Trophic structure in a large assemblage of phyllostomid bats in Panama

Norberte P. Giannini and Elisabeth K. V. Kalko Giannini, N. P. and Kalko, E. K. V. 2004. Trophic structure in a large assemblage of phyllostomid bats in Panama. - Oikos 105: 209-220. Bats of the family Phyllostomidae are fundamental components of Neotropical mammalian diversity and display the greatest dietary diversity seen in any mammalian family. We studied trophic structure in a species-rich local assemblage of phyllostomids for which dietary data were collected during 10 years on Barro Colorado Island, Panama. Correspondence analysis of > 3800 dietary records from 30 syntopic species showed a structure supporting traditional divisions of animalivorous and phytophagous phyllostomids. Putatively omnivorous species actually grouped among the latter. Phytophagous phyllostomids separated into Pi>er-specialists. Ficus- specialists, and eclectic plant eaters which in turn were the main consumers of flower products. Discrete dietary groups were compatible with several clades of the two current phylogenetic hypotheses of phyllostomids. We show that the trophic structure of the local contemporary assemblage is largely conservative with respect to traceable ancestral habits, strongly suggesting that overall trophic structure was likely determined historically. N. P. Giannini, Dept of Mammalogy, Am. Mus. ofNat. Hist., Central Park West at 79th Street, New York, NY 10024-5192, USA (norherto@amnh.org). - E. K. V. Kalko, Dept of Experimental Ecology (Bio III), Univ. of Ulm, Albert-Einstein Alle 11, DE-89069 Ulm, Germany. EKVK also at Smithsonian Tropical Research Institute, P. O. Box 2072, Balhoa, Panama. Assemblages of Neotropical rainforest bats show general patterns of species composition and rank abundance. Local assemblages studied so far are dominated by phyllostomids - leaf-nosed bats of the New World family Phyllostomidae (Brosset and Charles-Dominique 1990, dos Reis and Muller 1995, Ascorra et al. 1996, Kalko et al. 1996a, Bernard 1997, 2001, Kalko 1997, Simmons and Voss 1998, Kalko and Handley 2003, Bernard and Fenton 2002). The community importance of phyllostomids goes far beyond that compositional contribution, as phyllostomids play crucial functional roles as arthropod and vertebrate predators (Humphrey et al. 1983, Medellin 1988) and dispersers of seeds and pollen (van der Pijl 1941, 1956, 1957, 1972, Dobat and Peikert-HoUe 1985, Fleming 1988, 1991, Handley et al. 1991, von Heiversen 1993, Kalko 1997, Proctor et al. 1996). Phyllostomids represent the most diverse family not only of bats but also of mammals as a whole with respect to feeding habits (Gardner 1977, Findley 1993, Ferrarezi and Gimenez 1996, Kalko et al. 1996a, Freeman 2000, Wetterer et al. 2000). In recent classifications of trophic groups based on studies carried out on Barro Colorado Island, Republic of Panama (hereafter BCI), phyllosto- mids were the exclusive members of six out of 10 bat guilds (Kalko et al. 1996a, Schnitzler and Kalko 1998). Guild definition was based on three categories: foraging habitats, foraging mode, and predominant diet. The first category refers to the acoustic environment of the echolocating bat (uncluttered, background cluttered. Accepted 7 September 2003 Copyright © OIKOS 2004 ISSN 0030-1299