Nesomyrmex asper ( Mayr, 1887 )

Arredondo, Brandon S. & Guerrero, Roberto J., 2025, The ant genus Nesomyrmex Wheeler (Formicidae, Myrmicinae) from the threatened Colombian tropical dry forest: three new species, a new synonymy, and new distributional data, ZooKeys 1232, pp. 131-172 : 131-172

Nesomyrmex asper ( Mayr, 1887)

Figs 18 , 19 , 20 , 29

Leptothorax asper Mayr, 1887: 618. Syntype series (worker, queen, male): Brazil, Santa Catarina. [ NHMW] (AntWeb image examined, CASENT 0901801).

Combination in Leptothorax (Goniothorax) : Emery 1896: 59.

Leptothorax (Goniothorax) asper var. rufa Emery, 1896: 61. Syntype series (queen, worker): Brazil, Pará. [ MSNG]. (AntWeb image examined, CASENT 0904722). Synonymy by Kempf 1959: 414.

Leptothorax (Goniothorax) tristani Emery, 1896: 61. Syntype series (queen, worker): Costa Rica. [ MSNG]. (AntWeb image examined, CASENT 0904724). Synonymy by Longino 2006: 136.

Leptothorax asper var. antoniensis Forel, 1912: 18. Syntype series. (worker): Colombia, Sierra Nevada de Santa Marta, San Antonio. [ MHNG]. (AntWeb image examined, CASENT 0909002). syn. nov.

Leptothorax asper var. sulfurea Forel, 1912: 18. Syntype series (worker): Brazil. [ MHNG]. (AntWeb image examined, CASENT 0909003). Synonymy by Kempf (1959: 414).

Combination in Leptothorax (Nesomyrmex) : Kempf 1959: 414.

Combination in Nesomyrmex : Bolton 2003: 272.

Worker measurements.

(n = 8) HL 0.86–1.08, HW 0.78–0.99, SL 0.68–0.84, ML 0.41–0.53, EL 0.19–0.24, PW 0.51–0.66, PTW 0.21–0.31, PPW 0.31–0.44, WL 1.05–1.38, PH 0.29–0.34, PTL 0.37–0.46, PTH 0.23–0.29, PPL 0.24–0.34, PPH 0.26–0.32, GL 0.88–1.01. CI 90–92, SI 84–87.

Geographic range.

Argentina, Bolivia, Colombia, Ecuador, French Guaina, Nicaragua, Panama, Paraguay, Trinidad and Tobago, Venezuela

Examined material.

Colombia • 1 worker; Atlántico, Usicurí, Vda. Luriza , CIALU; 10.75198°N, 75,030 75°W; 155 m a. s. l.; 28–30 Mar. 2023; J. Camargo, H. Sierra, S. De la Hoz legs.; Winkler; CBUMAG:ENT:54657 • 1 worker; Bolívar, Turbaco, Finca el Huerto ; 10.371944°N, 75.349667°W; 102 m a. s. l.; 05 Jul. 2015; A. Sagoval, C. Cantor legs.; secondary forest; ICN 106553 . • 1 worker; Cesar, La Jagua de Ibirico ; 9.561111°N, 73.336389°W; 150 m a. s. l.; 2007; F. Fernández leg.; pitfall; ICN 019802 . • 1 worker; Huila, Aipe, Cuenca Río Aipe, Vda. San Isidro ; 3.3453561°N, 75.3057781°W; 841 m a. s. l.; 25 Nov. 2017; L. Arcila leg.; Winkler; IAvH . • 1 worker; Valle del Cauca, Dagua, Cuenca Río Dagua , Vda. Limonar ; 3.6238689°N, 75.6945069°W; 1071 m a. s. l.; 17 Aug. 2021; L. Arcila leg.; Pitfall; IAvH . • 2 workers; Cauca, Santander de Quilichao, Las Chatas ; 3.1096°N, 76.5265°W; 909 m a. s. l.; 17 Aug. 2021; M. A. Bautista-Giraldo; I. Armbrecht legs.; meadow; CBUMAG:ENT:40121 , CBUMAG:ENT:40122 .

Natural history.

Some workers were collected foraging during the day on vegetation in TDF fragments in the Valle del Cauca. Additionally, one worker was collected foraging on the grassland soil using pitfall traps.

Comments.

This species is recognized by the set of the following characters: 11 antennomeres, clypeus sculpture ranges from smooth and shiny to longitudinally costate or reticulate, inner area of dorsal surface of mandibles finely reticulate and opaque, propodeal lobe angulate, apex blunt. Nesomyrmex asper presents intraspecific morphological variation in some traits throughout its distribution in the Colombian TDF. The lateral tubercles of the petiole and postpetiole are variable characteristics, both in quantity and size, between populations of the species (Fig. 18 ). For example, workers from populations in the Valle del Cauca (western Colombia) have no lateral tubercles on the petiole and postpetiole (Fig. 18 A ) while in more northern populations such as those from La Guajira and Magdalena there are between one and three tubercles distributed asymmetrically on the sides of the petiole (Fig. 18 D, E ). Analysis of N. asper specimens across the Colombian TDF suggests that populations of this species are morphologically cohesive in terms of the diagnostic characteristics that define it, but traits such as lateral tubercles on the petiole / postpetiole show extensive phenotypic plasticity.

Our novel observations of variability in number and shape of lateral petiole and postpetiole tubercles in N. asper contrasts with the use of presence and absence of tubercles as a diagnostic trait for some nomenclatural changes in N. asper ( Kempf 1958, 1959, 1975; Longino 2006). Longino (2006) proposed Nesomyrmex tristani ( Emery, 1896) as a junior synonym of Nesomyrmex asper considering the similarity of the lateral processes (i. e., lateral tubercles) of the petiole between the workers of both taxa. The same author used the differentiation of the lateral processes of the postpetiole (described there as “ acuminate teeth ”: p. 136) observed between the workers of Nesomyrmex asper var. antoniensis ( Forel, 1912) and N. asper s. str, to recognize N. antoniensis ( Forel, 1912) as a valid species. Considering the intraspecific morphological variation in the lateral tubercles of N. asper workers, we compared this trait with the type worker of N. antoniensis ( CASENT 0909002 ), finding that the latter falls within the high intraspecific variability of N. asper . Likewise, the type specimens of both N. antoniensis ( CASENT 0909002 ) and N. asper ( CASENT 0901801 ), and the workers of N. asper present in Colombia and the Sierra Nevada de Santa Marta (type locality of N. antoniensis ) were measured, finding that the type of N. antoniensis (HL 0.89, HW 0.83, SL 0.72, ML 0.43) matches the morphometric range of N. asper (HL 0.86–1.08, HW 0.78–0.99, SL 0.68–0.84, ML 0.41–0.53). Based on the evidence, we found that the morphological variation between N. antoniensis and N. asper is not distinct, with the form referred to as N. antoniensis falling within the variability observed in N. asper . Therefore, we propose N. antoniensis as a junior synonym of Nesomyrmex asper . The highly variable number and shape of tubercles on lateral petiole and postpetiole in N. asper should not be used to separate taxonomic units in these species groups. Interestingly, the lateral processes of the petiole and postpetiolar node described as “ acuminate teeth ” by Longino (2006: 136) are setigerous tubercles (Fig. 19 ; also see Kempf 1959) and their variation in shape is due to projection and orientation relative to the body.

Figures

Figure 18. Variation of lateral petiole tubercles in Nesomyrmex asper. White arrows indicate the tubercles.

Figure 19. Lateral petiole and postpetiole tubercles (Setigerous tubercles). Abbreviations: lpptt (lateral postpetiolar tubercles), lptt (lateral petiolar tubercles), pt (petiole), ppt (postpetiole), set (seta).

Figure 20. Nesomyrmex asper worker (ICN 106553) A full-face view B lateral view C dorsal view. Scale bars: 0.5 mm (A); 1.0 mm (B).

Figure 29. Distributional map of Nesomyrmex species from the tropical dry forest in Colombia.