Beyond the prolegomenon: a molecular phylogeny of the Australian camaenid land snail radiation

Abstract

From an analysis of over 900 specimens of camaenid land snails, we have assembled a molecular phylogeny of 327 tips covering > 70% genera across the entire continent of Australia and including > 90% of eastern species. Our approach emphasizes sampling to identify lineage flocks from populations down to build a hierarchical gene-bytaxa tapestry or supermatrix dataset using three mitochondrial genes, then analysed with Markov chain Monte Carlo and fast maximum likelihood methods. Similarity amongst taxa set results suggests missing data cause only minor distortions. This is supplemented by a separate higher level 28S rDNA phylogeny for a global scale perspective. The shallow divergence of Australasian forms, and their nesting within South-East Asian groups within the Helicoidea supergroup extending from Europe to North America, is consistent with the Solem hypothesis of Laurasian immigration of c. Miocene origin, and so being more than 400 species in 80-plus genera spread across the continent of Australia from rainforest to desert, forms an immense radiation. There is a major distinction between eastern and western lineages, with some key exceptions. Finer scale patterns of relictual endemics indicate that many ancestral lineages were in place before the major decline and breakup of the Tertiary mesic forest realm that once dominated Gondwanan Australia, and so chart the phylogenetic turnover of ecosystem change from mesic to xeric. The various higher classification schemes proposed all founder on the sheer scale of this radiation. Of 30 polytypic genera tested, at least 18 are not monophyletic, highlighting (1) the repeated radiation of shell forms, and (2) that the current higher taxonomy is unacceptable. Here we provide a phylogenetic and biogeographically condign arrangement as the basis for future elaborations.

Decline of a biome: evolution, contraction, fragmentation, extinction and invasion of the Australian mesic zone biota

“…For camaenid land snails, the phylogenetic evidence is consistent with relatively recent (Miocene) colonization and subsequent radiation through the mesic zone (Hugall et al. , 2002; Hugall & Stanisic, 2011).…”

Young relicts and old relicts: a novel palaeoendemic vertebrate from the Australian Central Uplands

“…Thus, while a majority of Central Uplands relicts probably do postdate the Pliocene wet phase, as dated molecular phylogenies accumulate, it seems likely that a smaller number will be shown to have longer histories of isolation (especially in specialized taxa, those with low mobility and/or a high capacity to persist in localized microrefugia, e.g. [13,57]).…”

Plio‐Pleistocene out‐of‐Australia dispersal in a camaenid land snail

“…Within this Australasian camaenid clade, Rhagada appeared as an early offshoot within ‘Clade 10’ comprising north‐western Australian and New Guinean lineages (Figure 7 in Hugall & Stanisic, ). In fact, the phylogenies presented by Hugall & Stanisic () revealed more complex phylogenetic – and thus biogeographical – relationships between Australian and New Guinean camaenid lineages than previously supposed. However, currently available phylogenetic reconstructions cannot resolve the proposed Oriental ancestry of the Australasian clade in more detail (i.e.…”

“…However, contrary to the scenario of immigration from Asia into Australia, our phylogenies support dispersal out of Australia into Indonesia. This could be concluded from the fact that Rhagada is firmly nested within the Australasian camaenid radiation (Figure 7 in Hugall & Stanisic, ), and based on this, it is most likely to be of Australian origin. Our trees revealed that the Indonesian species have derived from an Australian ancestor and dispersed out of Australia into the Lesser Sunda Islands.…”