bluuebunny/crossref_metadata_2025_split huggingface dataset:
Leaf adaptations of evergreen and deciduous trees of semi‐arid and humid savannas on three continents
Authors: Tomlinson Kyle W. , Poorter Lourens , Sterck Frank J. , Borghetti Fabian , Ward David , de Bie Steven , van Langevelde Frank 
Published: May 2013

Summary

Drought stress selects for a suite of plant traits at root, stem and leaf level. Two strategies are proposed for trees growing in seasonally water‐stressed environments: drought tolerance and drought avoidance. These are respectively associated with evergreen phenology, where plants retain their leaves throughout the year, and deciduous phenology, where plants drop their leaves during dry seasons. Evergreen species are thought to have leaf traits supporting lower photosynthesis and transpiration rates, in order to conserve water during dry periods.

We evaluated 18 morphological, chemical and physiological leaf traits of 51 abundant savanna tree species that differed in leaf habit (deciduous and evergreen), selected from two climate types (semi‐arid and humid) in three continents (Australia, Africa and South America) (annual rainfall range: 500–1550 mm), and grown in a common garden experiment. We hypothesised that evergreen species have more conservative water use and differ more across climate types than deciduous species because evergreen species are forced to endure extended water deficits during dry seasons.

Trait shifts between semi‐arid and humid savannas did not differ between evergreen and deciduous species.

Evergreen species had similar assimilation rates but lower photosynthetic water‐use efficiency (PWUE) than deciduous species, possibly to extend their leaf lifespans by protecting their photosynthetic machinery from overheating through evaporative cooling.

Species of humid and semi‐arid environments did not differ with respect to assimilation rate or PWUE, but semi‐arid species did have smaller leaf sizes and greater leaf potassium and phosphorus concentrations. These traits may enable semi‐arid species to maximize growth during episodes of favourable moisture availability.

Species from the three continents differed in their leaf traits. These probably reflect the greater proportion of evergreen species in Australia as compared to the other continents and generally infertile soils in the South American sampling sites compared to the wider fertility range in the African sites.

Synthesis: Water stress in savannas does not select for more conservative water use, but may select for rapid adjustment to prevailing water conditions and for heat avoidance mechanisms.
Let the best one stay: screening of ant defenders by Acacia host plants functions independently of partner choice or host sanctions
Authors: Heil Martin 
Published: May 2013

Summary

Multiple plant species are engaged in defensive mutualisms with members of the third trophic level. However, mutualisms are prone to exploitation by low‐quality symbionts that do not provide the adequate service to their host. Can mutualisms proceed only when hosts identify their symbionts in advance or continuously monitor their activity, or are there other mechanisms to avoid the invasion of mutualisms by exploiters?

High‐reward species amongst Mesoamerican Acacia myrmecophytes are dominantly colonized by defending mutualistic ants, whereas about 50% of the low‐reward hosts are inhabited by non‐defending exploiters. I followed the development of recently founded ant colonies on a high‐reward and a low‐reward Acacia host species over 7 months, to investigate whether reward production correlates with a preferred maintenance of defending ants on the respective hosts.

Ant diversity decreased sooner on high‐reward than on low‐reward hosts, and mutualistic ants were more likely to finally dominate the high‐reward hosts. I observed an increased frequency of mutualists replacing parasites at high initial rates of reward production. Apparently, higher nectar provisioning by the host plants shifted the competitive balance between mutualistic and parasitic ants. Independently of the causal reason for the different secretion rates, producing more nectar thereby favours the maintenance of defending mutualists on high‐reward hosts.

Synthesis. The aggressiveness that enables ants to outcompete other ants also underlies their defensive effect against herbivores. I conclude that hosts can preferably associate with high‐quality mutualists without measuring their effectiveness. Mutualisms remain stable when partner screening is based on traits that are relevant for the mutualistic interaction, with no need for the host to have information on the quality or identity of the symbiont.
Latitudinal gradients as natural laboratories to infer species' responses to temperature
Authors: De Frenne Pieter , Graae Bente J. , Rodríguez‐Sánchez Francisco , Kolb Annette , Chabrerie Olivier , Decocq Guillaume , De Kort Hanne , De Schrijver An , Diekmann Martin , Eriksson Ove , Gruwez Robert , Hermy Martin , Lenoir Jonathan , Plue Jan , Coomes David A. , Verheyen Kris 
Published: May 2013

Summary

Macroclimatic variation along latitudinal gradients provides an excellent natural laboratory to investigate the role of temperature and the potential impacts of climate warming on terrestrial organisms.

Here, we review the use of latitudinal gradients for ecological climate change research, in comparison with altitudinal gradients and experimental warming, and illustrate their use and caveats with a meta‐analysis of latitudinal intraspecific variation in important life‐history traits of vascular plants.

We first provide an overview of latitudinal patterns in temperature and other abiotic and biotic environmental variables in terrestrial ecosystems. We then assess the latitudinal intraspecific variation present in five key life‐history traits [plant height, specific leaf area (SLA), foliar nitrogen:phosphorus (N:P) stoichiometry, seed mass and root:shoot (R:S) ratio] in natural populations or common garden experiments across a total of 98 plant species.

Intraspecific leaf N:P ratio and seed mass significantly decreased with latitude in natural populations. Conversely, the plant height decreased and SLA increased significantly with latitude of population origin in common garden experiments. However, less than a third of the investigated latitudinal transect studies also formally disentangled the effects of temperature from other environmental drivers which potentially hampers the translation from latitudinal effects into a temperature signal.

Synthesis. Latitudinal gradients provide a methodological set‐up to overcome the drawbacks of other observational and experimental warming methods. Our synthesis indicates that many life‐history traits of plants vary with latitude but the translation of latitudinal clines into responses to temperature is a crucial step. Therefore, especially adaptive differentiation of populations and confounding environmental factors other than temperature need to be considered. More generally, integrated approaches of observational studies along temperature gradients, experimental methods and common garden experiments increasingly emerge as the way forward to further our understanding of species and community responses to climate warming.
The impact of secondary compounds and functional characteristics on lichen palatability and decomposition
Authors: Asplund Johan , Wardle David A. 
Published: May 2013

Summary

There has been much recent interest in understanding how functional traits of vascular plant species drive ecological processes such as herbivory and litter decomposition. In plants, these two processes are often driven by the same or similar suites of traits and therefore correlate across species. However, few studies have considered how traits of plant‐like life forms such as lichens determine species differences in their effects on ecological processes. This is despite the significant contribution of lichens to carbon and nutrient cycling in many environments.

We collected 28 lichen species that differed in their growth form, substrate type and capacity to fix N, and determined key traits for each species. For each species, we performed a feeding bioassay using the generalist snail Cepaea hortensis and carried out a laboratory bioassay to assess decomposability. We did these tests both with intact lichen material containing natural concentrations of carbon‐based secondary compounds (CBSCs), and material that had been acetone rinsed to reduce concentrations of CBSCs, to evaluate the effect of CBSC on palatability and decomposability.

We found that reducing CBSC concentrations greatly increased palatability for 17 species, and decomposability of 10 species. However, decomposability was correlated with several lichen traits while palatability was not, regardless of whether or not CBSCs were removed, and we therefore found no relationship between decomposability and palatability across species. Decomposability and palatability both varied, but in contrasting directions, among N‐fixing vs. non‐fixing lichens, lichens with different growth forms and those from contrasting substrate types. As such, N‐fixing lichens had higher decomposition rates but lower consumption rates than non‐fixing lichens, while foliose species had higher decomposition rates but lower consumption rates than fruticose species.

Synthesis: We have shown that lichen CBSCs regulate key processes such as lichenivory and decomposition, that lichen decomposability but not palatability are related to traits, and that these two processes are unrelated across species. These results highlight the potential role of lichen species differences in influencing ecosystem processes relating to decomposition and nutrient cycling and the role that grazers may play in driving this.
Local adaptation and plasticity of Erysimum capitatum to altitude: its implications for responses to climate change
Authors: Kim Eunsuk , Donohue Kathleen 
Published: May 2013

Summary

Alpine plants are at high risk because of climate change. Assessing the performance of alpine plant species across different altitudes is useful for predicting how they may respond to changing climate. Adaptation and plasticity of early life stages are of particular interest since seed germination and seedling establishment could be crucial life‐history stages for environmental tracking and population persistence of sexually reproducing plants.

To evaluate past adaptation and the potential to accommodate future climate conditions, seeds and seedlings of Erysimum capitatum were reciprocally transplanted between alpine and low‐altitude sites.

When grown in a common field environment, E. capitatum from alpine and lower‐altitude populations differed from each other in germination, size and morphological traits. Planting altitude also influenced those traits, indicating that population differentiation and plasticity to altitudinal conditions both contributed to differences in the performance of high‐ vs. low‐altitude plants. Seeds tended to germinate more in their native habitat than in the foreign habitat. Alpine plants survived more than low‐altitude plants at high altitude, and they suffered higher mortality when they were planted in low‐altitude sites. The production of multiple rosettes, a characteristic morphology of alpine E. capitatum, was negatively associated with survival at low altitude. In contrast to alpine populations, a survival advantage of low‐altitude populations in low‐altitude sites was not evident in this experiment.

Synthesis. Because climate change is projected to cause alpine environments to become more similar to low‐altitude environments, alpine Erysimum capitatum is expected to suffer reduced seedling recruitment and higher mortality as a direct response to altered environment and possibly as a result of past adaptation to high altitude. In particular, the production of multiple rosettes, an adaptive trait to the current alpine environment, would constrain plant survival should those environments come to resemble low altitude. Moreover, the limited fitness advantage of low‐altitude E. capitatum in low‐altitude conditions suggests that environmental tracking by low‐altitude populations might have a limited role in maintaining future populations.
Longitudinal analysis in Plantago: strength of selection and reverse age analysis reveal age‐indeterminate senescence
Authors: Shefferson Richard P. , Roach Deborah A. 
Published: May 2013

Summary

Senescence is usually viewed as increased age‐specific mortality or decreased age‐specific fecundity due to the declining ability of natural selection to remove deleterious age‐specific mutations with age. In herbaceous perennial plants, trends in age‐specific mortality are often confounded by size. Age‐indeterminate senescence, where accumulated physiological damage varies strongly with environment, may be a better model of senescence in these species.

We analysed trends in size and fertility in Plantago lanceolata, using a long‐term demographic census involving > 10 years and > 8000 individuals in four cohorts. We used elasticity and pairwise invasion analysis of life‐history function parameterized age × stage matrices to assess whether the force of natural selection declined with age. Then, we used reverse age analysis of size and fertility to assess whether age‐indeterminate senescence occurred. Reverse age analysis uses longitudinal data for individuals that have died to look at trait patterns as a function of both age and remaining time to death. We hypothesized that (i) the strength of natural selection would decline strongly with age, and (ii) physiological condition would deteriorate for several years prior to death.

Both elasticity and invasion analyses suggested that the strength of natural selection through mortality declined strongly with age once size was accounted for. Further, reverse age analyses showed that individuals shrank for 3 years prior to death, suggesting physiological decline. Inflorescence production declined with age, and also declined in the 3 years prior to death regardless of overall age.

Synthesis. The hypothesis that plants escape senescence generally assumes that plants can continue to grow larger and increase reproduction as they get older. The results here show that size and reproduction decline with age and the rates of these declines towards death are life span‐ and age dependent. Further research is needed to delineate the importance of age‐determinate vs. age‐indeterminate factors in senescence patterns across species.
Photo‐oxidative stress markers reveal absence of physiological deterioration with ageing in Borderea pyrenaica, an extraordinarily long‐lived herb
Authors: Morales Melanie , Oñate Marta , García María B. , Munné‐Bosch Sergi 
Published: May 2013

Summary

In animals, age‐associated disorders are believed to be connected to shifts in the antioxidant/pro‐oxidant balance in favour of oxidative stress. However, the contribution of oxidative stress to ageing in long‐lived perennials has not been explored to date.

Here, we tested age‐ and sex‐related changes in several photo‐oxidative stress markers in Borderea pyrenaica, a small dioecious geophyte relict of the Tertiary with one of the longest life spans ever recorded for a non‐clonal herb (more than 300 years). Given that survival increases with age in B. pyrenaica, we hypothesized that oxidative stress does not increase with ageing because the species develops improved anti‐oxidant defence.

In three field samplings performed during 2008, 2010 and 2011 in the Central Pyrenees (NE Spain), we examined the effects of ageing and sex on photosynthetic pigment levels, PSII integrity (Fv /Fm ratio), lipid peroxidation, and the extent of photo and anti‐oxidant protection in chloroplasts. Furthermore, we explored whether age and sex affect plant response to severe natural desiccation.

Both male and female plants maintained chlorophyll levels intact, as well as the Fv/Fm ratio and the levels of lipid peroxidation, irrespective of age. This finding suggests the absence of age‐associated oxidative stress at the organismal level. Furthermore, photoprotection mechanisms were found to be similarly efficient in the oldest individuals as in juvenile plants, in terms of xanthophyll cycle de‐epoxidation and accumulation of low‐molecular‐weight antioxidants (carotenoids and tocopherols). Indeed, females over 100 years of age were the most resistant to severe desiccation, maintaining higher leaf hydration levels, less chlorophyll degradation and better PSII integrity under stress than females below 100 years, males below or above 100 years, and juveniles.

Synthesis. Neither males nor females of the extraordinarily long‐lived B. pyrenaica show age‐dependent signs of oxidative stress. This observation suggests that age‐induced oxidative stress is not a universal feature of ageing in perennial plants. Indeed, females older than 100 years showed signs of negative senescence, in that they registered improved physiological performance with increasing age.
Forest edges show contrasting effects on an austral mistletoe due to differences in pollination and seed dispersal
Authors: Magrach Ainhoa , Santamaría Luis , Larrinaga Asier R. 
Published: May 2013

Summary

The alteration and transformation of the areas surrounding native forests due to anthropogenic disturbance can result in differences near this newly created boundary, termed ‘edge effects’.

Our study describes the consequences of edge creation over two successive stages in the life cycle of a hemi‐parasitic mistletoe (Tristerix corymbosus), which determine its reproductive success, in temperate austral forests.

We assessed how flower production and pollinator visits change with distance to the nearest forest edge and how these changes affect fruit set, fruit and seed size, and fruit removal by seed dispersers.

Edge effects were dominated by fruit removal, which increased with the distance to the edge, height in the canopy and fruit availability. As a result, plant reproduction (in terms of seeds produced and fruits removed, which putatively leads to higher seed dispersal) decreased strongly near to forest edges. In contrast, visitation rates of the main pollinator (the hummingbird) were unaffected by edges, and their strong effects on fruit set (including the alleviation of quality pollen limitation arising in the forest interior) might be mitigating the decrease in bumblebee visitation near to forest edges.

Synthesis. Our study shows clearly how secondary and tertiary responses to forest edges acted in opposite directions (increasing or decreasing plant reproductive performance), highlighting the need to study several successive processes that impact upon plant fitness under disturbance. Preserving relatively large patches of old‐growth forest with low perimeter/area ratios would be key to the habitat requirements of the main disperser and pollinator and thus for mistletoe reproductive performance.
Specialist species of wood‐inhabiting fungi struggle while generalists thrive in fragmented boreal forests
Authors: Nordén Jenni , Penttilä Reijo , Siitonen Juha , Tomppo Erkki , Ovaskainen Otso 
Published: May 2013

Summary

The loss of suitable habitats is one of the main causes behind the loss of species and communities. Habitat fragmentation, that is, the division of the remaining habitat into small and isolated fragments, often co‐occurs with the process of habitat loss. The spatial division of habitats decreases connectivity among local populations and generally has a negative effect on population viability, but it can also have a positive effect for some species, for example, due to released competition pressure.

In both animals and plants, certain characteristics such as low dispersal ability and narrow ecological niche are known to be associated with fragmentation vulnerability, but in fungi, systematic analyses have so far been lacking. With their small and highly dispersive spores, fungi could be mainly resource‐limited, not dispersal‐limited.

In this study, we analysed spatial occurrence data on 119 species of wood‐inhabiting fungi to identify the species characteristics that are associated with high extinction risk and fragmentation vulnerability in particular. We modelled resource use and connectivity dependence separately for each species using the presence–absence data on 98 318 dead trees in 496 sites located on a gradient in the duration and intensity of land use in eastern Fennoscandia. We then related species' responses to connectivity to their resource‐use patterns, life‐history characteristics and red‐list status.

Our results show that red‐listed species are highly specialized in their resource use and suffer from loss of connectivity at three spatial scales: along the large‐scale gradient, at the landscape scale and at the scale of a forest stand. In contrast, many of the non‐red‐listed generalist species are actually more likely to occur (per resource unit) in fragmented managed forests than well‐connected natural forests.

Synthesis. We show that the expected number of red‐listed species per a fixed amount of similar resources (dead trees) can be even more than 10 times higher in well‐connected than in fragmented surroundings, and thus, protecting high‐quality areas that are well connected is conservationally more effective than protecting small fragments distributed across the landscape.
Do plant traits retrieved from a database accurately predict on‐site measurements?
Authors: Cordlandwehr Verena , Meredith Rebecca L. , Ozinga Wim A. , Bekker Renée M. , van Groenendael Jan M. , Bakker Jan P. 
Published: May 2013

Summary

Trait‐based approaches are increasingly used to obtain an insight into the functional aspects of plant communities. Since measuring traits can be time‐consuming, large international databases of plant traits are being compiled to share the effort. From these databases, average trait values are often extracted per species by averaging trait values of individuals over multiple populations and habitats. However, the accuracy of such aggregated information from regional databases as a surrogate for on‐site measurements has seldom been tested.

For the local species pool (aggregated at the habitat‐level) and the plant communities on the plots (aggregated at the community‐level), we quantified how accurately trait values for each species measured at the plot (plot scale) and those averaged per species and site (site scale) can be estimated from those retrieved from a North‐west‐European trait database. We analysed three widely used plant traits, canopy height (CH), leaf dry matter content (LDMC) and specific leaf area (SLA), of species occurring in a wet meadow and a salt marsh.

Database values more accurately predicted traits aggregated at the habitat‐level than those aggregated at the community‐level. In addition, traits with lower plasticity, such as LDMC, were more accurately predicted by database values. The performance of database values also depended upon the habitat studied, for example, habitat‐level SLA values were accurately predicted by database values in the wet meadow but inaccurately predicted in the salt marsh.

Synthesis. This study reveals that the accuracy of traits retrieved from a database depends on the level of aggregation (lower at community‐level), the trait (lower in plastic traits) and the habitat type (lower in extreme habitats). For studies focussing on processes mainly acting at the site scale (e.g. trait–environment relationships), traits retrieved from a regional database and filtered according to habitat will probably lead to good results. Whereas studying processes acting at the plot scale (e.g. niche partitioning), requires the additional effort of measuring traits on‐site.