Species diversity and distribution of the calcareous green macroalgae Halimeda in Taiwan,Spratly Island,and Dongsha Atoll,with the proposal of Halimeda taiwanensis sp. nov.

The calcified green algal genus Halimeda is one of the most ecologically important but morphologically diverse seaweeds in sub-tropical and tropical waters. Because of its high morphological plasticity, the identification of Halimeda species based on morphological characters is challenging without the assistance of molecular analysis. To date, the species diversity of Halimeda in Taiwan and its overseas territories has not been investigated with the assistance of DNA sequencing, and this taxonomic knowledge gap should be filled. The present study initiates a systematic examination of the species diversity and distribution of Halimeda in Taiwan, Spratly Island, and Dongsha Atoll in the South China Sea, using DNA sequence data (plastid tufA gene and rbcL) and morphological data. Our DNA analyses revealed the presence of 10 Halimeda species (Halimeda borneensis, Halimeda cylindracea, Halimeda discoidea, Halimeda distorta, Halimeda macroloba, Halimeda minima, Halimeda opuntia, Halimeda renschii, Halimeda taiwanensis sp. nov., and Halimeda velasquezii) in the waters around Taiwan, Spratly Island, and Dongsha Atoll. The majority of the species could be readily distinguished by their morphological and anatomical characters. The proposed new species, H. taiwanensis, was differentiated not only by our algorithmic species delimitation analyses (statistical parsimony network analysis and automated barcode gap discovery), but also by its morphological features. The proposed new species differs from two externally resembled species, H. cuneata and H. discoidea, in having an undulated segment margin, the complete fusion of medullary siphons at the node, the lack of segment stalk, and the presence of a large primary utricle. Here, we present the up-to-date taxonomic account, molecular diversity, and geographical distribution of Halimeda spp. in Taiwan and associated areas of the South China Sea. Environmental factors that might drive the occurrence and latitudinal distribution of the species are also discussed.     

Molecular systematics,historical ecology,and phylogeography of Halimeda (Bryopsidales)

Halimeda (Bryopsidales), a genus of calcified, segmented green seaweeds, abounds in reefs and lagoons throughout the tropics. To investigate phylogenetic, phylogeographic, and historic ecological relationships of the genus, the nuclear rDNA including the SSU and both ITS regions were sequenced. A maximum likelihood tree revealed the following: (1) there were anatomical and morphological synapomorphies for five well-supported lineages; (2) the last common ancestor of one lineage invaded sandy substrata; those of two other lineages established in wave-affected habitats, whereas the cenancestor of the remaining two lineages occupied sheltered rocky slopes. Yet, several species adapted to new habitats subsequently, resulting in several cases of convergence; (3) all lineages separated into Atlantic and Indo-Pacific daughters, likely resulting from the rise of the Panamanian Isthmus. Each daughter pair gave rise to additional convergent species in similar habitats in different oceans; (4) Halimeda opuntia, the only monophyletic pantropical species detected so far, dispersed from the Indo-Pacific into the Atlantic well after the closure event; (5) minor SSU-sequence differences across species and phylogeographic patterns of vicariance indicated a relatively recent diversification of the extant diversity. Cretaceous and Early Tertiary fossil look-alikes of modern species must then have resulted from iterative convergence.     

Phylogeny and taxonomy of Halimeda incrassata,including descriptions of H. kanaloana and H. heteromorpha spp. nov. (Bryopsidales,Chlorophyta)

The tropical green algal genus Halimeda is one of the best studied examples of pseudo-cryptic diversity within the algae. Previous molecular and morphometric studies revealed that within Halimeda section Rhipsalis, Halimeda incrassata included three pseudo-cryptic entities and that the morphological boundaries between H. incrassata and Halimeda melanesica were ill-defined. In this paper, the taxonomy of H. incrassata is revised: two pseudo-cryptic entities are described as new species, Halimeda kanaloana and Halimed heteromorpha, while H. incrassata is redefined to encompass a single, monophyletic entity. Similarities and differences between the three species and H. melanesica are discussed. Monophyly of H. heteromorpha, which was questioned in a former study, is reinvestigated using sets of 32 ITS1–ITS2 and 21 plastid rps3 sequences and various alignment and inference methods. The phylogenetic relationships within Halimeda section Rhipsalis are inferred from nuclear 18S–ITS1–5.8S–ITS2 and concatenated plastid sequences (tufA & rpl5–rps8–infA) and interpreted in a biogeographic context.     

Biogeography and ecological niche evolution in Diapensiaceae inferred from phylogenetic analysis

Diapensiaceae (Ericales) are a small family of about 15 species. Within this clade, two species are broadly distributed throughout the Northern Hemisphere, whereas the remaining species have a disjunct distribution between eastern North America and eastern Asia. To address patterns and processes of diversification in Diapensiaceae, we conducted biogeographic analyses and inferred shifts in the ecological niche across the phylogeny of the clade. Although Diapensiaceae have been the focus of multiple phylogenetic and biogeographic studies, previous studies have been taxonomically limited. This study has greatly improved the phylogenetic underpinning for Diapensiaceae with the most inclusive taxonomic sampling thus far, employing both nuclear and plastid gene sequence data for at least one sample per species in the family. Our estimates indicate that genera of Diapensiaceae variously diverged in the Eocene, Oligocene, and early to mid‐Miocene. The biogeographic analysis suggests that the probable ancestor of the Diapensiaceae crown clade originated in the Nearctic, with vicariance events contributing to the current distribution of the disjunct taxa. Ecological niche, when considered in a phylogenetic context, was observed to be clustered on the basis of biogeographic realm. In general, a greater ecological overlap was found at younger nodes and a greater niche divergence was found among distantly related species. Diversification in Diapensiaceae appears to have been shaped by both large‐scale biogeographic factors, such as vicariance, and divergence in an ecological niche among closely related species.     

Dispersal, vicariance, and timing of diversification in Nothonotus darters

The species diversity of North American freshwater fishes is unparalleled among temperate regions of the planet. This diversity is concentrated in the Central Highlands of eastern North America and this distribution pattern has inspired different models involving either dispersal or vicariance to explain the high species diversity of North American fishes. The most popular of these models is the Central Highlands vicariance hypothesis (CHVH), which proposes an ancient and diverse widespread fauna that existed across a previously continuous highland landscape that is much different from today. The mechanisms of isolation in the CHVH involve specific instances of vicariance that affected several diverse lineages of Central Highlands fishes. We tested predictions of the CHVH and alternative models using a cytochrome b-inferred phylogeny of the darter clade Nothonotus. A Bayesian mixed-model method was used for phylogenetic analysis. The phylogenetic data set included all 20 recognized Nothonotus species, and most species were represented with multiple sequences. We were able to convert genetic branch lengths to absolute age using external fossil calibrations in the freshwater perciform fish clade Centrarchidae. Using a well-resolved Nothonotus phylogeny and divergence time estimates, we identify equal numbers of instances of both vicariance and dispersal among disjunct regions of the Central Highlands, biogeographic pseudocongruence, rather recent speciation in Nothonotus, and a surprisingly large amount of speciation within highland areas. With regard to Nothonotus, previous Central Highlands biogeographic models offer little in the way of providing possible mechanisms responsible for diversification in the clade. Patterns of speciation in Nothonotus are similar to those discovered in recent efforts that have included speciation as a parameter into classic models of island biogeography.     

Diversity of Halimeda (Bryopsidales,Chlorophyta) in New Caledonia: a Combined Morphological and Molecular Study

Halimeda is a genus of calcified and segmented green macroalgae in the order Bryopsidales. In New Caledonia, the genus is abundant and represents an important part of the reef flora. Previous studies recorded 19 species that were identified using morphological criteria. The aim of this work was to reassess the diversity of the genus in New Caledonia using morpho‐anatomical examinations and molecular analyses of the plastid tufA and rbcL genes. Our results suggest the occurrence of 22 species. Three of these are reported for the first time from New Caledonia: Halimeda kanaloana, H. xishaensis, and an entity resembling H. stuposa. DNA analyses revealed that the species H. fragilis exhibits cryptic or pseudocryptic diversity in New Caledonia. We also show less conclusive evidence for cryptic species within H. taenicola     

Phylogeography of the genus Cardiandra based on genetic variation in cpDNA sequences

We investigated the phylogenetic relationships within the genus Cardiandra based on plastid DNA sequences. The phylogenetic tree showed that Cardiandra populations from the Ryukyu Islands (Japan) and Taiwan were monophyletic (Ryukyu–Taiwan clade), whereas taxa from China and mainland Japan were sisters to this clade. The divergence time between the Ryukyu–Taiwan clade and the other species was estimated to be 0.082 MYA, i.e., the late Pleistocene. The infrageneric and/or infraspecific differentiation of Cardiandra is estimated to have depended largely on allopatric differentiation caused by the presence or division of the past landbridge of the Ryukyu Islands, which connected mainland Japan to the Asian Continent during the Quaternary.     

24 Diversity of macroalgal epiphytes on Thalassia and Syringodium in tampa bay, florida

Alaria is a common kelp genus generally found in the lower intertidal and shallow subtidal regions of rocky shores in the cold waters of the northern Hemisphere. About 16 species are currently recognized worldwide and, of these, A. fistulosa is distinguished by having hollow midrib and large blades with 10–30 m in length and 30–90 cm in width. It is the only canopy-producing kelp in the northwest Pacific, where it is restricted to the waters of north Hokkaido, Kamchatka, Aleutian Islands, and Alaska. In order to know the phylogenetic position of A. fistulosa , sequences of nr DNA ITS and plastid rbc L including spacer and psaA regions were determined in A. fistulosa and compared with homologous positions of newly sequenced putative relatives and with published sequences of other kelp species. Combined data of ITS and Rubisco spacer show that A. fistulosa was more related to the clade of Lessoniopsis and Pterygophora than to the clade of other species of Alaria , which is supported by the rbc L and psaA sequence data. The topologies from nuclear and plastid DNA sequences lead to phylogenetic independence of A. fistulosa , which is clearly different from the genus Alaria .     

Phylogenetic analyses indicate that the 19'Hexanoyloxy-fucoxanthin-containing dinoflagellates have tertiary plastids of haptophyte origin

The three anomalously pigmented dinoflagellates Gymnodinium galatheanum, Gyrodinium aureolum, and Gymnodinium breve have plastids possessing 19'-hexanoyloxy-fucoxanthin as the major carotenoid rather than peridinin, which is characteristic of the majority of the dinoflagellates. Analyses of SSU rDNA from the plastid and the nuclear genome of these dinoflagellate species indicate that they have acquired their plastids via endosymbiosis of a haptophyte. The dinoflagellate plastid sequences appear to have undergone rapid sequence evolution, and there is considerable divergence between the three species. However, distance, parsimony, and maximum-likelihood phylogenetic analyses of plastid SSU rRNA gene sequences place the three species within the haptophyte clade. Pavlova gyrans is the most basal branching haptophyte and is the outgroup to a clade comprising the dinoflagellate sequences and those of other haptophytes. The haptophytes themselves are thought to have plastids of a secondary origin; hence, these dinoflagellates appear to have tertiary plastids. Both molecular and morphological data divide the plastids into two groups, where G. aureolum and G. breve have similar plastid morphology and G. galatheanum has plastids with distinctive features.     

Origin, diversification, and evolution of Samolus valerandi (Samolaceae, Ericales)

The almost cosmopolitan distribution of Samolus valerandi is unique in the genus Samolus L. (Samolaceae), which also includes 12–15 taxa with distributions restricted to smaller areas of the Southern Hemisphere. Recent molecular phylogenetic studies based on chloroplast and nuclear DNA sequences showed that the widespread S. valerandi and the North American S. parviflorus are both part of a strongly supported clade, together with the North American S. vagans, S. spathulatus, and S. latifolius. To better understand the origin, distribution, and diversification of S. valerandi and to clarify the relationships within this clade, we performed molecular phylogenetic analyses based on the plastid trnS-G intergenic spacer and the nuclear ribosomal ITS region. We have also sought further support for relationships by examining flower and leaf characters. On the basis of new results, we propose that S. valerandi, S. parviflorus, and S. vagans are considered as part of a widespread “species complex”, with its centre of diversity in North America. No clear vicariance patterns were found regarding the phylogeography of S. valerandi, which thus seems to have dispersed secondarily to various places around the world, possibly as a result of human activities.     

The evolutionary history of Eryngium (Apiaceae, Saniculoideae): rapid radiations, long distance dispersals, and hybridizations

Eryngium is the largest and arguably the most taxonomically complex genus in the family Apiaceae. Infrageneric relationships within Eryngium were inferred using sequence data from the chloroplast DNA trnQ-trnK 5'-exon and nuclear ribosomal DNA ITS regions to test previous hypotheses of subgeneric relationships, explain distribution patterns, reconstruct ancestral morphological features, and elucidate the evolutionary processes that gave rise to this speciose genus. In total, 157 accessions representing 118 species of Eryngium, 15 species of Sanicula (including the genus Hacquetia that was recently reduced to synonymy) and the monotypic Petagnaea were analyzed using maximum parsimony and Bayesian methods. Both separate and simultaneous analyses of plastid and nuclear data sets were carried out because of the prevalence of polyploids and hybrids within the genus. Eryngium is confirmed as monophyletic and is divided into two redefined subgenera: Eryngium subgenus Eryngium and E. subgenus Monocotyloidea. The first subgenus includes all examined species from the Old World (Africa, Europe, and Asia), except Eryngium tenue, E. viviparum, E. galioides, and E. corniculatum. Eryngium subgenus Monocotyloidea includes all examined species from the New World (North, Central and South America, and Australia; herein called the "New World sensu stricto" clade) plus the aforementioned Old World species that fall at the base of this clade. Most sectional and subgeneric divisions previously erected on the basis of morphology are not monophyletic. Within the "New World sensu stricto" group, six clades are well supported in analyses of plastid and combined plastid and nuclear data sets; the relationships among these clades, however, are unresolved. These clades are designated as "Mexican", "Eastern USA", "South American", "North American monocotyledonous", "South American monocotyledonous", and "Pacific". Members of each clade share similar geographical distributions and/or morphological or ecological traits. Evidence from branch lengths and low sequence divergence estimates suggests a rapid radiation at the base of each of these lineages. Conflict between chloroplast and nuclear data sets is weak, but the disagreements found are suggestive that hybrid speciation in Eryngium might have been a cause, but also a consequence, of the different rapid radiations observed. Dispersal-vicariance analysis indicates that Eryngium and its two subgenera originated from western Mediterranean ancestors and that the present-day distribution of the genus is explained by several dispersal events, including one trans-Atlantic dispersal. In general, these dispersals coincide with the polytomies observed, suggesting that they played key roles in the diversification of the genus. The evolution of Eryngium combines a history of long distance dispersals, rapid radiations, and hybridization, culminating in the taxonomic complexity observed today in the genus.     

Phylogenetic relationships and biogeography of the desert plant genus Fagonia (Zygophyllaceae), inferred by parsimony and Bayesian model averaging

Phylogenetic relationships within Fagonia were inferred from analyses of plastid trnL intron and nuclear ribosomal ITS DNA sequences. Sampling of the genus was nearly complete, including 32 of 34 species. Phylogenetic analysis was carried out using parsimony, and Bayesian model averaging. The latter method allows model-based inference while accounting for model-selection uncertainty, and is here used for the first time in phylogenetic analyses. All species of Fagonia in the Old World, except F. cretica, form a weakly supported clade, and all Fagonia species of the New World, except F. scoparia, are well supported as sister to the Old World clade. Fagonia scoparia, from Mexico, and F. cretica, from Northern Africa, are well supported as sisters to all other Fagonia species. Vicariance-dispersal analysis, using DIVA, indicated that the occurrences of Fagonia in South America and southern Africa are due to dispersals, and also, that the ancestor of Fagonia had a distribution compatible with the boreotropics hypothesis.     

Comparative analysis of 343 plastid genomes of Solanum section Petota: Insights into potato diversity,phylogeny, and species discrimination

Common potato (Solanum tuberosum L.) and its wild relatives belong to Solanum section Petota. This section's phylogeny and species delimitation are complicated due to various ploidy levels, high heterozygosity, and frequent interspecific hybridization. Compared to the nuclear genome, the plastid genome is more conserved, has a haploid nature, and has a lower nucleotide substitution rate, providing informative alternative insights into the phylogenetic study of section Petota. Here, we analyzed 343 potato plastid genomes from 53 wild and four cultivated species. The diversity of sequences and genomes was comprehensively analyzed. A total of 24 species were placed in a phylogenetic tree based on genomic data for the first time. Overall, our results not only confirmed most existing clades and species boundaries inferred by nuclear evidence but also provided some distinctive species clade belonging and the maternally inherited evidence supporting the hybrid origin of some species. Furthermore, the divergence times between the major potato clades were estimated. In addition, the species discriminatory power of universal barcodes, nuclear ribosomal DNA, and whole and partial plastid genomes and their combinations were thoroughly evaluated; the plastid genome performed best but had limited discriminatory power for all survey species (40%). Overall, our study provided not only new insights into phylogeny and DNA barcoding of potato but also provided valuable genetic data resources for further systematical research of Petota.     

In vitro and in vivo analysis of transcription within the replication region of plasmid pIP501

Summary The tobacco (Nicotiana tabacum) nuclear genome contains long tracts of DNA (i.e. in excess of 18 kb) with high sequence homology to the tobacco plastid genome. Five lambda clones containing these nuclear DNA sequences encompass more than one-third of the tobacco plastid genome. The absolute size of these five integrants is unknown but potentially includes uninterrupted sequences that are as large as the plastid genome itself. An additional sequence was cloned consisting of both nuclear and plastid-derived DNA sequences. The nuclear component of the clone is part of a family of repeats, which are present in about 400 locations in the nuclear genome. The homologous sequences present in chromosomal DNA were very similar to those of the corresponding sequences in the plastid genome. However significant sequence divergence, including base substitutions, insertions and deletions of up to 41 bp, was observed between these nuclear sequences and the plastid genome. Associated with the larger deletions were sequence motifs suggesting that processes such as DNA replication slippage and excision of hairpin loops may have been involved in deletion formation.     

A phylogenetic analysis of the Arecoid Line of palms based on plastid DNA sequence data

A phylogenetic analysis of the Arecoid Line (sensu Moore) of palms was conducted using 7 kb of coding and noncoding plastid DNA sequence data. Recovered maximum-parsimony and maximum-likelihood phylogenies support monophyly for the Arecoid Line relative to the rest of the family but paraphyly for subfamily Arecoideae and polyphyly for subfamily Ceroxyloideae (sensu Dransfield and Uhl). Tribes Cocoeae, Geonomeae, Hyophorbeae, and Iriarteae and subfamily Phytelephantoideae were identified as monophyletic as were subfamily Phytelephantoideae + Ravenea (tribe Ceroxyleae of Ceroxyloideae), Podococcus (tribe Podococceae of Arecoideae) + Pseudophoenix (tribe Cyclospatheae of Ceroxyloideae), Reinhardtia (tribe Malortieinae) + tribe Cocoeae (both of Arecoideae), and a clade containing all IndoPacific pseudomonomerous genera of tribe Areceae (Arecoideae). A few taxa show spurious resolution with noncoding plastid DNA data but noncoding data are generally congruent with protein-coding data. Biogeographic interpretation suggests a Gondwanan origin for the Arecoid Line with several lineages found on more than one fragment of the former supercontinent and primary diversification in these groups possibly due to continental breakup vicariance. Three groups involving Cocos, Orania, and the IndoPacific clade demonstrate independent dispersals into the IndoPacific region from a Gondwanan origin.     

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.     

Phylogenetic studies of Ophioglossaceae: evidence from rbcL and trnL-F plastid DNA sequences and morphology

Ophioglossaceae are a putatively ancient lineage of ferns in which the aerial portion of the plant is composed of a single leaf. The simplicity of foliar morphology has limited the number of characters available for constructing classifications and contributed to taxonomic difficulties at nearly every level of classification within the family. Analysis of plastid DNA rbcL sequences from 36 species representing the diversity of Ophioglossaceae supported the monophyly of the family. Intrafamilial relationships were examined using rbcL and trnL-F plastid DNA sequences and morphological data. Individual and combined analyses of the three data sets revealed two main clades within the family, here termed ophioglossoid and botrychioid. In the botrychioid clade, Helminthostachys was sister to a broadly defined Botrychium, within which Botrychium in the narrow sense of some authors and Sceptridium were sister. Botrypus was paraphyletic, with Botrypus virginianus sister to Botrychium plus Sceptridium, and with Botrypus strictus sister to all other botrychioid species except Helminthostachys. In the ophioglossoid clade, Ophioglossum in the narrow sense was sister to Cheiroglossa plus Ophioderma, but relationships within Ophioglossum were not well supported.     

Phylogeny of east asian bufonids inferred from mitochondrial DNA sequences (Anura: amphibia)

We investigated the relationships of Asian bufonids using partial sequences of mitochondrial DNA genes. Twenty-six samples representing 14 species of Bufo from China and Vietnam and 2 species of Torrentophryne from China were examined. Three samples of Bufo viridis from Armenia and Georgia were also sequenced to make a comparison to its sibling tetraploid species B. danatensis. Bufo americanus, from Canada, was used as the outgroup. Sequences from the 12S ribosomal RNA, 16S ribosomal RNA, cytochrome b, and the control region were analyzed using parsimony. East Asian bufonids were grouped into two major clades. One clade included B. andrewsi, B. bankorensis, B. gargarizans, B. tibetanus, B. tuberculatus, its sister clade B. cryptotympanicus, and the 2 species of Torrentophryne. The second clade consisted of B. galeatus, B. himalayanus, B. melanostictus, and a new species from Vietnam. The placement of three taxa (B. raddei, B. viridis, and its sister species, B. danatensis) was problematic. The genus Torrentophryne should be synonymized with Bufo to remove paraphyly. Because B. raddei does not belong to the clade that includes B. viridis and B. danatensis, it was removed from the viridis species group. The species status of B. bankorensis from Taiwan is evaluated.     

Northern Hemisphere origin,transoceanic dispersal,and diversification of Ranunculeae DC. (Ranunculaceae) in the Cenozoic

Aim The role of dispersal versus vicariance for plant distribution patterns has long been disputed. We study the temporal and spatial diversification of Ranunculeae, an almost cosmopolitan tribe comprising 19 genera, to understand the processes that have resulted in the present inter‐continental disjunctions. Location All continents (except Antarctica). Methods Based on phylogenetic analyses of nuclear and chloroplast DNA sequences for 18 genera and 89 species, we develop a temporal–spatial framework for the reconstruction of the biogeographical history of Ranunculeae. To estimate divergence dates, Bayesian uncorrelated rates analyses and four calibration points derived from geological, fossil and external molecular information were applied. Parsimony‐based methods for dispersal–vicariance analysis (diva and Mesquite ) and a maximum likelihood‐based method (Lagrange ) were used for reconstructing ancestral areas. Six areas corresponding to continents were delimited. Results The reconstruction of ancestral areas is congruent in the diva and maximum likelihood‐based analyses for most nodes, but Mesquite reveals equivocal results at deep nodes. Our study suggests a Northern Hemisphere origin for the Ranunculeae in the Eocene and a weakly supported vicariance event between North America and Eurasia. The Eurasian clade diversified between the early Oligocene and the late Miocene, with at least three independent migrations to the Southern Hemisphere. The North American clade diversified in the Miocene and dispersed later to Eurasia, South America and Africa. Main conclusions Ranunculeae diversified between the late Eocene and the late Miocene. During this time period, the main oceanic barriers already existed between continents and thus dispersal is the most likely explanation for the current distribution of the tribe. In the Southern Hemisphere, a vicariance model related to the break‐up of Gondwana is clearly rejected. Dispersals between continents could have occurred via migration over land bridges, such as the Bering Land Bridge, or via long‐distance dispersal.     

Intraspecific phylogeography of Percina evides (Percidae: Etheostomatinae): an additional test of the Central Highlands pre-Pleistocene vicariance hypothesis

North America exhibits the most diverse freshwater fish fauna among temperate regions of the world. Species diversity is concentrated in the Central Highlands, drained by the Mississippi, Gulf Slope and Atlantic Slope river systems. Previous investigations of Central Highlands biogeography have led to conflicting hypotheses involving dispersal and vicariance to explain the diversity and distribution of the freshwater fish fauna. In this investigation predictions of the Central Highlands pre-Pleistocene vicariance hypothesis are tested with a phylogeographic analysis of the percid species Percina evides, which is widely distributed in several disjunct areas of the Central Highlands. Phylogenetic analysis of complete gene sequences of mitochondrially encoded cytochrome b recover three phylogroups, with very low levels of sequence polymorphism within groups. The two western phylogroups are monophyletic with respect to the eastern phylogroup. The recovery of two monophyletic lineages with an eastern and western distribution in the disjunct highland areas is a pattern expected from vicariance, but is not predicted by the Central Highlands pre-Pleistocene vicariance hypothesis. The recovery of very limited mitochondrial DNA polymorphism and lack of phylogeographic structuring across the entire range of the eastern clade, very shallow polymorphism between the disjunct Missouri River and upper Mississippi River populations, and lack of sequence polymorphism in the upper Mississippi River populations, support a hypothesis of dispersal during or following the Pleistocene. The present distribution of P. evides is best explained by both vicariant and dispersal events.