Pheidole innupta

Longino, J. T., 2009, Additions to the taxonomy of New World Pheidole (Hymenoptera: Formicidae)., Zootaxa 2181, pp. 1-90 : 38

Pheidole innupta

Pheidole innupta Menozzi, 1931: 200 , fig. 7. Syntype major, minor worker, gyne: Costa Rica, Vara Blanca (Schmidt) [DEIB] (examined). Wilson, 2003: 165: junior synonym of P. alfaroi . Revived status.

Geographic Range

Costa Rica.

Biology

This species occurs only in cloud forest habitats, where it nests in large epiphyte mats in the canopy, and occasionally in dead wood near ground level. Foundress queens occur under epiphyte mats, and in some cases pleometrosis occurs (a group of over five queens together with brood and small workers has been observed). Colonies are large, with many workers pouring forth when the nest is disturbed. Soldiers tend to stay deep within the colony. The feeding habits of this species are unknown. Foragers have never been observed outside of the nests. Observations have been almost entirely during the day, so they could forage nocturnally. Alternatively, they may have specialized and perhaps plant-derived food sources within the nests. Scattered mealybugs may be found on epiphyte roots in the nests.

Comments

Pheidole innupta and Pheidole alfaroi appear identical with respect to size, shape, surface sculpture, and pilosity. They differ in color, distribution, and nesting behavior. It is common in ant taxonomy to disregard color as a species specific trait because it often varies intraspecifically, especially in polytypic species with allopatric or parapatric color forms. But in this case the two species appear to remain distinct in sympatry, with very little evidence of intergradation.

Both species are so far only known from Costa Rica, although similar montane species occur in the mountains of Colombia. Pheidole innupta workers are dark brown to black; P. alfaroi workers are light orange brown. Pheidole innupta occurs in cloud forest habitats in the northern cordilleras of Costa Rica, from the Cordillera Volcanica Central to the Cordillera de Guanacaste. Pheidole alfaroi is only known from the Cordillera Volcanica Central. Pheidole innupta occurs in heavily forested areas, nesting under thick epiphyte mats either in the canopy or in gaps where epiphyte-laden branches have fallen. Pheidole alfaroi occurs more on the ground, either under second growth forest or in cloud forest pastures, nesting under dead wood.

In the Project ALAS quantitative sampling along the Barva Transect in Costa Rica, intensive sampling was carried out at 1100m, 1500m, and 2000m elevation. The 1100m site was all dense primary forest. The 1500m site was an ecotone between primary forest and actively maintained cow pastures. The 2000m site was a mosaic of primary forest and regenerating second growth vegetation. Ants were collected using Winkler samples of sifted litter from the forest floor, flight intercept traps, and Malaise traps. At the 1100m site, P. alfaroi was moderately abundant in all sample types, while P. innupta was rare, occurring in only one of 20 Malaise traps. At the 1500m site P alfaroi was one of the most abundant ants, occurring in all sample types and in many hand collections of nests under dead wood, and P. innupta was absent. At the 2000m site, P. innupta workers were collected occasionally in Malaise traps and flight intercept traps, but never in Winkler samples from the forest floor litter. Pheidole alfaroi was absent. These observations suggest that P. innupta and P. alfaroi are ecological replacements, with P. innupta being arboreal and adapted to the coldest conditions and highest elevations, while P. alfaroi is ground-nesting and adapted to slightly warmer, lower elevation, and/or more disturbed habitats. This is an interesting species pair to observe with respect to climate change.