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.

If Dung Beetles (Scarabaeidae: Scarabaeinae) Arose in Association with Dinosaurs, Did They Also Suffer a Mass Co-Extinction at the K-Pg Boundary?

The evolutionary success of beetles and numerous other terrestrial insects is generally attributed to co-radiation with flowering plants but most studies have focused on herbivorous or pollinating insects. Non-herbivores represent a significant proportion of beetle diversity yet potential factors that influence their diversification have been largely unexamined. In the present study, we examine the factors driving diversification within the Scarabaeidae, a speciose beetle family with a range of both herbivorous and non-herbivorous ecologies. In particular, it has been long debated whether the key event in the evolution of dung beetles (Scarabaeidae: Scarabaeinae) was an adaptation to feeding on dinosaur or mammalian dung. Here we present molecular evidence to show that the origin of dung beetles occurred in the middle of the Cretaceous, likely in association with dinosaur dung, but more surprisingly the timing is consistent with the rise of the angiosperms. We hypothesize that the switch in dinosaur diet to incorporate more nutritious and less fibrous angiosperm foliage provided a palatable dung source that ultimately created a new niche for diversification. Given the well-accepted mass extinction of non-avian dinosaurs at the Cretaceous-Paleogene boundary, we examine a potential co-extinction of dung beetles due to the loss of an important evolutionary resource, i.e., dinosaur dung. The biogeography of dung beetles is also examined to explore the previously proposed "out of Africa" hypothesis. Given the inferred age of Scarabaeinae as originating in the Lower Cretaceous, the major radiation of dung feeders prior to the Cenomanian, and the early divergence of both African and Gondwanan lineages, we hypothesise that that faunal exchange between Africa and Gondwanaland occurred during the earliest evolution of the Scarabaeinae. Therefore we propose that both Gondwanan vicariance and dispersal of African lineages is responsible for present day distribution of scarabaeine dung beetles and provide examples.