DOI: 10.5061/dryad.jm63xsjqx
title: Data from: Drought resistance drives population temporal stability of annuals in drylands

description: Understanding the mechanisms determining population temporal stability is
 key to explaining species diversity and coexistence, and to maintaining
 multiple ecosystem functions over time. Functional traits should offer
 mechanistic insights into the drivers of stability, but the generalization
 of a trait–stability relationship is lacking. Our overarching hypothesis
 is that traits predicted by bet-hedging theory to reduce variability in
 population size, i.e., delayed germination and/or bigger seeds and/or
 traits associated with higher drought resistance (high intrinsic water-use
 efficiency, high turgor loss point, slow relative growth rate, high leaf
 dry matter content, low SLA), lead to higher population temporal
 stability. We linked these traits to the year-to-year variation in winter
 annuals’ abundance of 178 populations (66 species) over 13 years. We
 tested the generality of these relationships in a biodiversity hotspot
 along a gradient of rainfall mean, variability, and unpredictability,
 defining three climates (Mediterranean, semi-arid, arid), considering also
 the spatial micro-heterogeneity defined by perennial shrubs. Away from
 shrubs, higher drought resistance was consistently associated with higher
 population stability in all climates. Under the shrubs, however, this
 relationship disappeared or was reversed. Delayed germination predicted
 higher stability in the arid open habitat only. Our results unveiled
 diverse drought resistance strategies within annuals in drylands, and
 elucidated their influence on population temporal stability. Our results
 challenge the long-standing assumption that delayed germination is the
 most important bet-hedging trait for annuals in drylands. Finally, we
 highlight the crucial need of including local microhabitat conditions in
 the assessment of population stability. Synthesis: The detection
 of drought resistance as a key driver of population temporal stability
 represents a significant advancement in evolutionary theory, trait-based
 ecology, and our understanding of community stability.
description: # Data from: Drought resistance drives population temporal stability of
 annuals in drylands Dataset DOI:
 [10.5061/dryad.jm63xsjqx](https://doi.org/10.5061/dryad.jm63xsjqx) ##
 Description of the data and file structure This dataset includes
 species‑level functional trait measurements (relative growth rate, RGR;
 leaf carbon isotopic ratio, δ¹³C; osmotic potential at turgor loss point,
 TLP; specific leaf area, SLA; leaf dry matter content, LDMC; germination
 fraction; and seed size) of winter annual species, calculated as averages
 across five individuals per species measured in 2022. It also includes
 interannual variability in species population size, expressed as the
 coefficient of variation (CV) of individual counts from winter growing
 seasons between 2001/2002 and 2014/2015 in permanent plots, with CV values
 averaged across five plots per microhabitat in each climate. Data were
 collected across four climate types (arid, semi‑arid, Mediterranean, and
 mesic‑Mediterranean) and two microhabitats (open areas and under shrubs),
 in Israel. ### Files and variables #### File: traits_stability.csv
 **Description:** Drought resistance traits (SLA, LDMC, RGR, CarbonRatio,
 TLP) were measured on five individuals per species, and seed traits
 (Germination, Seedmass) were measured on 10 seeds per individual. Missing
 values in the dataset are indicated as `NA`. ##### Variables * Species:
 species name (genus_species) * Site: climate type (A: arid, SA: semi-arid,
 M: Mediterranean) * Microhabitat: microhabitat type (O: open area, S:
 under shrubs) * CV: coefficient of variation in population size across the
 13 years (CV = standard deviation of individual counts/mean of individual
 counts) * SLA: Specific Leaf Area (cm^2^.g^−1^) * LDMC: Leaf Dry Matter
 Content (g.g^−1^) * RGR: Relative Growth Rate (day^-1^) *
 CarbonRatio: leaf carbon isotopic ratio (‰). It is the integrated
 long-term measure of the ratio of ^13^C over ^12^C. * TLP: osmotic
 potential at turgor loss point (MPa). It is the measure of the capability
 of plants to maintain cell turgor under water stress. *
 Germination: germination fraction (proportion, 0–1). * Seedmass: seed size
 (g) ## Code/software All the analyses were performed using the R software
 version 4.2.2.