Experimental evolution of resource allocation in a simultaneously hermaphroditic freshwater snail: preliminary results

NICOLÁS BONEL; KEVIN SARTORI; ELODIE CHAPUIS; TIM JANICKE; VIOLETTE SARDA; PHILIPPE JARNE; PATRICE DAVID

Bielefeld

Workshop; Simultaneously Hermaphroditic Organisms Workshop; 2016

Universität Bielefeld, Faculty of Biology, Evolutionary Biology

The sex allocation theory in hermaphrodites deals with fitness optimization in the presence of tradeoffs between male and female functions under different environmental and social conditions. We sought to determine the evolutionary changes of reproductive investment in the male and female sex functions, and in their fitness, in the hermaphrodite snail Physa acuta (Basommatophora). We used experimental evolution lines (38th generation) in which selection was relaxed on one gender by manipulating female or male fitness and mating group size??female-biased (F lines) and male-biased (M lines) were compared to control lines. Each line included two populations (sub-lines). The experiment comprised 450 pigmented individuals (focals) equally distributed among lines and populations; 450 albino snails served as mating partners to estimate male investment and fitness of focals. We assessed female fecundity rate (female investment), survival rate of offspring (female fitness), time spent in male position when copulating (male investment), and paternity rate (male fitness). Preliminary results indicated that relaxing selection in female function (M lines) led to high male investment and fitness as expected from sex allocation theory. Relaxing selection in the male function (F lines) led to high female investment but, counter to theory, female fitness was low. These results suggest that there was a positive evolutionary change in reproductive investment and fitness towards male function in M lines. The result for female fitness could be due to suppressed sexual selection in F lines in which individuals might have accumulated deleterious mutations, decreasing fitness in the function selected. This supports the idea that sexual selection on the male function contribute to purge the genome from deleterious mutations.