Brachymelecta Linsley, 1939

Onuferko, Thomas M., Packer, Laurence & Genaro, Julio A., 2021, Brachymelecta Linsley, 1939, previously the rarest North American bee genus, was described from an aberrant specimen and is the senior synonym for Xeromelecta Linsley, 1939, European Journal of Taxonomy 754, pp. 1-51 : 8-10

Genus Brachymelecta Linsley, 1939

Brachymelecta Linsley, 1939: 458 .

Xeromelecta Linsley, 1939: 450 , syn. nov.

Melectomorpha Linsley, 1939: 451 , syn. nov.

Nesomelecta Michener, 1948: 15 , syn. nov.

Diagnosis for Brachymelecta

Brachymelecta (previously Xeromelecta ) is an exclusively New World genus of small to mid-sized (8–16 mm) non-metallic anthophoriform bees, for which the following morphological features in combination constitute a diagnosis: the inner ramus of each tarsal claw of the mid- and hind legs is broad, lobe-like, and thus does not resemble the outer ramus ( Fig. 2A–B ) (this feature is unique among North American Melectini but also exhibited by many species of Melecta from the Old World (e.g., M. albifrons ) as well as many other groups of cleptoparasitic bees, Michener 2007); the distitarsi of all legs have arolia ( Hurd & Linsley 1951: pl. 11f); the marginal cell of each fore wing extends little (if at all) beyond the third submarginal crossvein (or, if the wing has only two submarginal cells, the second submarginal crossvein, which is equivalent morphologically to the third because it is the second that is lost) (e.g., Fig. 3A ; see also Engel & Michener 2012: fig. 4 to see this feature in the M.? mucida holotype); vein cu-v of each hind wing is distinctly longer than the second abscissa of vein M+Cu ( Engel & Michener 2012: fig. 5) (this feature is unique to Ericrocidini , Melectini , and Rhathymini , Roig- Alsina & Michener 1993; Michener 2007); in both pairs of wings, most closed cells are hairless and the region beyond the veins of each wing is strongly papillate (e.g., Fig. 3A ; see also Engel & Michener 2012: figs 4–5 to see this feature in the M.? mucida holotype); and most pale hairs (if present) on T1 are distinctly shorter than the longest hairs on the mesosoma (e.g., Fig. 3A–C ).

All species of Brachymelecta except B. larreae have well-defined metasomal fasciae comprised of short, appressed, branched pale hairs (e.g., Fig. 3A–C ), and may thus superficially resemble other cleptoparasitic Apidae (subfamily Nomadinae ), most notably various Epeolini , Ericrocis Cresson, 1887 (Ericrocidini) , and Hexepeolus Linsley & Michener, 1937 (Hexepeolini) . Brachymelecta can be readily distinguished from the aforementioned taxa by the length of the marginal cell of the fore wing, which in the non-melectine nomadines extends well beyond the third submarginal crossvein (or second submarginal crossvein if the wing has only two submarginal cells). In contrast to Epeolini and Hexepeolus (but not Ericrocis ), female Brachymelecta in ventral view show six recognizable metasomal sterna, with S6 tapering (in female Nomadinae sensu Michener 2007 , S6 is largely if not entirely retracted and commonly emarginate or bifid). Brachymelecta can be further distinguished from any Epeolini by their axillae, which in the latter are produced to rounded lobes, angles, or spines (in Brachymelecta , the axillae continue the contour of the mesoscutellum, as in Ericrocis and Hexepeolus ). Species of Brachymelecta , especially B. larreae , may also be confused with Melecta , but in New World Melecta spp. the inner ramus of each tarsal claw is narrow, pointed, and thus resembles the outer ramus ( Fig. 2C ), and T1 has long, pale hairs, similar in length to those on the dorsum of the mesosoma. Additionally, whereas in male Brachymelecta from North America each flagellomere except F1 is distinctly wider than long (L/ W ratio ≤ 0.8), in male Melecta each flagellomere is at most as wide as long (L/W ratio = 0.9–1.0). In males of the Antillean species of Brachymelecta , the flagellomeres are longer, as in Melecta , but given that the three species are the only melectines known to occur in the Caribbean, they can easily be separated from all other melectine genera by geography. The absence of arolia in Zacosmia readily distinguishes the genus from both Brachymelecta and Melecta .

Remarks

We present Brachymelecta as the replacement name for Xeromelecta at the generic level. This nomenclatural act was prompted by the recognition of the lectotype of Melecta californica and holotype of M.? mucida as belonging to the same species. The holotype of M.? mucida agrees with the diagnosis for the genus Brachymelecta provided herein, which corresponds to the former genus Xeromelecta . Most notably, the inner ramus of each tarsal claw of the mid- and hind legs is broad, lobe-like, and thus does not resemble the outer ramus, as in all species formerly placed in Xeromelecta (see Fig. 2A–B ). In their redescription of Brachymelecta mucida, Engel & Michener (2012) also noted the similarity between the tarsal claws of the M.? mucida holotype and X. californica .

Evidence that the morphological features exhibited by the holotype of M.? mucida fall within the range of variation observed within B. californica is presented in the ‘Remarks’ section for B. californica (vide infra). Melecta californica was described earlier, so the epithet ‘ californica ’ is the senior synonym to be used in reference to the species. Prior to the present study, the name used for this species was Xeromelecta californica . The name Xeromelecta was elevated to the rank of a genus by Hurd & Linsley (1951), after Brachymelecta had already been established as a generic name, by Linsley (1939). The two names were published simultaneously, but Xeromelecta was originally described as a subgenus of Melecta whereas Brachymelecta was described as a separate genus altogether into which M.? mucida was placed, the first among what are now understood to be its congeners to be placed in a new genus. According to article 24.1. of the code of the International Commission on Zoological Nomenclature (ICZN), when synonyms are published simultaneously but proposed at different ranks, the name proposed at the higher rank takes precedence. Therefore, even though M.? mucida is herein regarded as a junior synonym at the species level, Brachymelecta is regarded as the senior synonym for the genus.

Since B. mucida was established as the type species of its genus by original designation and monotypy, its senior synonym ( B. californica ) is herein regarded as the type species for the genus Brachymelecta . Under its former genus, the type species was placed in the subgenus Melectomorpha . Since article 44 of the code of the ICZN stipulates that (in a genus containing subgenera) the subgenus that contains the type species must be denoted by the same name as the genus, the subgenus Melectomorpha is herein recognized as no longer valid. Besides, according to the results of our phylogenetic analysis (presented below), Melectomorpha is paraphyletic, with its two members, B. californica and B. interrupta , not sister to one another but with B. interrupta sister to B. larreae , the only species in the subgenus Xeromelecta . Although Nesomelecta was found to constitute a natural group, to maintain its status as a valid subgenus would require the other three species of Brachymelecta to each be placed in their own separate subgenus or for B. interrupta to be placed in the same subgenus as B. larreae . As four or even three subgenera for a genus of six species is arguably a case of overclassification, the names Xeromelecta , Melectomorpha , and Nesomelecta are herein synonymized under Brachymelecta .

Figures

Fig. 2. Metadistitarsus of male, lateral view. A. Brachymelecta californica (Cresson, 1878) (photo of Melecta? mucida holotype (ANSP 2294), herein synonymized under B. californica), in which the inner ramus (blue arrow) of each tarsal claw is broad, lobe-like, and thus does not resemble the outer ramus. B. B. californica (photo of M. californica lectotype (ANSP 2292)), in which the inner ramus (blue arrow) of each tarsal claw is broad, lobe-like, and thus does not resemble the outer ramus. C. Melecta thoracica Cresson, 1875 (BOLD sample ID: LRBBC1476; PCYU LRB09-3186), in which the inner ramus (blue arrow) of each tarsal claw is narrow, pointed, and thus resembles the outer ramus.

Fig. 3. Brachymelecta alayoi (Michener, 1988). A–B, D: female (JAG); C: male (JAG). A. Habitus, lateral view. B. Habitus, dorsal view. C. Habitus, lateral view. D. Axillae and mesoscutellum, dorsal view.