Data from: Female-biased population sex ratios caused by genetic rather than ecological mechanisms in dwarf willow (Salix herbacea L.)
Data files
May 30, 2024 version files 240.44 KB
Abstract
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.
README: 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
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
Methods
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 S. herbacea 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 S. herbacea 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.