Low Phylogeographic Structure of Rhinella Arunco (Anura: Bufonidae)
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Vásquez et al. Zoological Studies 2013, 52:35 http://www.zoologicalstudies.com/content/52/1/35 RESEARCH Open Access Low phylogeographic structure of Rhinella arunco (Anura: Bufonidae), an endemic amphibian from the Chilean Mediterranean hotspot Dayana Vásquez1, Claudio Correa1,2*, Luis Pastenes1, R Eduardo Palma2 and Marco A Méndez1 Abstract Background: The Mediterranean zone of central Chile (30° to 38°S) is one of the 25 diversity hotspots in the world. However, there are few phylogeographic studies which identify the factors that have influenced population diversification in the fauna of this area. In this study, we investigated the phylogeographic structure of Rhinella arunco, an anuran endemic to Mediterranean Chile, using 160 individuals from 23 localities representative of its entire distribution (32° to 38°S). Results: The haplotype network revealed four haplogroups, three of which overlap geographically and only one of which has an exclusive geographic distribution. An analysis of molecular variance indicated that neither watershed limits nor the main rivers in the current distribution of this species have been important geographic barriers against the dispersion of individuals. Finally, the Geneland analysis showed three population units, one of which concurs with one of the haplogroups found in the haplotype network. Together, these analyses indicated a low level of phylogeographic structure for this species. On the other hand, the highest levels of intrapopulational genetic variation were concentrated in the central part of the distribution (33° to 34°S), which may indicate an effect of Pleistocene glaciations on the genetic diversity of the populations in the extreme south of its range. Conclusions: The low phylogeographic structure observed in R. arunco is a rarely documented pattern for amphibians and contrasts with the phylogeographic studies of other vertebrates which inhabit the same zone. This result may be attributed to a series of attributes of bufonids, related mainly to water retention and their reproductive biology, which have allowed them to disperse and colonize an enormous variety of environments. Keywords: Phylogeography; Central Chile; Mitochondrial DNA; Pleistocene glaciations Background considered among the 25 biodiversity hotspots in the The central zone of Chile (30° to 38°S) is one of five areas world with a high conservation priority (Myers et al. 2000; of the planet which have a Mediterranean-type climate Sauquet et al. 2009). However, there are few studies which (Cowling et al. 1996; Amigo and Ramírez 1998; Luebert have identified the historical factors that may have affected and Pliscoff 2006; Armesto et al. 2007). From a biogeo- the diversification of the biota in this zone or in other re- graphic viewpoint, it is an isolated area, located between gions of the Southern Hemisphere (Beheregaray 2008). the Andes Range and the Pacific Ocean, flanked on the During the Pleistocene (1.8 M to 14,000 years ago), and north by the Atacama Desert and on the south by temper- more specifically during the Last Glacial Maximum ate forests (Bull-Hereñu et al. 2005); it has a high level of (LGM, 20,000 to 18,000 years ago), an ice sheet of ap- diversity and endemism, which has led to its being proximately 2,000 km long covered the extreme southern portion of South America, including the Andes Range * Correspondence: [email protected] from 56° to 34°S and the Coastal Range to 42°S in Chile 1Laboratorio de Genética y Evolución, Facultad de Ciencias, (Clapperton 1990, 1994; McCulloch et al. 2000). At their Departamento de Ciencias Ecológicas, Universidad de Chile, maximum extension, the glaciers extended to approxi- Las Palmeras, 3425 Santiago, Chile 2Laboratorio de Biología Evolutiva, Departamento de Ecología, mately 33°S. This phenomenon generated changes in the Pontificia Universidad Católica de Chile, Alameda 340, Santiago, Chile climate, landscape, and sea level, which may have affected © 2013 Vásquez et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Vásquez et al. Zoological Studies 2013, 52:35 Page 2 of 11 http://www.zoologicalstudies.com/content/52/1/35 the demographics and distributions of the biota, implying a individuals (Duellman and Trueb 1994; Beebee 1996). loss of genetic diversity due to important decreases in their These reproductive and physiological restrictions are usu- population sizes, followed by post-glacial demographic and ally accompanied by the presence of philopatry (Blaustein range expansions (Hewitt 2000; Sérsic et al. 2011). et al. 1994; Vences and Wake 2007). As a consequence, Topographically, Mediterranean Chile has tripartite re- these factors produce a high degree of genetic structure, lief (Niemeyer and Cereceda 1984; Armesto et al. 2007), even at short geographic distances, due to direct influ- that is, two parallel mountain chains with a north–south ences of water availability and temperatures (Buckley and orientation, the Andes Range and the Coastal Range, sepa- Jetz 2007). At a larger geographic scale, amphibian species rated by an intermediate depression or central valley. A usually have strong phylogeographic structures, which number of watersheds which originate in the Andes cross mainly appear to reflect historical events which have af- the intermediate depression forming wide valleys, the fected their populations (reviewed in Vences and Wake most important being the Aconcagua, Maipo, Maule, and 2007; some exceptions are Burns et al. (2007), Makowsky Biobío Rivers (Amigo and Ramírez 1998, Armesto et al. et al. (2009), and Chen et al. (2012)). 2007). The water volume of these rivers was influenced by Several recent genetic and phylogeographic studies in climatic changes in the Pleistocene. For example, melting different zones of Chile used amphibians as models (e.g., produced greater increases in water volume than those Méndez et al. 2004; Correa et al. 2010) or included spe- currently observed, and these phenomena may have been cies of amphibians which inhabit the Mediterranean barriers for the dispersion of some species (e.g., Liolaemus zone (Victoriano et al. 1995; Brieva and Formas 2001; monticola, Lamborot and Eaton 1997). Correa et al. 2008a). However, those studies used species Several studies have evaluated the effects of Pleistocene whose distributions span beyond the Mediterranean zone, glaciations and geographic barriers on the genetic struc- or used few samples within this zone, which were insuffi- ture of vertebrate species in the central zone of Chile. cient to evaluate hypotheses of historical genetic differen- Victoriano et al. (2008) compared patterns of genetic vari- tiation or to compare with co-distributed taxa. Rhinella ation of three lizard species of the genus Liolaemus sam- arunco (Molina, 1782) is one of two species of anurans en- pled in different latitudinal ranges (Liolaemus tenuis,31° demic to Mediterranean Chile; it is distributed from 32° to to 40°S; Liolaemus lemniscatus, 32° to 37°S; and Liolaemus 38°S (Cei 1962; Correa et al. 2008b), including the coastal pictus, 37° to 42°S). In L. lemniscatus, which mainly in- zone, the intermediate depression, and the Andean foot- habits the Mediterranean zone, they found more genetic hills up to 1,450 m (Figure 1). Its populations are closely variation in populations of the extreme north compared to associated with a landscape dominated mainly by scler- those of the south of its range. Those authors proposed an ophyllous matorral, where the river basins exhibit large effect of glaciations on populations of the south and fluctuations in the amount of available water. This study greater stability in the northern part of the distribution, investigated the phylogeographic structure of R. arunco in since the latter area was less impacted by periglacial ef- its entire distribution range, using a fragment of the con- fects. Unmack et al. (2009) studied populations of the trol region of mitochondrial (mt)DNA as a genetic freshwater fish Trichomycterus areolatus, which is distrib- marker. The objective was to evaluate whether Pleistocene uted in major watersheds from 30° to 45°S, and found no glaciations and/or geographic barriers (watersheds and riv- evidence of the effects of Pleistocene glaciations on its ers) were relevant factors which could explain the genetic genetic diversity. Those authors identified the topography differentiation of this species in its distribution range. of the central Chile and oceanic barriers as the most im- portant factors which limited the connectivity of popula- tions among river basins. Finally, in a genetic study of Methods populations of the colubrid Philodryas chamissonis from Localities and study material 29° to 38°S, Sallaberry-Pincheira et al. (2011) found a high We used 160 individuals from 23 localities representative of level of phylogeographic structure, four latitudinally differ- the entire distribution range of R. arunco, which extends entiated haplogroups, and high levels of intrapopulational from 32° to 38°S (Cei 1962; Correa et al. 2008b). Samples genetic diversity in the Maipo River basin (33°S). included the main river basins in the distribution of this Among vertebrates, amphibians have advantages as species (Figure 1, Table 1). Individuals included adults, juve- models for phylogeographic studies,