Michael Lee
All new papers now written up on Instagram/Threads (shifting fromTwitter)
https://www.instagram.com/michael_s_y_lee
https://www.threads.net/@michael_s_y_lee
Evolutionary biology, phylogenetics, Bayesian inference, palaeontology, macroevolution, herpetology, lizards, snakes, reptiles.
Supervisors: Jennifer Clack FRS
https://www.instagram.com/michael_s_y_lee
https://www.threads.net/@michael_s_y_lee
Evolutionary biology, phylogenetics, Bayesian inference, palaeontology, macroevolution, herpetology, lizards, snakes, reptiles.
Supervisors: Jennifer Clack FRS
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Popular Press Articles - Unrefereed by Michael Lee
documented compared with other groups. Here, we describe a gigantic
Pleistocene skink from Australia based on extensive material that includes
much of the skull and postcranial skeleton, and spans ontogenetic stages
from neonate to adult. Tiliqua frangens substantially expands the known
ecomorphological diversity of squamates. At approximately 2.4 kg, it was
more than double the mass of any living skink, with an exceptionally
broad, deep skull, squat limbs and heavy, ornamented body armour.
It probably filled the armoured herbivore niche that land tortoises (testudinids), absent from Australia, occupy on other continents. Tiliqua frangens and other giant Plio-Pleistocene skinks suggest that small-bodied groups that dominate vertebrate biodiversity might have lost their largest and often most morphologically extreme representatives in the Late Pleistocene, expanding the scope of these extinctions.
Here, we assess GMM-based phylogenetic reconstructions in a heavily
sampled source of discrete characters formammalian phylogenetics—the basicranium— in 57 species of marsupial mammals, compared with the remainder of the cranium.We showless phylogenetic signal in the basicranium compared with a ‘Rest of Cranium’ partition, using diverse metrics of phylogenetic signal (Kmult, phylogenetically aligned principal components analysis, comparisons of UPGMA/neighbour-joining/parsimony trees and cophenetic distances to a reference phylogeny) for scaled, Procrustes-aligned landmarks and allometry-corrected residuals. Surprisingly, a similar pattern emerged from parsimony-based analyses of discrete cranial characters. The consistent results across methods suggest that easily computed metrics such as Kmult can provide
good guidance on phylogenetic information in a landmarking configuration. In addition, GMM data may be less informative for intricate but conservative anatomical regions such as the basicranium, while better—but not necessarily novel—phylogenetic information can be expected for broadly characterized shapes such as entire bones.
evidence of a flat S-shaped heart, which is well separated from the liver and other abdominal organs, and the absence of lungs. Arthrodires thus show the earliest phylogenetic evidence for repositioning of the gnathostome heart associated with the evolution of the complex neck region in jawed vertebrates
biodiversity and species demographies over the Holocene. In some cases, these two factors can be
resolved using fossil data, but for many taxa such data are not available. Inferring historical
demographies of taxa has become common, but the methodologies are mostly recent and their
shortcomings often unexplored. The bee genus Homalictus is developing into a tractable model
system for understanding how native bee populations in tropical islands have responded to past
climate change. We greatly expand on previous studies using sequences of the mitochondrial gene
COI from 474 specimens and between 171 and 3,928 autosomal (DArTSeq) SNP loci from 19
specimens of the native Fijian bee, Homalictus fijiensis (Perkins & Cheesman, 1928), to explore
its historical demography using coalescent and mismatch analyses. We ask whether past changes
in demography were human- or climate-driven, while considering analytical assumptions. We
show that inferred changes in population sizes are too recent to be explained by past climate
change. Instead we find that a dramatic increase in population size for the main island of Viti Levu
coincides with increasing occupation by humans and their modification of the environment. We
found no corresponding change in bee population size for another major island, Kadavu, where
human populations and agricultural activities have been historically very low. Our analyses
indicate that molecular approaches can be used to disentangle the impacts of humans and climate
change on a major tropical pollinator and that stringent analytical approaches are required for
reliable interpretation of results.
the fossil gap predicted by molecular data. The new species is estimated
to have been over 1 m long, much larger than typical modern scolecophidians (<30 cm). This finding sheds light on the early evolution of blind snakes, supportsthe hypothesis of a Gondwanan origin for the Typhlopoidea, and indicates that early scolecophidians had large body size, and only later underwent miniaturization.
There are several competing hypotheses to explain the high species richness of the Indo-Australian Archipelago (IAA) marine biodiversity hotspot centred within Southeast (SE) Asia. We use phylogenetic methods to provide a novel perspective on this problem using viviparous sea snakes, a group with high species richness in the IAA that is highly distinct from other taxa previously studied, both phylogenetically (Reptilia, Amniota) and biologically (e.g. viviparity and direct development).
Location
Indian Ocean and the West Pacific.
Methods
We used likelihood and Bayesian methods to reconstruct a multi-locus time-calibrated phylogeny for c. 70% of viviparous sea snake species, many sampled from multiple localities in Australasia, Southeast Asia and the Indian Ocean. We then compared rates and temporal concordance of inferred vicariance and dispersal events between marine basins using several approaches including new Bayesian analyses that allow for clade-specific and event-specific dispersal rates.
Results
Phylogenetic analyses and novel Bayesian biogeographical reconstructions indicate that viviparous sea snakes underwent rapid speciation after colonizing SE Asia c. 3 million years ago. Most of the SE Asian sea snake diversity is the result of in situ speciation, most consistent with the ‘centre of origin’ and ‘centre of refuge’ models for biodiversity hotspots. There is also speciation at the periphery, or entirely outside SE Asia; however, contrary to predictions of the ‘accumulation’ and ‘overlap’ models, these new outlying taxa do not preferentially disperse back into SE Asia. Instead, lineages are equally likely to disperse either into or away from SE Asia.
Main conclusion
The high diversity of sea snakes in SE Asia (and hence the IAA) is mostly explained by in situ speciation rather than accumulation or overlap. Most speciation events are contemporaneous with sea level changes that generated and dissolved barriers between marine basins during the last 2.5 million years.