Tapinoma breviscapum Forel, 1908 status novo

Escarraga, Mayron E., Lattke, John E., Pie, Marcio R. & Guerrero, Roberto J., 2021, Morphological and genetic evidence supports the separation of two Tapinoma ants (Formicidae, Dolichoderinae) from the Atlantic Forest biome, ZooKeys 1033, pp. 35-62 : 35

Tapinoma breviscapum Forel, 1908 status novo Figs 1C, D , 2E, F , 3E, F , 5 , 6

Tapinoma atriceps breviscapa Forel, 1908: 384-385. Syntype series (worker, queen): Brazil, São Paulo, Raiz da Serra. [MHNG, examined]. One syntype worker (CASENT0909768) here designated lectotype; two workers designated as paralectotypes, uppermost specimen and lowermost on the same pin as lectotype worker (MHNG, examined).

Tapinoma atriceps breviscapum Forel. Kempf 1972: 247.

Tapinoma atriceps breviscapum Forel. Shattuck 1994: 142.

Tapinoma atriceps breviscapum Forel. Bolton 2021: e-catalogue (http://antcat.org).

Worker diagnosis.

Lateral margin of head in frontal view slightly convex. Eye with 7 or 8 ommatidia along maximum diameter. Scape short (SI <85). Dorsal face of propodeum in lateral view meeting propodeal declivity through rounded angle; length of dorsal margin about ½ that of declivity.

Worker. Measurements (n = 16): HL 0.58 ± 0.04 (0.53-0.66), HW 0.48 ± 0.04 (0.43-0.56), SL 0.48 ± 0.03 (0.44-0.56), WL 0.63 ± 0.06 (0.49-0.78). Indices: CI 83 ± 1 (82-85), SI 80 ± 2 (78-85).

Head in full-face view oval to rectangular, longer than wide; lateral and posterior margins slightly convex. Maxillary palps filiform, relatively short, not posteriorly surpassing beyond mid-length of head. Mandibles with masticatory margin with 1 large apical tooth, followed by 2 smaller teeth, fourth tooth larger than third, and then followed by denticles. Anterior margin of clypeus slightly emarginate medially. Scape relatively short when compared to T. atriceps (SI <85), reaching or surpassing posterior margin of head by distance shorter than pedicel length. Pronotum and mesonotum form continuous feeble convexity in lateral view; metanotal groove weakly impressed; propodeum dome-shaped, slightly higher than mesonotum. Integument weakly imbricate, excepting petiole which is smooth. Body covered with short decumbent pubescence. Head (excluding clypeus), antenna, and mesosoma lacking erect setae, clypeus with 6 anterior setae. Pilosity pattern on gastric tergites similar as to T. atriceps . Head and gaster medium brown; antenna, mesosoma, legs, and petiole pale whitish yellow to bright orange (Fig. 1C, D ). Mesosoma with brown spot on mesopleuron and lateral pronotum, sometimes present on metapleuron and lateral propodeum, almost completely covering mesosomal side.

Queen. Measurements (n = 6): HL 0.74 ± 0.04 (0.70-0.80), HW 0.64 ± 0.03 (0.59-0.68), SL 0.54 ± 0.04 (0.49-0.59), WL 1.24 ± 0.18 (1.07-1.46). Indices: CI 86 ± 1 (84-87), SI 73 ± 2 (70-76).

Head rectangular in full-face view, clearly longer than wide (CI 84-87); lateral and posterior margins straight. Masticatory margin of mandible with 1 large apical tooth, followed by 2 smaller teeth, fourth tooth larger than third, followed by 5 smaller teeth, and then small denticles decreasing in size. Clypeus slightly emarginate anteromedially. Scape short, never surpassing posterior margin of head (SI 72-76). Integument weakly imbricate, mesopleuron smooth. Dorsum of head with abundant, short, decumbent hairs; clypeus bearing 6 long hairs; gastric tergites with several erect setae near their posterior margins. Body medium brown; palps, flagellum, coxae, trochanters, tibiae, tarsi, and petiole whitish yellow to bright orange (Fig. 2E, F ); propodeum sometimes with whitish-yellow spot on posterodorsal region. Gastric tergites I-III with pale-yellow, transverse posterior strip.

Male. Measurements (n = 3): HL 0.46 ± 0.02 (0.43-0.48) HW 0.46 ± 0.03 (0.43-0.48) SL 0.36 ± 0.02 (0.33-0.38) WL 0.62 ± 0.02 (0.61-0.64). Indices: CI 99 ± 2 (97-100) SI 78 ± 3 (75-82)

Head in dorsal view rounded, posterior margin slightly interrupted by lateral ocelli; anteromedian margin of clypeus straight to weakly emarginate. Compound eye large, rounded; scape long, reaching posterior margin of head; maxillary palp filiform. Mandible semi-falcate; masticatory margin with large apical tooth followed by many teeth of similar size. Integument feebly imbricate, katepisternum smooth. Forewing with median short; hindwing with free section of radial and cu-a present, free section of cubitus absent. Row of long setae present on posterior margins of fore and hindwing. Head, scutum, scutellum, and gaster covered by moderately abundant, yellow, short, decumbent hairs; antenna covered by short, decumbent hairs. Anepisternum covered by hairs, katepisternum lacking hairs ventrally. Gastric tergites I-V lacking erect setae. Head, mesosoma, petiole, and gaster dark brown; antenna and legs light brown.

Distribution.

Tapinoma breviscapum has been recorded from Misiones, Argentina, and from the Brazilian states of Minas Gerais, Rio de Janeiro, and São Paulo (Fig. 5 ).

Biology.

Tapinoma breviscapum is an arboreal ant, but beyond that, there is not much available information. This species, reported as T. atriceps , was found inhabiting a gall of Microgramma squamulosa (Kaulf.) de la Sota ( Santos et al. 2019).

Material examined.

Argentina • 3 workers; Misiones, 40.66 K N Campinas de América; 25°55.153'S, 53°56.151'W; alt. 508 m; 3 Jan. 2008; W. Mackay and E. Mackay legs; WEMC#22811 BRAZIL • 2 queens, 1 worker; Minas Gerais, Alto Caparaó, Parque Nacional Caparaó; 20°25.155'S, 41°51.083'W; 5-20 Dec. 2011; J. Chaul leg.; DZUP • 2 males, 3 workers; Minas Gerais, Serra Caraça; 1380 m; Nov. 1961; K. Lenko, Martins and Silva legs; MZSP 3104 • 3 workers; Minas Gerais, Serra Caraça; 1380m; Nov. 1961; K. Lenko, Martins and Silva legs; MZSP 4216 • 1 male, 2 queens, 17 workers; Minas Gerais, Serra do Cipó, CAPIII; Jan. 2013; M. Anjos M. leg.; DZUP • 1 queen, 2 workers; Minas Gerais, Serra do Cipo , Capão 11; 19°14.873'S, 43°33.055'W; 25 Jun. 2017; H. Brant leg. DZUP • 5 workers; Minas Gerais, Serra do Cipo ; 19°14.874'S, 43°33.054'W; 25 Jun. 2017; M. Escárraga leg., MYR380; Genbak codes: MG920285, MN294973, MN294963, MT375619 ; DZUP 548800 • 1 worker; Rio de Janeiro, Nova Friburgo , Praca do Suspiro , 22°16.763'S, 42°32.148'W; Apr. 2016 - Feb. 2018; I. Lancelloti leg.; DZUP • 5 workers; São Paulo, Barueri ; K. Lenko leg.; MZSP 447 • 5 workers; São Paulo, Barueri ; K. Lenko leg.; MZSP 2477 • 5 workers; São Paulo, Barueri ; 19 Jul. 1958; K. Lenko leg.; MZSP 534 • 3 workers; São Paulo, Cubatão, Estacao Raiz da Serra ; v Ihering leg.; MHNG • 2 queens, 2 workers; São Paulo, Ilha dos Buzios , 2 Apr. 1964; Exp. Dep. Zool. legs; MZSP 3910 • 1 male, 1 queen, 2 workers; São Paulo, Ilha dos Buzios , 2 Apr. 1964, Exp. Dep. Zool. legs; MZSP 4105 • 2 workers; São Paulo, Ilha dos Buzios ; 3 Sep. 1964; Exp. Dep. Zool. legs; MZSP 3885 • 4 workers; São Paulo, Ilha dos Buzios ; 3 Apr. 1964; Exp. Dep. Zool. legs; MZSP 3885 • 1 male, 1 queen, 3 workers; São Paulo, Ilha dos Buzios , 19 Oct. 1963; Exp. Dep. Zool. legs; MZSP 2978 • 1 queen, 4 workers; São Paulo, Ilha dos Buzios ; 17 Oct. 1963; Exp. Dep. Zool. leg; MZSP 2994 • 1 queen, 4 workers; São Paulo, Ilha dos Buzios ; 26 Oct. 1963; Exp. Dep. Zool. legs; MZSP 2992 • 1 queen, 3 workers; São Paulo, Ilha dos Buzios ; 31 Jul. 1964; Exp. Dep. Zool. legs; MZSP 3616 • 1 male, 1 queen, 2 workers; São Paulo, Ilha dos Buzios ; 2 Apr. 1964; Exp. Dep. Zool. [MZSP 4105] • 1 worker; São Paulo; MZSP11974 • 6 workers; São Paulo; USNM .

Morphological separation between Tapinoma atriceps and T. breviscapum

The most readily recognizable morphological diagnostic traits that permit separation of T. atriceps and T. breviscapum workers and queens are the relative length of the scape (i.e., SI), the shape of the propodeum, and differences in the degree of cephalic pubescence. In T. atriceps the worker scape is almost as long as the HL or greater (SI>93; Fig. 1A ), in contrast with T. breviscapum , where it is relatively short (SI <85; Fig. 1B ), sometimes reaching or barely surpassing the posterior head margin by a distance shorter than the pedicel length. SL shows significant differences between the workers of each species (T = 7.51, p <0.0001). Although there is a certain degree of overlap in the absolute measure (0.50-0.63 in T. atriceps and 0.44-0.56 in T. breviscapum ) the relationship from SL to HL for each species showed non-overlapping ranges (Fig. 7 ). Other morphometric traits, such as HL, HW, and WL were also evaluated; however, each of their paired distributions overlapped, showing no statistical differences. The SL partially overlaps in queens of both species (0.58-0.62 in T. atriceps and 0.49-0.59 in T. breviscapum ); however, differences between species were found (T = 2.29, p = 0.0257). These differences are notable in the non-overlapping ranges of the relative length of the scape (82-83 and 70-76, respectively). Statistical differences were also found in the HW of both species (T = 2.26, p = 0.0268); even without measuring, these differences are evident when they are compared under a stereoscope (Fig. 2B vs 2E), as T. breviscapum queens have a more elongate head as reflected in CI values that do not overlap those of T. atriceps queens.

The worker propodeum in both species differs markedly in shape and in the proportions between the dorsal and the posterior faces (Fig. 4B vs 6B). The dorsal propodeal margin when seen laterally in T. atriceps forms a distinct blunt angle with the declivity, contrasting with the rounded convexity formed in T. breviscapum . Additionally, the dorsal margin in T. atriceps is about 1/4 the length of the declivitous margin, while in T. breviscapum it is longer, about 1/2 that of the declivity (Figs 1B, D , 4B , 6B ). The dorsal surface of the head in T. atriceps workers (Fig. 4A ) is covered by appressed pubescence that is relatively longer and sparser than in T. breviscapum , where it is abundant and relatively shorter (Fig. 6A ). The males of both species are relatively similar in morphology(Fig. 3 ), but the male of T. breviscapum can be differentiated from T. atriceps males because the former is on average slightly larger (0.63 ± 0.02 mm) and the scutellum is glabrous, while males of T. breviscapum are slightly smaller (0.62 ± 0.02 mm) and have decumbent hairs on the scutellum.

Genetic differentiation between Tapinoma atriceps and T. breviscapum

Final alignments had 648, 562, 422, and 655 bp for COI, LW Rh, Wg, and EPIC, respectively. For LW Rh, the length of the concatenated two flanking exonic sequences was 456 bp and for the intron 106 bp.

The greatest genetic variation among the molecular markers was observed in COI, followed by EPIC, Wg, LW Rh-ex, and LW Rh-in, with 114, 38, 15, 9, and 3 variable sites, respectively. Within the T. atriceps samples, the genetic pairwise distance ranged between 0.0-9.6% for COI, 0.0-2.0% for LW Rh-intron and Wg, 0.0-1.8% for EPIC, and 0.0-0.4% for LW Rh-exon. The mean genetic distance between T. atriceps and T. breviscapum was 9.4% (8.8-10%) for COI. For the nuclear markers, EPIC presented the greatest distance between the two species (4.6-4.7%), followed by Wg (1.4-5.9%), LW Rh-intron (1.1-2.3%), and LWRh-exon (1.5-1.7%).

In the phylogenetic reconstruction (Fig. 8A ), T. opacum is closer to T. atriceps and T. breviscapum than to T. melanocephalum . Tapinoma atriceps was recovered as a monophyletic group, sister to T. breviscapum . The Bayesian consensus trees of the individual analysis of each locus also recover both results (Suppl. material 4: Figure S1). Bayesian analysis of COI provided a topology similar to the Bayesian tree based on concatenated data, although with differences in branch lengths and node support of T. atriceps (PP = 0.71). The reconstructed separate trees with the nuclear loci also recovered T. breviscapum as a sister species to T. atriceps (Suppl. material 4: Figure S1) but the latter results in poor resolution among the sampled populations. Within T. atriceps , the topology derived from the concatenated data was relatively similar to the haplotype network (Fig. 8B ). The samples from Paraná, corresponding to haplotypes H05 and H06, presented a comparatively deep divergence from the rest of the species. The sample of T. atriceps from Minas Gerais was sister to the group from southern Brazil, the populations of this latter group showing little genetic structure. Most of the nodes were relatively well-supported (PP 0.85-1.00) except for the low value of support corresponding to the Antonina haplotype (H01).

Seven mitochondrial (COI) haplotypes of Tapinoma atriceps were identified for the eight analyzed sequences and a single mitochondrial haplotype for the only T. breviscapum sample (Fig. 8B ). The analysis estimated five unsampled haplotypes and found many mismatches between most of the haplotypes, evidencing high molecular variation for this marker. Haplotype H01, found in Paraná and Santa Catarina, is very close to haplotypes H02 and H03 and separated from them by only one nucleotide substitution; together, these form a group of haplotypes from southern Brazil. Other two haplotypes found in Paraná (H05 and H06) are relatively close to each other, and separated by one unsampled haplotype, but very different from the other haplotypes from Paraná. Haplotype H04 from Minas Gerais is closest to the H01-H03 haplotype group, separated by two unsampled haplotypes. Haplotype H07 from Misiones (Argentina) is closer to T. breviscapum haplotype (H08) and relatively close to the subset of haplotypes from the southeastern (H04) and southern Brazil (H01-H03). A haplotype network built with only the sampled populations of T. atriceps (Suppl. material 5: Figure S2) shows that the H07 haplotype is sister to the other haplotypes from southeastern and southern Brazil, which is congruent with the phylogenetic structure inferred from the concatenated molecular data (Fig. 8A ).

Figures

Figure 1. Tapinoma atriceps and T. breviscapum workers A head in frontal view of T. atriceps B body in lateral view of T. atriceps C head in frontal view of T. breviscapum D body in lateral view of T. breviscapum. Photographed specimens and those included in the molecular analyzes (haplotypes H 04 and H 08 respectively) are nestmates. Specimens deposited in DZUP. Photographs by M. Escarraga.

Figure 2. Tapinoma atriceps and Tapinoma breviscapum queen A body in lateral view of T. atriceps B head in frontal view of T. atriceps C anterior wing of T. atriceps D posterior wing of T. atriceps E head in frontal view of T. breviscapum F body in lateral view of T. breviscapum. Photographed specimens and those included in the molecular analyzes (haplotypes H 04 and H 08 respectively) are nestmates. Specimens deposited in DZUP. Photographs by M. Escarraga.

Figure 3. Tapinoma atriceps from Antonina, Reserva Natural Guaricica (Parana, Brazil) and T. breviscapum from Serra do Cipo (Minas Gerais, Brazil) male A habitus of T. atriceps B head in frontal view of T. atriceps C anterior wing of T. atriceps D posterior wing of T. atriceps E head in frontal view of T. breviscapum F habitus of T. breviscapum. Specimens deposited in DZUP. Photographs by M. Escarraga.

Figure 4. SEM microphotographs of Tapinoma atriceps from Serra do Cipo (Minas Gerais, Brazil) A worker head in dorsal view B worker mesosoma in lateral view C queen head in dorsal view D queen mesosoma in lateral view. The box with dashed lines indicates pubescence on the frons between the frontal carinae. Specimens deposited in DZUP.

Figure 5. Distribution map of Tapinoma atriceps and T. breviscapum. The figures with red outline correspond to the localities for the sequenced specimens. Dark green area in the main map corresponds to the Atlantic Forest domain defined by the WWF.

Figure 6. SEM microphotographs of Tapinoma breviscapum from Serra do Cipo (Minas Gerais, Brazil) A worker head in dorsal view B worker mesosoma in lateral view C queen head in dorsal view D queen mesosoma in lateral view. The inset with broken lines indicates finer and lesser separated pubescence on the frons between the frontal carinae. Specimens deposited in DZUP.

Figure 7. Morphometric scatterplot showing the relationship between HL and SL. The green circles correspond to the measurements of Tapinoma atriceps, while the purple squares correspond to those in T. breviscapum.

Figure 8. Evolutionary relationships between Tapinoma atriceps and Tapinoma breviscapum A bayesian phylogenetic reconstruction based on concatenated sequences of four molecular markers (COI, LWRh, WG, and EPIC). The scale bar represents substitutions per site and the number next to nodes the posterior probability B haplotype network including several populations of T. atriceps and a single sample of T. breviscapum (H 08). Every circle represents a different haplotype, the color corresponds to the geographical distribution, and the number between brackets corresponds to the number of mismatches between haplotypes.