Size Assortative Mating and Reproductive Success of the Funnel-Web Spider, Agelena limbata (Araneae; Agelenidae)

Field observations and laboratory experiments were conducted to assess the relation between male size and reproductive success in the funnel-web spider, Agelena limbata Thorell (Agelenidae), in 2 years. In this species, the body size of males is similar to that of females. In the field, size assortative mating occurred in both years. In 1 year, partial correlation coefficient analysis indicates that male cephalothorax width is a beter predictor of the copulated female cephalothorax width than of the date of pairing. In laboratory experiments, females tended to reject courting males that were smaller in relative body size, and males that were larger in relative body size had greater copulation success. Consequently female rejection of smaller courting males has some contribution to size assortative mating. Since larger females deposited more numerous eggs in the field, larger males are expected to have a higher reproductive success.     

Why do sperm-depleted parasitoid males continue to mate?

Insect males of several parasitoid species have limited amountof sperm at emergence and experience sperm depletion when mateacquisition rate is high, suggesting that sperm production andstorage could be a limiting factor for male's fitness. Sperm-depletedmales of the parasitoid wasp Trichogramma evanescens continueto mate, and the impact of this behavior on sperm storage byfemales has been studied. Virgin females T. evanescens stored50.6 ± 13.1 (Mean ± SD) sperm when mating firstwith a virgin male. However, when these females mated firstwith a sperm-depleted male and then with a virgin male, theystored only 18.9 ± 7.8 sperm, indicating that matingwith a sperm-depleted male has a cost and limits sperm acquisitionfrom fertile males. Following a mating with a sperm-depletedmale, females had to mate with three virgin males to restoretheir sperm supply confirming that additional mating enabledthe female to store a limited number of sperm. According toour results, by continuing to mate, sperm-depleted males donot prevent mates from copulating again but they decrease theirability to store other male's sperm. Continuing to mate couldbe a strategy to increase the relative fitness of sperm-depletedmales.     

Multiple Mating and Reproductive Success of Male and Female Apple Maggot Flies, Rhagoletis pomonella (Diptera: Tephritidae)

Mature male and female apple maggot flies mated frequently on a field-caged host tree during a 14-day study. Each sex averaged one mating per day (mean of 1.0 ± 0.1), but some females mated up to eight times per day and some males up to six times per day. Reproductive success was estimated based both on observed numbers of matings in the field cage and on previous work relating fecundity and fertility to female mating status. Male and female flies did not differ in mean or variance in reproductive success, indicating that this is a polygamous mating system consisting of both polygyny and polyandry. We discuss the significance of this with regard to the framework of insect mating control and frequency proposed by others. We also discuss behaviors (such as movements, agonistic encounters, occurrences on fruit, and ovipositions) that do and do not show correlations with mating success in apple maggot flies.     

Can the limited marsupium space be a limiting factor for Syngnathus abaster females? Insights from a population with size-assortative mating

1. Some syngnathid species show varying degrees of sex role reversal aside from male pregnancy, with females competing for access to mates and sometimes presenting conspicuous secondary sexual characters. Among other variables, brooding space constraints are usually considered a key element in female reproductive success, contributing strongly to the observed morphological and behavioural sexual differences. Nevertheless, a close relationship between sex role reversal and male brooding space limitation has not yet been accurately demonstrated in field studies. 2. The present work, conducted over two consecutive breeding seasons in a wild population of the sex role-reversed pipefish Syngnathus abaster, simultaneously analysed egg number and occupied space, as well as the free area in the male's marsupium. The number of eggs that would fit in the observed unoccupied space was estimated. 3. Contrary to what would be expected, given the marked sexual dimorphism observed in the population studied, where females were larger and more colourful, male brooding space did not appear to limit female reproduction as neither large nor small individuals presented a fully occupied pouch. Interestingly, the largest unoccupied areas of marsupium were found in the larger individuals, although they received more and larger eggs. Laboratory data also showed that larger females lay larger eggs. 4. Together, these results suggest the existence of assortative mating, which may result from: (i) the reluctance of larger males (which tend not to receive small eggs usually laid by small females) to mate with lower quality females, even at the expense of a smaller number of offspring; or (ii) female-female competition, which might strongly reduce the hypothesis of a small female mating with a large male. The potential impact of temperature on reproduction and population dynamics is also discussed in the light of ongoing climatic changes.     

Desiccation resistance and mating behaviour in laboratory populations of Drosophila simulans originating from the opposing slopes of Lower Nahal Oren (Israel)

Lower Nahal Oren in Northern Israel, often referred to as 'Evolution Canyon', has been proposed as a microscale model site for ecological evolution. However, conflicting stress resistance and mating assay results contribute to controversy over the Nahal Oren model. In this study, we further tested the Nahal Oren model, while extending its focus from Drosophila melanogaster to its sister species, Drosophila simulans. Using fly populations derived from the opposing canyon slopes and acclimated to laboratory conditions for 11-22 generations, we did not find a significant slope effect on desiccation resistance (P = 0.96) or body metabolic fuel content (P > 0.43), which would indicate a genetic basis for adaptation to local resource limitation. Multiple-choice mating assays (47-48% homotypic couples in two replicate populations) did not indicate divergence from a random mating pattern between north- and south-facing slope flies. In conclusion, our findings do not support divergence of D. simulans populations across Lower Nahal Oren.     

Are there costs in the repeated mating activities of female Southern stink bugs Nezara viridula?

Mating is an energy demanding process, imposing risks to physical injuries, pathogen infection and predation. Nevertheless, repeated and multiple mating are widespread even in insect species where nuptial gifts are not involved. The effects of repeated mating, by the same male, are examined on the reproductive performance of female Southern green stink bug Nezara viridula (L.). Fecundity is reduced in females mated three or four times, although there is increased longevity. Females mated once or twice produce more egg clusters and concentrate egg‐laying activity in the early part of adult life, whereas those mating more often lay eggs throughout the life span, with fewer egg clusters. Although fecundity is negatively affected by the number of matings, egg fertility remains unaffected.