Triatominae in furnariid nests of the Argentine Gran Chaco

Triatomines (Hemiptera, Reduviidae) are bloodsucking insects involved in the transmission of Trypanosoma cruzi, the causative agent of Chagas disease, an important public health problem in Latin America. The triatomine species found in sylvatic habitats generally play a limited epidemiological role compared to domestic species, but they may act as a reinfestation source of dwellings after insecticide spraying and have to be carefully considered in control strategies of Chagas disease transmission. The objectives of this work were to carry out a survey of the sylvatic triatomine species colonizing Furnariidae nests in a typical area of the Chaco region of Argentina during the winter and to study the parasites and natural enemies associated with the collected triatomines. Sixty‐three triatomine specimens were collected from Furnariidae nests (Coryphistera alaudina and Phacellodomus sibilatrix) randomly selected within the study area. Fifty‐four were identified as Psammolestes coreodes, seven as Triatoma platensis, and two as Triatoma infestans. Specimens of T. infestans and T. platensis were found in one nest. The first finding of instar nymphs of T. infestans x T. platensis in a sylvatic habitat is reported. For the first time, sylvatic collected specimens of T. platensis were found infected by T. cruzi. Triatoma virus was found in one Ps. coreodes specimen.     

Trichopterans in a River of the Gran Chaco,Argentina

Twenty two species of Trichoptera were collected at 21 sampling stations in the Suquía river basin. Known ranges of 12 were enlarged by more than 300 km and constitute new records for a semiarid region. The different environmental conditions where their larvae live are listed.     

Genetic structure and gene flow in Gran Chaco populations of Argentina: evidence from Y-chromosome markers

The Gran Chaco region of central South America has been settled by humans for only the last 4,000-5,000 years. To investigate population structure and variation in this region's indigenous population, we scored males from tribes of the Argentinean part of the Gran Chaco (Pilagá, Wichí, and Toba, representing two major language groups, the Mataco and Guaycurú) for a number of Y-chromosome polymorphisms. The markers included eight microsatellites (DYS19, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438, and DYS439) and the unique native American single nucleotide polymorphism, DYS199. Sixty males (77%) from the total sample carried the DYS199T chromosome, and these were the focus of the present analysis. Unlike most other native Americans, Gran Chaco males show a moderate level of diversity at the DYS19 locus but still less than that seen in non-native Americans. The FST value for Y-chromosome markers in Gran Chaco was 0.107, a value that is more than double that found for mtDNA haplogroups in the same tribes but is not particularly high compared with other Y-chromosome studies. Phylogenetic trees based on all eight microsatellites showed relatively poor correlation of the tribes with either geography or language, and this is possibly explained by their ecology. They are seasonal hunters living in small bands, and under such circumstances drift will be a powerful evolutionary force. An UPGMA tree based on five microsatellites (DYS19, DYS390, DYS391, DYS392, and DYS393), however, showed a more positive relationship, suggesting that DYS437, DYS438, and DYS439 may behave differently from the other microsatellites. No association was found between maternal and paternal lineage distributions. The time to the most recent common ancestor of the DYS199T chromosome is calculated to lie between 13,000 and 26,000 years. This range is consistent with estimates from other Y-chromosome studies as well as with estimates from mtDNA and the archeology of the colonization of South America. We conclude that the male lineages present in the contemporary Gran Chaco population reflect the level of diversity found in South America and that the region's male founders did not carry a restricted gene pool.     

Mitochondrial DNA haplogroups in Amerindian populations from the Gran Chaco.

Mitochondrial DNA from 141 individuals was typed for diagnostic restriction sites and the 9-bp region V deletion to examine the distribution of the founding mtDNA lineage haplotypes in three Amerindian populations (Mataco, Toba, and Pilagá) who currently inhabit the Argentinian part of the Gran Chaco. All four lineages were identified in the three tribes and four population samples studied. Disregarding ethnic or geographic origin, haplogroups B and D exhibit high incidence among the Gran Chaco inhabitants, whereas haplogroups A and C are present in a lower frequency. Three individuals possess none of the characteristic markers and, therefore, could not be assigned to one of those lineages. A neighbor-joining representation of F(ST) distances reflects the current geographic location of the populations, and this also corresponds to their historic distribution. After separating South America into four major regions (Tropical Forest, Andes, Gran Chaco, and Patagonia-Tierra del Fuego), the Gran Chaco populations present the highest average intragroup variability (Hs = 0.64) as well as the lowest intergroup diversity (G(')(ST) = 0.06). These findings suggest high levels of gene flow among the Chaco tribes, as well as with neighbor populations from outside the region.     

Sarcoptic mange in free-ranging pampas foxes in the Gran Chaco,Bolivia

Sarcoptes scabiei infestation was diagnosed in two freshly dead free-ranging pampas foxes (Pseudalopex gymnocercus) in the Gran Chaco, Bolivia. Diagnosis was made based on histologic evaluation of skin biopsies and identification of the parasite from skin scrapings. Characteristic gross lesions consistent with mange were noted in 19 of 94 observations of free-ranging pampas foxes in the region from December 1998 to January 2000. None of 16 crab-eating foxes (Cerdocyon thous) observed during the same time period had visible lesions consistent with scabies. These are the first case reports of S. scabiei in pampas foxes.     

Increasing synergistic effects of habitat destruction and hunting on mammals over three decades in the Gran Chaco

Habitat destruction and overexploitation are the main threats to biodiversity and where they co-occur, their combined impact is often larger than their individual one. Yet, detailed knowledge of the spatial footprints of these threats is lacking, including where they overlap and how they change over time. These knowledge gaps are real barriers for effective conservation planning. Here, we develop a novel approach to reconstruct the individual and combined footprints of both threats over time. We combine satellite-based land-cover change maps, habitat suitability models and hunting pressure models to demonstrate our approach for the community of larger mammals (48 species > 1 kg) across the 1.1 million km² Gran Chaco region, a global deforestation hotspot covering parts of Argentina, Bolivia and Paraguay. This provides three key insights. First, we find that the footprints of habitat destruction and hunting pressure expanded considerably between 1985 and 2015, across ~40% of the entire Chaco – twice the area affected by deforestation. Second, both threats increasingly acted together within the ranges of larger mammals in the Chaco (17% increase on average, ± 20% SD, cumulative increase of co-occurring threats across 465 000 km²), suggesting large synergistic effects. Conversely, core areas of high-quality habitats declined on average by 38%. Third, we identified remaining priority areas for conservation in the northern and central Chaco, many of which are outside the protected area network. We also identify hotspots of high threat impacts in central Paraguay and northern Argentina, providing a spatial template for threat-specific conservation action. Overall, our findings suggest increasing synergistic effects between habitat destruction and hunting pressure in the Chaco, a situation likely common in many tropical deforestation frontiers. Our work highlights how threats can be traced in space and time to understand their individual and combined impact, even in situations where data are sparse.     

Deforestation and cattle ranching drive rapid range expansion of capybara in the Gran Chaco ecosystem

Anthropogenic habitat alteration has the capacity to alter the distribution of species. Capybara (Hydrochoerus hydrochaeris) are a widely distributed rodent throughout most of South America, but are restricted to areas of standing water. As the Gran Chaco ecosystem of Paraguay is converted from dry tropical forest to pastureland, we hypothesize that this alteration creates potential for invasion by capybara into newly fragmented areas. We surveyed throughout the Chaco to estimate the distribution of capybara, and we collected noninvasive genetic samples. We used ecological niche modeling based on six environmental or climatic variables, and we modeled both the current distribution of capybara and the distribution of capybara 80 years ago. We then verified the hypothesized demographic signal generated with our model using phylogeographic analyses of 386 bp of the mtDNA control region. Comparison of present and past models suggested that populations expanded into the Gran Chaco after forest was converted to pastureland. Analyses of the mitochondrial D‐loop supported the rapid range expansion scenario. We also found evidence of secondary contact of two distinct phylogroups which had previously been disjunct. Anthropogenic land transformation appeared to be a major factor influencing the distribution, as predicted by the niche model and confirmed by genetic data. Habitat modification altered connectivity of populations across the landscape. In addition, long separated clades of capybara are now admixed throughout the Paraguayan Chaco. The invasion of a large bodied herbivore into the High Chaco region may exacerbate the degradation of forest and prevent forest regeneration. As the reservoir host of several zoonotic diseases, the expansion and contact of two previously disjunct capybara populations has implications for disease emergence.     

Disease survey of free-ranging grey brocket deer (Mazama gouazoubira) in the Gran Chaco, Bolivia

Samples from 17 free-ranging hunter-killed grey brocket deer (Mazama gouazoubira) in the Gran Chaco, Bolivia, were collected during June-August 1999. All 17 deer appeared to be in good condition at the time of death. Gross necropsies were performed, serum was collected for serologic evaluation of selected infectious disease agents, and feces and ectoparasites were collected for evaluation of internal and external parasites. Serologic tests were positive for antibodies against bovine respiratory syncytial virus and four Leptospira interrogans serovars, with questionable results for epizootic hemorrhagic disease virus serotypes 1 and 2. No antibodies were detected to Anaplasma marginale, Babesia bigemina, Babesia bovis, Babesia odocoilei, bluetongue virus (serotypes 2, 10, 11, 13, and 17), bovine viral diarrhea virus, Brucella abortus, foot-and-mouth disease virus, infectious bovine rhinotracheitis virus, Mycobacterium avium subsp. paratuberculosis, and parainfluenza-3 virus. Sixty-four percent (7/11) of the deer had endoparasites. Amblyomma spp. ticks were found on seven deer, flies of the family Hippoboscidae on six deer, and lice on six deer.     

Exploring the association between Trypanosoma cruzi infection in rural communities and environmental changes in the southern Gran Chaco

The association between land use and land cover changes between 1979-2004 in a 2.26-million-hectare area south of the Gran Chaco region and Trypanosoma cruzi infection in rural communities was analysed. The extent of cultural land, open and closed forests and shrubland up to 3,000 m around rural communities in the north, northwest and west of the province of Córdoba was estimated using Landsat satellite imagery. The T. cruzi prevalence was estimated with a cross-sectional serological survey conducted in the rural communities. The land cover showed the same patterns in the 1979, 1999 and 2004 satellite imagery in both the northwest and west regions, with shrinking regions of cultured land and expanding closed forests away from the community. The closed forests and agricultural land coverage in the north region showed the same trend as in the northwest and west regions in 1979 but not in 1999 or 2004. In the latter two years, the coverage remote from the communities was either constant or changed in opposite ways from that of the northwest and west regions. The changes in closed forests and cultured vegetation alone did not have a significant, direct relationship with the occurrence of rural communities with at least one person infected by T. cruzi. This study suggests that the overall decrease in the prevalence of T. cruzi is a consequence of a combined effect of vector control activities and changes in land use and land cover.     

Wordhood and the interplay of linguistic levels in synthetic languages. An empirical study on Wichi (Mataguayan,Gran Chaco)

On the basis of data from the synthetic and agglutinative South American language Wichi (Mataguayan, Argentina/Bolivia), I argue in favor of regarding interface phenomena as typological variables. In particular, in this paper I discuss what type of interactions these are, arguing that they do not affect wordhood but do contribute to its formation. I will defend the hypothesis that linguistic level interactions within the word are of two types and different in nature: overlapping on the one hand and conditioning and alteration on the other. Conditioning only takes place in morphophonological and morphosemantic interactions and it follows the wordhood requirements of the language. Conversely, the interaction of morphology with all linguistic levels shows overlapping of units: the phonological word and the grammatical word in the morphophonological relation; the word and the simple clause or nominal phrase in the morphosyntactic relation; and the word and the semantic unit in the morphosemantic relation. This explains why the word is generally defined by phonological, morphological, syntactic and semantic criteria. It is to be hoped that the conclusions arrived at in this paper would contribute to deepen our knowledge of the notion of wordhood in synthetic languages in South America as well as our understanding of language structure and functioning.     

Geographic variation in scalation of the lizard Gallotia stehlini within the island of Gran Canaria

The lacertid lizard ( Gallotia stehlini ), an endemic of Gran Canaria, shows no visually obvious geographic variation, yet all seven scalation characters that were examined exhibit significant geographic variation. The number of collar scales, scales along the ventral trunk and femoral pores are correlated with habitat type, while the number of femoral pores is correlated negatively with altitude. Mantel tests were used to compare simultaneously an observed pattern with three hypothesized patterns (habitat type, altitude and proximity). They indicate that, while several individual characters are significantly associated with the putative causal factors of habitat type and altitude, there is no association between an overall scalation distance matrix and habitat type, or altitude when the effect of proximity is removed. Consequently, one should consider the individual characters as well as the multivariate generalized distances. Some of the observed patterns of geographic variation in scalation are very similar to those of the small scincid lizard Chalcides sexlineatus on Gran Canaria and also parallel the altitudinal and latitudinal variation in the scalation of the Tenerife lacertid ( Galotia galloti ). The low level of congruence in patterns of geographic variation in individual characters (i.e. some vary with latitude, some with altitude and one varies with longitude) is consistent with the hypothesis that ecogenetically caused geographic variation may result in lower inter-character congruence than phylogenetically caused geographic variation.     

The influence of habitat structure on arthropod diversity in Argentine semi-arid Chaco forest

Abstract. The Argentine Chaco is a mosaic of grassland and open forest habitats maintained by natural disturbance activities such as fire. Since the introduction of domestic livestock and other human activities, the balance of this mosaic has been significantly altered, both in plant species and structural composition. This study focuses on the impact of such changes on the diversity of ground-dwelling arthropods within semi-arid Chaco forest. Quantitative measures of habitat structure and arthropod diversity were taken in forest areas previously subjected to grazing, logging and ploughing. Results indicated that arthropod diversity was smaller on sites with reduced structural complexity, with marked changes in arthropod family composition. The habitat components relating to plant architectural and vertical diversity were particularly influential on arthropod diversity. The guild size ratio of predatory to non-predatory arthropods also differed significantly between habitats suggesting a change in the resource base available to some groups. The latter suggests a shift in the functional organisation of the forest ecosystem which could have important repercussions for the diversity of other trophic levels.     

L925I Mutation in the Para-Type Sodium Channel Is Associated with Pyrethroid Resistance in Triatoma infestans from the Gran Chaco Region

Background

Chagas'' disease is an important public health concern in Latin America. Despite intensive vector control efforts using pyrethroid insecticides, the elimination of Triatoma infestans has failed in the Gran Chaco, an ecoregion that extends over Argentina, Paraguay, Bolivia and Brazil.The voltage-gated sodium channel is the target site of pyrethroid insecticides. Point mutations in domain II region of the channel have been implicated in pyrethroid resistance of several insect species.

Methods and Findings

In the present paper, we identify L925I, a new pyrethroid resistance-conferring mutation in T. infestans. This mutation has been found only in hemipterans. In T. infestans, L925I mutation occurs in a resistant population from the Gran Chaco region and is associated with inefficiency in the control campaigns. We also describe a method to detect L925I mutation in individuals from the field.

Conclusions and Significance

The findings have important implications in the implementation of strategies for resistance management and in the rational design of campaigns for the control of Chagas'' disease transmission.     

New structures for goat corrals to control peridomestic populations of Triatoma infestans (Hemiptera: Reduviidae) in the Gran Chaco of Argentina

Goat production is an important economic activity for rural communities in the Gran Chaco of Argentina. Goat corrals are important for the survival of peridomestic populations of Triatoma infestans. This study evaluated the impact of modifying the traditional structure of goat corrals on T. infestans populations and goat productivity in the region of Los Llanos (La Rioja). Thirty-nine experimental corrals were constructed and 57 traditional corrals were used as controls. We evaluated the infestations of the control and experimental corrals for five years following construction of the structures. The results showed that the new structures did not prevent the colonization, although it enhanced the detection of infestation at low densities of T. infestans. No significant difference was found in T. infestans population abundance between control and experimental corrals, probably because of the different detectability in the two types of structures, especially among the small nymphs. Although goat productivity average was higher in experimental than in control corrals, no significant difference was found because of high variability. The new structures can be used as a complement to promote the development of rural communities. Acceptability and adoption of the new corrals by the owners was high, as the enclosures offered better protection for the goats, increased growth of kids and facilitated herd handling.     

Temporal Changes in Forest Contexts at Multiple Extents: Three Decades of Fragmentation in the Gran Chaco (1979-2010), Central Argentina

The context in which a forest exists strongly influences its function and sustainability. Unveiling the multi-scale nature of forest fragmentation context is crucial to understand how human activities affect the spatial patterns of forests across a range of scales. However, this issue remains almost unexplored in subtropical ecosystems. In this study, we analyzed temporal changes (1979–2010) in forest contexts in the Argentinean dry Chaco at multiple extents. We classified forests over the last three decades based on forest context amount (P _f) and structural connectivity (P _ff), which were measured using a moving window approach fixed at eight different extents (from local, ~ 6 ha, to regional, ~ 8300 ha). Specific multi-scale forest context profiles (for the years 1979 and 2010) were defined by projecting P _f vs. P _ff mean values and were compared across spatial extents. The distributions of P _f across scales were described by scalograms and their shapes over time were compared. The amount of agricultural land and rangelands across the scales were also analyzed. The dry Chaco has undergone an intensive process of fragmentation, resulting in a shift from landscapes dominated by forests with gaps of rangelands to landscapes where small forest patches are embedded in agricultural lands. Multi-scale fragmentation analysis depicted landscapes in which local exploitation, which perforates forest cover, occurs alongside extensive forest clearings, reducing forests to small and isolated patches surrounded by agricultural lands. In addition, the temporal diminution of P _f’s variability along with the increment of the mean slope of the P _f ‘s scalograms, indicate a simplification of the spatial pattern of forest over time. The observed changes have most likely been the result of the interplay between human activities and environmental constraints, which have shaped the spatial patterns of forests across scales. Based on our results, strategies for the conservation and sustainable management of the dry Chaco should take into account both the context of each habitat location and the scales over which a forest pattern might be preserved, altered or restored.     

Hematopoietic chimerism monitoring based on STRs: quantitative platform performance on sequential samples.

Hematopoietic stem cell transplantation (HSCT) creates a donor-recipient cellular chimerism in the patient, which is quantitatively assayed from peripheral blood based on STR-DNA. Since chimerism values often vary across a patient's samples, it is important to determine to what extent this variability reflects technical aspects of platform performance. This issue is systematically assessed in the current study for the first time. Using the SGM Plus multiplex PCR kit and ABI platform, the longitudinal performance of STR markers was quantitatively evaluated in two chimeric models with true values, and in patient samples (n >500 marker loci). Computation of percent chimerism for each marker, and mean (sample) percent chimerism, standard deviation, and coefficient of variance was performed by our ChimerTrack utility. In chimeric models with known values, individual markers exhibited an accuracy (observed/true) of 88-98%; replication precision was 92-100% true, with a mean error of 2%. Fragment size calling was greater than 99% accurate and precise. Patient results were comparable for markers, relaive to sample means. One source of technical variability in chimerism estimation was allelic differential amplification efficiency. The latter was influenced by signal amplitude, dye label, marker size, and allelic size interval. It can be concluded that long-term chimeric tracking is routinely feasible using this platform in conjunction with ChimerTrack software. Importantly, mean percent chimerism, for any sample, should closely approximate the true chimeric status, with a technical accuracy of 98%. Guidelines are presented for selecting an optimized marker profile.