Conservation and genetics of the frosted flatwoods salamander (Ambystoma cingulatum) on the Atlantic coastal plain

The federally threatened frosted flatwoods salamander, Ambystoma cingulatum, occurs in isolated populations on the coastal plain of northern Florida, Georgia and South Carolina. An earlier phylogeographic study based primarily on mitochondrial DNA (mtDNA) and morphometrics demonstrated that the previously recognized species A. cingulatum contained two cryptic species, and that two distinct mtDNA clades were contained within the newly restricted A. cingulatum. However, salamanders from the northern extent of the species range in South Carolina were not previously available for analysis. Here, we used individuals from a newly discovered South Carolina breeding site to determine whether A. cingulatum from South Carolina are genetically distinct from their more southerly conspecifics. These analyses included the mitochondrial gene studied previously as well as broad geographic sampling of three rapidly evolving nuclear genes that allowed us to further investigate lineage diversification of flatwoods salamanders. The mitochondrial and nuclear results are largely congruent, yielding strong support for two distinct species of flatwoods salamanders and also two lineages within the eastern species. Further, the South Carolina specimens are closely related to other haplotypes found in eastern Georgia and Florida. Our summary of field surveys over the past 20 years indicates that this South Carolina population may be one of only three remaining in the entire Atlantic coastal plain distribution of this rare and declining amphibian species.     

New data elucidating the taxonomy and ecology of the Parabrotulidae (Pisces: Zoarcoidei)

One hundred and eighty-two new specimens of Parabrotula and 52 Leucobrotula are reported. Generic separation is confirmed. although premaxillary dentition no longer distinguishes the two. Two species of Parabrotula (one yet to be described) and one of Leucobrotula are strongly indicated from meristic data. Breeding biology is considered, with comment upon sexual dimorphism in size, size at maturity and possible breeding period. Parabrotulu plagiophthalmus Zugmayer, 1911 is shown to be a midwater non-migrant species (range 76@1500 m) with a temperature preference in the eastern North Atlantic of 9.0–5.0° C. Leucobrotulu udipatus Koefoed, 1952 exhibits a depth range of 61–1290 m and a temperature range of 9.0–4.2° C. Geographically it is evidently restricted to the North Atlantic and endemic to the eastern side. Most specimens were caught pelagically in the northwest African upwelling area in slope waters. Parabrotulaplagiophthalnius is distributed worldwide, although 89% came from the eastern North Atlantic.     

Trans‐Pacific and trans‐Arctic pathways of the intertidal macroalga Fucus distichus L. reveal multiple glacial refugia and colonizations from the North Pacific to the North Atlantic

Aim We examined the phylogeography of the cold‐temperate macroalgal species Fucus distichus L., a key foundation species in rocky intertidal shores and the only Fucus species to occur naturally in both the North Pacific and the North Atlantic. Location North Pacific and North Atlantic oceans (42° to 77° N). Methods We genotyped individuals from 23 populations for a mitochondrial DNA (mtDNA) intergenic spacer (IGS) (n = 608) and the cytochrome c oxidase subunit I (COI) region (n = 276), as well as for six nuclear microsatellite loci (n = 592). Phylogeographic structure and connectivity were assessed using population genetic and phylogenetic network analyses. Results IGS mtDNA haplotype diversity was highest in the North Pacific, and divergence between Pacific haplotypes was much older than that of the single cluster of Atlantic haplotypes. Two ancestral Pacific IGS/COI clusters led to a widespread Atlantic cluster. High mtDNA and microsatellite diversities were observed in Prince William Sound, Alaska, 11 years after severe disturbance by the 1989 Exxon Valdez oil spill. Main conclusions At least two colonizations occurred from the older North Pacific populations to the North Atlantic between the opening of the Bering Strait and the onset of the Last Glacial Maximum. One colonization event was from the Japanese Archipelago/eastern Aleutians, and a second was from the Alaskan mainland around the Gulf of Alaska. Japanese populations probably arose from a single recolonization event from the eastern Aleutian Islands before the North Pacific–North Atlantic colonization. In the North Atlantic, the Last Glacial Maximum forced the species into at least two known glacial refugia: the Nova Scotia/Newfoundland (Canada) region and Andøya (northern Norway). The presence of two private haplotypes in the central Atlantic suggests the possibility of colonization from other refugia that are now too warm to support F. distichus. With the continuing decline in Arctic ice cover as a result of global climate change, renewed contact between North Pacific and North Atlantic populations of Fucus species is expected.     

Taxonomy of Gentiana,section Pneumonanthae,in eastern North America

The taxonomy ofGentiana (Gentianaceae), sect.Pneumonanthae, in eastern North America is reviewed. Two species and one variety recognized in recent literature are reduced to synonymy, while one overlooked variety is restored to recognition. Distributional data include several reductions in range resulting from examination of previously misidentified specimens. Thirteen species are native to eastern North America; all are restricted to it. Of these, three are primarily prairie species; three, Appalachian; three, coastal plain; two, southern plateau; one, eastern boreal; and one, Great Lakes region to central boreal. Interfertility and occasional natural hybridization are present even among the most morphologically diverse species.     

Phylogenetics and biogeography of eastern Asian-North American disjunct genus Pachysandra （Buxaceae） inferred from nucleotide sequences

Pachysandra is an eastern Asian-North American disjtunct genus with three species, two in eastern Asia （Pachysandra axillaris and Pachysandra terminalis） and one in eastern North America （Pachysandra procurnbens）. Although morphological and cytological studies suggest a close affinity of Pprocumbens with P axillaris, molecular data from nuclear and chloroplast DNA regions have provided conflicting signals. In this study, we tested previous phylogenetic hypotheses using sequences of nuclear ribosomal DNA internal transcribed spacers and chloroplast ndhF gene from multiple individuals of each of the three species. We also estimated the time of divergence between eastem Asia and eastern North America. Our results support the morphological and cytological conclusion that P procumbens is more closely related to P axillaris than to P terminalis. The estimated time of divergence of P axillaris and P procumbens was 14.6±5.5 mya, consistent with estimates from many other eastern Asian-North American disjunct genera. The migration of Pachysandra populations from eastern Asia to North America might have occurred by way of the North Atlantic land bridge.     

紫荆属的系统发育和生物地理学研究

紫荆属（Cercis L.）约含8种,间断分布于亚洲东、西部、欧洲南部和北美。应用核糖体DNA的ITS基因序列研究紫荆属的系统发育关系。在最简约性分析,北美的两个种和南欧、西亚的一个种构成一单系群而隐藏于东亚的种类中。这表明紫荆属北美的种类和南欧、西亚的种类之间的关系比它们的各自与东亚的种类的关系要密切。研究还发现北美洲东、西部的种类可能具较近亲缘。紫荆属以白令陆桥或北大西洋陆桥为迁移途径的可能性似乎都不能排除;北半球的生物地理分布式样可具有复杂的起源。     

Integrated Fossil and Molecular Data Reveal the Biogeographic Diversification of the Eastern Asian-Eastern North American Disjunct Hickory Genus (Carya Nutt.)

The hickory genus (Carya) contains ca. 17 species distributed in subtropical and tropical regions of eastern Asia and subtropical to temperate regions of eastern North America. Previously, the phylogenetic relationships between eastern Asian and eastern North American species of Carya were not fully confirmed even with an extensive sampling, biogeographic and diversification patterns had thus never been investigated in a phylogenetic context. We sampled 17 species of Carya and 15 species representing all other genera of the Juglandaceae as outgroups, with eight nuclear and plastid loci to reconstruct the phylogeny of Carya. The phylogenetic positions of seven extinct genera of the Juglandaceae were inferred using morphological characters and the molecular phylogeny as a backbone constraint. Divergence times within Carya were estimated with relaxed Bayesian dating. Biogeographic analyses were performed in DIVA and LAGRANGE. Diversification rates were inferred by LASER and APE packages. Our results support two major clades within Carya, corresponding to the lineages of eastern Asia and eastern North America. The split between the two disjunct clades is estimated to be 21.58 (95% HPD 11.07-35.51) Ma. Genus-level DIVA and LAGRANGE analyses incorporating both extant and extinct genera of the Juglandaceae suggested that Carya originated in North America, and migrated to Eurasia during the early Tertiary via the North Atlantic land bridge. Fragmentation of the distribution caused by global cooling in the late Tertiary resulted in the current disjunction. The diversification rate of hickories in eastern North America appeared to be higher than that in eastern Asia, which is ascribed to greater ecological opportunities, key morphological innovations, and polyploidy.     

Global distribution of cryptic native,introduced and hybrid lineages in the widespread estuarine amphipod Ampithoe valida

Biological invasions can pose a severe threat to coastal ecosystems, but are difficult to track due to inaccurate species identifications and cryptic diversity. Here, we clarified the cryptic diversity and introduction history of the marine amphipod Ampithoe valida by sequencing a mtDNA locus from 683 individuals and genotyping 10,295 single-nucleotide polymorphisms (SNPs) for 349 individuals from Japan, North America and Argentina. The species complex consists of three cryptic lineages: two native Pacific and one native Atlantic mitochondrial lineage. It is likely that the complex originated in the North Pacific and dispersed to the north Atlantic via a trans-arctic exchange approximately 3 MYA. Non-native A. valida in Argentina have both Atlantic mitochondrial and nuclear genotypes, strongly indicating an introduction from eastern North America. In two eastern Pacific estuaries, San Francisco Bay and Humboldt Bay, California, genetic data indicate human-mediated hybridization of Atlantic and Pacific sources, and possible adaptive introgression of mitochondrial loci, nuclear loci, or both. The San Francisco Bay hybrid population periodically undergoes population outbreaks and profoundly damages eelgrass Zostera marina thalli via direct consumption, and these ecological impacts have not been documented elsewhere. We speculate that novel combinations of Atlantic and Pacific lineages could play a role in A. valida’s unique ecology in San Francisco Bay. Our results reinforce the notion that we can over-estimate the number of non-native invasions when there is cryptic native structure. Moreover, inference of demographic and evolutionary history from mitochondrial loci may be misleading without simultaneous survey of the nuclear genome.

     

Molecular phylogeny, biogeography, and systematics of Dicerandra (Lamiaceae), a genus endemic to the southeastern United States

Dicerandra, an endemic mint of the southeastern United States, comprises nine species, all of which are threatened or endangered and restricted to sandhill vegetation and a mosaic of scrub habitats. Molecular phylogenetic analyses of Dicerandra based on data from the nuclear and plastid genomes for all 13 taxa of the genus, identified two strongly supported clades, corresponding to the four annual and to the five perennial species of Dicerandra. However, the nuclear and plastid trees were incongruent in their placement of two perennial taxa, D. cornutissima and D. immaculata var. savannarum, perhaps due to ancient hybridization or to lineage sorting. Based on these analyses, the widespread D. linearifolia is not monophyletic, with populations of D. linearifolia var. linearifolia falling into either western or eastern clades. The western clade, comprising populations of D. linearifolia var. linearifolia and var. robustior, occurs in an area drained by rivers flowing toward the Gulf of Mexico, whereas the eastern clade, comprising populations of D. linearifolia var. linearifolia, D. densiflora, D. odoratissima, and D. radfordiana (i.e., all the annual species), occupies a region drained by rivers flowing to the Atlantic Ocean. Although this pattern of genetic differentiation between populations from these two river drainages has been documented in several animal species, it has not previously been reported for plants. A revised subgeneric classification is presented to reflect the annual and perennial clades.     

Phylogeny and Biogeography of Thuja L. (Cupressaceae), an Eastern Asian and North American Disjunct Genus

In order to develop better insights into biogeographic patterns of eastern Asian and North American disjunct plant genera, sequences of nuclear ribosomal DNA internal transcribed spacer (nr DNA ITS) region were used to estimate interspecific relationships of Thuja L. (Cupressaceae) and infer its biogeography based on the phylogeny. According to the phylogenetic analysis, two clades were recognized. The first clade included Thuja plicata D. Don (western North America) and T. koraiensis Nakai (northeastern Asia), and the second one contained T. occidentalis (Gord.) Carr. (Japan). The ancestral area of Thuja was inferred to be eastern Asia, and two dispersal events were responsible for the modern distribution of Thuja in North America. Both the North Atlantic land bridge and Bering land bridge were possible routes for the migration of ancestral populations to North America.     

Habitat specialization and phylogenetic structure of tree species in a coastal Brazilian white-sand forest

Aims The coastal Brazilian rainforest on white-sand (restinga) ranks among the most fragmented forest types in the tropics, owing to both the patchy distribution of sandy soils and widespread coastal development activities. Here we study the environmental and evolutionary determinants of a forest tree assemblage at a single restinga forest in Southeastern Brazil. We also explore the ability of competing hypotheses to explain the maintenance of species diversity in this forest type, which includes contrasting extremes of edaphic conditions associated with flooding stress.Methods The study was conducted in a white-sand forest permanent plot of 10.24 ha on the coastal plain of Southeastern Brazil. This plot was divided into 256 quadrats of 20×20 m, which were classified into two main edaphic habitats (flooded and drained). Trees with a diameter ≥1cm at breast height were identified. We assembled DNA sequence data for each of the 116 morphospecies recognized using two chloroplast markers (rbcL and matK). A phylogenetic tree was obtained using the maximum likelihood method, and a phylogenetic distance matrix was produced from an ultrametric tree. We analyzed similarity in floristic composition and structure between habitats and related them to cross-plot distances using permutation procedures. Null model torus shift simulations were performed to obtain a statistical significance level for habitat association for each species. The phylogenetic structure for the two habitats and for each 20×20 m quadrat was calculated using the mean phylogenetic distance weighted by species abundance and checked for significance using the standardized effect size generated by 5000 randomizations of phylogenetic tip labels.Important findings Our results indicate that partitioning among edaphic habitats is important for explaining species distributions and coexistence in restinga forests. Species distributions within the plot were found to be non-random: there was greater floristic similarity within than between habitats, and>40% of the more abundant species were positively or negatively associated with at least one habitat. Patterns of habitat association were not independent of phylogenetic relatedness: the community was overdispersed with respect to space and habitat type. Closely related species tended to occur in different habitats, while neighboring trees tended to belong to more distantly related species. We conclude that habitat specialization is important for the coexistence of species in restinga forests and that habitat heterogeneity is therefore an essential factor in explaining the maintenance of diversity of this unique but fragile and threatened type of forest.     

Marine mites (Halacaroidea: Acari): a geographical and ecological survey

Halacarid mites (Acari), with almost 700 species described, inhabit marine and freshwater habitats. The majority of genera are recorded from at least two ocean basins or continents. There is no evidence of endemic genera, in either littoral faunal provinces or in deep-sea regions. Copidognathus, a genus comprising 1/4 of all species described, is found in almost all geographic regions, depths and habitats. Other genera dominate or are restricted to cold waters, to warm waters or to distinct habitats.Corresponding habitats on either side of the boreal Atlantic Ocean harbour congeneric, identical, sibling or morphologically similar species. The fauna in the western Atlantic is less diverse than that in the eastern. Amphiatlantics are restricted to certain genera. Transatlantic distribution is independent of the niche inhabited.Of the marine halacarid species recorded from the boreal western Atlantic, 41% are amphiatlantics, while only one species is recorded from both the Caribbean and the Mediterranean. The Caribbean and the Mediterranean faunas are dominated by genera in which amphiatlantics are unknown.Most of the Black Sea species of the genus Halacarellus also occur in the Baltic, North Sea or North Atlantic, whereas the Copidognathus fauna of the Black Sea is similar to that of the Mediterranean.Halacarids are thought to be an ancient taxon, with most genera probably having been present since the Mesozoic and with several species having an age of at least 50 million years. Evidence for their antiquity is found in the distributional pattern of marine and limnic genera and species, in the lack of endemic genera despite low fecundity and lack of dispersal stages, and in the fact that amphiatlantics are restricted to certain genera without relationships to the niches inhabited.     

Endemic birds of the Atlantic Forest: traits,conservation status,and patterns of biodiversity

The bird fauna of the Brazilian Atlantic Forest is exceptionally diverse and threatened, with high levels of endemism. Available lists of the endemic birds of the Atlantic Forest were generated before recent taxonomic revisions lumped or split species and before the recent increase in species occurrence records. Our objective, therefore, was to compile a new list of the endemic birds of the Atlantic Forest, characterize these species in terms of conservation status and natural history traits, and map remaining vegetation and protected areas. We combined GIS analysis with a literature search to compile a list of endemic species and, based on the phylogeny and distribution of these species, characterized areas in terms of species richness, phylogenetic diversity, and endemism. We identified 223 species of birds endemic to the Atlantic Forest, including 12 species not included in previous lists. In addition, 14 species included in previous lists were not considered endemic, either because they occur outside the Atlantic Forest biome or because they are not considered valid species. The typical Atlantic Forest endemic bird is a small forest‐dependent invertivore. Of the species on our list, 31% are considered threatened or extinct. Only ~ 34% of the spatial analysis units had > 10% forest cover, and protected area coverage was consistently low (< 1%). In addition, we found spatial incongruity among the different measures of biodiversity (species richness, relative phylogenetic diversity, restricted‐range species, and irreplaceability). Each of these measures provides information concerning different aspects of biological diversity. However, regardless of which aspect(s) of biodiversity might be considered most important, preservation of the remaining areas of remnant vegetation and further expansion of protected areas are essential if we are to conserve the many endemic species of birds in the Atlantic Forest.     

Species-level phylogeography and evolutionary history of the hyperdiverse marine gastropod genus Conus

Phylogenetic and paleontological analyses are combined to reveal patterns of species origination and divergence and to define the significance of potential and actual barriers to dispersal in Conus, a species-rich genus of predatory gastropods distributed throughout the world's tropical oceans. Species-level phylogenetic hypotheses are based on nucleotide sequences from the nuclear calmodulin and mitochondrial 16S rRNA genes of 138 Conus species from the Indo-Pacific, eastern Pacific, and Atlantic Ocean regions. Results indicate that extant species descend from two major lineages that diverged at least 33 mya. Their geographic distributions suggest that one clade originated in the Indo-Pacific and the other in the eastern Pacific + western Atlantic. Impediments to dispersal between the western Atlantic and Indian Oceans and the central and eastern Pacific Ocean may have promoted this early separation of Indo-Pacific and eastern Pacific + western Atlantic lineages of Conus. However, because both clades contain both Indo-Pacific and eastern Pacific + western Atlantic species, migrations must have occurred between these regions; at least four migration events took place between regions at different times. In at least three cases, incursions between regions appear to have crossed the East Pacific Barrier. The paleontological record illustrates that distinct sets of Conus species inhabited the Indo-Pacific, eastern Pacific + western Atlantic, and eastern Atlantic + former Tethys Realm in the Tertiary, as is the case today. The ranges of <1% of fossil species (N=841) spanned more than one of these regions throughout the evolutionary history of this group.     

Phylogenetics and biogeography of eastern Asian–North American disjunct genus Pachysandra (Buxaceae) inferred from nucleotide sequences

Abstract Pachysandra is an eastern Asian–North American disjunct genus with three species, two in eastern Asia (Pachysandra axillaris and Pachysandra terminalis) and one in eastern North America (Pachysandra procumbens). Although morphological and cytological studies suggest a close affinity of P. procumbens with P. axillaris, molecular data from nuclear and chloroplast DNA regions have provided conflicting signals. In this study, we tested previous phylogenetic hypotheses using sequences of nuclear ribosomal DNA internal transcribed spacers and chloroplast ndhF gene from multiple individuals of each of the three species. We also estimated the time of divergence between eastern Asia and eastern North America. Our results support the morphological and cytological conclusion that P. procumbens is more closely related to P. axillaris than to P. terminalis. The estimated time of divergence of P. axillaris and P. procumbens was 14.6±5.5 mya, consistent with estimates from many other eastern Asian–North American disjunct genera. The migration of Pachysandra populations from eastern Asia to North America might have occurred by way of the North Atlantic land bridge.     

Anatomically preserved Liquidambar (Altingiaceae) from the middle Miocene of Yakima Canyon, Washington state, USA, and its biogeographic implications

Liquidambar changii Pigg, Ickert-Bond & Wen sp. nov. (Altingiaceae) is established for anatomically preserved, middle Miocene infructescences from Yakima Canyon, Washington, USA. Specimens are spherical, ～2.5 cm in diameter, and have ～25-30 tightly packed, bilocular fruits per head. Fruits are 3.4-4.7 mm wide × 2.6-3.5 mm long and wedge shaped, fused at the base, and free distally. Each locule contains 1-2 mature, elongate seeds proximally and 5-9 aborted seeds of more irregular shape distally. Mature seeds are 1.5 mm long × 1.2 mm wide, elongate, and triangular transversely, with a slight flange. Seeds have a seed coat for which three zones can be well defined, a uniseriate outer palisade layer, a middle region of isodiametric cells comprising most of the integument, and a uniseriate inner layer of tangentially elongate cells lining the embryo cavity. Liquidambar changii is most similar to the eastern Asian L. acalycina H.-T. Chang on features of infructescence, fruit, and seed morphology and quite unlike the North American L. styraciflua L. and other species. Such a close relationship between these two species supports a Beringian biogeographic track between eastern Asia and western North America during the Miocene. Previous phylogenetic and allozyme analysis of modern Liquidambar demonstrates a close relationship between North American-western Asian taxa and suggests a North Atlantic biogeographic track in the middle Miocene. Together, these biogeographic tracks underscore the complexity of the biogeographic history of the Altingiaceae in the Northern Hemisphere throughout the Neogene.     

The genus Leptophytum (Melobesioideae, Corallinales, Rhodophyta) in NW Spitsbergen

Three species of the genus Leptophytum , viz. the generitype L. laeve, L. foecundum and the new Arctic endemic L. jenneborgii nov. sp. are described from localities in NW Spitsbergen. A fourth species, related to L. laeve , may also be present and its status requires further comparative studies with Lithothamnion tenue described from western Greenland. Leptophytum jenneborgii is restricted to sublittoral sites around Vasahalvøya, between 8 and 30 m depth growing on hard substrates (usually on Lithothamnion glaciate ) and forming encrusting to foliose thalli up to 10 cm in diameter. New lamellae develop in an unattached-superimposed pattern, overgrowing the parent thallus, so that individuals can reach at least 1.5 cm in thickness. Thallus organization is dorsiventral, with a noncoaxial hypothallium (producing rare patches of coaxial cells) and an ascending perithallium with short subepithallial and flattened epithallial cells. Multiporate conceptacles have convex or flattened roof and develop specialized (thinner-wider) pore cells lining the canals. This character combination supports a position in the genus Leptophytum , as recently emended by Athanasiadis & Adey (2006), and simultaneously distinguishes L. jenneborgii from its Arctic and North Atlantic congeners. Like Leptophytum arcticum nov. comb., that is only known from Uddebay on the east coast of Novaja Zemlya, L. jenneborgii shows a restricted distribution on the presumed north periphery of maximum ice cover during the latest glaciation. It is suggested that these two species represent the first evidence of algal glacial survivals in this part of the Arctic.     

ISOZYME DIVERGENCE BETWEEN EASTERN ASIAN,NORTH AMERICAN,AND TURKISH SPECIES OF LIQUIDAMBAR (HAMAMELIDACEAE)

The deciduous woody genus Liquidambar has four morphologically similar species in eastern and western Asia, eastern North America, and Central America. Liquidambar styraciflua is found in the eastern United States and Central America, L. orientalis is native only to southwest Turkey, and L. formosana and L. acalycina occur in eastern Asia. This genus is one of many that contributes to the floristic similarities observed between these different regions. Allelic variation was scored at 22 isozyme loci from 41 populations. The level of genetic divergence between species on different continents is high. Nei's genetic identity was 0.431 between L. formosana and L. styraciflua, 0.485 between L. acalycina and L. styraciflua, 0.512 between L. orientalis and L. styraciflua, 0.256 between L. formosana and L. orientalis, and 0.305 between L. acalycina and L. orientalis. Estimates of time of divergence from the isozyme data suggest that the current species diverged before or during the Miocene. The pattern of relationships portrayed by the isozyme data suggest a longer period of separation between the eastern and western Asian forms of this genus. In addition, the eastern North American and Turkish species appear to be the most closely related intercontinental pair of species providing evidence for a North Atlantic land bridge as late as the Miocene. It would appear, therefore, that the North American populations were in contact with the Asian populations over the North Pacific and North Atlantic possibly as late as the Miocene, but that the separation between the two Asian populations occurred much earlier. The time of divergence as measured from the isozyme data correlates with an independent assessment of the origin of these disjuncts as determined from the fossil record.     

Phylogeographic analysis of a recent radiation of Enallagma damselflies (Odonata: Coenagrionidae)

A phylogenetic hypothesis revealed two recent radiations among species of Enallagma damselflies, and extensive ecological work suggests that both adaptive and nonadaptive processes are involved in these radiations. We analysed the geographical pattern of genetic variability at 868 bp of mitochondrial DNA (mtDNA) among 283 individuals of 5 species displaying little ecological differentiation to identify the ancestral lineage, support their independent evolutionary trajectories and identify historical events and the underlying mechanism for one of these radiations. Nested clade analysis results clearly support a past event of range fragmentation in E. hageni. These Atlantic and Continental hageni races experienced distinct dispersal histories and still maintain nearly nonoverlapping ranges All four other species derive from the Continental hageni. Whereas three species endemic to the Atlantic coastal plain show little genetic variation, E. ebrium shared several haplotypes with the Continental hageni. Contrasting levels of genetic differentiation between E. hageni and E. ebrium in geographical areas associated with distinct events of E. hageni's recent history support the recent origin of this species. Altogether, our results are compatible with a process of radiation via divergence in mate recognition systems within the Continental hageni race following secondary contacts between putative refugial races.     

Taxonomy and biogeography of the fiddler crabs (Ocypodidae: Genus Uca) of the Atlantic and Gulf coasts of eastern North America

Fifteen species of fiddler crabs are reported for eastern North America between Massachusetts and Quintana Roo, Mexico. Thirteen occur in the United States and 11 in Mexico, with eight in common to the two countries. Of 13 species in the Gulf of Mexico, five are endemic and a sixth is restricted largely to the peninsulas of Florida and Yucatan. The status of U. rapax in the northern Gulf remains to be resolved. Range limits of most species approximate one or the other of two sets of intersecting thermal and geological boundaries that subdivide the Gulf of Mexico along north-south and east-west axes. Species belonging to subgenus Minuca tend to replace one another at the thermally-controlled Carolinian-Caribbean marine biotic boundary across the Florida peninsula and northern Gulf. However, only U. minax of all the North American fiddler crabs exhibits the classical disjunct Carolinian distribution, and this appears basically to reflect the discontinuous distribution of temperate salt marshes that are the habitat of the species. Distributions of species belonging to subgenus Celuca adhere for the most part to the subdivision of the Gulf into western terrigenous and eastern carbonate sedimentary provinces. The northern transition occurs in the vicinity of Apalachee Bay and the southern at Laguna de Terminos. A third distributional pattern is shown by U. subcylindrica , a specialized endemic species of the hypersaline Laguna Madre system of the western Gulf. The level of endemism in the fiddler crabs is relatively high in comparison with that of other marine groups within the Gulf of Mexico. This may be a consequence of the adaptations of fiddler crabs as specialized deposit feeders to regional differences in climatic and edaphic characteristics of a marginally marine upper shore habitat. The distributional patterns of the endemics could prove useful in reconstructing palaeoecological events of evolutionary significance within the Gulf of Mexico.