Nylanderia pubens

This ant belongs to a species complex that contains a number of morphologically similar species.

Identification
Identifying workers? Good luck! You need males (see the final paragraph in this section). Workers of N. pubens are indistinguishable from Nylanderia fulva. Gotzek et al. (2012) explain: the genus Nylanderia has a long history of taxonomic uncertainty in North America largely due to a lack of distinctive morphological characters in the worker caste.

LaPolla and Kallal (2019) - Large species (TL: >2.5), brown, and entire body covered in dense pubescence that gives body a dull and shaggy appearance shaggy. Compare with: Nylanderia bourbonica, Nylanderia fulva.

Unfortunately, it does not seem possible to separate workers of the species based on morphology. Despite the fact that Trager (1984) noted some differences in the heads of N. pubens workers from those of N. fulva stating N. pubens had more emarginate posterior margins, less overall pubescence and the head lacking punctation, we have not found that those differences reliably separate the species. It is not uncommon for sister species in Nylanderia to display differences in male morphology, while workers are difficult to impossible to distinguish morphologically. Two other widespread North American species, Nylanderia terricola and Nylanderia vividula are similar in requiring males for identification (Kallal & LaPolla, 2012).

This former subspecies of N. fulva was elevated to full species by Trager (1984) based primarily on differences in shape and pilosity of the male gonopods (see images in the caste section). Nylanderia pubens has gonopods that are more rounded at the distal apex, and much more setose. These morphological differences, as well molecular markers, were used by Gotzek et al. (2012) to support Trager’s assertion that N. fulva and N. pubens are in fact separate species. Based on the Gotzek et al. (2012) study, N. fulva and N. pubens can putatively be considered sister species. Dissection of male N. fulva and N. pubens genitalia completed in this study revealed significant differences in the shape of the penial sclerites as well as in the shape of the 9th sternites. It is important to note that while we had abundant male N. fulva specimens to examine (we dissected 10 specimens from different locations), we only had access to one male N. pubens we could dissect. The penial sclerites of N. pubens are more elongated than those of N. fulva and the 9th sternite is longer (along its anterior-posterior axis) and more shield-like in overall shape in N. pubens compared with N. fulva.

Identification Keys including this Taxon

 * Key to Nearctic Nylanderia workers
 * Key to Nearctic Nylanderia males

Distribution
Possibly restricted to the Caribbean region.

In Florida, where this is an introduced ant, it has had a foothold in Coral Gables, Dade County, for many years, but does not seem to be spreading rapidly. It is abundant on the campus of the University of Miami, where it forages on side walks and runs up and down tree trunks. Pest status: so far, this is a minor and localized pest. There are two reports of large infestations in buildings (Klotz et al. 1995). First published Florida record: Trager 1984; earlier specimens: 1953. (Deyrup, Davis & Cover, 2000.)

LaPolla and Kallal (2019) - There has been much interest in the separation of Nylanderia fulva and N. pubens recently due to the rapid spread of N. fulva across the southern United States (Gotzek et al. 2012; Kumar et al. 2015). While N. fulva is the species of recent interest, it is unclear if N. pubens is native to the West Indies either. It seems unlikely to be native based on the fact N. pubens is always found in lowland, highly disturbed places in the West Indies. Additionally, the fact that N. pubens is very likely the sister species to N. fulva, which almost certainly is native to southcentral South America, further supports the notion N. pubens is South American in origin. At one time populations of N. pubens were established in Florida (Trager, 1984), but those populations appear to have since been extirpated from the state. Specimens of N. pubens were also found in the National Museum of Natural History collection (Smithsonian Institution) that came from greenhouses in Washington D.C. around the turn of the 20th Century. Why N. fulva is now the species primarily being moved around the Western Hemisphere by human activities and not N. pubens is an interesting question.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Anguilla, Barbados, Cuba, Dominican Republic, Ecuador, Guadeloupe, Haiti, Lesser Antilles, Puerto Rico.

Biology
The following text and map are from Gotzek et al. (2012). References that were indicated but removed from the text are stated in the original publication:

There has been widespread misidentification of Nylanderia fulva and N. pubens specimens. Within museum collections, misidentifications are common given the morphological similarities of the workers within the genus overall, as well as because of uncertainties regarding species boundaries.

Given the uncertainty of worker based identifications of N. fulva and N. pubens most publications that involve either of these species are suspect; they may not involve the species listed in the publication, including the possibility that they are neither N. fulva nor N. pubens and are an entirely different Nylanderia species. It appears at this time that N. pubens is restricted to the Caribbean region. This species has been reported to be relatively to be relatively common in southern Florida in the 1950’s –1970’s, where it was also most recently found in 1994 (M. Deyrup, pers. comm. to JSL). It is not known whether these populations still persist today. Since we show that samples from northern Florida initially considered to be N. cf. pubens are actually N. fulva and given the invasive nature of N. fulva, we hypothesize that most or even all alleged occurrences of N. pubens in Florida are misidentified N. fulva. This would not be surprising, since the distribution is solely based on worker identifications (D. Oi, pers. comm. to DG). We also suspect that N. pubens may not have good invasive capabilities compared to N. fulva, given the currently rapidly expanding distribution of N. fulva in the United States and lack of N. pubens in our samples from northern Florida. It will require much better sampling of molecular data or male samples from throughout Florida to test our hypothesis. Currently, the Caribbean is likely the only place where N. fulva and N. pubens are sympatric and therefore the only region where identifications of workers will be difficult. If we are correct concerning the distribution and inability of N. pubens to become a pest, then the population explosions attributed to N. pubens that plagued the Caribbean from 19th century Bermuda to the recent outbreak on St. Croix and in southern Florida may very well have been N. fulva instead of N. pubens. Nylanderia fulva is known to be an invasive ant, most recently from Colombia where an outbreak occurred after this species was apparently introduced to control leafcutter ants and venomous snakes.

Nomenclature

 *  pubens. Prenolepis fulva r. pubens Forel, 1893g: 338 (w.q.m.) ANTILLES. Combination in Paratrechina (Nylanderia): Emery, 1925b: 222; in Nylanderia: Kempf, 1972a: 167; in Paratrechina: Trager, 1984b: 143; in Nylanderia: LaPolla, Brady & Shattuck, 2010a: 127. Junior synonym of fulva: Creighton, 1950a: 406. Revived from synonymy and raised to species: Trager, 1984b: 143.

Worker
LaPolla and Kallal (2019) - (n= 2): TL: 2.60–2.90; HW: 0.64–0.67; HL: 0.67–0.76; EL: 0.18–0.19; SL: 0.88– 0.9; WL: 0.90–0.94; GL: 1.05–1.20. SMC: 18–26; PMC: 4–6; MMC: 2–3. indices: CI: 88–95; REL: 25–28; SI: 133–137; SI2: 20–21.

Head: sides of head in full-face view nearly parallel; posterolateral corners rounded; posterior margin rounded distinctly emarginate medially; anterior clypeal margin emarginate; three ocelli present; eye well-developed. Mesosoma: in lateral view, pronotum convex; anterior margin of mesonotum more or less even with posterior pronotal margin; metanotal area with a short flat area before spiracle; dorsal face of propodeum slightly convex to almost flat in some specimens; dorsal face of propodeum lower than mesonotum in lateral view. Color and pilosity: brown; entire body covered with dense pubescence, giving it dull appearance; in many places across the body pubescence becomes decumbent and long, especially on pronotum, mesonotum and gaster giving shaggy appearance.

Queen
LaPolla and Kallal (2019) - (n=1): TL: N/A; HW: 1.04; HL: 0.99; EL: 0.31; SL: 1.1; WL: 1.7; GL: N/A. SMC: 21 PMC: 5; MMC: 23. indices: CI: 105; REL: 32; SI: 106.

Generally, as in worker with modifications expected for caste.

Male
LaPolla and Kallal (2019) - (n=1): TL: 2.40; HW: 0.57; HL: 0.63; EL: 0.28; SL: 0.99; WL: 1.10; GL: 1.30; SMC: 10; PMC: 0; MMC: 15. indices: CI: 86; REL: 42; SI: 150.

Head: sides of head in full face view nearly parallel becoming slightly broader posterior to eyes; posterior margin straight to slightly rounded; clypeus emarginate anteriorly; mandible with distinct apical tooth and usually a much smaller subapical tooth adjacent to apical tooth; basal angle sharp and distinct. Mesosoma: in lateral view, dorsal margin of mesoscutum same as height as dorsal margin of mesoscutellum; propodeum steeply sloping without distinct dorsal and declivitous faces. Genitalia: gonopod apex triangular but broadly rounded in lateral view; in dorsal view, gonopod margin curves away from penial sclerite; digitus with broadly rounded apex nearly parallel with penial sclerite; cuspis tubular, rounded at apex bending sharply toward digitus; anteroventral process of penial sclerite broadly rounded; valvura of penial sclerite placed ventral to midline. Color and pilosity: nearly uniform light brown to brown; head, pronotum and gaster often slightly darker with a slightly lighter posterior portion of mesosoma; entire body cover with a layer of dense pubescence.

Type Material
LaPolla and Kallal (2019) - 5 workers, 1 queen and 2 male syntypes, ST. VINCENT (examined; lectotype male here designated; specimen on pin with two separate points; point with lectotype marked with small red dot. In the interest of nomenclatural stability, a lectotype worker of Nylanderia fulva is here designated from the 12 worker syntype series from NHMW that were examined. Label data is: [Brazil] Novara; 1857-59; Reise (USNMENT007553598).

References based on Global Ant Biodiversity Informatics

 * Calcaterra L. A., F. Cuezzo, S. M. Cabrera, and J. A. Briano. 2010. Ground ant diversity (Hymenoptera: Formicidae) in the Ibera nature reserve, the largest wetland of Argentina. Ann. Entomol. Soc. Am. 103(1): 71-83.
 * Chacon de Ulloa P., A. M. Osorio-Garica, R. Achury, and C. Bermudez-Rivas. 2012. Hormigas (Hymenoptera: Formicidae) del Bosque seco tropical (Bs-T) de la cuenca alta del rio Cauca, Colombia. Biota Colombiana 13(2): 165-181.
 * Fisher B. L. 1992. Facultive ant association benefits a Neotropical Orchid. Journal of Tropical Ecology 8: 109-114.
 * Fisher B. L., L. da Silveira Lobo Sternber, and D. Price. 1990. Variation in the use of orchid extrafloral nectar by ants. Oecologia 83: 263-266.
 * Leponce, M., L. Theunis, J.H.C. Delabie and Y. Roisin. 2004. Scale dependence of diversity measures in a leaf-litter ant assemblage. Ecography. 27:253-267.