Microborus camerunus (Eggers, 1919) Eggers, 1919

Jordal, Bjarte H., 2017, Ancient diversity of Afrotropical Microborus: three endemic species - not one widespread, ZooKeys 710, pp. 33-42 : 38-40

Microborus camerunus (Eggers, 1919) stat. n. Figs 7-8, 15-17

Pseudocrypturgus camerunus Eggers, 1919: 236, original description.

Microborus camerunus (Eggers, 1919): synonymized with M. boops Blandford, 1897, by Wood (1982), here resurrected.

Type material examined.

Holotype of Pseudocrypturgus camerunus Eggers (NHMW). Holotype of Microborus boops Blandford (BMNH).

Diagnosis.

Distinguished from M. brevisetosus and M. boops by the smooth and glabrous frons, the glabrous central area of the ventrites, the smooth posterior face of the protibiae, subconfluent strial punctures, and the slightly stouter body shape.

Description

(male and female).Length 1.5 mm, 2.4 × longer than wide. Colour reddish brown, pronotum darker.

Head. Eyes separated above by 0.7 × their width. Frons smooth, shiny and lightly punctured, vestiture consisting of <10 short setae on epistoma and 2 longer setae between eyes.

Pronotum smooth, shiny, with densely placed puntures.

Elytra with striae impressed, punctures deep, subconfluent; interstriae about as broad as striae, with very fine irregularly spaced punctures; postero-lateral (interstrial) rim slightly elevated with 2-3 blunt granules. Vestiture consisting of scattered erect, golden setae on discal interstriae, somewhat shorter on declivity.

Legs. Protibiae with three lateral teeth (embedded denticles), and one additional tooth just above the inner mucro; posterior face smooth.

Ventral vestiture simple, on ventrites consisting of a few irregularly placed short setae close to the lateral margins.

Distribution and biology.

Known from Ghana, Cameroon and Congo. New record: Cameroon, Mt. Cameroon south slope, 1600 m, GIS: [4.12, 9.16], Ficus branch, B. Jordal 28xi-8 [28. Nov. 2007] (ZMBN/ENT_Scol4931, 4941). It was taken together with M. angustus under thick bark of large fallen Ficus tree (see above).

Key to the Afrotropical species of Microborus

Molecular data on Afrotropical species

Gene sequences obtained via PCR are listed by their genbank accession numbers in Table 1. Maximum likelihood and maximum parsimony provided consistent results across analyses, with all nodes maximally supported (Fig. 21). The three Afrotropical species formed a group separate from the single Neotropical species included, M. aberrans . Microborus angustus was furthermore clearly distinct from the sympatric M. camerunus that grouped closely with M. brevisetosus , suggesting a role for allopatric divergence prior to the co-existence of M. angustatus and M. camerunus . Given the limited global scope in this study, it cannot be ruled out that the Afrotropical (or the Neotropical) fauna experienced two origins for this genus.

Despite high morphological similarity, M. brevisetosus and M. camerunus differed by 15.3-16.1 % at COI. An average divergence of 2.4-3.3% at five nuclear loci leave no doubt about each species validity. The largest nuclear variation was found in 28S (3.9%), a substantial difference for morphologically similar taxa (see e.g. Jordal and Kambestad 2014). Guided by the molecular data, a search for consistent morphological differences was found in the frons, elytral declivity and the venter of these beetles. Hence, the overall similarity that has led previous researchers to synonymise M. camerunus with M. boops ( Wood 1982), emphasizes the need for careful consideration of possible semi-cryptic character differences. The low rate of change in morphological characters for the genus as a whole, as documented by the close similarity to the mid-Cretaceous fossil M. inertus Cognato & Grimaldi, 2009 (see Cognato and Grimaldi 2009), makes it advisable to base new synonymies on genetic data and rigorous morphological examination.