Odontomachus davidsoni Hoenle, Lattke & Donoso, 2020

Hoenle, Philipp O., Lattke, John E., Donoso, David A., Beeren, Christoph von, Heethoff, Michael, Schmelzle, Sebastian, Argoti, Adriana, Camacho, Luis, Stroebel, Bernhard & Bluethgen, Nico, 2020, Odontomachus davidsoni sp. nov. (Hymenoptera, Formicidae), a new conspicuous trap-jaw ant from Ecuador, ZooKeys 948, pp. 75-105 : 75

Odontomachus davidsoni Hoenle, Lattke & Donoso sp. nov. Figures 2 , 3

Type material examined.

Complete list of localities in Suppl. material 9. Unique museum specimen identifiers are given in brackets after each specimen identification code.

Type locality.

Ecuador • Esmeraldas, Reserva Río Canandé; 0.5281N, 79.2070W; ca. 330 m; 21 February 2019; P. Hoenle & G. Villagomez leg.; collection code PE39; single worker near large fig tree in mature forest.

Holotype specimen.

Ecuador • 1 worker; Esmeraldas, Reserva Río Canandé; 0.5281N, 79.2070W; ca. 330 m; 21 February 2019; P. Hoenle & G. Villagomez leg.; collection code PE39; single worker near large fig tree in mature forest; specimen code PE39_01; [MEPN5074].

Paratype workers.

Ecuador • 3 workers; Esmeraldas, Reserva Rio Canande; 0.5252N, 79.2079W; ca. 320 m; 04 February 2019; P. Hoenle & A. Argoti leg.; collection code PE23; hand sampling on Cecropia tree, same location as Odonto_Phil; specimen codes PE23_01, PE23_02, PE,_23_03; [MCZ-ENT00731935].

Ecuador • 2 workers; Esmeraldas, Reserva Río Canandé; 00.5263N, 79.2117W; ca. 310 m; 06 February 2019; P. Hoenle leg.; collection code PE25; workers on recently large, fallen tree; specimen codes PE25_01, PE25_02; [RBINS IG 34167].

Ecuador • 4 workers; Esmeraldas, Reserva Río Canandé; 0.5238N, 79.2130W; ca. 330 m; 11 February 2019; P. Hoenle leg.; collection code PE36; nest in fallen branch in secondary forest (former cacao plantation); specimen codes PE36_01[RBINS IG 34167]; PE36_02, PE36_03, PE36_04; [MEPN_5075].

Ecuador • 4 workers; Esmeraldas, Reserva Río Canandé; 0.5252N, 79.2079W; ca. 320 m; 29 May 2018; P. Hoenle & A. Argoti leg.; collection code Odonto_Phil; hand sampling on Cecropia tree. Same colony as PE23; One point-mounted worker;specimen code: Odon_Phil_02 [DZUP 548819], (BOLD ID: ODECU002-19) and one point-mounted worker with the same locality data but collected on 20 May 2018, specimen code Odon_Phil_01 [DZUP 548820]; (BOLD ID: ODECU001-19); Two workers mounted with permanent glue on top of needle specimen codes Odon_Phil_3, Odon_Phil_4; [PH private collection]

Paratype queens.

Ecuador • 2 queens; Esmeraldas, Reserva Río Canandé; 0.5263N, 79.2129W; ca. 340 m; 25 January 2019; P. Hoenle leg.; collection code PE24; 2 alate queens, ex. light trap at the Río Canandé station, 8 pm.; specimen codes PE24_01 [MCZ-ENT00731935], PE24_02 [MEPN_5076].

Ecuador • 1 queen; Esmeraldas, Reserva Río Canandé; 0.5263N, 79.2129W; ca. 340 m; 13 April 2019; P. Hoenle leg.; collection code PE87, 1 alate queen, ex. light trap at the Río Canandé station, 9 pm.; specimen code PE87_01; [RBINS IG 34167].

Ecuador • 1 queen; Esmeraldas, Reserva Río Canandé; 0.5263N, 79.2129W; ca. 340 m; 09 May 2018; P. Hoenle & A. Argoti leg.; collection code Odon_Phil_queen; ex. light trap at Canandé Lodge; specimen code Odon_Phil_queen_01; [PH private collection].

Ecuador • 1 queen; Esmeraldas, Kumanii Lodge near Cotocachi-Cayapas Reserve; 0.7539N, - 78.9208W; ca. 40 m; 14 April 2006; L. Camacho leg.; ex. light tap; [QCAZI 15167].

Specimens used for 3D scan:

1 holotype worker (PE39_01), 1 paratype worker (PE23_01), 1 paratype worker (PE36_01), 1 paratype queen (PE24_01)

Specimens used for DNA barcoding:

Paratype workers DZUP 548819 (BOLD ID: ODECU002-19) & DZUP 548820 (BOLD ID: ODECU001-19)

Diagnosis of workers.

Measurements (N = 3): HL 3.91-4.09, HoW 2.67-2.76, HvW 1.65-1.74, ML 2.62-2.70, SL 4.22-4.43, EL 0.62-0.71, MsL 6.00-6.20, PrW 1.49-1.57, PtW 0.59-0.64, PtL 1.53-1.57, PtH 2.20-2.23, FL 5.28-5.37, CI 67.48-68.53, SI 158.05-160.74, MI 65.28-69.05.

Long (TL> 17 mm), but slender, ferruginous to yellow brown body with striae on cephalic dorsum from antennal insertions to vertex, mandible with over 15 pre-apical teeth and denticles, pronotal dorsum with concentric to transverse striae. Petiole strongly pedunculate with posteriorly inclined apical spine, gaster smooth and shining.

Description of the holotype worker.

Head elongate in dorsal view, anterior and posterior margins approximately of same width, posterior cephalic margin mostly transverse; head widest across eyes, at anterior one-third of head length; lateral cephalic margin posterior to eye sinuous. Median furrow deep, extends anterad to antennal fossa where it fades; occipital ridge distinctly delineated by antennal fossa, extending posteromedially, joining broad ridge that runs parallel to median furrow. Extraocular furrow broad and shallow, temporal prominence broad and weakly elevated. Cephalic surface with well-defined striae that diverge posterad from between frontal carina, reaching vertex, striae fade away on most of lateral cephalic surface with some striae reaching posteroventral cephalic surface. Ocular ridge smooth closest to eye and striate towards cephalic median region. Cephalic dorsal surface anterad of eye and between eye and antennal sclerite mostly smooth. Scape slender and slightly arched, SL longer than HL, scape widest just anterad of mid length, finely punctulate; funicular segment elongated and slender, segment I half as long as segment II.

Median clypeus mostly smooth and shining, posteriorly projecting as flattened triangular surface between frontal carina; carina defines narrow elevated region that descends posteriorly and extends to antennal fossa; frontal carina narrow, width not greater than scape width; carina steeply elevated over posteromedian clypeal surface. Ventral cephalic surface mostly smooth and shining. Labium drop-shaped, anteroventral surface very convex, PF 4,4. Buccal cavity with lateral hypostomal tooth. Mandibular masticatory margin with basal row of six denticles and eleven blunt triangular, relatively short teeth apicad of denticles. One or more teeth closest to apex may be broken. Mandibular apex tridentate, ventral tooth with basal tooth. Mandibular dorsal surface mostly smooth, with sparse piligerous punctulae, but dorsolaterally with abundant punctulae, ventral surface smooth and shining.

Pronotal dorsum with concentric striation that become progressively transverse and elongate medially towards posterior margin, in lateral view striae appear anteriorly transverse, medially curving and U-shaped, posteriorly oblique to almost vertical. Posterolateral pronotal margin with short convex lobe. Mesosoma relatively slender and elongate, in lateral view pronotal dorsal margin straight to weakly convex, forming a posteriorly ascending slope, mesonotum anterior margin slightly higher than posterior pronotal margin, mesonotal dorsal margin mostly straight to weakly convex, descending to metanotal groove. Dorsal mesosomal margin between metanotal sulcus and metanotal spiracle forms brief convexity, propodeal anterodorsal margin brief and convex, dorsal margin mostly straight, three times longer than declivity, declivity forms blunt obtuse angle with dorsal margin. Propleuron mostly smooth and shining with narrow transverse band of sparse weak rugulae anteriorly and posteriorly.

Mesonotum with transverse striae that extend uninterrupted laterally to anepisternum and ventrally to mesosternum, katepisternum mostly smooth and shining except for sparse striae anteriorly and posteroventrally. Bulla of metathoracic spiracle semispherical, weakly sculpted, opening shaped as transverse slit. Propodeum and metanotum transversely striate. Mesometapleural suture distinct, propodeal- metapleural suture weakly impressed. No carina or visible suture between mesopleuron and mesosternum, mesosoma in hypothetical cross-section at mid-length forms relatively uniform ovoid. Mesosternum with median longitudinal region raised as low and broad convex ridge; metasternal process bidentate, teeth short and blunt. Propodeal spiracle slit-shaped, transverse to oblique, not elevated.

Petiole in lateral view slightly pedunculate, node shaped as posteriorly sloping cone with acute apical needle, anterior node margin weakly convex, posterior margin vertical, straight to weakly convex; anteroventral process prominent, triangular; node smooth and shining. Abdominal tergite 3 in lateral view with anterodorsal margin forming single convexity to posterior margin, ascending posterad at approximately 45°; ventral margin of tergite 3 briefly concave at prora, then broadly convex and mostly at the same level as prora. Constriction between abdominal segments 3, 4 weak to negligible; gaster smooth and shining.

Coxae mostly smooth with abundant minute piligerous punctulae, punctulae denser on tibiae. Protibial apex with single seta, spur with basal translucent lamella. Probasitarsus with row of short, stiff hairs and parallel row of short setae opposite spur. Meso and metatibial apex each with two spurs, one pectinate, one simple; each also with 3 setae, each seta widely separated from each other. Body pilosity generally short and scattered with little pubescence; dorsal surface with few standing hairs: one on head where antennal fossa and nuchal carina almost meet, few on gastral sterna. Head and mandibular dorsum with sparse appressed pubescence, hairs straight on mandible and arched on head. Mandibular ventral surface next to masticatory margin with row of five flagellate long hairs plus two long trigger hairs at base. Scape with dense appressed pubescence, no standing hairs. Mesosoma with sparse appressed to subdecumbent small hairs, node with longer hairs; gaster mostly with sparse short, appressed to decumbent hairs with suberect hairs towards posterior end of gaster. Mandible and other buccal appendages, antenna, tibiae, and tarsi ferruginous brown to brown. Body mostly ferruginous to brownish yellow, head dark anterad and gaster darker posterad; trochanters and apex of femora tend to be darker.

Queen.

Measurements (N = 1): HL 4.30, HoW 3.8, HvW 1.99, ML 2.87, SL 4.46, EL 0.75, MsL 6.78, PrW 2.22, PtW 0.79, PtL 1.68, PtH 2.40, FL 5.46, CI 71.63, SI 144.81, MI 66.74.

Mesosoma developed for wings, head with three ocelli. Queen with larger dimensions than worker: HoW> 3.3; MsL> 6.5; PrW>1.9 mm., otherwise similar.

Male. Unknown.

Etymology. The species epithet is a patronym in genitive case honoring Stuart Carleton Davidson, the founder of Clyde’s Restaurant Group, Washington, DC. Stuart had a lifelong interest in our environment, and would have loved this amazing ant.

Comparison to similar species.

Odontomachus davidsoni most closely resembles O. hastatus by sharing a relatively large size, a red to brown color, a head which has in dorsal view a great difference between ocular and vertexal width, a relatively slender habitus, a bilobed metasternal process (Fig. 4A ), and a pedunculate petiole with a posterior inclining node topped by a long dorsal needle. Together with O. mormo both species also share an evenly convex anterior margin of abdominal tergite III that in lateral view ascends posterad at an approximate 45° angle (Fig. 4B ).

Compared to O. hastatus , O. davidsoni is clearly larger: The HL range of O. hastatus is 2.81-3.67 mm ( Brown 1976) versus 3.91-4.09 mm. Further, it has coarse striae throughout the dorsal cephalic surface, whereas the striae on O. hastatus are fine and limited to the area between the frontal carina and the antennal fossa, not extending to the occipital ridge. The pronotum in O. hastatus frequently presents smooth and shining areas on the pronotal disc or its sides, where it is always striate in O. davidsoni .

While the body size of O. davidsoni is similar to O. mormo (HL 4.14-4.36 ( Brown 1976), both species can be clearly distinguished by the striation pattern on the head: The striation in O. mormo does not reach the occipital ridge and there is instead a large and shiny area on the cephalic dorsum, while in O. davidsoni the entire cephalic dorsum is covered in coarse striae. Further, O. mormo does not possess a metasternal process, while O. davidsoni has a rounded bilobed metasternal process. O. mormo is almost hairless on the entire dorsal body surface including the petiole, whereas O. davidsoni body possesses a few appressed to decumbent hairs on the mesonotum, and many long erect hairs on the petiole. Overall, O. mormo has a more brownish coloration (very similar to O. chelifer ), in contrast to the red coloration in O. davidsoni .

When using the key to Neotropical Odontomachus species by Rodriguez (2008) this species will be taken easily to couplet 13, whereupon it will not fit any of the two alternatives: O. ruginodis nor O. laticeps . It is clearly larger than O. ruginodis , which also differs in its dark brown color, sessile petiole, and a very short stubby petiolar needle. O. laticeps is smaller, dark brown, with a sessile and relatively erect petiole bearing a shorter dorsal needle. Using the identification key in Brown (1976: 111), or the key in Antwiki (2015), this species is easily taken to couplet 14 where it becomes stuck as it fits neither alternative, O. bauri nor O. laticeps . Both of these ants are much smaller, dark brown, have a sessile, erect petiolar node with a relatively shorter dorsal needle, and the anterior dorsal margin of abdominal tergite III in lateral view is mostly vertical.

Molecular analyses.

We successfully amplified DNA barcodes of two Odontomachus davidsoni workers, a 569 bp fragment and a 668 bp fragment (GenBank accession numbers MN454765 and MN454766, respectively). The two specimens came from the same nest and had identical sequences. Odontomachus davidsoni barcodes were clearly distinguishable from COI sequences of other Odontomachus species (Fig. 5 ) as indicated by the minimum interspecific p-distance of 0.09 in pairwise comparisons (range of p-distances in 94 pairwise comparisons: 0.09-0.14; Fig. 5 ). A search in the BOLD identification database for the closest sequence match yielded similar results of 90.76% and 90.67% sequence similarity to O. chelifer (private, not published yet) and O. hastatus (GenBank accession number: KU504889), respectively (accession date 28 May 2019).

Biology and distribution.

Workers of O. davidsoni were only found in the Río Canandé Reserve and its neighboring reserve Tesoro Escondido (Fig. 6 ). Alate queens were collected with light traps in April 2006 (Kumanii Lodge, Cotocachi-Cayapas Reserve, leg. Camacho), April and June 2018, as well as in February, March and April 2019 ( Canandé Lodge, Río Canandé Reserve, leg. Hoenle). In 2018 and 2019 we frequently visited a tree in a selectively logged area of the Canandé Reserve where a few workers of the species were spotted. Foraging workers were observed predominantly during nighttime between 8 pm and 11 pm. On at least five occasions during daytime (i.e., between 9 am and 5 pm) the plot was visited, but only once foraging workers were observed. Although their exact nest position was not detected, workers were predominantly foraging on a liana attached to a Cecropia tree. The tree had a diameter of 63 cm at breast height and an estimated height of 20 m. Workers could be observed walking straight up on it until they were out of sight in a height of approx. 10 m. Workers were never seen foraging on the ground, and we thus assume that they primarily forage in the canopy. Workers were observed to sit still on the surface of leaves with their mandibles open, probably waiting to ambush prey (Fig. 7 ).

On the 11th of February 2019 we collected what looked like a complete nest in a fallen branch (Fig. 8 ; GPS data: 0.5238N, 79.2130W). The nest contained one dealate queen and 18 workers, as well as brood in all development stages (Fig. 9 ). We assume that this colony was not fully grown because it contained no alates (despite other colonies having alates at this time). The single nest entry was located under a bromeliad (Fig. 8A ). We opened all parts of the nest with a machete, revealing a 40cm long tubular chamber within the center of the branch (Fig. 8B ). It does not look like the ants themselves carved it, hence it was probably a pre-existing cavity.

We kept the colony for three months (11 February-15 April 2019) for further observations. The colony accepted various smaller insects as food, including flies, crickets, and termites. However, insects larger than 2 cm (e.g., large cicadas, moths, large crickets) were usually not accepted. Furthermore, the colony had ad libitum access to sugar water which was frequently visited. In accordance with field observations, the colony showed most activity during nighttime. No recruitment to offered food resources was observed. Due to the possibly threatened status of this ant species, the colony was released at the end of our observation time on a tree bromeliad nearby the Canandé lodge.

Figures

Figure 2. Odontomachus davidsoni sp. nov. stacking pictures A Worker paratype (specimen PE 23 _ 01) B Queen paratype (specimen PE 24 _ 01). Additional pictures in Suppl. material 7. Scale bars: 2 mm (left); 5 mm (right).

Figure 3. 3 D models of Odontomachus davidsoni sp. nov. A 3 D scan of Odontomachus holotype (PE 39 _ 01). B 3 D scan of queen (PE 24 _ 01). Additional 3 D models of two more paratypes in Suppl. material 8.

Figure 4. Odontomachus davidsoni ventral picture of metasternal process (specimen: Odon _ Phil _ 3) and lateral image of gaster (specimen Odon _ Phil _ 4).

Figure 5. Neighbor-Joining (NJ) tree of Odontomachus COI sequences. The NJ tree is based on p-distances (scale bar). First digit in parentheses gives the number of identified COI haplotypes of a given species and the second one the total number of available COI sequences for this species. GenBank accession numbers are given in Suppl. material 5 and Newick tree file are given in Suppl. material 6.

Figure 6. Odontomachus davidsoni collection sites. Blue dots show collection sites in Esmeraldas Province (Ecuador) within the reserves Rio Canande, Tesoro Escondido and Cotacachi-Cayapas.

Figure 7. Odontomachus davidsoni worker sitting on a leaf in its natural habitat.

Figure 8. Nest of Odontomachus davidsoni A Nest found under natural conditions with bromeliad covering the nest entrance B Nest architecture visible after opening a fallen tree branch with a machete. Scale bar: 100 mm.

Figure 9. Colony of O. davidsoni. This colony was kept in the field laboratory after taking it out from the twig nest (Fig. 8). The sole dealate queen is marked with a red arrow.