Seasonal niche partitioning and coexistence of amphimictic and parthenogenetic lineages of Heterocypris barbara (Crustacea: Ostracoda)

Abstract

Sympatry of amphimictic and parthenogenetic lineages in species with mixed reproductive systems is rarely observed in nature. On Lampedusa Island (Pelagie Islands, Italy), amphimictic and parthenogenetic lineages of Heterocypris barbara (Gauthier and Brehm, 1928) co-occur in a temporary pond. Their sympatric persistence calls for an ecological differentiation. We investigated the role of seasonal variation of temperature and photoperiod conditions by two different approaches: microcosms set up by inundation of dry sediments from the temporary pond and life-table experiments. Microcosms recreate conditions similar to the field and in their sediments random samples of resting eggs of both amphimictic and parthenogenetic females are stored. Life-table experiments supplied individual-based estimates of survivorship, adult life span, fecundity, and sex ratio in the progeny. We carried out the experiments at 24 °C and a photoperiod of 12 h light (L) : 12 h dark (D) (simulating fall conditions) and at 16 °C and a photoperiod of 10 h L : 14 h D (simulating winter conditions). Males and amphimictic females were the most numerous forms at 24 °C and 12 h L : 12 h D; parthenogenetic females were dominant at 16 °C and 10 h L : 14 h D. Life-table experiments showed that amphimictic forms do not complete development at 16 °C and 10 h L : 14 h D. Our results suggest that sympatry of amphimictic and parthenogenetic females in the field depends on seasonal niche partitioning and the storage effect of resting eggs that allows survival through adverse-season conditions.

Adaptations to different habitats in sexual and asexual populations of parasitoid wasps: a meta-analysis

“…Our results strongly suggest that ecological differentiation may be a cornerstone to coexistence of the sexuals and asexuals forms in Venturia canescens . Our conclusion is congruent with previous studies reporting, in several taxa, differences in habitat preferences and in responses to environmental conditions between closely related sexual and asexual strains: in plants (dandelions, Meirmans, Meirmans & Kirkendall, 2012 ), insects (aphids, Simon, Rispe & Sunnucks, 2002 ; Gilabert et al, 2014 ), crustaceans ( Rossi et al, 2017 ) and fish ( Schenck & Vrijenhoek, 1986 ). Nevertheless, to firmly conclude about the involvement of ecological differentiation on coexistence of both reproductive modes in V. canescens , further investigations are needed to experimentally test, as done by Lehto & Haag (2010) in Daphnia pulex , whether the relative fitness of the sexual and asexual wasps depends on ecological conditions, that is, whether sexuals outperform asexuals in the field and asexuals outperform sexuals in building conditions.…”

Assessing the Extinction Risk of Heterocypris incongruens (Crustacea: Ostracoda) in Climate Change with Sensitivity and Uncertainty Analysis

“…Moreover, under climate change conditions, variations in rainfall patterns, temperature and evaporation increase, are expected to increase conductivity levels [36,64,82]. In Heterocypris, high conductivity delayed hatching of resting eggs from an egg bank [83]. In contrast to an increase of temperature, increasing of conductivity levels may reduce the hatching rate and the depletion of the egg bank or may reduce growth rates and fecundity of freshwater invertebrates [36].…”

Differential genotype response to increased resource abundance helps explain parallel evolution of Daphnia populations in the wild

“…Carvalho and Crisp (1987) demonstrated that five of the dominant genotypes in their system were seasonal specialists, favored in summer, fall, or winter, and that this pattern was consistent across multiple locations within a lake and across multiple years. In ostracods, this seasonal resource partitioning is thought to allow for coexistence among lineages (Rossi et al, 2017). There are a vast number of seasonally changing variables that could be responsible for the seasonal turnover of genotypes, with resource availability being just one possibility.…”