Hybrid complexes are composed of organisms with multiple combinations of parental genomes (genomotypes) that interconnect through nets of crosses. Although several such complexes are well established without speciation or extinction, mechanisms shaping their dynamics remain poorly understood. In this study, we quantified the reproductive success of the allopolyploid Iberian fish Squalius alburnoides in experimental free-access and directional crosses involving the most common genomotypes. Specifically, we analysed the paternity of the offspring produced when females had free access to male genomotypes and quantified variations in egg allocation, fertilization rate, and offspring survival among crosses involving each male genomotype. The composition of the offspring produced from free-access crosses varied significantly from that expected from random mating, suggesting that offspring production and viability are not independent of parental male genomotype. Moreover, directional crosses producing the genomotype most commonly found in wild populations appeared to be the most successful, with females laying more eggs, and fertilization rate and offspring survival being the highest. These results suggest that reproductive dynamics plays a relevant role in structuring the genomotype composition of populations and opens a path to future research on the ecology and evolutionary biology of allopolyploids and their multiplicity of possible evolutionary pathways.

Brood-guarding (or the continual attendance at the nest by one parent) has been relatively little studied in altricial birds. Parental investment in brood-guarding is often highly variable within a species, and the study of such variability may contribute to the understanding of the functions and regulation of this behaviour and of the tradeoffs involved in the choice between attending the nest and leaving to forage. In some colonial birds, it has been found that early nesting pairs attend their chick for longer than later nesting counterparts, giving rise to the synchronisation hypothesis that suggests that early pairs prolong broodguarding in order to reduce the probability of nest predation by a dilution effect. In this paper, for the first time we test the prediction that burrow-nesting colonial birds subject to little predation pressure should not display a seasonal decline in brood-guarding duration. The growth assistance hypothesis suggests that brood-guarding may allow the provision of frequent small meals and the efficient use of energy by chicks with poor homeothermic capabilities, resulting in improved early chick-growth. Finally, the chick-protection hypothesis predicts that chicks in more exposed nests should be brood-guarded for longer. Data collected at two Cory's Shearwater Calonectris diomedea colonies situated in contrasting environments supported the synchronisation hypothesis, as there was no seasonal trend in brood-guarding duration. Contrary to the growth assistance hypothesis, chicks brood-guarded for longer periods did not have an improved growth (in one colony there was even a negative effect of brood-guarding on early chick development). Finally, we found no difference in brood-guarding between nests with contrasting levels of exposure to potential predators and weather. Despite confirming the prediction of the synchronisation hypothesis, more research is needed to identify the main factors underlying the variability of brood-guarding observed in this and other studies.

Previous studies have shown that assortative mating acts as a driver of speciation by countering hybridization between two populations of the same species (pre-zygotic isolation) or through mate choice among the hybrids (hybrid speciation). In both speciation types, assortative mating promotes speciation over a transient hybridization stage. We studied mate choice in a hybrid vertebrate complex, the allopolyploid fish Squalius alburnoides. This complex is composed by several genomotypes connected by an intricate reproductive dynamics. We developed a model that predicts the hybrid complex can persist when females exhibit particular mate choice patterns. Our model is able to reproduce the diversity of population dynamic outcomes found in nature, namely the dominance of the triploids and the dominance of the tetraploids, depending on female mate choice patterns and frequency of the parental species. Experimental mate choice trials showed that females exhibit the preferences predicted by the model. Thus, despite the known role of assortative mating in driving speciation, our findings suggest that certain mate choice patterns can instead hinder speciation and support the persistence of hybrids over time without speciation or extinction.

Kinship has been described as a major factor shaping primates' social dynamics, with individuals biasing their affiliative interactions to their related counterparts. However, it has also been demonstrated that, under certain circumstances, social bonding can be established in the absence of kin. The fact that Colobus polykomos (Western black-and-white colobus) and Procolobus badius temminckii (Temminck's red colobus) often live in sympatry (subject to the same ecological/anthropogenic pressures) but exhibit contrasting social systems, makes them good models to test which factors shape their social systems. We investigated the influence of kinship on intragroup social dynamics of one focal group of each species present in Cantanhez National Park, Guinea-Bissau. Between October 2008 and June 2009 we used focal sampling to collect information on the individuals' nearest neighbors and Ad libitum sampling to collect data on intra-group social interactions. We estimated pairwise relatedness using fecal DNA from nine Colobus polykomos individuals and 15 Procolobus badius temminckii individuals genotyped at 15 microsatellite loci. We found that, in the Colobus polykomos focal group, individuals showed no preference to interact or be spatially closer to related partners. Moreover, mainly unrelated females and related males composed the Procolobus badius temminckii focal group but grooming was most frequent among female dyads and only rarely involved male dyads. We conclude that kinship is not an important factor determining the social bonding in either study species suggesting that other factors (e.g anthropogenic, ecological) may be at play shaping these groups' social bonding.

Androgenesis among vertebrates is considered a rare phenomenon, with some cases reported so far, but linked to experiments involving gamete manipulation (artificial androgenesis). Herein, we report the first empirical evidence of the natural occurrence of spontaneous androgenesis in a vertebrate, the Squalius alburnoides allopolyploid complex. A genetically screened random sample of a natural population was allowed to reproduce in an isolated pond without any human interference, and the viable offspring obtained was later analysed for paternity. Both nuclear and mitochondrial markers showed that the only allodiploid fish found among all the allotriploid offspring was androgenetically produced by an allodiploid male. This specimen had no female nuclear genomic input, and the sequence of the mitochondrial fragment examined differed from that of the male progenitor, matching one of the parental females available in the pond, probably the mother. The possible role of androgenesis in the reproductive dynamics of this highly successful vertebrate complex is discussed.