Ancient androdioecy in the freshwater crustaceanEulimnadia

Abstract

Among the variety of reproductive mechanisms exhibited by living systems, one permutationandrodioecy (mixtures of males and hermaphrodites)-is distinguished by its rarity. Models of mating system evolution predict that androdioecy should be a brief stage between hermaphroditism and dioecy (separate males and females), or vice versa. Herein we report evidence of widespread and ancient androdioecy in crustaceans in the genus Eulimnadia, based on observations of over 33 000 shrimp from 36 locations from every continent except Antarctica. Using phylogenetic, biogeographical and palaeontological evidence, we infer that androdioecy in Eulimnadia has persisted for 24-180 million years and has been maintained through multiple speciation events. These results suggest that androdioecy is a highly successful aspect of the life history of these freshwater crustaceans, and has persisted for orders of magnitude longer than predicted by current models of this rare breeding system.

High lability of sexual system over 250 million years of evolution in morphologically conservative tadpole shrimps

“…As models to describe the evolution and maintenance of AD only predict its evolution under stringent conditions, AD has historically been considered an unstable, transitional sexual system between gonochorism and hermaphroditism (or vice versa) [12-14,23,24]. This view is borne out by the scarcity of AD in nature [12,17], although recent research in the branchiopod Eulimnadia has revealed an unexpected stability of androdioecy [25]. …”

Genetic variability and reproductive modalities in European populations ofTriops cancriformis(Crustacea, Branchiopoda, Notostraca)

“…in the crustacean Eulimnadia spp. and in the nematode Caenorhabditis elegans) and plants (Lloyd 1975;Sudhaus & Kiontke 1996;Pannell 2002;Weeks et al 2006). The hypothesis that androdioecy could represent an intermediate step between gonochorism and hermaphroditism has been put forward (Pannell 2002).…”

Spatial Niche Differentiation of Sympatric Branchiopoda in a Highly Unpredictable Ephemeral Pool

“…Since B. kugenumaensis and L. biformis are bisexual, a clumped distribution would facilitate the efficiency of finding mates and reduce the risk of Alee effect (Sarnelle and Knapp, 2004). On the other hand, the reproductive mechanism of E. braueriana is androdioecy (Weeks et al, 2006) with only few males in our case (<10% in a cohort with hermaphrodites dominant, Wan-Ping Huang, unpublished), may suffer less pressure of Alee effect, and reduce urgent need to aggregate together for mating. They should more likely be randomly distributed.…”

“…Weeks et al, 2006;Wan-Ping Huang, unpublished), and the laevicaudatan clam shrimp Lynceus biformis (Ishikawa, 1895), in Siangtian Pond, a highly unpredictable ephemeral pool in northern Taiwan, with a relatively short but widely varying inundation duration. We compared and analyzed the spatial distribution densities of these three taxa in both the horizontal and vertical axes.…”