Genetic diversity in clustered colonies of an Antarctic marine mesopredator: a role for habitat quality?

Abstract

Genetic structure may be highly variable across seabird species, and particularly among those that are distributed over large geographical areas. The Adélie penguin (Pygoscelis adeliae) is a numerically dominant Antarctic seabird that is considered to be a key species in coastal ecosystems. Since the Last Glacial Maximum, penguin colonization of the Antarctic coastline occurred at varying geographical and temporal scales, contributing to an incomplete understanding of how modern colonies relate to each other at local or regional scales. We assessed the population genetic structure of Adélie penguins (n = 86 individuals) from three adjacent colonies along the Victoria Land coast using molecular genetic markers (i.e. seven microsatellite loci isolated through next-generation sequencing). Our results indicate meta-population dynamics and possibly relationships with habitat quality. A generally low genetic diversity (Nei's index: 0.322–0.667) was observed within each colony, in contrast to significant genetic heterogeneity among colonies (pairwise FST = 0.071–0.148), indicating that populations were genetically structured. Accordingly, an assignment test correctly placed individuals within the respective colonies from which they were sampled. The presence of inter-colony genetic differentiation contrasts with previous studies on this species that showed a lack of genetic structure, possibly due to higher juvenile or adult dispersal. Our sampled colonies were not panmictic and suggest a lower migration rate, which may reflect relatively stable environmental conditions in the Ross Sea compared to other regions of Antarctica, where the ocean climate is warming.

Pitfalls and advances in morphometric sexing: insights from the Adélie penguin Pygoscelis adeliae

“…If sexual dimorphism in bill size was due to sexual selection, one could speculate that a lower sexual selection on bill size may have occurred because of the relatively low habitat quality at Edmoson Point. In this colony, persistent fast-ice and high density of terrestrial predators (South Polar Skua Stercorarius maccormicki) seem to increase energetic constraints of penguins (see Clarke et al 1998;Olmastroni et al 2004Olmastroni et al , 2020Pezzo et al 2007;Mori et al 2021, for environmental-related constraints at Edmonson Point), which might have reduced the potential investment in sexual selection. Nevertheless, this hypothesis remains to be tested across colonies differing in habitat quality/predator density.…”

Breeding Ecology of Adélie Penguins in Mid Victoria Land, Ross Sea Antarctica

“…Our study took place for two summer seasons, November to February 2017-2 2018-2019. The Adélie penguin population was monitored to compare b chronology and success among colonies located between Wood Bay and Terra N on a 75 km stretch of coast along central Victoria Land, Ross Sea, Antarctica (F The ecological features of the three penguin colonies (Inexpressible Island, InIs, 163°39′ E; Adélie Cove, AdCo, 74°46′ S, 164°00′ E; Edmonson Point, EdPo, 74°20′ S E), i.e., marine and colony habitats that characterize these sites, have been deta previous study [40]. Colony size was markedly greater at InIs than at AdCo an with the latter showing the lowest population size.…”

“…EdPo has the lowest habitat with the highest per capita density of terrestrial predators (South Polar skua Ste maccormicki), the farthest distance from polynya and the greatest extension of fast main differences in penguin population abundance, seasonal sea ice regimes, and of terrestrial predators occurring among the study colonies are summarized in T Figure 1. Map of the three study areas located in the Ross Sea (modified by [40]).…”

“…The linear distance to Terra Nova Bay polynya and range of fast ice exten measured using EOSDIS Worldview [42] to the best image available in late October, mid-D and mid-January from 2017 to 2019. The approximate size of the colony area was measu Google Earth Pro on images on the 23 February 2010, 27 November 2011 and 2 Decembe Edmonson Point, Adélie Cove, and Inexpressible Island, respectively, updated from [40]. The annual life cycle of Adélie penguins is characterized by a short and The annual life cycle of Adélie penguins is characterized by a short and highly synchronized breeding period (Figure 2).…”

“…Adélie penguin colonies in the Mid Victoria Land are relatively close to each other but exposed to different local sea ice conditions and differ as much as tenfold in breeding population size [39][40][41]. Intraspecific competition over food resources may have cascading effects on foraging strategies, diet, and breeding performance of penguins [37], and the presence of the Terra Nova Bay polynya may play an important role in facilitating access to foraging areas, reducing the energy-time budget for breeders throughout the reproductive season [25,39].…”