Tip-dated phylogeny of whirligig beetles reveals ancient lineage surviving on Madagascar.

The temporal origin of Madagascar's extraordinary endemic diversity is debated. A preference for Cenozoic dispersal origins has replaced the classical view of Mesozoic vicariance in the wake of molecular dating. However, evidence of ancient origins is mounting from arthropod groups. Using phylogenetic 'tip-dating' analysis with fossils, we show that a whirligig beetle species, Heterogyrus milloti, inhabiting forest streams in southeastern Madagascar is the last survivor of a once dominant and widespread Mesozoic group. With a Late Triassic to Early Jurassic origin (226-187 Ma) it is the hitherto oldest dated endemic lineage of animal or plant on Madagascar. Island biotas' sensitivity to extinction is well known, but islands can also provide refuge from continental extinction. Heterogyrus milloti is an irreplaceable link to the freshwater biota of the Mesozoic and serves as a reminder of what may be lost without critical conservation efforts on Madagascar.

In or out-of-Madagascar?--Colonization patterns for large-bodied diving beetles (Coleoptera: Dytiscidae).

High species diversity and endemism within Madagascar is mainly the result of species radiations following colonization from nearby continents or islands. Most of the endemic taxa are thought to be descendants of a single or small number of colonizers that arrived from Africa sometime during the Cenozoic and gave rise to highly diverse groups. This pattern is largely based on vertebrates and a small number of invertebrate groups. Knowledge of the evolutionary history of aquatic beetles on Madagascar is lacking, even though this species-rich group is often a dominant part of invertebrate freshwater communities in both standing and running water. Here we focus on large bodied diving beetles of the tribes Hydaticini and Cybistrini. Our aims with this study were to answer the following questions 1) How many colonization events does the present Malagasy fauna originate from? 2) Did any colonization event lead to a species radiation? 3) Where did the colonizers come from--Africa or Asia--and has there been any out-of-Madagascar event? 4) When did these events occur and were they concentrated to any particular time interval? Our results suggest that neither in Hydaticini nor in Cybistrini was there a single case of two or more endemic species forming a monophyletic group. The biogeographical analysis indicated different colonization histories for the two tribes. Cybistrini required at least eight separate colonization events, including the non-endemic species, all comparatively recent except the only lotic (running water) living Cybister operosus with an inferred colonization at 29 Ma. In Hydaticini the Madagascan endemics were spread out across the tree, often occupying basal positions in different species groups. The biogeographical analyses therefore postulated the very bold hypothesis of a Madagascan origin at a very deep basal node within Hydaticus and multiple out-of-Madagascar dispersal events. This hypothesis needs to be tested with equally intense taxon sampling of mainland Africa as for Madagascar.

The utility of CAD in recovering Gondwanan vicariance events and the evolutionary history of Aciliini (Coleoptera: Dytiscidae).

BACKGROUND: Aciliini presently includes 69 species of medium-sized water beetles distributed on all continents except Antarctica. The pattern of distribution with several genera confined to different continents of the Southern Hemisphere raises the yet untested hypothesis of a Gondwana vicariance origin. The monophyly of Aciliini has been questioned with regard to Eretini, and there are competing hypotheses about the intergeneric relationship in the tribe. This study is the first comprehensive phylogenetic analysis focused on the tribe Aciliini and it is based on eight gene fragments. The aims of the present study are: 1) to test the monophyly of Aciliini and clarify the position of the tribe Eretini and to resolve the relationship among genera within Aciliini, 2) to calibrate the divergence times within Aciliini and test different biogeographical scenarios, and 3) to evaluate the utility of the gene CAD for phylogenetic analysis in Dytiscidae. RESULTS: Our analyses confirm monophyly of Aciliini with Eretini as its sister group. Each of six genera which have multiple species are also supported as monophyletic. The origin of the tribe is firmly based in the Southern Hemisphere with the arrangement of Neotropical and Afrotropical taxa as the most basal clades suggesting a Gondwana vicariance origin. However, the uncertainty as to whether a fossil can be used as a stem-or crowngroup calibration point for Acilius influenced the result: as crowngroup calibration, the 95% HPD interval for the basal nodes included the geological age estimate for the Gondwana break-up, but as a stem group calibration the basal nodes were too young. Our study suggests CAD to be the most informative marker between 15 and 50 Ma. Notably, the 2000 bp CAD fragment analyzed alone fully resolved the tree with high support. CONCLUSIONS: 1) Molecular data confirmed Aciliini as a monophyletic group. 2) Bayesian optimizations of the biogeographical history are consistent with an influence of Gondwana break-up history, but were dependent on the calibration method. 3) The evaluation using a method of phylogenetic signal per base pair indicated Wnt and CAD as the most informative of our sampled genes.

Taxonomic revision of Madagascan Rhantus (Coleoptera, Dytiscidae, Colymbetinae) with an emphasis on Manjakatompo as a conservation priority.

We review the diving-beetle genus Rhantus Dejean of Madagascar (Coleoptera, Dytiscidae, Colymbetinae) based on museum collection holdings and recently collected expedition material. Both morphology and DNA is used to test species boundaries, in particular whether newly collected material from the Tsaratanana mountains in the north represent a new species or are conspecific with Rhantus manjakatompo Pederzani and Rocchi 2009, described based on a single male specimen from the central Ankaratra mountains. DNA of the holotype of R. manjakatompo was successfully extracted in a non-destructive way and sequenced. The general mixed Yule coalescent model applied to an ultrametric tree constructed from mitochondrial cytochrome c oxidase subunit I (COI) sequence data delimited three species. Morphological characters supported the same species unambiguously. We therefore recognise three species of Rhantus to occur in Madagascar: R. latus (Fairmaire, 1869), R. bouvieri Régimbart, 1900 and R. manjakatompo Pederzani and Rocchi, 2009. All three species are endemic to Madagascar and restricted to the highlands of the island. Rhantusstenonychus Régimbart, 1895, syn. n., is considered a junior synonym of R. latus. We designate lectotypes for R. bouvieri and R. goudoti Sharp, 1882, the latter a junior synonym of R. latus. We provide descriptions, a determination key, SEM-images of fine pronotal and elytral structures, distribution maps, habitus photos, and illustrations of male genitalia and pro- and mesotarsal claws. We discuss the role of the Manjakatompo forest as a refugium for Madagascan Rhantus diversity and other endemics of the montane central high plateau.