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Female-biased sex ratio despite the absence of spatial and niche segregation between sexes in alpine populations of dioecious Salix lapponum (Salicaceae)

Abstract

Dioecious plants often exhibit deviations from expected 1:1 sex ratios. Genus Salix is a notable example of the female-biased sex ratio. Quite surprisingly, there are very few studies retesting observed bias patterns from the different parts of the species range. We have determined whether isolated subalpine populations of Salix lapponum exhibit a biased secondary sex ratio, measured the size of the plants, and tested the spatial and ecological correlations of the bias at fine and broad scales. Males were generally taller than females, suggesting that a different allocation of resources may occur in both sexes. Despite this, we found consistent female bias with females on average twice as common as males in most populations studied. No correlations of sex ratio with elevation as a proxy of environmental harshness and proportion of non-flowering individuals were found. Additionally, no differences in spatial sex segregation and microhabitat preferences were found between males and females at a fine scale within the studied populations. Our results suggest that the biased sex ratio in S. lapponum is not environment-dependent and probably originates during early stages of ontogenetic development (seeds).

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Acknowledgements

We are grateful to workers of the Krkonoše National Park administration, namely J. Zahradníková and D. Gluzová, for help with obtaining research permit and field work, respectively. L. Čáp helped with nitrogen analysis. We thank the anonymous reviewer for many useful comments on the manuscript. Field work was carried out under research permits no 8/2010, 112/2012 and 113/2012. MH, SHM, ZH & MD were supported by the project no. IGA PrF-2018-001 from the Internal Grant Agency of the Palacký University.

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MH, SHM and MD conceived the study. MH and SHM conducted field work and soil sample analyses. MD and MH performed data analyses. ZH determined the collected bryophytes. PH helped with soil sample analyses. MH wrote the first draft of the manuscript. All of the authors contributed to and approved the final manuscript.

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Correspondence to Michal Hroneš.

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Hroneš, M., Hrachová Macurová, S., Hradílek, Z. et al. Female-biased sex ratio despite the absence of spatial and niche segregation between sexes in alpine populations of dioecious Salix lapponum (Salicaceae). Alp Botany 129, 1–9 (2019). https://doi.org/10.1007/s00035-018-0213-6

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Keywords

  • Dioecy
  • Niche differentiation
  • Secondary sexual dimorphism
  • Sex ratio bias
  • Spatial sex segregation
  • Willow