Lasioglossum gemmatum (Smith, 1853)

Gardner, Joel & Gibbs, Jason, 2023, Revision of the Nearctic species of the Lasioglossum (Dialictus) gemmatum species complex (Hymenoptera: Halictidae), European Journal of Taxonomy 858 (1), pp. 1-222 : 10

Lasioglossum gemmatum species complex

Species included

Lasioglossum angelicum sp. nov., L. busckiellum (Cockerell, 1915) , L. carlinvillense Gibbs, 2009 , L. coactus ( Cresson, 1872) , L. cupreicollis (Friese, 1917) , L. deludens sp. nov., L. diabolicum sp. nov., L. ellisiae ( Sandhouse, 1924) , L. enatum Gibbs, 2018 , L. eremum sp. nov., L. fernandezis Engel, 2000 , L. gaudiale ( Sandhouse, 1924) , L. gemmatum (Smith, 1853) , L. gloriosum sp. nov., L. helianthi ( Cockerell, 1916) , L. holzenthali sp. nov., L. indagator sp. nov., L. lepidii ( Graenicher, 1927) , L. magnitegula sp. nov., L. monense Gibbs, 2018 , L. parvum (Cresson, 1865) , L. paululum ( Sandhouse, 1924) , L. perparvum ( Ellis, 1914) , L. profundum sp. nov., L. pseudotegulare ( Cockerell, 1896) , L. puteulanum Gibbs, 2009 , L. rufodeludens sp. nov., L. stictaspis ( Sandhouse, 1923) , L. surianae ( Mitchell, 1960) , L. tegulare ( Robertson, 1890) , and L. tegulariforme ( Crawford, 1907) .

Diagnosis

Both sexes in the L. gemmatum complex have the tegula enlarged (reaching the posterior margin of the mesoscutum in dorsal view or nearly so), usually strongly punctate, and with the inner posterior margin straight or concave; about 50% of clypeus projecting below suborbital tangent; and T1 without tomentum. Additionally, females have the propodeum with a distinct oblique carina, and males have the mesepisternum and often propodeum lateral face shiny with large, distinct punctures, and metasomal sterna with moderately sparse plumose pubescence 1–2 OD long.

Some members of the L. perdifficile complex (defined in Gardner & Gibbs 2022) have a similar tegula, but these have more than 50% of the clypeus projecting below the suborbital tangent, females with propodeum oblique carina absent, and T1 with lateral tomentum. Some atypical specimens of L. knereri Gibbs, 2010 from California (possibly representing a cryptic species) also have a similar tegula, but have the propodeum without a distinct oblique carina, the metasomal terga all without appressed tomentum, and males have the metasomal sterna with very long and dense scopa-like pubescence (> 2 OD).

Lasioglossum comulum Michener, 1951 , L. dispersum Gibbs, 2018 , L. immigrans Gardner & Gibbs, 2022 , L. strigosigena Michener, 1954 , and several undescribed species have the tegula small, ovoid, and impunctate, which is standard for most L. ( Dialictus ), but resemble the L. gemmatum complex in most other characters. Additionally, DNA barcodes of these two species groups are very similar and suggest a close relationship. These species are informally defined as the L. comulum group. The L. comulum group appears to be an evolutionary grade from which the L. gemmatum complex is derived ( Fig. 2 ), but additional taxon sampling and more molecular data are needed to resolve their relationship with more certainty.

Figures

Fig. 2. 50% majority-rule consensus tree of species of Lasioglossum Curtis, 1833 with enlarged tegulae and representatives of other major lineages, based on 654-bp COI sequences and 15 morphological characters. MCMC tree search was performed in MrBayes ver. 3.2.7 using a GTR+I+Γ4 model for the molecular data, gamma-distributed rate variation for the morphological data, partitioning by data type, two simultaneous runs with 8 chains each, temperature of 0.0375, 20000 000 generations, and L. sordidum (Smith, 1853) set as the outgroup (other settings program defaults). Node labels are posterior probabilities. Taxa names are followed by their BOLD accession numbers. Bold branches on the tree are species with enlarged tegulae.