Nylanderia parasitica, Messer & Cover & Rabeling, 2020

Messer, Steven J., Cover, Stefan P. & Rabeling, Christian, 2020, Two new species of socially parasitic Nylanderia ants from the southeastern United States, ZooKeys 921, pp. 23-48 : 23

Nylanderia parasitica sp. nov. Figures 4A, C, E (queen), 5A, C, E (male); see Plate 89 in Deyrup (2016): p. 349.

Material examined.

Holotype: USA • alate queen; Florida, Hamilton Co., 2 miles east of Jasper, Route 6, pine-oak hammock near Snake Pond; 30.533N, 82.883W, elevation above sea level: 41 m; 03-July-1994; M. and S. Deyrup leg.; MCZ-ENT00716663. Deposited at MCZC.

Paratypes: USA • 7 males; same data as for holotype; MCZ-ENT00716664-666, MCZ-ENT00716668, MCZ-ENT00716670-672 • 1 alate queen, 1 male (on same pin); same data as for holotype; MCZ-ENT00716673 • 1 alate queen, 1 male (on same pin); same data as for holotype; MCZ-ENT00716674 • 1 alate queen, 1 male (on same pin); same data as for holotype; MCZ-ENT00716675. MCZ-ENT00716664-666, MCZ-ENT00716668, MCZ-ENT00716673 deposited at MCZC; MCZ-ENT00716670-672, MCZ-ENT00716674-675 deposited at SIBR.

USA • 1 alate queen; Florida, Alachua Co., Gainesville, Rock Creek; 9-17-IX-1983; S. Gupta leg.; MCZ-ENT00716676 • 1 alate queen; same data as previous; but V-1984; MCZ-ENT00716677. MCZ-ENT00716676 deposited at MCZC; MCZ-ENT00716677 deposited at SIBR.

USA • 1 alate queen; Georgia, Jones Co., Piedmont National Wildlife Refuge; 33.05N, 83.7167W; 19-26-VII-1994; J. Pickering leg.; MCZ-ENT00716662. Deposited at MCZC.

Diagnosis.

The queen of N. parasitica differs from the queen of its host, N. faisonensis , by its lightened coloration and smaller size (WL: N. parasitica = 0.77-0.83 vs. N. faisonensis = 1.00-1.35; Fig. 6 ). Macrosetae counts across the entire body of N. parasitica vs. N. faisonensis are higher: MMC (16-23 vs. 4-14), MtMC (6-9 vs. 1-3), and PMC (7-11 vs. 4-6); and macrosetae densely cover the whole gaster. Scape macrosetae are absent. The eyes also extend beyond the lateral margins of the head. Reduced CI (86-91 vs. 91-102), reduced REL (24-26 vs. 30-33), SI increased (113-119 vs. 102-112). Mandibular dentition reduced to an apical tooth and maximally two minute denticles as opposed to six mandibular teeth. Males are distinctly bicolored with a darker head and gaster, and the mesonotum is reduced and does not protrude beyond the pronotum. The pronotum possesses one or two macrosetae, which are absent in N. faisonensis . The antennae also have a reduced number of segments, possessing 12 as opposed to 13. CI increased (95-97 vs. 87-94) and reduced REL (26-29 vs. 34-36).

Nylanderia parasitica queens differ from those of N. deceptrix by: (i) possessing dense, pale macrosetae across the entire body, (ii) exhibiting a uniform body coloration, and (iii) an overall smaller size (WL: N. parasitica = 0.77-0.83 vs. N. deceptrix = 0.99-1.07; Fig. 7 ), (iv) the absence of macrosetae from the antennal scape, (v) reduced profemur size (FI 18-20 vs. 21-24), (vi) smaller relative eye size (REL 24-26 vs. 33-37), and (vii) shorter relative antennal scape length (SI 113-119 vs. 121-130). Mandibular dentition is reduced to an apical tooth and maximally two minute denticles vs. four or five mandibular teeth in N. deceptrix . In contrast to N. deceptrix , males of N. parasitica have (i) fully developed wings, (ii) pale macrosetae across the body, (iii) 1-2 pronotal macrosetae, (iv) a higher number of macrosetae on the metanotum (3-5 vs. 1-2), (v) macrosetae present on the gaster, (vi) a reduced FI (18-20 vs. 22-25), (vii) a reduced REL (26-29 vs. 34-36), (viii) a reduced SI (113-119 vs. 125-127), and (ix) 12-segmented antennae.

Description, holotype gyne.

Measurements: TL 2.54, HW 0.53, HL 0.59, EL 0.15, SL 0.60, MW 0.49, PW 0.56, WL 0.79, GL 1.16, PDH 0.31, PFL 0.67, PFW 0.14, SMC 0, PMC 9, MMC 16, MtMC 6. Indices: CI 90, REL 26, SI 114, FI 20. Nylanderia parasitica is unique in the context of the Nearctic Nylanderia fauna because the queens are the smallest known to date (TL 2.54). Head: slightly longer than wide (CI 90), broadening posteriorly, eyes protruding beyond lateral margins of head, three ocelli present. Maxillary and labial palp formula 6:4, mandibular dentition reduced to apical tooth and one small denticle. Antennae 12-segmented, scapes long (SI 114), exceeding posterior margin of head by length of first three funicular segments, covered in pubescence but lacking macrosetae. Mesosoma: fully alate, pronotum bearing nine macrosetae, mesonotum bearing 16 macrosetae, metanotum bearing six macrosetae, mid and hind legs lacking macrosetae. Forewings showing no significant differences in venation from host, slight reduction in venation in hindwings. Metasoma: lateral margins of petiole with pubescence and three macrosetae, gaster uniformly covered in dense pubescence and macrosetae. Body uniform yellow-brown in color with legs, antennae, and mandibles lighter yellow. All body regions densely covered in pale pubescence and macrosetae.

Measurements, paratype gynes

(N = 6): TL 2.27-2.54, HW 0.52-0.56, HL 0.58-0.61, EL 0.15, SL 0.60-0.63, MW 0.44-0.49, PW 0.49-0.57, WL 0.77-0.83, GL 0.89-1.16, PDH 0.30-0.32, PFL 0.60-0.67, PFW 0.11-0.14, SMC 0, PMC 7-11, MMC 16-23, MtMC 6-9. Indices: CI 86-91, REL 24-26, SI 113-119, FI 18-20.

Description, paratype males.

Measurements (N = 10): TL 1.70-2.10, HW 0.44-0.47, HL 0.46-0.49, EL 0.12-0.14, SL 0.51-0.54, MW 0.30-0.31, PW 0.36-0.38, WL 0.59-0.64, GL 0.62-0.99, PDH 0.22-0.25, PFL 0.52-0.56, PFW 0.10-0.11, PL 0.15-0.19, SMC 0, PMC 1-2, MMC 10-13, MtMC 3-5. Indices: CI 95-97, REL 26-29, SI 113-119, FI 18-20. Body bicolored, pale yellow mesosoma with yellow-brown legs, head and gaster, head slightly darker than gaster, antennae and mandibles yellow. Head: covered in pubescence and macrosetae, less dense than in female, slightly longer than wide (CI 95-97), eyes protruding beyond lateral margins of head, three ocelli present; maxillary and labial palp formula 6:4, mandibular dentition reduced to apical tooth only; antennal scapes long (SI 113-119), exceeding the posterior margin of head by length of funicular segments I-III, covered in pubescence, lacking erect macrosetae, antennae 12-segmented, reduced from typical 13-segmented in ants. Mesosoma: dorsum covered in pubescence and macrosetae, largely absent on lateral portions of mesosoma, macrosetae matching body coloration, pronotum bearing one or two macrosetae, mesonotum bearing 10-13 macrosetae, metanotum bearing 3-5 macrosetae curving towards the midline of body; fully alate, wings resemble host with no significant differences. Metasoma: petiole triangular with longer posterior face, 1-3 macrosetae present; gaster covered in pubescence and macrosetae, with macrosetae clustering on first gastral tergite and posterior margins of tergites and sternites. Genitalia: parameres narrowly triangular, straight and densely covered in macrosetae, digiti narrow and tubular, cuspi broad anteriorly and narrow laterally at posterior end.

Etymology.

Nylanderia parasitica inhabits the nests of N. faisonensis , exhibits morphological characteristics of the inquiline syndrome, and potentially lacks a worker caste. Hence, the species epithet is indicative of the socially parasitic life history of N. parasitica .

Distribution and natural history.

Information on the natural history and biogeography of N. parasitica is extremely limited. In previous publications, N. parasitica was referred to as undescribed socially parasitic Nylanderia species ( N. sp. 1) ( Kallal and LaPolla 2012) and Nylanderia Species B ( Deyrup 2016). Most individuals of N. parasitica were collected from Hamilton County, Florida. Two alate queens were collected from Alachua County, Florida, and a single alate queen was collected from Jones County, Georgia (Fig. 10 ; see also Deyrup 2016). The type series was collected inside the nest of N. faisonensis in a rotten log located in an upland oak-pine hammock and a pond swamp area in Hamilton County ( Deyrup 2016). Unfortunately, no additional observations were recorded from this mixed colony. The two queens from Alachua County were collected in malaise traps in May and September, suggesting that N. parasitica females disperse on the wing throughout the warm summer months.

The host of N. parasitica , N. faisonensis , is widely distributed in the southeastern United States ( Kallal and LaPolla 2012) and is primarily a woodland species living in rotting branches, under rotting tree bark, or in the leaf litter ( Trager 1984). Nests are often fragmented, and they do not make a soil nest like most other Nearctic Nylanderia species, with the single queen living deep under the leaf litter, while workers and brood live near the surface ( Trager 1984). Alates are reared from August to December, followed by an overwintering period typical of Nearctic Nylanderia . Alate individuals disperse from the maternal nests between March and May, while more southern populations start dispersing earlier during those months ( Trager 1984). It remains unknown whether N. parasitica is tolerant of the N. faisonensis queen.

Worker caste.

Our limited collections of N. parasitica have not yielded any putative workers for this species. Therefore, like N. deceptrix and N. parasitica , it is likely that this species is a workerless inquiline.

Figures

Figure 4. Gynes of the social parasite Nylanderia parasitica (A, C, E) and its host Nylanderia faisonensis (B, D, F) in full-face (A, B), lateral (C, D), and dorsal (E, F) views. Scale bars: 0.1 mm (A, B), 0.5 mm (C-F).

Figure 6. Boxplots comparing body sizes (Weber's Length) of social parasite queens (red) to the queens (light blue) and workers (dark blue) of their respective host species. Letters above the boxes indicate significantly different groups (Pairwise Mann-Whitney Test with Bonferroni correction, P <0.05).

Figure 7. Boxplot comparing body sizes (Weber's Length) of social parasite queens to each other. Letters above the boxes indicate significantly different groups (Pairwise Mann-Whitney Test with Bonferroni correction, P <0.05).

Figure 10. Geographic distribution of N. parasitica (black stars) and its host N. faisonensis (red circles). Host distribution data was supplemented with additional information from antmaps. org (Janicki et al. 2016).