# Eco-Evolutionary Drivers of Body Size Variation in Arthropods, With a Focus on Spiders

Camille Ameline, Denis Lafage, Mickaël Hedde, Philippe Vernon, Julien Pétillon

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## To cite this version:

Camille Ameline, Denis Lafage, Mickaël Hedde, Philippe Vernon, Julien Pétillon. Eco-Evolutionary Drivers of Body Size Variation in Arthropods, With a Focus on Spiders. Journal of Biogeography, 2026, 53 (2), pp.e70158. 10.1111/jbi.70158. hal-05500183

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Submitted on 9 Feb 2026

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1 Eco-evolutionary drivers of body size variation in arthropods, with a focus

2 on spiders

3

4 Running title: Arthropods body size variation along macroecological gradients

5

6 Camille Ameline1*, Denis Lafage1, Mickaël Hedde2, Philippe Vernon1 & Julien Pétillon1,3

7

8 1Université de Rennes, UMR CNRS 6553 Ecobio, 35042 Rennes Cedex, France

9 2INRAE, UMR 1222 Eco & Sols, 34070 Montpellier Cedex, France

10 3Institute for Coastal and Marine Research, Nelson Mandela University, Port Elizabeth 6031,

11 South Africa

12 *Corresponding author: cameline8@gmail.com

13

14 ORCID ID: Camille Ameline: 0000-0001-6892-2819, Denis Lafage: 0000-0002-6205-611X,

15 Mickaël Hedde: 0000-0002-6733-3622, Philippe Vernon: 0000-0002-6237-7511, Julien Pétillon:

16 0000-0002-7611-5133.

17

18 Acknowledgments

19 JP was supported by "BOOST ERC" OPALE and by the SAD "PEPPS" (both by the Région

20 Bretagne). No permits were required. We thank very much the two reviewers for their

21 constructive and detailed comments, as they helped focus and structure our manuscript.

22

23 Supplementary Data

24 Dataset and R script used for body size reviewing analysis are available in the Figshare

25 repository at https://doi.org/10.6084/m9 figshare.27118986.v3

26

27 Authors contribution

28 Camille Ameline: conceptualization (equal); data curation (lead); formal analysis (lead);

29 methodology (equal); visualization (lead); writing – original draft preparation (lead); writing –

30 review and editing (lead). Denis Lafage: writing – review and editing (supporting). Mickaël

31 Hedde: writing – review and editing (supporting). Philippe Vernon: conceptualization (equal);

32 methodology (equal); supervision (supporting); writing – original draft preparation

33 (supporting); writing – review & editing (supporting). Julien Pétillon: conceptualization

34 (equal); funding acquisition (lead); methodology (equal); project administration (lead);

35 supervision (lead); writing – original draft preparation (supporting); writing – review & editing

36 (supporting).
37 Abstract

38 **Aim:** Body size has been used thoroughly in arthropod ecology as a reliable trait to assess fitness
39 responses to changes in environmental factors. We aim to assess general patterns of intra-
40 specific body size variation along macroecological gradients in arthropods. We more specifically
41 discuss these patterns in spiders, as they represent a large and diverse group, colonizing most
42 terrestrial habitats.

43 **Location:** Global

44 Time Period: 1982-2024

45 Major Taxa Studied: Arthropods

46 **Methods:** We propose a systematic review and a meta-analysis of 146 studies on intraspecific
47 body size variation in arthropods over two main macroecological spatial gradients—latitude and
48 elevation—both of high interest in a global warming context.

49 **Results:** We found that more species with direct than with indirect development present a
50 converse Bergmann cline along both gradients.

51 **Main Conclusions:** We propose that life history traits such as voltinism, mobility, and brood
52 care influence intraspecific body size patterns—potentially hiding large-scale patterns

53 This review gathers empirical data about body size variation along elevational and latitudinal
54 gradients in arthropods, providing a step forward to better understanding of underlying
55 mechanisms driving body size variation.

56 **Keywords**

57 Araneae, Bergmann's rule, climate change, functional trait, macroecology, microecology,
58 Rensch's rule

59
60 Introduction

61 Ectotherms account for approximately 99% of all animal species on Earth, and they represent
62 the vast majority of the living biomass (Atkinson & Sibly, 1997; Rosenberg et al., 2023). This
63 diversity and preponderance has to be studied to understand organisms' ecological and
64 evolutionary responses to environmental changes, such as climate change (Ohlberger, 2013).

65 Among ectotherms, arthropods are known for their phenotypic plasticity in life history traits,
66 when habitats vary (Bonte & Lens, 2007; Fox & Czesak, 2000). As such, they present an ideal
67 taxon to investigate organisms' responses to environmental changes, which indeed shape
68 morphological and life-history traits expressed in a population (Kingsolver & Pfennig, 2007;
69 Nussey et al., 2007). The phenotypic plasticity of arthropods has been demonstrated through
70 variations in life-history traits such as dispersal behavior (Bonte et al., 2008; Bonte & Lens,
71 2007), amount and timing of reproduction events, and clutch size (Fox & Czesak, 2000). For
72 example, female spiders have been shown to maximize their fitness by allowing less energy to
73 reproduction whilst producing larger eggs (Hendrickx, Maelfait, & Lens, 2003; Pétillon et al.,
74 2009).

75 Body size varies by three orders of magnitude in arthropods: from the 139 µm long male
76 mymarid egg-parasitic wasp *Dicopomorpha echmepterygis* (Mockford 1997, Mymaridae) to
77 the 35.7 cm long stick insect *Phobaeticus chani* (Hennemann & Conle, 2008). Body size variation
78 has been broadly used to measure the organism responses to environmental variations. It is a
79 relatively easy trait to measure interspecifically and intraspecifically in arthropods because of
80 their exoskeleton, the large number of individuals and species, and their easy collection and
81 preservation. The study of body size, sometimes coupled with geometric morphometrics, gives
82 us information about body condition (Jakob et al., 1996), fecundity (Berger et al., 2012), fitness
83 (Brown et al., 2003), dispersion ability (Coyle et al., 1985) and eating habits (Evans & Forsythe,
84 1985; Gavín-Centol et al., 2017). In the present review we focus on structural body size, as
85 opposed to condition-dependent body size (Box 1). The mean structural body size of individuals
86 from a population is the result of evolutionary and ecological constraints (Gaston & Blackburn,
2000), while condition-dependent body size is influenced by the environment of an individual during its whole life. Structural body size (henceforth body size) is a labile trait, i.e. a trait that can vary over the course of an organism's ontogeny, until the organism finishes its exoskeleton growth (Nussey et al., 2007). Before structural body size is set (i.e. before the last ecdysis takes place), it is influenced by physiological traits (growth rate, resource availability, duration of important periods during juvenile growth), themselves influenced by environmental factors (Chown & Gaston, 2010) and phylogeny (Foerster, 2025; Rainford et al., 2016).

Body size variations will be different whether we consider intraspecific or interspecific patterns, generalist or specialist species, and large or small species. Considering these differences in body size variations, species will be constrained differentially by distinct ecological factors. It has been shown for example that small ectotherms acclimate to ambient temperature almost instantly (Stevenson, 1985). In arthropods, a larger body size can be an asset because it means greater fecundity in females, access to mates for males and resource sequestration advantages (Chown & Gaston, 2010; Huang et al., 2017). The benefits of small size may include reduced viability costs of growth and development, enhanced agility and reduced detectability, lowered maintenance energy costs, reduced heat stress, reduced costs of reproduction, and increased scramble competitive ability (Blanckenhorn, 2000; Chown & Gaston, 2010; Huang et al., 2018; Moya-Laraño et al., 2002, 2007). Intraspecific variation of body size and other morphologic traits may ultimately lead to parapatric speciation (Mammola et al., 2018).

The most studied environmental factors in "trait-based ecology of terrestrial arthropods" (Wong et al., 2019) are macroecological factors—namely latitude and elevation—and their associated biotic and abiotic environmental variables, e.g. temperature or season length, often in the context of climate change (Høye & Forchhammer, 2008; Radchuk et al., 2013). A latitudinal gradient will trigger gradients of abiotic factors such as temperature and growing season length (Conover & Present, 1990) while an elevational gradient will trigger gradients of temperature lapse rate, short-wave radiation input, partial pressure of respiratory gases, precipitation (and thus humidity), turbulence and wind speed (Hodkinson, 2005). Biotic factors that vary along these gradients are life history traits such as density, sex ratio (Lee et al., 2012), fecundity
(Bowden et al., 2013), dispersal ability, prey availability and sociality (Guevara & Avilés, 2007), wing size, color, absorbance and spectral reflectance, body size, thermal tolerance, diapause and fecundity (Hodkinson, 2005). Elevational and latitudinal gradients also trigger biotic differences in population density or community composition, themselves having an impact on interactions between organisms and resource acquisition. For example, a higher population density can lead to higher intraspecific competition, leading to a longer development period and a decreased body mass (Begon et al., 1986). Longitudinal gradients are understudied in insects, although they correlate to climatic variables (Jego et al., 2023). Species Abundance and Distribution (SAD) is commonly studied along with body size (Gaston, 2003; Gutiérrez & Menéndez, 1997; King, 2010; Ulrich, 2008) and sometimes along with macroecological factors (Bowden et al., 2013; Ciplak et al., 2008). For example, larger repartition area have been shown to positively correlate to body size, showing a direct implication of the study of body size in conservation (Gaston & Blackburn, 1996).

Several theories have been proposed to explain the patterns of body size variation along macroecological gradients. The main theory was Bergmann's rule which proposes that body size increases with latitude (Atkinson and Sibly 1997), while converse Bergmann's rule states that body size should decrease with latitude (Sheridan & Bickford, 2011). We present the most studied theories and hypotheses about the role of temperature in Boxes 2 and 3.

Along latitudinal gradients, there is a variety of body size responses in arthropods. A review on 47 species, (Blanckenhorn & Demont, 2004) found that, intraspecifically, around 20% of species did not show any pattern, while among the rest, about half followed Bergmann's rule, and the other half followed the converse rule. In insects, (Shelomi, 2012) found that on a total of 779 intra- and interspecific studies, 30% of the groups followed Bergmann's rule while another 30% followed the converse rule and 40% did not follow any trend. If we take some examples, several species of Diptera follow Bergmann's rule, while for a lot of Coleoptera, Orthoptera and Lepidoptera (Blanckenhorn & Demont, 2004), some spiders (Entling et al., 2010) or univoltine insects (Mousseau, 1997), the converse rule has been demonstrated.
142 Elevational gradients have been used as a proxy for latitudinal gradients and climatic changes.

143 Along elevational gradients, body size shows a variety of responses in arthropods, similar to
144 what is observed along latitudinal gradients. Some species show a positive correlation between
145 body size and elevation (Bergmann's rule) while some others show a negative one (converse
146 Bergmann's rule) (Hodkinson, 2005).

147 In contrast with arthropods in general, and notably insects, body size variation in spiders is
148 much less known, although they are used in many ecological and evolutionary studies because of
149 their high global and local diversity (see Dimitrov and Hormiga 2021 for a recent review). Like
150 other arthropods, spiders show a very wide size range: the smallest one is thought to be *Patu
digua* (Forster and Platnick 1977) from the Symphytognathidae family, with a body length of
151 0.37 mm, whilst the largest ones occur among tarantulas (Theraphosidae) and can have body
152 lengths up to 90 mm and leg spans up to 250 mm (Mammola et al., 2017). Gigantism can also be
153 observed on islands in spider taxa such as the *Orsonwelles* genus (Hormiga, 2002). As generalist
154 predators, spiders can be used for pest control (Toft, 2005). They are good bioindicators (Marc
155 et al., 1999; Rainio & Niemelä, 2003) and represent a diverse and abundant group within the
156 arthropods in various habitats (Lafage & Pétillon, 2014; Wise, 2006). Species with direct
157 development such as Orthopterans (hemimetabolous insects), and the majority of spiders, have
158 their body size controlled by feeding while ecdysis still takes place; unlike holometabolous
159 insects (with indirect development) such as ground beetles whose imaginal body size is
160 governed only by larval stages (complete metamorphosis). Spider body size and shape have
161 been shown to vary across behavioral guilds (Wolff et al., 2022). Hypotheses on resource
162 allocation and growth have been proposed, e.g. that some orb weavers, due to their efficient
163 webs, can capture more and larger prey and hence invest more into growth and fecundity
164 (Blackledge et al., 2009). Along macroecological gradients, we hypothesize that wanderers and
165 web-building species might present different patterns of body size variation.

167 In spiders, males are typically smaller than females and some families present one of the
168 greatest sexual size dimorphisms (SSD) in animals (Kuntner & Coddington, 2020). Only in rare
169 cases is the male larger than the female (Aisenberg et al., 2007). Across the animal kingdom, SSD
tends to increase with mean body size when the male is the larger sex; while the opposite tends to arise when the female is the larger sex. This is known as the Rensch's rule (Bidau & Martí, 2008; Rensch, 1950) and has been studied inter- and intraspecifically, along elevational and latitudinal gradients (Blanckenhorn et al., 2006; Bowden et al., 2013; Høye & Hammel, 2010; Laiolo et al., 2013). The size difference between sexes is expected to vary across macroecological gradients, as size itself varies with climatic conditions. Depending on the species presenting SSD, either male or female body size varied more often along macroecological gradients (Blanckenhorn et al., 2006; Bowden et al., 2013; Laiolo et al., 2013).

In this work, we review field studies on intraspecific variation of structural body size along macroecological gradients in spiders and other arthropods. We address the following three questions: (1) How does body size in arthropods vary along with macroecological factors? (2) Is this variation different among taxa with distinct development (direct vs. indirect)? (3) How do biotic (including life history traits) and abiotic factors interact with body size, to possibly explain larger spatial scale patterns? We further discuss the implications of monitoring body size in a changing world.

185

## 186 Methods

We chose the scope of this review as described in Table 1.

We searched for reviews and articles using the search engine 'Google Scholar' until September 2024 with the following key words: 'body size' + 'macroecological' / 'altitude' / 'latitude' / 'elevation' + 'ectotherm' / 'Arthropod' / 'insect' / 'spider' / 'Hexapoda' / 'Chelicerata' / 'Arachnid' / 'Araneae' / 'Myriapoda' / 'Crustacea'. This resulted in 40 combinations of searches. We found a total of 146 studies reporting intraspecific body size variation of 240 arthropod species along latitudinal and elevational gradients. See the PRISMA flow diagram for exclusion criteria (Figure S1) (O'Dea et al., 2021). We compared the proportions of body size responses along macroecological gradients between groups using a two-proportions Z-test. We also report a non-
196 exhaustive list of studies reporting intraspecific SSD variation along macroecological gradients

197 that we found with this search.

198 Specifically for spiders, we report studies that we found on other microecological patterns

199 (urbanization and habitat quality) as a non-exhaustive list.

200

201 Definitions and concepts

202 Box 1. Body size

203 It is important to differentiate structural body size (SBS, usually called body size indicator (BSI)

204 in vertebrates) from condition-dependent body size (CDBS). Structural body size was defined by

205 (Moya-Laraño, Macías-Ordóñez, et al., 2008) as a 'measure of body size that does not change with

206 additional nutrient acquisition once an animal has discontinued growth, and thus SBS is not

207 directly affected by current condition', while CDBS is 'any measure of body size that changes with

208 current condition (i.e. covaries with nutrient storage)'. Body condition (i.e. body mass corrected

209 for size differences) is a proxy of fitness and reflects nutrient storage and habitat quality (Jakob

210 et al., 1996; Knapp & Knappová, 2013; Labocha et al., 2014; Moya-Laraño, Macías-Ordóñez, et al.,

211 2008; Peig & Green, 2009). Structural body size, on the other hand, is not affected by condition

212 and will thus reflect evolutionary and ecological constraints. In arthropods, the confusion is

213 sometimes made between CDBS and SBS when body condition traits are measured and

214 considered as 'body size' such as mass, density, or abdomen size (Chown & Gaston, 2010).

215 Structural body size can be measured in multiple ways within and across taxa, considering

216 distinct ways to store energy. For example, the whole body of a ground beetle is covered with

217 chitin, which prevents it from storing much energy while a spider's abdomen can grow larger to

218 store energy. It will then be more adapted to measure a sclerotized body part such as the head

219 or the pronotum to measure SBS. Measures of structural body size in spiders include:

220 cephalothorax (carapace) length (Petersen, 1950) and width (Bowden et al., 2013; Høye &

221 Hammel, 2010) illustrated in Figure 1A: *Pardosa furcifera*, from Ameline *et al.* (2017), first femur

222 length (Opell et al., 2007) (illustrated in Figure 1B), and tibia-patella length (Skow & Jakob,
2003). There needs to be a consensus on which body size measures to use in order to allow comparison (Gallagher et al., 2020). Indeed, interspecific meta-analyses using average figures from taxonomic literature (Entling et al., 2010; Fattorini et al., 2013, 2014; Ulrich, 2007; Ulrich & Fiera, 2010) can only do so if the same measures are used. Similarly, intraspecific studies should be comparable among one another. In most recent studies, several measures of sclerotized body parts are correlated (Ameline et al., 2018; Knapp & Knappová, 2013; Lowe et al., 2020; Puzin et al., 2014). In the present study, we are interested in evolutionary and ecological constraints, thus focusing on structural body size, henceforth body size throughout this article.

Box 2. Rules of body size variation along macroecological gradients.

Body size has been used interspecifically in allometric studies to try and understand general biological laws (Norris, 1998; Raerinne, 2013). At the interspecific level, the *Metabolic Theory of Ecology* proposes that (i) there are more species at low latitudes than at high latitudes, (ii) there are more small species, (iii) so there are consequently more small species at low latitudes and they show greater diversity (Brown et al., 2004). The most famous body size variation theory is *Bergmann's rule* which proposes that body size increases with latitude (Atkinson & Sibly, 1997; Bergmann, 1848). This rule states that a larger organism provides a reduced surface per volume ratio which minimizes the heat loss (Blackburn et al., 1999). The rule was originally thought to apply interspecifically to endotherms, but an intraspecific version has been proposed as *James' rule* or *neo-Bergmann's rule* (Chown & Gaston, 2010; Vinarski, 2014), and it has been tested in all taxa (Blanckenhorn & Demont, 2004; Chown & Gaston, 2010; Entling et al., 2010; Meiri, 2011; Shelomi, 2012). As the opposite pattern has been observed in arthropods (Sheridan & Bickford, 2011) and spiders (Puzin et al., 2014), a *converse Bergmann's rule* has then been proposed which postulates that decreasing season length causes smaller body size at higher latitude (Blanckenhorn & Demont, 2004). This rule supposes that shorter seasons at higher latitudes reduce the foraging period, hence resulting in reduced growth and development period. A gradient of decreasing body size towards the poles should then be observed (Blanckenhorn & Demont, 2004). While this hypothesis supposes that individuals complete their life cycle within
one year, spider species who complete theirs in several years and live at high elevations (Ameline et al., 2018; Høye & Forchhammer, 2008; Milano et al., 2023; Pickavance, 2001) might adapt to grow a larger body size. The *countergradient variation* announces that growth rate increases with latitude, because the growing season is shorter, resulting in a homogenous distribution of body size along latitudinal gradients (Conover & Present, 1990). Different intraspecific patterns of body size variation across macroecological gradients are usually reported, including linear and non-linear clines. Linear clines can be *positive* (Bergmann's rule) or *negative* (converse Bergmann's rule) showing increase or decrease of body size across the range, respectively. Non-linear clines include *sawtooth* and *stepwise* clines, which can still show an overall positive or negative cline, *U-shaped* or *hump-shaped* clines, which occur when an increase or decrease is reversed gradually over a single point in the entire range, while *curvilinear* clines occur when increase or decrease is reversed gradually over several points across the range (Shelomi, 2012).

*Rapoport's rule* says that the size of a species distribution range increases with latitude, but it is used interspecifically (Gaston & Blackburn, 1996). *Cope's rule* supposes a macroevolutionary trend towards increased size (Kingsolver & Pfennig, 2004). The *seasonality hypothesis* states that climates characterized by long annual cycles select for large body sizes. This hypothesis was confirmed by (Troost et al., 2009) who proposed that both longer productivity and seasonality may lead to larger body sizes. Although many hypotheses were proposed, the mechanisms underlying these body size patterns are still rarely investigated (Blanckenhorn & Demont, 2004).

Box 3. Body size variation linked to temperature variation.

Rules laid down are often thought to be linked to temperature. However, it is still a controversial subject and there is no clear explanation on why body size increases or decreases when the organism is exposed to low temperatures (Atkinson & Sibly, 1997). Indeed, 83% of 109 studies on ectotherms showed an increased growth rate and consequently, an increased body size at lower rearing temperatures, although individual growth rates were expected to decrease at
279 lower temperatures. This phenomenon is explained by the 'developmental temperature-size rule'
280 or TSR (Atkinson, 1994; Atkinson & Sibly, 1997). The organism can 'choose' to trade-off for a
281 delayed maturity which would lead to a larger body size if the increase of fecundity exceeds the
282 loss of fitness caused by delayed maturity. Another hypothesis is that higher temperatures may
283 cause limited resource availability. In response to that limitation, body size is smaller due to the
284 lack of resource acquisition or due to an adaptive response to reduce size at maturity. From a
285 cellular point of view, the TSR argues that cellular differentiation which leads to sexual maturity
286 is limited by diffusion at low temperatures, thus maturity would be delayed. Consequently, cell
287 size would become larger at lower temperatures (Arendt, 2007). Bergmann's rule has been
288 attributed to the TSR theory (temperature variation) while converse Bergmann's rule was
289 attributed to a resource limitation, due to season length variation (Hodkinson, 2005). This has
290 been shown, for example, by an experiment along a thousand meters elevational gradient on
291 weevils in subantarctic islands by (Chown & Klok, 2003).

292 Kingsolver and Huey (2008) summarized the rules linked to temperature as three rules. The first
293 one is "bigger is better" (red in Figure 2, adapted from Kingsolver & Huey (2008)). A larger body
294 size is thought to bring a higher fitness via better performance and dominance. But a larger body
295 size can also be costly and risky because of delayed maturation and increased energy demand.
296 Hence, intermediate sizes are also thought to be optimal. As a counter-example of this first rule,
297 (Moya-Laraño et al., 2007) showed that smaller males are better scramble competitors. Smaller
298 is also generally better in the case of parasites and parasitoids (Blanckenhorn, 2000). The
299 second rule is "hotter is smaller" (green in Figure 2). It corresponds to the TSR, which takes into
300 account the effect of temperature on the organism during development. Counter-examples exist,
301 e.g. in the case of Orthoptera and Lepidoptera, hotter is bigger (Mousseau, 1997; Walters &
302 Hassall, 2006). 'Ectotherms that obey the temperature size rule are identified as having a higher
303 temperature threshold for development rate than for growth rate; exceptions are identified as
304 having a lower temperature threshold for development rate than for growth rate' (Walters &
305 Hassall, 2006). The third rule, "hotter is better" (blue in Figure 2), proposes that organisms with
306 a high optimal temperature will also have high maximal performance and fitness, according to
thermodynamics laws. We chose not to present body size variations in response to temperature because most of the studies consider growth rate and growth efficiency but not directly body size (Angilletta and Dunham 2003).

310

## 311 Results

We found a total of 146 studies reporting intraspecific body size variation of 240 arthropod species along latitudinal and elevational gradients (Figure 3, Supplementary Table S1). We did not find an overall tendency towards positive (Bergmann's rule) or negative (converse Bergmann's rule) variation of body size across elevation or latitude. We found that species with direct development (non holometabolous) presented a larger proportion of negative clines than species with indirect development, both along elevational (Z-test, X-squared = 4.1, df = 1, p-value = 0.02, 42% vs. 23%, Figure 3) and latitudinal clines (Z-test, X-squared = 8.2, df = 1, p-value = 0.002, 74% vs. 40%, Figure 3). In spiders, we found that 11 out of 18 species showed no body size trend along elevational gradients (61%, Figure 2, Table 2). This proportion was higher than in other arthropod species (Z-test, X-squared = 8.2, df = 2, p-value = 0.02, 61% vs. 22% and 33% in species with direct and indirect development, respectively). We present here a non-exhaustive list of SSD variation along macroecological gradients in Arthropods (Table 3).

324

325

## 326 Discussion

(1) Intraspecific body size and sexual size dimorphism (SSD) variation along macroecological gradients

We did not find an overall tendency towards positive (Bergmann's rule) or negative (converse Bergmann's rule) variation of body size across elevation or latitude. We found that species with direct development presented a larger proportion of negative clines than species with indirect development, both along elevational and latitudinal clines (Figure 3). This result suggests that the growth of species with direct development might be restricted by the environmental

333
changes caused by increasing latitude or elevation—notably the shorter season length. Because species with indirect development go through metamorphosis between the larval and the adult stages, they may dispose of more possibilities to increase their growing season. In spiders, we found that 11 out of 18 species showed no body size trend along elevational gradients (61%, Figure 3, Table 2). This proportion was higher than in other arthropod species (61% vs. 22% and 33% in species with direct and indirect development, respectively). This result may be caused by the high dispersal of spiders which would hide existing body size variations along elevational gradients. It is important to note that most studies have been performed on a limited number of populations and have not been repeated, which may result in a low statistical power to detect overall patterns (Gienger et al., 2019).

Sexual Size Dimorphism (SSD) has been shown to vary across macroecological gradients in arthropods interspecifically (Blanckenhorn et al., 2006; Laiolo et al., 2013) and intraspecifically, e.g. in beetles (Baranovská et al., 2019) and spiders (Bowden et al., 2013; Høye et al., 2009; Høye & Hammel, 2010; Laiolo et al., 2013). A meta-analysis on intraspecific SSD variation across macroecological gradients in arthropods revealed that, on average, male body size varied more than female (Horne et al., 2019; Kojima, 2019). In spider species this was found to be the opposite, as female body size varied more across elevation gradients (Horne et al., 2019). This study suggests that intraspecific SSD variation is constrained by evolutionary forces rather than environmental ones (Horne et al., 2019). They also found no relationship between SSD variation and varied tested factors like environment type (aquatic or terrestrial), voltinism, mean body size, degree of SSD and gradient direction. Conversely, it was found in grasshoppers that female body size varied more across an elevational gradient and the authors hypothesized that female body size might be more plastic or evolve faster in harsh environments (Laiolo et al., 2013). We present here a non-exhaustive list of intraspecific SSD variation along macroecological gradients in Arthropods (Table 3).

In contrast with sexual *size* dimorphism, sexual *shape* dimorphism is studied in other arthropods such as the millipede *Brachydesmus troglobius* (Vujić et al., 2020) and might be relevant in
further, spider-focused, studies. Shape dimorphism, similarly to size dimorphism, might be affected by factors affecting body size along macroecological gradients.

In the context of anthropic impacts, macroecological gradients have been studied in spiders, such as urbanization and land use. It was shown for one species of orb-weaver spider (Araneidae) that body size increased in an urbanized habitat (Lowe et al., 2014), while another species was shown to decrease body size in highly urbanized habitats (Dahirel et al., 2019).

Interspecifically, urbanization and fragmentation have been shown to cause body size decrease (Merckx et al., 2018; Piano et al., 2020). High habitat quality, determined by more rocks, precipitation and duration of snow coverage, was shown to intraspecifically increase body size and eggcase size (Mammola et al., 2019). Corroborating this result, (Bowden et al., 2018) observed a decline in spider abundance correlated to snowmelt timing and moisture availability.

In an agricultural context, (Plath et al., 2021) revealed that mean body size of spider community decreased with intensive agriculture. On the other hand, (Pinto et al., 2021) observed no difference in body size in spider communities across different land uses, and hypothesized that microhabitat rather than global land use influenced the observed interspecific body size pattern.

In the following, we pinpoint several factors that could explain variability of intraspecific body size responses along macroecological gradients among taxa and even species, focusing on spiders.

(2) Biotic and abiotic factors driving local changes in body size and SSD

(a) Biotic factors

Diet quality has been correlated to body size variation across latitudinal gradients (Ho et al., 2010). Higher competition and variation in prey availability might also lead to fewer resources and explain a lack of overall body size variation along environmental gradients (Beckers et al., 2020).

Among life history traits, the degree of voltinism—i.e. how many reproduction events occur during the year—may influence body size (of both male and female) response to macroecological gradients. Shifts in voltinism across elevational or latitudinal gradients—due to
changing seasonality—might cause body size variation along these gradients (Beckers et al., 2020). (Cabon et al., 2024) showed that temperature had an effect on the body size of univoltine, but not bivoltine species. A sawtooth cline is typically interpreted as the result of a shift in voltinism (Shelomi, 2012). The level of voltinism is known to change interspecifically with latitude and hence temperature (Kivelä et al., 2011; Zeuss et al., 2017). Voltinism is less studied across populations and along elevational gradients, as these gradients are usually smaller than latitudinal ones. A shorter generation time in multivoltine species would provide a longer growing season for earlier clutches of offspring (Chown & Klok, 2003). A different degree of voltinism would then mean a different resource allocation strategy and the underlying mechanisms of body size variation would differ. In the present study, we could not consider voltinism *a priori*, as it may vary within species and populations.

Brood care is common in spiders and may provide them with a lower susceptibility to unfavorable conditions in comparison with insect species with stationary larval stages (Beckers et al., 2020). Body size might then be less influenced by environmental conditions during development and show no trend across an environmental gradient.

Mobility and dispersal are important factors that could influence the degree of body size variation across gradients. In (Cabon et al., 2024), only species with a low ballooning capacity showed body size variation across a temperature gradient. Species with low mobility may be split in subpopulations that would induce body size variation across gradients (Beckers et al., 2020). A higher mobility may thus cause a species to show variation induced by large-scale rather than fine-scale environmental factors (Hein et al., 2019). For example, body size variation has been linked to foraging ability in bees (Gathmann & Tscharntke, 2002). Here we want to emphasize the role of body size particularly in spider dispersion. Long-distance dispersal in spiders will be passive via ballooning and favored by a small body size or mass while short-distance dispersal will be active via walking on the ground and favored by a large size or amplitude. Ideal Free Distribution (IFD) is expected to homogenize body sizes among habitats (Fretwell & Lucas, 1970; Hendrickx, Maelfait, Speelmans, et al., 2003; Yip et al., 2008), while disturbances may select for increased dispersal propensities: smaller body size in ballooning
species or individuals, mostly web-building spiders (Blandenier, 2009; Blandenier et al., 2013;

Coyle et al., 1985; Simonneau et al., 2016) or longer legs in runners, i.e. ground-dwelling spiders

(Lafage et al., 2015). Selection for relatively longer legs was previously reported in web-building

(mate search: Foellmer and Fairbairn (2005)), free-running (mate search: Framenau (2005))

and cave-living species (cave adaptation: Miller (2005)). Longer legs have also been proved to
increase speed in steep ground (Prenter et al., 2012)), and in suspensory locomotion (Moya-
Laraño, Vinković, et al., 2008)).

Although we do not present an exhaustive list of such results, traits linked to body size have
been shown to vary across macroecological gradients: sexual size dimorphism (SSD), growth
rate—related to temperature (Angilletta, Jr., & Dunham, 2003), or fecundity (Berger et al., 2012;
Bowden et al., 2013; Marshall et al., 2013; Reed & Nicholas, 2008).

Body size in spider offspring is typically measured to reveal reproduction trade-offs (Ameline et al., 2017; Brown et al., 2003; Petersen, 1950; Pétillon et al., 2009; Skow & Jakob, 2003; Walker et al., 2003), and these reproductive trade-offs have been revealed along macroecological gradients (elevation: Ameline et al. 2018).

(b) Abiotic factors

Habitat has been shown to be an important factor in spider communities distribution (Entling et

al., 2007; Koponen, 2002). At a local spatial scale (m²), habitats can shape body size patterns

(Brown et al. 2003, Hendrickx et al. 2003a, Pétillon et al. 2009, Puzin et al. 2011). After finding

no overall body size patterns along elevational gradients, studies suggested that microhabitats

played a more important role than the large-scale landscape (Ameline et al., 2017; Hein et al.,

2015). Local environmental conditions such as soil pH, occurrence of ice and abundance have

been shown to play a role in species body size distribution (Ornaghi et al., 2023). In spiders,

snow cover and habitat type are considered to play a role in body size distribution across

macrogeographic scales (Bowden et al., 2015; Hein et al., 2014). (Bowden et al., 2015)

emphasize that environmental conditions are especially important for small size species with

low dispersal ability. Further, models showed that body size was linked to how ectotherms move

in microclimatic environments (Woods et al., 2015).
Climate has been shown to drive body size patterns in arthropods along macroecological gradients (Hu et al., 2012). Alternatively, little effect of climate change on body size has been observed in herbivorous beetles (Baar et al., 2018). The effect of temperature on body size or related traits is often studied in insects (Ciplak et al., 2008; Opell et al., 2007) and has also been studied along latitudinal and elevational gradients (Koyama et al., 2015; Pérez-Valencia & Moya-Raygoza, 2015). In insects, further analysis of the effect of temperature on physiology (growth rate, metabolic rate) has been performed along elevational gradients (Bulgarella et al., 2015; Cogo et al., 2020). Dispersal ability, mentioned above, has also been shown to be influenced by temperature in spiders (Bonte et al., 2008). In various arthropods, temperature and season length has been found to influence body size—e.g. in crustaceans (Jaramillo et al., 2017) and beetles (Collard et al., 2021). Overall patterns of reduced body size were observed with warming temperatures, likely linked to oxygen lack in aquatic environments (Verberk et al., 2021) and heat tolerance in endotherms (Peralta-Maraver & Rezende, 2021).

Other climatic factors such as photoperiod (Hassall, 2013) have been correlated to body size variation along macroecological gradients. We further develop the broader impact of climatic changes on body size variation in the last section of the results.

### (3) Perspectives and future research directions in a changing world

The intraspecific study of body size through space and time is key in Ecology, as it is driven by physiological and adaptive mechanisms, and addresses conservation and invasion issues (Austin & Dunlap, 2019; Bertelsmeier, 2017; Thomas, 2010; Violle et al., 2007; Wills et al., 2014).

Notably, the French agriculture research institute (INRAE) has been collecting soil arthropods along latitudinal gradients across varied habitats in 70 stations every year (Pouzenc et al., 2026), along 25 elevational gradients across France, and across over ten years in agronomic stations (ongoing studies). However, most studies solely report correlations of phenotypic variation with macroecological gradients. We found many studies investigating body size variation along macroecological gradients, but we still know little about the causes and consequences of
472 variation in life history trait plasticity in the wild, or how natural selection operates on plasticity
473 (Pigliucci, 2005; Stillwell, 2010). A few studies combined body size measurements with
474 common-garden experiments or genetic data on arthropods collected on macroecological
475 gradients (Bulgarella et al., 2015; Sandoval-Arango et al., 2020; Yadav et al., 2021), but more of
476 these studies are needed to address the mechanisms underlying body size variation along
477 macroecological gradients.

478 Latitude and elevation are macroecological factors that are good correlates of temperature
479 variations in a global change context. There is a need to predict how species and populations will
480 adapt to macroecological variations, since global change brings fast and important
481 modifications. Anthropic activity threatens biodiversity and thus stability of ecosystems and
482 biogeological cycles, causing an increase of severe weather events. It has been shown for birds
483 that severe weather events can exert directional selection pressure, favoring larger size
484 (Goodman et al., 2012). Global warming is thought to generally result in an intraspecific
485 decrease in body size, but the underlying mechanisms are not well known and very few studies
486 have focused on endotherms (Sheridan & Bickford, 2011). Body size and SSD can also vary with
487 anthropogenic disturbance (Sukhodolskaya & Eremeeva, 2013). Intraspecifically, climate change
488 may result in increased SSD at higher elevations due to expanding growing seasons (Høye &
489 Hammel, 2010).

490 Thermal tolerance may be studied along with body size variation (Hoffmann et al., 2013),
491 although we assume that it may play a less important role than habitat niches in ectotherms.
492 Sudden environmental changes can lead to niche shifts, thus leading to invasions depending on
493 dispersion ability and range size (Iversen et al., 2013). Climate indeed acts as a major constraint
494 on range boundaries (Thomas, 2010). This is a major social issue as invasive species may also be
495 vectors of disease, such as mosquitoes with malaria. Invasions can also inverse the clines
496 brought by climate change (Treasure & Chown, 2014). A good example of habitat that is
497 particularly prone to global warming is the arctic habitat; where arthropods rely on snowmelt to
498 emerge. Hence, the predicted variability of snowmelt may affect organisms in areas of late
snowmelt most severely (Bowden et al., 2018; Hein et al., 2014; Wehner et al., 2023). Moreover, specialized species that present a narrow phenological range or host specialization like butterflies or parasitoid wasps will possibly be more vulnerable to trophic mismatch (Høye & Forchhammer, 2008). As a contrasting example, body size can remain stable over decades (one arctic lycosid population: Høye et al. (2009)). Global change may have a bigger impact on tropical insects because they are living close to their optimal temperature and they are relatively sensitive to temperature change (Deutsch et al., 2008). We also know that plasticity increases in an unpredictable environment (Fischer et al., 2011) and this raises again the issue of anthropic disturbance in stable environments.

Because of the variety of morphologies in arthropods, studies use diverse measures of body size and often did not compare or repeat their results within the same taxa. The results we present thus offer a rough overview of body size variation in arthropods. Multivariate analyses of body size provide a better approximation of a population's body size (Bidau & Martí, 2007; Caldas et al., 1996; Knapp & Knappová, 2013). Ratios (Azevedo et al., 1998), allometry (Bidau & Martí, 2007) or Geometric Morphometrics (GM) (Hernández et al., 2011) can further take shape into account. These methods require however a large sampling and analyzing effort, difficult to implement in large-scaled analyses. For future meta-analyses to be richer and more precise, open-source databases (Gallagher et al., 2020) and standardized traits measurements in arthropods (Moretti et al., 2017) and spiders (Lowe et al., 2020; Pekár et al., 2021)—including habitat and life-history traits—are essential. We plead for integrating more life history traits in monitoring and predicting research, which is increasingly easy due to the development of worldwide databases and mechanistic species distribution models, respectively.

Conclusions

(1) We found that converse Bergmann clines prevail along elevational and latitudinal gradients in arthropod species with direct development (non holometabolous). In arthropods and in spiders specifically, we argue that life-history traits such as voltinism,
526 development, mobility and dispersal ability, guild—e.g. wanderer vs. web-building—are
527 explanatory variables that influence body size patterns along macroecological gradients.

528 (2) Multivariate assessment of body size is often lacking, although essential to grasp its
529 variation across macroecological gradients. As an example, separate measurement of
530 female and male body size can reveal sexual size dimorphism (SSD), an important trait to
531 consider in arthropods and in spiders specifically.

532 (3) Abiotic factors such as microclimate, habitat are also key factors influencing body size
533 variation, although they are not often reported.

534 (4) In addition, we emphasize the need for future studies to use standardized measurements
535 and to publish them in public databases to allow for comparable and more complete
536 analyses.

537 (5) Many rules have been set to fit body size trends, without however explaining the
538 underlying patterns that drive body size clines (Meiri, 2011). This review gathers
539 empirical data about body size variation along elevational and latitudinal gradients in
540 arthropods, providing a step forward to better understanding of underlying mechanisms
541 driving body size variation.

542 (6) The intraspecific study of body size through space and time is key in Ecology, as it is
543 driven by physiological and adaptive mechanisms, and addresses conservation and
544 invasion issues However, most studies solely report correlations of phenotypic variation
545 with macroecological gradients. We still know little about the causes and consequences
546 of variation in life history trait plasticity in the wild, or how natural selection operates on
547 plasticity. A few studies combined body size measurements with common-garden
548 experiments or genetic data on arthropods collected on macroecological gradients, but
549 more of these studies are needed to address the mechanisms underlying body size
550 variation along macroecological gradients.

551

552 Supplementary Material
553 **Figure S1** PRISMA flow diagram of literature meta-analysis

554 **Table S1** Body size variations in response to latitudinal and elevational gradients.

555

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1010 https://doi.org/10.1016/j.anbehav.2012.02.010
1011

1012 Puzin, C., Acou, A., Bonte, D., & Pétillon, J. (2011). Comparison of reproductive traits between two salt-marsh wolf spiders (Araneae, Lycosidae) under different habitat suitability conditions. *Animal Biology, 61*(2), 127-138. https://doi.org/10.1163/157075511X566461

1015 Puzin, C., Leroy, B., & Pétillon, J. (2014). Intra-and inter-specific variation in size and habitus of two sibling spider species (Araneae: Lycosidae): taxonomic and biogeographic insights from sampling across Europe. *Biological Journal of the Linnean Society, 113*(1), 85-96.

1018 Radchuk, V., Turlure, C., & Schtickzelle, N. (2013). Each life stage matters: The importance of assessing the response to climate change over the complete life cycle in butterflies. *Journal of Animal Ecology, 82*(1), 275-285. https://doi.org/10.1111/j.1365-2656.2012.02029.x

1022 Raerinne, J. P. (2013). Explanatory, predictive, and heuristic roles of allometries and scaling relationships. *BioScience, 63*(3), 191-198. https://doi.org/10.1525/bio.2013.63.3.7

1024 Rainford, J. L., Hofreiter, M., & Mayhew, P. J. (2016). Phylogenetic analyses suggest that diversification and body size evolution are independent in insects. *BMC Evolutionary Biology, 16*(1), 8. https://doi.org/10.1186/s12862-015-0570-3

1027 Rainio, J., & Niemelä, J. (2003). Ground beetles (Coleoptera: Carabidae) as bioindicators. *Biodiversity and Conservation, 12*(3), 487-506.

1029 Reed, D. H., & Nicholas, A. C. (2008). Spatial and temporal variation in a suite of life-history traits in two species of wolf spider. *Ecological Entomology, 33*(4), 488-496.
1030 https://doi.org/10.1111/j.1365-2311.2008.00994.x

1032 Rensch, B. (1950). Die Abhängigkeit der relativen Sexualdifferenz von der Körpergröße. *Bonner Zoologische Beiträge, 1*, 58-69.

1034 Rosenberg, Y., Bar-On, Y. M., Fromm, A., Ostikar, M., Shoshany, A., Giz, O., & Milo, R. (2023). The global biomass and number of terrestrial arthropods. *Science Advances, 9*(5), eabq4049. https://doi.org/10.1126/sciadv.abq4049

1037 Sandoval-Arango, S., Cárdenas Henao, H., & Montoya-Lerma, J. (2020). Divergence in Bergmann's clines: Elevational variation and heritability of body size in a leaf-cutting ant. *Insectes Sociaux, 67*(3), 355-366. https://doi.org/10.1007/s00040-020-00771-8
1040 Schäfer, M. (1976). Experimentelle Untersuchungen zum Jahreszyklus und zur Überwinterung von Spinnen (Anarenida). *Zoologische Jahrbücher, Abteilung Systematik, Ökologie Und Geographie Der Tiere*, 103, 127-289.

1043 Shelomi, M. (2012). Where are we now? Bergmann's rule sensu lato in insects. *The American Naturalist*, 180(4), 511-519. https://doi.org/10.1086/667595

1045 Sheridan, J. A., & Bickford, D. (2011). Shrinking body size as an ecological response to climate change. *Nature Climate Change*, 1(8), 401-406. https://doi.org/10.1038/nclimate1259

1047 Simonneau, M., Courtial, C., & Pétillon, J. (2016). Phenological and meteorological determinants of spider ballooning in an agricultural landscape. *Comptes Rendus Biologies*, 339(9-10), 408-416. https://doi.org/10.1016/j.crvi.2016.06.007

1050 Skow, C. D., & Jakob, E. M. (2003). Effects of maternal body size on clutch size and egg weight in a pholcid spider (*Holocnemus pluchei*). *Journal of Arachnology*, 31(2), 305-308. https://doi.org/10.1636/01-85

1053 Stevenson, R. D. (1985). Body size and limits to the daily range of body temperature in terrestrial ectotherms. *The American Naturalist*, 125(1), 102-117. https://doi.org/10.1086/284330

1055 Stillwell, R. C. (2010). Are latitudinal clines in body size adaptive? *Oikos*, 119(9), 1387-1390. https://doi.org/10.1111/j.1600-0706.2010.18670.x

1057 Sukhodolskaya, R. A., & Eremeeva, N. I. (2013). Body size and shape variation in ground beetle *Carabus aeruginosus* F.-W., 1822 (Coleoptera, Carabidae). *Contemporary Problems of Ecology*, 6(6), 609-615. https://doi.org/10.1134/S1995425513060127

1060 Tanaka, S. (2024). Geographic variation in body size of the migratory locust *Locusta migratoria* (Orthoptera, Acrididae): Masaki's cline and phase polyphenism. *Journal of Orthoptera Research*, 33(1), 27-40. https://doi.org/10.3897/jor.33.107242

1063 Thomas, C. D. (2010). Climate, climate change and range boundaries: Climate and range boundaries. *Diversity and Distributions*, 16(3), 488-495. https://doi.org/10.1111/j.1472-4642.2010.00642.x

1066 Toft, S. (2005). The quality of aphids as food for generalist predators: Implications for natural control of aphids. *European Journal of Entomology*, 102(3), 371.

1068 Treasure, A. M., & Chown, S. L. (2014). Antagonistic effects of biological invasion and temperature change on body size of island ectotherms. *Diversity and Distributions*, 20(2), 202-213. https://doi.org/10.1111/ddi.12153

1071 Troost, T. A., van Dam, J. A., Kooi, B. W., & Tuenter, E. (2009). Seasonality, climate cycles and body size evolution. *Mathematical Modelling of Natural Phenomena*, 4(6), 135-155. https://doi.org/10.1051/mmnp/20094605

1074 Ulrich, W. (2007). Body weight distributions of central European Coleoptera. *European Journal of Entomology*, 104(4), 769-776.

1076 Ulrich, W. (2008). Body size and the relative abundance of species. *Ecological Questions*, 10, 19-29. https://doi.org/10.2478/v10090-009-0003-2
1078 Ulrich, W., & Fiera, C. (2010). Environmental correlates of body size distributions of European springtails (Hexapoda: Collembola): Body size distributions of European springtails. *Global Ecology and Biogeography*, 19(6), 905-915. https://doi.org/10.1111/j.1466-8238.2010.00565.x

1082 Verberk, W. C. E. P., Atkinson, D., Hoefnagel, K. N., Hirst, A. G., Horne, C. R., & Siepel, H. (2021). Shrinking body sizes in response to warming: Explanations for the temperature-size rule with special emphasis on the role of oxygen. *Biological Reviews*, 96(1), 247-268. https://doi.org/10.1111/brv.12653

1086 Viel, N., Mielec, C., Pétillon, J., & Høye, T. T. (2022). Variation in abundance and life-history traits of two congeneric Arctic wolf spider species, *Pardosa hyperborea* and *Pardosa furcifera*, along local environmental gradients. *Polar Biology*, 45(5), 937-950. https://doi.org/10.1007/s00300-022-03041-4

1090 Vinarski, M. V. (2014). On the applicability of Bergmann's rule to ectotherms: The state of the art. *Biology Bulletin Reviews*, 4(3), 232-242. https://doi.org/10.1134/S2079086414030098

1093 Violle, C., Navas, M.-L., Vile, D., Kazakou, E., Fortunel, C., Hummel, I., & Garnier, E. (2007). Let the concept of trait be functional! *Oikos*, 116(5), 882-892. https://doi.org/10.1111/j.2007.0030-1299.15559.x

1096 Vujić, V., Lučić, L., Pavković-Lučić, S., Ilić, B., Jovanović, Z., Makarov, S., & Dudić, B. (2020). Sexual size and shape dimorphism in *Brachydesmus troglobius* Daday, 1889 (Diplopoda, Polydesmida). *ZooKeys*, 930, 75-88. https://doi.org/10.3897/zookeys.930.48285

1100 Walker, S. E., Rypstra, A. L., & Marshall, S. D. (2003). The relationship between offspring size and performance in the wolf spider *Hogna helluo* (Araneae: Lycosidae). *Evolutionary Ecology Research*, 5(1), 19-28.

1103 Walters, R. J., & Hassall, M. (2006). The Temperature-Size Rule in Ectotherms: May a General Explanation Exist after All? *The American Naturalist*, 167(4), 510-523. https://doi.org/10.1086/501029

1106 Wehner, A., Hein, N., Beckers, N., Dobbert, S., Pape, R., & Löffler, J. (2023). Early snow melt and diverging thermal constraints control body size in arctic-alpine spiders. *Biological Journal of the Linnean Society*, 138(1), 1-13. https://doi.org/10.1093/biolinnean/blac127

1109 Wills, B. D., Moreau, C. S., Wray, B. D., Hoffmann, B. D., & Suarez, A. V. (2014). Body size variation and caste ratios in geographically distinct populations of the invasive big-headed ant, *Pheidole megacephala* (Hymenoptera: Formicidae). *Biological Journal of the Linnean Society*, 113(2), 423-438. https://doi.org/10.1111/bij.12386

1113 Wise, D. H. (2006). Cannibalism, food limitation, intraspecific competition, and the regulation of spider populations. *Annual Review of Entomology*, 51(1), 441-465. https://doi.org/10.1146/annurev.ento.51.110104.150947

1116 Wolff, J. O., Wierucka, K., Paterno, G. B., Coddington, J. A., Hormiga, G., Kelly, M. B. J., Herberstein, M. E., & Ramírez, M. J. (2022). Stabilized morphological evolution of spiders despite mosaic changes in foraging ecology. *Systematic Biology*, 71(6), 1487-1503. https://doi.org/10.1093/sysbio/syac023
1120 Wolz, M., Klockmann, M., Schmitz, T., Pekár, S., Bonte, D., & Uhl, G. (2020). Dispersal and life-history traits in a spider with rapid range expansion. *Movement Ecology*, 8(1), 2.
1121 https://doi.org/10.1186/s40462-019-0182-4
1122

1123 Wong, M. K. L., Guénard, B., & Lewis, O. T. (2019). Trait-based ecology of terrestrial arthropods. *Biological Reviews*, 94(3), 999–1022. https://doi.org/10.1111/brv.12488

1125 Woods, H. A., Dillon, M. E., & Pincebourde, S. (2015). The roles of microclimatic diversity and of behavior in mediating the responses of ectotherms to climate change. *Journal of Thermal Biology*, 54, 86–97. https://doi.org/10.1016/j.jtherbio.2014.10.002

1128 Yadav, S., J. Stow, A., & Dudaniec, R. Y. (2021). Microgeographical adaptation corresponds to elevational distributions of congeneric montane grasshoppers. *Molecular Ecology*, 30(2), 481–498. https://doi.org/10.1111/mec.15739

1131 Yadav, S., Stow, A., & Dudaniec, R. Y. (2020). Elevational partitioning in species distribution, abundance and body size of Australian alpine grasshoppers (*Kosciuscola*). *Austral Ecology*, 45(5), 609–620. https://doi.org/10.1111/aec.12876

1134 Yip, E. C., Powers, K. S., & Avilés, L. (2008). Cooperative capture of large prey solves scaling challenge faced by spider societies. *Proceedings of the National Academy of Sciences*, 105(33), 11818–11822.

1137 Zeuss, D., Brunzel, S., & Brandl, R. (2017). Environmental drivers of voltinism and body size in insect assemblages across Europe: Voltinism and body size in insect assemblages. *Global Ecology and Biogeography*, 26(2), 154–165. https://doi.org/10.1111/geb.12525

1140

1141

1142 **Table 1:** The eight essential dichotomies implied by the study of body size variation in

1143 arthropods in ecological and evolutionary research. The choices appear in bold.

Restrictions for the literature meta-analysis

Due to prior choices

1. **Ectotherms** vs. endotherms

2. **Intraspecific** vs interspecific variation

3. **Structural body size** vs. condition-dependent body size (see Box1)

Due to lack of studies

4. **Field** vs. experiments

5. **Bergmann's rule** vs. Temperature-Size Rule

6. **Macro** vs. microecological/spatial gradients

Possible comparisons within our field study

7. Direct vs. indirect development

8. Wandering vs. web-building spiders

1144

1145
1146 **Table 2:** Body size variations in response to macroecological gradients in spiders. Response can be negative (-), positive (+), curvilinear (C), humped-shaped (H), none (N), sawtooth (S) or U-shaped (U). The full table of body size variation found in all arthropods is given in Supplementary Table S1 and at https://doi.org/10.6084/m9.fishshare.27118986.v3. References: (Ameline et al., 2018; Beckers et al., 2020; Bowden et al., 2013; Cabon et al., 2024; Dahirel et al., 2019; Hein et al., 2015, 2018, 2019; Høye & Hammel, 2010; Lee et al., 2012; Lowe et al., 2014; Mammola et al., 2019; Monsimet et al., 2021; Opell et al., 2007; Puzin et al., 2014; Viel et al., 2022; Wolz et al., 2020).

<table><thead><tr><th>Gradient</th><th>Species</th><th>Family</th><th>Guild</th><th>Measure</th><th>Response</th><th>Reference</th></tr></thead><tbody><tr><td rowspan="2">Latitude</td><td>Amaurobioides maritima</td><td>Anyphaenidae</td><td>Orb-weaver</td><td>Carapace, abdomen lengths</td><td>N</td><td>Opell 2007</td></tr><tr><td>Argiope bruennichi</td><td>Araneidae</td><td>Orb-weaver</td><td>Total length of patella + tibia of the first right leg</td><td>-</td><td>Wolz et al. 2020</td></tr><tr><td rowspan="10">Elevation</td><td>Dolomedes fimbriatus</td><td>Pisauridae</td><td>Non web-building</td><td>Prosoma width and length</td><td>N</td><td>Monsimet et al. 2021</td></tr><tr><td>Pardosa agrestris purbeckensis</td><td>Lycosidae</td><td>Non web-building</td><td>Carapace length</td><td>-</td><td>Puzin et al. 2014</td></tr><tr><td>Arctosa insignata</td><td>Lycosidae</td><td>Non web-building</td><td></td><td>-</td><td>Hoye & Hammel 2010</td></tr><tr><td>Pardosa uintana</td><td></td><td></td><td></td><td>-</td><td>Bowden et al. 2013</td></tr><tr><td>Pardosa glacialis</td><td></td><td></td><td></td><td>N</td><td></td></tr><tr><td>Pardosa hyperborea</td><td></td><td></td><td></td><td>N</td><td></td></tr><tr><td>Pardosa hyperborea</td><td></td><td></td><td></td><td>+</td><td>Ameline et al. 2018</td></tr><tr><td>Pardosa palustris</td><td></td><td></td><td></td><td>+</td><td></td></tr><tr><td>Pardosa palustris</td><td></td><td></td><td></td><td>C</td><td>Hein et al. 2019</td></tr><tr><td>Pardosa palustris</td><td></td><td></td><td></td><td>+</td><td>Hein et al. 2018</td></tr><tr><td>Pardosa palustris</td><td>Lycosidae</td><td>Non web-building</td><td>Prosoma width</td><td>N</td><td>Beckers et al. 2020</td></tr><tr><td>Pardosa palustris</td><td></td><td></td><td></td><td>N</td><td></td></tr><tr><td>Pardosa amentata</td><td></td><td></td><td></td><td>N</td><td></td></tr><tr><td>Pardosa lugubris</td><td></td><td></td><td></td><td>N</td><td>Hein et al. 2015</td></tr><tr><td>Pardosa hyperborea</td><td></td><td></td><td></td><td>N</td><td></td></tr><tr><td>Pardosa riparia</td><td></td><td></td><td></td><td>N</td><td></td></tr><tr><td>Pardosa hyperborea</td><td></td><td></td><td></td><td>-</td><td></td></tr><tr><td>Pardosa furcifera</td><td></td><td></td><td></td><td>N</td><td>Viel et al. 2022</td></tr><tr><td rowspan="10">Urbanization</td><td>Myro kerguelensis</td><td>Toxopidae</td><td></td><td>Carapace and sternum width</td><td>N</td><td>Lee et al. 2012</td></tr><tr><td>Waitkera waitakerensis</td><td>Uloboridae</td><td>Orb-weaver</td><td>Femur I length</td><td>N</td><td>Opell et al. 2007</td></tr><tr><td>Nephila plumipes</td><td>Araneidae</td><td>Orb-weaver</td><td>Tibia length of leg I</td><td>+</td><td>Lowe et al. 2014</td></tr><tr><td>Araneus diadematus</td><td></td><td></td><td>Prosoma width</td><td>-</td><td>Dahirel et al. 2019</td></tr><tr><td>Pardosa prativaga</td><td></td><td></td><td></td><td>+ (temp on females)</td><td></td></tr><tr><td>Pardosa pullata</td><td>Lycosidae</td><td>Non web-building</td><td></td><td>+ (local temp on females)</td><td></td></tr><tr><td>Pardosa cf. tenuipes</td><td></td><td></td><td></td><td>N</td><td></td></tr><tr><td>Bathyphantes gracilis</td><td></td><td></td><td></td><td>N</td><td></td></tr><tr><td>Diplostyla concolor</td><td></td><td></td><td></td><td>N</td><td></td></tr><tr><td>Erigone dentipalpis</td><td></td><td></td><td></td><td>N</td><td></td></tr><tr><td>Oedothorax fuscus</td><td>Linyphiidae</td><td>Orb-weaver</td><td>Prosoma width and right leg IV segments length</td><td>N</td><td>Cabon et al. 2024</td></tr><tr><td>Oedothorax retusus</td><td></td><td></td><td></td><td>N</td><td></td></tr><tr><td>Tenuiphantes tenuis</td><td></td><td></td><td></td><td>N</td><td></td></tr></tbody></table>
<table><tr><td></td><td>Hahnia nava</td><td>Hahniidae</td><td>Orb-weaver</td><td>N</td></tr><tr><td></td><td>Pachygnatha degeeri</td><td>Tetragnathidae</td><td>Orb-weaver</td><td>N</td></tr><tr><td>Quality</td><td></td><td></td><td></td><td></td></tr><tr><td>(climatic, topographical and geomorphological variables)</td><td>Vesubia jugorum</td><td>Lycosidae</td><td>Non web-building</td><td>Femur, tibia and metatarsus length, and carapace length and width</td></tr></table>

1154

1155

**Table 3:** Sexual size dimorphism (SSD) variation along macroecological gradients in arthropods: D: direct, I: indirect development. References: (Bidau & Martí, 2007; Bowden et al., 2013; Ciplak et al., 2008; Dudaniec et al., 2022; Høye et al., 2009; Høye & Hammel, 2010; Jarčuška et al., 2023; Laiolo et al., 2013; Marshall et al., 2013; Outomuro et al., 2021; Papandreou et al., 2023; Tanaka, 2024; Yadav et al., 2020).

<table><thead><tr><th>Gradient</th><th>Species</th><th>Development</th><th>Measure</th><th>Response</th><th>Reference</th></tr></thead><tbody><tr><td rowspan="5">Latitude</td><td><strong>Coleoptera</strong></td><td></td><td></td><td></td><td></td></tr><tr><td><em>Agrilus planipennis</em></td><td>I</td><td>Dorsal length and dry mass</td><td>Negative for ♀</td><td>Marshall et al. 2013</td></tr><tr><td><strong>Odonata</strong></td><td></td><td></td><td></td><td></td></tr><tr><td><em>Ischnura elegans</em></td><td>I</td><td>PCA with total length, wing length, abdomen length, thorax width and S4 width</td><td>Positive for ♂, none for ♀</td><td>Dudaniec et al. 2021</td></tr><tr><td><em>Lestes sponsa</em></td><td>I</td><td>Head width, wing centroid size</td><td>None</td><td>Outomouro et al. 2021</td></tr><tr><td rowspan="5">Elevation</td><td><strong>Orthoptera</strong></td><td></td><td></td><td></td><td></td></tr><tr><td><em>Dichroplus pratensis</em></td><td>D</td><td>Total body length</td><td>None</td><td>Bidau & Marti 2007</td></tr><tr><td><em>Locusta migratoria</em></td><td>D</td><td>Head width, hind femur length, and forewing length</td><td>More positive for ♀</td><td>Tanaka 2024</td></tr><tr><td><strong>Araneae</strong></td><td></td><td></td><td></td><td></td></tr><tr><td><em>Pardosa lapponica</em></td><td>D</td><td>Carapace width</td><td>More negative for ♀</td><td>Bowden et al. 2013</td></tr><tr><td><em>Alopecosa aculeata</em></td><td>D</td><td>Carapace width</td><td>Positive for ♂, none for ♀</td><td></td></tr><tr><td><em>Pardosa glacialis</em></td><td>D</td><td>Carapace width</td><td>Negative for ♀, none for ♂</td><td>Høye & Hammel 2010</td></tr><tr><td><em>Pardosa groenlandica</em></td><td>D</td><td>Carapace width</td><td>Negative for ♀, none for ♂</td><td></td></tr><tr><td rowspan="10">Elevation</td><td><strong>Lepidoptera</strong></td><td></td><td></td><td></td><td></td></tr><tr><td><em>Afrasura cf. numida</em></td><td>I</td><td></td><td>Positive for ♂, none for ♀</td><td></td></tr><tr><td><em>Asythosia velutina</em></td><td>I</td><td></td><td>More positive for ♂ than ♀</td><td></td></tr><tr><td><em>Eilema cf. fletcheri</em></td><td>I</td><td></td><td>Positive for ♂, none for ♀</td><td></td></tr><tr><td><em>Galtara sp. "1"</em></td><td>I</td><td>Right forewing length, from the base of the apex</td><td>More positive for ♂ than ♀</td><td>Papandreou et al. 2023</td></tr><tr><td><em>Ligulosia costimaculata</em></td><td>I</td><td></td><td>Negative for ♂, none for ♀</td><td></td></tr><tr><td><em>Palaeugoa camerunensis</em></td><td>I</td><td></td><td>More positive for ♂ than ♀</td><td></td></tr><tr><td><em>Mylantria xanthospila</em></td><td>I</td><td></td><td>None for ♂, negative for ♀</td><td></td></tr><tr><td><strong>Orthoptera</strong></td><td></td><td></td><td></td><td></td></tr><tr><td><em>Chorthippus cazurroi</em></td><td>D</td><td>Hind femur length</td><td>Negative for ♀, none for ♂</td><td>Laiolo et al. 2013</td></tr><tr><td><em>Dichroplus pratensis</em></td><td>D</td><td>Total body length</td><td>None</td><td>Bidau & Marti 2007</td></tr><tr><td><em>Chorthippus vagans</em></td><td>D</td><td>Tegmina length</td><td>Negative for ♂, positive for ♀</td><td>Ciplak et al. 2008</td></tr></tbody></table>
<table><tbody><tr><td>Kosciuscola usitatus</td><td>D</td><td>Femur length</td><td>Negative for both</td><td>Yadav et al. 2020</td></tr><tr><td>Kosciuscola tristis</td><td>D</td><td>Femur length</td><td>None in ♂, negative in ♀</td><td>Yadav et al. 2020</td></tr><tr><td>Kosciuscola cognatus</td><td>D</td><td>Femur length</td><td>Negative in ♂, none in ♀</td><td>Yadav et al. 2020</td></tr><tr><td>Pholidoptera griseoaptera</td><td>D</td><td>Pronotum width, femur length, tibia length and ovipositor length</td><td>None</td><td>Jarčuška et al. 2023</td></tr><tr><td colspan="5"><strong>Temperature</strong></td></tr><tr><td>Earlier snowmelt</td><td>Araneae</td><td>Carapace width</td><td>More positive for ♀</td><td>Høye et al. 2009</td></tr><tr><td>Mean annual temperature</td><td>Orthoptera</td><td>Hind femur length</td><td>More positive for ♀</td><td>Laiolo et al. 2013</td></tr><tr><td>Mean annual temperature</td><td>Chorthippus cazurroi</td><td>Hind femur length</td><td>More positive for ♀</td><td></td></tr><tr><td></td><td>Chorthippus parallelus</td><td></td><td></td><td></td></tr></tbody></table>

1161

1162

Figures

1163

<figure><img src="image_3.png" /></figure>

1164

1165

[single column: width 60mm x height 28 mm] Figure 1 Structural body size measurement in the wolf spider *Pardosa furcifera* (Araneae, Lycosidae). From Ameline *et al.*, (2017). A: carapace length and width, B: first femur length.

1166

1167

<figure><img src="image_4.png" /></figure>

1168

1169

[1.5 columns: width 92 mm x height 60 mm] Figure 2 Body size variation linked to temperature variation. Adapted from Kingsolver & Huey, (2008). Red: "bigger is better", green: "hotter is smaller", blue: "hotter is better".

1170

1171
<figure><img src="image_5.png" /></figure>

1172

1173 [1.5 columns: width 80mm x height 50.2 mm] Figure 3 Intraspecific body size response to

1174 elevation and latitude in arthropods. We separately report studies on spider species along

1175 elevational gradients. We distinguished taxa with direct from taxa with indirect development

1176 (Schäfer, 1976). The number of species is reported below each barplot. Details of the studies are

1177 given in Supplementary Table S1.

1178