Comparative Genomics Supports Ecologically Induced Selection as a Putative Driver of Banded Penguin Diversification.

The relative importance of genetic drift and local adaptation in facilitating speciation remains unclear. This is particularly true for seabirds, which can disperse over large geographic distances, providing opportunities for intermittent gene flow among distant colonies that span the temperature and salinity gradients of the oceans. Here, we delve into the genomic basis of adaptation and speciation of banded penguins, Galápagos (Spheniscus mendiculus), Humboldt (Spheniscus humboldti), Magellanic (Spheniscus magellanicus), and African penguins (Spheniscus demersus), by analyzing 114 genomes from the main 16 breeding colonies. We aim to identify the molecular mechanism and genomic adaptive traits that have facilitated their diversifications. Through positive selection and gene family expansion analyses, we identified candidate genes that may be related to reproductive isolation processes mediated by ecological thermal niche divergence. We recover signals of positive selection on key loci associated with spermatogenesis, especially during the recent peripatric divergence of the Galápagos penguin from the Humboldt penguin. High temperatures in tropical habitats may have favored selection on loci associated with spermatogenesis to maintain sperm viability, leading to reproductive isolation among young species. Our results suggest that genome-wide selection on loci associated with molecular pathways that underpin thermoregulation, osmoregulation, hypoxia, and social behavior appears to have been crucial in local adaptation of banded penguins. Overall, these results contribute to our understanding of how the complexity of biotic, but especially abiotic, factors, along with the high dispersal capabilities of these marine species, may promote both neutral and adaptive lineage divergence even in the presence of gene flow.

Nest-type associated microclimatic conditions as potential drivers of ectoparasite infestations in African penguin nests.

Nest design and characteristics can influence the microclimatic conditions in the nest. Nest-dwelling ectoparasites are sensitive to temperature and moisture and as such the conditions in the nest can influence parasite infestations. The endangered African penguin (Spheniscus demersus) breeds in different nest types and as yet little is known with regard to the microclimate and parasite infestation within these nests. This study characterized the microclimatic conditions in natural open, natural covered (with vegetation) and artificial nests, and assessed the relationship between nest characteristics (type, age, distance from the coast, orientation and entrance opening) and in-nest ectoparasite infestations and the health of African penguins in Stony Point, South Africa. Penguins (50 adults and 192 chicks) and their nests (n = 308) were sampled in 2016 and 2017. Soil temperature was higher in artificial than in natural nests, and soil and nest material moisture was lower in artificial and natural covered nests than natural open. Ectoparasite infestations were higher under warmer and drier conditions, in artificial nests and nests near the coastline. Penguin (adult and chick) body mass and chick body condition were lower in warmer nests and total plasma protein (in adults and checks) was lower in drier nests. Given the potential adverse effects of ectoparasites on host species, it is recommended that conservation agencies implement a monitoring programme to assess the ectoparasite infestation in artificial nests across multiple colonies. This information will facilitate a more holistic penguin conservation management plan that may prevent further detrimental effects on this endangered penguin species.

Parasite diversity associated with African penguins (Spheniscus demersus) and the effect of host and environmental factors.

The African penguin (Spheniscus demersus) is a critically endangered species endemic to southern Africa. Limited information is available on the parasite diversity associated with the species in natural settings. This study explores the diversity and incidence of parasites associated with African penguins and their nests, and records the effect of host and environmental factors on parasite infestation. Ecto-, haemo- and helminth parasites were recorded from 210 adult birds, 583 chicks and 628 nests across five colonies (two mainland and three islands) along the south-western coast of South Africa, in 2016 and 2017. Mean nest density (total and active nests) and climate variables (temperature and precipitation) were obtained for each colony. Parapsyllus humboldti was the most abundant and prevalent ectoparasite on penguins and in nests (69.10 and 57.80%, respectively), while Piroplasmorida/Haemospororida (33.51%) and Cardiocephaloides spp. (56.17%) were the most prevalent haemo- and helminth parasites of penguins, respectively. In general parasite abundance and prevalence was significantly affected by penguin age (chicks vs adults), location (mainland vs islands), nest density (total and active nests) and season (spring vs autumn/winter). It is concluded that parasite infestations are structured and that penguin chicks at mainland colonies are more susceptible to parasite infestations during spring.

Analysis of large new South African dataset using two host-specificity indices shows generalism in both adult and larval ticks of mammals.

Ticks and tick-borne pathogens can have considerable impacts on the health of livestock, wildlife and people. Knowledge of tick-host preferences is necessary for both tick and pathogen control. Ticks were historically considered as specialist parasites, but the range of sampled host species has been limited, infestation intensity has not been included in prior analyses, and phylogenetic distances between hosts have not been previously considered. We used a large dataset of 35 604 individual collections and two host-specificity indices to assess the specificity of 61 South African tick species, as well as distinctions between adult and juvenile ticks, for 95 mammalian hosts. When accounting for host phylogeny, most adult and juvenile ticks behaved as generalists, with juveniles being significantly more generalist than adults. When we included the intensity of tick infestation, ticks exhibited a wider diversity of specificity in all life stages. Our results show that ticks of mammals in South Africa tend to behave largely as generalists and that adult ticks are more host-specific. More generally, our analysis shows that the incorporation of life-stage differences, infestation intensity and phylogenetic distances between hosts, as well as the use of more than one specificity index, can all contribute to a deeper understanding of host-parasite interactions.