Ontogeny and sex alter the effect of predation on body shape in a livebearing fish: sexual dimorphism, parallelism, and costs of reproduction

Predation can cause morphological divergence among populations, while ontogeny and sex often determine much of morphological diversity among individuals. We used geometric morphometrics to characterize body shape in the livebearing fish Brachyrhaphis rhabdophora to test for interactions between these three major shape-determining factors. We assessed shape variation between juveniles and adults of both sexes, and among adults for populations from high- and low-predation areas. Shape differed significantly between predation regimes for all juveniles regardless of sex. As males grew and matured into adults, ontogenetic shape trajectories were parallel, thus maintaining shape differences in adult males between predation environments. However, shape of adult females between predation environments followed a different pattern. As females grew and matured, ontogenetic shape trajectories converged so that shape differences were less pronounced between mature females in predator and nonpredator environments. Convergence in female body shape may indicate a trade-off between optimal shape for predator evasion versus shape required for the livebearing mode of reproduction.     

Ecological disjunction across the sexes in an alloparasitoid: Host requirements,sex ratios and mate localization (Hymenoptera: Aphelinidae)

The larval females of Coccophagus sp. nr gurneyi Compere are primary parasitoids of lantana mealybugs, whereas males develop hyperparasitically through other parasitoids (never their own females), so the species is alloparasitic. Males are seldom even reared from lantana mealybugs (<0.3%, n = 4,212), and have not yet been reared from any other host. Adults were sampled in the field to establish that this species is sexual (by assessing female spermathecal content), and to quantify relative abundance of the sexes around host infestations. Adult males were scarce above hosts (3%, n = 314), but were attracted in relatively high numbers to caged virgin females within those infestations. Caged females outside infestations did not attract males, suggesting that mate attraction requires environmental signals other than those from females. Most females collected in the field above host infestations had sperm in their spermathecal capsules. They presumably had mated with males that developed elsewhere (so mate localization might involve searching across substantial distances). Virgin females were present only early in the day and evidently mate soon after eclosion. Evidence of sperm depletion in mated females was not found. The spatial scale of male and female movements needs to be quantified, but the ongoing movement of individuals (as a consequence of their sex‐related host relationships) seems to be a regular aspect of their ecology. The spatial and temporal dynamics across the sexes illustrates that their abilities to localize one another for mating leaves the sexes free to diverge ecologically, and their sex ratios to vary.     

Ecological context of breeding system variation: sex, size and pollination in a (predominantly) gynodioecious shrub

BACKGROUND AND AIMS: Species that exhibit among-population variation in breeding system are particularly suitable to study the importance of the ecological context for the stability and evolution of gender polymorphism. Geographical variation in breeding system and sex ratio of Daphne laureola (Thymelaeaceae) was examined and their association with environmental conditions, plant and floral display sizes, and pollination environment in a broad geographic scale was analysed. METHODS: The proportion of female and hermaphrodite individuals in 38 populations within the Iberian Peninsula was scored. Average local temperature and precipitation from these sites were obtained from interpolation models based on 30 years of data. Pollination success was estimated as stigmatic pollen loads, pollen tubes per ovule and the proportion of unfertilized flowers per individual in a sub-set of hermaphroditic and gynodioecious populations. KEY RESULTS: Daphne laureola is predominantly gynodioecious, but hermaphroditic populations were found in northeastern and southwestern regions, characterized by higher temperatures and lower annual precipitation. In the gynodioecious populations, female plants were larger and bore more flowers than hermaphrodites. However, due to their lower pollination success, females did not consistently produce more seeds than hermaphrodites, which tends to negate a seed production advantage in D. laureola females. In the northeastern hermaphroditic populations, plants were smaller and produced 9-13 times fewer flowers than in the other Iberian regions, and thus presumably had a lower level of geitonogamous self-fertilization. However, in a few southern populations hermaphroditism was not associated with small plant size and low flower production. CONCLUSIONS: The findings highlight that different mechanisms, including abiotic conditions and pollinator service, may account for breeding system variation within a species' distribution range and also suggest that geitonogamy may affect plant breeding system evolution.