The evolutionary history of the genus Abax (Coleoptera, Carabidae)

Summary

The genus Abax Bonelli has been revised by means of the “internal sac inflating method”. Seventeen species have been recognized, some of them forming allopatric species groups: A. exaratus with 5 species, A. beckenhaupti with 4 taxonomic units, A. parallelus with 2 units. Most species live on the Alps or in Central Europe: A. pyraeneus is isolated in the Eastern Pyrenees, A. schüppeli on the Carpathian Mountains. Among 15,000 specimens observed, only one hybrid has been found: A. ater Villers × A. parallelepipedus Dejean.

The evolutionary history probably started in lowland forests of the pre-quarternary Central Europe with forms of the plesiomorphic A. carinatus lineage. The more recent species are found in the ater lineage, where nearly all species originated during the Pleistocene, mostly as ende-mites on the ice-free southern slope of the alpine chain.

In the whole genus a clear lowland-mountain gradient is recognizable: the older species are still able to live in lowlands, the younger ones are found only in mountain forests or in primary alpine grasslands (oblongus and beckenhaupti groups).

The same gradient is seen in the size and shape of the larval cerci that seem strictly related to the soil type inhabited.

All speciation patterns can be interpreted as allopatric.

A first synthesis of the evolutionary history of the genus is presented here based on: holomorphological affinity, adult behaviour (parental care), larval behaviour, habitat affinity and reconstruction of distribution, areas.