Effects of polyploidy and reproductive mode on life history trait expression

Abstract

Ploidy elevation is increasingly recognized as a common and important source of genomic variation. Even so, the consequences and biological significance of polyploidy remain unclear, especially in animals. Here, our goal was to identify potential life history costs and benefits of polyploidy by conducting a large multiyear common garden experiment in Potamopyrgus antipodarum, a New Zealand freshwater snail that is a model system for the study of ploidy variation, sexual reproduction, host–parasite coevolution, and invasion ecology. Sexual diploid and asexual triploid and tetraploid P. antipodarum frequently coexist, allowing for powerful direct comparisons across ploidy levels and reproductive modes. Asexual reproduction and polyploidy are very often associated in animals, allowing us to also use these comparisons to address the maintenance of sex, itself one of the most important unresolved questions in evolutionary biology. Our study revealed that sexual diploid P. antipodarum grow and mature substantially more slowly than their asexual polyploid counterparts. We detected a strong negative correlation between the rate of growth and age at reproductive maturity, suggesting that the relatively early maturation of asexual polyploid P. antipodarum is driven by relatively rapid growth. The absence of evidence for life history differences between triploid and tetraploid asexuals indicates that ploidy elevation is unlikely to underlie the differences in trait values that we detected between sexual and asexual snails. Finally, we found that sexual P. antipodarum did not experience discernable phenotypic variance‐related benefits of sex and were more likely to die before achieving reproductive maturity than the asexuals. Taken together, these results suggest that under benign conditions, polyploidy does not impose obvious life history costs in P. antipodarum and that sexual P. antipodarum persist despite substantial life history disadvantages relative to their asexual counterparts.

Embryonic ontogeny of three species of Horned Frogs, with a review of early development in Ceratophryidae

“…Polyploidy is an important evolutionary phenomenon that causes the whole‐genome multiplication and a consequent genomic redundancy. Both higher and lower growth rates are expected in polyploid species, based on a positive correlation with the major RNA content, and a slower metabolic rate and longer cell cycle duration, respectively (Larkin, Tucci, & Neiman, ; Otto, ). In a large‐scale study of evolution of genome size in amphibians, Liedtke, Gower, Wilkinson, and Gomez‐Mestre () found that more rapid growth rates are associated with smaller genomes.…”

Parasite resistance predicts fitness better than fecundity in a natural population of the freshwater snailPotamopyrgus antipodarum

“…In laboratory conditions, the snails reach maturity in 4–12 months (Winterbourn ; Larkin et al. ). In natural populations, juveniles born in the spring may reach maturity in late summer, and before the next summer season, if born later in the season.…”

Population genomics and geographical parthenogenesis in Japanese harvestmen (Opiliones, Sclerosomatidae, Leiobunum)

“…The origins and reproductive mode of a species provide critical information to workers concerned with the systematics or conservation of populations (Dejaco, Gassner, Arthofer, Schlick‐Steiner, & Steiner, ) or recommending areas for protection. Genomic innovations such as duplication (often the prelude to asexual reproduction; Larkin, Tucci, & Neiman, ) may play a role in the construction of complex genomes (Berthelot et al., ; Campbell, Ganley, Gabaldón, & Cox, ; Glasauer & Neuhauss, ; Kellis, Birren, & Lander, ; Kenny et al., ), thus making these pathways of particular import toward understanding why some lineages are evolutionarily successful and others are not (Pandit, Pocock, & Kunin, ). Exploration of the habitats commonly inhabited by parthenogens may also yield predictions about the biotic and abiotic factors that favor transitions in reproductive mode (Tilquin & Kokko, ).…”

“…A number of hypotheses have been offered as to the mechanisms contributing to geographical parthenogenesis, including selection for the beneficial demographic effects of parthenogenesis (Cosendai, Wagner, Ladinig, Rosche, & Hörandl, ; Kearney, ), biotic influences (Verhoeven & Biere, ), and successive genetic bottlenecks (Haag & Ebert, ). Some of these hypotheses are in turn reliant upon the origins and developmental pathways leading to parthenogenesis (Hörandl, ): Asexual populations frequently show evidence of hybrid origin (Janko, Kotlík, & Ráb, ; Kearney, ) and/or polyploidization (Grismer et al., ; Larkin et al., ; Myers, Trewick, & Morgan‐Richards, ), and male‐vectored “contagious” parthenogenesis has also been described (Maccari, Amat, & Gómez, ; Tucker, Ackerman, Eads, Xu, & Lynch, ; Xu, Innes, Lynch, & Cristescu, ). In order to disentangle the underlying processes that lead to the particular distribution of a species, we must consider the environments it occupies and query genetic markers that provide multiple lines of historical information (Barrow, Bigelow, Phillips, & Lemmon, ; Jezkova et al., ).…”