Riberazantaena grebennikovi (Perkins, 2009) Bilton, 2021

Bilton, David T., 2021, Riberazantaena, a new hydraenid genus from the Eastern Arc Mountains of Tanzania (Coleoptera, Hydraenidae), Zootaxa 4999 (6), pp. 573-581 : 577-578

Riberazantaena grebennikovi comb. nov.

( Figs. 1A , 2C , 3 & 4B )

Protozantaena grebennikovi Perkins, 2009: 47 .

Material examined: 4♂, 2♀ “ TANZANIA, Uluguru Mts. // at Tchenzema vil.// S07°07’19” E037°37’16”,// 7.xi.2010, 2429m,// sifting09, V.Grebennikov ” ; 3♂ “ TANZANIA, W. Usamba-// ra Mts., Mazumbai For.,// S4.82634° E38.49690°,// 1860m, 12.i.2013, sift46,// V.Grebennikov ” ; 3♂ “ TANZANIA, Rubeho Mts. // at Ipondelo vil.// 6°50’20”S 36°34’32”E,// 21.xii.2011, 1875m,// sift.10, V.Grebennikov ” ( CBP, CNC, NMW)

Variation and biogeography. Populations of these beetles have been sampled from three separate mountain forests in the Eastern Arcs: West Usambara Mountains, Uluguru Mountains and Rubeho Mountains ( Fig. 4B ). The first two of these also provided specimens included by Perkins (2009) in the type series. Whilst there are some differences between individuals from these populations in the shape of the apical expansion of the main piece (see Fig. 3 ), this character is also somewhat variable within a single sample, and not consistently diagnostic. Externally, beetles from these different forests do not differ consistently either. Despite this, the late Ignacio Ribera (pers. comm.), noted significant mitochondrial COI divergence between populations, suggesting relatively long-term isolation in montane forest ‘islands’. This isolation does not appear to have resulted in significant fixation of divergent morphological characters, however, and so I retain populations from all three mountain systems within R. grebennikovi . Grebennikov (2019) describes a remarkably similar situation in some Eastern Arc Afrocloetus Petrovitz, 1968 pill scarabs, in which distinct, allopatric mitochondrial clades are in some cases morphologically identical. It is interest- ing to note that there is much greater geographical distance between populations of R. grebennikovi than between the northernmost populations of this species and R. latissima sp. nov. in the South Pare Mountains. All specimens examined were micropterous, in contrast to the observations of Perkins (2009).

Differential diagnosis. For characters allowing separation from Riberazantana latissima sp. nov., see under that species below.

Figures

FIGURE 1. Habitus images of A) Riberazantaena grebennikovi, Uluguru Mountains, Tanzania; B) Riberazantaena latissima sp. nov., Chome Forest, South Pare Mountains, Tanzania. Scale bar = 1 mm.

FIGURE 2. Aedeagi of A) Protozantaena labrata, modified from Perkins (2009); B) Protozantaena palpalis, modified from Perkins (2009); C) Riberazantaena grebennikovi, Uluguru Mountains, Tanzania; D) Riberazantaena latissima sp. nov., Chome Forest, South Pare Mountains, Tanzania. Scale bar = 0.1 mm. Note that the flagella of P. labrata and Riberazantaena spp. are flexible, meaning that curvature etc. is not diagnostic.

FIGURE 3. Riberazantaena grebennikovi, variation in apex of main piece, ventral view A) Uluguru Mountains; B) Rubeho Mountains; C) Usambara Mountains. Scale bar = 500 µm.

FIGURE 4. A) Chome Forest, South Pare Mountains, Tanzania, type locality of Riberazantaena latissima sp. nov. Photo Vasily Grebennikov; B) Map of East Africa showing known localities of Riberazantaena species. Red symbol = R. grebennikovi; blue symbol = R. latissima sp. nov.