Ants of Las Rejas

Ants of Las Rejas, Costa Rica

Report by John T. Longino and Michael G. Branstetter, The University of Utah. Student participants: Irene Calderon, Josue Corrales, Krissy Dominguez, Scott Heacox, Josh Kouri, Irene Mata, Mac Pierce, Marianela Solís.

This is a list of the ants of Las Rejas, Costa Rica, based on Project ADMAC sampling.

Project ADMAC carried out ant sampling in the Finca Naranjo - Las Rejas area from 23 June to 1 July 2015. The Finca Naranjo area was a small dairy farm, with cleared pasture on a bench overlooking the Rio Naranjo. Upslope from the pasture was a steep rocky slope covered with closed-canopy cloud forest. The history of the forest was unknown. There were scattered larger trees, abundant smaller trees, and a moderately dense understory. The forest was very wet and epiphyte-laden. Some cows were present just inside the edge of the forest, but not further up the slope. Second-growth forest lined the road into the farm along the Rio Naranjo. The bench was at 1500 m elevation, and the forest patch extended up to another road at 1700 m. Maxiwinklers were taken down to 1330 m in the steep-sided ravine of the Rio Naranjo and in the forest patch above the farm. One miniwinkler transect was taken just inside the forest patch, and one was taken in the second growth forest along the road in to the farm. Both transects were around 1500 m.

A road above the farm went to a site about 5 km away called Las Rejas. The road was on very steep slopes, going through forest patches and farms, gradually rising to 2000 m at Las Rejas. On one day we took a series of maxiwinkler samples along the road, distributed from 1500 to 2000 m.

The Las Rejas site was a mosaic of open pasture and second growth cloud forest of various ages. The two miniwinkler transects were taken in second growth forest near the road. A trail led up a ridge to 2270 m and then down to the Finca Naranjo area, and there were patches of tall oak forest along this trail. We took maxiwinkler samples along this trail.

For purposes of the species lists, we defined the Finca Naranjo site as samples within a km of the Finca Naranjo transects, from 1330 to 1700 m. The Las Rejas site was defined as all samples above 1900 m.

On the above figure, green points are maxiwinkler samples (with elevations). Ts in circles are miniwinkler transects.

Specimen records have been uploaded to the AntWeb database and are periodically updated. Names in the species list are linked to individual specimen records on AntWeb, from which a link can be followed to the general species page. These specimens function as site-specific vouchers, whose identities may change. The species names in the list are static text on this page. Following the specimen link to AntWeb will allow one to see if the name has changed.

There are at least 44 species at the Las Rejas site. A few notable discoveries include:

Adelomyrmex brenesi: This species was previously known only from one site at 2000 m on Volcán Barva, collected in 2002. The species is clearly rare; only two individuals were collected in a miniwinkler sample, in spite of abundant sampling at the site.

Leptanilloides gracilis: Prior to collecting at Finca Naranjo and Las Rejas, workers of this tiny subterranean species were only known from Mexico (Chiapas) and Guatemala. Putative males are relatively common in Malaise samples throughout Central America, but these were the first workers south of Guatemala.

Pheidole bucculenta: A group of cloud forest Pheidole have distinctive shape and sculpture. They are shiny, with no propodeal spines, and there are transverse arcuate carinae on the face. There are two species in Costa Rica with these characters: P. alfaroi and P. innupta. When I first saw the specimens from Las Rejas, I assumed they were P. alfaroi. But on closer inspection, the proportions of the head and scapes were very different and closely matched P. bucculenta from montane forest of southern Brazil. The types of P. bucculenta are brown, and the specimens from Las Rejas are orange, like P. alfaroi.

Ant List

Camponotus cuneidorsus

Crematogaster moelleri

Crematogaster nigropilosa

Cyphomyrmex salvini

Discothyrea horni_complex

Eurhopalothrix schmidti