Revista Chilena de Historia Natural 59: 135-150, 1986 The structure of Neotropical bat communities: a preliminary analysis La estructura de comunidades de murcielagos neotropicales: un análisis preliminar THEODORE H. FLEMING Department of Biology, University of Miami, Coral Gables, FL 33124, USA ABSTRACT I review the taxonomic composition and ecology of the bat fauna of Venezuela and examine the structure of several mainland and Canobean island phyllostomid bat communities in an effort to discern general rules in the assembly of Neotropical bat communities. The structure of species-rich phyllostomid communities appears to closely resemble the taxonomic, trophic, and morphological characteristics of the phyllostomid fauna. These communities contain clusters of morphologically similar species that tend to be less common and ecologically more specialized than a handful of abund- ant and broad-niched core species that are found in almost all faunas. As overall biological diversity decreases along rainfall and elevational gradients, specialist species drop out of communitiestwhereas the generalists persist. Phyllostomid generalists come from each of the major trophic and size adaptive zones into which this family has radiated. Mutualistic interactions with plants appear to have had a more profound influence on community structure in this family than have competitive interactions. Key words: Neotropical bats, community structure, competition, mutualism, zoogeography. RESUMEN En este trabajo reviso la composicion taxonomica y la ecologia de la fauna de murcielagos de Venezuela y examino la estructura de varias comunidades de murcielagos filostómidos en áreas continentales y de islas caribefias, con el prop6sito de discernir reglas generales en el ensamblaje de comunidades neotropicales de murcielagos. La estructura de comunidades de filostomidos con alta riq ueza de especies refleja claramente las caracteristicas taxonomicas, tr6ficas y morfologicas de la fauna de filostómidos en general. Dichas comunidades contienen especies morfologicamente similares que tienden a ser menos comunes y ecologicamente más especializadas que un pequefio grupo de especies nucleares abundantes y generalistas que se encuentran en casi todas las faunas. En la medida que la diversidad biológica decrece a lo largo de gradientes crecientes de pluviosidad y elevacion, las especies especialistas desaparecen de las comunidades, en tanto que las generalistas persisten. Los filostomidos generalistas provienen de cada una de las grandes zonas adaptativas troficas y de tamaiio dentro de las cuales la familia ha radiado. Las interacciones mutualistas con plantas parecen haber tenido una influencia más profunda que aquellas de tipo competitivas en la estructuracion comunitaria de esta familia de murcielagos. Palabras claves: Murcielagos neotropicales, estructura comunitaria, competencia, mutualismo, zoogeografia. INTRODUCION tionarily (e.g., papers in Strong et a/. 1984 ). The role of competition in struc- Patterns of species diversity and the factors turing communities has been a central that influence the structure of communities focus in these studies. Both views (non- (i.e., species richness and relative abun- random vs. random assemblages; impor- dance of species) have been of long- tance vs. unimportance of competition) standing interest to ecologists (Elton 1927, have their strong advocates (e.g., Wiens Hutchinson 1959, Cody & Diamond 1975). 1983, Brown & Bowers 1984, Grant & Recent studies of vertebrate community Schluter 1984, Simberloff 1984). To re- structure have focused on determining the concile different viewpoints, most investi- degree to which communities differ from gators agree that detailed field observations random assemblages of sympatric species and, whenever possible, controlled field that do not interact ecologically or evolu- experiments are needed. (Received 20 October 1985. Accepted 11 March 1986.) 136 FLEMING A variety of approaches has been used to New World (Table 1). Members of eight of study the structure of bat communities. An the nine families are insectivorous (with the ecological approach aimed at documenting exception of Noctilio leporinus, which is the relative abundances of species and their primarily a fish-eater). As reviewed by food niche relationships has been used by Gardner ( 1977), members of the Phyllosto- Fleming et al. (1972), Black (1974), LaVal midae, in which six subfamilies are cu- & Fitch ( 1977), and Bonaccorso ( 1979). A rrently recognized (Jones & Carter 1976) primarily morphological approach has been and whose species make up one-half of the used by Tamsitt (1967), McNab (1971), total fauna, consume a diverse array of Fenton (1972), Findley (1973, 1976), foods, including insects, vertebrates, nectar Findley & Black (1983), and Schum and pollen, fruit, and blood. (1984). Both approaches have led to the The bat fauna of Venezuela has been conclusion that many bat communities extensively sampled by field crews directed contain species that are tightly packed in by C. 0. Handley, Jr. (see Handley 1976) ecological and morphological space. The and can be used to obtain an overview of extent to which competitive interactions general trends in the species richness, geo- influence (or have influenced) interspecific graphic distributions, and relative abun- relationships, however, is still unclear. dance of Neotropical bats. I will use the I have three goals in this paper. First, I results of this faunal overview to predict will review our current knowledge of the the detailed structure of bat communities structure of Neotropical bat communities under the assumption that community with particular emphasis being placed on structure merely reflects faunal structure the family Phyllostomidae, the New World (or vice versa). This assumption will serve fruit bat family. Second, I will attempt to as a. null hypothesis in this study. identify general trends in the "assembly" of phyllostomid communities that are indi- cative of general "assembly rules" in Neo- Distributions by Life Zones tropical bat communities. Third, I will compare the results of this study with As shown in Fig. I, bat species are previous studies of insectivorous bat com- unevenly distributed among life zones (as munities and faunas conducted by Fenton designated by Hoi bridge 1947 in Venezue- (1972), Findley (1973, 1976), and Schum la. A strong diversity peak occurs in tropi- ( 1984 ), and with studies of bird communi- cal dry and tropical moist life zones, and a ties and faunas conducted by Karr & James secondary peak occurs in subtropical or (1975) and Ricklefs & Travis (1980), in an lower montane moist life zones. The insec- attempt to identify general assembly rules tivorous families show this basic pattern in communities of volant vertebrates. An (Fig. I) except that species are equally underlying theme in this analysis will be represented in both the tropical dry and the degree to which interspecific inte- tropical moist life zones whereas they are ractions (e.g., competition and mutualism) better represented in the subtropical moist influence bat community structure. I want than in the subtropical wet life zone. to emphasize the preliminary nature of this Distributions of modal life zones differ inductive exercise. A complete analysis among phyllostomid subfamilies (Fig. I). requires a much more extensive set of Phyllostomines (which are insectivorous- ecological, behavioral, and morphological omnivorous) peak strongly in tropical data, and a more sophisticated statistical moist life zones; glossophagines (which are analysis. I strongly suspect, however, that nectarivorous) peak in the tropical moist the general patterns that I have found will and subtropical moist zones; no strong hold up under more detailed scrutiny. dominance of one life zone occurs in the Humphrey & Bonaccorso ( 1979) discussed frugivorous carolliines; and two peaks this subject from a different viewpoint. occur in the frugivorous stenodermines (tro- pical moist and subtropical wet-lower mon- An Overview of the Neotropical Bat Fauna tane moist zones). These distributional data indicate that faunal and community di- versity is highest in lowland moist forests in The Neotropical bat fauna consists of both insectivorous and plant-visiting bats approximately 282 species classified in nine and that a secondary radiation has occurred families, six of which are endemic to the in certain groups at mid-elevations. NEOTROPICAL BAT COMMUNITIES: A PRELIMINARY ANALYSIS 137 TABLE 1 Families of Neotropical bats and their general food habits. Data taken from Nowak & Paradiso (1983) Familias de murcielagos neotropicales y sus habitos alimenticios generales. Datos obtenidos de Nowak & Paradiso (1983) FAMILY NUMBER OF SPECIES GENERAL FOOD HABITS Emballonuridae 21 Insectivorous Noctilionidaea 2 Insectivorous/piscivorous Mormoopidaea 8 Insectivorous Phyllostomidaea 143 Phyllostorninae (Phyllos.)b 34 Many insectivorous, occasionally frugivorous; some carnivorous Glossophaginae 34 Nectarivorous, occasionally (Glosso.) frugivorous & insectivorous Carolliinae 7 Frugivorous, occasionally (Caroll.) insectivorous &·nectarivorous Stenod erminae 57 Frugivorous, occasionally (Steno.) insectivorous & nectarivorous Brachyphyllinae 8 Nectarivorous & frugivorous (Brachy.) Desmodontinae 3 Sanguinivorous (Desmo.) Natalidae8 4 Insectivorous Furipteridaea 3 Insectivorous Thyropteridaea 2 Insectivorous Vespertilionidae 63 Insectivorous Molossidae 36 Insectivorous ~ Neotropical endemics. Abbreviations used in