Sisters' curse: sexually antagonistic selection constrains the spread of a rare mitochondrial haplogroup
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Authors
Padua, Michael V.
Issue Date
2014
Type
Thesis
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Keywords
Cordylochernes scorpioides , maternal inheritance , mitochondrial haplotype , polyandry , sexually antagonistic selection , sperm competition
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Abstract
Females produce relatively few, large and costly eggs. By contrast, males produce large numbers of small and physiologically inexpensive sperm. This differential investment in gametes has long been identified as a force driving the evolution of divergent mating tactics in the sexes. In most species, anisogamy is also coupled with strict maternal inheritance of genetic elements in the cytoplasm, including DNA in cellular endosymbionts and mitochondria. Because males are an evolutionary dead end for mitochondria, mutations in the mitochondrial genome that are harmful or beneficial to males but not to females cannot respond directly to selection. Few studies have documented sex-specific selection acting on mitochondria, and its general evolutionary significance remains poorly understood. As a polyandrous, viviparous invertebrate with indirect sperm transfer, the pseudoscorpion, Cordylochernes scorpioides, possesses a suite of reproductive and behavioral traits that makes it ideally suited for investigating the effects of mtDNA variation on male adaptation and sexual selection. Mitochondrial genome sequencing and phylogenetic analyses have revealed the coexistence of two highly divergent mitochondrial haplogroups, Clades A and B2, in central Panamá. DNA profiling demonstrated that B2-haplogroup males enjoyed a significant sperm competitive advantage, siring 2.5 times as many offspring as A- haplogroup males in two-male sperm competition experiments. However, mtDNA variation also influenced female sexual receptivity on second mating, with B2-haplogroup females significantly less likely to accept sperm from a second male. Taken together, these findings suggest that, despite its highly advantageous effects on sperm competitive ability, the B2 haplogroup is constrained to low frequency in central Panamanian populations of C. ii scorpioides because of its negative consequences for females, in terms of reduced propensity for adaptive polyandrous behavior among females carrying B2 haplogroup mitochondria.
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In Copyright(All Rights Reserved)