Centris (Relicthemisia), Vivallo & Zanella, 2021

Vivallo, Felipe & Zanella, Fernando César Vieira, 2021, Relicthemisia, a new subgenus of the oil-collecting bee genus Centris Fabricius, 1804 with notes on distribution and host plants of C. xanthomelaena Moure & Castro, 2001 (Hymenoptera: Apidae), European Journal of Taxonomy 760, pp. 1-15 : 3-4

Relicthemisia subgen. nov.

urn:lsid:zoobank.org:act:361E0AE3-2711-4089-974A-DA742A130E52

Figs 1–4

Type species

Centris xanthomelaena Moure & Castro, 2001

Diagnosis

Integument dark brown to black, clypeus and labrum coriaceous with coarse and dense punctation, but the clypeus with an unpunctated area as a median longitudinal band on upper half ( Fig. 1A ).

Female

Inner orbits of compound eyes converging downward ( Fig. 1A ). Mandible with four apically acute teeth, the fourth tooth slightly larger than the third ( Fig. 1A ). Basitibial plate elliptical, with S-like secondary plate ( Fig. 2A ). Elaiospathes normally developed.

Male

Clypeus, except lateral areas, and labrum yellow ( Fig. 1C ). Yellow spots on paraocular and supraclypeal areas ( Fig. 1C ). Apical margin of T7 with strong emargination ( Fig. 2B ). S7 without emargination on the basal border ( Fig. 2B ). S8, apical projection clearly defined, larger at middle and with rounded apex ( Fig. 2C ). Genital capsule with long dorsoapical projection of gonocoxite, ca 2/3 lengths of gonostylus ( Fig. 2E ).

Etymology

From Latin ‘ relictus ’ (a survivor from a previous age) plus ‘ Hemisia ’ (a junior synonym of Centris ) due to the antiquity and isolation of this lineage.

Remarks

Centris xanthomelaena , the only species of the new subgenus Relicthemisia , was recognized as a distinct lineage with no close relationship to other species, based on morphological ( Zanella 2002) and molecular data ( Martins & Melo 2015). Depending on the study, the phylogenetic position of this lineage was different, either as sister group of Centris s. str. or Paracentris Cameron, 1903 respectively. Nevertheless, it was always recovered as a distinct and relatively old lineage within the ‘ Centris group’. According to Martins & Melo (2015), C. xanthomelaena diverged from a South American clade formed by Paracentris around 18 million years ago, at about the same time when the major lineages within the ‘ Centris group’ diverged from each other.

The hypothetical relationship of this species with Centris s. str. was based on the interpretation of two morphological characters: the strong emargination on the apical margin of T7 ( Fig. 2B ; character 25: 0 in Zanella 2002) and the short and wide translucent laminar projection on the dorsodistal region of the gonocoxite at the base of the long, giant bristles ( Fig. 2E–F ; character 44: 1 in Zanella 2002), but the states present in C. xanthomelaena are clearly unique and cannot be homologous to those present in species of Centris s. str.

Despite the fact that new phylogenetic analyses using a higher number of terminals of Centris s. str. and Paracentris can provide new information regarding the history and relatedness of the lineage of C. xanthomelaena , its distinctness and old history are well supported (see Martins & Melo 2015). Besides the uniqueness of the intense yellow slightly greenish pilosity covering the head, mesosoma (except the ventral surface) and on the anterior half of T1 that allow to easily recognize C. xanthomelaena from other species of the genus ( Fig. 1A–D ), this monotypic subgenus presents a unique combination of characters of the male’s genitalia that distinguishes it from the other members of the ‘ Centris group’: an emargination on the apical margin of T7 ( Fig. 2B ); a long dorsoapical projection of gonocoxite, ca 2/3 lengths of gonostylus ( Fig. 2E ); the dorsomedial projections of the genital capsule ( Fig. 2E ), as well as the S-like lower margin of the female’s secondary basitibial plate ( Fig. 2A ).

Figures

Fig. 1. Centris (Relicthemisia) xanthomelaena Moure & Castro, 2001. A–B. ♀. A. Frontal view. B. Habitus, lateral view. C–D. ♂. C. Frontal view. D. Habitus, lateral view. Scale bars: A, C = 2 mm; B, D = 5 mm.

Fig. 2. Morphological characteristics of Centris (Relicthemisia) xanthomelaena Moure & Castro, 2001. A. Female basitibial plate. B. Male S7. C. Male S8. D. Female pygidial plate. E. Genital capsule (dorsal view). F. Genital capsule (ventral view). Scale bars = 0.5 mm.

Fig. 3. Distribution records of Centris (Relicthemisia) xanthomelaena Moure & Castro, 2001. The limits of biogeographical provinces are depicted in the map. Most records of this species are found in the Caatinga province in northeastern Brazil and marginally in the Cerrado Province, both in the South American diagonal of dry open areas.

Fig. 4. Female of Centris (Relicthemisia) xanthomelaena Moure & Castro, 2001 visiting Krameria sp. (Krameriaceae) in Estação Ecológica do Seridó, Rio Grande do Norte State, Brazil.