Contributions to Zoology, 86 (1) – 2017Isabel T Hyman; Irantzu de la Iglesia Lamborena; Frank Köhler: Molecular phylogenetics and systematic revision of the south-eastern Australian Helicarionidae (Gastropoda, Stylommatophora)
Discussion

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Species distributions

Southeastern Australian helicarionids exhibit varied distributional patterns. We have found very broad ranges of up to 500 km in Mysticarion and 750 km in Ubiquitarion (although Ubiquitarion is thought to be introduced into the southern part of its range, and its natural range is probably closer to 400 km; Stanisic, pers. comm.). Species belonging to both genera are arboreal and when not actively crawling, sit in a resting posture on the underside of leaves. They are likely to be subjected to greater passive dispersal by wind than litter-dwelling species, such as Brevisentis. While M. hyalinus is allopatric with respect to its congeners, the other three species of Mysticarion are sympatric throughout much of their range. There is some evidence that M. porrectus inhabits higher altitude, moister areas and may not occur in micro-sympatry with the others; however, M. obscurior and M. insuetus have indeed been collected from the same locality. These two species are not sister taxa in the phylogenetic tree and their sympatry is probably secondary.

In contrast, the semi-arboreal taxa Peloparion and Cucullarion have relatively narrow ranges of around 30-50 km in diameter. Peloparion helenae lives under bark on trees or under grass (Stanisic et al., 2010). Cucullarion generally rests in the base of palm fronds or in leaf litter, only crawling on palm fronds and trunks during rain. Both are less prone to passive dispersal by wind than fully arboreal species. In addition, both groups have a high degree of shell reduction and may be more susceptible to desiccation, rendering them rather poor dispersers.

The litter-dwelling taxa Brevisentis and Parmavitrina also exhibit restricted distributions, with ranges of about 30 km (B. kaputarensis) up to about 300 km (B. atratus, P. planilabris, P. rubrica).