Agabus austellus Englund, Bilton & Bergsten, 2020

Englund, William F., Njoroge, Laban, Bistroem, Olof, Miller, Kelly B., Bilton, David T. & Bergsten, Johannes, 2020, Taxonomic revision of the Afrotropical Agabus raffrayi species group with the description of four new species (Coleoptera, Dytiscidae), ZooKeys 963, pp. 45-79 : 45

publication ID	https://dx.doi.org/10.3897/zookeys.963.53470
publication LSID	lsid:zoobank.org:pub:9636C9F2-C6BD-4B34-BCC6-ED214C7B0D19
persistent identifier	https://treatment.plazi.org/id/290F05EF-3F4E-4971-B957-1071B64FBD13
taxon LSID	lsid:zoobank.org:act:290F05EF-3F4E-4971-B957-1071B64FBD13
treatment provided by	ZooKeys by Pensoft
scientific name	Agabus austellus Englund, Bilton & Bergsten
status	sp. nov.

Treatment

Agabus austellus Englund, Bilton & Bergsten sp. nov. Figures 1 View Figure 1 , 5D View Figure 5 , 6A-D View Figure 6 , 7B View Figure 7 , 8G View Figure 8 , 9A-D View Figure 9 , 11L View Figure 11 , 11P View Figure 11 , 12 View Figure 12 , 13 View Figure 13 , 14 View Figure 14 , 16 View Figure 16 , 17 View Figure 17

Type locality.

South Africa, Western Cape Province, Tributary stream to Keurboom river crossing R339 road, 33.8612S, 23.1729E, 250 m (Fig. 16 View Figure 16 ).

Type material.

Holotype ♂ (AMG) labelled: "South Africa W Cape Province Tributary stream to Keurboom river x-ing R339. 33.8612S, 23.1729E, 250m. Foreststream with gravel and veg. At edges RSA15-21 13.XII.2015 Leg. J. Bergsten & A. Désamoré”. Paratypes: 1 ♂ (NHRS) labelled: "South Africa E Cape Province. Small fish river x-ing road r337, NW of Somerset East. 32.5913S, 25.4510E, 1017m. Waterpools in streambed RSA15-27 15.XII.2015 Leg. J. Bergsten & A. Désamoré”; paratypes 1 ♂ (NHRS) labelled: "Rep. South Africa, W. Cape Gydo Pass at junc R303 & Witzenberg Valley Rd. Aug. 25, 2004 G. Challet"; paratypes 6 ♂ 2 ♀ (MZLU) labelled: "S. Afr. Cape Prov., Swartbergpas, Platberg, Alt.: ab. 5000 ft., 5-6.I.51 No. 120", "Swedish South Africa Expedition 1950-1951, Brinck-Rudebeck", " Agabus ruwenzoricus Guignot, det AN Nilsson 1990", one male and one female had an extra label containing " Agabus raffrayi sharp, Det. J. Omer-Cooper"; paratypes 2 ♂ 3 ♀ (MfN) labelled: "R.S.Africa 17.xi.1997 32°15.3'S, 22°29.9'E Cape Province:Karoo NP. Swamp at Puttersvlei, swamp vegetation treating, watercatcher, lg. M.Uhlig+J.Ndamane", one male had an extra label containing " Agabus ruwenzoricus Guignot det. K.B. Miller 1999"; paratypes 2 ♂ 3 ♀ (AMG, CBP) labelled: "Sept. 2002 South Africa WC Pools beside Brée River below Mitchell’s Pass, Ceres. D T Bilton leg."; paratypes 4 ♂ 1 ♀ (CBP, ZSM) labelled: "24/ix/2009 South Africa WC Groote Swartberg stream on R328 1 km N of De Top, on N side of pass. D.T. Bilton leg."; paratypes 1 ♂ 1 ♀ (CBP) labelled: "20/ix/2014 South Africa WC Gifberg - stream in Gifberg Pass above Vanrhynsdorp rocky stream. D T Bilton leg."; paratype 1 ♂ (CBP) labelled: "11/ii/2017 South Africa WC Harkerville Forest pool 1 survey site 16. M Bird & D T Bilton leg."; paratypes 6 ♂ 6 ♀ dry mounted, 18 ♂ 16 ♀ in ethanol (AMG, CBP, NHRS) labelled: "28/v/2018 South Africa KZN Drakensberg - river nr. Sentinel Peak 28°45'30.80"S, 28°54'14.82"E 2960m M. Mlambo leg."; paratype 1 ♀ (IBE) labelled: "25/viii/2008 South Africa WC Gydo Pass - pool at Jnct. R303 & Witzenberg Valley Rd. G Challet leg."; paratypes 1 ♂ (IBE) labelled: "2/x/2010 South Africa WC Cederberg Dwarsrivier 32°30'59.51"S, 19°21'E 735 m Hidalgo-Galiana & Kleynhans leg."; paratypes 1 ♂ (CBP) labelled: "6/x/2015 South Africa NC Bokkeveld, Avontuur - stream below Fynbos Cottage D T Bilton leg."; paratypes 4 ♂ 3 ♀ (CBP, ISAM, SANC) labelled: "22/ix/2010 South Africa WC Gydo Pass stream along Witzenberg Valley road ca 1 km SW of Jnct. with R303 985 m D T Bilton leg.".

Diagnosis.

Most similar to A. riberae sp. nov. and A. agulhas sp. nov., but distinguishable by a combination of having a scutellum darker than or as dark as elytra, base of aedeagal subapical tooth lacking a distinct incurvation (compare Fig. 8G, I View Figure 8 ) and a relatively narrow metasternal wing (see Table 1 View Table 1 ). The pronotal hypomeron is not visible in strict lateral view, the aedeagus does not have a prolonged subapical portion and in ventral view its apex is asymmetrically curved. The discal elytral microreticulation of most specimens is dominated by relatively small, isodiametric meshes.

Description.

Habitus as in Fig. 11L, P View Figure 11 .

Colour: Head black, with rufous interocular spots; some specimens with an additional anterior rufous area. Pronotum rufopiceous to black. Elytra rufopiceous to black. Ventral surface rufous to black; testaceous lines on abdominal segments rarely present; hypomeron and epipleuron rufopiceous to rufous. Legs rufous to rufopiceous. Antennae and palpi testaceous.

Microreticulation : Relatively fine on both pronotum and elytra, and rather similarly impressed in both sexes. The microreticulation of the elytral disc is dominated by relatively small, somewhat isodiametric meshes in most specimens examined (e.g. Fig. 9B, C View Figure 9 ), although this character does vary somewhat between populations in this relatively widespread species (see Fig. 9 View Figure 9 ). In particular, the male from Harkerville Forest (see Fig. 9D View Figure 9 ) has a reticulation composed of much larger meshes than seen in other material of this species. This specimen conforms to A. austellus sp. nov. on other morphological characters, and COI sequence data (I. Ribera, pers. comm.).

Structural features : Body length: 6.80-8.40 mm (see Table 1 View Table 1 ). Hypomeron marginally visible in strict lateral view, lateral bead of pronotum narrow and well defined. Metasternal wing narrow, WC/WS 3.1 or more in both males and females (see Table 1 View Table 1 and Fig. 12 View Figure 12 ). Pronotum broad, more than twice as broad as interocular distance (see Table 1 View Table 1 and Fig. 13 View Figure 13 ).

Legs: Protarsal claws long,> 1.6 × as long as protarsomere 4 in most specimens (see Table 2 View Table 2 & Fig. 14 View Figure 14 ). Metatarsomeres usually short and broad; metatarsomere 2 <1.8 × as long as broad in most specimens (see Table 2 View Table 2 ), metatarsomere 5 <3.3 × as long as broad in most specimens (see Table 2 View Table 2 ).

Male genitalia: Aedeagus lack the prolonged section between the subapical broadening and the apical and subapical teeth present in some species in the group (see Fig. 8G View Figure 8 ). In ventral view the apex is asymmetrically curved (Fig. 7B View Figure 7 ). There is some variation in the shape and size of the subapical tooth of the aedeagus (Fig. 6A-D View Figure 6 ), this being relatively small in most populations (Fig. 6A-C View Figure 6 ).

Female: Externally similar to males. Some specimens with dorsal microreticulation slightly more strongly impressed.

Distribution.

Republic of South Africa, where the species is relatively widespread, from the Bokkeveld Plateau in the south of the Northern Cape Province, most mountain systems of the Western Cape Province and east along the Great Escarpment to the Drakensberg (see Fig. 1 View Figure 1 ). This wide geographical range encompasses winter, summer and bimodal rainfall regimes.

Ecology.

Found in streams, pools beside streams and remnant pools in seasonal running watercourses. Most localities are situated in Fynbos or alpine grassland (e.g., Fig. 17 View Figure 17 ), but also recorded from densely forested streams. Sites span a wide range of altitudes, from the type locality at 250 m (Fig. 16 View Figure 16 ) to almost 3000 m in the Kwazulu-Natal, Drakensberg (Fig. 17 View Figure 17 ), most being at intermediate elevations.

Etymology.

The name refers to the fact that the species is widespread in South Africa and therefore truly an Agabus of the south (Latin: austellus = southern parts).

Comments.

Nilsson (1992a) and Omer-Cooper (1965) assigned specimens from South Africa and S. Rhodesia [=Zimbabwe] to A. ruwenzoricus . We have studied one series of specimens cited by both authors from the Swartberg Pass (Swartbergpas) W. Cape Province, housed in Lund (MZLU), which correspond to A. austellus sp. nov. Males of this species do not have a prolonged preapical section of the aedeagus, a distinguishing character not previously noted in the raffrayi group. It seems likely that all previous records of A. raffrayi , A. pallidus or A. ruwenzoricus from South Africa, and also possibly those from Zimbabwe, are misidentified and mostly refer to A. austellus sp. nov. This species is somewhat variable in body shape, elytral microreticulation (see Fig. 9A-D View Figure 9 ) and the shape and size of the subapical tooth of the aedeagus (see Fig. 6A-D View Figure 6 ). We interpret this variation as comprising a single species, however, particularly given the very similar mtDNA COI sequences observed amongst populations spanning the entire known range in South Africa (i.e., Bokkeveld Plateau to Drakensberg, I. Ribera, pers. comm.).