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1.
Albinaria (Gastropoda, Clausiliidae) is a pulmonate genus distributed around the north-eastern coasts of the Mediterranean. It is the most 'speciose' genus within the family of Clausiliidae, exhibiting a high degree of morphological and genetic differentiation, and serving as a model for several ecological, systematics and evolutionary studies. Nevertheless, many aspects remain uncertain mainly due to the large number of taxa whose classification has not yet been evaluated with solid synapomorphic characters. Thirty-one morphological species are currently recognized on the island of Crete and its satellite islets. Four of them (A. retusa, A. torticollis, A. jaeckeli, and A. teres) are distributed on the island of Dia (north of Crete); the first three are island endemics. Here, we combined mitochondrial and nuclear DNA information and Bayesian and Maximum Likelihood approaches to evaluate the phylogenetic relationships, and assess the genetic distinctiveness and cohesiveness of all described species of Dia Island. The produced phylogeny was not congruent with the morphological species, demonstrating a more complex pattern of speciation and diversification. Although each island endemic constitutes a monophyletic lineage, the number of island endemic species could be greater than the three currently recognized species so far (A. retusa, A. torticollis, and A. jaeckeli), since a newly discovered lineage (north-western part of the island), that morphologically differs from the populations of A. torticollis in the eastern part, and genetically is more closely related to A. jaeckeli, could be elevated to the species level. Considering the fourth species found on the island of Dia, A. teres is genetically highly variable, showing low geographic structuring due to either long-distance gene flow or retained ancestral polymorphisms, or a combination of both. Further work (analysis of more specimens and DNA data) both from Dia and Crete is indispensable in order to shed light on aspects of the evolutionary history of the genus in Dia.  相似文献   

2.
Reversed chirality has frequently evolved in snails, although the vast majority coils dextrally. However, there are often sinistral species within a dextral genus or almost exclusively sinistral families, such as the Clausiliidae. Some populations of the predominantly sinistral clausiliid genus Albinaria, in the southern Greek mainland, coil dextrally. The origin, evolution and distribution of the dextral Albinaria are puzzling, and as there is no reliable phylogenetic reconstruction for this speciose genus, it remains unclear how many times a shift in chirality has really occurred. In this study, our aim was to elucidate the evolutionary pathways of dextrality in Albinaria. We undertook a molecular phylogenetic analysis of two mtDNA (16S and COI) and one nDNA marker (ITS1) and included dextral and sinistral representatives found in syntopy or not. Both mtDNA and nDNA tree topologies imply that dextrals did not evolve as a monophyletic lineage. Instead, dextral lineages have evolved from sinistral ancestors multiple times independently. The fragmented population structure in Albinaria facilitates genetic drift and contributes to fixation of the opposite chirality and overcoming of the mating disadvantage of left–right reversal. Stochastic phenomena and biogeographical barriers have trapped those reversals in a limited geographical area.  相似文献   

3.
A molecular phylogeny based on DNA/DNA hybridization revealed that the Sylvia-Parisoma complex is monophyletic and includes three main groups of species, the “mid-European” warblers, the genus Parisoma, and the “eu-Mediterranean” Sylvia species sensu stricto. The latter can be assigned to three main clusters, a “West-Mediterranean” group, a “Central-Mediterranean group”, and an “East-Mediterranean” group. The radiation of the whole complex is much more ancient than formerly believed. It started ca 12–13 Ma ago and the ancestors of the main extant groups differentiated during the Pliocene. Only speciation events within the “eu-Mediterranean” lineages occurred during the Pleistocene. The paleoclimatical and paleoecological history of the Mediterranean region is too complicated to provide any evidence for direct relationships between past events and evolutionary steps of these taxa which did not leave any reliable fossil record. However, some major speciation events may be related to well documented climatical crises as well as paleobotanical data. The largely man-induced extension of matorrals over several millenia presumably extended the range of several species that were formerly much more restricted, which complicates reconstruction of the spatio-temporal course of speciation.  相似文献   

4.
Nineteen taxa representing 10 genera of Sisoridae were subjected to phylogenetic analyses of sequence data for the nuclear genes Plagl2 and ADNP and the mitochondrial gene cytochrome b. The three data sets were analyzed separately and combined into a single data set to reconstruct phylogenetic relationships among Chinese sisorids. Both Chinese Sisoridae as a whole and the glyptosternoid taxa formed monophyletic groups. The genus Pseudecheneis is likely to be the earliest diverging extant genus among the Chinese Sisoridae. The four Pareuchiloglanis species included in the study formed a monophyletic group. Glaridoglanis was indicated to be earliest diverging glyptosternoid, followed by Glyptosternon maculatum and Exostoma labiatum. Our data supported the conclusion that Oreoglanis and Pseudexostoma both formed a monophyletic group. On the basis of the fossil record and the results of a molecular dating analysis, we estimated that the Sisoridae diverged in the late Miocene about 12.2 Mya. The glyptosternoid clade was indicated to have diverged, also in the late Miocene, about 10.7 Mya, and the more specialized glyptosternoid genera, such as Pareuchiloglanis, originated in the Pleistocene (within 1.9 Mya). The speciation of glyptosternoid fishes is hypothesized to be closely related with the uplift of the Qinghai-Tibet Plateau.  相似文献   

5.
The evolution of marine neotropical shallow water species is expected to have been greatly affected by physical events related to the emergence of the Central American Isthmus. The anomuran crab Megalobrachium, a strictly neotropical porcellanid genus, consists of four species in the West Atlantic (WA) and nine in the East Pacific (EP). Dispersal is limited to a relatively short planktonic phase, which lasts approximately two weeks. We obtained DNA sequences of three mitochondrial and two nuclear genes of all but one species of Megalobrachium to construct a time‐calibrated phylogeny of the genus and its historical phylogeography, based on the reconstruction of ancestral areas. The topology of the phylogenetic trees of Megalobrachium produced by Bayesian Inference (BI) and Maximum Likelihood (ML) were virtually congruent. The genus is monophyletic with respect to other porcellanids. Ancestral area reconstruction indicates that it arose in the eastern Pacific 18 million years ago and diversified into at least 13 species that are currently formally recognized and three additional species indicated by our data. Most morphological variation appears to have followed phylogenetic differentiation, though some cryptic speciation has also occurred. Four geminate clades in this genus implicate the gradual emergence of the Central American Isthmus in this diversification, but events preceding the final separation of the oceans as well as within‐ocean events after the cessation of water connections were also important.  相似文献   

6.
Small-eared shrews of the genus Cryptotis (Mammalia: Eulipotyphla: Soricidae) are widespread in the northern Neotropics. Systematic studies of these shrews over the past two decades have revealed previously undocumented morphological and species diversity, resulting in a quadrupling of the number of recognized species. Unfortunately, a small proportion of the species in the genus have been included in molecular phylogenetic studies, and evolutionary relationships within the genus are incompletely known. Traditionally, species have been assigned to four or five morphologically defined ‘species groups’, but tests of the monophyly of some of these groups show weak support and relationships amongst species groups remain somewhat speculative. The largest species group is the C. mexicanus group inhabiting Mexico and northern Central America. We studied sequences from mitochondrial cytochrome-b and 16S genes, as well as nuclear ApoB and BRCA1 genes from 22 species of Cryptotis, including 15 species in the C. mexicanus group. Our combined analysis shows that the C. goldmani subgroup is very weakly supported as monophyletic; however, the C. mexicanus group as a whole is not monophyletic. Our molecular phylogenetic analyses confirm the distinctiveness of two newly described species (C. celaque and C. mccarthyi) from isolated highlands of western Honduras and illustrate their relationship with other species formerly considered part of a widespread C. goodwini.  相似文献   

7.
In spite of several classification attempts among taxa of the genus Lepus, phylogenetic relationships still remain poorly understood. Here, we present molecular genetic evidence that may resolve some of the current incongruities in the phylogeny of the leporids. The complete mitochondrial cytb, 12S genes, and parts of ND4 and control region fragments were sequenced to examine phylogenetic relationships among Chinese hare taxa and other leporids throughout the World using maximum parsimony, maximum likelihood, and Bayesian phylogenetic reconstruction approaches. Using reconstructed phylogenies, we observed that the Chinese hare is not a single monophyletic group as originally thought. Instead, the data infers that the genus Lepus is monophyletic with three unique species groups: North American, Eurasian, and African. Ancestral area analysis indicated that ancestral Lepus arose in North America and then dispersed into Eurasia via the Bering Land Bridge eventually extending to Africa. Brooks Parsimony analysis showed that dispersal events followed by subsequent speciation have occurred in other geographic areas as well and resulted in the rapid radiation and speciation of Lepus. A Bayesian relaxed molecular clock approach based on the continuous autocorrelation of evolutionary rates along branches estimated the divergence time between the three major groups within Lepus. The genus appears to have arisen approximately 10.76 MYA (+/-0.86 MYA), with most speciation events occurring during the Pliocene epoch (5.65+/-1.15 MYA approximately 1.12 +/- 0.47 MYA).  相似文献   

8.
9.
Low copy number nuclear genes have been found to be useful for phylogenetic reconstruction at different taxonomic levels. This study investigated the utility of a single copy gene, cinnamoyl CoA reductase (CCR), for resolving phylogenetic relationships at the sectional level within Eucalyptus. The monophyly of sections Exsertaria and Latoangulatae was explored, using section Maidenaria as an outgroup, and the impact of intragenic recombination on phylogenetic reconstruction examined. Phylogenetic analysis did not resolve monophyletic groups. Latoangulatae and Maidenaria were polyphyletic or paraphyletic. Exsertaria species formed a clade but included a single Latoangulatae species (E. major). Recombination analysis identified two intragenic recombination events that involved species from different sections, which have probably been facilitated by inter-sectional hybridisation. One of the events most likely occurred prior to speciation, with several Latoangulatae species having the recombinant allele. The other event may have occurred after speciation, since only one of two E. globulus samples possessed the recombinant allele. This is the first detailed report of intragenic recombination in both CCR and Eucalyptus, and between species of different sections of a plant genus. The occurrence of intragenic recombination may explain the anomalous positions of some species within the phylogenetic tree, and indicates that phylogenetic analysis of Eucalyptus using nuclear genes will be problematic unless recombination is taken into account.  相似文献   

10.
The relationship between Litsea and related genera is currently unclear. Previous molecular studies on these taxa using cpDNA and nrITS were unable to produce well-resolved phylogenetic trees. In this study, we explored the potential of the rpb2 gene as a source of molecular information to better resolve the phylogenetic analysis. Although rpb2 was believed to be a single-copy gene, our cloning results showed that most species examined possessed several copies of these sequences. However, the genetic distance among copies from any one species was low, and these copies always formed monophyletic groups in our molecular trees. Our phylogenetic analyses of rpb2 data resulted in better resolved tree topologies compared to those based on cpDNA or nrITS data. Our results show that monophyly of the genus Litsea is supported only for section Litsea. As a genus, Litsea was shown to be polyphyletic. The genera Actinodaphne and Neolitsea were resolved as monophyletic groups in all analyses. They were also shown to be sisters and closer to the genus Lindera than to the genus Litsea. Our results also revealed that the genus Lindera is not a monophyletic group.  相似文献   

11.
Complete plastid genome (plastome) sequences and nuclear ribosomal DNA (nrDNA) regions have been proposed as candidates for the next generation of DNA barcodes for plant species discrimination. However, the efficacy of this approach still lacks comprehensive evaluation. We carried out a case study in the economically important but phylogenetically and taxonomically difficult genus Panax (Araliaceae). We generated a large data set of plastomes and nrDNA sequences from multiple accessions per species. Our data improved the phylogenetic resolution and levels of species discrimination in Panax, compared to any previous studies using standard DNA barcodes. This provides new insights into the speciation, lineage diversification and biogeography of the genus. However, both plastome and nrDNA failed to completely resolve the phylogenetic relationships in the Panax bipinnatifidus species complex, and only half of the species within it were recovered as monophyletic units. The results suggest that complete plastome and ribosomal DNA sequences can substantially increase species discriminatory power in plants, but they are not powerful enough to fully resolve phylogenetic relationships and discriminate all species, particularly in evolutionarily young and complex plant groups. To gain further resolving power for closely related species, the addition of substantial numbers of nuclear markers is likely to be required.  相似文献   

12.
The lizard genus Kentropyx (Squamata: Teiidae) comprises nine species, which have been placed in three species groups (calcarata group, associated to forests ecosystems; paulensis and striata groups, associated to open ecosystems). We reconstructed phylogenetic relationships of Kentropyx based on morphology (pholidosis and coloration) and mitochondrial DNA data (12S and 16S), using maximum parsimony and Bayesian methods, and evaluated biogeographic scenarios based on ancestral areas analyses and molecular dating by Bayesian methods. Additionally, we tested the life‐history hypothesis that species of Kentropyx inhabiting open ecosystems (under seasonal environments) produce larger clutches with smaller eggs and that species inhabiting forest ecosystems (under aseasonal conditions) produce clutches with fewer and larger eggs, using Stearns’ phylogenetic‐subtraction method and canonical phylogenetic ordination to take in to account the effects of phylogeny. Our results showed that Kentropyx comprises three monophyletic groups, with K. striata occupying a basal position in opposition to previous suggestions of relationships. Additionally, Bayesian analysis of divergence time showed that Kentropyx may have originated at the Tertiary (Eocene/Oligocene) and the ‘Pleistocene Refuge Hypothesis’ may not explain the species diversification. Based on ancestral reconstruction and molecular dating, we argued that a savanna ancestor is more likely and that historical events during the Tertiary of South America promoted the differentiation of the genus, coupled with recent Quaternary events that were important as dispersion routes and for the diversification at populational levels. Clutch size and egg volume were not significantly different between major clades and ecosystems of occurrence, even accounting for the phylogenetic effects. Finally, we argue that phylogenetic constraints and phylogenetic inertia might be playing essential roles in life history evolution of Kentropyx.  相似文献   

13.
The genetic structure of populations of closely related, sympatric species may hold the signature of the geographical mode of the speciation process. In fully allopatric speciation, it is expected that genetic differentiation between species is homogeneously distributed across the genome. In nonallopatric speciation, the genomes may remain undifferentiated to a large extent. In this article, we analyzed the genetic structure of five sympatric species from the plant genus Heliotropium in the Atacama Desert. We used amplified fragment length polymorphisms (AFLPs) to characterize the genetic structure of these species and evaluate their genetic differentiation as well as the number of loci subject to positive selection using divergence outlier analysis (DOA). The five species form distinguishable groups in the genetic space, with zones of overlap, indicating that they are possibly not completely isolated. Among‐species differentiation accounts for 35% of the total genetic differentiation (FST = 0.35), and FST between species pairs is positively correlated with phylogenetic distance. DOA suggests that few loci are subject to positive selection, which is in line with a scenario of nonallopatric speciation. These results support the idea that sympatric species of Heliotropium sect. Cochranea are under an ongoing speciation process, characterized by a fluctuation of population ranges in response to pulses of arid and humid periods during Quaternary times.  相似文献   

14.
Data on the spermatozoa of Branchiobdellida were taken from the published literature: sperm models of 25 species belonging to 13 different branchiobdellidan genera have been compared with the aim of supplying further evidences for a phylogenetic analysis of the group. The species considered were representative of all traditional branchiobdellidan families, excluding the monotypic Caridinophilidae. Branchiobdellidan spermatozoa are complex cells, thus it was possible to analyse the variation of 20 characters within the group. A parsimony analysis has yielded nine minimal trees, eight of which are very similar to one another. The main conclusions of the phylogenetic analysis are: (a) the monophyly of the taxon Branchiobdellida is confirmed; (b) the most speciose branchiobdellidan genus, Cambarincola is polyphyletic; (c) none of the traditional ‘families’ are supported; (d) the genus Branchiobdella is monophyletic, but the position of one species, B. kobayashi, albeit basal to the whole genus, is not resolved; (e) the other two genera analysed for which more than one species was available, Pterodrilus and Xironogiton, are monophyletic; (f) there seems to be a ‘trend’ in the whole group towards an increase of acrosome length. Our results partly parallel those obtained by Gelder and Siddall (2000) with a combined analysis of molecular and somatic characters, and point to the need for a comprehensive revision of the Branchiobdellida based on a combination of molecular, somatic and spermatological data sets.  相似文献   

15.
16.
Aim We use the Stramonita haemastoma species complex (Muricidae) to investigate the geographic scale of speciation in a marine snail with a long pelagic larval duration (PLD) of 2–3 months and, consequently, high dispersal potential. We aim to: (1) delimit species within Stramonita, (2) discover the phylogenetic relationship among them, (3) map their distributions, and (4) infer the age and likely cause of speciation events. Location Tropical intertidal of the Atlantic and eastern Pacific Oceans. Methods We use one nuclear and two mitochondrial genes to construct a molecular phylogeny of the S. haemastoma species complex. We first test the monophyly of the genus and of the species complex, and then use statistical methods to delimit species within the complex. We incorporate information from museum collections and the literature to map distributions and to look for diagnostic morphological traits. We use fossils to date our phylogeny. Results The genus Stramonita is monophyletic and restricted to the tropical and warm‐temperate Atlantic and eastern Pacific oceans. The genus is composed of Stramonita delessertiana and six members of the S. haemastoma complex: S. haemastoma, Stramonita rustica, Stramonita floridana, Stramonita canaliculata, Stramonita biserialis and Stramonita brasiliensis (new species described herein). These species are supported by reciprocal monophyly in mitochondrial gene trees, together with independent evidence from morphology, distribution and the nuclear gene. The species are almost entirely allopatric, with only three instances of sympatry. Two species have unusually wide distributions, consistent with their long PLD; one of these is amphi‐Atlantic. Main conclusions Despite the long PLD of Stramonita, speciation has occurred within the Atlantic, both in response to barriers operating at the largest geographical scale (the width of Atlantic, but not the Amazon barrier) and at a smaller scale within the western Atlantic.  相似文献   

17.
Abstract Phylogenetic relationships of Pamphagidae were examined using cytochrome oxidase subunit II (COII) mtDNA sequences (684 bp). Twenty‐seven species of Acridoidea from 20 genera were sequenced to obtain mtDNA data, along with four species from the GenBank nucleotide database. The purpose of this study was analyzing the phylogenetic relationships among subfamilies within Pamphagidae and interpreting the phylogenetic position of this family within the Acridoidea superfamily. Phylogenetic trees were reconstructed using neighbor‐joining (NJ), maximum parsimony (MP) and Bayesian inference (BI) methods. The 684 bp analyzed fragment included 126 parsimony informative sites. Sequences diverged 1.0%–11.1% between genera within subfamilies, and 8.8%–12.3% between subfamilies. Amino acid sequence diverged 0–6.1% between genera within subfamilies, and 0.4%–7.5% between subfamilies. Our phylogenetic trees revealed the monophyly of Pamphagidae and three distinct major groups within this family. Moreover, several well supported and stable clades were found in Pamphagidae. The global clustering results were similar to that obtained through classical morphological classification: Prionotropisinae, Thrinchinae and Pamphaginae were monophyletic groups. However, the current genus Filchnerella (Prionotropisinae) was not a monophyletic group and the genus Asiotmethis (Prionotropisinae) was a sister group of the genus Thrinchus (Thrinchinae). Further molecular and morphological studies are required to clarify the phylogenetic relationships of the genera Filchnerella and Asiotmethis.  相似文献   

18.
The neotropical cichlid genus Gymnogeophagus is distributed in the Río de la Plata basin and in Dos Patos and Merín coastal lagoons on the border between Uruguay and southern Brazil. A phylogeographic approach based on mitochondrial cytochrome b analysis was performed to assess the patterns and processes of differentiation in this taxon. Gymnogeophagus gymnogenys showed high haplotype diversity (H = 0.992) and corrected mtDNA genetic distances ranged from 0 to 5.3%. Our analyses yielded robust support for the existence of four monophyletic groups within G. gymnogenys from the analyzed basins. No correlation between the aforementioned clades and geographic structure was found, since individuals belonging to different phylogenetic clades inhabit the same locality. The phylogeographic approach presented here showed that these four phylogroups (1, 2, 3 and 4) were sister groups. Our present findings would corroborate that G. gymnogenys could be integrated by different phylogenetic lineages, showing an explosive differentiation pattern and confirming the hypothesis that this taxon constitutes a species complex.  相似文献   

19.
The study of island fauna has greatly informed our understanding of the evolution of diversity. We here examine the phylogenetics, biogeography, and diversification of the damselfly genera Nesobasis and Melanesobasis, endemic to the Fiji Islands, to explore mechanisms of speciation in these highly speciose groups. Using mitochondrial (COI, 12S) and nuclear (ITS) replicons, we recovered Garli ‐part maximum likelihood and Mrbayes Bayesian phylogenetic hypotheses for 26 species of Nesobasis and eight species/subspecies of Melanesobasis. Biogeographical patterns were explored using Lagrange and Bayes ‐Lagrange and interpreted through beast relaxed clock dating analyses. We found that Nesobasis and Melanesobasis have radiated throughout Fiji, but are not sister groups. For Nesobasis, while the two largest islands of the archipelago—Viti Levu and Vanua Levu—currently host two distinct species assemblages, they do not represent phylogenetic clades; of the three major groupings each contains some Viti Levu and some Vanua Levu species, suggesting independent colonization events across the archipelago. Our Beast analysis suggests a high level of species diversification around 2–6 Ma. Our ancestral area reconstruction (Rasp ‐Lagrange ) suggests that both dispersal and vicariance events contributed to the evolution of diversity. We thus conclude that the evolutionary history of Nesobasis and Melanesobasis is complex; while inter‐island dispersal followed by speciation (i.e., peripatry) has contributed to diversity, speciation within islands appears to have taken place a number of times as well. This speciation has taken place relatively recently and appears to be driven more by reproductive isolation than by ecological differentiation: while species in Nesobasis are morphologically distinct from one another, they are ecologically very similar, and currently are found to exist sympatrically throughout the islands on which they are distributed. We consider the potential for allopatric speciation within islands, as well as the influence of parasitic endosymbionts, to explain the high rates of speciation in these damselflies.  相似文献   

20.
A phylogenetic analysis of the Neotropical members of genus Lepidocyrtus was conducted to assess the pattern of speciation in Puerto Rico while testing the phylogenetic information content of two characters used to diagnose subgenera. The analysis included twenty‐two species of Lepidocyrtus from the Neotropical Region for which information on the tergal chaetotaxy of the trunk was available, two species of Holarctic Lepidocyrtus, three species of Pseudosinella, two species of Metasinella used in outgroup analysis and ninety‐two informative characters. The results do not support a monophyletic origin for the Puerto Rican Lepidocyrtus, suggesting the current fauna originated through repeated invasions from abroad. Three instances of endemic speciation can be inferred from the cladograms. The geographical distribution and diversity of colour forms suggest that L. caprilesi and L. paracaprilesi speciated sympatrically, whereas vicariance can explain speciation for L. lepargus and L. maldonadoi. The mode of speciation for L. dispar and L. biphasis remains unclear because the proportion of morphological variation between these species does not fit the proportions expected under the sympatric model suggested by their geographical distribution. The results support an early conclusion regarding appendicular scale distribution as a poor indicator of phylogenetic relationships. Taxa defined using this character are likely to be polyphyletic. The results disagree with a previous study in documenting low levels of homoplasy for the dental tubercle, implying that this character contains phylogenetic information useful in defining subgenera. However, the presence or absence of a dental tubercle is not diagnostic and should be used in combination with other characters. Comparisons of levels of homoplasy in Neotropical and Hawaiian Lepidocyrtus suggest that the relative position of two setae on the second abdominal tergum may be a better subgeneric character than other characters currently in use.  相似文献   

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