What Ecological Factors Favor Parthenogenesis over Sexual Reproduction? A Study on the Facultatively Parthenogenetic Mayfly Alainites muticus in Natural Populations

Abstract

Different reproductive modes are characterized by costs and benefits which often depend on ecological contexts. Benefits of sex are expected to increase under complex biotic interactions, whereas parthenogenesis can be beneficial for reproductive assurance when females are mate limited. Here, we study how different ecological contexts influence the frequency of sex or parthenogenesis in the facultatively parthenogenetic mayfly Alainites muticus. We first verified that high parthenogenetic frequencies translate into female-biased population sex ratios. We then measured the population sex ratio (a proxy for parthenogenetic capacities), density of individuals (mate limitation) and community diversity (biotic interaction complexity) for 159 A. muticus populations, 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 become female-biased in low population densities, as expected if mate limitation selects for parthenogenesis. Mate limitation might be widespread in mayflies because of their very short adult lifespan and limited dispersal, which can generate strong selection for reproductive assurance and may provide a steppingstone towards obligate parthenogenesis.

Sex ratio dynamic of the field population of the sugarcane rust mite Abacarus sacchari (Acari: Eriophyidae)

“…The landing in the early colonisation was very low and resulted in a sparse population; consequently, encounters among individual mites were low. In addition, the low proportion of males (less than 5%) within the airborne mites lowered the chance of encounters, which eventually lowered the level of chance of mating availability (Liegeois et al 2023). Arrhenotokous parthenogenesis combined with oedipal mating takes advantage in such a situation allowing a single female of eriophyid to start a new colony in a new habitat, even for the immature mites (McCulloch & Owen 2012;Filia et al 2015;Ding et al 2018).…”