Photos from the Field: Changes in Species Richness of Twig-nesting Ants in Coffee Landscapes

Gillette, Ennis, Domínguez Martínez and Philpott (2015). Changes in Species Richness, Abundance, and Composition of Arboreal Twig-nesting Ants Along an Elevational Gradient in Coffee Landscapes. Biotropica, 47: 712–722. doi: 10.1111/btp.12263

The distribution, diversity, and assembly of tropical insects have long intrigued ecologists, and for tropical ants, can be affected by competitive interactions, microhabitat requirements, dispersal, and availability and diversity of nesting sites. Arboreal twig-nesting ants are limited by the number of hollow twigs available, especially in intensive agricultural systems. Ant diversity and abundance may shift along elevation gradients, but no studies have examined if the proportion of occupied twigs or richness of arboreal twig-nesting ants vary with elevation. In coffee agroecosystems, there are over 40 species of arboreal twig-nesting ants. We examined communities of twig-nesting ants in coffee plants along an elevational gradient to answer the following questions: (1) Do species richness and colony abundance decline with elevation or show a mid-elevation peak? (2) Does community composition change with elevation? (3) Is elevation an important predictor of change in ant abundance, richness, and relative abundance of common species? We surveyed 42 10 × 10 m plots in 2013 from 450 to1550 m elevation across a coffee landscape in Chiapas, Mexico. We sampled a total of 2211 hollow coffee twigs, 77.1 percent of which were occupied by one of 28 species of ants. Pseudomyrmex simplex was more abundant in lower elevations, whereas Pseudomyrmex ejectus dominated in high elevations. Species richness and the percent of occupied hollow twigs both peaked at mid-elevations (800–1050 m). In sum, we found that species richness, abundance, and composition of arboreal twig-nesting ants shift with elevation. These findings may provide important insights for understanding ant communities in coffee agroecosystems.

A twig nesting ant (Cephalotes sp.) collected from a coffee farm in Chiapas, Mexico. This ant uses its large head to block the doorway of its twig nest in hollow coffee twigs. (Photo by Katherine Ennis).

A twig nesting ant (Cephalotes sp.) collected from a coffee farm in Chiapas, Mexico. This ant uses its large head to block the doorway of its twig-nest in hollow coffee twigs. (Photo by Katherine Ennis).

A view of an intensive coffee farm in the Soconusco region of Chiapas, Mexico (Finca San Francisco) where rows of coffee plants are visible underneath the sparse pine tree canopy. At the other side of the valley is a less intensive coffee farm with a a more diverse and dense tree canopy (Finca San Cristobal) where coffee plants are not visible. (Photo by Penelope Gillette)

A view of an intensive coffee farm in the Soconusco region of Chiapas, Mexico (Finca San Francisco) where rows of coffee plants are visible underneath the sparse pine tree canopy. At the other side of the valley is a less intensive coffee farm with a more diverse and dense tree canopy (Finca San Cristobal) where coffee plants are not visible. (Photo by Penelope Gillette)

Up-close view of a moderate intensity coffee farm in the Soconusco region of Chiapas, Mexico (Finca Irlanda) with some trees in the genus Inga, coffee plants, and recently cut weed layer. (photo by Penelope Gillette)

Up-close view of a moderate intensity coffee farm in the Soconusco region of Chiapas, Mexico (Finca Irlanda) with some trees in the genus Inga, coffee plants, and recently cut weed layer. (Photo by Penelope Gillette)

This ant (Pseudomyrmex simplex) is one of the most commonly encountered twig-nesting ant found in hollow coffee twigs in the Soconusco region of Chiapas, Mexico. The abundance of this species is significantly higher at lower elevations (450-900m) and drops off at the higher end of the Arabica coffee range (1200-1500m). (Photo by Katherine Ennis)

This ant (Pseudomyrmex simplex) is one of the most commonly encountered twig-nesting ant found in hollow coffee twigs in the Soconusco region of Chiapas, Mexico. The abundance of this species is significantly higher at lower elevations (450–900m) and drops off at the higher end of the Arabica coffee range (1200–1500m). (Photo by Katherine Ennis)

A rare twig-nesting ant from the coffee study region, Pseudomyrmex boopis, nests in hollow coffee twigs. It is among the largest of the eight Pseudomyrmex species collected. (Photo by Katherine Ennis)

A rare twig-nesting ant from the coffee study region, Pseudomyrmex boopis, nests in hollow coffee twigs. It is among the largest of the eight Pseudomyrmex species collected. (Photo by Katherine Ennis).

An open hollow coffee twig revealing a nest of Pseudomyrmex simplex with workers and larvae. (Photo by Penelope Gillette)

An open hollow coffee twig revealing a nest of Pseudomyrmex simplex with workers and larvae. (Photo by Penelope Gillette).

A ominous rainy season sky, a heavily pruned Inga shade tree, and a topographically variable coffee landscape behind the twig-nesting ant research team in Chiapas, Mexico in June of 2013. From L to R: Katherine Ennis, Stacy Philpott, Gabriel Domínguez Martínez, Félix Ángel Rodríguez, and Penelope Gillette. (Photo by Penelope Gillette).

A ominous rainy season sky, a heavily pruned Inga shade tree, and a topographically variable coffee landscape behind the twig-nesting ant research team in Chiapas, Mexico in June of 2013. From left to right: Katherine Ennis, Stacy Philpott, Gabriel Domínguez Martínez, Félix Ángel Rodríguez, and Penelope Gillette. (Photo by Penelope Gillette).