Contrasting effects of large density changes on relative testes size in fluctuating populations of sympatric vole species

Klemme, Ines and Soulsbury, Carl D. and Henttonen, Heikki (2014) Contrasting effects of large density changes on relative testes size in fluctuating populations of sympatric vole species. Proceedings of the Royal Society B: Biological Sciences, 281 (1792). p. 20141291. ISSN 0962-8452

Full content URL: http://dx.doi.org/10.1098/rspb.2014.1291

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Contrasting effects of large density changes on relative testes size in fluctuating populations of sympatric vole species

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Item Type:Article
Item Status:Live Archive

Abstract

Across species, there is usually a positive relationship between sperm competition level and male reproductive effort on ejaculates, typically measured using relative testes size (RTS). Within populations, demographic and ecological processes may drastically alter the level of sperm competition and thus, potentially affect the evolution of testes size. Here, we use longitudinal records (across 38 years) from wild sympatric Fennoscandian populations of five species of voles to investigate whether RTS responds to natural fluctuations in population density, i.e. variation in sperm competition risk. We show that for some species RTS increases with density. However, our results also show that this relationship can be reversed in populations with large-scale between-year differences in density. Multiple mechanisms are suggested to explain the negative RTS–density relationship, including testes size response to density-dependent species interactions, an evolutionary response to sperm competition levels that is lagged when density fluctuations are over a certain threshold, or differing investment in pre- and post-copulatory competition at different densities. The results emphasize that our understanding of sperm competition in fluctuating environments is still very limited.

Keywords:Sperm competition, Population cycles, Density, Voles, Relative testes size, JCOpen
Subjects:D Veterinary Sciences, Agriculture and related subjects > D300 Animal Science
Divisions:College of Science > School of Life Sciences
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ID Code:14698
Deposited On:16 Aug 2014 12:25

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