Ropalidia aethiopica ( DU BUYSSON 1906 ), 1918

Ropalidia aethiopica ( DU BUYSSON 1906) View in CoL

Icaria aethiopica DU BUYSSON 1906

Ropalidia aethiopica ssp. bimaculata GIORDANI SOIKA 1981 View in CoL , syn. nov.

Type material. Nominal form. A male and a female specimen are deposited in the MNHN. The species description does not describe the exact type status, leading Carpenter to consider them as syntypes (J. M. Carpenter, 1999); the type designation was later made by Kojima (J. Kojima, 2001), who assigned the male status as lectotype and female status as paralectotype. Both specimens are in good condition .

Subspecies. Giordani Soika described ssp. bimaculata based on two females and a male deposited in the ZSM. The main features include extensive yellow colour markings, especially a thick yellow line on the pronotum, a thicker band on T2 and a large bilateral yellow spot on propodeum, without any trace of the inferior propodeal carina ( Figure 36 View FIGURE 36 cc). The examination of the entire series of specimens based on genetics suggests that the yellow spots are occurring in three separate genetic lineages ( BOLD: ADR6945 , ACH1101 View Materials and ADR2619). Additionally , two specimens from these BINs do not have any trace of yellow markings on the propodeum. Lastly , a few members of the other BINs of this cluster also have yellow spots on the propodeum (smaller, but present, even smaller yellow spots under substantially developed inferior carina). Three series of specimens from Kenya with the same collection data include specimens with or without yellow spots, suggesting that this feature might not have taxonomic value and represent a variation of the colour pattern. Finally, the sympatric occurrence of nominal form and subspecies is not possible, leading to the decision to refer the subspecies to the nominal form .

Comments. This is a complex of multiple genetic and morphologic clusters, which show some overlap among themselves, but also with R. puncta (FABRICIUS) stat. rev. The key features of both taxa include the lack of inner orbit punctures, developed median carina of scutellum and a dark apical spot in contrast to the more lightly coloured stigma. These two species show an interesting sympatric-allopatric disagreement; specimens from the allopatric regions of their distribution do not provide substantial problems in separation. However, the overlap zone between them is marked by numerous combinations and a challenging situation, causing substantial separation problems in some specimens.

Analysis of the puncta-aethiopica-complex. Morphological features and colour patterns suggest four colour clusters of R. aethiopica (DU BUYSSON) :

a) Nominal cluster; the typical colour form, characterized by the brown-greyish basal colour, silvery pubescence on the frons, moderately developed or undeveloped inferior propodeal carina, black antenna and black tarsi. Specimens from Western Africa can have a reduced amount of black on the antenna and tarsi, resembling R. guttatipennis (DE SAUSSURE) . In contrast, specimens from Zambia to Kenya have more developed inferior propodeal carina ( Figure 31 View FIGURE 31 bb), a feature shared with the pale cluster (see later). Genetic analysis revealed that this cluster includes five separate BINs (BOLD:ADN2737, ADO5117, ADO2809, ACH1224 and ADR2619) and two more lineage clusters without BIN assignment (Supplementary Figure 24 View FIGURE 24 ).

b) Red cluster; basal body colour is reddish, and the markings on the body are whitish in both males and females. This cluster was recorded from Uganda; all examined specimens were older, therefore, no sequencing was attempted. Also, specimens from this cluster were substantially smaller than the nominal cluster on average (Supplementary Figure 25 View FIGURE 25 ).

c) “ bimaculata ” cluster, a former subspecies cluster, is characterized by more yellow markings on the body (thick yellow line on pronotum, thick band on T2 and two spots on propodeum). This cluster is sympatric to both nominal and pale clusters, in the most diverse region for this entire species, Southern Kenya and Northern Tanzania. Specimens from this cluster belong to three genetic lineages (BOLD:ACH1101, BOLD:ADR2619 and ADR6945).

d) Pale cluster, characterized by the black upper side of the antenna, intermediately developed inferior propodeal carina and ferruginous tarsi; markings on the body are pale whitish, and females have more yellow on the head (brown spot on clypeus is almost entirely bordered by yellow). This cluster is present from Kenya to South Africa and shares genetic lineage with the “bimaculata” cluster (BOLD:ADR6945).

In addition, there were three clusters of a very similar species, R. puncta (FABRICIUS) stat. rev. The first is characterized by the wider head and mesosoma, yellowish basal body colour, longer golden pubescence and a mainly yellow face in females (similar to the nominal form). This cluster is the commonest Ropalidia species in South Africa and extends north towards Zimbabwe and Malawi. The second cluster has shorter pubescence, a leaner body and a darker basal colour, with most examined specimens coming from the Eastern parts of the South Africa. These two clusters share genetic lineages (BOLD:ADN4162, ADO2931). Finally, a third cluster corresponds to the former taxon R. cariniscutis , from Kenya and Tanzania (Supplementary Figure 24 View FIGURE 24 ). The general appearance of this cluster is similar, with a darker antenna (but still not black) and traces of silvery setae on the frons, especially in males. This cluster is also present in Zanzibar, where it is sympatric with the nominal form of R. aethiopica (DU BUYSSON) .

One of the most interesting features of the entire distribution of these two species is a substantial similarity of male morphology, especially in the anatomical parts that are commonly species-specific, such as the shape of the clypeus and the terminal flagellomere. The second important problem is the nested position of all three genetic R. puncta (FABRICIUS) stat. rev. genetic lineages within R. aethiopica (DU BUYSSON) . This might suggest a degree of hybridization in the sympatric regions. Such events would have to be more prevalent in the contact regions, and morphological similarities do seem to follow this pattern. The extreme distribution area of both species (western parts of South Africa vs Yemen) have relatively uniform populations of either species, without specimens that could cause taxonomic problems. The areas between them, from Namibia, Zambia to Kenya and Tanzania, seem to be where hybridization might occur, introducing much greater diversity and causing taxonomic uncertainties. The definitive answer requires further confirmation through more detailed sequencing with multiple genetic markers.

Nest. Several nests were seen on iNat; all seem somewhat irregular, with an intermediate size of both the nest and the colony. Cell wall colouring varies from relatively light greyish-brown to darker grey (iNat:14682014, 40119082, 41128729). Two nests with male and female wasps collected confirmed this: an irregular shape, uneven cell length, and light-greyish opercula with or without nodules.

Similar species. Some specimens of R. aethiopica (DU BUYSSON) have a very shallow propodeal excavation, in which case they may resemble R. africana (CAMERON) stat. rev.; separation of these two species can be made by observing the shape of clypeus in females, which is elongated and pentagonal, with straight upes in R. africana (CAMERON) stat. rev. Specimens of R. aethiopica (DU BUYSSON) from Western Africa ( Cote d’Ivoire to Cameroon) have another peculiar feature. Females from this region are similar to R. guttatipennis (DE SAUSSURE) , primarily reflected in an almost identical body colouration pattern. Their wings have a brownish apical spot (instead of black), yellow markings on the body become intensely yellow, and the basal body colour becomes browner (as opposed to greyish in most other specimens). This pattern was seen on specimens from two museum collections, suggesting it is not an artefact of specimen preservation. In one of these, genotyping has confirmed the existence of two genetic lineages in otherwise very similar morphological specimens. In this situation, the only reliable separation feature is the inner orbit punctures in females, despite an uncannily similar colour pattern. Additional support may arise from the basal body colour—it always has a greyish tone in R. aethiopica (DU BUYSSON) , while R. guttatipennis (DE SAUSSURE) has either brownish or even dark brown basal colour (close to black), without greyish tone to it, while the pattern of yellow markings on the body becomes completely similar in both species. Finally, there were some interesting differences in males; those from the central parts of Africa had fine punctures of entirely yellow clypeus ( Figure 78a View FIGURE 78 ), while those from Yemen had coarse punctures and traces of basal brownish spot ( Figure 78b View FIGURE 78 ).

Distribution. Nearly the entire Sub-Saharan Africa.In addition to mainland Africa, this species is also distributed in Yemen. One photograph suggests it might also be present in São Tome (iNat:33195567).

Genetics. In addition to the 8 BINs assigned to COI gene sequences, we sequenced several specimens with 28s rDNA. The mPTP clustering results suggested the existence of three clusters with relatively weak support; although these distances might have suggested the possibility of separating these taxa, the overall amount of evidence prohibited us from making further conclusions. Therefore, despite the fair extent of genetic diversity encountered, we retained all the examined specimens as a single species.