DOI: 10.5061/dryad.z612jm6df
title: Environmental variation in sex ratios and sexual dimorphism in three wind-pollinated dioecious plant species

description: Variation in plant sex ratios is often attributable to sex-specific
 mortality in heterogeneous environments that differentially limit male and
 female plant reproduction. Yet sexual dimorphism and plastic responses to
 environmental heterogeneity are common and may co-vary with variation in
 sex ratios. Here, we show that the sex ratio and the degree of sexual
 dimorphism for a number of plant traits varied along climatic and
 elevation gradients in three wind-pollinated dioecious species, Rumex
 lunaria, Urtica dioica and Salix helvetica. Some of the observed
 sex-specific responses to climatic variation are consistent with greater
 sensitivity of females to water scarcity, but most responses rather point
 to the greater sensitivity of males to ecological stress, consistent with
 larger male reproductive effort, as has been commonly reported for
 wind-pollinated plants. In contrast, we found no evidence for variation in
 either sex ratios or sexual dimorphism expected under sexual selection.
 Interestingly, sex ratios and sexual dimorphism varied both along distinct
 and the same ecological axes of variation, suggesting that the evolution
 of sexual dimorphism in the measured traits was not sufficient to prevent
 sex-specific mortality.
description: We counted males and females and measured plant traits at 14
 naturally occurring populations of <em>R. lunaria</em> on the
 island of Tenerife (Spain) in April 2017, at eleven populations of
 <em>U. dioica</em> in ‘Le Plateau’ area (Switzerland) in
 September 2017, and at ten populations of <em>S.
 helvetica</em> in the Alps (Switzerland) in July 2017. To ensure an
 unbiased sample, we recorded the sex of every individual identified,
 moving through the populations in only one direction to avoid sampling any
 individual more than once. For each species, we counted all individuals up
 to a maximum of 150 per population.  
 Plant height and canopy width were recorded for all sampled
 mature flowering individuals in <em>R. lunaria</em> and
 <em>S. helvetica</em>.  
 For <em>U. dioica</em>, due to its clonal habits,
 we estimated plant cover for roughly half of the mature individuals
 identified, using a visual criterion to determine the shape best
 approximating the plant cover per individual (e.g., circle, ellipse, or
 rectangle), and we further measured the parameters of the projected shape
 to assess their cover.   For
 each population, we calculated the operational sex ratio (SR) as the
 proportion of females divided by the total number of flowering individuals
 in a population. We further calculated, for each population, two sexual
 dimorphism indices, one for leaf area and one for plant size, hereafter
 termed SLD and SSD, respectively. The SLD and SSD were calculated as the
 log of the ratio of the mean female to the mean male leaf area or plant
 size, respectively (Smith 1999), with a null expectation of 0 for no
 difference.<br>   We extracted for
 each population ten bioclimatic variables at a spatial resolution of 1 km
 2 from WorldClim global climate layers (Fick and Hijmans 2017) and
 calculated the principal components (PC) axes of the bioclimatic
 variables. Please, find additional
 details in the Readme file and in the article: Bürli,
 S., Pannell, J. R., & Tonnabel, J. (2022). Environmental variation
 in sex ratios and sexual dimorphism in three wind‐pollinated dioecious
 plant species. Oikos, e08651. https://doi.org/10.1111/oik.08651
description: A detailed README file is available with the datasets.
 The data are not standardised and missing values are noted by NA.
 The data have been checked for outliers. Relationship
 between files: the number of the populations refer to the same populations
 between the files of the same species. For example, the population one for
 Rumex lunaria refers to the same population one in the following documents
 "data_SPECIES_pop.csv", "data_SPECIES_indiv.txt" and
 "data_SPECIES_leaf.txt".