Phylogeny and historical biogeography of the water boatmen (Insecta: Hemiptera: Heteroptera: Nepomorpha: Corixoidea).

The water boatmen of Corixoidea, a group of aquatic bugs with more than 600 extant species, is one of the largest superfamilies of Nepomorpha. Contrary to the other nepomorphan lineages, the Corixoidea are most diverse in the Laurasian remnant Holarctic region. To explicitly test whether the present-day Holarctic distribution of diverse corixids is associated with the arising of the Laurasian landmass that was separated from Gondwana, we investigated the phylogeny, divergence times and historical biogeography of Corixoidea based on morphological and molecular characters sampled from 122 taxa representing all families, subfamilies, tribes and approximately 54 % of the genera. Our results were largely congruent with the phylogenetic relationships within the established nepomorphan phylogenetic context. The fossil calibrated chronogram, diversification analysis and ancestral ranges reconstruction indicated that Corixoidea began to diversify in Gondwana in the late Triassic approximately at 224 Ma and the arising of the most diverse subfamily Corixinae in Corixidae in the Holarctic region was largely congruent with the time of separation of Laurasia from Gondwana. The large-scale expansion of the temperate and cold zones on the northward-moving Laurasian landmass after the breakup of the Pangea provided new aquatic niches and ecological opportunities for promoting rapid diversification for the Holarctic corixid lineage.

A molecular phylogeny of the pan-tropical pond skater genus Limnogonus Stål 1868 (Hemiptera-Heteroptera: Gerromorpha-Gerridae).

We investigated phylogenetic relationships among pond skaters (Heteroptera: Gerridae) of the genus Limnogonus Stål 1868 by performing separate and combined parsimony analyses of DNA sequences from three mitochondrial (COI+II, 16SrRNA) and one nuclear (28SrRNA) gene(s). The taxon sample represented almost two thirds of the known diversity, and with most taxa represented by two or more individuals. A simultaneous analysis of all data showed that L. luctuosus Montrousier 1865 was paraphyletic and suggests that "L. luctuosus" from Australia and possibly also a population from the Society Islands (Moorea) each represents unrecognized species. L. fossarum F. 1775 was strongly supported, but the two subspecies L. f. fossarum F. 1775 and L. f. gilguy Andersen and Weir 1997 were paraphyletic. The two currently recognized subgenera Limnogonus (s. str.) Stål 1868 and L. (Limnogonoides)Andersen 1975 were paraphyletic, and were accordingly broken up in several monophyletic groups, each containing one or more species. From Limnogonus (s. str.) we delimited five clades: I (comprising L. aduncus Drake & Harris 1933, L. recens Drake and Harris 1934, L. profugus Drake & Harris 1930 and L. ignotus Drake and Harris 1934, all from the Neotropical Region), II (comprising L. nitidus Mayr 1865 from the Oriental Region), III (comprising L. franciscanus (Stål 1859) from the New World and L. cereiventris (Signoret 1862) from the Afrotropical Region), IV (comprising L. hungerfordi Andersen 1975 and L. luctuosus Montrousier 1865 from the Oriental and Australasian Regions) and V (comprising L. fossarum F. 1775 from the Oriental and Australasian Regions). From L. (Limnogonoides) we delimited two clades: VI (comprising L. intermedius Poisson 1941 from the Afrotropical Region and L. pectoralis (Mayr 1865) from the Oriental Region) and VII (comprising L. hypoleucus (Gerstaecker 1873), L. nigrescens Poisson 1941, L. poissoni Andersen 1975, and L. capensis China 1925 from the Afrotropical Region). Finally, L. (s. str.) windi Hungerford & Matsuda 1961 from Australia was placed as sister to clades I-VI. A manual optimization of geographical distribution onto the strict consensus tree suggests that Limnogonus is primarily an Old World group with independent transitions to the New World in L. franciscanus and in the common ancestor of Clade I.