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BACKGROUND AND AIMS: In eastern Neotropical South America, the Cerrado, a large savanna vegetation, and the Atlantic Forest harbour high biodiversity levels, and their habitats are rather different from each other. The biomes have intrinsic evolutionary relationships, with high lineage exchange that can be attributed, in part, to a large contact zone between them. The genomic study of ecotypes, i.e. populations adapted to divergent habitats, can be a model to study the genomic signatures of ecological divergence. Here, we investigated two ecotypes of the tree Plathymenia reticulata, one from the Cerrado and the other from the Atlantic Forest, which have a hybrid zone in the ecotonal zone of Atlantic Forest-Cerrado. METHODS: The ecotypes were sampled in the two biomes and their ecotone. The evolutionary history of the divergence of the species was analysed with double-digest restriction site-associated DNA sequencing. The genetic structure and the genotypic composition of the hybrid zone were determined. Genotype-association analyses were performed, and the loci under putative selection and their functions were investigated. KEY RESULTS: High divergence between the two ecotypes was found, and only early-generation hybrids were found in the hybrid zone, suggesting a partial reproductive barrier. Ancient introgression between the Cerrado and Atlantic Forest was not detected. The soil and climate were associated with genetic divergence in Plathymenia ecotypes and outlier loci were found to be associated with the stress response, with stomatal and root development and with reproduction. CONCLUSIONS: The high genomic, ecological and morphophysiological divergence between ecotypes, coupled with partial reproductive isolation, indicate that the ecotypes represent two species and should be managed as different evolutionary lineages. We advise that the forest species should be re-evaluated and restated as vulnerable. Our results provide insights into the genomic mechanisms underlying the diversification of species across savanna and forest habitats and the evolutionary forces acting in the species diversification in the Neotropics.

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The mechanisms of hybridization can be elucidated by analyzing genotypes as well as phenotypes that could act as premating barriers, as the reproductive interactions among heterospecifics can alter the evolutionary history of species. In frogs, hybrids typically occur among species that reproduce explosively (in dense aggregations) with few opportunities for mate selection but are rare in species with elaborate courtship behaviors that may prevent erroneous mating. Using 21 microsatellite markers, we examined hybridization in the prolonged-breeding tree frogs Bokermannohyla ibitiguara and B. sazimai sampled within a contact zone in the Brazilian savanna (72 tadpoles; 74 adults). We also compared acoustic and morphological data. We confirmed both parental species genetically; STRUCTURE results confirmed 14 hybrids, 11 of which were second-generation according to NEWHYBRIDS, all with intermediate values of genetic dissimilarities compared to the parentals. Morphological and acoustic analyses revealed that hybrids showed variable but not necessarily intermediate phenotypes. Moreover, 2 hybrids exhibited call types different from parentals. The reproduction of B. ibitiguara involves territorial and aggressive males, elaborate courtships with acoustic and tactile stimuli, choosy females, and opportunistic strategies. Our study uncovers a rare case of viable hybridization among closely related frogs with such a combination of complex courtship behaviors and mate choice. We discuss the likely directionality and mechanisms behind this phenomenon, and highlight the importance of investigating hybridization even in species that show elaborate reproduction and female choice to advance our understanding of animal diversification.

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Beekeepers around the world select bees' characteristics that facilitate and favor production. In regions where hybridization among lineages is taking place, this selection is a challenge, given that these regions are "natural laboratories", where the action of evolutionary processes of a population or species occurs in real time. A natural honeybee (Apis mellifera) hybrid zone exists in Argentina between 28° and 35° South, where Africanized (AHB) and European (EHB) populations converge. In this zone, beekeepers use selected genetic resources of European origin mostly, since the local Africanized bees show a higher defensive behavior, which is not desirable for management. Although EHB colonies have many advantages for honey production, they are not fully adapted to the subtropical climate and are susceptible to certain parasitosis such as varroosis. In addition, both AHB and EHB mate in drone congregation areas (DCAs), where males and virgin queens fly to meet, resulting in variability in the desired characteristics. In this study, we explored the degree of hybridization within a DCA and its reference apiary, located in the province of Entre Ríos, by applying two complementary techniques. First, morphotypes with different degrees of hybridization between European and African subspecies were observed in the reference apiary, indicating a high sensitivity of this morphometric approach to detect hybridization in these populations. Second, a genetic analysis revealed haplotypes of both origins for drones in DCAs, with a higher prevalence of European haplotypes, while all the colonies from the reference apiary exhibited European haplotypes. Overall, our results are in line with the strong impact that commercial beekeeping has on the genetics of DCAs. We show how wing morphometry may be used to monitor hybridization between European and African subspecies, a tool that may be evaluated in other regions of the world where hybridization occurs.

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Genetic variation segregates as linked sets of variants or haplotypes. Haplotypes and linkage are central to genetics and underpin virtually all genetic and selection analysis. Yet, genomic data often omit haplotype information due to constraints in sequencing technologies. Here, we present "haplotagging," a simple, low-cost linked-read sequencing technique that allows sequencing of hundreds of individuals while retaining linkage information. We apply haplotagging to construct megabase-size haplotypes for over 600 individual butterflies (Heliconius erato and H. melpomene), which form overlapping hybrid zones across an elevational gradient in Ecuador. Haplotagging identifies loci controlling distinctive high- and lowland wing color patterns. Divergent haplotypes are found at the same major loci in both species, while chromosome rearrangements show no parallelism. Remarkably, in both species, the geographic clines for the major wing-pattern loci are displaced by 18 km, leading to the rise of a novel hybrid morph in the center of the hybrid zone. We propose that shared warning signaling (Müllerian mimicry) may couple the cline shifts seen in both species and facilitate the parallel coemergence of a novel hybrid morph in both comimetic species. Our results show the power of efficient haplotyping methods when combined with large-scale sequencing data from natural populations.

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BACKGROUND: In the Tropical Eastern Pacific (TEP), four species of parrotfishes with complex phylogeographic histories co-occur in sympatry on rocky reefs from Baja California to Ecuador: Scarus compressus, S. ghobban, S. perrico, and S. rubroviolaceus. The most divergent, S. perrico, separated from a Central Indo-Pacific ancestor in the late Miocene (6.6 Ma). We tested the hypothesis that S. compressus was the result of ongoing hybridization among the other three species by sequencing four nuclear markers and a mitochondrial locus in samples spanning 2/3 of the latitudinal extent of the TEP. RESULTS: A Structure model indicated that K = 3 fit the nuclear data and that S. compressus individuals had admixed genomes. Our data could correctly detect and assign pure adults and F1 hybrids with > 0.90 probability, and correct assignment of F2s was also high in some cases. NewHybrids models revealed that 89.8% (n = 59) of the S. compressus samples were F1 hybrids between either S. perrico × S. ghobban or S. perrico × S. rubroviolaceus. Similarly, the most recently diverged S. ghobban and S. rubroviolaceus were hybridizing in small numbers, with half of the admixed individuals assigned to F1 hybrids and the remainder likely > F1 hybrids. We observed strong mito-nuclear discordance in all hybrid pairs. Migrate models favored gene flow between S. perrico and S. ghobban, but not other species pairs. CONCLUSIONS: Mating between divergent species is giving rise to a region-wide, multispecies hybrid complex, characterized by a high frequency of parental and F1 genotypes but a low frequency of > F1 hybrids. Trimodal structure, and evidence for fertility of both male and female F1 hybrids, suggest that fitness declines sharply in later generation hybrids. In contrast, the hybrid population of the two more recently diverged species had similar frequencies of F1 and > F1 hybrids, suggesting accelerating post-mating incompatibility with time. Mitochondrial genotypes in hybrids suggest that indiscriminate mating by male S. perrico is driving pre-zygotic breakdown, which may reflect isolation of this endemic species for millions of years resulting in weak selection for conspecific mate recognition. Despite overlapping habitat use and high rates of hybridization, species boundaries are maintained by a combination of pre- and post-mating processes in this complex.

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Natural selection is an important driver of genetic and phenotypic differentiation between species. For species in which potential gene flow is high but realized gene flow is low, adaptation via natural selection may be a particularly important force maintaining species. For a recent radiation of New World desert shrubs (Encelia: Asteraceae), we use fine-scale geographic sampling and population genomics to determine patterns of gene flow across two hybrid zones formed between two independent pairs of species with parapatric distributions. After finding evidence for extremely strong selection at both hybrid zones, we use a combination of field experiments, high-resolution imaging, and physiological measurements to determine the ecological basis for selection at one of the hybrid zones. Our results identify multiple ecological mechanisms of selection (drought, salinity, herbivory, and burial) that together are sufficient to maintain species boundaries despite high rates of hybridization. Given that multiple pairs of Encelia species hybridize at ecologically divergent parapatric boundaries, such mechanisms may maintain species boundaries throughout Encelia.

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BACKGROUND: Invasion of organisms into new ecosystems is increasingly common, due to the global trade in commodities. One of the most complex post-invasion scenarios occurs when an invasive species is related to a native pest, and even more so when they can hybridize and produce fertile progeny. The global pest Helicoverpa armigera was first detected in Brazil in 2013 and generated a wave of speculations about the possibility of hybridization with the native sister taxon Helicoverpa zea. In the present study, we used genome-wide single nucleotide polymorphisms from field-collected individuals to estimate hybridization between H. armigera and H. zea in different Brazilian agricultural landscapes. RESULTS: The frequency of hybridization varied from 15 to 30% depending on the statistical analyses. These methods showed more congruence in estimating that hybrids contained approximately 10% mixed ancestry (i.e. introgression) from either species. Hybridization also varied considerably depending on the geographic locations where the sample was collected, forming a 'mosaic' hybrid zone where introgression may be facilitated by environmental and landscape variables. Both landscape composition and bioclimatic variables indicated that maize and soybean cropland are the main factors responsible for high levels of introgression in agricultural landscapes. The impact of multiple H. armigera incursions is reflected in the structured and inbred pattern of genetic diversity. CONCLUSIONS: Our data showed that the landscape composition and bioclimatic variables influence the introgression rate between H. armigera and H. zea in agricultural areas. Continuous monitoring of the hybridization process in the field is necessary, since agricultural expansion, climatic fluctuations, changing composition of crop species and varieties, and dynamic planting seasons are some factors in South America that could cause a sudden alteration in the introgression rate between Helicoverpa species. Introgression between invasive and native pests can dramatically impact the evolution of host ranges and resistance management.

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The genus Austrolebias (Cyprinodontiformes: Rivulidae) represents a specious group of taxa following annual life cycles in the neotropical ichthyofauna. They live in temporary ponds and each generation must be completed in a few months, depending on environmental stochasticity. Annual fish survive the dry season through diapausing eggs buried in the substrate of these ponds. A hypothesized bimodal hybrid zone between two taxa of the genus, A. charrua and A. reicherti from Dos Patos Merin lagoon system, was recently proposed based on genetics and morphological analyses. However, hundreds of additional nuclear molecular markers should be used to strongly support this hypothesized bimodal pattern. In the present paper, we conducted RNA-seq-based sequencing of the transcriptomes from pools of individuals of A. charrua, A. reicherti and their putative natural hybrids from the previously characterized hybrid zone. As a result, we identified a set of 111,725 SNP (single nucleotide polymorphism) markers, representing presumably fixed allelic differences among the two species. The present study provided the first panel of 106 SNP markers as a single diagnostic multiplex assay and validated their capacity to reconstruct the patterns of the hybrid zone between both taxa. These nuclear markers combined with Cytb gene and morphological analyses detected a population structure in which some groups among the hybrid swarms showed different level of introgression towards one or the other parental species according to their geographic distribution. High-quality transcriptomes and a large set of gene-linked SNPs should greatly facilitate functional and population genomics studies in the hybrid zone of these endangered species.

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Hybrid zones have long been of interest to biologists as natural laboratories where we can gain insight into the processes of adaptation and speciation. Repeated sampling of individual hybrid zones has been particularly useful in elucidating the dynamic balance between selection and dispersal that maintains most hybrid zones. Here, we revisit a hybrid zone between Heliconius erato butterflies in Panamá for a third time over more than 30 years. We combine a novel Bayesian extension of stepped-cline hybrid zone models with environmental data to understand the genetic and environmental causes of cline dynamics in this species. The cline has continued to move west, likely due to dominance drive, but has slowed and broadened. Environmental analyses suggest that widespread deforestation in Panamá could be leading to decreased avian predation and relaxed selection, causing the observed changes in cline dynamics.

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Determining the mechanisms that create and maintain biodiversity is a central question in ecology and evolution. Speciation is the process that creates biodiversity. Speciation is mediated by incompatibilities that lead to reproductive isolation between divergent populations and these incompatibilities can be observed in hybrid zones. Gecko lizards are a speciose clade possessing an impressive diversity of behavioral and morphological traits. In geckos, however, our understanding of the speciation process is negligible. To address this gap, we used genetic sequence data (both mitochondrial and nuclear markers) to revisit a putative hybrid zone between Sphaerodactylus nicholsi and Sphaerodactylus townsendi in Puerto Rico, initially described in 1984. First, we addressed discrepancies in the literature on the validity of both species. Second, we sampled a 10-km-wide transect across the putative hybrid zone and tested explicit predictions about its dynamics using cline models. Third, we investigated potential causes for the hybrid zone using species distribution modeling and simulations; namely, whether unique climatic variables within the hybrid zone might elicit selection for intermediate phenotypes. We find strong support for the species-level status of each species and no evidence of movement, or unique climatic variables near the hybrid zone. We suggest that this narrow hybrid zone is geographically stable and is maintained by a combination of dispersal and selection. Thus, this work has identified an extant model system within geckos that that can be used for future investigations detailing genetic mechanisms of reproductive isolation in an understudied vertebrate group.

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The validity of the monobasic neotropical butterfly genus Cheimas Thieme (Nymphalidae, Satyrinae, Satyrini, Pronophilina) is discussed, and confirmed based on morphological and molecular data. Cheimas opalinus (Staudinger), endemic to the Venezuelan Cordillera de Mérida, and considered prior to this study to be monotypic and restricted to the central part of the range, is demonstrated to be polytypic and more widely distributed. Five subspecies are recognised, differing mostly in their dorsal patterns, in particular the shape and colour of hindwing greenish-blue patch. Mitochondrial DNA sequences (COI) were obtained for three of them. The nominate subspecies is found in the central part of the range, in the Sierra Nevada and La Culata. The other subspecies are found as follows: C. opalinus dominici n. ssp.; in the Santo Domingo valley in the centre-north; C. opalinus cristalinus n. ssp. in the north; C. opalinus iosephi n. ssp. on the eastern slopes, and C. opalinus rosalinus n. ssp. in the southern Páramo El Batallón massif. A hybrid zone between the latter two subspecies was detected in the northern part of the Batallón massif based on unusual individual variation and intermediate phenotypes. All the populations of Cheimas opalinus occur in the forest-paramo ecotone at 2800-3400 m a.s.l., with the notable exception of C. opalinus cristalinus n. ssp. found also in mid-elevation forests down to 2300 m a.s.l.

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Mangrove plants comprise plants with similar ecological features that have enabled them to adapt to life between the sea and the land. Within a geographic region, different mangrove species share not only similar adaptations but also similar genetic structure patterns. Along the eastern coast of South America, there is a subdivision between the populations north and south of the continent's northeastern extremity. Here, we aimed to test for this north-south genetic structure in Rhizophora mangle, a dominant mangrove plant in the Western Hemisphere. Additionally, we aimed to study the relationships between R. mangle, R. racemosa, and R. × harrisonii and to test for evidence of hybridization and introgression. Our results confirmed the north-south genetic structure pattern in R. mangle and revealed a less abrupt genetic break in the northern population than those observed in Avicennia species, another dominant and widespread mangrove genus in the Western Hemisphere. These results are consistent with the role of oceanic currents influencing sea-dispersed plants and differences between Avicennia and Rhizophora propagules in longevity and establishment time. We also observed that introgression and hybridization are relevant biological processes in the northeastern coast of South America and that they are likely asymmetric toward R. mangle, suggesting that adaptation might be a process maintaining this hybrid zone.

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OBJECTIVES: When closely related species overlap geographically, selection may favor species-specific mate recognition traits to avoid hybridization costs. Conversely, the need to recognize potential same-sex rivals may select for lower specificity, creating the possibility that selection in one domain constrains evolution in the other. Despite a wealth of data on mate recognition, studies addressing rival recognition between hybridizing species are limited to a few bird species. Using naïve populations, we examine the extent to which failed rival recognition might have affected hybridization patterns when two species of howler monkeys (Alouatta pigra and A. palliata) first met after diverging in allopatry. METHODS: We simulated first contact between naïve subjects using playback experiments in allopatric populations of the two purebred species. Using linear mixed models, we compared their look, move, and vocal responses to conspecific and heterospecific loud calls. RESULTS: Although not different in overall response strength to playbacks, the two species differed in reaction to heterospecific callers. Male A. pigra ignored calls from male A. palliata, but the reverse was not true. DISCUSSION: Despite striking differences in vocalizations, A. palliata respond equally to calls from both species whereas A. pigra respond only to conspecifics. This apparent failure of A. pigra males to recognize interspecific rivals might have biased hybridization (F1 hybrids = male A. palliata x female A. pigra), a pattern previously hypothesized based on genetic analysis of hybrids. Given that A. pigra males could be losing reproductive opportunities to heterospecific males, our findings add to growing evidence of potential costs for overly specific species recognition.

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BACKGROUND: Characterizations of the dynamics of hybrid zones in space and time can give insights about traits and processes important in population divergence and speciation. We characterized a hybrid zone between tanagers in the genus Ramphocelus (Aves, Thraupidae) located in southwestern Colombia. We evaluated whether this hybrid zone originated as a result of secondary contact or of primary differentiation, and described its dynamics across time using spatial analyses of molecular, morphological, and coloration data in combination with paleodistribution modeling. RESULTS: Models of potential historical distributions based on climatic data and genetic signatures of demographic expansion suggested that the hybrid zone likely originated following secondary contact between populations that expanded their ranges out of isolated areas in the Quaternary. Concordant patterns of variation in phenotypic characters across the hybrid zone and its narrow extent are suggestive of a tension zone, maintained by a balance between dispersal and selection against hybrids. Estimates of phenotypic cline parameters obtained using specimens collected over nearly a century revealed that, in recent decades, the zone appears to have moved to the east and to higher elevations, and may have become narrower. Genetic variation was not clearly structured along the hybrid zone, but comparisons between historical and contemporary specimens suggested that temporal changes in its genetic makeup may also have occurred. CONCLUSIONS: Our data suggest that the hybrid zone likey resulted from secondary contact between populations. The observed changes in the hybrid zone may be a result of sexual selection, asymmetric gene flow, or environmental change.

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The genus Crocodylus comprises 12 currently recognized species, many of which can be difficult to differentiate phenotypically. Interspecific hybridization among crocodiles is known to occur in captivity and has been documented between some species in the wild. The identification of hybrid individuals is of importance for management and monitoring of crocodilians, many of which are Convention on International Trade in Endangered Species (CITES) listed. In this study, both mitochondrial and nuclear DNA markers were evaluated for their use in confirming a suspected hybrid zone between American crocodile (Crocodylus acutus) and Morelet's crocodile (Crocodylus moreletii) populations in southern Belize where individuals and nests exhibiting atypical phenotypic features had previously been observed. Patterns observed in both phenotypic and molecular data indicate possible behavioural and ecological characteristics associated with hybridization events. The results of the combined analyses found that the majority of suspected hybrid samples represent crosses between female C. acutus and male C. moreletii. Phenotypic data could statistically identify hybrids, although morphological overlap between hybrids and C. moreletii reduced reliability of identification based solely on field characters. Ecologically, C. acutus was exclusively found in saline waters, whereas hybrids and C. moreletii were largely absent in these conditions. A hypothesized correlation between unidirectional hybridization and destruction of C. acutus breeding habitats warrants additional research.

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The Psorophora confinnis complex is currently composed of three species--Psorophora confinnis sensu stricto (Lynch Arribalzaga) in South America, Psorophora columbiae (Dyar and Knab) in North America, and Psorophora jamaicensis (Theobald) in the Caribbean. Members of the complex are of considerable importance as vectors of arboviruses, for example, Venezuelan equine encephalitis virus, and are significant biting pests throughout their range. The biological and geographic boundaries of Ps. confinnis and Ps. columbiae are unclear. In fact, the name Ps. columbiae is presently designated as "provisional." In this article, we aim to clarify the taxonomy and geographic distributions of species within the Ps. confinnis complex. A population genetics approach was employed using gene and genotypic frequency data at 26 isozyme loci. The results suggest that the Ps. confinnis complex in North and South America is composed of four species. Ps. confinnis s.s. and Ps. columbiae are distinct species in South and North America, respectively. Populations in Colombia, South America, formally designated as Ps. funiculus (Dyar) and populations in the southwestern United States and western Mexico, formally designated Ps. toltecum (Dyar and Knab), are distinct species. Psorophora toltecum and Psorophora funiculus species names should be resurrected from synonymy. In addition we identified a Ps. columbiae and Ps. toltecum hybrid zone in central Texas in a region described as being one of 13 North American suture zones, being geographical areas in which closely related species occur in sympatry and frequently hybridize.

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Many understory birds and other groups form genetically differentiated subspecies or closely related species on opposite sides of major rivers of Amazonia, but are proposed to come into geographic contact in headwater regions where narrower river widths may present less of a dispersal barrier. Whether such forms hybridize in headwater regions is generally unknown, but has important implications to our understanding of the role of rivers as drivers of speciation. We used a dataset of several thousand single nucleotide polymorphisms to show that seven taxon pairs that differentiate across a major Amazonian river come into geographic contact and hybridize in headwater regions. All taxon pairs possessed hybrids with low numbers of loci in which alleles were inherited from both parental species, suggesting they are backcrossed with parentals, and indicating gene flow between parental populations. Ongoing gene flow challenges rivers as the sole cause of in situ speciation, but is compatible with the view that the wide river courses in the heart of Amazonia may have driven interfluvial divergence during episodes of wet forest retraction away from headwater regions. Taxa as old as 4 Ma in our Amazonian dataset continue to hybridize at contact zones, suggesting reproductive isolation evolves at a slow pace.

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Just as mating patterns can promote speciation or hybridization, the presence of hybridization can shape mating patterns within a population. In this study, we characterized patterns of multiple mating and reproductive skew in a naturally hybridizing swordtail fish species, Xiphophorus birchmanni. We quantified multiple mating using microsatellite markers to genotype embryos from 43 females collected from 2 wild populations. We also used a suite of single-nucleotide polymorphism markers to categorize females and their inferred mates as either parental X. birchmanni or as introgressed individuals, which carried alleles from a sister species, X. malinche. We found that parental and introgressed X. birchmanni females mated multiply with both parental and introgressed males. We found no difference in mating patterns or reproductive skew between parental and introgressed X. birchmanni females. However, nonintrogressed X. birchmanni males mated more often with large, fecund females. These females also had the greatest levels of skew in fertilization success of males. Thus, our results show that X. birchmanni has a polygynandrous mating system and that introgression of X. malinche alleles has only subtle effects on mating patterns in this species.

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Chagas disease, one of the most important vector-borne diseases in the Americas, is caused by Trypanosoma cruzi and transmitted to humans by insects of the subfamily Triatominae. An effective control of this disease depends on elimination of vectors through spraying with insecticides. Genetic research can help insect control programs by identifying and characterizing vector populations. In southern Latin America, Triatoma infestans is the main vector and presents two distinct lineages, known as Andean and non-Andean chromosomal groups, that are highly differentiated by the amount of heterochromatin and genome size. Analyses with nuclear and mitochondrial sequences are not conclusive about resolving the origin and spread of T. infestans. The present paper includes the analyses of karyotypes, heterochromatin distribution and chromosomal mapping of the major ribosomal cluster (45S rDNA) to specimens throughout the distribution range of this species, including pyrethroid-resistant populations. A total of 417 specimens from seven different countries were analyzed. We show an unusual wide rDNA variability related to number and chromosomal position of the ribosomal genes, never before reported in species with holocentric chromosomes. Considering the chromosomal groups previously described, the ribosomal patterns are associated with a particular geographic distribution. Our results reveal that the differentiation process between both T. infestans chromosomal groups has involved significant genomic reorganization of essential coding sequences, besides the changes in heterochromatin and genomic size previously reported. The chromosomal markers also allowed us to detect the existence of a hybrid zone occupied by individuals derived from crosses between both chromosomal groups. Our genetic studies support the hypothesis of an Andean origin for T. infestans, and suggest that pyrethroid-resistant populations from the Argentinean-Bolivian border are most likely the result of recent secondary contact between both lineages. We suggest that vector control programs should make a greater effort in the entomological surveillance of those regions with both chromosomal groups to avoid rapid emergence of resistant individuals.

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Eight current species of snakes of the Bothrops neuwiedi group are widespread in South American open biomes from northeastern Brazil to southeastern Argentina. In this paper, 140 samples from 93 different localities were used to investigate species boundaries and to provide a hypothesis of phylogenetic relationships among the members of this group based on 1122bp of cyt b and ND4 from mitochondrial DNA and also investigate the patterns and processes occurring in the evolutionary history of the group. Combined data recovered the B. neuwiedi group as a highly supported monophyletic group in maximum parsimony, maximum likelihood and Bayesian analyses, as well as four major clades (Northeast I, Northeast II, East-West, West-South) highly-structured geographically. Monophyly was recovered only for B. pubescens. By contrast, B. diporus, B. lutzi, B. erythromelas, B. mattogrossensis, B. neuwiedi, B. marmoratus, and B. pauloensis, as currently defined on the basis of morphology, were polyphyletic. Sympatry, phenotypic intergrades and shared mtDNA haplotypes, mainly between B. marmoratus and B. pauloensis suggest recent introgressive hybridization and the possible occurrence of a narrow hybrid zone in Central Brazil. Our data suggest at least three candidate species: B. neuwiedi from Espinhaço Range, B. mattogrossensis (TM173) from Serra da Borda (MT) and B. diporus (PT3404) from Castro Barros, Argentina. Divergence estimates highlight the importance of Neogene events in the origin of B. neuwiedi group, and the origin of species and diversification of populations of the Neotropical fauna from open biomes during the Quaternary climate fluctuations. Data reported here represent a remarkable increase of the B. neuwiedi group sampling size, since representatives of all the current recognized species from a wide geographic range are included in this study, providing basic information for understanding the evolution and conservation of Neotropical biodiversity.

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