The two species of ground parrots (Pezoporus wallicus and P. flaviventris) are morphologically and behaviourally similar, yet geographically disjunct and genetically distinct. We investigated the dynamics of divergence between the two species in the context of niche evolution across Australian platycercine parrots.
Australia.
Platyercine parrots.
We estimated climatic and habitat niche breadths for all Australian platycercine parrots and quantified niche overlap between species. We constructed climate envelope niche models for ground parrots to project paleoclimatic suitability, and reconstructed biogeographic and climatic niche evolution of platycercine parrots using phylogenetic comparative methods.
We found that the western ground parrot (P. flaviventris) occupies a narrow climatic niche almost entirely nested within the broader niche of the eastern ground parrot (P. wallicus), which has the widest climatic niche of any Australian platycercine. Habitat niches also differ markedly, with P. flaviventris specialised to mallee and heathland vegetation, and P. wallicus using a wider array of habitats. Palaeoclimate projections suggest a formerly contiguous range across southern Australia that became fragmented ~2 Mya, coinciding with increasing aridity across the Nullarbor plain. Evolutionary models support niche expansion in P. wallicus, consistent with speciation following allopatric isolation and subsequent ecological divergence.
Our findings provide evidence for ecological speciation under niche conservatism and have important implications for conservation management of the Critically Endangered P. flaviventris, including consideration of genetic rescue strategies involving P. wallicus.
Biogeographic allopatry is easy to miss when clades are not mapped because the patterns are made invisible. This invisibility occurs when ancestral area programs analyse the relationships of artificially constructed areas that have no direct relationship with the distributions of taxa. This problem is illustrated with reference to Leptotes clades, where ancestral areas analysis generates ambiguous results over the role of vicariance and chance dispersal for Madagascar and America. Examination of clade distributions as visible patterns shows that three principal clades are reciprocally allopatric, other than for one widespread African species. The principal allopatric groups are America-Canary Islands, Africa-Europe-Middle East, southern and eastern Asia-eastern Australia. Each clade comprises two allopatric subclades (excluding one widespread species), which is consistent with allopatric divergence of a widespread ‘pantropical’ ancestor in the Mesozoic. The vicariance pattern of Leptotes clades is repeated by similar patterns in Vanessa (Nymphalidae), Biblidini (Nymphalidae) and Leptocircini (Papilionidae) butterflies. Concordant allopatry requires chance dispersal to generate the same or similar results, time and again in different taxa, whereas a vicariance process implies past tectonic, geological or ecological disruption of entire biotas. The presence of endemic Leptotes on oceanic islands (Galapagos, Canary Islands, Mauritius, Príncipe and São Tomé) does not necessitate chance dispersal, as tectonic studies indicate that the history of these locations involved former geological connections and relationships with other regions. These events could mediate widespread ancestral Leptotes distributions followed by isolation and local survival from Mesozoic time to the present through sequential metapopulation persistence. The biogeography of Leptotes suggests its distribution is an integral part of the global fabric of life rather than the result of waifs and strays disconnected from life in general.
Globally, island biotas are continuing to experience catastrophic losses leading to species extinctions. In Australia, 31 bird taxa have become extinct since European colonisation, including four from Tasmania including Macquarie Island. In 2024, the Tasmanian Government's State of the Environment Report provided compelling evidence on the broad scale deterioration in the conservation status of Tasmania's birds, with the number of threatened species comprising 12.5% of all bird taxa known from the State. This alarming finding concurs with other State and National assessments that have shown losses in Australia's avifauna have been underway for decades. However, by excluding taxa on subantarctic Macquarie Island, the situation on mainland Tasmania is even more concerning with 37 bird taxa currently listed on State and Commonwealth threatened species legislations, representing over 18% of all non-vagrant native bird taxa in Tasmania. These legislations include 18 endangered or critically endangered taxa and 13 endemic breeding species or subspecies with increasing extinction trajectories. Here, the survival prospects of mainland Tasmania's birds are viewed through the lens of well-established risk factors intrinsic to island faunas to highlight the urgency to catalyse conservation efforts for those identified at elevated risk of extinction.
The aim of this study was to elucidate the phylogenetic and evolutionary history of the colubrid genus Platyceps.
Saharo–Arabian biogeographic realm.
Genus Platyceps, Colubridae, Squamata.
We sequenced four mitochondrial (12S rRNA, cytb, ND4 + tRNA, COI) and two nuclear (c-mos, NT3) markers of 19 species (115 newly analysed tissue samples) of the genus Platyceps, covering the entire distribution of the genus, to build both Maximum Likelihood (IQ-Tree) and Bayesian inference (BEAST) trees. Furthermore, for the first time, we reconstructed the historical biogeography of this genus based on a time-calibrated tree using the BioGeoBEARS package in R.
Our results confirmed Platyceps to be monophyletic and that it is divided into four main groups (plinii, ventromaculatus, karelini, and florulentus). The genus diverged in the Early Miocene (around 19.9 million years ago) when the ancestor of the plinii group split. This was followed by the separation of the three main groups (ventromaculatus, karelini, and florulentus) around 18.6 million years ago. The genus's representatives then spread from their most probable place of origin in South Asia to the entire Saharo-Arabian biogeographic realm.
The genus originated most likely in South Asia from where it expanded three independent times through the Arabian Peninsula to northeastern Africa. The dispersal events were likely enabled by the existence of temporary land bridges between Africa and Arabia. Considering that many of the Platyceps species are well adapted to arid conditions, the distribution was also affected by the Miocene climatic changes and the increasing aridification of the North African and Arabian arid belt.
Aims of the study are to examine patterns of range-wide genetic differentiation and population structure in a headwater obligate salamander living in a geologically rich region, to identify genetically distinct populations and areas of gene flow between them.
Oregon and Washington in the Pacific Northwest, United States of America.
Tissue samples were collected in 2022 and 2023.
The Cascade torrent salamander Rhyacotriton cascadae.
Utilisation of a genome-wide single nucleotide polymorphism (SNP) dataset from across the species range to conduct a principal components analysis (PCA), Bayesian model of population structure, co-ancestry matrix, phylogenetic tree and estimate genetic diversity.
There are extensive levels of population structure within R. cascadae, including a previously unknown and highly differentiated clade. Structure is characterised by an island-like pattern wherein the species is comprised of six populations that function as independent demographic units, with gene flow largely constrained within populations.
Our findings reveal cryptic population structure within R. cascadae, identifying six distinct populations across the range. The northernmost population in the northwest of the species range in Washington is surprisingly highly divergent from the other five populations, and the divergence was not previously known to science. While major rivers act as phylogeographic boundaries between some populations, these boundaries appear to not always be complete.
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