New Guinea uplift opens ecological opportunity across a continent

Aridification and major geotectonic landscape change shaped an extraordinary species radiation across a world's extreme elevational gradient

Understanding the profound influence of climatic and tectonic histories on adaptation and speciation is a crucial focus in biology research. While voyages like Humboldt's expedition shaped our understanding of adaptation, the origin of current biodiversity remains unclear - whether it arose in situ or through dispersal from analogous habitats. Situated in the geologically complex Australopacific region, our study focuses on Limbodessus diving beetles (Dytiscidae), a diverse genus distributed from underground aquifers in Western Australia to alpine meadows in New Guinea. Using low-coverage whole-genome sequencing, we established a time-calibrated phylogenetic tree, elucidating Limbodessus' origin in the mid-late Miocene, most likely in the Sahul continent (i.e., Australia and New Guinea) and western Pacific archipelagos. Our results provide evidence for parallel colonization and speciation at extreme altitudinal ends, driven by aridification in Australia, influencing subterranean colonization, and in situ diversification of alpine taxa by passive-uplifting of local biota in New Guinea. Furthermore, our findings highlight instances of subterranean speciation in isolated underground aquifers, marked by recurrent independent colonizations of this habitat.

Morphological evolution and niche conservatism across a continental radiation of Australian blindsnakes

Understanding how continental radiations are assembled across space and time is a major question in macroevolutionary biology. Here, we use a phylogenomic-scale phylogeny, a comprehensive morphological dataset, and environmental niche models to evaluate the relationship between trait and environment and assess the role of geography and niche conservatism in the continental radiation of Australian blindsnakes. The Australo-Papuan blindsnake genus, Anilios, comprises 47 described species of which 46 are endemic to and distributed across various biomes on continental Australia. Although we expected blindsnakes to be morphologically conserved, we found considerable interspecific variation in all morphological traits we measured. Absolute body length is negatively correlated with mean annual temperature, and body shape ratios are negatively correlated with soil compactness. We found that morphologically similar species are likely not a result of ecological convergence. Age-overlap correlation tests revealed niche similarity decreased with the relative age of speciation events. We also found low geographical overlap across the phylogeny, suggesting that speciation is largely allopatric with low rates of secondary range overlap. Our study offers insights into the eco-morphological evolution of blindsnakes and the potential for phylogenetic niche conservatism to influence continental scale radiations.

To and fro in the archipelago: Repeated inter-island dispersal and New Guinea's orogeny affect diversification of Delias, the world's largest butterfly genus

The world's largest butterfly genus Delias, commonly known as Jezebels, comprises ca. 251 species found throughout Asia, Australia, and Melanesia. Most species are endemic to islands in the Indo-Australian Archipelago or to New Guinea and nearby islands in Melanesia, and many species are restricted to montane habitats over 1200 m. We inferred an extensively sampled and well-supported molecular phylogeny of the group to better understand the spatial and temporal dimensions of its diversification. The remarkable diversity of Delias evolved in just ca. 15-16 Myr (crown age). The most recent common ancestor of a clade with most of the species dispersed out of New Guinea ca. 14 Mya, but at least six subsequently diverging lineages dispersed back to the island. Diversification was associated with frequent dispersal of lineages among the islands of the Indo-Australian Archipelago, and the divergence of sister taxa on a single landmass was rare and occurred only on the largest islands, most notably on New Guinea. We conclude that frequent inter-island dispersal during the Neogene-likely facilitated by frequent sea level change-sparked much diversification during that period. Many extant New Guinea lineages started diversifying 5 Mya, suggesting that orogeny facilitated their diversification. Our results largely agree with the most recently proposed species group classification system, and we use our large taxon sample to extend this system to all described species. Finally, we summarize recent insights to speculate how wing pattern evolution, mimicry, and sexual selection might also contribute to these butterflies' rapid speciation and diversification.

Speciation across biomes: Rapid diversification with reproductive isolation in the Australian delicate mice

Phylogeographic studies of continental clades, especially when combined with palaeoclimate modelling, provide powerful insight into how environment drives speciation across climatic contexts. Australia, a continent characterized by disparate modern biomes and dynamic climate change, provides diverse opportunity to reconstruct the impact of past and present environments on diversification. Here, we use genomic-scale data (1310 exons and whole mitogenomes from 111 samples) to investigate Pleistocene diversification, cryptic diversity, and secondary contact in the Australian delicate mice (Hydromyini: Pseudomys), a recent radiation spanning almost all Australian environments. Across northern Australia, we find no evidence for introgression between cryptic lineages within Pseudomys delicatulus sensu lato, with palaeoclimate models supporting contraction and expansion of suitable habitat since the last glacial maximum. Despite multiple contact zones, we also find little evidence of introgression at a continental scale, with the exception of a potential hybrid zone in the mesic biome. In the arid zone, combined insights from genetic data and palaeomodels support a recent expansion in the arid specialist P. hermannsburgensis and contraction in the semi-arid P. bolami. In the face of repeated secondary contact, differences in sperm morphology and chromosomal rearrangements are potential mechanisms that maintain species boundaries in these recently diverged species. Additionally, we describe the western delicate mouse as a new species and recommend taxonomic reinstatement of the eastern delicate mouse. Overall, we show that speciation in an evolutionarily young and widespread clade has been driven by environmental change, and potentially maintained by divergence in reproductive morphology and chromosome rearrangements.

Paleoenvironments shaped the exchange of terrestrial vertebrates across Wallace's Line

Faunal turnover in Indo-Australia across Wallace's Line is one of the most recognizable patterns in biogeography and has catalyzed debate about the role of evolutionary and geoclimatic history in biotic interchanges. Here, analysis of more than 20,000 vertebrate species with a model of geoclimate and biological diversification shows that broad precipitation tolerance and dispersal ability were key for exchange across the deep-time precipitation gradient spanning the region. Sundanian (Southeast Asian) lineages evolved in a climate similar to the humid "stepping stones" of Wallacea, facilitating colonization of the Sahulian (Australian) continental shelf. By contrast, Sahulian lineages predominantly evolved in drier conditions, hampering establishment in Sunda and shaping faunal distinctiveness. We demonstrate how the history of adaptation to past environmental conditions shapes asymmetrical colonization and global biogeographic structure.

Evolution: The evolutionary rat race in New Guinea and Australia

A new molecular phylogeny of a remarkable radiation of New Guinean and Australian rodents indicates multiple transitions between biomes and biogeographical regions within the group, and suggests that a key role was played by the geological history of New Guinea.