Lasioglossum (Dialictus) carlinvillense Gibbs, 2009

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 : 18-22

Lasioglossum (Dialictus) carlinvillense Gibbs, 2009

Figs 6–8

Lasioglossum (Dialictus) carlinvillense Gibbs, 2009a: 28 (holotype, ♀, deposited in PCYU, examined).

Lasioglossum (Dialictus) carlinvillense – Gibbs 2011: 25 , 32 (key to species), 65 (review).

Diagnosis

Females of L. carlinvillense have the tegula relatively small (reaching but not exceeding posterior margin of mesoscutum), moderately densely punctate (IS ≤ 1 PD), and with inner posterior margin straight or weakly concave; mesoscutum entirely dull and tessellate; metapostnotum with strong subparallel rugae reaching posterior margin; mesepisternum strongly imbricate with crowded punctures (IS = 0 PD), inner metatibial spur with only two branches, and T1–T3 flat in lateral view. They are most similar to those of L. coactus and L. tegulare , both of which have the inner metatibial spur with 3–4 branches. Females of L. coactus also have T1–T3 distinctly convex in lateral view.

The male of L. carlinvillense , if correctly associated, may be morphologically indistinguishable from L. tegulare (see Comments).

Etymology

Gibbs (2009a) named this species after the type locality of Carlinville, Illinois, combined with the Latin adjectival suffix ʻ -ense ʼ (indicating association with a place).

Material examined

Holotype UNITED STATES – Illinois • ♀; Macoupin Co., east of Carlinville ; 39.2787° N, 89.7961° W; 25 Jun. 2006; J. Gibbs and C. Sheffield leg.; PCYU.

Other material

UNITED STATES – Alabama • 1 ♀; Sheffield ; [34.77° N, 87.7° W]; 4 Aug. 1944; G.E. Bohart leg.; BBSL700639 • 1 ♂; ibid.; 4 Aug. 1944; G.E. Bohart leg.; BBSL700633 . – Illinois • 1 ♀; Carlinville ; 39.2787° N, 89.8898° W; 24 Jun. 2006; J. Gibbs leg.; PCYU • 1 ♀; Dubois ; [38.22° N, 89.21° W]; 8 Aug. 1917; INHS • 1 ♀; Litchfield ; 39.1484° N, 89.66696° W; 25 Jun. 2006; C. Sheffield leg.; PCYU .

Range

Illinois to Alabama ( Fig. 8 ).

Floral hosts

None recorded.

DNA barcodes

Three confirmed sequences available (BOLD process IDs: DIAL728-06, DIAL832-06, DIAL837-06). These sequences are identical (0% maximum intraspecific p-distance). They are closest in terms of p-distance to L. coactus (0.15% minimum interspecific p-distance). No fixed nucleotide substitutions distinguish L. carlinvillense from all other species of the L. gemmatum complex or closely related species.

Comments

Rare. Lasioglossum carlinvillense was described from only four female specimens, all from Illinois. These specimens have similar DNA barcodes to several sequences from Colorado and Texas for which the associated specimens could not be located and examined. These sequences probably belong to L. coactus , which shares the same BIN as L. carlinvillense , but the possibility that L. carlinvillense ranges further west into Colorado cannot be ruled out.

Two additional female specimens with only two metatibial spur branches were discovered in the current work, both from Alabama. One of these is much larger than the other known specimens of L. carlinvillense and is believed to be an atypical L. puteulanum . The other is morphologically indistinguishable from other L. carlinvillense and may truly be a new record. There is one male from the same collection event as this specimen, but it is morphologically indistinguishable from L. tegulare , and whether it is the hitherto unknown male of L. carlinvillense is uncertain. These specimens are far too old to attempt DNA barcoding, but fresh material from Alabama could help resolve their status.

It is possible that L. carlinvillense is merely an aberrant form of L. tegulare or a hybrid of L. tegulare and L. coactus . Lasioglossum carlinvillense and L. tegulare are apparently morphologically indistinguishable except by the metatibial spur and the slightly smaller size of the former. The fact that L. coactus also shares a BIN with L. tegulare suggests that introgression could have occurred between these two species. A possible explanation, then, is that the BIN corresponding to L. carlinvillense is the “natural” COI sequence for L. coactus , and the L. coactus sequences in the L. tegulare BIN are a result of introgression. Similarly, the L. carlinvillense sequences could then be L. tegulare which acquired L. coactus COI sequences through introgression. More evidence is needed to test this hypothesis.

Figures

Fig. 6. Lasioglossum (D.) carlinvillense Gibbs, 2009, ♀, holotype (PCYU). A. Dorsal habitus. B. Lateral habitus. C. Face. D. Metasoma and propodeum. Scale bars = 1 mm.

Fig. 7. Lasioglossum (D.) carlinvillense Gibbs, 2009, possible ♂ (based on a single male associated with a single female) (BBSL700633). A. Lateral habitus. B. Dorsal habitus. C. Face. D. Metasoma. Scale bars = 1 mm.

Fig. 8. Georeferenced collection records of Lasioglossum (D.) carlinvillense (black squares) and predicted distribution by maximum entropy ecological niche modelling in Maxent (colour shading). Warmer colours indicate higher cloglog probability of occurrence.