Title: Miocene uplift and Pleistocene forest connectivity drove the evolution of large-bodied Afrotropical pill scarabs (Co­leo­ptera: Hybosoridae: Afrocloetus and Congomostes)

Creators: Vasily V. Grebennikov

Accepted on September 17, 2019.

Published online at www.senckenberg.de/arthropod-systematics on December 06, 2019.
Published in print on December 20, 2019.

DOI: 10.26049/ASP77-3-2019-3
PDF/A 6 MB

Published by Senckenberg Gesellschaft für Naturforschung

Date (Publication Year): 2019

Resource Type (General): TEXT

Resource Type (optional): Arthropod Systematics & Phylogeny, Scientific Article

Description: This study targets the post-Oligocene evolution of low-vagility beetles in wet African forests. Two nominal genera of large-bodied pill scarabs form the focus: the East African Afrocloetus with two nominal species and the Central African Congomostes with three nominal species. Both genera are rarely sampled, particularly Afrocloetus which is known until now from two holotypes collected in 1948 and 1957. Long series of Afrocloetus are newly reported from four Tanzanian localities: Kimboza forest, Kaguru, Rubeho and Udzungwa; the last three belong to the biodiverse chain of the Eastern Arc Mountains. A phylogenetic analysis utilized a matrix consisting of 52 terminals (including five Afrocloetus and two Congomostes) and an alignment of 2,940 bp from one mitochondrial and two nuclear fragments. The analysis recovered both genera as monophyletic and forming the sister clade to the Afrotropical Philharmostes group of genera. Molecular clock analysis of 39 DNA barcodes of both genera estimated their separation within a temporal window (13.0 – 6.8 Ma) that is fully concurrent with the Miocene uplift of the East African Plateau causing aridification and forest fragmentation. Three Tanzanian localities each support an endemic mitochondrial Afrocloetus clade evolving in allopatry, following the pre-Pleistocene range breakup of their originally widespread ancestor (= first cycle of forest expansion and contraction). Two morphologically and genetically distinct Afrocloetus clades co-exist in Udzungwa; this sympatry is attributed to secondary re-colonization of Udzungwa by the younger and reproductively isolated clade at 2.4 – 1.2 Ma (= second cycle of forest expansion and contraction). This hypothesised re-colonisation of Udzungwa by flightless beetles coincides with the Pleistocene climatic cycles and suggests temporal connectivity between Rubeho and Udzungwa forests. Adults of Afrocloetus are extensively illustrated, compared among themselves and with those of Congomostes, and their relevant evolutionary markers are discussed. The taxonomy of both nominal and likely synonymous genera is unmodified pending further research. Habitus images, DNA sequences and other supplementary information of all sequenced specimens are available online at dx.doi.org/10.5883/DS-VGDS002 and dx.doi.org/10.5883/DS-VGDS003.

Keywords: DNA barcode, ITS2, 28S, phylogeny, forest litter, phylogeography.

Citation: Grebennikov, V. V. (2019). Miocene uplift and Pleistocene forest connectivity drove the evolution of large-bodied Afrotropical pill scarabs (Co­leo­ptera: Hybosoridae: Afrocloetus and Congomostes). Arthropod Systematics & Phylogeny, 77(3): 417-431. https://doi.org/10.26049/ASP77-3-2019-3