Organisms Diversity & Evolution

, Volume 17, Issue 2, pp 421–445 | Cite as

From Eastern Arc Mountains to extreme sexual dimorphism: systematics of the enigmatic assassin bug genus Xenocaucus (Hemiptera: Reduviidae: Tribelocephalinae)

  • C. Weirauch
  • M. Forthman
  • V. Grebennikov
  • P. Baňař
Original Article


The Eastern Arc Mountains (EAM) have long been recognized as an area of extraordinary endemic biodiversity but have remained understudied compared to other biodiversity hotspots. The tribelocephaline assassin bug genus Xenocaucus China & Usinger, 1949, currently comprises two species known from the Uluguru Mountains of the EAM and Bioko Island in the Gulf of Guinea. Both species are based on single apterous and apparently eyeless female specimens. Based on collections resulting from extensive leaf litter sampling in Tanzania and Ethiopia, we here describe six new species, five based on females (Xenocaucus chomensis, n. sp., Xenocaucus kimbozensis, n. sp., Xenocaucus nguru, n. sp., Xenocaucus rubeho, n. sp., and Xenocaucus uluguru, n. sp.) and Xenocaucus ethiopiensis, n. sp., for which we discovered a macropterous male with well-developed eyes in addition to the apterous females. Molecular phylogenetic analyses indicate that Xenocaucus ethiopiensis, n. sp., is the sister taxon to the Tanzanian clade and support morphology-based species concepts. Divergence dating shows that diversification in the Tanzanian clade started ∼15 mya, with the youngest species-level split occurring ∼8 mya. Three species occur across multiple mountain ranges in the EAM or occur also on Mt. Hanang, and biogeographic analyses suggest a complex history of Xenocaucus in East Africa.


Phylogeny Biogeography Divergence dating Tropical montane forest Biodiversity Afrotropical region 



Thanks to the collection manager at the Museo Civico di Storia Naturale, Genova and Dr. Eric Guilbert at the Muséum national d’Histoire naturelle for the loans of the holotypes of X. mancinii and X. schoutendeni to CW and PB, respectively. We thank Jonathan McGhee, a former undergraduate research student in the Weirauch lab, for assistance with specimen sorting and imaging. Special thanks to Rochelle Hoey-Chamberlain who assisted with specimen measurements and molecular work. Earlier drafts of this manuscript were reviewed by Alex Knyshov and other members of the Weirauch lab and we thank them for their valuable discussions and suggestions. This study was partially supported by the US National Science Foundation grant no. 0933853 (Principal Investigator C. Weirauch) and the University of California, Riverside.

Supplementary material

13127_2016_314_MOESM1_ESM.xlsx (12 kb)
Online Resource 1. Uncorrected pairwise distances for the D2 region of 28S rDNA for species of Xenocaucus; the male of X. ethiopiensis is selected as the reference taxon (XLSX 12 kb)
13127_2016_314_MOESM2_ESM.jpg (232 kb)
Online Resource 2. Divergence dates based on the BEAST2 analysis showing 95% HPDs (JPEG 231 kb)
13127_2016_314_MOESM3_ESM.pptx (9.3 mb)
Online Resource 3. Alternative biogeographic reconstructions for Xenocaucus using BioGeoBEARS and RASP DIVA (PPTX 9525 kb)


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Copyright information

© Gesellschaft für Biologische Systematik 2016

Authors and Affiliations

  1. 1.Department of EntomologyUniversity of CaliforniaRiversideUSA
  2. 2.Entomology and Nematology DepartmentUniversity of FloridaGainesvilleUSA
  3. 3.Canadian Food Inspection AgencyOttawaCanada
  4. 4.Department of EntomologyMoravian MuseumBrnoCzech Republic

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