Why Do Breeding Frogs Colonize Some Puddles More Than Others?
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~ Phyllomedusa 1(1):31-40, 2002 @ 2002 Melopsittacus Publicações Científicas ISSN 1519-1397 Why do breeding frogs colonize some puddles more than others? Paula Cabral Eterovick and Geraldo Wilson Fernandes Ecologia Evolutiva de Herbívoros Tropicais, Caixa Postal 486, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. 30123-970. Belo Horizonte, MG, Brasil. E-mail: [email protected] Abstract The composition of anuran communities at the Serra do Cipó (southeastern Brazil) was studied to familiarize ourselves with the species that breed in natural puddles. An experiment with artificial puddles was conducted to investigate the relationship of several physical properties of puddles to the pattern of their colonization by breeding anurans; the factors included were puddle size. permanency. pH, distance from a colonizing source, and abundance and richness of potential tadpole predators. Estimates of anuran species richness wet"e based on records of tadpoles and calling ma- les; species richness was higher in puddles with more types of tadpole predators. The number of species of tadpoles was higher in less ephemeral puddles with more predator types, and the number of species of calling males was higher in puddles having greater abundances of tadpole predators. Males may not be sensitive to tadpole-predation risk when they select calling sites, and the same physical characteristics of the puddles may attract both tadpole predators and anurans. For éxample, puddle permanency probably is such a feature, because in the less ephemeral puddles there were more species of tadpoles. as well as greater numbers and species richness of predators. Keywords: Anura habitat selection, tadpole predators, puddle permanency, southeastem Brazil. Introduction larger scales, factors such as local extinction and recolonization, and pond succession probably At a relatively small spatial scale, the spatial are important (Marsh and Borrell, 2001). and temporal distribution of anuran populations Behavior associated with se1ection of and species during reproductive activities may oviposition site contributes to spatial and tempo- be influenced by choice of oviposition site; at ral variation in patterns of abundance or population dynamics, and is influenced by habitat quality and interactions with conspecifics Received 23.05.2001 or predators (Resetarits and Wilbur, 1989; Accepted 02.10.2001 Marsh and Borrell. 2001 ). Some environmental . Phyllomedusa 111.Jonuorv 2002 Eterovirk nnd Fernand", factors known to influence habitat selection by occur every year. Anuran species richness may reproducing anurans are leaf litter availability, be determined by site selectivity by the surface area, depth of water (Marsh and Borrell, colonizers (which may be sensitive to variables 2001), shade (Wemer and Glennemeier, 1999), such as pool size or potential permanency) and and water chemistry and transparency (Leuven their ability to reach a given puddle and cope et al., 1986; Evans et al., 1996). with the prevailing environmental conditions. Isolation of water bodies is a major factor We determined the composition of anuran influencing anuran distribution, especial1y in assemblages in natural temporary puddles and species with limited dispersal abilities or in then tested whether puddle size, permanency, species that rely on breeding habitats that vary pH, distance from a colonizer source, and in space and time, such as temporary puddles abundance. and richness of potential tadpole (Marsh et al., 1999). The time taken by Tungara predators influenced anuran species richness in frogs (Physalaemus pustulosus) to colonize artificial puddles. available ponds increased with pond isolation at Barro Colorado Island (Marsh et al., 1999), and Methods in areas with isolated water bodies, amphibians may not be able to avoid oligotrophic and acid Study site waters by means of habitat selection as they do The study was conducted at the montane at less isolated oviposition sites (Leuven et al., meadows of the Serra do Cip6 (19°12'-19°20'S, 1986). 43°30'-43°40'W, 1095-1485 m e]evation), Mi- At larger spatial scales, species distribution nas Gerais, southeastem Brazi]. Many temporary depends on colonization abilities and successful wet]ands and some pudd]es appear during the establishment of species. Factors such as rainy season at the site and are used by anurans landscape pattems and proximity of suitable during reproductive activities. The rainy season habitats may facilitate dispersal, whereas factors starts in October or November and ends in such as pond chemistry and predation pressure March. may cause environmental resistance and prevent tecruitment (Bunnell and Zampella, 1999). Once Field activities colonization occurs, interspecific competition, We studied six natural puddles (Table 1) predation, and pond drying may interact to from November 1998 to March 2000. We produce pattems of distribution and composition sampled tadpoles and ca1ling males monthly of tadpole assemblages (Morin, 1983; Skelly, during the rainy season and bimonthly during 1996). In southeastem Michigan, Skel1y (1996) , the dry season. One man-made puddle (Puddle found that more permanent ponds had morea., 3) near the upper entrance of the National Park predators of larger sizes and greater taxonomic of the Serra do Cip6 is used by some frog diversity than did less permanent ponds. species and functions as a natural puddle. Differences in the ability of tadpoles to gamer Tadpoles that could not be identified in the field resources and avoid predation were reflected in were co1lected and identified by comparison their distributions among pond sizes: tadpoles with specimens housed in the co1lections of the from smal1, temporary sites spend more time Universidade Federal de Minas Gerais (UFMG), feeding and cah develop faster than tadpoles MG, Brazil, and Museu de Hist6ria Natura1 Uni- from large, permanent sites, where the larvae versidade Estadual de Campinas (ZUEC), Cam- must spend more time hiding from predators pinas, SP, Brazil. Specimens co1l~cted during . and, as a consequence, develop more slowly this study were deposited in the herpetological (Skel1y, 1997). co1lection of the Departmento de Zoologia of In temporary puddles, colonization must the UFMG. Phyllomedusa 1 ). Jonuorv 2002 Whv do breedinR froRs colinize some puddles more than others ~ õ' !'! :!I !") "' .. a " ~ Figure 1 Views of Puddle 4, the anuran colonizing source (A) and a 2m-diameter artificial puddle just after lining with a plastic tarpaulin (8). To investigate the co1onizing abi1ity of quickest after the rainy season remained intact. anurans that use pudd1es to reproduce and their These .were inc1uded as contro1s (Tab1e 2). We preferences regarding puddle size, we dug 18 ar- measured water pH of natural and artificial tificial puddles at increasing distances from a pudd1es containing water on 21 November 1999 natural puddle (Puddle 4; Figure 1A, Table 1) (Tab1es 1,2). that served as a colonizing source. The circular Potentia1 tadpo1e predators were counted puddles were of three different sizes -0.5, 1.0, and identified as one of seven types -Anisoptera and 2.0 m diameter. They had volumes of 0.05, naiads (Odonata), water bugs (Be1ostomatidae), 0.20, and 0.79 m3 respectively, and all were 25 waterscorpions (Nepidae), backswimmers cm deep. We positioned one puddle of each size (Notonectidae), water scavenger beet1es(Hydro- at 5, 10, 20, 40, 80, and 160 m (Table 3) from phi1idae), whir1igig beet1es (Gyrinidae), and the source along three 160-m transects starting spiders (Thaumasia sp., Pisauridae). A11of these at the natural puddle. The angles between taxa can prey upon anuran eggs and 1arvae Transects 1 and 2, and 2 and 3 were about 45° (Borror et al. 1992, Roth and Jackson 1987, and 35°, in order to position them as far apart as Sazimaand Bokermann 1977, Sea1e 1980, A. J. possible and away from a small permanent dos Santos, pers. comm.). Leptodactylus stream that passed about 10 m from the source lab)'rinthicus tadpo1esfeed on eggs and tadpo1es puddle. Frogs that breed in the stream do not of ~ther species of anurans (M. Martins, pers. reproduce in puddles. Therefore, we assumed comm.). A1though these tadpo1es cou1d be that they would not interfere in the experimental considered as an additiona1 predator, we did not colonization process. We visited these puddles inc1ude them in the ana1ysesbecause they on1y once or twice a month during the rainy seasons appeared in the 1ast samp1ing. of 1999/2000 and 2000/2001 until alI the puddles had dried. The most distant artificial Statistical analyses puddles dried quickly; and during the second We used stepwise multiple linear regres- rainy season, we attempted to prolong the sions (Systat, 1998) to relate puddle volume, . duration of these pudd1es by lining the basins permanency (number of months with water per with plastic tarpaulins (Fig. 1B). Most tarpaulins year), pH, distance from the colonizer source, were sto1enand only two of the smallest puddles number of tadpole predator types (richness), and farthest from the source that usually dried total number (abundance) of potential tadpole Phyllomedusa 1 11 ). Januarv 2002 Eterovick and Fernande.f Table 1 -Number of anuran species (tadpoles/calling males) found in six natural puddles at the Serra do Cip6. Southeastern Brasil from November 1998 to March 2000. The puddle used as colonizers source in the experiment with artificial pools is marked with an asterisk. Number Number of Number of Total Number of Volume of months