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1.
Hierarchical genetic structure was examined in the three geographically-defined subspecies of spotted owl (Strix occidentalis) to define relationships among subspecies and quantify variation within and among regional and local populations. Sequences (522 bp) from domains I and II of the mitochondrial control region were analyzed for 213 individuals from 30 local breeding areas. Results confirmed significant differences between northern spotted owls and the other traditional geographically defined subspecies but did not provide support for subspecific level differences between California and Mexican spotted owls. Divergence times among subspecies estimated with a 936 bp portion of the cytochrome b gene dated Northern and California/Mexican spotted owl divergence time to 115,000–125,000 years ago, whereas California/Mexican spotted owl divergence was estimated at 15,000 years ago. Nested clade analyses indicated an association between California spotted owl and Mexican spotted owl haplotypes, implying historical contact between the two groups. Results also identified a number of individuals geographically classified as northern spotted owls (S. o. caurina) that contained haplotypes identified as California spotted owls (S. o. caurina). Among all northern spotted owls sampled (n=131), 12.9% contained California spotted owl haplotypes. In the Klamath region, which is the contact zone between the two subspecies, 20.3% (n=59) of owls were classified as California spotted owls. The Klamath region is a zone of hybridization and speciation for many other taxa as well. Analyses of population structure indicated gene flow among regions within geographically defined subspecies although there was significant differentiation among northern and southern regions of Mexican spotted owls. Among all areas examined, genetic diversity was not significantly reduced except in California spotted owls where the southern region consists of one haplotype. Our results indicate a stable contact zone between northern and California spotted owls, maintaining distinct subspecific haplotypes within their traditional ranges. This supports recovery efforts based on the traditional subspecies designation for the northern spotted owl. Further, although little variation was found between California and Mexican spotted owls, we suggest they should be managed separately because of current isolation between groups.  相似文献   

2.
We used analyses of mitochondrial DNA restriction site polymorphisms to estimate population genetic structure and phylogenetic relationships among 42 individuals from two Asian leaf monkey species (Trachypithecus auratus and T. cristatus) and to compare them to the geographically proximate species, Presbytis comata. We amplified a 2300-base pair fragment spanning the mitochondrial NADH 3 and NADH 4 genes, including their tRNA flanking subunits, glycine and leucine, and digested it with a battery of 22 restriction endonucleases, yielding 21 unique multienzyme haplotypes and 60 variable restriction sites. Presbytis comata is clearly divergent from both Trachypithecus species. Within the Javan T. auratus, our analysis does not support the distinction of two subspecies currently recognized on the basis of morphological features (Weitzel and Groves, 1985). T. auratus and T. cristatus are not internally monophyletic with respect to each other in our phylogenetic analysis. These results indicate either a recent speciation event with the retention of ancestral polymorphisms or that the two taxa are not separate species. Therefore with respect to conserving genetic diversity within the leaf monkey, we would have to consider T. auratus and T. cristatus as essentially one large polymorphic, conservation unit. However, within that conservation unit, T. auratus of Java represent a separate management unit from T. auratus/T. cristatus of Sumatra and Peninsular Malaysia.  相似文献   

3.
Comparison of molecular data suggests that the higher apes (Gorilla, Pan) and humankind (Homo) are closely related and that they diverged from the common ancestor through two speciation events situated very closely together in time. Examination of the chromosomal formulas of the living species reveals a paradox in the distribution of mutated chromosomes which can only be resolved by a model of trichotomic diversification. This new model of divergence from the common ancestor is characterized by the transition from (1) a monotypic phase to (2) a polytypic phase of three sub-species — pre-gorilla, pre-chimpanzee and preaustralopithecine. The quadruped ancestors ofAustralopithecus appear to have been one of the three components of the common ancestor. The question is whetherramidus is an australopithecine or a pre-australopithecine representative of the common ancestor. The new model of diversification of the common ancestor is resituated in the paleogeographic and paleoclimatic context which, through the north-south pattern of extension of aridity, provides a coherent scenario for the formation of extant species and subspecies of theGorilla andPan genera.  相似文献   

4.
We studied the intraspecific evolutionary history of the South American Atlantic forest endemic Xiphorhynchusfuscus (Aves: Dendrocolaptidae) to address questions such as: Was the diversification of this bird's populations associated to areas of avian endemism? Which models of speciation (i.e., refuges, river as barriers or geotectonism) explain the diversification within X. fuscus? Does the genetic data support subspecies as independent evolutionary units (species)? We used mitochondrial (n=34) and nuclear (n=68) DNA sequences of X. fuscus to study temporal and spatial relationships within and between populations. We described four main monophyletic lineages that diverged during the Pleistocene. The subspecies taxonomy did not match all the evolutionary lineages; subspecies atlanticus was the only one that represented a monophyletic and isolated lineage. The distribution of these lineages coincided with some areas of endemism for passerines, suggesting that those areas could be regions of biotic differentiation. The ancestor of X. fuscus diverged approximately 3 million years ago from Amazonian taxa and the phylogeographic pattern suggested that X. fuscus radiated from northeastern Brazil. Neither the riverine nor the geotectonic vicariance models are supported as the primary cause for diversification of geographic lineages, but rainforest contractions and expansions (ecological vicariance) can explain most of the spatial divergence observed in this species. Finally, analyses of gene flow and divergence time estimates suggest that the endangered subspecies atlanticus (from northeastern Brazil) can be considered a full species under the general lineage species concept.  相似文献   

5.
Cicindela (Cylindera) terricola Say is one of the most widespread and variable species of Nearctic Cicindelidae with six recognized subspecies. Cicindela t. lunalonga Schaupp (1884) is known from few museum specimens collected prior to 1979. The goal of this study was to resolve the uncertain taxonomic status of C. t. lunalonga using mitochondrial DNA analysis of cytochrome b and cytochrome oxidase subunit I and determine its conservation status. In phylogenetic reconstruction using distance and parsimony methods, all members of the terrricola group were recovered as monophyletic and embedded within outgroup species of the subgenus Cylindera, while C. lunalonga was recovered as sister to all other members of the C. terricola clade. Cicindela lunalonga exhibited an exceptionally high (mean of 6.36%) pairwise sequence divergence for both genes against all C. terricola surveyed. For the cytochrome oxidase subunit I alone the pairwise divergence was 3.9–4.8% (4.58% avg.). The lowest divergences were between C. lunalonga and C. terricola subspecies of the American southwest (C. t. cinctipennis and C. t. kaibabensis), rather than with the closest geographic neighbors (C. t. imperfecta). We conclude that based on strict monophyly and pairwise sequence divergence, C. lunalonga is a distinct species. Our study of museum specimens and extensive field surveys suggest this species has been extirpated from all sites in the San Joaquin Valley and perhaps all but one of the historic sites throughout its range. Thus, it should be considered for Federal listing as an endangered species.  相似文献   

6.
Kopp A  Frank AK 《Genetica》2005,125(1):55-68
Incipient species in the early stages of divergence can provide crucial information about the genetic basis of reproductive isolation and the evolutionary forces that promote speciation. In this report, we describe two subspecies of Drosophila bipectinata that show a continuum of reproductive isolation. Crosses between strains of the same subspecies produce fully fertile offspring. At the same time, each subspecies harbors extensive variation for the degree of reproductive isolation from the other subspecies. The percentage of fertile hybrid males varies from 0 to 90%, depending on the origin of parental strains, indicating that the genes responsible for hybrid sterility are not fixed within either subspecies, or even within local populations. Reproductive isolation is non-transitive, so that the extent of hybrid sterility depends on the particular combination of strains. The two subspecies show little or no evidence of genetic differentiation at three nuclear loci, suggesting that they diverged very recently or continue to experience significant levels of gene flow. A hybrid zone between the two subspecies may exist in New Guinea and Northeastern Australia.  相似文献   

7.
We surveyed population-level sequence variation in part of the mitochondrial control region for three species including eight subspecies of Cepphus guillemots (Charadriiformes: Alcidae) to test specific predictions about mechanisms of population differentiation. We found that sequences of spectacled guillemots (C. carbo) were more closely related to those of pigeon guillemots (C. columba; both found in the Pacific Ocean) than to those of black guillemots (C. grylle; Arctic and Atlantic Oceans), despite dissimilarities in plumage between spectacled guillemots and the other species. Distributions of species and timing of divergence events suggest that speciation involved allopatric and microallopatric populations isolated by Pleistocene glaciers. Control region sequences were significantly differentiated among populations within species and suggest that gene flow is low; however, populations are probably not in genetic equilibrium, so these results probably reflect historical isolation of colonies. In contrast, phylogenetic relationships among sequences within species were poorly resolved, probably because of a combination of incomplete lineage sorting and contemporary gene flow. Indices of genetic diversity provided no suggestion of recent bottlenecks in most populations, although two populations apparently underwent recent severe bottlenecks. Genetic divergence among populations was not correlated with geographic distance, which argues against isolation by distance. Results of these analyses, combined with breeding distributions and timing of divergence events, suggest that populations diverged during isolation in glacial refugia. Our results are consistent with earlier hypotheses posed by Storer and Udvardy.  相似文献   

8.
The Guadeloupean racoon has been chosen as the emblematic species of the Parc National de Guadeloupe because of its supposed endemic specificity. However, its taxonomic position is not clearly defined. At what period did this animal colonize Guadeloupe and how it reached the island remain unsolved questions. To clarify these points, insular and continental individuals (Procyon lotor), coming from five localities and belonging to three subspecies, were compared using molecular (sequencing of a 294-bp of the left domain of the mtDNA control region) and chromosomal (C, G and R karyotypes) analyses. Genetic distance between the Guadeloupean racoon and lotor subspecies from Virginia and Maryland was very short (mean sequence divergence between haplotypes equals to 1.46%). A four times higher distance was found between P. l. lotor and P. l. pallidus, a continental subspecies inhabiting Arizona than between P. l. lotor and Procyon minor. A neighbour-joining phenogram is proposed; the Guadeloupean haplotype is on a branch close to the one clustering P. l. lotor from the East coast whereas the haplotype from Arizona diverged earlier. These results strongly suggest that the Guadeloupean racoon is included in the P. lotor species. Moreover, no differences were found between P. lotor and P. minor karyotypes, again suggesting a high genetic homogeneity between the two taxa. Furthermore, comparison of the control region variability within Procyon with intra- and interspecific variability observed in other Carnivores, clearly strengthens the hypothesis that P. minor is conspecific with P. lotor. These results imply that the taxonomic status of the Guadeloupean racoon should be revised. In a biogeographic perspective, it is suggested that the racoon has been recently introduced in Guadeloupe by man with individuals coming from the east coast of the USA. The consequences of these results for conservation of the racoon in Guadeloupe, and more generally, the definition and the use of the subspecies as a unit of conservation are discussed.  相似文献   

9.
Speciation by polyploidy is rare in animals, yet, in vertebrates, there is a disproportionate concentration of polyploid species in anuran amphibians. Sequences from the cytochrome b gene of the mitochondrial DNA (mtDNA) were used to determine phylogenetic relationships among 37 populations of the diploid-tetraploid species pair of gray treefrogs, Hyla chrysoscelis and Hyla versicolor. The diploid species, H. chrysoscelis, consists of an eastern and a western lineage that have 2.3% sequence divergence between them. The tetraploid species, H. versicolor, had at least three separate, independent origins. Two of the tetraploid lineages are more closely related to one or the other of the diploid lineages (0.18%–1.4% sequence divergence) than they are to each other (1.9%–3.4% sequence divergence). The maternal ancestor of the third tetraploid lineage is unknown. The phylogenetic relationships between the two species and among lineages within each species support the hypothesis of multiple origins of the tetraploid lineages.  相似文献   

10.
Aim To examine the phylogeography and population structure of three dung beetle species of the genus Trypocopris (Coleoptera, Geotrupidae). We wanted to test whether genetic differences and genealogies among populations were in accordance with morphologically described subspecies and we aimed to establish times of divergence among subspecies to depict the appropriate temporal framework of their phylogeographical differentiation. We also wished to investigate the historical demographic events and the relative influences of gene flow and drift on the distribution of genetic variability of the different populations. Location Europe (mostly Italy). Methods We collected adult males from dung pats from 15 Italian localities over the period 2000–2002. For sequence analysis, some dried specimens from Albania, Croatia, Slovakia and Spain were also used. We applied cytochrome oxidase I mitochondrial DNA sequencing and the amplified fragment length polymorphism (AFLP) technique to determine whether phylogeographical patterns within the three species support the proposed hypotheses of subspecies designations, and to detect further structure among populations that might mediate diversification. Results and main conclusions The results show a high concordance between the distribution of mtDNA variation and the main morphological groups recognized as subspecies, which thus may represent independent evolutionary units. The degree of mitochondrial divergence suggests that speciation events occurred during the Pliocene, while diversification of the main subspecific lineages took place in the Pleistocene, from c. 0.3 to 1.5 Ma. Mitochondrial and nuclear data also reveal that there is phylogeographical structuring among populations within each of the main groups and that both contemporary and historical processes determined this pattern of genetic structure. Geographical populations form monophyletic clades in both phylogenetic and network reconstructions. Despite the high levels of intrapopulational diversity, FST values indicate moderate but significant genetic differentiation among populations, and a Bayesian clustering analysis of the AFLP data clearly separates the geographical populations. Nucleotide and gene diversity estimates reveal interspecific differences in the degree of diversification among populations that may be related to the different ecological requirements of the three species.  相似文献   

11.
12.
Echinometra is a pantropical sea urchin made famous through studies of phylogeny, speciation, and genetic structure of the Indo-West Pacific (IWP) species. We sequenced 630 bp of the cytochrome oxidase I (COI) mitochondrial gene to provide comparable information on the eastern Pacific and Atlantic species, using divergence between those separated by closure of the Isthmus of Panama 3.1 million years ago (Ma) to estimate dates for cladogenic events. Most recently (1.27-1. 62 Ma), the Atlantic species E. lucunter and E. viridis diverged from each other, at a time in the Pleistocene that sea levels fell and Caribbean coral speciation and extinction rates were high. An earlier split, assumed to have been coincident with the completion of the Isthmus of Panama, separated the eastern Pacific E. vanbrunti from the Atlantic common ancestor. Transisthmian COI divergence similar to that in the sea urchin genus Eucidaris supports this assumption. The most ancient split in Echinometra occurred between the IWP and the neotropical clades, due to cessation of larval exchange around South Africa or across the Eastern Pacific Barrier. Gene flow within species is generally high; however, there are restrictions to genetic exchange between E. lucunter populations from the Caribbean and those from the rest of the Atlantic. Correlation between cladogenic and vicariant events supports E. Mayr's contention that marine species, despite their high dispersal potential, form by means of geographical separation. That sympatric, nonhybridizing E. lucunter and E. viridis were split so recently suggests, however, that perfection of reproductive barriers between marine species with large populations can occur in less than 1.6 million years (Myr).  相似文献   

13.
Effective conservation that preservesevolutionary entities and processes requiresconservation action that is targeted atappropriate taxonomic units. Molecularphylogenetics can contribute to the resolutionof taxonomic uncertainties by defining therelationships between populations and species,and allowing the recognition of taxonomicentities that reflect evolutionary history.Some uncertainty surrounds the status of taxain the Eucalyptus angustissima complex,which includes threatened taxa with restricteddistributions. The phylogenetic relationshipsbetween populations and taxa in the E.angustissima complex were investigated usingnuclear and chloroplast RFLP analysis.Phylogenetic relationships confirmed thegenetic differentiation of two taxa, identifiedspecies level divergence between two taxacurrently recognised at subspecies level, andestablished the identity of a previouslyundetermined population. Phylogeneticrelationships between the taxa were notcongruent with presumed relationships based onmorphological characters alone.  相似文献   

14.
Determining the genetic bases of adaptations and their roles in speciation is a prominent issue in evolutionary biology. Cichlid fish species flocks are a prime example of recent rapid radiations, often associated with adaptive phenotypic divergence from a common ancestor within a short period of time. In several radiations of freshwater fishes, divergence in ecomorphological traits — including body shape, colour, lips and jaws — is thought to underlie their ecological differentiation, specialization and, ultimately, speciation. The Midas cichlid species complex (Amphilophus spp.) of Nicaragua provides one of the few known examples of sympatric speciation where species have rapidly evolved different but parallel morphologies in young crater lakes. This study identified significant QTL for body shape using SNPs generated via ddRAD sequencing and geometric morphometric analyses of a cross between two ecologically and morphologically divergent, sympatric cichlid species endemic to crater Lake Apoyo: an elongated limnetic species (Amphilophus zaliosus) and a high‐bodied benthic species (Amphilophus astorquii). A total of 453 genome‐wide informative SNPs were identified in 240 F2 hybrids. These markers were used to construct a genetic map in which 25 linkage groups were resolved. Seventy‐two segregating SNPs were linked to 11 QTL. By annotating the two most highly supported QTL‐linked genomic regions, genes that might contribute to divergence in body shape along the benthic–limnetic axis in Midas cichlid sympatric adaptive radiations were identified. These results suggest that few genomic regions of large effect contribute to early stage divergence in Midas cichlids.  相似文献   

15.
Vicariance and isolation leading to speciation of reptiles on islands is well exemplified in a number of taxa in the Caribbean. The St. Lucia whiptail (Cnemidophorus vanzoi), considered a single species, is found on two small islets (Maria Major and Maria Minor) off the main island of St. Lucia. From lizards collected from both localities, we gathered morphological measurements and analysed the genetic divergence between populations, using a molecular survey of ∼ ∼2800 mtDNA base pairs and 8 microsatellites. There are significant differences in body size and general form and fixed but small mtDNA differences between island populations. Microsatellites reveal low diversity within populations but very high differentiation between islands with non-overlapping allele size ranges at all except one microsatellite and two loci exhibiting single-base polymorphism, fixed between islands. Based on these results, we examine published criteria to determine whether the studied island forms could be considered true species. According to the phylogenetic species concept and Moritz’s evolutionary significant unit (ESU) criteria, the two lizard populations can be considered separate entities. Crandall et al.’s (2000, Trends Ecol. Evol., 15, 290–295) broader categorization of population distinctiveness, based on concepts of ecological and genetic exchangeability, produces conflicting results depending on the interpretation of the observed ecological data. Following Fraser and Bernatchez’s (2001, Mol. Ecol., 10, 2741–2752) framework for management decisions when ecological data are not sufficient we propose that the lizard populations on the Maria islands are on differing evolutionary trajectories and thus at the species boundary. The populations are of high priority to conservation, thus meriting separate management.  相似文献   

16.
Echium hypertropicum, E. stenosiphon and E. vulcanorum are the three endemics representative of the genus Echium (Boraginaceae) in Cape Verde archipelago. The aim of this study is to provide a first attempt at estimating genetic diversity among natural populations of these endangered Echium species based on RAPD, so as to provide data available for future appropriate strategies for their conservation. PCO and UPGMA of RAPD analysis suggests a close genetic proximity between the Southern endemic species (E. hypertropicum and E. vulcanorum) and shows that the levels of polymorphism strongly differ between these two Echium species (27 and 29% respectively) and E. stenosiphon (74%), the Northern endemic species. Mantel test also corroborates a close genetic proximity between genetic and geographic data. Population genetic analysis of E. stenosiphon revealed low levels of gene flow between islands (Nm = 0.32) being S. Nicolau the most isolated as evident in PCO. Furthermore the differentiation between groups of individuals belonging to putative subspecies was tested by AMOVA. According to our results there is no genetic basis to consider the two subspecies of E. stenosiphon namely ssp. stenosiphon and ssp. lindbergii. Our results enable us to suggest that E. stenosiphon must be ranked as a Threatened species. Measures aiming at conservation of E. hypertropicum and E. vulcanorum must be implemented at short-term taking into account the small number of existing plants and its low genetic variability.  相似文献   

17.
The genus Diplodus presents multiple cases of taxonomic conjecture. Among these the D. cervinus complex was previously described as comprising three subspecies that are now regarded as separate species: Diplodus cervinus, Diplodus hottentotus and Diplodus omanensis. Diplodus hottentotus exhibits a clear break in its distribution around the Benguela Current system, prompting speculation that Angolan and South African populations flanking this area may be isolated and warrant formal taxonomic distinction. This study reports the first integrated genetic [mitochondrial (mt)DNA and nuclear microsatellite] and morphological (morphometric, meristic and colouration) study to assess patterns of divergence between populations in the two regions. High levels of cytonuclear divergence between the populations support a prolonged period of genetic isolation, with the sharing of only one mtDNA haplotype (12 haplotypes were fully sorted between regions) attributed to retention of ancestral polymorphism. Fish from the two regions were significantly differentiated at a number of morphometric (69·5%) and meristic (46%) characters. In addition, Angolan and South African fish exhibited reciprocally diagnostic colouration patterns that were more similar to Mediterranean and Indian Ocean congeners, respectively. Based on the congruent genetic and phenotypic diversity we suggest that the use of hottentotus, whether for full species or subspecies status, should be restricted to South African D. cervinus to reflect their status as a distinct species‐like unit, while the relationship between Angolan and Atlantic–Mediterranean D. cervinus will require further demo‐genetic analysis. This study highlights the utility of integrated genetic and morphological approaches to assess taxonomic diversity within the biogeographically dynamic Benguela Current region.  相似文献   

18.
Determining how genetic diversity is structured between populations that span the divergence continuum from populations to biological species is key to understanding the generation and maintenance of biodiversity. We investigated genetic divergence and gene flow in eight lineages of birds with a trans‐Beringian distribution, where Asian and North American populations have likely been split and reunited through multiple Pleistocene glacial cycles. Our study transects the speciation process, including eight pairwise comparisons in three orders (ducks, shorebirds and passerines) at population, subspecies and species levels. Using ultraconserved elements (UCEs), we found that these lineages represent conditions from slightly differentiated populations to full biological species. Although allopatric speciation is considered the predominant mode of divergence in birds, all of our best divergence models included gene flow, supporting speciation with gene flow as the predominant mode in Beringia. In our eight lineages, three were best described by a split‐migration model (divergence with gene flow), three best fit a secondary contact scenario (isolation followed by gene flow), and two showed support for both models. The lineages were not evenly distributed across a divergence space defined by gene flow (M) and differentiation (FST), instead forming two discontinuous groups: one with relatively shallow divergence, no fixed single nucleotide polymorphisms (SNPs), and high rates of gene flow between populations; and the second with relatively deeply divergent lineages, multiple fixed SNPs, and low gene flow. Our results highlight the important role that gene flow plays in avian divergence in Beringia.  相似文献   

19.
Hybridization between wild species and their domestic congeners often threatens the gene pool of the wild species. The last wild Bactrian camel (Camelus ferus) populations in Mongolia and China are examples of populations facing such a hybridization threat. To address this key issue in the conservation of wild camels, we analysed wild, hybrid and domestic Bactrian camels (Camelus bactrianus) originating from Mongolia, China and Austria. Through screening of an 804‐base‐pair mitochondrial fragment, we identified eight mitochondrial haplotypes and found high sequence divergence (1.9%) between C. ferus and C. bactrianus. On the basis of a mitochondrial DNA sequence fixed difference, we developed a diagnostic PCR restriction fragment length polymorphism (PCR‐RFLP) assay to differentiate between wild and domestic camel samples. We applied the assay to 81 individuals and confirmed the origin of all samples including five hybrids with known maternal ancestry. The PCR‐RFLP system was effective for both traditional (blood, skin) and non‐invasive samples (faeces, hair), as well as for museum specimens. Our results demonstrate high levels of mitochondrial differentiation between wild and domestic Bactrian camels and that maternal hybridization can be detected by a rapid and reliable PCR‐RFLP system.  相似文献   

20.
This article describes the complete sequences of the mitochondrial DNA displacement loop (D-loop) region and cytochrome b gene from domestic goats in Laos (Laos native) and wild goat markhor (C. falconeri). The wild goat bezoar (Capra aegagrus) has been considered to be the strongest candidate for the ancestor of the domestic goats (C. hircus); however, there is not sufficient molecular data to verify the hypothesis at present. In phylogenetic analyses, two wild goats, the markhor and the ibex (C. ibex), appeared as an outgroup, while the bezoar was located in a cluster of domestic goats. Mitochondrial haplotypes of Laos natives revealed two distinct major clusters: one was the same as the bezoar, the second, unique to Laos natives. The topology and calibrated levels of sequence divergence suggests that these clusters might represent at least two different subspecies of ancestral bezoars.  相似文献   

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