Biology subjects

Rawlence, N. J.

Publications and source records attributed to Rawlence, N. J..

3 recordsLinked to original sources

bioRxiv2022

Convergent evolution of skim feeding in baleen whales

The origin of pygmy right whales (Caperea marginata), the smallest and most enigmatic of the living baleen whales, remains contentious. Morphological analyses largely continue to ally Caperea with right whales (balaenids) based on shared cranial features like a tall braincase and a narrow, highly arched rostrum. By contrast, molecular data and some anatomical evidence suggest a closer relationship with rorquals (balaenopterids), but fail to explain "the substantial issue of convergence posed by the many balaenid features of Caperea" (Berta & Demere, 2017). To resolve this question, we sequenced the nuclear genome of C. marginata (812,269,251 paired reads; 47X average depth of coverage, with 89.33% of the genome covered at [≥]10X) and subjected it to a multispecies coalescent analysis including representatives of all baleen whale families. Our results confirm Caperea as sister to rorquals and, thus, the convergent origin of its right whale-like anatomy. Considering this overwhelming molecular evidence, we propose that the traditional taxonomic grouping of Caperea with right whales be abandoned.

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↗