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Phylogeography of the armadillo Chaetophractus villosus (Dasypodidae Xenarthra): Post-glacial range expansion from Pampas to Patagonia (Argentina)

We report a phylogeographic study of Chaetophractus villosus populations in Argentina. Control Region (CR) sequences (484 bp) were obtained for 76 C. villosus from 20 locations across the species whole distribution range. Seventeen new haplotypes were identified. The highest genetic variation and the earliest fossils were found in the Pampean Region, thus appearing as the most probable area of origin of the species. A general pattern of Contiguous Range Expansion (CRE) was revealed by Nested Clade Analysis (NCA) supported by mismatch analysis and Fus test. The Pampean Region would have been the pre-expansion area, while Patagonia would have been the main dispersal route of contiguous expansion, possibly after the Pleistocenic glaciations.

Robertsonian chromosome polymorphism of Akodon molinae (Rodentia: Sigmodontinae): analysis of trivalents in meiotic prophase

Akodon molinae con 2n = 42-43-44 y FN = 44 presenta un notable polimorfismo en el cromosoma 1 en poblaciones naturales y de laboratorio, los individuos 2n = 42 tienen un par 1 formado por dos cromosomas metacentricos grandes y son denominados homocigotos simples (SH); los individuos 2n = 43, heterocigotos (Ht), presentan un cromosoma 1 y dos cromosomas subtelocentricos de tamano medio 1a and 1b, que son homologos con los brazos largo y corto del 1, respectivamente; y los individuos 2n = 44 que son los doble homocigotos (DH) y presentan dos pares de cromosomas subtelocentricos 1a y 1b. Analisis de la metafases I y II meioticas han demostrado que se producen segregaciones anomalas con una alta frecuencia en los espermatocitos portadores de los cromosomas 1a and 1b. Ello alteraria a otros procesos, como la gametogenesis, la reproduccion y el desarrollo, disminuyendo la viabilidad individual y poblacional de los DH. No ha habido una explicacion satisfactoria para estos fenomenos. Para investigar elementos estructurales que pudiesen explicar tales alteraciones segregacionales, se estudio la sinapsis de bivalentes y trivalentes en espermatocitos en paquiteno de ejemplares SH, Ht y DH. De un total de 80 microesparcidos de nucleos de espermatocitos: en 16 nucleos de ejemplares SH se observaron 20 bivalentes autosomicos mas el bivalente XY; en 48 nucleos de Ht se observaron 19 bivalentes autosomicos, 1 trivalente y un bivalente XY; y en 16 nucleos de DH se observaron 21 bivalentes autosomicos mas el bivalente XY. Los trivalentes analizados mostraron apareamiento completo entre los brazos cortos de 1a y 1b conformandose un complejo sinaptonemico (CS) aparentemente normal con una longitud entre 1 µm y 2,8 µm. El CS de los trivalentes presento tres extremos telomericos correspondientes a los brazos: q1 y q1a, p1 y q1b y p1a y p1b, con placas de insercion a la envoltura nuclear de organizacion normal. En ninguno de los trivalentes se observo asinapsis o desinapsis entre p1a y p1b, ni asociaciones con el bivalente XY. En el 70 % de los espermatocitos estudiados el bivalente XY mostro apareamiento completo entre X e Y, con formacion de CS en toda la longitud del cromosoma Y. El 30 % restante presento apareamiento parcial con un CS de longitud variable a partir del extremo comun. Sobre la base de los resultados de este trabajo y los antecedentes existentes, se discute: 1.- que la configuracion obligada del trivalente con formacion de CS entre los brazos cortos de 1a y 1b, contribuye a asegurar la segregacion cuasi normal entre 1, 1a y 1b en la I anafase de la meiosis de los Ht; y 2.- que la coexistencia en los trivalentes de los cromosomas 1, 1a y 1b en los Ht, erosiona la integridad estructural y funcional de los brazos cortos de 1a y 1b, dano que seria acumulativo y que explicaria la viabilidad disminuida de los individuos portadores de estos cromosomas

Phylogeography of Cnesterodon decemmaculatus (Cyprinodontiformes: poeciilidae) in Southern Pampas, Argentina: ancient versus recent patterns in freshwater fishes

The Southern Pampean Area includes the southernmost limit of the Brazilian subregion and represents an interesting model to study how evolution of the landscape has affected the distribution of freshwater fishes in time and space. The hydrogeographic pattern of the region results from a combination of factors including climatic and sea level changes occurred since the Miocene and extending into the Quaternary. The hydrologic basins of this region are isolated, and have a similar ichthyological composition among them. Here we use a phylogeographic approach to infer how paleoclimatic changes affected the distribution of genetic variation in the populations of freshwater fishes. We analyzed the control region of mtDNA of Cnesterodon decemmaculatus and compared it with published data for the species Jenynsia multidentata and Corydoras paleatus in the same area. Cnesterodon decemmaculatus showed two main haplotypes with scarce divergence and wide geographical distribution within the area. The low divergence found between the Cnesterodon decemmaculatus haplotypes and the results obtained in the demographic analyses could suggest that the presence of this species in the area have a recent demographic history. These results are in contrast with the pattern reported for Jenynsia multidentata and Corydoras paleatus, where data suggest an ancient history in the area. The incongruence in the observed phylogeographical patterns could be due to the different ecological requirements of each species, and to the various responses of them to the environmental conditions resulting from geologic and paleoclimatic changes occurred in the region during the Late Quaternary.

Phylogeographic pattern of Jenynsia multidentata(Cyprinodontiformes: Anablepidae) in the southern boundary of the Brazilian Subregion, Argentina

The Atlantic drainage basins are located in the southern Pampean area, in the southernmost part of the Brazilian subregion. Tectonic and paleoclimatic phenomena, occurring during the Quaternary, have currently isolated these basins from the present hydrographic system. Their ichthyofaunal composition is similar to that of hydric systems located further northward. Jenynsia multidentata is a species with wide distribution in the Atlantic drainage basins, as well as in those Northern basins. Here we investigated the phylogeographic pattern of Jenynsia multidentata and analyzed its relationships with the paleoclimatic and geologic history of the region. The analysis of the population’s assemblage showed moderate genetic diversity, demographic equilibrium and marked genetic structure in the populations that occupy the extremes of the distributional range. The populations in the center of the range did not present genetic diversity, sharing a single haplotype. These results allow inferring that the presence of Jenynsia multidentata in the area results from historical demographic processes that are independent but complementary. In turn, these processes could arise from paleoclimatic changes occurred during the Quaternary.

Actinopterygii, Siluriformes, Loricariidae, Hypostomus aspilogaster (Cope, 1894). Distribution extension and first record for Argentina

The present work extends to Argentina the distribution of Hypostomus aspilogaster originally described from Uruguay River in southern Brazil. The examined specimens were sampled in the stream Mandisovi Grande, affluent of Uruguay River in Entre Rios province, and in Punta Lara, from Rio de la Plata basin, in Buenos Aires province, Argentina. This represents the first country record for this species.

Phylogeography of screaming hairy armadillo Chaetophractus vellerosus: Successive disjunctions and extinctions due to cyclical climatic changes in southern South America

Little is known about phylogeography of armadillo species native to southern South America. In this study we describe the phylogeography of the screaming hairy armadillo Chaetophractus vellerosus, discuss previous hypothesis about the origin of its disjunct distribution and propose an alternative one, based on novel information on genetic variability. Variation of partial sequences of mitochondrial DNA Control Region (CR) from 73 individuals from 23 localities were analyzed to carry out a phylogeographic analysis using neutrality tests, mismatch distribution, median-joining (MJ) network and paleontological records. We found 17 polymorphic sites resulting in 15 haplotypes. Two new geographic records that expand known distribution of the species are presented; one of them links the distributions of recently synonimized species C. nationi and C. vellerosus. Screaming hairy armadillo phylogeographic pattern can be addressed as category V of Avise: common widespread linages plus closely related lineages confined to one or a few nearby locales each. The older linages are distributed in the north-central area of the species distribution range in Argentina (i.e. ancestral area of distribution). C. vellerosus seems to be a low vagility species that expanded, and probably is expanding, its distribution range while presents signs of genetic structuring in central areas. To explain the disjunct distribution, a hypothesis of extinction of the species in intermediate areas due to quaternary climatic shift to more humid conditions was proposed. We offer an alternative explanation: long distance colonization, based on null genetic variability, paleontological record and evidence of alternance of cold/arid and temperate/humid climatic periods during the last million years in southern South America.

Evolutionary Genetics of Invasive Mammal Species Introduced in Argentina

Evolutionary genetics of invasive species has been unexplored in Argentina. Invasive alien species (IAS) have a wide geographical distribution, characteristic life cycles and great ability to adapt, establish and spread in a new environment. Recent advances in novel molecular technologies, the use of higher resolution genetic markers, and the research development on genetic variation of invasive species consolidated the importance of genetic aspects in the invasion process. Undoubtedly, the growing concern for the disturbances generated by invasive species on biodiversity and functioning of ecosystems was also determinant for the inclusion of the Invasion Biology within the broad field of Evolutionary Biology including relevant examples that address the evolutionary genetic aspects of biological invasions. Recent studies suggest that the invasion success of many species depends on their ability to respond to natural selection. Although the number of invasive species registered in Argentina far exceeds 600, little research has been done on invasive mammal species and only five of them were hitherto genetically analyzed. Presuming that invasion genetics is incorporated into the agenda of control and management organizations, it would allow integrating the ecological, genetic, and evolutionary biology aspects for knowledge of invasive species widely distributed in Argentina. The objective of this article is to highlight the importance of evaluating the genetic structure of invasive species for their management and to inform about the invasive species of mammals that were introduced in Argentina and have been or are being analyzed genetically.