Parents should vary their level of investment in sons and daughters in response to the fitness costs and benefits accrued through male and female offspring. I investigated brood sex ratio biases and parental provisioning behaviour in the brown thornbill, Acanthiza pusilla, a sexually dimorphic Australian passserine. Parents delivered more food to male-biased than female-biased broods. However, ...

The parasitoid wasp genus Achrysocharoides (Eulophidae) is unusual in that many of its species lay male and female eggs in single-sex clutches. The average clutch size of female broods is always greater than that of male broods, and in some species male clutch size is always one. We constructed models that predicted that severely egg-limited wasps should produce equal numbers of male and female...

caspian brown trout (salmo trutta caspius) is one of the economically valuable species in the caspian sea. artificial propagation and production of larvae are the main problems in the early culture of this species. the purpose of this paper is to study the effect of reproductive performance of female broods on opposition reproduction efficiency in caspian brown trout in the breeding season of 2...

For maternally transmitted microbes, a female-biased host sex ratio is of reproductive advantage. Here we found a strong female bias in a field population of the green lacewing, Mallada desjardinsi (Insecta; Neuroptera). This bias was attributed to the predominance of individuals harboring a maternally inherited male-killing bacterium that was phylogenetically closely related to the plant-patho...

In brood-caring species, family members are faced with a conflict over resource distribution. While parents are selected to adapt the amount of care according to their offspring's needs, offspring might be selected to demand more care than optimal for parents. Recent studies on birds have shown that the social network structure of offspring affects the amount of care and thus the fitness of fam...

1. Polyembryonic wasps provide dramatic examples of intra-specific developmental conflict. In these parasitoids, each egg proliferates into a clonal lineage of genetically identical larvae. If more than one egg is laid in a host (superparasitism), individuals of different clones may compete for food resources. 2. In the polyembryonic encyrtid Copidosoma koehleri , one larva per clone can differ...

Brood size and other life-history traits of females affect male investment in mating. Female Uca tetragonon, producing relatively small broods, were attracted to the burrows of males for underground mating (UM) while carrying eggs. Most UM females released larvae and ovulated new broods during the pairing, averaging 3.9 days. While a female was incubating one brood, another brood was developing...

Because elevated glucocorticoid levels can impair reproduction, populations or species that engage in particularly valuable reproductive attempts may down-regulate the glucocorticoid stress response during reproduction (the brood value hypothesis). It is not clear, however, whether individuals rapidly modulate glucocorticoid responses based on shifting cues about the likelihood of reproductive ...

We use microsatellite loci to detail the multiple paternity patterns in broods from 10 wild populations of the guppy (Poecilia reticulata) found in Northern Trinidad. The populations span two major drainages comprising the Caroni and the Oropouche, and include sites that are characterized by either high or low predation. Across the populations the frequency of multiple paternity is high with 95...

Why females mate with multiple males, particularly in socially monogamous species, is one of the central unanswered questions in sexual selection and behavioural ecology. Recent theory suggests that socially monogamous females may improve the genetic quality of their offspring by mating with extrapair males with whom they are more genetically dissimilar (relative to their social mates), because...