Diplotrichus acutior, Jordal, 2021

Jordal, Bjarte H., 2021, An integrated taxonomic revision of Diplotrichus (Coleoptera, Scolytinae) supports a Malagasy origin and single colonisation of South Africa, Zootaxa 5047 (2), pp. 101-122 : 102-103

Diplotrichus phylogeny and biogeography

The maximum likelihood analysis of the concatenated gene sequences resulted in a tree topology with Diplotrichus minor ( Schedl, 1950) as sister to the remaining species in the genus ( Fig. 7 ). This species is the only one with a dorsal spike on the female scapus. Species with a faint to strong apical expansion of the elytra formed the next group consisting of Diplotrichus acutior sp. nov. and Diplotrichus falcatus sp. nov. These were sister to a clade consisting of two equally well supported groups. One group contained all South African species, including the type species Diplotrichus gracilis ( Schedl, 1958) . The other group contained only Malagasy species such as Diplotrichus catenatus ( Schedl, 1953) . Relationships within these two clades received lower support.

Analyses of individual genes revealed fairly similar results, varying in the position of D. acutior and D. falcatus . Occasionally, these two species formed either a grade separating D. minor and the remaining taxa or formed the sister group to the South African species. In all cases the South African species were deeply nested within an assembly of Malagasy species.

The phylogenetic analysis adds additional evidence to a Malagasy origin of South African Diplotrichus . The South African taxa that were analysed with molecular data are morphologically fairly similar to each other ( Figs 8– 24 ) and this clade was nested deeply within a grade of Malagasy species. This clearly documents a case of overseas dispersal in the direction from Madagascar to South Africa. The timing of this event cannot be dated precisely given the large difference between stem and crown age for the South African clade. A new Beast analysis with D. acutior and D. falcatus added to the data matrix provided estimates similar to Jordal (2021b), in the range from 29 (stem) to 14.5 (crown) Ma for the South African clade. This estimate extends over both sides in the Oligocene–Miocene transition; the Miocene recolonisation (of Africa) hypothesis is therefore only partly supported. Irrespective of the exact timing and process of the South African diversification, this genus provides yet another piece of evidence for Madagascar’s important historical role in fostering additional diversity in the Afrotropical region.

Figures

FIGURE 7. Maximum likelihood tree topology for Diplotrichus based on nucleotides from five gene fragments. Node support values from 100 bootstrap replicates are shown on branches.

FIGURES 8–14. Dorsal, lateral, and front view of Diplotrichus gracilis female (8, 10, 12) and male (13), and Diplotrichus widdringtoniae paratype (9, 11, 14).

FIGURES 15–24. Dorsal, lateral, and front view of Diplotrichus pilifrons sp. nov. female holotype (15, 18, 21) and male allotype frons (22), Diplotrichus calvifrons sp. nov. female holotype (16, 19, 23), and Diplotrichus medius sp. nov. female holotype (17, 20, 24).