Abstract
Understanding processes that govern and sustain biological diversity is a central goal of community ecology. Unisexual complexes, where reproduction depends on sperm from males of one or more bisexual host species, are rare and the processes driving their diversity and structure remain poorly understood. Unisexual Ambystoma salamanders produce distinct biotypes (‘genomotypes’) depending on which bisexual species they ‘steal’ sperm from. This reproductive mode should generate distinct assemblages depending on the locally available bisexual host species. Yet, how availability and relative abundance of multiple bisexual hosts influences composition and diversity of natural unisexual assemblages at local or regional scales remains unknown. We hypothesize that host identity most directly drives local assemblage composition, with host variation associated with increased beta and gamma diversity within unisexuals. We collected genetic samples from Ambystoma salamanders across Pelee Island, Ontario, Canada (2015–2022). Two host species were identified (A. texanum and A. laterale) with nine sites having a single host and one site having both. Unisexual assemblages were grouped into four clusters by similarity, with host identity being a key determinant. Gamma diversity increased as a result of distinct host-specific assemblages forming at different sites on the island (i.e., high beta diversity). Assemblage composition, but not diversity, was correlated with relative host abundance, which may reflect matching niche requirements between host and unisexual forms they produce. Our results demonstrate that diversity and structure of unisexual assemblages are clearly shaped by their host(s) and such systems may serve as models for studying how biotic interactions shape ecological communities.
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Acknowledgements
Nature Conservancy of Canada, Essex Region Conservation Authority, Ontario Parks, as well as J. Ambrose, J. DeMarco, and D. Kraus provided authorization to sample on their properties.
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Financial support for the work was provided by The Ontario Species at Risk Stewardship Fund (SAR-00109, SARSF_23_18_Dmurr2), the Species at Risk Research Fund of Ontario (RF_23_18_Trent6), and the Species at Risk Stewardship Program (103-20-TrentU1).
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EAB, JPB, DLM, and TJH conceived and designed the study. EAB and JPB conducted the genotyping work. EAB and TJH conducted fieldwork. JPB and CW provided advice on lab techniques. EAB analyzed the data and TJH collaborated on statistical analysis. EAB and TJH wrote the manuscript. All authors provided critical feedback and contributed to the final version of the manuscript.
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Communicated by Jean-François Le Galliard.
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Bare, E.A., Bogart, J.P., Wilson, C. et al. Diversity and composition of mixed-ploidy unisexual salamander assemblages reflect the key influence of host species. Oecologia 202, 807–818 (2023). https://doi.org/10.1007/s00442-023-05440-8
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DOI: https://doi.org/10.1007/s00442-023-05440-8