Parental effort has a direct impact on individual fitness. Theoretical models exploring how parental effort evolves to cope with offspring demand and sexual conflicts may differ in the assumptions they make in respect to the genetic heritability of parental behaviours. Only a few attempts, however, have been made to estimate the heritability of parental behaviours and their possible co-evolutio...

1. With the aid of a novel survivorship model, an 8-year field study of social and maternal factors affecting duckling survival in eiders (Somateria mollissima) revealed that duckling survival probability varies in accordance with maternal brood-rearing strategy. This variability in survival provides compelling evidence of different annual fitness consequences between females that share brood-r...

Genome editing using the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and associated nuclease (Cas9) enables specific genetic modifications, including deletions, insertions, and substitutions in numerous organisms, such as the fruit fly Drosophila melanogaster One challenge of the CRISPR/Cas9 system can be the laborious and time-consuming screening required to find CRISPR-...

To understand the evolution of alternative reproductive strategies such as communal breeding, it is important to recognize the options open to individuals and to evaluate their consequences. The relative reproductive success of individuals taking each option is one of the most important of these consequences. Burying beetles, Nicrophorus, are an excellent model system for the investigation of r...

The mating behavior of captive Loligo bleekeri and the paternity of the resulting progeny were examined based on behavioral observations and genetic analyses. In this species, there are 3 mating behaviors (male-parallel, head-to-head, and extra-pair), and 2 sperm storage sites in females (seminal receptacle and the opening of the oviduct), which suggest that sperm competition occurs. All 3 mati...

Hamilton's haplodiploidy hypothesis suggests that the relatively higher relatedness of full sisters in haplodiploid populations promotes altruistic sib rearing and, consequently, the evolution of eusociality. This haplodiploidy effect works when some broods have a relatively female-biased sex ratio and other broods have a relatively male-biased sex ratio, termed split sex ratios. There is empir...

1. Sex-biased mortality in adult vertebrates is often attributed to lower immunocompetence and higher parasite susceptibility of males. Although sex-specific mortality has also been reported during growth, the importance of sex-specific immunocompetence and parasite susceptibility in explaining male-biased mortality remains ambiguous in growing individuals because of potentially confounding sou...

In cooperatively breeding birds multiple maternity and paternity of broods is not uncommon, reproduction often being shared among group members as well as with extragroup members. We investigated the extent of extrapair paternity and intraspecific brood parasitism in a population of cooperatively breeding long-tailed tits. Our aim was to determine the frequency and cause of mixed parentage and ...

In a previous study we showed that broods from the viviparous eelpout Zoarces viviparus were significantly male biased in 1998 in the vicinity of a large kraft pulp mill on the Swedish Baltic coast. One suggested hypothesis was that masculinizing compounds in the effluent were affecting gonadal differentiation of the embryos, resulting in skewed sex ratios. In this article, we present further e...

Genetic parentage analyses provide insights into mating systems and have revealed widespread evidence for polyandry in natural populations. Here, we use 5 microsatellite markers to estimate female mating rates in a feral population of green swordtails, Xiphophorus helleri, a live-bearing poeciliid fish that has become a model system in the study of precopulatory mate choice and mating competiti...