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1.
Sand-smelts are small fishes inhabiting inshore, brackish and freshwater environments and with a distribution in the eastern Atlantic and Mediterranean Sea, extending south into the Indian Ocean. Here, we present a broad phylogenetic analysis of the genus Atherina using three mitochondrial (control region, 12S and 16S) and two nuclear markers (rhodopsin and 2nd intron of S7). Phylogenetic analyses fully support the monophyly of the genus. Two anti-tropical clades were identified, separating the South African Atherina breviceps from the north-eastern Atlantic and Mediterranean Atherina' species. In European waters, two groups were found. The first clade formed by a well supported species-pair: Atherina presbyter (eastern Atlantic) and Atherina hepsetus (Mediterranean), both living in marine waters; a second clade included Atherina boyeri (brackish and freshwater environments) and two independent lineages of marine punctated and non-punctated fishes, recently proposed as separate species. Sequence divergence values strongly suggest multiple species within the A. boyeri complex.  相似文献   

2.
The identification of incipient ecological species represents an opportunity to investigate current evolutionary process where adaptive divergence and reproductive isolation are associated. In this study we analysed the genetic structure of marine and estuarine populations of the silverside fish Odontesthes argentinensis using nine microsatellite loci and 396 bp of the mitochondrial DNA (mtDNA) control region. Our main objective was to investigate the relationship among estuarine colonization, divergent selection and speciation in silversides. Significant genetic structure was detected among all marine and estuarine populations. Despite the low phylogeographic structure in mtDNA haplotypes, there was clear signal of local radiations of haplotypes in more ancient populations. Divergence among marine populations was interpreted as a combined result of homing behaviour, isolation by distance and drift. On the other hand, ecological shifts due to the colonization of estuarine habitats seem to have promoted rapid adaptive divergence and reproductive isolation in estuarine populations, which were considered as incipient ecological species. This conclusion is supported by the existence of a set of environmental factors required for successful reproduction of estuarine ecotypes. The pattern of genetic structure indicates that phenotypic and reproductive divergence evolved in the face of potential gene flow between populations. We suggest that the 'divergence-with-gene-flow' model of speciation may account for the diversification of estuarine populations. The approach used can potentially identify 'incipient estuarine species', being relevant to the investigation of the evolutionary relationships of silversides in several coastal regions of the world.  相似文献   

3.
Phylogenetic relationships of the Malagasy and Australasian rainbowfishes are investigated using 4394 characters derived from five mitochondrial genes (12S, 16S, tRNA-Valine, ND5, and COI), three nuclear genes (28S, histone H3, and TMO-4c4), and 102 morphological transformations. This study represents the first phylogenetic analysis of the endemic Malagasy family Bedotiidae and includes a nearly complete taxonomic review of all nominal species, as well as numerous undescribed species. Simultaneous analysis of the molecular and morphological datasets results in two equally most parsimonious trees. Results indicate that Bedotiidae (Bedotia+Rheocles) and Bedotia are monophyletic, whereas Rheocles is paraphyletic with the inclusion of two recently described species from northeastern Madagascar, R. vatosoa, and R. derhami. Rheocles vatosoa and R. derhami are sister taxa, and this clade is recovered as the sister group to Bedotia. The remaining species of Rheocles are not sexually dimorphic and comprise a clade that is recovered as the sister group to Bedotia+(R. derhami+R. vatosoa), all of which are sexually dichromatic, and sexually dimorphic for pigmentation and fin development. Three geographically distinct clades are recovered within Bedotia, one comprising species with distributions ranging from mid- to southeastern Madagascar, another including species restricted to eastern drainages north of the Masoala Peninsula, and a third comprising taxa with distributions extending from the Masoala Peninsula south to the Ivoloina River. The Australian/New Guinean melanotaeniids are monophyletic and are recovered as the sister group to Bedotiidae. The Australasian Telmatherinidae and Pseudomugilidae comprise a clade that is recovered as the sister group to the Melanotaeniidae-Bedotiidae clade. This sister-group relationship between Malagasy bedotiids and a clade restricted to Australia-New Guinea, and the absence of a close relationship between bedotiids and African or Mascarene atheriniforms, is congruent with the break-up of Gondwana, not a scenario reliant on Cenozoic trans-oceanic dispersal. Finally, results of the phylogenetic analysis indicate that Atheriniformes is polyphyletic and further corroborate recent morphological hypotheses, which have recovered Bedotiidae in a derived position within Atherinoidei.  相似文献   

4.
The phylogeny of the avian genus Emberiza and the monotypic genera Latoucheornis, Melophus and Miliaria (collectively the Old World Emberizini), as well as representatives for the New World Emberizini, the circumpolar genera Calcarius and Plectrophenax and the four other generally recognized tribes in the subfamily Emberizinae was estimated based on the mitochondrial cytochrome b gene and introns 6-7 of the nuclear ornithine decarboxylase (ODC) gene. Our results support monophyly of the Old World Emberizini, but do not corroborate a sister relationship to the New World Emberizini. Calcarius and Plectrophenax form a clade separated from the other Emberizini. This agrees with previous studies, and we recommend the use of the name Calcariini. Latoucheornis, Melophus and Miliaria are nested within Emberiza, and we therefore propose they be synonymized with Emberiza. Emberiza is divided into four main clades, whose relative positions are uncertain, although a sister relation between a clade with six African species and one comprising the rest of the species (30, all Palearctic) is most likely. Most clades agree with traditional, morphology-based, classifications. However, four sister relationships within Emberiza, three of which involve the previously recognized Latoucheornis, Melophus and Miliaria, are unpredicted, and reveal cases of strong morphological divergence. In contrast, the plumage similarity between adult male Emberiza (formerly Latoucheornis) siemsseni and the nominate subspecies of the New World Junco hyemalis is shown to be the result of parallel evolution. A further case of parallel plumage evolution, between African and Eurasian taxa, is pointed out. Two cases of discordance between the mitochondrial and nuclear data with respect to branch lengths and genetic divergences are considered to be the result of introgressive hybridization.  相似文献   

5.
Based on geometric morphometrics and discriminant analysis, the percentage of silverside Odontesthes hatcheri and Odontesthes bonariensis individuals identified by a taxonomic key and misclassified by discriminant analysis was obtained and a negative correlation between the percentage of misclassified individuals of O. hatcheri and the distance to the nearest hatchery stocking silversides was found, suggesting a genetic introgression. Morphological analyses between species, between populations and within populations pointed to the same anatomical structures, suggesting a nested variation related to environmental cues such as availability of littoral shelter. The dependence between the cephalic morphology of O. hatcheri and body size would be in agreement with the trophic niche shifts of the species. Introgression adds a new threat to the already observed decline of populations of O. hatcheri and suggests that this species deserves particular consideration in terms of conservation guidelines.  相似文献   

6.
Huffmanela moraveci n. sp. (Nematode: Trichosomoididae) is described from the skin of fins and gills of the silversides Odontesthes smitti Lahille, 1949, and Odontesthes nigricans Richardson, 1848 (Pisces: Atheriniformes), from southwestern Atlantic coast, on the basis of the morphology of adults and eggs found in the host tissues. Huffmanela moraveci n. sp. can be distinguished from Huffmanela carcharini, H. banningi, H. japonica, H. mexicana, H. paronai, H. schouteni, H. shikokuensis, H. branchialis, H. filamentosa, H. ossicola, and H. lata by the size and shape of the eggs. The adult stage of H. moraveci n. sp. can be differentiated from H. hufmani and H. canadensis by the position of the nerve ring and by the total esophagus length/body length ratio. Huffmanela moraveci n. sp. also differs from H. huffmani by the presence of bacillary bands and by the body length. This is the first report of a species of Huffmanela in South America, the first report of a species of Huffmanela with Odontesthes spp. as host, and the third known adult form in the genus.  相似文献   

7.
Synopsis In a high salinity estuary at North Inlet, South Carolina, co-occurrence and possible competition among adults of four dominant zooplanktivorous fishes were minimized by seasonal adjustments in lateral and vertical distributions as well as in dietary preferences. In winter, Atlantic silversides, Menidia menidia, occupied the entire water column while other planktivores were rare or absent from the estuary, and they consumed large prey such as mysid shrimps and fish larvae. An immigration of bay anchovies, Anchoa mitchilli, in the spring resulted in a redistribution of species with Atlantic silversides shifting to the surface waters and bay anchovies dominating the lower half of the water column. Both fishes consumed mostly copepods in the spring, but each favored a different species. There was little similarity in the large prey items consumed by the two fishes. Striped anchovies, Anchoa hepsetus, arrived in mid-summer and were most abundant at the surface while bay anchovies continued to dominate the bottom waters. Atlantic silversides were rare in all summer collections. The diets of the two anchovies were similar, but vertical separation during the period of maximum zooplankton abundance probably minimized competition. Rough silversides, Membras martinica, which were obligate surface dwellers, shared the upper water column with striped anchovies, but the two species had very different diets during their period of co-occurrence. Although seasonal changes in fish diets reflected shifts in zooplankton composition and all fishes consumed a variety of prey types, preferences for some prey taxa and total avoidance of others were indicated. Electivity indices indicated an especially strong selection for fiddler crab megalopae by all fishes in the summer and fall. All fishes, except rough silversides, which fed almost exclusively on copepods and crab zoeae, consumed large prey items when they were available. Fine scale partitioning of the food resources was apparent in the selection of different copepod and insect species by the fishes. Spatial and temporal separation in the distribution and/or dietary preferences of the zooplanktivores fishes probably reduces the potential for resource competition. Given the high abundances and selectivity of the planktivores, significant impacts on some zooplankton populations probably result.  相似文献   

8.
The Indo-Pacific marine atherinid fishes Atherinomorus forskalii (Rüppell, 1838), Atherinomorus lacunosus (Forster, 1801), and Atherinomorus pinguis (Lacepède, 1803) are redescribed as valid species based on the types and non-type specimens collected throughout the Indo-Pacific. They are similar to each other chiefly in having a wide midlateral band (almost the same or greater than the midlateral scale width), large mouth (posterior tip of upper jaw reaching to or beyond a vertical through anterior margin of pupil), and no distinct tubercle at the posterior end of the dentary. All three species are distinguishable from congeners by those characters. The three species have long been confused with each other or synonymized erroneously as a single species. Atherinomorus forskalii, known from the Red Sea and eastern Mediterranean, differs from Atherinomorus lacunosus and Atherinomorus pinguis in having conspicuous, large endopterygoid teeth, forming obvious tooth ridges. Atherinomorus lacunosus, widely distributed in almost the entire Indo-Pacific, from East Africa to Tonga, north to southern Japan, and south to northern Australia, differs from Atherinomorus pinguis in having a wider midlateral band (the lower margin reaching to almost the center of the fourth scale row at level of the anal fin origin vs. the lower margin reaching to the ventral end of the third scale row in Atherinomorus pinguis) and more numerous midlateral scales (40–44 vs. 38–41 in Atherinomorus pinguis). Atherina morrisi Jordan and Starks, 1906, Hepsetia pinguis mineri Nichols and Roemhild, 1951, Pranesus capricornensis Woodland, 1961, Pranesus maculatus Taylor, 1964, and Pranesus pinguis ruppelli Smith, 1965, are regarded as junior synonyms of Atherinomorus lacunosus. Atherinomorus pinguis is also widely distributed in the Indo-West Pacific, from East Africa to northern Australia and north to southern Japan. Atherina pectoralis Valenciennes, 1835, is considered a junior synonym of Atherinomorus pinguis. Supplementary material to this paper is available in electronic format at  相似文献   

9.
The CD genome species in the genus Oryza are endemic to Latin America, including O. alta, O. grandiglumis and O. latifolia. Origins and phylogenetic relationship of these species have long been in dispute and are still ambiguous due to their homogeneous genome type, similar morphological characteristics and overlapping distribution. In the present study, we sequenced two chloroplast fragments (matK and trnL-trnF) and portions of three nuclear genes (Adh1, Adh2 and GPA1) from sixteen accessions representing seven species with the C, CD, and E genomes, as well as one G genome species as the outgroup. Phylogenetic analyses using parsimony and distance methods strongly supported that the CD genome originated from a single hybridization event, and that the C genome species (O. officinalis or O. rhizomatis instead of O. eichingeri) served as the maternal parent while the E genome species (O. australiensis) was the paternal donor during the formation of CD genome. In addition, the consistent phylogenetic relationships among the CCDD species indicated that significant divergence existed between O. latifolia and the other two (O. alta and O. grandiglumis), which corroborated the suggestion of treating the latter two as a single species or as taxa within species.We thank Tao Sang of Michigan State University (East Lansing, USA) and Bao-rong Lu of Fudan University (Shanghai, China) for their encouragement and assistance. We are also grateful to the International Rice Research Institute (Manila, Philippines) for providing plant material for this study. This research was supported by the Chinese Academy of Sciences (kscxz-sw-101A), the National Natural Science Foundation of China (30025005) and the Program for Key International S & T Cooperation Project of P. R. China (2001CB711103).  相似文献   

10.
The big‐scale sand smelt Atherina boyeri lives in fresh water, brackish water and sea water of the western Atlantic Ocean and Mediterranean Sea. Previous studies concerning distribution, biometric characters and genetic molecular markers have suggested the possible existence of two or even three different groups or species of sand smelt, one ‘lagoon’ type and one (or two – punctuated and non‐punctuated on the flanks) ‘marine’ type. In this study, the presence and the localization of an insertion was described, c. 200 bp in length, in the mtDNA of the lagoon and marine punctuated specimens of A. boyeri and its absence in the marine non‐punctuated specimens, as well as in other two congeneric species, Atherina hepsetus and Atherina presbyter, and in the atheriniform Menidia menidia. The intergenic spacer is located between the tRNAGlu and cytochrome b (cyt b) genes and shares a c. 50% sequence similarity with cyt b. The distribution and the features of the intergenic spacer suggest that it might have originated from an event of gene duplication, which involved the cyt b gene (or, more likely, a part of it) and which took place in the common ancestor of the lagoon and the marine punctuated specimens. The data obtained therefore support the hypothesis of the existence of three cryptic and, or sibling species within the A. boyeri taxon and provide a genetic molecular marker to distinguish them.  相似文献   

11.
Gynaecotyla squatarolae (Digenea: Microphallidae) is a minute intestinal trematode whose natural hosts are aves. We conducted a feces screening survey in a coastal village of Muan-gun, where the residents routinely consume brackish water crabs as a food. Through this survey, a 50-year-old female was found to shed gymnophallid and heterophyid eggs in her stool, and 845 adult flukes were collected from her purged stool. The adult worms were morphologically grouped into three species. A total of 841 worms were Gymnophalloides seoi. Three worms were identified as G. squatarolae, and the last one proven to be Haplorchis pumilio. This is the first worldwide report of G. squatarolae infection in humans, and the first H. pumilio infection in Korean people.  相似文献   

12.
Reed beetles (Donaciinae) of the genus Macroplea Samouelle, 1819 live permanently submerged. Literature indicates that Macroplea mutica occurs in brackish water, whereas Macroplea appendiculata is restricted to freshwater. The salinity preference of these two species was tested in a linear and a circular device that offered a continuous salinity gradient. The distribution of animals in the devices was monitored over at least 3 h in each of the 21 experiments. Both species preferred freshwater (salinity 0) over brackish water (salinity 10). In particular, this holds true for specimens collected in brackish water. Likewise, immediate reactions could be observed when during such experiments the direction of the gradient was reversed. While M. mutica can be regarded as a truly marine insect, this marine environment does not strictly reflect its fundamental niche with respect to salinity preference. This is in line with accumulating evidence that M. mutica can be found in freshwater habitats (and M. appendiculata in brackish water). This indicates that the species’ distribution might be influenced by other factors like host plant preference or dispersal mechanisms. It is discussed if—in spite of similar fundamental niches—differences in salinity tolerance (and hence performance in brackish water) may have contributed to speciation in the genus Macroplea.  相似文献   

13.
Biosurfactants have been suggested as a method to control harmful algal blooms (HABs), but warrant further and more in-depth investigation. Here we have investigated the algicidal effect of a biosurfactant produced by the bacterium Pseudomonas aeruginosa on five diverse marine and freshwater HAB species that have not been tested previously. These include Alexandrium minutum (Dinophycaee), Karenia brevis (Dinophyceae), Pseudonitzschia sp. (Bacillariophyceae), in marine ecosystems, and Gonyostomum semen (Raphidophyceae) and Microcystis aeruginosa (Cyanophyecae) in freshwater. We examined not only lethal but also sub-lethal effects of the biosurfactant. In addition, the effect of the biosurfactant on Daphnia was tested. Our conclusions were that very low biosurfactant concentrations (5 μg mL−1) decreased both the photosynthesis efficiency and the cell viability and that higher concentrations (50 μg mL−1) had lethal effects in four of the five HAB species tested. The low concentrations employed in this study and the diversity of HAB genera tested suggest that biosurfactants may be used to either control initial algal blooms without causing negative side effect to the ecosystem, or to provoke lethal effects when necessary.  相似文献   

14.
The pore-systems of 17 extant species of Loxoconcha around Japan were studied in order to understand their phylogeny and evolution. The phylogeny was estimated by two steps. First, the 17 species were divided into two groups, Group A (12 species) and Group B (five species) by Pore pattern Below Eye tubercle (PBE) analysis. Then, intragroup relationships were estimated by Differentiation of Distributional pattern of Pore-system (DDP) analysis. PBE analysis reveals that species of Groups A and B have on average different ecological preferences. Species of Group A, which appeared in the late Pliocene, are more diverse, have both phytal and bottom-dwelling modes of life, possess fewer pore-systems in the ventral area, and inhabit normal marine environments. Species of Group B, whose oldest fossil record is the lower Miocene, are less diverse, have only bottom-dwelling species, possess more pore-systems in the ventral area, and tend to inhabit brackish water environments. The results of this study suggest that the differences in ecology may have had an impact on the late Cenozoic diversification around Japan. The primary invasion of Group B occurred before the lower Miocene,with no subsequent diversification. Group A invaded after the late Pliocene and immediately diversified, which created the present abundance of Loxoconcha species around Japan in both species diversity and variety of modes of life.  相似文献   

15.
While adult parasitic Hymenoptera in general feed on floral and extrafloral nectars, hemipteran-honeydews and fluids from punctured hosts, Diachasmimorpha longicaudata (Ashmead), an Old World opiine braconid introduced to tropical/subtropical America for the biological control of Anastrepha spp. (Tephritidae), can survive on fruit juices as they seep from injured fruit. An ability to exploit fruit juice would allow such a parasitoid to efficiently forage for hosts and food sources simultaneously. Two New World opiines, Doryctobracon areolatus (Szepligeti) and Utetes anastrephae (Viereck), are also prominent Anastrepha parasitoids and are roughly sympatric. All three species were provided with: (1) pulp and juice diets derived from a highly domesticated Old World fruit (orange, Citrus sinensis L.) that is only recently sympatric with the Mexican flies and parasitoids and so offered little opportunity for the evolution of feeding-adaptations and (2) a less-domesticated New World fruit (guava, Psidium guajava L.), sympatric over evolutionary time with D. areolatus and U. anastrephae. Both sexes of D. longicaudata died when provided guava pulp or juice at a rate similar to a water-only control. D. areolatus and U. anastrephae, presumably adapted to the nutrient/chemical constituents of guava, also died at a similar rate. Survival of all three species on orange pulp and juice was greater than on water, and often equaled that obtained on a honey and water solution. In confirmatory experiments in Mexico, D. areolatus and U. anastrephae, as well as other tephritid parasitoids Doryctobracon crawfordi (Viereck) and Opius hirtus (Fisher), all died at a significantly higher rates when provided guava in comparison to a honey and water diet. Such a result is likely due to guavas being repellent, innutritious or toxic. D. longicaudata clearly consumed guava juice tagged with a colored dye. Dilutions of orange and guava juice resulted in shorter lifespans than dilutions of orange juice and water demonstrating that there while diluted orange juice provided nutrition the addition of guava created toxicity. Given the differences in fruit-food quality, adult opiine food sources would not be obtainable at all oviposition sites and in the case of guava, more additional sites and foraging for food than previously postulated may be required.  相似文献   

16.
Although bacteria of the genus Shewanella belong to one of the readily cultivable groups of "Gammaproteobacteria", little is known about the occurrence and abundance of these microorganisms in the marine ecosystem. Studies revealed that of 654 isolates obtained from marine invertebrates (ophiuroid Amphiopholis kochii, sipuncula Phascolosoma japonicum, and holothurian Apostichopus japonicus, Cucumaria japonica), seawater and sediments of the North-West Pacific Ocean (i.e. the Sea of Japan and Iturup Is, Kurile Islands), 10.7% belonged to the genus Shewanella. The proportion of viable Shewanella species varied from 4% to 20% depending on the source of isolation. From the isolation study, representative strains of different phenotypes (from seventy presumptive Shewanella strains) were selected for detailed characterization using phenotypic, chemotaxonomic, and phylogenetic testing. 16S rDNA sequence-based phylogenetic analysis confirmed the results of tentative identification and placed the majority of these strains within only a few species of the genus Shewanella with 98-99% of 16S rDNA sequences identity mainly with S. japonica and S. colwelliana, suggesting that the strains studied might belong to these species. Numerically dominant strains of S. japonica were metabolically active and produced proteinases (gelatinases, caseinases), lipases, amylases, agarases, and alginases. Shewanella strains studied demonstrated weak antimicrobial and antifungal activities that might be an indication of their passive role in the colonization on living and non-living surfaces.  相似文献   

17.
Over the past 5 years, raphidophyte blooms have been frequently observed along the South Carolina coastal zone. During the 2002, 2003, and 2004 sampling seasons, we investigated temporal fluctuations of algicidal bacteria abundance against raphidophycean flagellates (Heterosigma akashiwo, Chattonella subsalsa, and Fibrocapsa japonica) using the microplate most probable number (MPN) method in three Kiawah Island brackish stormwater detention ponds (K1, K2, and K75). Local axenic isolates of H. akashiwo, C. subsalsa, and F. japonica were obtained and their susceptibility to algicidal bacteria tested. A total of 195 algicidal bacterial strains were isolated from raphidophyte blooms in the study ponds, and 6 of them were identified at the genus level, and the taxonomic specificity of their algicidal activity was tested against local (pond) and nonlocal isolates of raphidophytes (3 species, 10 total strains). In the ponds, a consistent association was found between raphidophyte bloom development and an increase in bacteria algicidal to the bloom species. In 12 of 15 cases, bloom decline followed the increase in algicidal bacteria to maximum abundances. Although variability was found in the taxonomic specificity of the algicidal bacteria effect (i.e. the number of raphidophyte species affected by a particular bacteria strain) and raphidophyte susceptibility (i.e. the number bacteria strains affecting a particular raphidophyte species), a toxic effect was always found when strains of a raphidophyte species were exposed to algicidal bacteria isolated from a bloom caused by that same species. The results suggest that algicidal bacteria may be an important limiting factor in raphidophyte bloom sustenance and can promote bloom decline in brackish lagoonal eutrophic estuaries.  相似文献   

18.
The phylogeny of Celastraceae tribe Celastreae, which includes about 350 species of trees and shrubs in 15 genera, was inferred in a simultaneous analysis of morphological characters together with nuclear (ITS and 26S rDNA) and plastid (matK, trnL-F) genes. A strong correlation was found between the geography of the species sampled and their inferred relationships. Species of Maytenus and Gymnosporia from different regions were resolved as polyphyletic groups. Maytenus was resolved in three lineages (New World, African, and Austral-Pacific), while Gymnosporia was resolved in two lineages (New World and Old World). Putterlickia was resolved as nested within the Old World Gymnosporia. Catha edulis (qat, khat) was resolved as sister to the clade of Allocassine, Cassine, Lauridia, and Maurocenia. Gymnosporia cassinoides, which is reportedly chewed as a stimulant in the Canary Islands, was resolved as a derived member of Gymnosporia and is more closely related to Lydenburgia and Putterlickia than it is to Catha. Therefore, all eight of these genera are candidates for containing cathinone- and/or cathine-related alkaloids.  相似文献   

19.
Recent phylogenetic studies of the subfamily of cricetid rodents (Sigmodntinae) have validated the taxonomic classification at the tribal level of the Andean Clade. It is possible that some endemic species from Patagonian South America are part of this new tribe, but previous studies have not evaluated this hypothesis due to the difficulty of obtaining samples. In this study, we evaluate the phylogenetic relationships of Akodon markhami (Pine, 1973), a species endemic to the Chilean Patagonia, using individuals recently captured at the type locality of this taxon. Our results indicate that this form of Akodon corresponds to a subspecies of Abrothrix olivaceus, and should be incorporated into the Andean Clade as a geographic race of this widely distributed species on the South American continent. Based on a molecular clock calibration, we dated the origin of this geographic race during the last glacial cycles of the Quaternary, as the result of a vicariant process.  相似文献   

20.
The evolutionary affinities within and among many groups of nine-primaried oscines remain unresolved. One such group is Sporophila, a large genus of New World tanager-finches. Our study focused particularly on clarifying the relationship between this genus and a closely related one, Oryzoborus, and on examining the phylogenetic affinities of the "capuchinos," a group of 11 Sporophila species that share a similar male plumage coloration pattern. Our phylogenetic analyses, based on 498 bp of mitochondrial DNA sequence, indicated that: (1) Oryzoborus is embedded within a well-supported clade containing all Sporophila species, which strongly suggests that both genera should be merged, (2) the species of capuchinos comprise a monophyletic group, implying that the plumage patterns common to all probably arose only once, and (3) the capuchinos clade is comprised of two sub-clades, one including two species that are distributed in northern South America and the other one containing eight species that are present south of the Amazon River. Mean sequence divergence among the southern capuchinos species was extremely low, suggesting a rapid radiation within the last half-million years that may be related to the high level of sexual selection present in the genus and might have been promoted by marine ingressions and egressions that occurred in some southern coastal regions of South America in the Late Pleistocene.  相似文献   

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