Abstract:
The current study is about the evolution and the morphology of dung
beetles, subfamily Scarabaeinae. The study includes the systematics of the
tribe Canthonini and an exhaustive analysis of the morphological variation of
male genitalia including species from the 11 tribes of the subfamily, mainly
Canthonini, Ateuchini, Scarabaeini and Coprini. With the aim to go deep in the
phylogenetic relationships of the tribe Canthonini, the largest of the subfamily
Scarabaeinae, with 91 genera and 875 species, a total of 109 genera, 327
species and 513 specimens were reviewed. The tribe Canthonini is mainly
distributed in Gondwana, with species in America, Africa, Madagascar,
Australia, New Zealand and the Oriental region. Species of the different regions
were included in the detailed examination of male genitalia as well in the
cladistic analysis using morphological characters.
Strong evidence of a need for sub-division of Canthonini in natural
groups, morphologically and ecologically more solid groups, is one of the main
results obtained. Three tribes are proposed, the tribe Byrrhidiini (Byrrhidium,
Dicranocara, Namakwanus, and Versicorpus), tribe Circelliini (monotypic genus
Circellium), and the tribe Canthonini, firstly with the American genera (Canthon,
Malagoniella, Megathopa, Megathoposoma, Eudinopus, Canthonidia,
Tetraechma, Anisocanthon, Melanocanthon, Sylvicanthon, and Hansreia), as
well as the African genera Gyronotus and Anachalcos. Genera from
Madagascar, Australia and the Oriental region should be treated in separate
analyses, and probably the pre-established tribes such as Panelini, Epilissini
and Mentophilini, could acquire validity in the context of a new classification for
these groups currently in Canthonini.
The phylogeny of the genus Epirinus and description of six new species
is also presented. Epirinus is a monophyletic group, although by morphological
differences, is not considered under the tribe Canthonini. Equally the genus
Deltochilum is not considered as part of the tribe Canthonini, since in the
phylogenetic analysis of American genera, Deltochilum appear polyphyletic, and this genus deserves a more detailed analysis of its systematics and
classification.
Patterns of variation in the genitalia structures, mainly the sclerites, were
useful in species separation and to define genera. However, the patterns were
not so suitable in setting the limits of the tribes. To date, taxonomists have been
trying to fit the whole range of variation in species and genera into a preestablished
and limited Scarabaeinae tribal classification. Based on this study
the recommendation for a better understanding of the evolutionary history, and
to improve the taxonomic classification of the tribe Canthonini and the
Scarabaeinae dung beetles, is to study in detail each group, in morphological,
molecular and even ecological and biogeographical aspects. Information from
these different approaches, will help to establish the borders for the tribes, and
therefore to have more accurate classifications.
