DOI: 10.5061/dryad.hqbzkh1nv
title: Tackling local ecological homogeneity: Finding intraspecific trait variability in local populations of Mediterranean plants

description: Local homogeneity, in ecology, is the often undisclosed assumption that
 variability within populations is negligible or mostly distributed evenly.
 In large areas, this can lead to the aggregation of different populations
 without regard for their unique needs and characteristics, such as drought
 sensitivity and functional traits distributions. Here we discuss whether
 this assumption can be justified, and we hypothesize that discerning the
 source of variation between plasticity and adaptation could be a feasible
 approach to formulate an informed decision. We test this hypothesis on
 plants, resorting to a common garden experiment to determine the source of
 variation of several plant functional traits at a local scale (~60 Km) of
 three wild species: Quercus ilex, Pistacia lentiscus and Cistus
 salviifolius. Individuals of each species were sourced from three key
 sites chosen along a local aridity gradient. Our approach led to the
 rejection of the local homogeneity assumption for Q. ilex and C.
 salviifolius at this scale due to the adaptive divergence observed among
 neighbouring populations. This case study provides evidence that
 addressing local homogeneity can highlight diverging populations in a
 relatively simple way. We conclude that gathering empirical evidence on
 intraspecific variability is a feasible approach that can provide
 researchers with solid bases to decide whether to adopt the local
 homogeneity assumption or not.
description: This data were obtained over the course of two sampling
 campaigns. The first campaign happened in June-August
 2021 <em>in situ</em>, as samples were collected directly from
 adult individuals from three populations of the <em>Latium
 </em>region in central Italy, namely <em>Castel
 Fusano</em> (41°43'23.6" N, 12°19'55.7"
 E), <em>La Farnesiana</em> (42°11'38.9" N, 11°52'33.1"
 E) and <em>Tivoli </em>(41°57'51.5" N, 12°48'54.9"
 E). The
 second campaign happened in June-August 2022 <em>ex situ</em>,
 as measurements were obtained from seedlings grown in a common garden from
 seeds collected at the original provenance sites.
 We followed the same standard
 procedures described by Perez-Harguindeguy <em>et al.
 </em>(2016), "Corrigendum to: New handbook for standardised
 measurement of plant functional traits worldwide."
 (<em>Australian Journal of
 botany</em>, <em>64</em>(8), 715-716), to directly
 measure plant height (H), fresh leaf area (LA), and leaf thickness (LT).
 Leaf mass was measured at collection (FM), after 48h at 5 °C in the dark
 (SM) and after being kept at 90 °C until costant weight was reached (DM).
 Stomatal density (SD) was obtained using leaf gel impressions and digital
 microscopy.<br> All the aforementioned measures were used to
 obtain the traits presented in this dataset: LMA  (mgcm<sup>-2</sup>, LMA = DM/LA), LDMC (mgmg<sup>-1</sup>, LDMC= DM/SM), LTD (mgcm<sup>-3</sup> LTD= LMA/LT), SAI (n° of stomata*mm<sup>-2</sup>, SAI= SD*stomatal length). H (cm) and SD (n° of stomata*mm<sup>-2</sup>) were also directly included in the dataset. Dixon test was used to highlight potential outliers, which are flagged with the red fields in the dataset file.
description: # Tackling local ecological homogeneity: finding intraspecific trait
 variability in local populations of Mediterranean plants
 [https://doi.org/10.5061/dryad.hqbzkh1nv](https://doi.org/10.5061/dryad.hqbzkh1nv) The dataset contains several plant functional traits from three populations of *Quercus ilex*, *Pistacia lentiscus* and *Cistus salviifolius* obtained both *in situ* and *ex situ*, from seedlings cultivated in a common garden. The included trait are total plant height (H), leaf mass per area (LMA), leaf dry matter content (LDMC), leaf tissue density (LTD), stomatal density (SD) and stomatal area index (SAI). Traits were used to determine whether the intraspecific variability observed between the populations in situ would be inherited by seedlings cultivated *ex situ* in common conditions. Our results show significant variations for at least one trait between populations of *Q. ilex* and *C. salviifolius* but not *P. lentiscus* ex situ, and significant variations between populations of all three species for at least one trait *in situ*. ## Description of the data and file structure Data are presented in a simple data sheet, with the column Origin indicating whether the measurement was obtained *in situ*, in natural conditions, or *ex situ*, after being grown in a common garden. H (cm) refers to total plant height measured from soil to peak, LMA (mgcm<sup>-2</sup>) is leaf mass per area, obtained from the ratio between leaf dry mass and total leaf area (petiole included), LDMC (mgmg<sup>-1</sup>) is leaf dry matter content, the ratio between leaf dry mass and water-saturated leaf mass, LTD (mgcm<sup>-3</sup>) is leaf tissue density, and is the ratio between LMA and leaf thickness. SD (n° of stomata\*mm<sup>-2</sup>) is stomatal density, and is the count of stomata in a mm<sup>-2</sup> estimated from the direct count of stomata in a 220x165 μm<sup>2 </sup>area from leaf gel impressions. SAI (n° of stomata\*mm<sup>-1</sup>) is the stomatal area index, and was obtained by multiplying SD for the mean stomatal length. The spreadsheet was presented with some data highlighted by red fields. These specific values were highlighted as potential outliers by a Dixon test. An important note: while LMA, LDMC and LTD were obtained on the same leaf for each plant, SD and SAI were obtained on different leaves, due to the sampling process being incompatible. Each trait is therefore traceable to the same individual but not to the same leaf. SD and SAI were obtained on a lower amount of leaves, thus some N/As are present for missing data. To avoid bias and ensure data comparability, H *ex situ* was only measured on plants that sprouted in the same week, leading to a lower amount of individuals measured for this trait in the common garden. This didn't affect LMA, LDMC and LTD since these traits were measured on leaves of comparable age. This produced some missing data (N/A). ## Sharing/Access information N/A ## Code/Software N/A