Haplodiploid Hymenoptera females control the sex of their progeny, and their sex allocation is influenced by several factors. The impact of intra- and interspecific competition and of inbreeding and outbreeding on sex allocation has been studied in some species of the egg parasitoid Trichogramma. The pre-mating dispersion has also been studied. Impact of competition on sex allocation was observed for Trichogramma minutum Riley and Trichogramma pintoi Voegele. These species were chosen because of the ease with which than can be distinguish. Results show that females of both species lay more males under intraspecific competition than alone, following the Local Mate Competition theory, while only T. pintoi modifies its sex ratio under interspecific competition. Multiparasitism and natural habitat could explain this shift in the sex ratio. Trichogramma minutum, T. pintoi and Trichogramma evanescens Westwood pre-mating dispersion show that most matings occur at the emergence site. However, the three species have a potential for off-patch mating, allowing genetic exchange between sub-populations. These three species were chosen because they are classified in different groups in the genus. Finally, T. evanescens did not modify its sex ratio following inbreeding or outbreeding. The incapacity to discriminate between kin and non-kin, insufficient genetic distance in outbreeding, or the population structure could explain these results.

Thesis (M.Sc.). / Written for the Dept. of Natural Resource Sciences, Macdonald College of McGill University. Title from title page of PDF (viewed 2008/07/28). Includes bibliographical references.

No description available.

Thesis (Ph. D.)--Michigan State University. Dept. of Zoology, Program in Ecology, Evolutionary Biology, and Behavior, 2008. / Title from PDF t.p. (viewed Aug. 19, 2009). Includes bibliographical references (p. 88-95). Also issued in print.

Fitness components of small and large males (emerging respectively from small and large hosts) of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) were compared in laboratory experiments. These components were the longevity, courtship, mate competition, and daily and lifetime fertilization. Small males were less fit than large males: they had a reduced longevity, took longer to induce female mating behavior, rarely succeeded in mating females when in competition with large males and had lower fertilization capacity; female fertilized by small males oviposited in the first two days of their life only one third of the progeny of daughters mated by large males. The impact of males fitness on optimal sex allocation by females parasitoids was evaluated by measuring the primary and tertiary sex ratios (proportion of males in the progeny) produced by a female T. evanescens when ovipositing in small and large hosts (low and high quality patches). Females of T. evanescens, an arrhenotokous species, have control on the sex ratio of their offspring by regulation of the sperm's access to the egg. Certain combinations of male and female eggs deposited in a host patch result in greater fitness than others. As predicted, females produced a significantly higher proportion of males on the low quality patches. T. evanescens females adjusted the sex ratio allocated to a patch of homogeneous quality and under complete local mate competition to the expected fitness of their sons, as smaller males have a lower fitness and are expected to have low fertilization capacity and therefore fertilize less females. To optimize her fitness gain (the capacity of the individual to transmit its genes), the sex ratio is increased in order to have all daughters mated.

Thesis (Ph. D.)--Australian National University, 2003. / Title from PDF title page (viewed May 12, 2005). Includes bibliographical references.

The behaviour of sex allocation has been extensively studied in hymenopterans (ants, bees and wasps) as an adaptive trait with respect to intra-specific competition within the framework of kin selection theory. Mating in these organisms often takes place in patchy populations established by the offspring of a few foundresses. Typically, there is a bias in favour of female dispersal from these patches. Theory predicts that foundresses that oviposit alone will do best to produce just enough sons to mate all of their daughters so as to maximize the number of dispersing daughters, under conditions of what is referred to as Local Mate Competition (LMC) between brothers to mate their sisters. If foundresses co-found a patch with other foundresses, they are expected to invest more resources in sons insofar as opportunity to sire offspring with the daughters of the other foundresses presents itself. Among organisms with such a life histories are fig wasps, the insects that pollinate and lay their eggs in the flowers that grow inside young figs. There is thought to be strong selective pressure for foundresses to use information about clutch size differences in species where clutch sizes are small and low foundress numbers are frequently encountered. However, less rigorous modes of sex allocation are thought to suffice in species encountering intermediate foundress numbers. Theory thus predicts a positive relationship between the degree of structure within mating populations and the information utilized by foundresses with respect to intra-specific competition for resources and mating opportunities. This is being extensively tested across the diverse species range of fig wasps and their hosts with the larger objective in mind of contributing to a better understanding of the role of natural selection in accounting for variation observed of intra-specific behaviour. This dissertation reports on a study of the sex allocation behaviour of the pollinating fig wasp Platyscapa awekei, a species characterized by low foundress numbers and clutch size differences brought about by foundress competition over oviposition sites. Offspring collected from experimentally controlled twofoundress broods were fingerprinted using microsatellite genetic markers to assign maternity and work out clutch size differences. These data are used to test what information foundresses use when allocating sex. It is reported that foundresses appear to use information of clutch size differences in two foundress broods. This observation provides evidence of advanced information utilization in fig wasps. More generally, the findings add support to the hypothesis that natural selection can bring about subtle adaptive behaviour at the individual level, but simultaneously highlights the importance of accounting for the selective regime of the organism being studied when attempting to understand the role of natural selection in the evolution of fine scale adaptive traits. / Dissertation (MSc)--University of Pretoria, 2011. / Genetics / unrestricted

No description available.

<p>This thesis focuses on reproduction in a simultaneous hermaphrodite with internal fertilization; the nudibranch <i>Aeolidiella glauca</i>. Unlike most other nudibranchs, where copulation is the rule, <i>A</i>. <i>glauca</i> was found to transfer sperm via external spermatophores that were attached to the partner's back. Despite elaborate courtship the actual spermatophore transfer, which always involved two animals only, was of short duration. In most matings (88%) spermatophores were reciprocally exchanged. </p><p><i>A. glauca</i> was further found to be very promiscuous. During mating and sperm transfer the receiver exerts considerable control over sperm, and manipulative behaviours designed to increase the donor's reproductive success are thus likely to have evolved. An example of such manipulative behaviour may be <i>A. glauca's</i><b> </b>unique spermatophore avoidance behaviour. I found that slugs carrying a sign of previous mating activity, i.e. a spermatophore, were discriminated against in a situation where mate choice was possible. The presence of spermatophores was further found to reduce slugs' ability to interrupt matings, and displace other slugs. Body size, however, had no direct effect on displacement in <i>A. glauca</i> as small slugs interrupted matings as successfully as large ones. Furthermore, pair formation and mating were found to be random with respect to size. This was true also for pairs formed in the field. </p><p>In addition to mate choice hermaphrodites may increase their reproductive success by differential sex allocation. I tested whether differing mate encounter rates had any effects on allocation to male and female function in <i>A. glauca</i>. Slugs with more mating opportunities mated more, and had higher proportional spermatophore production that others. As predicted they also laid significantly fewer eggs than slugs presented with partners less often.</p>

This thesis focuses on reproduction in a simultaneous hermaphrodite with internal fertilization; the nudibranch Aeolidiella glauca. Unlike most other nudibranchs, where copulation is the rule, A. glauca was found to transfer sperm via external spermatophores that were attached to the partner's back. Despite elaborate courtship the actual spermatophore transfer, which always involved two animals only, was of short duration. In most matings (88%) spermatophores were reciprocally exchanged. A. glauca was further found to be very promiscuous. During mating and sperm transfer the receiver exerts considerable control over sperm, and manipulative behaviours designed to increase the donor's reproductive success are thus likely to have evolved. An example of such manipulative behaviour may be A. glauca's<b> </b>unique spermatophore avoidance behaviour. I found that slugs carrying a sign of previous mating activity, i.e. a spermatophore, were discriminated against in a situation where mate choice was possible. The presence of spermatophores was further found to reduce slugs' ability to interrupt matings, and displace other slugs. Body size, however, had no direct effect on displacement in A. glauca as small slugs interrupted matings as successfully as large ones. Furthermore, pair formation and mating were found to be random with respect to size. This was true also for pairs formed in the field. In addition to mate choice hermaphrodites may increase their reproductive success by differential sex allocation. I tested whether differing mate encounter rates had any effects on allocation to male and female function in A. glauca. Slugs with more mating opportunities mated more, and had higher proportional spermatophore production that others. As predicted they also laid significantly fewer eggs than slugs presented with partners less often.