The ground beetle genus Casnoidea Castelnau: Taxonomy, phylogeny and zoogeography (Insecta : Coleoptera : Carabidae : Odacanthinae)

Abstract

On the basis of morphological characters of adults, the odacanthine genus Casnoidea Castelnau is reviewed and a key to the species is provided. Of the 17 species, seven are described as new: Casnoidea celebensis, sp. nov., from Sulawesi, C. ceylonica, sp. nov., from Sri Lanka, C. leytensis, sp. nov., from Leyte (Philippines), C. australica, sp. nov., and C. storeyi, sp. nov., both from northern Australia, C. malickyi, sp. nov., from northern Thailand and C. brandti, sp, nov., from Bougainville (Solomon Islands). The first five species are closely related to the widespread Oriental species C. interstitialis (Schmidt-Göbel), C. malickyi is related to the Oriental species C. nigrofasciata (Schmidt-Göbel), and C. brandti is closely related to the Papuan C. gestroi (Maindron). An Australian record of the Oriental species C. indica (Thunberg) indicates an accidental introduction. For the Australian species C. puncticollis and C. thouzeti new records show more extensive ranges than known previously. C. thouzeti (Castelnau) is also a new record from New Guinea.

For C. foersteri (Bouchard) a new subgenus Procasnoidea, subgen. nov., is erected because of certain aberrant and presumably plesiomorphic external and genitalic characters present in this species.

On the basis of the cladistic method as proposed by Hennig, a phylogenetic and biogeographic analysis shows that Casnoidea is a young, highly evolved genus that probably originated in the so-called 'Sundaland'. Apart from some rather primitive species or dibasic species-groups (C. gestroi-group, C. puncticollis, C. indica, C. thouzeti) the subgenus Casnoidea s. str. is divided into two more diverse species groups, namely the nigrofasciata-group with C. nigrofasciata, C. bakeri, C. bhamoensis and C. malickyi, and the interstitialis-group with C. interstitialis, C. ishiii, C. celebensis, C. ceylonica, C. leytensis, C. storeyi and C. australica. Both groups combine closely related species that apparently have been derived from the same stocks with the widespread C. nigrofasciata and C. interstitialis, respectively, and the species have mostly rather restricted ranges at or beyond the margins of the range of the wide-ranging species. Phylogenetical and chorological evidence reveals that several evolutionary events occurred within the genus and that Wallace's line was probably crossed six times independently in easterly direction by the gestroi-, puncticollis-, indica and thouzeti-stocks and within the nigrofasciata- and interstitialis-groups. The Papuan and Australian subregions have been colonised by different stocks and the shared species may have colonised New Guinea rather recently from the south. For Australia at least three independent immigrations of Casnoidea species from the Oriental region are postulated, namely by the thouzeti-, puncticollis- and australica-storeyi-lineages.