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
Language
Keywords
Cordylochernes scorpioides , maternal inheritance , mitochondrial haplotype , polyandry , sexually antagonistic selection , sperm competition
Alternative Title
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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