Arboreal twig-nesting ants and agricultural matrix quality: colonization, species richness, and reproductive success

Distance from forest patches and agricultural matrix quality influence insect conservation in agricultural landscapes. Yet, the importance of matrix quality for twig-nesting ants or impacts on nesting phenomena (e.g. reproduction, brood) is unknown. We examined whether distance from a forest fragment or shade management of coffee agroecosystems affects twig-nesting ants by investigating: a) colonization rate, b) richness and species composition, and c) reproductive success of ants colonizing artificial nests. We established plots in three farms differing in shade management (1 traditional polyculture [TP], 1 commercial polyculture [CP], and 1 shade monoculture [SM]) at increasing distances from a forest fragment (0-100 m) and in a nearby forest fragment. In each plot, we selected 10 coffee plants, and placed five artificial nests on coffee twigs. We harvested nests every three months for one year (July 2007 – June 2008). Colonization rates of artificial nests were highest in SM (37.9% ± 2% [SE]) and lowest in forest (1.2% ± 0.62%). Occupation rates did not differ with increasing distance from the forest (P>0.05). Species richness was highest in SM (37 species) and lowest in forest (5). Species composition differed in all sites (ANOSIM, P<0.05) except for CP and SM (P=0.219). Composition did not differ with distance to forest (P>0.05). Distance from forest did not affect reproductive success, but shade cover was important (r2=0.07). Results indicate habitat type, but not distance from forest affect twig-nesting ants. Low occupation in the forest may be due to high nest availability in the canopy, relative to coffee habitats.