Rasopone costaricensis

Identification
Montane; mandible striate or smooth; anterior clypeal margin truncate; side of head bare or with a few inconspicuous short setae; petiole scale-like. The species forms a clade of cryptic species that vary in size, mandibular sculpture, and petiole shape. They are all montane. Three unrelated species are within geographic and size range of the clade:

Rasopone cryptergates: lowland; petiolar node more cuboidal; posterolateral margins of head more angular.

Rasopone panamensis: lowland: petiolar node cuboidal.

Rasopone MAS010: smaller, HW 1.00 for both of the measured specimens of R. MAS010 versus 1.09 for the smallest measured specimen of R. costaricensis; petiole somewhat thicker (average PTI 59 vs 53).

Distribution based on Regional Taxon Lists
Neotropical Region: Costa Rica, Panama.

Biology
This species complex occurs in cloud forest habitats, from 1,000 to 2,000 m elevation (although one enigmatic collection is from 250 m elevation on the Osa Peninsula). Workers, and in one case a dealate queen, are collected in Winkler samples of forest floor leaf litter and rotten wood. Workers have been collected beneath epiphytes in treefalls and beneath rotten wood on the ground. Workers have been found both in closed-canopy cloud forest and in open pastures near cloud forest edges (beneath wood on the ground). In Monteverde, in addition to specimens from multiple Winkler samples, a worker was found in soil of a clay bank in a steep-sided ravine, and a worker was found beneath a stone. At Estación Pittier in the Talamanca range, a dealate queen was found beneath a stone. It is likely that the most common forms (of the various cryptic species) nest in the soil, with workers foraging in the litter. One nests beneath epiphytes. Males can be common in Malaise traps (associated with COI results). An alate queen was collected by an INBio Parataxonomist, at Tapantí National Park, on 30 October 1991. Cryptic species in the complex may specialize on particular microhabitats (e.g., beneath epiphytes; see Comments).

Nomenclature

 * . Rasopone costaricensis Longino & Branstetter, 2020: 11, figs. 8-11 (w.) COSTA RICA, PANAMA.
 * Type-material: holotype worker, 7 paratype workers.
 * Type-locality: holotype Costa Rica: Puntarenas, Monteverde, 10.30829, - 84.78498±50 m., 1617 m., 13.v.2014, cloud forest, ex sifted leaf litter, JTL8628-s (J. Longino); paratypes: 1 worker with same data, 2 workers with same data but 10.29905, - 84.78292±200 m., 1570 m., 30.iv.1989, 1 worker with same data but 10.3, -84.8±2 km., 1500 m., 26.vi.1984, 1 worker with same data but 10.30649, -84.81756±100 m., 1290 m., 21.xii.2013, 1 worker with same data but 10.30719, -84.78627±50 m., 1670 m., 13.v.2014, 1 worker with same data but 10.31156, -84.81459±50 m., 1480 m., 31.xii.2015.
 * Type-depositories: UCRS (holotype); CASC, DZUP, MCZC, UCDC, USNM (paratypes).
 * Distribution: Costa Rica, Panama.

Description
DNA sequence data, both COI and UCE, support a clade endemic to Costa Rican and adjacent Panamanian cloud forest. Within the clade, genetic evidence also supports the occurrence of multiple sympatric species at two intensively sampled sites. But the genetic data are fragmentary and the relationships among species across sites is unclear. We take the approach of referring to the entire clade as R. costaricensis, with the acknowledgment that further study will almost certainly result in the further splitting of the clade into component species. We describe here what we currently know of the sympatric forms at particular sites.

There is evidence that three sympatric species occur on the Barva transect, on Costa Rica's Caribbean slope. The three species differ in morphology, microhabitat, and COI sequence (as noted below).

There is evidence for at least three sympatric species, based on COI clusters in the BOLD database, on the peak of Volcán Cacao, a cloud forest site in Guanacaste, Costa Rica. The evidence comes mostly or entirely from males in Malaise traps, sampled by Alex Smith and others. Barva Form a and Form b cluster with one of the Cacao clusters. Form a and Form b differ from each other by about 5%, while each differs from the Cacao specimens by about 3%. Barva Form c clusters with the largest Cacao cluster, which contains over 120 specimens, with much less than 0.5% sequence divergence among them. A third Cacao cluster is small, and currently unassociated with any other specimens.

Other populations are known from Monteverde (the type locality) in the Cordillera de Tilarán, multiple cloud forest sites in the Cordillera de Talamanca and mountains of western Panama, and one lowland site near the Osa Peninsula.

Worker
Barva Form a: HW 1.32 (1.25-1.41, 6); HL 1.56 (1.51-1.65, 6); SL 1.20 (1.19-1.21, 3); PTH 0.90 (0.83-0.94, 5); PTL 0.50 (0.48-0.53, 5); CI 85 (83-86, 6); SI 88 (85-93, 3); PTI 56 (54-58, 5).

This is the largest of the three. The mandibles are smooth and shiny; the other two forms have striate mandibles. It is known from five separate collections: 1) 2 workers under epiphytes in an old treefall; 2) a worker and some brood in a rotten knot in a treefall; 3) a worker under epiphytes on dead wood at the edge between pasture and forest; 4) a Berlese sample of epiphytic material; and 5) a worker in a collection of mixed ants collected by hand. The first four collections were from a 1,500 m site and the last collection from an 1,100 m site. It is notable that no specimens were collected in the 350 miniWinkler samples of forest floor litter that were taken at the two sites.

Barva Form b: HW 1.19 (1.14-1.25, 10); HL 1.39 (1.33-1.47, 10); SL 1.08 (1.04-1.11, 3); PTH 0.85 (0.78- 0.93, 7); PTL 0.46 (0.42-0.51, 7); CI 86 (84-89, 10); SI 91 (87-93, 3); PTI 54 (52-61, 7).

This and Form c have striate mandibles. Form b is very similar to Form c, but the petiole is somewhat more tapering and scale-like. It occurred at the 1,500 m and 2,000 m sites on the Barva transect, where it was moderately abundant in miniWinkler samples. Parataxonomist Ronald Vargas collected a worker by hand at the 2,000 m site.

Barva Form c: HW 1.11 (1.09-1.14, 2); HL 1.28 (1.26-1.29, 2); SL 0.99 (0.98-1.00, 2); PTH 0.78 (0.77-0.78, 2); PTL 0.41 (0.41-0.41, 2); CI 88 (86-89, 2); SI 89 (87-90, 2); PTI 53 (53-53, 2).

This form has a relatively less scale-like node than Form b. It occurred at the 1,500 m site, from two collections. One worker was collected by hand from under rotten wood. Two workers were collected by student Andy Boring in an open pasture area, beneath rotten wood. These two collections were united by DNA sequence data (see below), which also supported their distinctness from Form b. However, a few specimens from miniWinklers from the 1,500 m and 2,000 m sites lacked sequence data and were intermediate in petiole shape, and thus could not be assigned to one form or the other.

other populations: HW 1.15 (1.09-1.21, 12); HL 1.33 (1.26-1.43, 12); SL 0.98 (0.91-1.09, 7); PTH 0.85 (0.72-0.95, 9); PTL 0.45 (0.39-0.53, 9); CI 86 (83-92, 12); SI 85 (76-91, 7); PTI 54 (50-58, 9).

Queen
other populations: HW 1.18 (1.08-1.27, 2); HL 1.32 (1.26-1.38, 2); SL 0.91; PTH 0.75; PTL 0.42; CI 89 (86- 92, 2); SI 84; PTI 55.

Type Material
HOLOTYPE: 1 worker, Costa Rica, Puntarenas: Monteverde, 10.30892 −84.78498 ±50 m, 1,617 m, 13-v-2014, cloud forest, ex sifted leaf litter, J. Longino, JTL8628-s, unique specimen identifier CASENT0635809]. PARATYPES: same data as holotype [1 worker,, CASENT0644841]; same data except 10.29905 −84.78292 ±}200 m, 1,570 m, 30-iv-1989, JTL2486-s [1 worker, , INBIOCRI001281356; 1 worker, , INBIOCRI001281355]; 10.3 −84.8 ±}2 km, 1,500 m, 26-vi-1984, JTL26Jun84/grou [1 worker, , INBIOCRI002278996]; 10.30649 −84.81756 ±}100 m, 1,290 m, 21-xii-2013, evergreen forest, in clay bank soil, JTL8467 [1 worker, CASC, CASENT0635758]; 10.30719 −84.78627 ±}50 m, 1,670 m, 13-v-2014, JTL8627-s [1 worker, , CASENT0635807]; 10.31156 −84.80459 ±}50 m, 1,480 m, 31-xii-2015, cloud forest, under stone, JTL9474 [1 worker, USNM, CASENT0632484].