Fernando Torres-Perez

Abstract: Chagas disease is one of the most important vector-borne diseases in Latin America. The disease, caused by the flagellate protozoan Trypanosoma cruzi, is commonly transmitted to humans by Triatoma infestans in South America. Using mitochondrial DNA sequences, we assessed alternative biogeographic scenarios of dispersal of T. infestans using coalescence simulations. We also assessed phylogeographic structure and spatial genetics of T. infestans in Chile. Two major routes of dispersal in southern South America were supported including a dual-origin of T. infestans in Chile. Phylogeographic analyses identified two primary clades with Chilean haplotypes partitioned into either a northern cluster with Peruvian and Bolivian haplotypes or a north-central cluster with Argentinean and Uruguayan haplotypes. The north-central clade is further divided into two subgroups. Domestic and sylvatic T. infestans in central Chile were not segregated in the phylogeographic reconstruction. Spatial genetic analyses show higher distances in northern Chile, congruent with the presence of two divergent lineages of T. infestans. Phylogenetic evidence does not unequivocally support the hypothesized Bolivian origin of T. infestans, so we discuss alternative scenarios.

Abstract: Co-divergence between host and parasites suggests that evolutionary processes act across similar spatial and temporal scales. Although there has been considerable work on the extent and correlates of co-divergence of RNA viruses and their mammalian hosts, relatively little is known about the extent to which virus evolution is determined by the phylogeographic history of host species. To test hypotheses related to co-divergence across a variety of spatial and temporal scales, we explored phylogenetic signatures in Andes virus (ANDV) sampled from Chile and its host rodent, Oligoryzomys longicaudatus. ANDV showed strong spatial subdivision, a phylogeographic pattern also recovered in the host using both spatial and genealogical approaches, and despite incomplete lineage sorting. Lineage structure in the virus seemed to be a response to current population dynamics in the host at the spatial scale of ecoregions. However, finer scale analyses revealed contrasting patterns of genetic structure across a latitudinal gradient. As predicted by their higher substitution rates, ANDV showed greater genealogical resolution than the rodent, with topological congruence influenced by the degree of lineage sorting within the host. However, despite these major differences in evolutionary dynamics, the geographic structure of host and virus converged across large spatial scales.

Abstract: We report 2 cases of Sin Nombre virus (SNV) infection in field workers, possibly contracted through rodent bites. Screening for antibodies to SNV in rodents trapped in 2 seasons showed that 9.77% were seropositive. Quantitative real-time PCR showed that 2 of 79 deer mice had detectable titers of SNV RNA.

Abstract: Hantavirus cardiopulmonary syndrome (HCPS) is an emerging infectious disease first reported in Chile in 1995. Andes hantavirus (ANDV) is responsible for the more than 500 cases of HCPS reported in Chile. Previous work showed that ANDV is genetically differentiated in Chile across contrasting landscapes. To determine whether the reservoir rodent (Oligoryzomys longicaudatus) populations are also geographically segregated, we conducted range-wide spatial genetic analyses of O. longicaudatus in Chile using the mitochondrial DNA cytochrome b gene. Given that landscape structure influences the incidence of hantavirus infections, we also tested 772 O. longicaudatus specimens for antibodies to ANDV captured during the period 2000-2006. Population genetic analyses of O. longicaudatus are largely congruent with those reported for ANDV, with the host primarily differentiated according to three defined ecoregions, Mediterranean, Valdivian rain forest and North Patagonian rain forest. Significant differences in the relative prevalence of anti-ANDV antibodies in rodent samples also were found across the three ecoregions. We relate these results to the number of reported human HCPS cases in Chile, and discuss the importance of landscape differences in light of ANDV transmission to humans and among rodent populations.

Abstract: Powassan virus (POW) is a tick-borne flavivirus distributed in Canada, the northern USA and the Primorsky region of Russia. POW is the only tick-borne flavivirus endemic to the western hemisphere, where it is transmitted mainly between Ixodes cookei and groundhogs (Marmota monax). Deer tick virus (DTV), a genotype of POW that has been frequently isolated from deer ticks (Ixodes scapularis), appears to be maintained in an enzootic cycle between these ticks and white-footed mice (Peromyscus leucopus). DTV has been isolated from ticks in several regions of North America, including the upper Midwest and the eastern seaboard. The incidence of human disease due to POW is apparently increasing. Previous analysis of tick-borne flaviviruses endemic to North America have been limited to relatively short genome fragments. We therefore assessed the evolutionary dynamics of POW using newly generated complete and partial genome sequences. Maximum-likelihood and Bayesian phylogenetic inferences showed two well-supported, reciprocally monophyletic lineages corresponding to POW and DTV. Bayesian skyline plots based on year-of-sampling data indicated no significant population size change for either virus lineage. Statistical model-based selection analyses showed evidence of purifying selection in both lineages. Positive selection was detected in NS-5 sequences for both lineages and envelope sequences for POW. Our findings confirm that POW and DTV sequences are relatively stable over time, which suggests strong evolutionary constraint, and support field observations that suggest that tick-borne flavivirus populations are extremely stable in enzootic foci.

Abstract: Triatoma infestans is one of the main domestic vectors of Chagas disease. Reports of wild habitat occurrences have recently increased. In Chile, after a successful elimination campaign of T. infestans domestic infestation, a sylvatic focus was reported in bromeliads in the metropolitan region. Here, we report a new focus of sylvatic T. infestans inhabiting rock piles in the Valparaíso region in central Chile. All T. infestans captured were nymphal instars living among the stones, which were inhabited by several mammal species, along with the sylvatic triatomine vector Mepraia spinolai. We found a prevalence of infection with Trypanosoma cruzi of 36.54% in T. infestans, similar to the previous report for sylvatic specimens from bromeliads. Sylvatic populations of T. infestans should be studied at different geographic scales to elucidate their role in the maintenance of the sylvatic transmission cycle of T. cruzi and their possible role in threatening the domestic elimination of this vector. This information should be used to re-design the control programs in Chile to avoid the re-establishment of the domestic cycle.

Abstract: Andes virus (ANDV) is the predominant etiologic agent of hantavirus cardiopulmonary syndrome (HCPS) in southern South America. In Chile, serologically confirmed human hantavirus infections have occurred throughout a wide latitudinal distribution extending from the regions of Valparaiso (32 to 33{degrees}S) to Aysen (46{degrees}S) in southern Patagonia. In this study, we found seropositive rodents further north in the Coquimbo region (30{degrees}S) in Chile. Rodent seroprevalence was 1.4%, with Oligoryzomys longicaudatus displaying the highest seroprevalence (5.9%), followed by Abrothrix longipilis (1.9%) and other species exhibiting < = 0.6% seropositivity. We sequenced partial ANDV small (S) segment RNA from 6 HCPS patients and 32 rodents of four different species collected throughout the known range of hantavirus infection in Chile. Phylogenetic analyses showed two major ANDV South (ANDV Sout) clades, congruent with two major Chilean ecoregions, Mediterranean (Chilean matorral [shrubland]) and Valdivian temperate forest. Human and rodent samples grouped according to geographic location. Phylogenetic comparative analyses of portions of S and medium segments (encoding glycoproteins Gn and Gc) from a subset of rodent specimens exhibited similar topologies, corroborating two major ANDV Sout clades in Chile and suggesting that yet unknown factors influence viral gene flow and persistence throughout the two Chilean ecoregions. Genetic algorithms for recombination detection identified recombination events within the S segment. Molecular demographic analyses showed that the virus is undergoing purifying selection and demonstrated a recent exponential growth in the effective number of ANDV Sout infections in Chile that correlates with the increased number of human cases reported. Although we determined virus sequences from four rodent species, our results confirmed O. longicaudatus as the primary ANDV Sout reservoir in Chile. While evidence of geographic differentiation exists, a single cosmopolitan lineage of ANDV Sout remains the sole etiologic agent for HCPS in Chile.

Abstract:

Abstract: The delimitation of species is a major issue in systematic biology and has been a re-emerging discipline in the last decade. A number of studies have shown that the use of multiple data sets is critical for the identification of cryptic species, particularly in groups with complex evolutionary histories. Liolaemus monticola is a montane lizard species distributed in central Chile (32°201342°S), with four described subspecies in a latitudinal gradient from north to south: L. m. monticola, L. m. chillanensis, L. monticola ssp. and L. m. villaricensis. In order to test the systematic status and phylogenetic relationships of the taxa included in the L. monticola group, we analysed morphological (morphometric and meristic) and molecular (allozyme and mitochondrial DNA) data sets. The results of the morphological analyses showed that meristic variables correctly assigned individuals with higher accuracy than did morphometric characters. The results of the analyses of allozyme data revealed eight diagnostic loci that are evidence for significant differences among the four L. monticola subspecies. Phylogenetic analyses with mitochondrial DNA data, including additional species, showed that the L. monticola group is polyphyletic. We postulate that the four current subspecies represent independent evolutionary lineages and must be raised to the specific level as L. monticola, L. chillanensis and L. villaricensis. The taxonomic status of the unnamed L. monticola ssp. remains unresolved, although we provide a preliminary proposal.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 6352013650.

Abstract: Allozyme variability was assessed within and between 18 samples of four chromosomal races of the Liolaemus monticola complex: "Southern, 2n=34", "Northern, 2n=38-40", "Multiple Fission, 2n=42-44" and "Northern modified 1, 2n=38-40". This is an endemic montane Chilean lizard characterized by extensive chromosomal polytypy. The population genetic structure was studied by means of allozyme electrophoresis of 20 presumptive loci. Population heterogeneity analysis carried out by the estimation of Weir and Cockerham's F-statistic (θ), demonstrated substantial genetic differentiation among populations. The u-statistic, genetic distance data and multivariate analyses show that genetic variation is distributed into geographically coherent population groups in accordance with three of the four chromosome races. The greatest differentiation occurs between all populations of the "Southern, 2n=34" race and a second group that includes all populations from the "Northern, 2n=38-40" plus "Northern mod 1, 2n=38-40" races, separated from the "Multiple Fissions, 2n=42-44" race. As riverine barriers also separate these chromosomal races, we do not attribute the observed differentiation to isolation-by-distance or the chromosome characterization for each race. Possible routes of migration and colonization are proposed.

Abstract: Liolaemus monticola is a mountain lizard species, with a widespread distribution from central Chile that displays several highly polymorphic chromosomal races. Our study determined the phylogeographic structuring and relationships among three chromosomal races of L. monticola in Chile. Mitochondrial DNA (mtDNA) sequences of the cytochrome b gene were examined using the following phylogenetic methods: maximum parsimony, maximum likelihood, Bayesian inference and nested clade phylogeographic analyses (NCPAs). These methods revealed two major monophyletic clades (north and south) in the L. monticola species, with non-overlapping geographical locations separated by the Maipo and Yeso rivers (except one hybrid, from a zone of secondary contact). The NCPA showed that a past fragmentation process likely resulted in the separation of the two clades. The southern clade includes all samples of the 'Southern, 2n = 34' race; the northern clade is comprised of all remaining derived chromosomal races: the 'Northern, 2n = 38-40 and the Multiple Fission, 2n = 42-44' races. Our results support the hypothesis of a geographical and genetic split resulting from allopatric processes caused by riparian barriers acting over a long time period. The inferred biogeographical scenario shows that populations have moved from the south to the north using the Andean mountains as the primary corridor for dispersal.

Abstract: Insuetophrynus acarpicus is a poorly known frog restricted to the temperate forests of the coastal range of Chile (39 degrees 25' S, 73 degrees 10' W). Until recently, this species was known only from one type locality since its original description in 1970. However, in 2002 two new localities were reported, extending its distribution range to about 40 km(2). In order to evaluate genetic divergence, provide a preliminary evaluation of the genetic diversity of this species and the phylogenetic relationships among individuals from the three known populations, we analyzed the nucleotide variation of a fragment of the mitochondrial gene cytochrome b. We sampled just two or four individuals per population of this endangered frog. We found a low nucleotide divergence among populations suggesting a genetic homogeneity across the entire range. This highlights the need for further studies to define the conservation status of this endangered frog.

Abstract:

Abstract: Phylogeographic relationships were evaluated at the intraspecific level using nucleotide sequence data from the mitochondrial cytochrome b gene of representative specimens of "colilargo" (Oligoryzomys longicaudatus) from 31 localities, along its distributional range over a large part of the western Andes and southern Argentina. Based on approximately 1,000 base pairs (bp), we recognized a single species on both the Chilean and the Argentinean side as far as at least latitude 51degreesS, rejecting the subspecific distinctiveness of longicaudatus and philippi. We thus placed the latter in full synonymy with O. longicaudatus as earlier studies proposed, and enlarged its range as far as Torres del Paine, about 51degreesS. The occurrence of subspecies in this range is doubtful given the low sequence divergence values and the absence of significant associations between haplotypes and their geography. Additionally, we hypothesized that the entrance of this species into the Chilean side of the Andes mountains occurred through the Patagonian forests of southern Argentina, with further dispersal to the north from the south.

Abstract: Cases of human hantavirus disease have been reported in Chile since 1995, most of them in people living in rural and periurban areas. We conducted a peridomestic study of small mammals to evaluate the relationships between the presence of rodents with antibodies to Andes virus confirmed human cases of hantavirus pulmonary syndrome in southcentral Chile. The results of 20 sampled sites, which involved the capture of 272 mice over an 18-month period, showed the occurrence of 10 small mammal species, of which Oligoryzomys longicaudatus was the only seropositive species for hantavirus, with an intra-specific serologic rate of 10.4%

Abstract: The Eight Region has the second highest number of cases of Hantavirus Cardiopulmonary Syndrome (HCPS) in humans for Chile. A study was performed to identify the number of rodents serologically positive to hantavirus and their local distribution in this region. To achieve this goal, we sampled eleven sites in the four provinces of the region. Seven rodents species were collected, with Abrothrix olivaceus presenting the largest number of captures followed by Oligoryzomys longicaudatus. Of the 300 rodents analyzed, five (1.66%) were sero-positives to hantavirus and belonged to three different sigmodontine species: Abrothrix longipilis, O. longicaudatus, and Loxodontomys micropus. No previous records of seropositive L. micropus existed.

Abstract:

Abstract: Allozyme variation and evolutionary relationship in species of the genus Microlophus of the peruvianus group from I I localities in Chile and southern Peru were determined. Two external groups (M. occipitalis and M. thoracicus, both from northern Peru), were considered to polarize character states in a cladistics analysis. A total of 22 presumptive loci were analysed, of which 18 were variables. The results obtained suggests the presence of three species of Microlophus in southern Peru and northern Chile. Two species inhabit intertidal areas; one correspond to M. quadrivittatus which extends from Islay in Peru (16degrees59' S, 72degrees06' W) to Antofagasta in Chile (23degrees40' S, 70degrees26' W). The second species, M. atacamensis, is distribuited from the south of Antofagasta to Tres Playitas in Chile (28degrees 28' S, 71degrees14' W). The third species corresponds to M. theresioides, which is distribuited in the chilean desert, in Pica (20degrees30' S, 69degrees20' W), Huayca (20degrees11' S, 69degrees08'W), and Mamina (20degrees04' S, 69degrees13'W), and probably extends to the coastal range of the Chilean desert at this latitude. The taxonomic arrangement proposed is according to Rogers genetic identity levels, where the respective dendrogram clustered populations in three nodes, one for each species. Phylogenetic analysis confirms the existence of three clades corresponding to species suggested by phenetic analysis. We did not detect evidence of monophily of both coastal species. This indicates that M. atacamensis is the sister taxon of M. quadrivittatus - M. theresioides clade. According to this, the adaptation to an intertidal habitat could have originated more than once in the evolutionary history of Microlophus of the peruvianus group. Another explanation is that this adaptation is plesiomorphic within the group analysed.

Abstract: Genetic divergence between two traditionally recognized subspecies, Liolaemus monticola chillanensis and Liolaemus monticola ssp. was assessed by allozymic comparison. Both morphotypes are syntopic and restricted to the mountains of the Cordillera de Chillan. Results of 17 presumptive loci have shown diagnostic alleles at five loci in Esterases and MDHP enzymatic systems. This provides evidence that both morphotypes show strong differences in their genetic structure, and they are independent lineages.

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract: