Delayed selfing and resource reallocations in relation to mate availability in the freshwater snail Physa acuta.
We study the influence of mate availability on the mating behavior of the self-fertile, preferentially outcrossing freshwater snail Physa acuta. Previous optimization theory indicated that mating system interacts with life-history traits to influence the age at first reproduction, providing three testable predictions. First, isolated individuals should reproduce later than individuals with available mates in the expectancy of finding a partner and avoiding the cost of inbreeding. Second, resource reallocation to future fecundity is needed for such reproductive delays to evolve. Third, the reproductive delay can be optimized with respect to life-history traits (e.g., survival, growth) and the mating system (inbreeding depression). Our results largely validate these predictions. First, reproduction is significantly delayed in isolated individuals ("selfers") as compared with individuals frequently exposed to mates ("outcrossers"). Second, delayed reproduction is associated with reallocation to future growth, survival, and fecundity, although fecundity is also affected by the mating system (selfing vs. outcrossing). Third, the reproductive delay found (approximately 2 wk) is consistent with quantitative predictions from optimization models. The delay is largely heritable, which might be partly explained by among-family differences in the amount of inbreeding depression (mating system) but not growth or survival.
Unité Mixte de Recherche, Diversité et Gènome des Plantes Cultivées, Institut National de la Recherche Agronomique, Domaine de Melgueil, F34130 Mauguio, France. tsitrone@ensam.inra.fr
Anne
A
Tsitrone
Philippe
P
Jarne
Patrice
P
David
D000818:Animals; D005075:Biological Evolution; D005602:France; D005618:Fresh Water; D007178:Inbreeding; D008954:Models, Biological; D011157:Population Dynamics; D012098:Reproduction / Q000502:physiology; D012726:Sexual Behavior, Animal / Q000502:physiology*; D012908:Snails / Q000502:physiology*; D013997:Time Factors