Data from: 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, especially if a Gondwana vicariance origin is
plausible, and3) to evaluate the utility of the gene CAD (rudimentary) for
phylogenetic analysis in Dytiscidae. Results: Our analyses confirm
Aciliini as monophyletic and Eretini as the sister group, with high
support. All six genera with multiple species are also supported as
monophyletic. The origin of the tribe is firmly based on 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 on all
basal branches as well as for all genera as monophyletic. 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, suggested Wnt and CAD as the most informative of our sampled genes
per base pair.