DSpace Community:
https://hdl.handle.net/2440/5129
2024-03-18T15:57:07ZModification of vertebral regions explains heart position in arboreal colubrids (Serpentes: Colubridae)
https://hdl.handle.net/2440/140431
Title: Modification of vertebral regions explains heart position in arboreal colubrids (Serpentes: Colubridae)
Author: Nash-Hahn, T.; Stepanova, N.; Davis Rabosky, A.R.; Sherratt, E.
Abstract: Recent research into the snake vertebral column has highlighted the importance of considering regionalization and its implications for the life history of snakes. Our research delves into the distinctions in vertebral column morphology and regionalization within the snake family Colubridae, comparing arboreal and terrestrial species. Our results provide significant support for dissociation between two pre-cloacal regions: the ‘pre-atrial’ (anterior to heart) and the ‘post-atrial’ (posterior to heart). Furthermore, the two ecological groups display distinct proportional compositions between the two pre-cloacal regions and the one post-cloacal region (caudal); arboreal species tend to possess a higher proportion of caudal vertebrae, whereas terrestrial species exhibit a higher proportion of post-atrial vertebrae. Our study reveals that the axial morphology of arboreal species is distinct from that of terrestrial species; however, this was not attributable to a convergent evolution process. By estimating the evolutionary history of vertebral number in each region between the ecological groups, we find each region has a unique pattern, further highlighting evolutionary disassociation between the regions. This study adds to the growing evidence on regionalization of the pre-cloacal snake vertebral column and underscores the importance in continuing to develop our understanding of snake evolution.
Description: Advance access publication 27 February 2024.
OnlinePubl2024-01-01T00:00:00ZElucidating the morphology and ecology of Eoandromeda octobrachiata from the Ediacaran of South Australia
https://hdl.handle.net/2440/139912
Title: Elucidating the morphology and ecology of Eoandromeda octobrachiata from the Ediacaran of South Australia
Author: Botha, T.; Sherratt, E.; Droser, M.; Gehling, J.; Garcia-Bellido, D.
Abstract: Eoandromeda octobrachiata is a poorly understood Ediacaran organism, with spiral- octoradial arms, found in South Australia and South China. The informal Nilpena member of the Rawnsley Quartzite, Flinders Ranges in South Australia preserves more than 200 specimens of Eoandromeda. Here we use the novel application of rotational geometric morphometrics together with palaeoenvironmental information to provide a better insight into their palaeobiology and ecology and to address conflicting hypotheses regarding mode of life and taxonomic affinity. We find that Eoandromeda likely had a radially symmetrical shape in life, was cone-shaped and had a high relief off the microbial mat. Analysis of the symmetric and asymmetric shape components revealed they deform strongly in the direction of palaeocurrent, therefore are thought to be made of a flexible material. Almost all specimens are compressed flat. Specimens that appear to have not fully collapsed support the idea that Eoandromeda was likely cone-shaped and further suggest that they possibly collapsed spirally. Our shape analysis along with observed morphological features support the benthic mode of life hypothesis rather than pelagic. Morphological and ecological inconsistencies such as a lack of biradial symmetry and a benthic mode of life do not support the hypothesis of a Ctenophora taxonomic affinity.2023-01-01T00:00:00ZShape and size variation in elapid snake fangs, and the effects of phylogeny and diet
https://hdl.handle.net/2440/139911
Title: Shape and size variation in elapid snake fangs, and the effects of phylogeny and diet
Author: Palci, A.; Lee, M.S.Y.; Crowe-Riddell, J.; Sherratt, E.
Abstract: Recent studies have found correlations between the shape of snake teeth/fangs and diet. These studies were done at a very broad phylogenetic scale, making it desirable to test if correlations are still detectable at a narrower evolutionary scale, specifically within the family Elapidae. To this end, we studied fang shape in a dense selection of elapids representing most genera worldwide (74%). We used three-dimensional geometric morphometrics to analyse fang diversity and evaluate possible correlations between fang shape, fang size, and diet. We detected only weak phylogenetic signal in our dataset for both shape and size, and no significant evolutionary allometry when correcting for phylogeny. Overall, the distribution of elapid fangs in morphospace was found to be surprisingly conservative, with only a few outliers. The only two dietary categories that were found to have a significant effect on fang shape are fish and snakes, while mammals have a significant effect on absolute but not relative fang size. Our results show that there are disparate patterns in fang-diet relationships at different evolutionary scales. Across all venomous snakes, previous work found that fangs are strongly influenced by diet, but within elapids our study shows these same associations are weaker and often non-significant. This could result from limitations in these types of studies, or could reflect the fact that elapids are a relatively young clade, where recent extensive divergences in diet have yet to be mirrored in fang shape, suggesting a lag between changes in ecology and dental morphology.
Description: Published online: 9 October 20232023-01-01T00:00:00ZEvolutionary transition from surface to subterranean living in Australian water beetles (Coleoptera, Dytiscidae) through adaptive and relaxed selection
https://hdl.handle.net/2440/139907
Title: Evolutionary transition from surface to subterranean living in Australian water beetles (Coleoptera, Dytiscidae) through adaptive and relaxed selection
Author: Zhao, Y.; Guzik, M.; Humphreys, W.; Watts, C.; Cooper, S.; Sherratt, E.
Abstract: Over the last 5 million years, numerous species of Australian stygobiotic (subterranean and aquatic) beetles have evolved underground following independent colonisation of aquifers by surface ancestors, providing a set of repeated evolutionary transitions from surface to subterranean life. We used this system as an ‘evolutionary experiment’ to investigate whether relaxed selection has provided a source of variability for adaptive radiations into ecosystems containing open niches and whether this variability underpins phenotypic evolution in cave animals. Linear and landmark-based measurements were used to quantify the morphology of subterranean species from different aquifers, compared to interstitial and closely related aquatic surface species. Subterranean dytiscids were observed to be morphologically distinct, suggesting they have a different lifestyle compared to their surface relatives. However, the variation in the measured traits was much greater in the subterranean species, and unstructured, showing no evidence of clustering that would indicate adaptation to specific niches. Furthermore, a previously identified pattern of repeated non-overlapping size variation in beetles across aquifers was not correlated with repeated body shape evolution. The observed variability across body shape and limb traits provides support for the hypothesis that relaxed selection and neutral evolution underlie the phenotypic evolution in these species.
Description: Advance access publication 19 October 2023.
OnlinePubl2023-01-01T00:00:00Z