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Leptodactylid Frogs and the Brasilian Shield: An Old and Continuing Adaptive Relationship

1982; Wiley; Volume: 14; Issue: 1 Linguagem: Inglês

10.2307/2387754

1744-7429

Linda R. Maxson, W. Ronald Heyer,

Turtle Biology and Conservation

Relationships among 10 leptodactylid genera are probed using the quantitative molecular micro-complement fixation technique to estimate degrees of relatedness and times of divergence of major lineages. The leptodactylid genera tested are old, with many dating back to the late Mesozoic Era. Speciation events studied are most likely Miocene ard Oligocene in age. THE BRASILIAN SHIELD area of South America has been land positive since the Precambrian (Harrington 1962), with major uplift of coastal ranges occurring in the Cenolzoic (Simpson 1979). Today, several morphoclimatic domains cover the Brasilian Shield (Ab'Saber 1977). Among these, the Tropical Atlantic Morphoclimatic Domain (referred to as Atlantic Forest Domain or region herein) supports a rich and diverse frog fauna. One of the major frog elements of the Atlantic Forest region consists of members of the family Leptodactylidae; the Atlantic Forest Domain contains twice as many endemic leptodactylid genera as any other morphoclimactic domain in Brasil (Heyer 1975). The relationships among many of these leptodactylid genera are enigmatic (compare Lynch 1971, and Heyer 1975), and the historical zoogeography of the fauna of the Domain is poorly understolod. Classical morphological analyses of the leptodactylid genera have clarified many relationships, but several remain unclear, indicating a need for new data. Comparative protein studies have proven a fruitful avenue of inquiry where classical morphological analyses have left ambiguous results (e.g., see Avise 1976, Wilson et al. 1977). In particular, studies of the serum protein albumin, using the quantitative immunological technique of micro-complement fixation (MC'F), have been useful in deducing phylogenetic relationships among aInphibians (Maxson and Wilson 1975; Maxson 1977, Maxson et al. 1979). Recent studies have documented the effectiveness of MC'F studies of albumin in examining bo,th recent and more ancient (up to late Cretaceous) speciation events (Maxson and Maxson 1979). We therefore set out to, gather comparative albumin data on leptodactylid frogs in an attempt to clarify relationships among certain key genera of southeastern Brasil, and to provide a better understanding of the speciation events and zoogeography of the Atlantic Forest fauna. Two levels of relationships are examined: interand intra-Leneric. In order to place the Atlantic Forest leptodactylid relationships in better perspective, we include data from the northern and southern Andean leptodactylid frog fauna. This latter sample is included as it is taken from the probable site of the origin of the family in South America (beech forests of Southern Andes, Vuilleumier 1968, Lynch 1971, Heyer 1975), and the Andes themselves are young in relation to the Brasilian Shield. METHODS AND MATERIALS As sources of albumin, we used serum or tissues of over 30 species of leptodactylid frogs representing 11 genera. Antisera were raised in rabbits to purified albumins of 10 leptodactylid genera. Protocol for antisera production, titering, and MC'F experiments is given in Maxson et al. (1979) and Champion et al. (1974). Data are reparted in immunological distance units, where for albumin it has been determined that one unit of immunological distance is roughly equivalent to one amino acid difference between the albumins compared (Maxson and Wilson 1974). Antisera were produced to albumin from a single individual for large frogs or from several animals from the same population in case of small frogs 10 BIOTROPICA 14(1): 10-15 1982 This content downloaded from 157.55.39.223 on Wed, 24 Aug 2016 05:58:46 UTC All use subject to http://about.jstor.org/terms (Maxson and Maxson 1979) for the following species: Caudiverbera caudiverbera (Chile), Ceratophrys aurita (Brasil, Sao Paulo, Fazenda do Veado), Ceratophrys calcarata (Colombia), Cycloramphus dubius (Brasil, Sao Paulo, Boraceia), Hylodes pulchra (Brasil, Minas Gerais, Brejo de Lapa), Leptodactylus pentadactylus (Panama, Canal Zone, Frijoles), Megaelosia goeldi (Brasil, Rio de Janeiro, Teresopolis), Odontophrynus americanus (Paraguay), Proceratophrys appendiculata (Brasil, Sao Paulo, Fazenda do Veado), Telmwtobius oxycephalus (Argentina, Tucuman), and Thoropa miliaris (Brasil, Sao Paulo, Boraceia). Because polyploid species of Ceratophrys and Odontophrynus are known, species used for albumin antisera production were karyotyped and confirmed as diploids before being used. The Cycloramphus and Leptoaactylus antisera are being used for in-depth studies within each of these genera, and data on relationships among species of these two groups will be reported elsewhere. With these exceptions, cross reactions were performed on all available members of each genus for which antisera were made. The genera Cycloramphus and Megaelosia are restricted to the Atlantic Forest Domain. Most members of the genera Proceratophrys and Thoropa occur in the Atlantic Forest Domain; each genus has one species that occurs in adjacent domains. The genera Ceratophrys, Leptodactylus, and Odontophrynus have broad geographic distributions in South America with one or more species endemic to the Atlantic Forest Domain. The genera Caudiverbera and Telmatobius are restricted to the Andes. Voucher specimens are deposited in The National Museum of Natural History, Washington, D.C., and the Museum of Natural History at the University of Kansas, Lawrence, Kansas. RESULTS Antisera titers range from a low of 1300 (Leptodactylus pentadactylus) to a high of 6000 (Telmatobius, Megaelosia, and Odontophrynus). The average titer of 3400 and average slope of 375 is typical of that reported in earlier amphibian studies (Maxson et al.