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K. BITENCOURTH C. M. VOLOCH N. M. SERRA‐FREIRE E. MACHADO‐FERREIRA M. AMORIM G. S. GAZÊTA 《Medical and veterinary entomology》2016,30(3):342-350
Amblyomma sculptum (Ixodida: Ixodidae) Berlese, 1888, a member of the Amblyomma cajennense complex, is the major vector of Brazilian spotted fever (BSF) in southeastern Brazil. In this study, the genetic diversity of A. sculptum populations in the state of Rio de Janeiro (RJ), Brazil, was investigated because genetic variability in tick populations may be related to vector competence. Samples of A. sculptum from 19 municipalities in 7 regions of RJ were subjected to DNA extraction, amplification and sequencing of D‐loop, cytochrome oxidase II and 12S rDNA mitochondrial genes. These sequences were used to map the genetic diversity of this tick. Amblyomma sculptum populations are genetically diverse in RJ, especially in the South Centre and Highland regions. Few unique haplotypes were observed in all populations, and the majority of genetic variation found was among ticks within each population. Phylogenetic reconstruction reinforced the assumption that all the haplotypes identified in RJ belong to A. sculptum. However, some RJ haplotypes are closer to A. sculptum from Argentina than to A. sculptum from elsewhere in Brazil. In RJ, A. sculptum has high genetic diversity, although little genetic differentiation. Observations also indicated a high level of gene flow among the studied populations and no evidence of population structure according to region in RJ. 相似文献
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K. Bitencourth M. Amorim S. V. de Oliveira C. M. Voloch G. S. Gazêta 《Medical and veterinary entomology》2019,33(2):256-268
Amblyomma ovale (Ixodida: Ixodidae) Koch, 1844 is widely‐reported in the neotropical region and is the main vector in the epidemic cycle of Rickettsia parkeri strain Atlantic rainforest, a bioagent of a milder variety of spotted fever (SF). Because species with wide geographical distributions are known to exhibit variations that influence their vectorial capacity, the present study aimed to analyze genetic diversity and rickettsia infection of A. ovale collected during the investigation and surveillance of SF cases in the Cerrado and Atlantic rainforest (ARF) Brazilian biomes. Samples had their DNA extracted, amplified and sequenced for 16S rDNA, 12S rDNA, cytochrome oxidase subunit II and D‐loop markers for tick analyses, as well as the gltA, htrA, ompA and ompB genes for rickettsia detection. Between 11 and 33 A. ovale haplotypes were identified, all of them exclusive to areas within individual analyzed biome areas. The A. ovale populations appeared to be structured, with Cluster I restricted to Cerrado + ARF isolated in Caatinga and Cluster II to ARF continuous area. Rickettsia bellii, R. parkeri strain Atlantic rainforest (first report for Goiás state, Cerrado), Rickettsia asemboensis (first record in A. ovale for Brazil) and Rickettsia felis (first detection in this ixodid) were identified. A. ovale clusters were not associated with rickettsia types. 相似文献
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Plathymenia reticulata is a tropical tree native to the Brazilian Cerrado, one of the most important and endangered ecosystems in Brazil. This species presents high-quality wood and potential for recovery of degraded areas. Despite its importance, almost nothing is known about its genetic or ecological features. Random amplified polymorphic DNA (RAPD) markers were used to investigate the genetic diversity and structure of six natural populations of P. reticulata. DNAs from 117 adult individuals were amplified with 10 random primers and Shannon's index and amova were used to evaluate the levels of genetic diversity within and among populations. Through 72 markers, 70.8% of which were polymorphic, it was possible to obtain 117 unique RAPD phenotypes. The levels of genetic variability found in the six populations of P. reticulata were considerable and most of the genetic variation was found between individuals within populations, although pairwise PH(ST) values indicated significant divergence between populations. The among-population component accounted for, respectively, 12.3% and 16% of the genetic variation, according to amova and Shannon's index. These results were compared with other genetic studies on plant species and such a level of differentiation among populations corresponds to that which has usually been observed for outcrossing plants. The importance of maintenance of the P. reticulata populations and implications of the analysis of adult individuals, considering the longevity of this species and the relatively recent Cerrado fragmentation, are discussed. 相似文献
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William A. Hoffmann 《Biotropica》2000,32(1):62-69
Due to frequent fire, low nutrient availability, and prolonged drought, tropical savanna is a stressful environment for the survival and growth of woody plant seedlings. To understand why forest species do not succeed in this environment while savanna species are able to persist, the effects of fire and woody cover on seedlings of these two functional groups were investigated in the Brazilian Cerrado. Seedlings were established in experimental plots under three densities of woody cover, in sites protected from fire and sites to be subjected to fire. There was a clear difference in the ability of savanna and forest species to survive fire. None of the three forest species were able to survive fire during the first two years of life, whereas eight of the nine savanna species were able to resprout following fire. The small seed size of the ninth savanna species, Miconia albicans, predisposed its seedlings to be sensitive to fire, because there was a strong positive correlation between seed size and survivorship. Savanna species were less dependent on woody cover than were forest species, which exhibited higher growth and survival under tree canopies than in open grassland. The low rates of establishment and survival of forest trees in savanna, combined with high sensitivity to fire, appear sufficient to prevent the expansion of forest into savanna under current fire regimes in the Cerrado. 相似文献
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Trade‐offs between savanna woody plant diversity and carbon storage in the Brazilian Cerrado
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Adam F.A. Pellegrini Jacob B. Socolar Paul R. Elsen Xingli Giam 《Global Change Biology》2016,22(10):3373-3382
Incentivizing carbon storage can be a win‐win pathway to conserving biodiversity and mitigating climate change. In savannas, however, the situation is more complex. Promoting carbon storage through woody encroachment may reduce plant diversity of savanna endemics, even as the diversity of encroaching forest species increases. This trade‐off has important implications for the management of biodiversity and carbon in savanna habitats, but has rarely been evaluated empirically. We quantified the nature of carbon‐diversity relationships in the Brazilian Cerrado by analyzing how woody plant species richness changed with carbon storage in 206 sites across the 2.2 million km2 region at two spatial scales. We show that total woody plant species diversity increases with carbon storage, as expected, but that the richness of endemic savanna woody plant species declines with carbon storage both at the local scale, as woody biomass accumulates within plots, and at the landscape scale, as forest replaces savanna. The sharpest trade‐offs between carbon storage and savanna diversity occurred at the early stages of carbon accumulation at the local scale but the final stages of forest encroachment at the landscape scale. Furthermore, the loss of savanna species quickens in the final stages of forest encroachment, and beyond a point, savanna species losses outpace forest species gains with increasing carbon accumulation. Our results suggest that although woody encroachment in savanna ecosystems may provide substantial carbon benefits, it comes at the rapidly accruing cost of woody plant species adapted to the open savanna environment. Moreover, the dependence of carbon‐diversity trade‐offs on the amount of savanna area remaining requires land managers to carefully consider local conditions. Widespread woody encroachment in both Australian and African savannas and grasslands may present similar threats to biodiversity. 相似文献
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Range expansions are a potential outcome of changes in habitat suitability, which commonly result as a consequence of climate change. Hypotheses on such changes in the geographic distribution of a certain species can be evaluated using population genetic structure and demography. In this study we explore the population genetic structure, genetic variability, demographic history of, and habitat suitability for Amblyomma americanum, a North American tick species that is a known vector of several pathogenic microorganisms. We used a double digestion restriction site‐associated DNA sequencing technique (dd‐RAD seq) and discovered 8,181 independent single nucleotide polymorphisms (SNPs) in 189 ticks from across the geographic range of the species. Genetic diversity was low, particularly when considering the broad geographic range of this species. The edge populations were less diverse than populations belonging to the historic range, possibly indicative of a range expansion, but this hypothesis was not statistically supported by a test based on genetic data. Nonetheless, moderate levels of population structure and substructure were detected between geographic regions. For New England, demographic and species distribution models support a scenario where A. americanum was present in more northern locations in the past, underwent a bottleneck, and subsequently recovered. These results are consistent with a hypothesis that this species is re‐establishing in this area, rather than one focused on range expansion from the south. This hypothesis is consistent with old records describing the presence of A. americanum in the northeastern US in the early colonial period. 相似文献
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de Siqueira Samantha Maciel da Costa Maia Rodrigo do Nascimento Ramos Vanessa da Silva Rodrigues Vinicius Szabó Matias Pablo Juan 《Experimental & applied acarology》2021,84(3):659-672
Experimental and Applied Acarology - We herein describe zebuine cattle tick infestation in a farm in southeast Brazil with an examination accurate enough to detect tick immatures and species other... 相似文献
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Fourteen polymorphic microsatellite loci (di, tetra and di‐tetra complexes) were developed for the argasid tick Ornithodoros coriaceus. Polymorphism was assessed for 56 individuals from two populations separated by ~95 km. All loci were polymorphic (X = 7, range 3–17 alleles). All loci were in Hardy–Weinberg equilibrium except for one locus (OrC 8) in a single population (P < 0.00119, after Bonferroni correction for multiple tests). 相似文献
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Small‐ and large‐scale heterogeneity in genetic variation across the collard flycatcher genome: implications for estimating genetic diversity in nonmodel organisms
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Population genetic studies in nonmodel organisms are often hampered by a lack of reference genomes that are essential for whole‐genome resequencing. In the light of this, genotyping methods have been developed to effectively eliminate the need for a reference genome, such as genotyping by sequencing or restriction site‐associated DNA sequencing (RAD‐seq). However, what remains relatively poorly studied is how accurately these methods capture both average and variation in genetic diversity across an organism's genome. In this issue of Molecular Ecology Resources, Dutoit et al. (2016) use whole‐genome resequencing data from the collard flycatcher to assess what factors drive heterogeneity in nucleotide diversity across the genome. Using these data, they then simulate how well different sequencing designs, including RAD sequencing, could capture most of the variation in genetic diversity. They conclude that for evolutionary and conservation‐related studies focused on the estimating genomic diversity, researchers should emphasize the number of loci analysed over the number of individuals sequenced. 相似文献
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Population genetics of the hispid cotton rat (Sigmodon hispidus): patterns of genetic diversity at the major histocompatibility complex 总被引:2,自引:0,他引:2
The hispid cotton rat, Sigmodon hispidus, is a common rodent widely distributed across the southern USA and south into South America. To characterize major histocompatibility complex (MHC) diversity in this species and to elucidate large-scale patterns of genetic partitioning, we examined MHC genetic variability within and among 13 localities, including a disjunct population in Arizona and a population from Costa Rica that may represent an undescribed species. We also tested the hypothesis that populations within the USA are at equilibrium with regard to gene flow and genetic drift, resulting in isolation-by-distance. Using single-strand conformation polymorphism (SSCP) analysis we identified 25 alleles from 246 individuals. Gene diversity within populations ranged from 0.000 to 0.908. Analysis of molecular variance (AMOVA) revealed that 83.7% of observed variation was accounted for by within-population diversity and 16.3% was accounted for by among-population divergence. The disjunct population in Arizona was fixed for a single allele. The Costa Rican population was quite divergent based on allelic composition and was the only population with unique alleles. Within the main portion of the geographical distribution of S. hispidus in the USA there was considerable divergence among some populations; however, there was no significant pattern of isolation-by-distance overall (P = 0.090). Based on the significant divergence of the only sampled population to its east, the Mississippi River appears to represent a substantial barrier to gene flow. 相似文献
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Higher genetic diversity on mountain tops: the role of historical and contemporary processes in shaping genetic variation in the bank vole
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Luca Cornetti Mélissa Lemoine Daniela Hilfiker Jennifer Morger Kevin Reeh Barbara Tschirren 《Biological journal of the Linnean Society. Linnean Society of London》2016,118(2):233-244
Glacial phases during the Pleistocene caused remarkable changes in species range distributions, with inevitable genetic consequences. Specifically, during interglacial phases, when the ice melted and new habitats became suitable again, species could recolonize regions that were previously covered by ice, such as high latitudes and elevations. Based on theoretical models and empirical data, a decrease in genetic variation is predicted along recolonization routes as a result of the consecutive founder effects that characterize the recolonization process. In the present study, we assessed the relative importance of historical and contemporary processes in shaping genetic diversity and differentiation of bank vole (Myodes glareolus) populations at different elevations in the Swiss Alps. By contrast to expectations, we found that genetic variation increased with elevation. Estimates of recent migration rates and a contrasting pattern of genetic differentiation observed at the mitochondrial cytochrome b gene and nuclear microsatellites support the hypothesis that higher genetic diversity at high elevation results from contemporary gene flow. Although historical recolonization processes can have marked effects on the genetic structure of populations, the present study provides an example where contemporary processes along an environmental gradient can reverse predicted patterns of genetic variation. 相似文献
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Abstract. Tropical forests are species-diverse communities, but we know very little about the geographical distribution of genetic diversity within a species. During the late Pleistocene, lower temperatures and rainfall reduced the distribution of tropical wet forests, and in Central America lowland species may have been limited to riparian habitats. Approximately 12,000 years bp , temperature and rainfall increased in Central America, the distribution of wet forest species expanded, and today the distribution of some species extends into southern Mexico. The distribution of genetic diversity, based on RAPD markers, among ten populations of Poulsenia armata (Miq.) Standl. (Moraceae) suggests that these populations did not originate from a single refugium or region in the late Pleistocene. The Central American populations had high genetic diversity and unique bands giving support to the hypothesis that populations of P. armata occurred in Central American during the late Pleistocene. The majority of genetic diversity was partitioned among populations and there was no geographical relationship among populations, suggesting that these populations were isolated for a long period and there has been little gene flow. Populations of P. armata may have persisted in riparian zones along the Caribbean coast during the late Pleistocene. Given that riparian forest can support high levels of biodiversity in ecological time, and they have played an important role during periods of climate change over geological time, their conservation is of utmost importance particularly with the threat of a rapid shift in climatic patterns. 相似文献
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Genetic effects of habitat fragmentation may be undetectable because they are generally a
recent event in evolutionary time or because of confounding effects such as historical
bottlenecks and historical changes in species'' distribution. To assess the effects
of demographic history on the genetic diversity and population structure in the
Neotropical tree Dipteryx alata (Fabaceae), we used coalescence analyses coupled
with ecological niche modeling to hindcast its distribution over the last 21 000
years. Twenty-five populations (644 individuals) were sampled and all individuals were
genotyped using eight microsatellite loci. All populations presented low allelic richness
and genetic diversity. The estimated effective population size was small in all
populations and gene flow was negligible among most. We also found a significant signal of
demographic reduction in most cases. Genetic differentiation among populations was
significantly correlated with geographical distance. Allelic richness showed a spatial
cline pattern in relation to the species'' paleodistribution 21 kyr BP
(thousand years before present), as expected under a range expansion model. Our results
show strong evidences that genetic diversity in D. alata is the outcome of the
historical changes in species distribution during the late Pleistocene. Because of this
historically low effective population size and the low genetic diversity, recent
fragmentation of the Cerrado biome may increase population differentiation, causing
population decline and compromising long-term persistence. 相似文献
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We performed a comparative analysis of the genetic diversity and structure of two congeneric tree species, one critically endangered, with only 21 known individuals in the wild, Dimorphandra wilsonii, and the other widely distributed Dimorphandra mollis. Eight populations of D. mollis and all known trees of D. wilsonii, from three areas, were screened for variability with ISSR markers. Percentage of polymorphic bands, Nei's gene diversity and Shannon's index were considerably lower in D. wilsonii (P = 40.0%, h = 0.124 and I = 0.190), as compared to D. mollis (P = 70.4%, h = 0.190 and I = 0.297). Bayesian clustering showed that D. wilsonii individuals are clustered in three populations, which had high differentiation among them. Several measures for their conservation were suggested: protection of all extant populations, ex situ conservation of seeds, production of saplings in nurseries and foundation of new populations in reserve areas. 相似文献
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Functional connectivity and genetic diversity of Eulaema atleticana (Apidae,Euglossina) in the Brazilian Atlantic Forest Corridor: assessment of gene flow
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The mobility and dispersal of organisms affect population genetics and dynamics, and consequently affect persistence and the risk of extinction. Thus, it is important to understand how organisms move in the fragmented landscapes in order to manage populations and predict the effects of habitat changes on species persistence. This study evaluated the functional connectivity of an orchid bee (Eulaema atleticana Nemésio, 2009) with a high fidelity to forest habitats in the Brazilian Atlantic Forest Corridor by analyzing genetic diversity, spatial genetic structure, and gene flow estimated from microsatellite and mitochondrial markers. Genetic diversity was not correlated with area of the forest fragments, or with forest isolation. At the mosaic scale, Eulaema atleticana showed no significant or low genetic differentiation, indicating genetic homogeneity among forest fragments. A previous field study indicated that Eulaema atleticana was one of the most sensitive Euglossina bees to forest fragmentation but the present molecular analyses demonstrates that current gene flow is sufficient to maintain genetic variability at the mosaic scale. 相似文献