DOI: 10.5061/dryad.cnp5hqcd8
title: Data from: Female-biased population sex ratios caused by genetic rather than ecological mechanisms in dwarf willow (Salix herbacea L.)

description: Biased sex ratios among reproductive individuals are common in plants, but
 the underlying mechanisms, as well as the evolutionary consequences, are
 not well understood. The classical theory of Düsing and Fisher predicts an
 equal primary sex ratio at seed production, based on the selective
 advantage of the rare sex. Biased sex ratios among reproductive plants can
 arise from sexual dimorphism in survival and flowering. Sex ratio biases
 can also be present from the seed stage; in these cases, assumptions of
 Düsing’s and Fisher’s theory, for example, random mating or demographic
 equilibrium, are thought to be violated. We investigated mechanisms
 leading to female-biased sex ratios in the arctic-alpine dwarf
 willow Salix herbacea L. We studied sex ratios in three natural
 populations over three years as well as in 29 crosses (full-sib families)
 under controlled conditions over four growth periods. We tested whether
 sex ratio was associated with habitat parameters (elevation and snowmelt
 time), or with germination, survival or flowering, and whether females and
 males differed in size or flowering that may cause observation bias. We
 detected a strong and consistent female bias, both in natural populations
 (sex ratio [proportion of females]: 0.71-0.82) and in our controlled
 experiment (overall sex ratio: 0.70-0-72). Female bias became more
 pronounced with increasing elevation. Our data did not support sexual
 dimorphism in size or flowering. Family sex ratios varied largely (from
 0.25 to 1), including many female-biased families, unbiased families and
 two male-biased families. Families with lower germination, seedling
 establishment, survival or flowering did not have stronger female bias,
 indicating that intrinsically higher survival or flowering in females does
 not explain overall female bias.  Synthesis: Our results suggest
 that sex ratio bias in S. herbacea is already present in seeds and does
 not arise through intrinsic differences between sexes. Candidate
 mechanisms that can lead to both overall female bias and variation in sex
 ratio among families are meiotic drive or cyto-nuclear interactions. The
 pioneer habit of Salix may lead to non-equilibrium population dynamics
 that allow for the long-term persistence of variable genetic sex ratio
 distortion systems that arise from genetic conflict.
description: We investigated sex ratios in three natural populations over
 three years as well as in 29 crosses (full-sib families) under controlled
 conditions over four growth periods. We tested whether sex ratio was
 associated with habitat parameters (elevation and snowmelt time), or with
 germination, survival or flowering, and whether females and males differed
 in size or flowering that may cause observation bias.
 We re-analysed published data from three natural <em>S.
 herbacea</em> populations near Davos Switzerland, Jakobshorn (J),
 Schwarzhorn (S) and Wannengrat (W), at elevations from 2000 to 2800 m
 above sea level (Wheeler et al., 2016), supplemented by 116 unpublished
 records from the same study. In the controlled experiment, we generated 29
 hand-pollinated crosses in a natural alpine population of<em> S.
 herbacea </em>near Jakobshorn, Switzerland (46.7720N, 9.8554E, 2535
 m above sea level) between June and August 2020, and collected mature
 fruits 4-6 weeks after pollination.  A total of 1521 seeds from 29
 families were then cultivated under controlled conditions. We assessed
 plant sex by reproductive flowers for four growth periods and recorded bud
 break, leaf expansion and flowering every three days, counted the number
 of leaves and catkins and measured the length and width of two leaves per
 plant, as well as the length of the longest twig.
description: # Data from: Female-biased population sex ratios caused by genetic rather
 than ecological mechanisms in dwarf willow (*Salix herbacea* L.)
 [https://doi.org/10.5061/dryad.cnp5hqcd8](https://doi.org/10.5061/dryad.cnp5hqcd8) Authors: Xiaomeng Mao, Andres J. Cortés, Christian Rixen, Sophie Karrenberg This dataset contains all the data collected and analysed in the study. It includes two files: 1) data from the controlled experiments collected in this study (JEcol-2023-1073_controlled_measurements.csv), and 2) data of natural populations from a published dataset and unpublished records in Wheeler et al., 2016 (JEcol-2023-1073_natural_measurements.xlsx). #### JEcol-2023-1073\_controlled\_measurements.csv: Reproductive flowering, traits and growth data of *Salix herbacea* under controlled conditions. * *Tray* & *Position*: location identity  * *Family*, *ID* & *family_id*: individual identity * *Final_Sex*: sex identified by reproductive flower after four growth periods (Female, Male, non-flower or DIE) * *no_leaves_r4*: leaf number measured at the fourth growth period * *leave_size_r4*: leaf area (mm^2) defined as average leaf length * width, measured at the fourth growth period * leave_shape_r4: leaf shape defined as average leaf length/width, measured at the fourth growth period * no_Catkin_r4: catkin number measured at the fourth growth period  * *Longest_twig_r4*: the length of the longest twig measured at the fourth growth period (mm) * *L_r4*, *B_r4* and *flower_r4*: the days of leaf expansion, bud broken and flowering. Recorded every 3 days after the spring season started at the fourth growth period * *died_final*: whether the plant died after four growth periods (died or NA) * *died_final_new* and *died_final_old*: whether the plant died after the seedling establishment of the first growth period, whether the plant died before the seedling establishment of the first growth period (died or NA) * *ref*: flowering frequency in the last three growth periods ("a" or "NA" means flowering or not in the period 2_3_4) * *table_old*: the location before seedling establishment * *pollinated_rounds* & *sampling_r1*: whether the plant has been used for pollination or sampling in other projects #### JEcol-2023-1073\_natural\_measurements.xlsx: Reproductive flowering, traits and habitats data of *Salix herbacea* in natural populations. * *data*: data resources ("dryad", published data; "herm" and "pp", unpublished data. Both are derived from the study of Wheeler et al., 2016) * *pop*: population name * *ID* & *band* & *microhabitat* & *patch*: location identity of patch * *year*: collection year * *patch.sex*: the reproductive sex in the patch (female, male, both or NA) * *leaf.area*: leaf area (1e^-4 mm^2)  * *elevation*: the elevation above sea level (m) * *snowmelt*: snowmelt day of the year * *flowering*: whether it flowered or not (flowering or vegetative) * *fl_doy*: flowering day of the year ## Sharing/Access information Data on natural population was partially derived from the following sources: * Wheeler, Julia A. et al. (2017). Data from: The snow and the willows: earlier spring snowmelt reduces performance in the low-lying alpine shrub Salix herbacea [Dataset]. Dryad. [https://doi.org/10.5061/dryad.6js40](https://doi.org/10.5061/dryad.6js40)