Phenotypic plasticity in sex allocation for a simultaneously hermaphroditic coral reef fish

Abstract

Phenotypic plasticity can facilitate reproductive strategies that maximize mating success in variable environments and lead to differences in sex allocation among populations. For simultaneous hermaphrodites with sperm competition, including Serranus tortugarum a small coral reef fish, proportional male allocation (testis in total gonad) is often greater where local density or mating group size is higher. We tested whether S. tortugarum reduced male allocation when transplanted from a higher density site to a lower density site. After 4 months, transplants mirrored the sex-allocation patterns of the resident population on their new reef. Transplants had significantly lower male allocation than representatives from their source population, largely as a result of reduced testis mass relative to body size.

Does the cost of a function affect its degree of plasticity? A test on plastic sex allocation in three closely related species of hermaphrodites

“…Empirical tests of these predictions often investigated the effect of the social group, rather than that of the mating group, because the latter is difficult to manipulate. By varying the size of the social group, itwas often found that adult hermaphrodites make plastic adjustments of their sex allocation as they sense a change in their social group, i.e., in mating opportunities (Brauer et al, 2007;Hart et al, 2011;Lorenzi et al, 2005). However, the way hermaphrodites adjust their sex allocation to mating opportunities varies widely among species.…”

Self-fertilization, sex allocation and spermatogenesis kinetics in the hypodermically-inseminating flatworm Macrostomum pusillum

“…The evolution of sex allocation in simultaneous hermaphrodites is considered to have been largely shaped by sperm competition (Charnov, 1979(Charnov, , 1982(Charnov, , 1996. As has been demonstrated in a variety of species, hermaphrodites respond to higher levels of sperm competition by shifting their reproductive investment more towards the male function in order to increase their chances in reproduction over their competitors (Schärer and Ladurner, 2003;Tan et al, 2004;Hart et al, 2011;but see Baeza, 2007).…”

Do stable environments select against phenotypic plasticity in hermaphroditic sex allocation?

“…As a consequence, hermaphrodites should be selected to adjust their sex allocation plastically and opportunistically in response to the mating opportunities they are facing. By adjusting their sex allocation to these mating opportunities, hermaphrodites have more chances to produce offspring through the potentially more rewarding sex function (the preferred sex role) (Leonard 2005(Leonard , 2006Anthes et al 2006Anthes et al , 2010Schärer 2009;Di Bona et al 2010;Hart et al 2011). The evolution of plastic sex allocation in hermaphrodites is a key subject in sex allocation theory, but empirical tests are rare, as far as we know.…”

“…Generally, hermaphrodites are expected to live at low densities and meet their mates rarely (Ghiselin 1969;Westheide 1984;Sella & Ramella 1999;Puurtinen & Kaitala 2002). However, many species exhibit some degree of plasticity in sex allocation (e.g., Tan et al 2004;Baeza 2007;Brauer et al 2007;Schleicherova et al 2010;Hart et al 2011;Hoch & Levinton 2012). This suggests that the opportunities for mating fluctuate in the wild.…”