RECOVERY OF AMPHIBIAN SPECIES RICHNESS AND COMPOSITION IN A CHRONOSEQUENCE OF SECONDARY FORESTS IN NORTHEASTERN COSTA RICA By BRANKO HILJE A thesis submitted to the DEPARTMENT OF BIOLOGY FACULTY OF NATURAL SCIENCES UNIVERSITY OF PUERTO RICO RIO PIEDRAS CAMPUS In partial fulfillment of the requirements for the degree of MASTER OF SCIENCE BIOLOGY May 2011 Río Piedras, Puerto Rico Branko Hilje All rights reserved This Thesis has been accepted by the faculty of the: DEPARTMENT OF BIOLOGY FACULTY OF NATURAL SCIENCES UNIVERSITY OF PUERTO RICO RIO PIEDRAS CAMPUS In partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN BIOLOGY Thesis committee Advisor T. Mitchell Aide, Ph. D. Ingi Agnarsson, Ph. D. Alonso Ramírez, Ph. D. Alberto Sabat, Ph. D. 2 DEDICO ESTA TESIS A MI FAMILIA EN COSTA RICA, IVO, VERA E IRENA, POR TODO SU AMOR Y APOYO SIEMPRE. Y A FERNANDA Y A SERGIO QUE ME APOYAN DESDE EL CIELO. 3 ACKNOWLEDGMENTS I thank T. Mitchell Aide for his support and advice during these three years of my graduate studies. I want to thank my thesis committee for their valuable suggestions and contributions, Ingi Agnarsson, Alberto Sabat y Alonso Ramirez. S. Letcher and R. Chazdon provided data on the study sites and advices, and Brian Finegan (CATIE), the Tirimbina Rainforest Center, along with other private landowners brought permission to access the sites. Jeanette Paniagua, B. Paniagua and E. Salicetti of the Bosques Project at LSBS, and E. Arévalo, C. Quesada, L. Jacobs, A. Izquierdo and T. Chavarria helped with field work. Carlos Corrada, Carlos Milan, Giovany Vega, and Nathaniel Garcia helped with ideas and the recording devices. I want to thank the Graduate Program of Biology and Biology Department of the University of Puerto Rico, the Decanato de Estudios Graduados Universidad de Puerto Rico (DEGI), CREST- CATEC. Funding was provided by the Organization for Tropical Studies (OTS), Glaxo Pharmaceutical Fellowship (1243), National Science Foundation (NSF) (0640143, 0709598), Ministerio de Ciencia y Tecnología (MICIT) Costa Rica, Consejo Nacional para Investigaciones Científicas y Tecnológicas (CONICIT) Costa Rica, and Idea Wild. 4 TABLE OF CONTENTS CHAPTER 1. RECOVERY OF AMPHIBIAN SPECIES RICHNESS AND COMPOSITION IN A CHRONOSEQUENCE OF SECONDARY FORESTS IN NORTHEASTERN COSTA RICA ABSTRACT……………………………………………………………………………………………………………8 INTRODUCTION………………………………………………………………………………………………….10 METHODS……………………………………………………………………………………………………………14 Study sites and sampling design………………………………………………………….………….14 Species sampling........................................................................15 Visual Survey………………………….…………………………………………………………………………15 Acoustic Survey………………………………………………………………………………………………..16 Forest Characteristics……………………………………………………………………………………. 16 Statistical Analysis……………………………………………………………………………………………17 Species richness……………………………………………………………………………………………….17 Species composition…………………………………………………………………………………………17 RESULTS…………………………………………………………………………………………………………….18 Forest Characteristics………………………………………………………………………………………18 Species Richness……………………………………………………………………………………………….19 Species Composition…………………………………………………………………………………………19 DISCUSSION………………………………………………………………………………………………………20 LITERATURE CITED……………………………………………………………………………………………23 5 TABLES………………………………………………………………………………………………………………34 FIGURE LEGENDS……………………………………………………………………………………………….36 FIGURES…………………………………………………………………………………………………………….37 APPENDICES………………………………………………………………………………………………………39 2. CALLING ACTIVITY AS A MEASURE OF RECOVERY OF THE COMMON TINK FROG (DIASPORUS DIASTEMA) (ELEUTHERODACTYLIDAE) IN SECONDARY FORESTS OF THE CARRIBBEAN OF COSTA RICA ABSTRACT………………………………………………………………………………………………………….41 INTRODUCTION………………………………………………………………………………………………….42 METHODS……………………………………………………………………………………………………………43 Study sites…………………………………………………………………………………………………………43 Study species…………………………………………………………………………………………………….44 Sampling design……………………………………………………………………………………………….44 Data analysis…………………………………………………………………………………………………….45 RESULTS…………………………………………………………………………………………………………….46 DISCUSSION……………………………………………………………………………………………………….47 LITERATURE CITED……………………………………………………………………………………………50 TABLES………………………………………………………………………………………………………………55 FIGURE LEGENDS……………………………………………………………………………………………….56 FIGURES…………………………………………………………………………………………………………….57 APPENDICES………………………………………………………………………………………………………61 6 CHAPTER 1 RECOVERY OF AMPHIBIAN SPECIES RICHNESS AND COMPOSITION IN A CHRONOSEQUENCE OF SECONDARY FORESTS IN NORTHEASTERN COSTA RICA 7 ABSTRACT In some tropical regions, following the abandonment of agriculture and pastures, secondary forests can recover plant species richness and forest structure (e.g. canopy cover, biomass); however, the importance of these secondary forests for fauna is not clear. Secondary forests can benefit fauna by providing suitable habitats, connecting forests fragments, and increasing gene flow. Previous studies of forest regeneration have showed different levels of amphibian recovery. In Puerto Rico, 1-5 years old secondary forests achieved similar amphibian species richness and composition in comparison with old-growth forests, while in Brazil secondary forests from 14-19 years of recovery only recovered 60% of the species of old-growth forests. We evaluated amphibian recovery in secondary forests in northeastern Costa Rica, by assessing amphibian recovery in 12 secondary forests that vary in age of recovery and in three old-growth forests using visual and acoustic surveys. Our sites varied in terms of their landscape context (e.g. amount of surrounding forest), and forests characteristics associated with forest age (e.g. aboveground biomass, basal area, number of tree species, number of stems, leaf-litter depth), but there was no relationship between forest characteristics and amphibian species richness or species composition. We found that amphibians are recovering rapidly in secondary forests in Costa Rica, and even young forests (10-16 years) had similar species richness and composition in comparison with old-growth forests. These forests are providing suitable microhabitats and microclimate conditions for amphibians. 8 In addition, this study highlights the importance of landscape context. The abundance of amphibian species sources (e.g. forest patches) and connections between forests appear to be helping the species colonize these sites. Worldwide, the area of secondary forests is increasing, and our results show that these habitats are suitable for a diversity of amphibian species. If secondary forests have recovered from abandoned agricultural lands and pastures rather than deforestation or degradation, then these forests can help reduce amphibian population and species decline. Key words: amphibian recovery; Costa Rica; forest recovery; landscape; leaf- litter frogs; microhabitat; secondary forests. 9 INTRODUCTION Species richness and structure (e.g. canopy cover, biomass) of tropical forests can recover from different human activities such as deforestation, agriculture or pasture in 20-40 years (Aide et al. 2000, Janzen 2002, Letcher and Chazdon 2009). In some tropical regions the rates of deforestation are decreasing and the rates of reforestation are increasing (Aide and Grau 2004, Rudel et al. 2005). For example, in Dominican Republic and Puerto Rico secondary forests have emerged from abandoned agriculture lands (Rivera et al. 2000, Grau et al. 2003, Lugo and Helmer 2004, Grau et al. 2007). Secondary forests have also emerged from abandoned pastures for cattle in Puerto Rico, Dominican Republic and Costa Rica (Aide et al. 1996, Rivera et al. 2000, Janzen 2002); and there are examples of forests recovery from forest plantations (Mayaux et al. 2005), and following slash and burn agriculture (Rudel et al. 2005) in other neotropical ecosystems. Most of this recovery has occurred due to changes in socioeconomic patterns that involve rural-urban migration, increasing industrialization, and modern agriculture practices (Aide and Grau 2004, Wright and Muller-Landau 2006). These secondary forests can be important reservoirs for mature forest plant species (Wright and Muller-Landau 2006, Chazdon et al. 2009), although their value for fauna is still poorly understood (Dunn 2004, Gardner et al. 2007). Secondary forests can benefit fauna by providing suitable habitats (Faria et al. 2009), connecting forests fragments (Faria 2006), and increasing gene flow (Pardini et al. 2005). For example, secondary forests from 25-30 10 years old have similar ant species composition in comparison with 60 years old secondary forests in Puerto Rico, because they provide similar microhabitats (Osorio-Pérez et al. 2007). Similarly, the diversity, abundance and trophic structure of amphibians and reptiles increased as forest complexity and microclimate diversity increased during secondary succession (Heinen 1992, Williams et al. 2002, Gardner et al. 2007, Ríos-López and Aide 2007, Ficetola et al. 2008, Herrera-Montes and Brokaw 2010). Birds and mammals also increase in diversity and abundance as the habitat structure complexity increases during secondary succession (Johnston and Odum 1956, Barlow et al. 2007, Jayat et al. 2008). Furthermore, it has been shown that secondary forests can provide corridors between old-growth forests and plantations for bat populations in the Atlantic rainforest of Brazil (Faria 2006); and small mammal total abundances and levels of gene flow are higher in forests connected by secondary forests than in isolated forests fragments (Pardini