Thermal Quality Explains Shift in Habitat Association from Forest to Clearings for Terrestrial-Breeding Frogs Along
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John Carroll University Carroll Collected Masters Theses Master's Theses and Essays Summer 2019 THERMAL QUALITY EXPLAINS SHIFT IN HABITAT ASSOCIATION FROM FOREST TO CLEARINGS FOR TERRESTRIAL-BREEDING FROGS ALONG AN ELEVATION GRADIENT IN COLOMBIA Zachary Lange John Carroll University, [email protected] Follow this and additional works at: https://collected.jcu.edu/masterstheses Part of the Biology Commons Recommended Citation Lange, Zachary, "THERMAL QUALITY EXPLAINS SHIFT IN HABITAT ASSOCIATION FROM FOREST TO CLEARINGS FOR TERRESTRIAL-BREEDING FROGS ALONG AN ELEVATION GRADIENT IN COLOMBIA" (2019). Masters Theses. 42. https://collected.jcu.edu/masterstheses/42 This Thesis is brought to you for free and open access by the Master's Theses and Essays at Carroll Collected. It has been accepted for inclusion in Masters Theses by an authorized administrator of Carroll Collected. For more information, please contact [email protected]. THERMAL QUALITY EXPLAINS SHIFT IN HABITAT ASSOCIATION FROM FOREST TO CLEARINGS FOR TERRESTRIAL-BREEDING FROGS ALONG AN ELEVATION GRADIENT IN COLOMBIA A Thesis Submitted to the Office of Graduate Studies College of Arts & Sciences of John Carroll University in Partial Fulfillment of the Requirements for the Degree of Master of Science By Zachary Kurtis Lange 2019 Table of Contents ..............................................................................................................1 Abstract .............................................................................................................................3 1. Introduction ...................................................................................................................4 2. Materials and Methods ..................................................................................................7 2.1 Study area and species .............................................................................................7 2.2 Field sites ...............................................................................................................10 2.3 Environmental variables ........................................................................................12 2.4 Mark-recapture surveys .........................................................................................13 2.5 Detection probability .............................................................................................13 2.6 Thermal assays ......................................................................................................14 2.7 Statistical analysis .................................................................................................16 2.8 Analysis of thermal quality ...................................................................................17 3. Results .........................................................................................................................18 3.1 Environmental data ...............................................................................................18 3.2 Mark-recapture ......................................................................................................20 3.3 Detection probability .............................................................................................22 3.4 Habitat associations ...............................................................................................22 3.5 Thermal preference ...............................................................................................25 3.6 Thermal quality .....................................................................................................25 1 3.7 Critical thermal maxima ........................................................................................28 4. Discussion ...................................................................................................................28 Acknowledgements .........................................................................................................34 References .......................................................................................................................35 Supplemental Materials ..................................................................................................48 Figure S1 .....................................................................................................................48 Figure S2 .....................................................................................................................49 Figure S3 .....................................................................................................................50 Figure S4 .....................................................................................................................51 Figure S5 .....................................................................................................................52 Figure S6 .....................................................................................................................53 Figure S7 .....................................................................................................................54 Table S1 .......................................................................................................................55 Table S2 .......................................................................................................................56 Table S3 .......................................................................................................................57 2 Thermal quality explains shift in habitat association from forest to clearings for terrestrial-breeding frogs along an elevation gradient in Colombia Abstract Tropical ectotherms are considered particularly sensitive to changes in the thermal environment from climate change and habitat alteration. Understanding how such species’ thermal physiology relates to their habitat associations in thermally heterogeneous landscapes may help us predict responses and develop sound conservation strategies for the future. We conducted a mark-recapture study of three terrestrial- breeding anuran species (Pristimantis medemi, P. savagei, P. frater) in adjacent forest and anthropogenic clearings at field sites spread across seven elevations (415-1350 m asl) in the Colombian Andes. We also performed thermal preference and critical thermal maximum assays in the lab to investigate the relationship between Pristimantis thermal physiology and habitat associations at each elevation. Thermal traits did not differ based on the habitat or elevation occupied; yet as elevation increased, two of three species became more abundant in clearings than in forest. We found that some species track their thermal preference to warmer clearings with increasing elevation. In essence, upland anthropogenic clearings are perceived as higher quality thermal habitat by two species in our study. Our findings suggest the importance of thermal heterogeneity and human- disturbed environments for the conservation of thermally sensitive species. 3 1. Introduction Organisms worldwide are experiencing novel thermal conditions brought about by anthropogenic forces, namely climate change (Parmesan & Yohe, 2003) and habitat alteration (Tuff et al., 2016). Although the threat of climate change is global in scale, habitat alteration has a more localized impact. However both threats typically lead to increasing environmental temperatures, and there is growing evidence of their synergistic negative effects on biodiversity (Hof et al., 2011; Nowakowski et al., 2016; Nowakowski et al., 2018a; Newbold, 2018). Across geographic regions and taxonomic groups, rising temperatures resulting from climate change have already induced a wide range of responses, including changes in behavior (Sinervo et al., 2010), distribution (Bustamante et al., 2005; Feeley et al., 2011), phenology (Parmesan & Yohe, 2003), and even local extinction (Sinervo et al., 2010). Moreover, warmer temperatures caused by habitat loss and degradation have resulted in changes to species assemblages, especially loss of thermally sensitive species from affected localities (Nowakowski et al., 2017; Frishkoff et al., 2019). Ectotherms, whose basic physiological functions are largely governed by environmental temperature, are especially vulnerable to rising temperatures from climate change (Deutsch et al., 2008; Newbold, 2018). Because ectotherms in the tropics often live close to their thermal limits (Sunday et al., 2014; Chan et al., 2016), even small changes in temperature can impact their distribution and survival (Colwell et al., 2008; Deutsch et al., 2008; Tewksbury et al., 2008). Furthermore, high levels of thermal specialization (Laurance et al., 2011), caused by exposure to relatively invariable temperatures (Janzen 1967), suggests that many tropical ectotherms have a limited capacity to physiologically 4 acclimate or adapt to increasing temperatures associated with climate change (Ghalambor et al., 2006; Shah et al., 2017). The lack of thermal variation in the tropics is one reason tropical mountains harbor high levels of biodiversity and endemism (Janzen, 1967; Graham et al., 2014). Locations close in proximity but differing in elevation may see very little overlap in environmental temperatures, resulting in the range-restricted, thermally constrained species seen in tropical montane areas (Janzen, 1967). As climate change progresses, tropical mountain ranges, such as the Andes, may become important refugia