Niche Structure of an Anole Community in a Tropical Rain
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3// NICHE STRUCTURE OF AN ANOLE COMMUNITY IN A TROPICAL RAIN FOREST WITHIN THE CHOCO REGION OF COLOMBIA DISSERTATION Presented to the Graduate Council of the North Texas State University in Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY By Fernando Castro-Herrera Denton, Texas May, 1988 Castro-H, Fernando, Niche Structure of an Anole Community in a Tropical Rain Forest within the Choco Region of Colombia. Doctor of Philosophy (Biology), May, 1988, 107 pp., 20 tables, 10 figures, 13 Plates, bibliography, 81 titles. Ten species of anoles at Bajo Calima within the Choco of western Colombia separate into two principal macrohabitat groups: (1) forest species (A. latifrons, A. chocorum, A. macrolepis, A. granuliceps A. anchicayae and A. lyra), and (2) those inhabiting openings and edges (A. maculiventris, A. chloris, A. biporcatus and A. notopholis). The 10 anoles further separate according to ground and vegetation dwellers: A. granuliceps, A. notopholis and A. macrolepis (the latter being a semiaquatic species); and A. latifrons, A. chocorum, A. anchicayae, A. biporcatus, A. chloris, A. lyra and A. maculiventris, respectively. There is a relation at Bajo Calima between the number of anole species and vegetational structural diversity. Anole diversity within a given macrohabitat is by perch microsite/microclimate heterogeneity. These are the two major ecological dimensions along which similarity is limited or resources are partitioned. Pattern of anole body size and perch microsite preference at Bajo Calima is similar to that on the Greater Antilles. Except in disturbed cultivated areas, no two anoles having similar body sizes share the same perch microsite within a macrohabitat. In cultivated areas the two more opportunistic species, A. chloris and A. anchicayae, overlap in microsite, but segregate slightly in size and microclimate preference. No taxonomic prey preference is indicated among the- most common arthropods in the anoles' diets. However, prey size range differs among anoles and is related to anole snout-vent length. Interspecific competition among anoles at Bajo Calima for prey, if it occurs, should be asymmetrical. Current interspecific competition at Bajo Calima is not evident because of macrohabitat and perch microsite/microclimate structural segregation, and/or body size-prey size preference. TABLE OF CONTENTS Page List of Tables........................................... v List of Figures.......................................... vii List of Plates........................................... viii Chapter IINTRODUCTION.................................... 1 II STUDY SITE...................................... 18 I:II SPECIES STUDIED................................ 31 Anolis granuliceps......................... 31 Anolis macrolepis.......................... 31 Anolis anchicayae.......................... 32 Anolis chioris............................. 33 Anolis maculiventris....................... 33 Anolis latifrons........................... 33 Anolis chocorum............................ 34 Anolis biporcatus.......................... 34 Anolis notopholis.......................... 34 Anolis lyra................................ 34 IV METHODS.......................................... 47 Macrohabitat Dispersion.................... 48 Abundance................................... 48 iii Microhabitat Dispersion... 49 Dietary Preference....... .... ... 49 Morphometrics............ 50 Data Analyses...'......... 51 V RESULTS...................... .... ... 54 Macrohabitat Dispersion.. .... ... 54 Microhabitat Dispersion.. .... ... 65 Dietary Dimension........ ............ 76 Morphometrics............ ............ 87 VI DISCUSSION................... ............ 91 Summary. ...... .. ..... .. 99 VII LITERATURE CITED............................... 101 iv LIST OF TABLES Table Page I. Known lowland anole species from the Choco Region.................................... 3 II. Comparison of the Choco Region and Caribbean Islands........................................6 III. Meteorological characterization of Bajo Calima.................................... 19 IV. Anole lizard community at Bajo Calima.......... 32 V. Macrohabitat dispersion........................ 55 VI. Macrohabitat niche overlap..................... 56 VII. Relative abundance of nine anole species....... 64 VIII. Perch microsites............................... 66 IX. Niche overlap for some perch microsites...........67 X. Microclimate dispersion........................ 68 XI. Microclimatic niche overlap.....................75 XII. Prey operational taxonomic units (OTUs).........77 XIII. Diets of 10 anole species from Bajo Calima......78 XIV. Dietary overlap................................ 79 XV. Diets according to OTU and volume.............. 83 XVI. Dietary summary by prey OTU and volume......... 86 XVII. Relation of prey volume to snout-vent length......................................87 XVIII. Body size comparisons...........................88 V XIX. Morphometrics of 10 anoles from Bajo Calima....................................89 vi LIST OF FIGURES Figure Page 1. Map of Colombia showing the Choco Region.......... 5 2. Temperature and relative humidity................ 15 3. Monthly rainfall at Bajo Calima study site........ 17 4. Dendrogram of macrohabitat similarity............. 58 5. Community coefficient and similarity for principal macrohabitats based on anole composition.................................. 60 6. Profile of four principal macrohabitats and anole species distribution at Bajo Calima.... 62 7. Dendrogram of perch microsite similarity.......... 70 8. Relation of perch microsite to macrohabitat, vegetational structure and anole body size... 72 9. Dendrogram of perch microclimate similarity....... 74 10. Dendrogram of diet similarity......................81 vii LIST OF PLATES Plate Page I. Topographic map of western Colombia showing isolation of the Choco Region by the Andean Mountains............................. 9 II. Aerial photograph of primary forest at the Bajo Calima study site........................11 III. Aerial photographs at the Bajo Calima study site showing agricultural and loggins effects on forests............................13 IV. Ground level views of primary forest at Bajo Calima study site............................ 24 V. Ground level views of primary forest showing stream covered with palms.................... 26 VI. Ground level views of secondary and open forests at Bajo Calima....................... 28 VII. Ground level views of cleared areas used for cultivation of African oil palms and fruit trees.................................. 30 VIII. Anolis granuliceps and Anolis macrolepis...........36 IX. Anolis anchicayae and Anolis chloris.............. 38 X. Anolis maculiventris and Anolis latifrons...........40 XI. Anolis chocorum and Anolis biporcatus............. 42 XII. Anolis notopholis and Anolis lyra.................44 XIII. Anolis sp. (new species) and Anolis gracilipes.... 46 viii CHAPTER I INTRODUCTION Anolis is the largest lizard genus in the new world, containing 200 known species distributed from the southern United States, throughout the Caribbean Islands, Central America and tropical South America. The systematics, behavior, ecology, biogeography, and evolution of many of these species have been studied intensively, particularly in the Greater and Lesser Antilles (e.g., Arnold, 1966; Collete, 1961; Fretwell, 1981; Gorman, et al., 1980; Hertz, 1976; Huey et al., 1976; Jenssen, 1977, 1981; Lazell, 1962, 1964, 1966, 1972; Lister, 1976; Moermond, 1977, 1979; Rand, 1964, 1967, 1969; Rand and Williams, 1969; Roughgarden, et al., 1983; Schoener, 1969, 1970a, 1970b, 1974, 1975; Schoener and Schoener, 1971a, 1971b; Williams and Rand, 1969; among others). Less work has been done with Central America Anolis (e.g., Andrews, 1971, 1979; Crump, 1971; Fitch, 1975; Guyer and Savage, 1987; Heatwole and Sexton, 1966; Heyer, 1967; Scott, 1976; Sexton and Turner, 1971 among others), and far less with those in South America (e.g., Ayala and Castro, in prep.; Dixon and Soini, 1975; Duellman, 1978, 1979; Rand and Humphrey, 1968; Vanzolini and Williams, 1970). 1 2 Studies on Anolis have provided insight into niche partitioning, competition, adaptive radiation, community structure and insular biogeography. Considerable theory and tests for hypotheses have derived from the Caribbean Island studies. Several comparative studies on mainland species have been conducted (Andrews, 1971, 1979; Fitch, 1975; Heatwole and Sexton, 1966; Pounds, in prep.; Williams and Rand, 1977), but more are needed to test hypotheses concerning expected differences between mainland and island lizard commnunities. This especially is true for tropical South America. The Choco region on the Pacific coast of Colombia (Figure 1) is an excellent area for comparative studies of anoles. It supports a high diversity (ca. 25; Table I) apparently representing Anolis lines from the southern and northern hemispheres (Anolis alpha and beta species, respectively; Etheridge, 1960). The Choco appears to be the biogeographical confluence for and shows the highest diversity of Anolis alpha and beta species. The Choco is comprised of ca. 89,497 km2 of lowlands, bounded by a branch of the Andes to the east (elevation ca. 3000 m), the Pacific Ocean to the west, a sub-xeric zone with some dry forests to the south-and Panama Isthmus with low mountains to the North. It is essentially a "biogeographical island" (Plate I) on South American continent which provides