Data from: What ecological factors favor parthenogenesis over sexual reproduction? A study on the facultatively parthenogenetic mayfly Alainites muticus in natural populations

Different reproductive modes are characterized by costs and benefits which
depend on ecological contexts. For example, sex can provide benefits under
complex biotic interactions, while its costs increase under mate
limitation. Furthermore, ecological contexts often vary along abiotic
gradients. Here, we study how these factors simultaneously influence the
frequency of sex in the facultatively parthenogenetic mayfly Alainites
muticus . We first verified that parthenogenesis translates into
female-biased population sex ratios. We then measured the density of
individuals (a proxy for mate limitation) and community diversity (biotic
interaction complexity) for 159 A. muticus populations covering a broad
altitudinal gradient and used structural equation modeling to investigate
their direct and indirect influences on sex ratios. We found no effect of
community diversity or altitude on sex ratios. Furthermore, even when
females can reproduce parthenogenetically, they generally reproduce
sexually, indicating that the benefits of sex exceed its costs in most
situations. Sex ratios only become female-biased under low population
densities, as expected if mate limitation was the main factor selecting
for parthenogenesis. Mate limitation might be widespread in mayflies
because of their short adult lifespan and limited dispersal, which can
generate strong selection for reproductive assurance and may provide a
stepping-stone towards obligate parthenogenesis.