Birth of a biome: insights into the assembly and maintenance of the Australian arid zone biota

Geographic variation in the age of temperate-zone reptile and amphibian species: Southern Hemisphere species are older

Despite controversy over alternative definitions, the species is the fundamental operational unit of biodiversity, and species are the building-blocks of conservation. But is a 'species' from one part of the world the same as a 'species' from elsewhere? Our meta-analysis of molecular phylogenetic data reveals that reptile and amphibian species distributed in temperate-zone areas of the Northern Hemisphere are younger than taxa from the Southern Hemisphere, probably reflecting the greater impact of past climatic variation on Northern Hemisphere habitats. Because a species' age may influence its vulnerability to anthropogenic threats, geographical variation in species ages should be incorporated into conservation planning.

Multilocus analysis of honeyeaters (Aves: Meliphagidae) highlights spatio-temporal heterogeneity in the influence of biogeographic barriers in the Australian monsoonal zone

Multilocus studies in phylogenetics and comparative phylogeography have the power to explore a broader spectrum of evolutionary questions than either discipline has alone. To examine the origins of sympatry in a group of closely related birds of mostly mesic eucalypt woodlands in Australia, we reconstructed the relationships among species of Entomyzon and Melithreptus honeyeaters (Aves: Passeriformes: Meliphagidae) using a mitochondrial marker, ND2, and six non-coding nuclear loci (total 4719 base pairs). By sampling across the geographical range of each species, we studied not only their phylogenetic relationships to each other but also the spatial distribution of their genetic diversity. We tested several biogeographic hypotheses concerning the role of Pleistocene environmental change in Australia. Phylogenetic gene trees support the current understanding of E. cyanotis as the sister to Melithreptus. Non-monophyly of M. lunatus in Australia's southern temperate woodlands highlights the need for a revision of systematics within Melithreptus. Phylogeographic analysis of the three northern species in Australia's monsoon tropics, M. gularis, M. albogularis and E. cyanotis, suggests that the roles of the Carpentarian and Torresian Barriers in shaping geographic structure in each of the species have been more complex and temporally dynamic than earlier morphology-based arguments of vicariance had suggested. We discuss their roles as ecological filters as well as barriers.

A Phylogeny and Timescale for the Evolution of Pseudocheiridae (Marsupialia: Diprotodontia) in Australia and New Guinea

PSEUDOCHEIRIDAE (MARSUPIALIA: Diprotodontia) is a family of endemic Australasian arboreal folivores, more commonly known as ringtail possums. Seventeen extant species are grouped into six genera (Pseudocheirus, Pseudochirulus, Hemibelideus, Petauroides, Pseudochirops, Petropseudes). Pseudochirops and Pseudochirulus are the only genera with representatives on New Guinea and surrounding western islands. Here, we examine phylogenetic relationships among 13 of the 17 extant pseudocheirid species based on protein-coding portions of the ApoB, BRCA1, ENAM, IRBP, Rag1, and vWF genes. Maximum parsimony, maximum likelihood, and Bayesian methods were used to estimate phylogenetic relationships. Two different relaxed molecular clock methods were used to estimate divergence times. Bayesian and maximum parsimony methods were used to reconstruct ancestral character states for geographic provenance and maximum elevation occupied. We find robust support for the monophyly of Pseudocheirinae (Pseudochirulus + Pseudocheirus), Hemibelidinae (Hemibelideus + Petauroides), and Pseudochiropsinae (Pseudochirops + Petropseudes), respectively, and for an association of Pseudocheirinae and Hemibelidinae to the exclusion of Pseudochiropsinae. Within Pseudochiropsinae, Petropseudes grouped more closely with the New Guinean Pseudochirops spp. than with the Australian Pseudochirops archeri, rendering Pseudochirops paraphyletic. New Guinean species belonging to Pseudochirops are monophyletic, as are New Guinean species belonging to Pseudochirulus. Molecular dates and ancestral reconstructions of geographic provenance combine to suggest that the ancestors of extant New Guinean Pseudochirops spp. and Pseudochirulus spp. dispersed from Australia to New Guinea ∼12.1-6.5 Ma (Pseudochirops) and ∼6.0-2.4 Ma (Pseudochirulus). Ancestral state reconstructions support the hypothesis that occupation of high elevations (>3000 m) is a derived feature that evolved on the terminal branch leading to Pseudochirops cupreus, and either evolved in the ancestor of Pseudochirulus forbesi, Pseudochirulus mayeri, and Pseudochirulus caroli, with subsequent loss in P. caroli, or evolved independently in P. mayeri and P. forbesi. Divergence times within the New Guinean Pseudochirops clade are generally coincident with the uplift of the central cordillera and other highlands. Diversification within New Guinean Pseudochirulus occurred in the Plio-Pleistocene after the establishment of the Central Range and other highlands. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10914-010-9129-7) contains supplementary material, which is available to authorized users.

Plio-pleistocene diversification and connectivity between mainland and Tasmanian populations of Australian snakes (Drysdalia, Elapidae, Serpentes)

The genus Drysdalia contains three recognised species of elapid (front-fanged) snakes, distributed across south-eastern Australia (including Tasmania). Here we aim to clarify the biogeography and phylogeographical relationships of this poorly documented region. We conducted molecular phylogenetic and dating analyses, using mitochondrial genes (ND4 and cyt-b). Our analyses suggest that divergence events among the three extant species, and among major lineages within those species, are congruent with Plio-pleistocene climatic variations. Two highly divergent genetic lineages within Drysdalia coronoides occur in Tasmania. Molecular dating suggests that these lineages were isolated from the mainland in the Pleistocene.

Evolutionary speed limited by water in arid Australia

The covariation of biodiversity with climate is a fundamental pattern in nature. However, despite the ubiquity of this relationship, a consensus on the ultimate cause remains elusive. The evolutionary speed hypothesis posits direct mechanistic links between ambient temperature, the tempo of micro-evolution and, ultimately, species richness. Previous research has demonstrated faster rates of molecular evolution in warmer climates for a broad range of poikilothermic and homeothermic organisms, in both terrestrial and aquatic environments. In terrestrial systems, species richness increases with both temperature and water availability and the interaction of those terms: productivity. However, the influence of water availability as an independent variable on micro-evolutionary processes has not been examined previously. Here, using methodology that limits the potentially confounding role of cladogenetic and demographic processes, we report, to our knowledge, the first evidence that woody plants living in the arid Australian Outback are evolving more slowly than related species growing at similar latitudes in moist habitats on the mesic continental margins. These results support a modified evolutionary speed explanation for the relationship between the water-energy balance and plant diversity patterns.

Diversification and persistence at the arid-monsoonal interface: australia-wide biogeography of the Bynoe's gecko (Heteronotia binoei; Gekkonidae)

Late Neogene aridification in the Southern Hemisphere caused contractions of mesic biota to refugia, similar to the patterns established by glaciation in the Northern Hemisphere, but these episodes also opened up new adaptive zones that spurred range expansion and diversification in arid-adapted lineages. To understand these dynamics, we present a multilocus (nine nuclear introns, one mitochondrial gene) phylogeographic analysis of the Bynoe's gecko (Heteronotia binoei), a widely distributed complex spanning the tropical monsoon, coastal woodland, and arid zone biomes in Australia. Bayesian phylogenetic analyses, estimates of divergence times, and demographic inferences revealed episodes of diversification in the Pliocene, especially in the tropical monsoon biome, and range expansions in the Pleistocene. Ancestral habitat reconstructions strongly support recent and independent invasions into the arid zone. Our study demonstrates the varied responses to aridification in Australia, including localized persistence of lineages in the tropical monsoonal biome, and repeated invasion of and expansion through newly available arid-zone habitats. These patterns are consistent with those found in other arid environments in the Southern Hemisphere, including the South African succulent karoo and the Chilean lowlands, and highlight the diverse modes of diversification and persistence of Earth's biota during the glacial cycles of the Pliocene and Pleistocene.

VIEWPOINT. Is the Australian subterranean fauna uniquely diverse?

Australia was historically considered a poor prospect for subterranean fauna but, in reality, the continent holds a great variety of subterranean habitats, with associated faunas, found both in karst and non-karst environments. This paper critically examines the diversity of subterranean fauna in several key regions for the mostly arid western half of Australia. We aimed to document levels of species richness for major taxon groups and examine the degree of uniqueness of the fauna. We also wanted to compare the composition of these ecosystems, and their origins, with other regions of subterranean diversity world-wide. Using information on the number of ‘described’ and ‘known’ invertebrate species (recognised based on morphological and/or molecular data), we predict that the total subterranean fauna for the western half of the continent is 4140 species, of which ~10% is described and 9% is ‘known’ but not yet described. The stygofauna, water beetles, ostracods and copepods have the largest number of described species, while arachnids dominate the described troglofauna. Conversely, copepods, water beetles and isopods are the poorest known groups with less than 20% described species, while hexapods (comprising mostly Collembola, Coleoptera, Blattodea and Hemiptera) are the least known of the troglofauna. Compared with other regions of the world, we consider the Australian subterranean fauna to be unique in its diversity compared with the northern hemisphere for three key reasons: the range and diversity of subterranean habitats is both extensive and novel; direct faunal links to ancient Pangaea and Gondwana are evident, emphasising their early biogeographic history; and Miocene aridification, rather than Pleistocene post-ice age driven diversification events (as is predicted in the northern hemisphere), are likely to have dominated Australia’s subterranean speciation explosion. Finally, we predict that the geologically younger, although more poorly studied, eastern half of the Australian continent is unlikely to be as diverse as the western half, except for stygofauna in porous media. Furthermore, based on similar geology, palaeogeography and tectonic history to that seen in the western parts of Australia, southern Africa, parts of South America and India may also yield similar subterranean biodiversity to that described here.

Phylogeography of the Australian sugar glider (Petaurus breviceps): evidence for a new divergent lineage in eastern Australia

The sugar glider (Petaurus breviceps) shows considerable variation in external morphology and mitochondrial DNA (mtDNA) diversity across its distribution in New Guinea and Australia. Here we investigate the phylogeography of P. breviceps in Australia using data from two mitochondrial genes (ND2 and ND4) and a nuclear gene (ω-globin). Phylogenetic analyses revealed the existence of two divergent mtDNA clades that are distributed over distinct geographical regions, one from coastal New South Wales and south-eastern Queensland and a second over the remaining distributional range of the species in Australia. The two groups generally had distinct ω-globin haplotypes that differed by one or two mutational steps. Analyses of Molecular Variation further supported the presence of at least two populations, accounting for 84.8% of the total mtDNA variation and 44% of the ω-globin variation. The general concordance of phylogeographic and population analyses suggests that population subdivision, possibly resulting from the combined influences of aridification after the Pliocene and uplift of the Great Dividing Range has impacted the evolution of P. breviceps. Our results also show that the geographical distribution of the two evolutionary lineages does not correspond with the distribution of the current morphological subspecies and we further propose that they be considered as separate Evolutionarily Significant Units for the purposes of conservation management.

Fine-scale comparative phylogeography of a sympatric sister species triplet of subterranean diving beetles from a single calcrete aquifer in Western Australia

Calcrete aquifers in the arid Yilgarn region of central Western Australia are a biodiversity hotspot for stygofauna. A distinct pattern of interspecific size class variation among subterranean dytiscid beetle species has been observed in 29 of these aquifers where either two or three small, medium and/or large sympatric species are found that are in some cases sister species. We used a 3.5 km(2) grid of bores to sample dytiscids on a fine-scale and employed a comparative phylogeographical and population genetic approach to investigate the origins of a sympatric sister species triplet of diving beetles from a single aquifer. Mitochondrial DNA sequence data from the Cytochrome oxidase c subunit I gene revealed that all three species have high levels of haplotype diversity with ancient (approximately 1 million years ago) intra-specific coalescence of haplotypes, but low levels of nucleotide diversity. Population analyses provide evidence for multiple expansion events within each species. There was spatial heterogeneity in the distribution of genetic variation and abundance both within and among the three taxa. Population analyses revealed significant fine-scale differentiation with isolation by distance for Paroster macrosturtensis and P. mesosturtensis, but not the smallest species P. microsturtensis. Haplotype network analyses provided limited or no evidence for past population fragmentation within the large and small species, but substantial historical divergence was observed in P. mesosturtensis that was not spatially structured. A patchy population structure with contemporaneous and historical isolation by distance in the three species is likely to have been a significant isolating and diversifying force, preventing us from ruling out a potential role for allopatric divergence during speciation of this beetle sister triplet.

The evolution of sexual and parthenogenetic Warramaba: a window onto Plio-Pleistocene diversification processes in an arid biome

Environmental changes over the Plio-Pleistocene have been key drivers of speciation patterns and genetic diversification in high-latitude and mesic environments, yet comparatively little is known about the evolutionary history of species in arid environments. We applied phylogenetic and phylogeographic analyses to understand the evolutionary history of Warramaba grasshoppers from the Australian arid zone, a group including sexual and parthenogenetic lineages. Sequence data (mitochondrial COI) showed that the four major sexual lineages within Warramaba most likely diverged in the Pliocene, around 2-7 million years ago. All sexual lineages exhibited considerable phylogenetic structure. Detailed analyses of the hybrid parthenogenetic species W. virgo and its sexual progenitors showed a pattern of high phylogenetic diversity and phylogeographic structure in northern lineages, and low diversity and evidence for recent expansion in southern lineages. Northern sexual lineages persisted in localized refugia over the Pleistocene, with sustained barriers promoting divergence over this period. Southern parts of the present range became periodically unsuitable during the Pleistocene, and it is into this region that parthenogenetic lineages have expanded. Our results strongly parallel those for sexual and parthenogenetic lineages of the gecko Heteronotia from the same region, indicating a highly general effect of Plio-Pleistocene environmental change on diversification processes in arid Australia.

Australian pirates: systematics and phylogeny of the Australasian pirate spiders (Araneae:Mimetidae), with a description of the Western Australian fauna

Pirate spiders (Mimetidae) are well known for their specialised feeding ecology. They are vagrant araneophagic predators, enter the webs of their prey spiders and exhibit patterns of aggressive mimicry to overcome the web owner. The mimetid fauna of Australia and New Zealand currently consists of 26 species in the following three genera: Australomimetus Heimer, 1986 (18 species), Mimetus Hentz, 1832 (six species), and Ero C.L. Koch, 1836 (two species). The systematic position of the majority of Australasian mimetids was investigated through phylogenetic techniques utilising morphological character systems of 29 exemplar taxa and 87 characters, including the first examination of spinneret structure in species of Australomimetus. The results support an expanded concept for Australomimetus, which, apart from the introduced Ero aphana (Walckenaer, 1802), is found to contain the entire Australian and New Zealand mimetid fauna, also recorded from Asia. The following taxonomic changes are proposed: A. catulli (Heimer, 1989), comb. nov., A. hannemanni (Heimer, 1989), comb. nov., A. japonicus (Uyemura, 1938), comb. nov., A. mendicus (O. P. Cambridge, 1879), comb. nov. and A. sennio (Urquhart, 1891), comb. nov.; Ero luzoniensis Barrion & Litsinger, 1995 is synonymised with Ero aphana, and A. andreae Heimer, 1989 is synonymised with A. daviesianus Heimer, 1986; Mimetus tikaderi Gajbe, 1992 from India is excluded from Mimetidae, and referred to Liocranidae. The Western Australian mimetid fauna is described for the first time and comprises nine species of Australomimetus, including the following five new species: A. diabolicus, sp. nov., A. djuka, sp. nov., A. dunlopi, sp. nov., A. nasoi, sp. nov. and A. stephanieae, sp. nov. Several species-groups of Australomimetus are identified.