Phylogeography of the greenside darter complex, Etheostoma blennioides (Teleostomi: Percidae): a wide-ranging polytypic taxon

The greenside darter, Etheostoma blennioides (Teleostomi: Percidae), is a wide-ranging polytypic taxon that occurs throughout eastern North America. A previous morphological study recognized four subspecies (blennioides, newmanii, gutselli, and pholidotum), several morphological races, and three zones of morphological intergradation. We generated complete cytochrome b (1140bp) sequence data for 51 individuals from across the range of the greenside darter inclusive of all of the currently recognized taxa to assess genetic variation and taxonomic boundaries. Both maximum parsimony and mixed model Bayesian analyses resulted in two strongly supported deeply divergent clades including (1) a Tennessee River drainage clade, and (2) an Ohio River and Great Lakes basins, Interior Highlands, and Atlantic slope clade. Etheostoma blennius, a closely related congener, nested within the Tennessee River clade of E. blennioides, rendering the complex paraphyletic. Test of alternative topologies failed to support the current taxonomic designations. The inclusion of nuclear sequence data from intron 1 of the S7 ribosomal protein (523bp) from a subset of the populations was included to independently test whether the currently recognized taxa conform to distinct evolutionary lineages and also to clarify potential issues associated with ancestral hybridization. Although the nuclear data was less variable than the mitochondrial data, the monophyly of several of the subspecies could not be rejected.     

Molecular phylogeny of the snubnose darters, subgenus Ulocentra (genus Etheostoma, family Percidae)

Snubnose darters comprise one of the largest subgenera of the percid genus Etheostoma. Many species are described based on differences in male breeding coloration. Few morphological synapomorphies have been proposed for the subgenus and their relatives, making it difficult to delineate monophyletic clades. The phylogenetic relationships of the 20 snubnose darter species of the subgenus Ulocentra and 11 members of its proposed sister subgenus Etheostoma were investigated with partial mitochondrial DNA sequences including 1033 bp encompassing the entire mitochondrial control region, the tRNA-Phe gene, and part of the 12S rRNA gene. Two hypotheses on the relationship and monophyly of the two subgenera were evaluated. Both maximum-parsimony and neighbor-joining analyses supported monophyly of the subgenus Ulocentra and resolved some species-level relationships. The banded darter, E. zonale, and its sister taxon, E. lynceum, were not closely related to the snubnose darters and appear to be diverged from the other members of the subgenus Etheostoma, fitting their former distinction as the recognized subgenus Nanostoma. The sister group to Ulocentra appears to be a restricted species assemblage within the subgenus Etheostoma containing E. blennioides, E. rupestre, E. blennius, and the E. thalassinum species group. The placement of the harlequin darter, E. histrio, is problematic, and it may represent a basal member of Ulocentra or of the restricted subgenus Etheostoma. Despite recent estimates of divergence times between nominal Ulocentra taxa, each species exhibits its own unique set of mtDNA haplotypes, providing no direct evidence for current genetic exchange between species. The nominal taxa of snubnose darters thus appear to be evolving independently from each other and therefore constitute valid species under the Phylogenetic Species Concept.     

The effects of river barriers and range expansion of the population genetic structure and stability in Greenside Darter (Etheostoma blennioides) populations

The genetic structure of a stream-dwelling fish, the Greenside Darter, Etheostoma blennioides, is described from variation at nine microsatellite loci in 26 populations in the northern-most portions of the species’ range in southern Ontario, Canada in two sampling years. We found relatively high levels of genetic structure at the among- and within-watershed scales, with some watersheds and populations exhibiting very high divergence. The Ausable River populations were especially isolated, containing distinct populations of potential conservation concern. Temporal replicates at selected localities showed evidence of substantial temporal variation in genetic structure, perhaps resulting from movement among sites. We found strong evidence for an effect of river barriers (dams and weirs) on dispersal measured by genotype assignment techniques. However, we found no bias in upstream vs downstream dispersal. Significant isolation-by-distance relationships in both sample years indicate that river distance is an important factor regulating gene flow in these watersheds. The Canadian Greenside Darter populations are expanding their range into more northerly watersheds, but also show substantial within-watershed genetic structure despite substantial dispersal.     

Molecular phylogenetic relationship of snow finch complex (genera Montifringilla, Pyrgilauda, and Onychostruthus) from the Tibetan plateau

The snow finch complex (Montifringilla, Pyrgilauda, and Onychostruthus) has its center of distribution on the Tibetan plateau, with six out of seven species in the genera occurring there. Phylogenetic relationships among these six species of three genera have been studied based on DNA sequence data obtained from the mitochondrial cytochrome b gene and the nuclear myoglobin gene. The results support monophyly of the snow finch complex group and three major evolutionary lineages are recognized. The first clade consists of ruficollis, blanfordi, and davidiana. These three taxa are sometimes placed in their own genus, Pyrgilauda, and the DNA data supports this. The three taxa nivalis, henrici, and adamsi have traditionally been placed in the genus Montifringilla, and they group together strongly in the present analysis. The results further suggest that nivalis and adamsi are more closely related to each other than are nivalis and henrici, despite that the latter two are often regarded as conspecific. The third distinct lineage within the snow finch complex consists of taczanowskii, which has been placed its own genus, Onychostruthus. This taxon has a basal position in the phylogenetic tree and is sister to all other snow finches. We estimated that taczanowskii split from the other taxa between 2 and 2.5 mya, i.e., about the time for the most recent uplift of the Tibetan plateau, "the Tibet movement", 3.6-1.7 mya. Cladogenesis within the Montifringilla and Pyrgilauda clades seems to be contemporary with the second phase of "Tibet movement" at 2.5 mya and the third phase at 1.7 mya and "Kunhuang movement" in 1.5-0.6 mya. The dramatic climatic and ecological changes following from the uplift of the Tibetan plateau, together with the cyclic contraction and expansion of suitable habitats during the Pleistocene, are probably the most important factors for the cladogenesis in snow finch complex.     

Systematics of the subgenus Oligocephalus (Teleostei: Percidae: Etheostoma) with complete subgeneric sampling of the genus Etheostoma

The genus Etheostoma is the most diverse clade of freshwater fishes in North America. While studies have been performed with complete sampling of a single subgenus, none have included representatives of all remaining subgenera. The subgenus Oligocephalus is the largest, consisting of 25-27 species in four species groups, and its monophyly has never been clearly demonstrated. The monophyly of this subgenus and its constituent groups was tested using parsimony and Bayesian analyses of ND2 (mtDNA) and the first intron of S7 (nDNA) with complete species sampling from Oligocephalus and complete subgeneric sampling from Etheostoma. Although the subgenus Oligocephalus was not recovered as a monophyletic group in any analyses, monophyletic E. whipplei, Southwestern Darter, and E. spectabile (in part) species groups were recovered in all analyses. All analyses agree that E. okaloosae and both subspecies of E. hopkinsi are not closely related to other members of the subgenus Oligocephalus. E. exile is, however, presenting the strongest evidence yet that recognition of the subgenus Boleichthys is unwarranted.     

Global mitochondrial DNA phylogeography and biogeographic history of the antitropically and longitudinally disjunct marine bryozoan Membranipora membranacea L. (Cheilostomata): another cryptic marine sibling species complex?

The origin of disjunct distributions in high dispersal marine taxa remains an important evolutionary question as it relates to the formation of new species in an environment where barriers to gene flow are not always obvious. To reconstruct the relationships and phylogeographic history of the antitropically and longitudinally disjunct bryozoan Membranipora membranacea populations were surveyed with mtDNA cytochrome oxidase 1 (COI) sequences across its cosmopolitan range. Maximum parsimony, maximum likelihood and Bayesian genealogies revealed three deep clades in the North Pacific and one monophyletic clade each in the southeast Pacific (Chile), southwest Pacific (Australia/New Zealand), North Atlantic and southeast Atlantic (South Africa). Human-mediated dispersal has not impacted M. membranacea’s large-scale genetic structure. M. membranacea did not participate in the trans-arctic interchange. Episodic long-distance dispersal, combined with climatic vicariance can explain the disjunct distribution. Dispersal led southward across the tropics perhaps 13 mya in the East Pacific and again northwards perhaps 6 mya in the Eastern Atlantic to colonize the North Atlantic from the south, and along the West Wind Drift to colonize Australia. The clades differentiated over evolutionary time in their respective ocean region, potentially forming a sibling species complex. The taxonomic status of the clades is discussed.     

Rare and enigmatic genera (Dunnia, Schizocolea, Colletoecema), sisters to species-rich clades: phylogeny and aspects of conservation biology in the coffee family

Despite extensive efforts, parts of the phylogeny of the angiosperm family Rubiaceae has not been resolved and consequently, character evolution, ancestral areas and divergence times of major radiations are difficult to estimate. Here, phylogenetic analyses of 149 taxa and five plastid gene regions show that three enigmatic genera are sisters to considerably species rich clades. The rare and endangered species Dunnia, endemic to southern Guangdong, China, is sister to a large clade in the Spermacoceae alliance; the rarely collected Schizocolea from western tropical Africa is sister to the Psychotrieae alliance; and Colletoecema from central tropical Africa is sister to remaining Rubioideae. The morphology of these taxa has been considered "puzzling". In combination with further morphological studies, our results may help understanding the apparently confusing traits of these plants. Phylogenetic, morphological, and geographical isolation of Dunnia, Schizocolea and Colletocema may indicate high genetic diversity. They are lone representatives of unique lineages and if extinct, the loss would not only mean loss of genetic diversity of a single species but of an entire lineage.     

Molecular systematics,hybridization, and phylogeography of the Bufo americanus complex in Eastern North America

We reconstruct phylogenetic relationships among a well-studied group of toads and find relationships that differ greatly from the current taxonomic understanding. We use mitochondrial sequences encoding ND1, tRNA(Leu(UUR)), and part of 16S to infer relationships among members of the Bufo americanus complex. Focusing on the four taxa that historically have been most problematic due to morphological similarity and hybridization in sympatry, we sample 150 individuals from multiple populations across each species' geographic range. Our evidence conflicts with previous taxonomic hypotheses that were based on ability to hybridize, geographic distribution, and call variation. First, sequences from B. fowleri do not comprise the sister clade to sequences of B. woodhousii; therefore the previous classifications of B. fowleri as sister species to, or eastern subspecies of, B. woodhousii are both called into question. Second, sequences from B. americanus are more closely related to those of B. woodhousii than to those of B. terrestris, indicating that similar advertisement call characteristics evolved independently. Third, sequences of B. fowleri are paraphyletic, with sequences of B. terrestris embedded within. Lastly, sequences from B. fowleri cluster into three distinct mitochondrial clades, with some divergences corresponding to greater than 2mya. These clades are somewhat geographically structured, suggesting divergence in allopatry during the Pleistocene. These mitochondrial divergences are not accompanied by known phenotypic differences, however, suggesting either evolutionary stasis in morphology and behavior, cryptic phenotypic evolution, or that hybridization in secondary contact has homogenized phenotypic differences that may have arisen in allopatry.     

Impacts of a tertiary treated municipal wastewater effluent on the carbon and nitrogen stable isotope signatures of two darter species (Etheostoma blennioides and E. caeruleum) in a small receiving environment

This study contrasted the influence of tertiary treated municipal wastewater effluent (MWWE) exposure on the abundance, food selection (stomach contents), and carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope signatures of Rainbow Darter (Etheostoma caeruleum) and Greenside Darter (Etheostoma blennioides) in a small receiving stream in southern Ontario, Canada. Despite tertiary treatment resulting in relatively high effluent quality, there is continued concern for environmental degradation downstream of the effluent outfall because of the relatively small size of the receiving environment and recent studies that have indicated changes occurring in relative fish abundance and stable isotope signatures. In July and August of 2009 fish and benthic invertebrate communities were examined along with analysis of δ¹³C and δ¹⁵N of the most common species to determine the effects of effluent exposure on the food web. Rainbow Darter increased in abundance and their δ¹⁵N values were enriched immediately downstream of the effluent outfall throughout the summer (July and August). In contrast, while δ¹⁵N of Greenside Darter followed a similar pattern in July, they were not enriched in August. The benthic community was changed immediately downstream of the outfall and the δ¹⁵N of invertebrates was enriched, similar to that observed in Rainbow Darter. Stomach contents of the two darter species diverged the most in the summer possibly explaining some of the changes in δ¹³C and δ¹⁵N among sites. It is possible that Greenside Darter fed on less enriched food downstream of the outfall, or fed outside of the effluent plume during the summer. Rainbow Darter may be able to exploit the changes in habitat and prey composition, resulting in differences in relative abundance of darters immediately downstream of the effluent outfall.     

Apparent 'sympatric' speciation in ecologically similar herbivorous beetles facilitated by multiple colonizations of an island

Coexistence of recently diverged and ecologically similar sister species in complete sympatry represents a particularly compelling case for sympatric speciation. This study investigates the possible sympatric origin of two coexisting bark beetle taxa that utilize the same host plant on the island of La Palma in the Canary Islands. Aphanarthrum subglabrum and Aphanarthrum glabrum ssp. nudum breed inside dead twigs of Euphorbia lamarckii plants and are closely related to the allopatric A. glabrum ssp. glabrum in Tenerife, El Hierro and La Gomera. We tested the various speciation hypotheses in a genealogical context, using mitochondrial gene fragments from Cytochrome Oxidase I and 16S, and nuclear gene fragments from Enolase, Elongation Factor 1alpha and Histone H3. Phylogenetic analyses of the combined nuclear DNA data strongly supported a sister relationship between two sympatric and reproductively isolated taxa in La Palma. However, network analyses of subdivided nonrecombinant segments of the Enolase locus indicated a closer relationship between the two allopatric A. glabrum subspecies, suggesting multiple colonizations of this island. A bimodal distribution of mtDNA haplotypes in La Palma further documented the independent colonization of this island, with asymmetric introgression of mtDNA between two lineages. Consequently, the sympatric origin of the La Palma species is concluded to have involved allopatric phases before the parallel colonization of this island and subsequent introgression at some loci. The clear genetic and morphological evidence for reproductive isolation between these species suggests that the sympatric completion of divergence was either due to initial genetic incompatibility, morphological character displacement in male genitalia, or a combination of these factors.     

Diversity of North American map and sawback turtles (Testudines: Emydidae: Graptemys)

Map turtles of the genus Graptemys are native to North America, where a high degree of drainage endemism is believed to have shaped current diversity. With 14 species and one additional subspecies, Graptemys represents the most diverse genus in the family Emydidae. While some Graptemys species are characterized by pronounced morphological differences, previous phylogenetic analyses have failed yet to confirm significant levels of genetic divergence for many taxa. As a consequence, it has been debated whether Graptemys is taxonomically inflated or whether the low genetic divergence observed reflects recent radiations or ancient hybridization. In this study, we analysed three mtDNA blocks (3228 bp) as well as 12 nuclear loci (7844 bp) of 89 specimens covering all species and subspecies of Graptemys. Our analyses of the concatenated mtDNA sequences reveal that the widespread G. geographica constitutes the sister taxon of all other Graptemys species. These correspond to two clades, one comprised of all broad‐headed Graptemys species and another clade containing the narrow‐headed species. Most species of the broad‐headed clade are reciprocally monophyletic, except for G. gibbonsi and G. pearlensis, which are not differentiated. By contrast, in the narrow‐headed clade, many currently recognized species are not monophyletic and divergence is significantly less pronounced. Haplotype networks of phased nuclear loci show low genetic divergence among taxa and many shared haplotypes. Principal component analyses using coded phased nuclear DNA sequences revealed eight distinct clusters within Graptemys that partially conflict with the terminal mtDNA clades. This might be explained by male‐mediated gene flow across drainage basins and female philopatry within drainage basins. Our results support that Graptemys is taxonomically oversplit and needs to be revised.     

A molecular phylogeny for the South African limbless lizard taxa of the subfamily Acontinae (Sauria: Scincidae) with special emphasis on relationships within Acontias

In the present study, relationships among three genera Acontias, Acontophiops, and Typhlosaurus, that comprise the South African limbless lizard subfamily Acontinae, were assessed with partial sequences of the 16S rRNA mitochondrial DNA gene. In addition, relationships within Acontias were further investigated using sequence data from the cytochrome oxidase I gene (COI). Maximum likelihood and maximum parsimony analyses of the 16S rRNA mtDNA data revealed that within this subfamily, Typhlosaurus is basal while Acontophiops and Acontias are sister taxa. Based on the 16S rRNA mtDNA data, the relationships within Acontias placed A. meleagris orientalis as the sister taxon of A. percivali tasmani, with A. m. orientalis lineacauda morph and A. m. meleagrus being the sister taxa to this group. The small-bodied skinks A. lineatus lineatus and A. l. tristis formed a monophyletic group, with the medium-bodied species A. gracilicauda gracilicauda being their sister taxon. Analyses of the COI gene for Acontias place A. m. orientalis as the sister taxon of A. p. tasmani with both A. meleagris meleagris and A. m. orientalis lineacauda being distinct. In contrast to the 16S rRNA mtDNA data, the COI data placed A. g. gracilicauda as the sister taxon to these medium-bodied species; while the subspecies status of the small-bodied taxa A. l. lineatus and A. l. tristis is reaffirmed. Combined analysis of both gene fragments for Acontias taxa recovered the same clades as found using only COI data. Systematic affinities in Acontias are discussed. These results indicate that Acontias is more species rich than previously thought.     

Sorting out the Snakebirds: The species status,phylogeny, and biogeography of the Darters (Aves: Anhingidae)

Although the avian family Anhingidae is unequivocally monophyletic, the number and relationships of the component species within the single genus (Anhinga) have long remained unclear. Here, we use extensive mitochondrial and nuclear DNA sequence data (8,878 bp) to show that four species should be recognized. Our fully resolved and well‐supported tree shows that the American Anhinga (Anhinga anhinga) is sister to the three Old World species, with the Oriental (A. melanogaster) and African (A. rufa) Darters sister within the Old World clade, which also includes the Australian Darter (A. novaehollandiae). We estimate that the divergence between the New World and Old World branches occurred 19–22 mya, with the Australian Darter separating from its Old World congeners 14–16 mya and the Oriental and African species splitting ~10 mya. The genus is yet another example of osteological conservatism in the Suliformes, which is comparable to that shown by the cormorants and shags. Nevertheless, the relationships we infer are congruent with recent plumage studies and are biogeographically plausible. We suggest that further investigation of the variation within the African and Australian Darters would be of interest.     

Evolutionarily independent genes and genomes and insights on genetic structure, evolution and conservation of the collis group of darters

Comparing variation across evolutionarily independent characters, notably nuclear and mitochondrial genes, yields a more robust estimate of diversification than is generally recovered from individual characters. Patterns of variation across multiple molecular markers from the mitochondrial ( 16SrRNA , cytochrome b ) and nuclear ( ldhA6 and aldB ) genomes were examined from six populations of Etheostoma collis and two populations of Etheostoma saludae , species aligned in the collis groups. Phylogenetic analyses revealed that sequence variation among individuals from the Roanoke, Tar and Neuse Rivers and the Catawba and Pee Dee Rivers, respectively, form highly supported, deeply divergent clades. Relationships of alleles sampled from Saluda River E. saludae and Cape Fear River E. collis to these lineages are unresolved, but all groups are reciprocally monophyletic for both nuclear and mtDNA loci. Phylogenetic analyses suggest that historical factors have had a strong influence on the distribution of genetic variation among populations. Genetic variation within the collis group is consistent with all previously proposed taxonomic hypotheses for the collis group, providing no taxonomic insights. From a conservation standpoint, each population of the collis group is an ESU, thereby warranting a drainage-specific management strategy.     

The youngest split in sympatric schizothoracine fish (Cyprinidae) is shaped by ecological adaptations in a Tibetan Plateau glacier lake

Although new empirical evidence shows that sympatric speciation has occurred in some species, there are few indisputable model organisms for this process of speciation. The two subspecies ( Gymnocypris eckloni eckloni and G . e . scoliostomus ) of the schizothoracine Gymnocypris fish species complex from a small glacier lake in the Tibetan Plateau, Lake Sunmcuo, fit several of the key characteristics of the sympatric speciation model. We used combined mitochondrial control region sequences and the cytochrome b gene (1894 bp) to address the phylogenetics and population genetics of 232 specimens of G . e . eckloni and G . e . scoliostomus , as well as all of its closely related sister species. We found that: (i) a total of four old lineages were uncovered in the widespread G . e . eckloni , of which only one was shown to be shared with all G . e . scoliostomus individuals and (ii) the new subspecies ( G . e . scoliostomus ) evolved in Lake Sunmcuo from the ancestral G . e . eckloni population within approximately 0.057 Ma. These two taxa of the species complex are morphologically distinct, and reproductive isolation is further suggested. Ecological disruptive selection based on morphological traits (e.g. mouth cleft characters) and food utilization may be a mechanism of incipient speciation of two sympatric populations within Lake Sunmcuo. This study provides the first genetic evidence for sympatric speciation in the schizothoracine fish.     

The use of molecular and morphological characters to resolve the taxonomic identity of cryptic species: the case of Miniopterus manavi (Chiroptera, Miniopteridae)

Based on recent molecular phylogenetic studies, the Old World bat family Miniopteridae, composed of species in the genus Miniopterus , has been shown to contain complex paraphyletic species, many of which are cryptic based on convergent morphological characters. Herein we resolve the phylogenetic relationships and taxonomy of the species complex M . manavi on Madagascar and in the Comoro Archipelago, where these animals occur in different bioclimatic zones. First using mitochondrial cytochrome- b sequence data to define clades and then morphology to corroborate the molecular data, including comparisons to type specimens, we demonstrate that animals identified as this taxon are a minimum of three species: M . manavi sensu stricto occurs in at least the central portion of the Central Highlands; M . griveaudi has a broad distribution in lowland northern and central western Madagascar and the Comoros (Anjouan and Grande Comore), and M . aelleni sp. n. has been found in northern and western Madagascar and the Comoros (Anjouan). In each case, these three clades were genetically divergent and monophyletic and the taxa are diagnosable based on different external and craniodental characters. One aspect that helped to define the systematics of this group was isolation of DNA from one of the paratypes of M. manavi collected in 1896 and new topotypic material. Miniopterus manavi is most closely allied to a recently described species, M. petersoni . At several localities, M . griveaudi and M . aelleni have been found in strict sympatry, and together with M. manavi sensu stricto show considerable convergence in morphological characters, but are not immediate sister taxa. In defining and resolving the systematics of cryptic species, such as miniopterid bats, the process of defining clades with molecular tools, segregating the specimens accordingly, and identifying corroborative morphological characters has been notably efficient.     

Genetic Differentiation in Insular Lowland Rainforests: Insights from Historical Demographic Patterns in Philippine Birds

Phylogeographic studies of Philippine birds support that deep genetic structure occurs across continuous lowland forests within islands, despite the lack of obvious contemporary isolation mechanisms. To examine the pattern and tempo of diversification within Philippine island forests, and test if common mechanisms are responsible for observed differentiation, we focused on three co-distributed lowland bird taxa endemic to Greater Luzon and Greater Negros-Panay: Blue-headed Fantail (Rhipidura cyaniceps), White-browed Shama (Copsychus luzoniensis), and Lemon-throated Leaf-Warbler (Phylloscopus cebuensis). Each species has two described subspecies within Greater Luzon, and a single described subspecies on Greater Negros/Panay. Each of the three focal species showed a common geographic pattern of two monophyletic groups in Greater Luzon sister to a third monophyletic group found in Greater Negros-Panay, suggesting that common or similar biogeographic processes may have produced similar distributions. However, studied species displayed variable levels of mitochondrial DNA differentiation between clades, and genetic differentiation within Luzon was not necessarily concordant with described subspecies boundaries. Population genetic parameters for the three species suggested both rapid population growth from small numbers and geographic expansion across Luzon Island. Estimates of the timing of population expansion further supported that these events occurred asynchronously throughout the Pleistocene in the focal species, demanding particular explanations for differentiation, and support that co-distribution may be secondarily congruent.     

History repeated: recent and historical mitochondrial introgression between the current darter Etheostoma uniporum and rainbow darter Etheostoma caeruleum (Teleostei: Percidae)

Incongruence between recognized taxonomy and phylogenetic relationships between two species from a diverse clade (Percidae: Etheostomatinae) of stream fishes was found in a mitochondrial (mt) DNA gene tree. Two darters in subgenus Oligocephalus , Etheostoma uniporum current darter and Etheostoma caeruleum rainbow darter were sampled throughout their sympatric distribution in the Ozark Highlands of the central United States. Sequences from cytochrome (cyt) b and the first intron of the nuclear marker S7 were analysed separately using maximum parsimony and Bayesian methods. Cyt b recovered both species as polyphyletic; E. uniporum haplotypes were interspersed within E. caeruleum . However, both species were monophyletic and non-sister taxa based on S7. The cyt b gene tree pattern is caused by introgressive hybridization resulting in the mtDNA replacement of E. uniporum haplotypes by those of E. caeruleum . Some E. uniporum haplotypes are shared with geographically proximate E. caeruleum , and this is consistent with recent hybridization, while other E. uniporum haplotypes indicate historical sorting of introgressed lineages. The mechanism of introgression is likely asymmetric sneaking behaviour by male E. uniporum , a mating tactic observed in related species. MtDNA replacement may have occurred in E. uniporum due to drift fixation in a historically small female effective population. Additional evidence for darter hybridization will likely be discovered in future molecular genetic surveys of the nearly 200 species in eastern North America.     

Phylogeography of white-spotted Charr (Salvelinus leucomaenis) inferred from mitochondrial DNA sequences

The white-spotted charr (Salvelinus leucomaenis) is a coldwater-adapted fish distributed in far-eastern Asia. To assess phylogeographic patterns of this species over most of its range in the Japanese archipelago and Sakhalin Island, Russia, we examined nucleotide sequences of the mitochondrial DNA (mtDNA) cytochrome b region (557 bp) in 141 individuals from 50 populations. A total of 33 (5.5%) nucleotide positions were polymorphic and defined 29 haplotypes. Phylogenetic analysis assigned the observed haplotypes to four main clades, which were characterized by the idiosyncrasies and discontinuity of geographic distributions. The nested clade analyses revealed that the geographical distribution patterns of some haplotypes and clades were explained by historical event such as past fragmentation. Although substantial genetic differentiation was found among the four main clades, their geographic distributions overlapped extensively in several regions. Since white-spotted charr can potentially use both freshwater and marine environments, coexistence among different lineages can be attributed to secondary contact through range expansion by migratory individuals during multiple glacial periods after interglacial isolation. Finally, our data demonstrate that the current subspecies designation does not reflect the phylogeography of this species based on mtDNA analysis. Hierarchical analysis (AMOVA) also showed that genetic variation was far more pronounced within subspecies than among subspecies (i.e., among discrete regions). These results suggest that each population, rather than each subspecies, must be treated as an evolutionarily significant unit.     

Phylogenetic analyses of mtDNA sequences reveal three cryptic lineages in the widespread neotropical frog Leptodactylus fuscus (Schneider, 1799) (Anura, Leptodactylidae)

Leptodactylus fuscus is a neotropical frog ranging from Panamá to Argentina, to the east of the Andes mountains, and also inhabiting Margarita, Trinidad, and the Tobago islands. We performed phylogenetic analyses of 12S rRNA, 16S rRNA, tRNA-Leu, and ND1 mitochondrial (mt) DNA sequences from specimens collected across the geographic distribution of L. fuscus to examine two alternative hypotheses: (i) L. fuscus is a single, widely distributed species, or (ii) L. fuscus is a species complex. We tested statistically for geographic association and partitioning of genetic variation among mtDNA clades. The mtDNA data supported the hypothesis of several cryptic species within L. fuscus. Unlinked mtDNA and nuclear markers supported independently the distinctness of a 'northern' phylogenetic unit. In addition, the mtDNA data divided the southern populations into two clades that showed no sister relationship to each other, consistent with high differentiation and lack of gene flow among southern populations as suggested by allozyme data. Concordance between mtDNA and allozyme patterns suggests that cryptic speciation has occurred in L. fuscus without morphological or call differentiation. This study illustrates a case in which lineage splitting during the speciation process took place without divergence in reproductive isolation mechanisms (e.g. advertisement call in frogs), contrary to expectations predicted using a biological species framework.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 87 , 325–341. No claim to original US government works.