Oceanography and reefs of recent and Paleozoic tropical epeiric seas

Summary The Java Sea, one of the few modern tropical epeiric seas, is used as an analogue to examine oceanography, stratigraphy, and reefs of Devonian strata in the Appalachian and Michigan Basins. Nearshore patch reefs and offshore “pinnacle” reefs occur in both the Java Sea and the Emsian-Eifelian Onondaga Formation in the Appalachian Basin. Nearshore patch reefs also occur in the Eifelian Formosa Reef Limestone in the Michigan Basin. The Java Sea is characterized by quasi-estuarine circulation, in which runoff and rainfall exceed evaporation. Nutrient and organic matter influx from land and from estuarine upwelling contribute to organic rich facies during transgressions and sea level highstands. Similarly, we propose that high runoff from the Appalachian Mountains and from the Laurentian craton contributed to slightly reduced salinity in the Appalachian basin, including possible density stratification during Middle Devonian highstands. By contrast, the Michigan Basin was characterized by antiestuarine circulation, in which evaporation exceeded combined runoff and rainfall. Contemporaneous Emsian-Eifelian strata in the Michigan Basin are dolomite and dolomitic limestone, rather than cherty and muddy limestone typical of the Appalachian basin. Reef composition generally reflects oceanographic circulation regime within the epicontinental seas we examine. Nearshore reefs of the modern Java Sea and the Onondaga Formation (Appalachian Basin) are dominated by multilobate submassive, dendroid, and phaceloid corals, and virtually no platy corals or tabular stromatoporoids. Multilobate and phaceloid corals are better able to accommodate muddy sedimentation. By contrast, offshore pinnacle reefs of the Java Sea and nearshore reefs of the Formosa Reef Limestone are dominated by platyAcropora (modern) or tabular and laminar stromatoporoids (Devonian). The scarcity of tabular stromatoporoids, and the dominance of phaceloid corals and dendritic branching corals, in the Onondaga Formation (Appalachian Basin) are herein explained by localized high productivity conditions driven by quasi-estuarine circulation, rather than cool water. Quasi-estuarine circulation or localized topographic upwelling leading to highly productive coastal environments may be responsible for other Paleozoic examples of apparent cool-water carbonate deposition within the tropics, including the Ordovician of Eastern Canada.     

Extinctions and migrations of Devonian rugose corals in the Eastern Americas Realm

Oliver, W. A., Jr. 1990 04 15: Extinctions and migrations of Devonian rugose corals in The Eastern Americas Realm. Lethaia , Vol. 23 , pp. 167–178. Oslo. ISSN 0024–1164.
Detailed plotting of the stratigraphic ranges of Devonian rugose coral genera within the Eastern Americas Realm reveals new information about the extinctions and migrations of this largely endemic fauna. There were significant faunal turnovers in the Lochkovian, middle Eifelian and late Givetian. as well as in the often discussed late Frasnian. The late Givetian turnover was nearly as great as the Frasnian one. Inward migration was principally from western North America, and the greatest influxes were during the carly Givetian and Frasnian. It seems likely that there were several separate incursions and that some genera were introduced to the east two, or even three times.     

Canary Grasses (Phalaris,Poaceae): biogeography,molecular dating and the role of floret structure in dispersal

Canary grasses (Phalaris, Poaceae) include 21 species, widely spread throughout the temperate and subtropical regions of the world with two centres of diversity: the Mediterranean Basin and western North America. The genus contains annual and perennial, endemic, cosmopolitan, wild, and invasive species with diploid, tetraploid and hexaploid cytotypes. As such, Phalaris presents an ideal platform to study diversification via historic hybridization and polyploidy events, and geographical dispersal in grasses. We present the first empirical phylogeographic study for Phalaris testing current, intuitive hypotheses on the centres of origin, historic dispersal events and diversification within a geological timeframe. Bayesian methods (beast , version 1.6.2) were used to establish divergence dates, and dispersal–vicariance analyses (rasp , version 2.1b) were implemented for ancestral node reconstructions. Our phylogeographic results indicate that the genus emerged during the Miocene epoch [20.6–8.4 Ma (million years ago)] in the Mediterranean basin followed by dispersal and vicariance events to Africa, Asia and the Americas. We propose that a diploid ancestor of P. arundinacea migrated to western North America via the Bering Strait, where further diversification emerged in the New World. It appears that polyploidy played a major role in the evolution of the genus in the Old World, while diversification in the New World followed a primarily diploid pathway. Dispersal to various parts of the Americas followed different routes. Fertile florets with hairy protruding sterile lemmas showed significant correlation with wider geographical distribution.     

Biogeographic history of the butterfly subtribe Euptychiina (Lepidoptera,Nymphalidae, Satyrinae)

Peña, C., Nylin, S., Freitas, A. V. L. & Wahlberg, N. (2010). Biogeographic history of the butterfly subtribe Euptychiina (Lepidoptera, Nymphalidae, Satyrinae).—Zoologica Scripta, 39, 243–258. The diverse butterfly subtribe Euptychiina was thought to be restricted to the Americas. However, there is mounting evidence for the Oriental Palaeonympha opalina being part of Euptychiina and thus a disjunct distribution between it (in eastern Asia) and its sister taxon (in eastern North America). Such a disjunct distribution in both eastern Asia and eastern North America has never been reported for any butterfly taxon. We used 4447 bp of DNA sequences from one mitochondrial gene and four nuclear genes for 102 Euptychiina taxa to obtain a phylogenetic hypothesis of the subtribe, estimate dates of origin and diversification for major clades and perform a biogeographic analysis. Euptychiina originated 31 Ma in South America. Early Euptychiina dispersed from North to South America via the temporary connection known as GAARlandia during Eocene–Oligocene times. The current disjunct distribution of the Oriental Palaeonympha opalina is the result of a northbound dispersal of a lineage from South America into eastern Asia via North America. The common ancestor of Palaeonympha and its sister taxon Megisto inhabited the continuous forest belt across North Asia and North America, which was connected by Beringia. The closure of this connection caused the split between Palaeonympha and Megisto around 13 Ma and the severe extinctions in western North America because of the climatic changes of the Late Miocene (from 13.5 Ma onwards) resulted in the classic ‘eastern Asia and eastern North America’ disjunct distribution.     

Morphometric Analysis of Sunflower (<Emphasis Type="Italic">Helianthus annuus</Emphasis> L.) Achenes from Mexico and Eastern North America<Superscript>1</Superscript>

Morphometric Analysis of Sunflower ( Helianthus annuus L.) Achenes from Mexico and Eastern North America. Sunflower (Helianthus annuus L.) has played a major role in the evolution of agricultural systems in the Americas. The discovery of ancient domesticated remains from archaeological deposits in pre-Columbian Mexico offers new dimensions to widely accepted viewpoints on the domestication pattern of H. annuus. Although American sunflower populations north of Mexico have been examined extensively, Mexican indigenous domesticated landraces have not been studied in any detail. In this study, we morphologically assessed wild and domesticated sunflower achenes from Mexico and compared them to similar datasets from eastern North America. Additionally, we evaluated the utility of four computer-assisted shape measurements in discriminating between wild and domesticated sunflower achenes (fruits) and compared variation in achene size among modern wild and cultivated populations from both Mexico and the U.S. We found that, of the shape parameters tested, none were informative in distinguishing wild achenes from domesticated varieties. Subsequent size analysis, using conventional parameters of length, width, and thickness, showed that modern wild populations from Mexico had smaller achenes compared to modern populations from eastern North America. Domesticated achenes unearthed from Mexican archaeological sites, however, were significantly larger than the early domesticated specimens recovered from eastern North America. Our methodological results indicate that variation in archaeological sunflower achenes is better described by conventional size parameters rather than computerized shape analysis.     

A new delthyridoid spiriferid genus from the Dra Valley, Morocco, and its phylogenetic affinities (Brachiopoda, Lower Devonian)

Multiplicatispirifer, a new delthyridoid brachiopod genus with a gently divergent capillate micro-ornamentation and bifurcating costae on flanks, sulcus and fold, has been identified in the Mdâouer-el-Kbîr Formation of the Dra Valley (southern Anti-Atlas, Morocco). Its type speciesMultiplicatispirifer foumzguidensis n. gen., n. sp., at present the only species of this genus, is described. This form has hitherto been determined asFimbrispirifer orStruveina by various authors. In this work, the new genus is compared with the multiplicate and capillate spiriferid genera with bifurcating costae which also have costae in the sulcus and on the fold:Costispirifer andPerryspirifer from North America,Elymospirifer from South China,Borealispirifer from Asia andMultispirifer from Central Europe. The relation ofMultiplicatispirifer to the fimbriateFimbrispirifer, Struveina andVandercammenina, from which it is distinguished by its capillate micro-ornamentation, is discussed. The new genus is hitherto only known from the Moroccan southern Anti-Atlas. Its colsest relatives, taxa ofCostispirifer, occur in the Eastern American Realm (Gaspé, Canada and the eastern United States) and the Nevada Province (western United States).Multiplicatispirifer occurrences are restricted to the Lower/Upper Emsian boundary interval (upper Lower Devonian). The reasons for a possible migration corridor between North America and North Africa before Emsian time are discussed.     

Biogeographical and geological evidence for a smaller, completely-enclosed Pacific Basin in the Late Cretaceous

Aim To use biogeographical, palaeomagnetic, palaeosedimentary, and plate circuit data from Late Cretaceous regions in and around the Pacific to test the plate tectonic hypothesis of a pre‐Pacific superocean. Location East Asia, Australia, Antarctica, the western Americas, and the Pacific. Methods Literature surveys of the distributions of Cretaceous, circum‐Pacific taxa were compared with palaeomagnetic and palaeosedimentary data. Uncontroversial plate motions based on seafloor spreading data were also used to test the results of the biogeographical and palaeomagnetic analyses. Results The distributions of Cretaceous terrestrial taxa, mostly dinosaurs, imply direct, continental connections between Australia and East Asia, East Asia and North America, North America and South America, South America and Antarctica, and Antarctica and Australia. Palaeomagnetic, palaeosedimentary, and basic plate circuit analyses require little to no latitudinal motion of the Pacific plate with respect to the surrounding continents. Specifically, the data implies that western North America, East Asia, and the Pacific plate all increased in latitude by roughly the same amount (c. 11 ± 5°) since the Campanian – and that the Pacific Ocean Basin has increased in length north‐to‐south. Main conclusions Each of the analyses provides independent corroboration for the same conclusion: the Late Cretaceous Pacific plate was completely enclosed by the surrounding continents and has not experienced significant latitudinal motion with respect to North America, East Asia, or the Bering land bridge. This contrasts significantly with the plate tectonic history of the Pacific, implying instead that the Pacific plate formed in situ, pushing the continents apart as the plate and basin expanded. These results also substantiate recent biogeographical analyses that have concluded that a narrower Pacific Ocean Basin in the Mesozoic and early Tertiary provides the most reasonable explanation for the great number of trans‐Pacific disjunctions of poor dispersing taxa.     

Palaeobiogeography of late cretaceous belemnites of Europe

A North Temperate Realm, characterized by Belemnitellidae Pavlov, and a South Temperate Realm, characterized by Dimitobelidae WHITEHOUSE, existed throughout the Late Cretaceous, while Tethyan belemnites belonging to Belemnopseidae Naef existed only in the Cenomanian and disappeared afterwards. The North Temperate Realm may be subdivided into North European and North American Provinces. The latter province includes Greenland, Canada, the Western Interior Region of North America, and the Atlantic and Gulf coasts of North America. The belemnites from the North American Province, consisting of populations of the generaActinocamax Miller andBelemnitella d’Orbigny, are closely related to the belemnites of the North European Province and appear to have migrated from this province to North America via Greenland and Arctic Canada. The North European Province extends from Ireland to the Ural Mountains. Belemnites from this province belong to the following genera:Neohibolites Stolley,Parahibolites Stolley,Belemnocamax Crick,Actinocamax Miller,Belemnellocamax Naidin,Gonioteuthis Bayle,Belemnitella d’Orbigny,Belemnella Nowak, andFusiteuthis Kongiel. Two subprovinces within the North European Province have been recognized: the Central European and Central Russian Subprovinces. These subprovinces are well-defined in the late Coniacian-Early Campanian and are characterized by theGonioteuthis stock andBelemnitella stock, respectively. The two subprovinces are less distinct in other periods of the Late Cretaceous and may disappear completely.     

Carbonate breccias in the lower-middle Ordovician Maggol Limestone (Taebacksan Basin,South Korea): Implications for regional tectonism

Summary Carbonate breccias occur sporadically in the Lower-Middle Ordovician Maggol Limestone exposed in the Taebacksan Basin, South Korea. These carbonate breccias have been previously interpreted as intraformational or fault breccias. Thus, little attention has been focused on tectonic and stratigraphic significance of these breccias. This study, however, indicates that the majority of these breccias are solution-collapse breccias, which are causally linked to paleokarstification. Carbonate facies analysis in conjunction with conodont biostratigraphy suggests that an overall regression toward the top of the Maggol Limestone probably culminated in subaerial exposure of platform carbonates during the early Middle Ordovician. Extensive subaerial exposure of platform carbonates resulted in paleokarst-related solution-collapse breccias in the upper maggol Limestone. This subaerial exposure event is manifested as a major paleokarst unconformity elsewhere beneath the Middle Ordovician sequence, most notably North America and North China. Due to its global extent, the early Middle ordovician paleokarst unconformity (‘the Sauk-Tippecanoe sequence boundary’) has been viewed as a product of second-order eustatic sea level drop during the early Middle Ordovician. Although we recognizes a paleokarst breccia zone in the upper Maggol Limestone beneath the Middle Ordovician sequence, the early Middle Ordovician sequence boundary appears to be a conformable transgressive surface or a drowning unconformity, rather than a major paleokarst unconformity. The paleokarst breccia zone in the upper Maggol Limestone is represented by a thinning-upward stack of exposure-capped tidal flat-dominated cycles that are closely associated with multiple occurrences of paleokarst-related solution-collapse breccias. The paleokarst breccia zone in the upper Maggol Limestone was a likely consequence of repeated high-frequency sea level fluctuations of fourth- and fifth-order superimposed on a second-and third-order eustatic fall in sea level that was less than the rate of tectonic subsidence across the platform. It suggests that second- and thirdorder eustatic sea level drop may have been significantly tempered by substantial tectonic subsidence near the end of maggol deposition. The tectonic subsidence in the basin is also evidenced by the occurrence of coeval off-platform lowstand siliciclastic quarzite lenses as well as debris flow carbonate breccias. With the continued tectonic subsidence, subsequent rise in the eustatic cycle caused drowning and deep flooding of carbonate platform, forming a conformable transgressive surface or a drowning unconformity on the top of the paleokarst breccia zone. This tectonic implication contrasts notably with the slowly subsiding carbonate platform model for the Taebacksan Basin as previously intepreted. Here we propose that the Taebacksan Basin evolved from a slowly subsiding carbonate platform to a rapidly subsiding intracontinental rift basin during the early Middle Ordovician. This study also provides a good example that the falling part of the eustatic sea-level cycle may not produce a significant event at all in a rapidly subsiding basin where the rate of eustatic fall always remained lower than the rate of subsidence.     

A review of vital rates and cause‐specific mortality of elk Cervus elaphus populations in eastern North America

相似文献   

A new hadrosaurid dentary from the latest Maastrichtian of the Pyrenees (north Spain) and the high diversity of the duck-billed dinosaurs of the Ibero-Armorican Realm at the very end of the Cretaceous

In the latest Maastrichtian, the European hadrosauroid fauna was more diverse than those of North America and Asia. The European record of hadrosaurid dentaries is an example of this diversity, and most of the sites with mandibular remains are located in the Ibero-Armorican Realm. Within the Iberian Peninsula, most of the remains are located in the Tremp Basin (South Central Pyrenees). Two of the three valid hadrosaurid taxa defined in this basin are from the Blasi sites (Arén, Huesca province): Arenysaurus ardevoli (Blasi-3) and Blasisaurus canudoi (Blasi-1). A new locality in Blasi (Blasi 3.4) has provided a new dentary from an indeterminate euhadrosaurid. This dentary presents some characters intermediate between Arenysaurus and Blasisaurus, some characters similar to Pararhabdodon isonensis (from the nearby province of Lleida), and some characters of its own. Nevertheless, due to its fragmentary character, without dentition or its edentulous anterior part, it cannot be determined above the level of Euhadrosauria. It thus represents a fourth Iberian euhadrosaurian taxon in the Ibero-Armorican Realm, different from Arenysaurus, Blasisaurus and Pararhabdodon, increasing the diversity of hadrosauroids in this realm at the very end of the Cretaceous.     

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.     

Ordovician conodont biogeography – reconsidered

Review of the traditional separation of global Ordovician conodont distribution into the North American Midcontinent Province (NAMP) and North Atlantic Province (NAP) reveals a confusing variety of concepts and definitions that hinder biogeographic analysis. Use of this twofold scheme and its subsequent variants should be­discontinued in favour of the more detailed divisions proposed here. Major biogeographical entities of the Shallow-Sea and Open-Sea Realms, separated by the shelf-slope break, are both further subdivisible into Tropical, Temperate and Cold Domains. In the Cold domains, faunal differences between the two Realms and their subdivisions are not easily discernible, since biofacies zones and different habitats were highly condensed. Faunal differences are amplified in the tropical regions, where the North American Midcontinent Province and North Atlantic Province were originally defined. Recognition of endemic taxa is essential for finer classification within domains of the Shallow-Sea Realm (SSR). Our preliminary analysis of Early Ordovician conodont distribution identifies the Laurentian Province (in the Tropical Domain), Australian­(Tropical Domain), North China (Tropical Domain), South China (Temperate Domain), Argentine Precordillera (Temperate Domain) and Balto-Scandian Province (in the Cold Domain). The Open-Sea Realm (OSR) is dominated by cosmopolitan and widespread taxa, and formal subdivision at provincial level is yet to be achieved. The North Atlantic Province encompasses both the Open-Sea Realm and the Temperate and Cold Domains of the Shallow-Sea Realm. The North American Midcontinent Province sensu stricto is more or less equivalent to the Laurentian Province, representing shallow-water regions fringing Laurentia; in a broader sense the North American Midcontinent Province includes all provinces of the Tropical Domain within the Shallow-Sea Realm.     

A discovery of the genus <Emphasis Type="Italic">Cabrieroceras</Emphasis> (Werneroceratidae,Ammonoidea) in Salair

The ammonoid genus Cabrieroceras Bogoslovsky is recorded for the first time from the Eifelian of Salair (from the Safonovo Horizon). These ammonoids date the host rocks as the Cabrieroceras crispiforme Zone, recognized in many sections in Western Europe, North America, and North Africa. The taxonomy of the genus Cabrieroceras is discussed, and a new species, C. salairicum Nikolaeva, is described.     

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.

     

Strontium stratigraphy of the Burdigalian transgression in the Western Mediterranean

Brandano, M. & Policicchio, G. 2011: Strontium stratigraphy of the Burdigalian transgression in the Western Mediterranean. Lethaia, Vol. 45, pp. 315–328. A ⁸⁷Sr/⁸⁶Sr analysis of selected pectinid shells has been performed to refine the stratigraphical framework of the Burdigalian transgressive event. Samples were collected from shallow water successions of the Western Mediterranean area (North‐Eastern Sardinia, Southern Corsica, Central Apennines). The Western Mediterranean is the result of the interaction between the European and the African plates. Sardinia and Corsica were extended and rifted apart from the Iberian Peninsula during the opening of the Liguro‐Provencal basin, between 30 and 15 Ma. In the outcrops of Northern Sardinia and Southern Corsica, Burdigalian deposits nonconformably overlie Varisican granites. In the central Apennines the Burdigalian deposits paraconformably overlie the Cretaceous platform. These are transgressive deposits, characterized by the presence of Miogypsina globulina, which points out early to middle Burdigalian age. The Sr isotope ages indicate that marine transgression in Northern Sardina and Southern Corsica took place between 18.6 and 18.3 Ma, which could correspond to the eustatic sea level rise of the Bur3 third‐order sequence. In the Central Apennines the Burdigalian transgression was anticipated (18.8 Ma) by subsidence input linked to the eastward migration of the orogenic system. This input allowed the Miocene carbonate ramp to develop on the Cretaceous platform substrate, while successive eustatic rise controlled the evolution of the stratigraphical architecture. The following regressive phase is recorded in both the Apennine and Corsica successions. The end of this phase is dated between 17.6 and 17.5 Ma and corresponds to sea level drop corresponding to the occurrence of the Mi 1b event. □Burdigalian, pectinids, strontium stratigraphy, transgression, Western Mediterranean     

Stratigraphy, geometry, and facies of a Middle Devonian ramp-to-basin transect (Eastern Anti-Atlas, SE Morocco)

Summary In the castern Anti-Atlas (SE Morocco), a small sedimentary basin (Mader Basin) evolved during the late Palacozoic. The Middle Devonian deposits consist of shales and limestones with a thickness up to 700 m in the depocentre. Sedimentary structures and sole marks of Middle Devonian limestones indicate transport from the northwest and the south towards the basin centre, located in the central Mader area. Lithostratigraphic, biostratigraphic, and dynamic stratigraphic approaches were applied to correlate stratigraphic sections. Five correlatable large-scale base-level hemicycles were recognized in the Middle Devonian succession. Thickness trends of Middle Devonian deposits, regional correlations, and facies-trends reveal the geometry of a carbonate ramp. The carbonate ramp was slightly inclined (<1°) to the NE. A sedimentary wedge, consisting of limestones and limestone/marl alternations, was deposited during the Eifelian and marks the transition from the ramp to the adjacent basin. Middle Devonian water depths are estimated as close to and within the storm wave-base at the southern area of the ramp and far below storm wave-base in the northeastern part of the ramp. Shallowest conditions (inner-ramp environment), close or within the fairweather wave-base, existed during the early Givetian as documented by the abundance of recfal fauna (stromatoporoids, corals) and calcimicrobes (lumps, micritic envelopes) in the eastern and southeastern area of the ramp.     

Carboniferous biogeography of the bryozoan Archimedes in North America

The fenestrate bryozoan genus Archimedes apparently originated and then diversified in Early Carboniferous seas of eastern North America. Its highest species richness and greatest abundance are reached in uppermost Lower to lowest Upper Carboniferous (Chesterian) rocks of eastern North America. Following the unconformity that marks the mid‐Carboniferous eustatic event, however, it is known in North America only in Upper Carboniferous basinal deposits of the Oquirrh Mountains and in nearby regions of Utah and Nevada. It is hypothesized that Archimedes’ life‐history patterns caused the biogeographical change: dependence on fragmentation as a means of recruitment did not allow Archimedes to keep up with its rapidly migrating preferred back‐barrier environment during the numerous eustatic transgressive and regressive cycles that caused the shoreline to sweep across North America during the Late Carboniferous. The persistence of Archimedes in the Oquirrh Basin and vicinity is inferred to have resulted from its preferred back‐barrier environment migrating only locally along the relatively steep basinal slope present there during the Late Carboniferous eustatic cycles.     

INTRASPECIFIC PHYLOGEOGRAPHY OF NORTH AMERICAN HIGHLAND FISHES: A TEST OF THE PLEISTOCENE VICARIANCE HYPOTHESIS

The highland fish fauna of eastern North America consists of Appalachian and Ozark centers of endemism separated by the intervening Glacial Till Plains. Clades within these areas are more closely related phylogenetically to each other than to clades occurring in the intervening formerly glaciated region, suggesting that the Pleistocene glaciations fragmented a widespread highland region and its associated fauna. Alternatively, it is possible that these faunal assemblages predate the glaciations or that recent dispersals may have been more important than vicariance in determining faunal compositions. We examined the relationships among mitochondrial DNA (mtDNA) haplotypes within five clades of highland fishes, each with a distribution suggestive of a Pleistocene vicariance event. Darters of the subgenera Litocara and Odontopholis have distributions and mtDNA relationships that are consistent with the Pleistocene integration and burial of the Teays-Mahomet valley, a major drainage of the early Pleistocene. The distribution and mtDNA relationships among subspecies of Erimystax dissimilis are not consistent with Pleistocene vicariance, but relationships among Appalachian haplotypes are consistent with the late Pleistocene integration of the modern Ohio River system. Both Cottus carolinae and the Fundulus catenatus species group have representatives in the Mobile basin consistent with pre-Pleistocene divergences. Three haplotype clusters were found in C. carolinae, corresponding to the Appalachian, Ozark, and upper Kanawha River populations. However, Appalachian and Ozark F. catenatus populations are paraphyletic with respect to each other. This, coupled with a relatively low degree of sequence divergence, suggests that no long-term barriers to gene flow exist for C. carolinae and F. catenatus. These three distinct phylogeographic patterns indicate that Pleistocene vicariance is not the only explanation for the Appalachian-Ozark distribution of highland fish communities.     

A rangewide herbarium‐derived dataset indicates high levels of gene flow in black cherry (Prunus serotina)

Isolation by Distance (IBD) is a genetic pattern in which populations geographically closer to one another are more genetically similar to each other than populations which are farther apart. Black cherry (Prunus serotina Ehrh.) (Rosaceae) is a forest tree species widespread in eastern North America, and found sporadically in the southwestern United States, Mexico, and Guatemala. IBD has been studied in relatively few North American plant taxa, and no study has rigorously sampled across the range of such a widespread species. In this study, IBD and overall genetic structure were assessed in eastern black cherry (P. serotina Ehrh. var. serotina), the widespread variety of eastern North America. Eastern North America. Prunus serotina Ehrh. var. serotina (Rosaceae). Dense sampling across the entire range of eastern black cherry was made possible by genotyping 15 microsatellite loci in 439 herbarium samples from all portions of the range. Mantel tests and STRUCTURE analyses were performed to evaluate the hypothesis of IBD and genetic structure. Mantel tests demonstrated significant but weak IBD, while STRUCTURE analyses revealed no clear geographic pattern of genetic groups. The modest geographic/genetic structure across the eastern black cherry range suggests widespread gene flow in this taxon. This is consistent with P. serotina's status as a disturbance‐associated species. Further studies should similarly evaluate IBD in species characteristic of low‐disturbance forests.