Biology subjects

Scarsbrook, L.

Publications and source records attributed to Scarsbrook, L..

4 recordsLinked to original sources

bioRxiv2025

Brain size reduction in dogs was already established at least by the Late Neolithic of western Europe, 5,000 years ago

The timing and causes of brain size reduction in domestic dogs remain uncertain. Using endocasts volume as a proxy for brain size, this study provides a first insight into long-term brain size evolution in the wolf-dog lineage. We compared endocranial volumes of 185 modern and 22 prehistoric wolves and dogs ranging from Western Europe to Australia, and spanning the Pleniglacial (35 Ky BP) to the Late Neolithic (5 Ky BP). Our results reveal that Pleistocene so called "protodogs" show no brain size reduction compared to coeval Pleistocene wolves. Instead, we observed a slightly larger relative endocranial volume in the 35,000-year-old protodog from Goyet, which could suggest increased behavioural flexibility in the presence of humans. This hypothesis needs to be tested further. In contrast, Late Neolithic dogs show a drastic 46% brain size reduction with an endocranial volumes comparable to modern small terrier and toy breeds. The anxious and wary temperaments of these Late Neolithic dogs, induced by the brain tissue reorganization associated with such a size reduction, could have served an alerting purpose, among the many other potential roles dogs could have played within this Late Neolithic socio-ecosystems.

zoology↗

bioRxiv2024

Imputation of ancient canid genomes reveals inbreeding history over the past 10,000 years

The multi-millenia long history between dogs and humans has placed them at the forefront of archeological and genomic research. Despite ongoing efforts including the analysis of ancient dog and wolf genomes, many questions remain regarding their geographic and temporal origins, and the microevolutionary processes that led to the diversity of breeds today. Although ancient genomes provide valuable information, their use is hindered by low depth of coverage and post-mortem damage, which inhibits confident genotype calling. In the present study, we assess how genotype imputation of ancient dog and wolf genomes, utilising a large reference panel, can improve the resolution provided by ancient datasets. Imputation accuracy was evaluated by down-sampling high coverage dog and wolf genomes to 0.05-2x coverage and comparing concordance between imputed and high coverage genotypes. We measured the impact of imputation on principal component analyses and runs of homozygosity. Our findings show high (R2>0.9) imputation accuracy for dogs with coverage as low as 0.5x and for wolves as low as 1.0x. We then imputed a dataset of 90 ancient dog and wolf genomes, to assess changes in inbreeding during the last 10,000 years of dog evolution. Ancient dog and wolf populations generally exhibited lower inbreeding levels than present-day individuals. Interestingly, regions with low ROH density maintained across ancient and present-day samples were significantly associated with genes related to olfaction and immune response. Our study indicates that imputing ancient canine genomes is a viable strategy that allows for the use of analytical methods previously limited to high-quality genetic data.

evolutionary biology↗

bioRxiv2022

Ancient DNA from the extinct New Zealand grayling (Prototroctes oxyrhynchus) reveals evidence for Miocene marine dispersal

O_LIThe evolutionary history of Southern Hemisphere graylings (Retropinnidae) in Aotearoa New Zealand--including the number of colonisation events, the directionality and timing of dispersal, and their relationship to the Australian grayling--is poorly understood. The New Zealand grayling (Prototroctes oxyrhynchus) is the only known freshwater fish species to have gone extinct since human arrival in New Zealand. Despite its historical abundance, only 23 formalin-fixed specimens (both wet and dried) exist in museum collections globally, which were previously non-amenable to palaeogenetic analysis. C_LIO_LIHere, we used high-throughput DNA sequencing techniques, specifically designed for formalin-fixed specimens, to generate mitochondrial genomes of P. oxyrhynchus, and analysed these within a temporal phylogenetic framework of retropinnid and osmerid taxa. C_LIO_LIWe recovered strong evidence for a sister relationship between the New Zealand and Australian grayling (P. mareana), with the two having a common ancestor around 13.8 Mya (95% HPD: 6.1-23.2 Mya), after the height of Oligocene marine inundation in New Zealand. C_LIO_LIOur temporal phylogenetic analysis suggests a single marine dispersal event between New Zealand and Australia, though the direction of dispersal is equivocal, followed by divergence into genetically and morphologically distinguishable species through isolation by distance. C_LIO_LIThis study provides further insights into the possible drivers of the extinction of the New Zealand grayling, and highlights how advancements in palaeogenetic techniques can be used to test evolutionary hypotheses in extinct (and living) fish, which have been comparatively neglected in the field of ancient DNA. C_LI

evolutionary biology↗

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↗