Molecular phylogeny and taxonomic revision of the genera Baudinella Thiele, 1931, Retroterra Solem, 1985 and Molema Köhler, 2011 endemic to the coastal Kimberley, Western Australia (Gastropoda, Camaenidae)

Validation and description of two new north-western Australian Rainbow skinks with multispecies coalescent methods and morphology

While methods for genetic species delimitation have noticeably improved in the last decade, this remains a work in progress. Ideally, model based approaches should be applied and considered jointly with other lines of evidence, primarily morphology and geography, in an integrative taxonomy framework. Deep phylogeographic divergences have been reported for several species of Carlia skinks, but only for some eastern taxa have species boundaries been formally tested. The present study does this and revises the taxonomy for two species from northern Australia, Carlia johnstonei and C. triacantha. We introduce an approach that is based on the recently published method StarBEAST2, which uses multilocus data to explore the support for alternative species delimitation hypotheses using Bayes Factors (BFD). We apply this method, jointly with two other multispecies coalescent methods, using an extensive (from 2,163 exons) data set along with measures of 11 morphological characters. We use this integrated approach to evaluate two new candidate species previously revealed in phylogeographic analyses of rainbow skinks (genus Carlia) in Western Australia. The results based on BFD StarBEAST2, BFD* SNAPP and BPP genetic delimitation, together with morphology, support each of the four recently identified Carlia lineages as separate species. The BFD StarBEAST2 approach yielded results highly congruent with those from BFD* SNAPP and BPP. This supports use of the robust multilocus multispecies coalescent StarBEAST2 method for species delimitation, which does not require a priori resolved species or gene trees. Compared to the situation in C. triacantha, morphological divergence was greater between the two lineages within Kimberley endemic C. johnstonei, which also had deeper divergent histories. This congruence supports recognition of two species within C. johnstonei. Nevertheless, the combined evidence also supports recognition of two taxa within the more widespread C. triacantha. With this work, we describe two new species, Carlia insularis sp. nov and Carlia isostriacantha sp. nov. in the northwest of Australia. This contributes to increasing recognition that this region of tropical Australia has a rich and unique fauna.

Phylogenetic systematics of the land snail Basedowena from the Australian arid zone: taxonomic revision with description of new taxa (Stylommatophora : Camaenidae)

The land snail Basedowena Iredale, 1937 currently comprises eight species that inhabit mountain ranges in the central Australian arid zone. By studying the variation in shell and genital anatomy and the differentiation in the mitochondrial markers 16S and COI, we revise the taxonomy of this camaenid and describe new taxa. We demonstrate that the current morphology-based classification has been misled by homoplasy mainly in shell shape. In fact, Basedowena as herein revised contains species with vastly different shells, which have so far been assigned to different genera. By contrast, these species have the same general genital anatomy in common and form a clade in the mitochondrial phylogeny. Based on these findings, we transfer Pleuroxia bethana, P. hinsbyi, P. elfina, P. oligopleura, P. polypleura, P. radiata, Montanomelon angatjana and Minimelon colmani to Basedowena. While Pleuroxia and Montanomelon are maintained as distinct genera, although with fewer species, the monotypic Minimelon becomes a junior synonym of Basedowena. We identify and describe three new Basedowena species (B. bicolor, sp. nov., B. holoserica, sp. nov., B. siparium, sp. nov.). A fourth new species differs substantially from all other arid zone camaenids and is hence placed in a new genus, Xeromelon, gen. nov. The revised delineation of Basedowena renders it now the most widespread camaenid genus in Australia. It is distributed throughout the Australian arid zone from Western Australia, via the Northern Territory and South Australia into New South Wales.

Snails in the desert: Assessing the mitochondrial and morphological diversity and the influence of aestivation behavior on lineage differentiation in the Australian endemic Granulomelon Iredale, 1933 (Stylommatophora: Camaenidae)

Progressive aridification since the mid-Miocene has had a significant influence on the evolution of the biota in the arid zone of central Australia. Especially moisture sensitive groups, such as snails, are often restricted to topographically complex areas, which have acted as refugia in an otherwise inhospitable environment. This historical fragmentation is deemed to be a potent agent of allopatric lineage diversification. Camaenid land snails are amongst only a few terrestrial gastropods that have managed to survive in the arid zone probably due to their ability to escape desiccation through aestivation. Here, we present the first study of the mitochondrial lineage differentiation in an endemic land snail genus from the Australian 'Red Centre', Granulomelon Iredale, 1933. Exposing significant incongruence between mtDNA phylogeny and morphology-based taxonomy, we completely revise the species and genus level taxonomy of this camaenid group. We demonstrate that this genus contains three species, G. grandituberculatum, G. adcockianum and G. squamulosum, which have so far been assigned to different genera: Granulomelon Iredale, 1933 (junior synonym: Baccalena Iredale, 1937), Basedowena Iredale, 1937 and Pleuroxia Ancey, 1887. Two of these species are widespread comprising multiple divergent mitochondrial lineages. Based on a molecular clock estimate, these lineages diverged approximately during the mid-Pleistocene, a period of particularly severe aridification. The phylogeographic patterns are consistent with an isolation-by-distance model in one species but not the other. We suggest that these differences can be attributed to their distinctive aestivation behavior.

A molecular phylogeny of camaenid land snails from north-western Australia unravels widespread homoplasy in morphological characters (Gastropoda, Helicoidea)

North-western Australia harbours more than 300 species of camaenid land snail in 41 genera exhibiting considerable and well documented morphological diversity. We performed Bayesian and Maximum Likelihood analyses of concatenated nuclear (28S) and mitochondrial (COI, 16S) DNA sequences from 140 species of 37 of these genera plus an additional 27 extralimital species in order to resolve their phylogenetic relationships and to address the significance of morphological characters for the delineation of monophyletic taxa. While north-western Australian Camaenidae in their entirety are not monophyletic with respect to extralimital groups, they underwent extensive in situ-diversification in several independent phylogenetic radiations. A Maximum Likelihood-based character history reconstruction revealed extensive convergence in all studied shell characters and in three out of four genital features across this group. However, in some genera close morphological similarity is best explained by the retention of ancestral characters. We hypothesize that both morphological stasis in some groups and convergent character evolution in others can to a large extent be attributed to adaptive transformations in response to historically increasing aridity throughout north-western Australia in concert with structural constraints.