Biology subjects

Spencer, H. G.

Publications and source records attributed to Spencer, H. G..

4 recordsLinked to original sources

bioRxiv2026

Was the extinct Spectacled Cormorant part of the North Pacific kelp-associated fauna?

The coastal North Pacific kelp ecosystems are highly productive, supporting a rich faunal assemblage. Some historical aspects of this ecosystem remain poorly studied, as exemplified by the extinct Spectacled Cormorant Urile perspicillatus, whose Late Holocene distribution was apparently restricted to Bering Island. This cormorant's taxonomic relationships remain unresolved and little is known about its ecology. We use ancient-DNA to reconstruct the evolutionary history of the Spectacled Cormorant. Mitogenomes from five of the six known historical skins form a strongly supported clade within Urile cormorants. The ancestors of Spectacled Cormorant diverged from its closest relatives, the Pelagic (U. pelagicus) and Red-faced (U. urile) cormorants, ~6.98 Mya, and the population subsequently underwent a pronounced bottleneck. This divergence time is co-incident with the establishment of coastal kelp-forests. The Spectacled Cormorant may have been an integral part of the kelp-associated fauna as a large benthic-foraging predator. Similar to the sympatric Steller's sea cow (Hydrodamalis gigas), the historical relict distribution of the Spectacled Cormorant may be the result of trophic collapse of kelp-forest ecosystems and subsistence hunting. Future palaeogenomic and dietary isotopic research, and reassessment of North Pacific archaeological and fossil assemblages, should shed light on the evolution and palaeoecology of this enigmatic seabird.

evolutionary biology↗

bioRxiv2023

The radiation of Austral teals and the evolution of flightlessness

The origin and evolution in the Southern Hemisphere of the Austral teals, consisting of the grey-teal and brown-teal species complexes, remains poorly understood due to limited molecular data. With the group containing multiple independent examples of flight loss, understanding the evolutionary history of the group is of significant interest for functional genomic studies into the evolution of flightlessness. Here we present the first whole mitogenome-based phylogeny of the Austral teals. We show that the group diverged from a common ancestor with mallards in the late Miocene and soon after radiated into the brown-teal and grey-teal lineages, as well as the widely distributed pintails and green-winged ducks. The brown-teal species complex, which includes the volant brown and Chatham Island teals as well as the flightless, sub-Antarctic Auckland and Campbell Island teals, radiated within the past 0.9 - 2.2 million years. The divergence of the extinct Chatham Island teal, and the stepping-stone colonisation of the Auckland and Campbell Islands occurred from mainland New Zealand. Morphological changes towards flightlessness are also present in the volant brown teal on mainland New Zealand, suggesting that this group was on the pathway to flightlessess, which accelerated in some insular island lineages.

evolutionary biology↗

bioRxiv2022

The swan genome and transcriptome: its not all black and white

The Australian black swan (Cygnus atratus) is an iconic species with contrasting plumage to that of the closely related Northern Hemisphere white swans. The relative geographic isolation of the black swan may have resulted in a limited immune repertoire and increased susceptibility to infectious disease, notably infectious diseases from which Australia has been largely shielded. Indeed, unlike Mallard ducks and the mute swan (Cygnus olor), the black swan is extremely sensitive to severe highly pathogenic avian influenza (HPAI). Understanding this susceptibility has been impaired by the absence of any available swan genome and transcriptome information. Here, we generate the first chromosome-length annotated black and mute swan genomes annotated with transcriptome data, all using long-read based pipelines generated for vertebrate species. We used these genomes and transcriptomes, to show that unlike other wild waterfowl, black swans lack an expanded immune gene repertoire, lack a key viral pattern-recognition receptor in endothelial cells and mount a poorly controlled inflammatory response to HPAI. We also implicate genetic differences in SLC45A2 in the iconic plumage of the Australian black swan. Together, these data suggest that the immune system of the black swan is such that should any avian viral infection become established in its native habitat the survival of the black swan would be in significant peril.

genomics↗

bioRxiv2021

Rapid radiation of Southern Ocean shags in response to receding sea ice

AimUnderstanding how wild populations respond to climatic shifts is a fundamental goal of biological research in a fast-changing world. The Southern Ocean represents a fascinating system for assessing large-scale climate-driven biological change, as it contains extremely isolated island groups within a predominantly westerly, circumpolar wind and current system. The blue-eyed shags (Leucocarbo spp.) represent a paradoxical Southern Ocean seabird radiation; a circumpolar distribution implies strong dispersal capacity yet their speciose nature suggests local adaptation and isolation. Here we use genetic tools in an attempt to resolve this paradox. LocationSouthern Ocean. Taxa17 species and subspecies of blue-eyed shags (Leucocarbo spp.) across the geographical distribution of the genus. MethodsHere we use mitochondrial and nuclear sequence data to conduct the first global genetic analysis of this group using a temporal phylogenetic framework to test for rapid speciation. ResultsOur analysis reveals remarkably shallow evolutionary histories among island-endemic lineages, consistent with a recent high-latitude circumpolar radiation. This rapid sub-Antarctic expansion contrasts with significantly deeper lineages detected in more temperate regions such as South America and New Zealand that may have acted as glacial refugia. The dynamic history of high-latitude expansions is further supported by ancestral demographic and biogeographic reconstructions. Main conclusionsThe circumpolar distribution of blue-eyed shags, and their highly dynamic evolutionary history, potentially make Leucocarbo a strong sentinel of past and ongoing Southern Ocean ecosystem change given their sensitivity to climatic impacts.

evolutionary biology↗