The genus Anisancylus Pilsbry , 1924 ( Planorboidea , Ancylinae ) in South America : species distribution and new records

Information on the distribution of Anisancylus Pilsbry, 1924 in South America is provided. For first time, we recorded A. dutrae (Santos 1994) in Minas Gerais state and 2 new localities in northeastern Brazil. Anisancylus obliquus (Broderip & Sowerby, 1832) is widely distributed in Chile, Peru, central and southern Argentina, Uruguay and southern Brazil while A. dutrae is restricted to Brazil. This freshwater genus shows a disjunct distribution in South America that could be explained by tectonics and evolution of the basins. To understand this peculiar distributional pattern, additional studies should be performed combining biogeographic and phylogeographic analyses.


Introduction
Anisancylus was established by Pilsbry (1924), based on the morphology of the shell's apex and the radula.He designated as type species Ancylus obliquus Broderip & Sowerby, 1832 (now Anisancylus obliquus), from Chile.Anisancylus is endemic to the Neotropical region and is composed of 2 nominal species: Anisancylus dutrae (Santos, 1994) and A. obliquus.Both species are common in lotic environments, under stones or on their surfaces, and, rarely, on fallen leaves (Santos 1994, Ovando et al. 2014).

DISTRIBUTION SUMMARY
As goal of the present study, we update the information of the distribution of Anisancylus species in South America based on material housed in scientific collections, records from the literature and material collected from several localities in Brazil.

Methods
This study was based on a literature review (using Scielo, Scopus and Web of Sciences data bases), material deposited in the following institutional collections: Academy of Natural Sciences of Drexel University, Philadelphia, Pennsylvania, USA (ANSP); Instituto de Biodiversidad Neotropical, Tucumán, Argentina (IBN); Museo Nacional de Historia Natural de Montevideo, Uruguay (MNHNM); Museo Nacional de Historia Natural de Santiago de Chile, Chile, (MNHNSC); Museo de Zoología de la Universidad de Concepción, Chile (MZUC); Instituto Oswaldo Cruz, Rio de Janeiro, Brazil (CMIOC); National Museum of Natural History, Washington, DC, USA (USNM); Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil (Col.Mol.UERJ) and material collected in various localities from Brazil.
Geopolitical boundaries and watersheds were used as overlays to produce the distribution map based on 107 records (16 records from Argentina, 18 from Brazil, 57 from Chile, 3 from Peru and 13 from Uruguay) (Table 1).To produce the map, GIS software was used taking in account layers of administrative areas, basins and water lines (rivers).Layers of administrative areas and water lines of Argentina, Chile, Uruguay and Brazil were obtained from DIVA resource (http://www.diva-gis.org/gdata).Localities without exact geographic coordinates in the original source were georeferenced using the GEO-Locate web application (http://www.museum.tulane.edu/geolocate/web/webgeoref.aspx) and Google Earth™.The identifications of specimens collected were corroborated with original descriptions, type material and morphological characters proposed in Santos (2003b).Shell microsculpture was analyzed under SEM in the Museu Nacional da Universidade Federal do Rio de Janeiro.
Anisancylus dutrae -  (Ohlweiler andLanzer 1993, Lanzer 1996).Our results report for first time the presence of this species in the La Plata Basin system of Paraná state.The La Plata basin extending over territories belonging to Argentina, Bolivia, Brazil, Uruguay and the whole of Paraguay, is the second largest drainage in South America (Berbery and Barros 2002).However, in our exhaustive bibliographic search and study of material from malacological collections, we did not find additional records of A. obliquus from other South American countries such as Bolivia and Paraguay.
The distribution of Anisancylus in South America shows peculiarities, and some hypotheses such as the tectonic evolution of the basins and the fossil record could explain this peculiar distribution.According to Leal (2011), part of the diversification of aquatic Neotropical biota resulted from the dynamics of rivers and watersheds during the Lower Cretaceous and Cenozoic.Vicariance processes and dispersion of this biota appear to have been mainly due to these events.Distribution patterns of some South American taxa such as fishes, ostracods and mollusks are examples of vicariance events (Leal 2011).Furthermore, the change of direction in the drainage and the establishment of its current pattern in the South American basins was the result of a series of tectonic processes, including the uplift of the Andes Mountain Range (Brito et al. 2007).The sea level fluctuations related to the glacial cycles of the Pliocene and Holocene also influenced on the hydrology of the South American basins (Leal 2011) together with the isolation of some Rivers and the formation of some lagoons (Hubert andRenno 2006, Ribeiro 2006).
The paleontological records show evidences about the presence of Anisancylus in freshwater environments in the past.Gundlachia taguataguensis Covacevich, 1971 [a nomen nudum] was described in lacunar facies of the Upper Pleistocene of San Vicente de Tagua Tagua, Chile.According Santos (2003b), this name corresponds with A. obliquus.For Uruguay, Olazarri (1988) mentioned Ancylus gayanus d'Orbigny, 1837 (= Anisancylus obliquus) in sediments of the Artigas Formation (Upper Pleistocene) and Martínez and Rojas (2004) cited this species as A. obliquus in the Sopas and Yucutujá formations.
Summarizing the tectonic processes, vicariance and dispersal (via animal transport) would explain the distribution patterns and the presence of A. obliquus in both sides of Andes.Additional studies are needed to understand these distributional patterns and affinities among the South American species of Anisancylus.Such studies must take an integrative approach by combining biogeographic and phylogeographic analyses, distribution modeling, and molecular systematics to allow inferences on the history of this genus and other Neotropical freshwater limpets.

Figure 7 .
Figure 7. Distribution map showing the localities of Anisancylus species in South America: Anisancylus obliquus (pink points) and A. dutrae (green points). .

Table 1 .
Distribution of Anisancylus in South America by localities and countries.
Ritossa and Gustavo (2014)2006: 112.AHaase 2012)in South America.The northernmost point of the occurrence corresponds to A. dutrae in Brazil (Baturité, Ceará state) while the southernmost corresponds to A. obliquus in Chile(Grande River, Tulahuen, Coquimbo  region).We recorded new localities of A. dutrae in the states of Ceará and Pernambuco and for first time this species is recorded in Minas Gerais (Lassance) and Mato Grosso do Sul (Bonito), extending the known distribution of this species to the southeast.Previous records of A. dutrae were located in the São Francisco river basin (the same basin where we found the new record in Lassance).The São Francisco River runs generally north in the states of Minas Gerais and Bahia, before turning east to form the border between Bahia on the right bank and Pernambuco (type locality of A. dutrae) and Alagoas states on the left bank(Simpson 1999).This basin has a high level of endemism (mainly fishes and birds) and has significant biogeographical interest(Camelier and Zanata 2014).One possible hypothesis to explain the presence of A. dutrae in Minas Gerais could be passive dispersal by fishes or birds(Green and Figuerola 2005, Kappes andHaase 2012).On the other hand, A. obliquus has records in Chile, Peru, central and southern Argentina, Uruguay and Southern Brazil.In Argentina A. obliquus is distributed in 2 disjunct areas, the first one located in central and southern Córdoba province and the second located on the southwestern border of Río Negro and Neuquén provinces.The record of A. obliquus reported from an Andean Patagonian lake in Argentina byRitossa and Gustavo (2014)is incorrect.The specimens they figured does not match the general shell morphology of A. obliquus.In Brazil, A. obliquus had been recorded only in Rio Grande do Sul state