Changes in genetic structure of North American Bythotrephes populations following invasion from Lake Ladoga, Russia

1. We used allozyme electrophoresis to compare Bythotrephes longimanus (Crustacea: Onychopoda: Cercopagididae) from recently founded North American populations with those from native European populations, and to examine changes in genetic structure of North American populations over time.
2. The genetic structure of North American populations in 1996 was similar to that of European populations, because of the disappearance of founder effects which distinguished North American from European populations in 1989.
3. The Lake Ladoga, Russia population was more closely related to North American populations than to other European populations, consistent with non-genetic evidence implicating Lake Ladoga as the source of North American populations.
4. Our results provide additional evidence of the presence of an invasion corridor that allows Urasian and Ponto-Caspian species to be introduced into North American freshwater ecosystems, and show that founder effects can erode over time following establishment of invasive species.     

Allelopathic inhibition of germination by Alliaria petiolata (Brassicaceae)

Garlic mustard (Alliaria petiolata, Brassicaceae) is an invasive, nonindigenous species currently invading the understory of North American woodlands where it is a serious threat to the native flora. Part of this success might be due to allelopathic interference by garlic mustard. Two congeneric species, the European Geum urbanum and the North American Geum laciniatum, were tested for allelopathic inhibition of germination by garlic mustard. Seeds were germinated either on substrate contaminated by garlic mustard or on substrate with contamination neutralized by activated carbon. Allelopathic effects of native European and invasive North American garlic mustard populations were also compared. Activated carbon increased germination by 14%, indicating that garlic mustard contaminated the substrate through root exudates. Activated carbon in turn counteracted this effect. The two test species differed in their sensitivity to allelopathic interference. North American G. laciniatum had a much stronger increase in germination when activated carbon was added to the substrate, independent of the origin of garlic mustard. In contrast, the European G. urbanum germinated better in substrate precultivated with North American garlic mustard, whereas activated carbon increased its germination only in substrate precultivated with European garlic mustard.     

Tissue Residue Guideline for ∑DDT for Protection of Aquatic Birds in China

DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) is a chlorinated hydrocarbon insecticide that has been used worldwide. While the use of DDT has been phased out in many countries, it is still produced in some parts of the world for use to control vectors of malaria. DDE (1,1,-dichloro-2,2-bis(p-chlorophenyl)ethylene) and DDD (1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) are primary metabolites of DDT and have similar chemical and physical properties. DDT and its metabolites (DDE and DDD) are collectively referred to as ∑DDT. The lipophilic nature and persistence of the ∑DDT result in biomagnification in wildlife that feed at higher trophic levels in the food chain. Wildlife in aquatic ecosystems depend on aquatic biota as their primary source of food, which provide the main route of exposure to ∑DDT. Studies about effects of ∑DDT on birds were reviewed. The tissue residue guidelines for DDT (TRGs) for protection of birds in China were derived using species sensitivity distribution (SSD) and toxicity percentile rank method (TPRM) based on the available toxicity data. Risks of ∑DDT to birds were assessed by comparing the TRGs and ∑DDT concentrations in fishes from China. The tissue residue guideline for protection of birds in China is recommended to be 12.0 ng ∑DDT/g food.     

Effects of sex and sampling site on the relative proportion of pesticides in uropygial gland secretions of European Blackbirds (Turdus merula)

Dichlorodiphenyltrichloroethane (DDT) is a pesticide that was commonly used for decades worldwide. The use of DDT was banned in the 1970s and 1980s in Europe because of its high toxicity and persistence in the environment, bioaccumulation in living organisms and biomagnification through food webs. However, monitoring using both invasive and non-invasive methods has routinely reported the occurrence of DDT metabolites such as dichlorodiphenyldichloroethylene (DDE) in wild birds, providing valuable information about the exposure to pesticides and potential differences between species and over time. Here, we analysed the relative proportion of DDE in the uropygial gland secretions of European Blackbirds Turdus merula from two localities in southern Spain. Given the negative effects of this pollutant on animal immunity, we also tested for associations between the prevalence of haemosporidians and the relative proportion of DDE in their secretions. Relative proportions of DDE varied between sampling sites and were higher in females than in males, regardless of their age. In spite of the potential immunosuppressive effect of DDE, haemosporidian infection was not associated with DDE presence.     

High migration rates shape the postglacial history of amphi‐Atlantic bryophytes

Paleontological evidence and current patterns of angiosperm species richness suggest that European biota experienced more severe bottlenecks than North American ones during the last glacial maximum. How well this pattern fits other plant species is less clear. Bryophytes offer a unique opportunity to contrast the impact of the last glacial maximum in North America and Europe because about 60% of the European bryoflora is shared with North America. Here, we use population genetic analyses based on approximate Bayesian computation on eight amphi‐Atlantic species to test the hypothesis that North American populations were less impacted by the last glacial maximum, exhibiting higher levels of genetic diversity than European ones and ultimately serving as a refugium for the postglacial recolonization of Europe. In contrast with this hypothesis, the best‐fit demographic model involved similar patterns of population size contractions, comparable levels of genetic diversity and balanced migration rates between European and North American populations. Our results thus suggest that bryophytes have experienced comparable demographic glacial histories on both sides of the Atlantic. Although a weak, but significant genetic structure was systematically recovered between European and North American populations, evidence for migration from and towards both continents suggests that amphi‐Atlantic bryophyte population may function as a metapopulation network. Reconstructing the biogeographic history of either North American or European bryophyte populations therefore requires a large, trans‐Atlantic geographic framework.     

Molecular phylogeny and historical biogeography of the Holarctic wetland leaf beetle of the genus Plateumaris

Leaf beetles of the genus Plateumaris inhabit wetlands across the temperate zone of the Holarctic region. To explore the phylogeographic relationships among North American, East Asian, and European members of this genus and the origin of the species endemic to Japan, we studied the molecular phylogeny of 20 of the 27 species in this genus using partial sequences of mitochondrial cytochrome oxidase subunit I (COI) and the 16S and nuclear 28S rRNA genes. The molecular phylogeny revealed that three species endemic to Europe are monophyletic and sister to the remaining 11 North American and six Asian species. Within the latter clade, North American and Asian species did not show reciprocal monophyly. Dispersal-vicariance analysis and divergence time estimation revealed that the European and North America-Asian lineages diverged during the Eocene. Moreover, subsequent differentiation occurred repeatedly between North American and Asian species, which was facilitated by three dispersal events from North America to Asia and one in the opposite direction during the late Eocene through the late Miocene. Two Japanese endemics originated from different divergence events; one differentiated from the mainland lineage after differentiation from the North American lineage, whereas the other showed a deep coalescence from the North American lineage with no present-day sister species on the East Asian mainland. This study of extant insects provides molecular phylogenetic evidence for ancient vicariance between Europe and East Asia-North America, and for more recent (but pre-Pleistocene) faunal exchanges between East Asia and North America.     

Extended phylogeny of Aquilegia: the biogeographical and ecological patterns of two simultaneous but contrasting radiations

Studies of the North American columbines (Aquilegia, Ranunculaceae) have supported the view that adaptive radiations in animal-pollinated plants proceed through pollinator specialisation and floral differentiation. However, although the diversity of pollinators and floral morphology is much lower in Europe and Asia than in North America, the number of columbine species is similar in the three continents. This supports the hypothesis that habitat and pollinator specialisation have contributed differently to the radiation of columbines in different continents. To establish the basic background to test this hypothesis, we expanded the molecular phylogeny of the genus to include a representative set of species from each continent. Our results suggest that the diversity of the genus is the result of two independent events of radiation, one involving Asiatic and North American species and the other involving Asiatic and European species. The ancestors of both lineages probably occupied the mountains of south-central Siberia. North American and European columbines are monophyletic within their respective lineages. The genus originated between 6.18 and 6.57 million years (Myr) ago, with the main pulses of diversification starting around 3 Myr ago both in Europe (1.25–3.96 Myr ago) and North America (1.42–5.01 Myr ago). The type of habitat occupied shifted more often in the Euroasiatic lineage, while pollination vectors shifted more often in the Asiatic-North American lineage. Moreover, while allopatric speciation predominated in the European lineage, sympatric speciation acted in the North American one. In conclusion, the radiation of columbines in Europe and North America involved similar rates of diversification and took place simultaneously and independently. However, the ecological drivers of radiation were different: geographic isolation and shifts in habitat use were more important in Europe while reproductive isolation linked to shifts in pollinator specialisation additionally acted in North America.     

Novel weapons and invasion: biogeographic differences in the competitive effects of Centaurea maculosa and its root exudate (±)-catechin

Recent studies suggest that the invasive success of Centaurea maculosa may be related to its stronger allelopathic effects on native North American species than on related European species, one component of the “novel weapons” hypothesis. Other research indicates that C. maculosa plants from the invasive range in North America have evolved to be larger and better competitors than conspecifics from the native range in Europe, a component of the “evolution of increased competitive ability” hypothesis. These hypotheses are not mutually exclusive, but this evidence sets the stage for comparing the relative importance of evolved competitive ability to inherent competitive traits. In a competition experiment with a large number of C. maculosa populations, we found no difference in the competitive effects of C. maculosa plants from North America and Europe on other species. However, both North American and European C. maculosa were much better competitors against plants native to North America than congeners native to Romania, collected in areas where C. maculosa is also native. These results are consistent with the novel weapons hypothesis. But, in a second experiment using just one population from North America and Europe, and where North American and European species were collected from a broader range of sites, competitive interactions were weaker overall, and the competitive effects of C. maculosa were slightly stronger against European species than against North American species. Also consistent with the novel weapons hypothesis, (±)-catechin had stronger effects on native North American species than on native European species in two experiments. Our results suggest that the regional composition of the plant communities being invaded by C. maculosa may be more important for invasive success than the evolution of increased size and competitive ability. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Molecular evidence for an Asian origin and a unique westward migration of species in the genus Castanea via Europe to North America

The genus Castanea (Fagaceae) is widely distributed in the deciduous forests of the Northern Hemisphere. The striking similarity between the floras of eastern Asia and those of eastern North America and the difference in chestnut blight resistance among species has been of interest to botanists for a century. To infer the biogeographical history of the genus, the phylogeny of Castanea was estimated using DNA sequence data from different regions of the chloroplast genome. Sequencing results support the genus Castanea as a monophyletic group with Castanea crenata as basal. The three Chinese species form a strongly supported sister clade to the North American and European clade. A unique westward expansion of extant Castanea species is hypothesized with Castanea originating in eastern Asia, an initial diversification within Asia during the Eocene followed by intercontinental dispersion and divergence between the Chinese and the European/North American species during the middle Eocene and a split between the European and the North American species in the late Eocene. The differentiation within North America and China might have occurred in early or late Miocene. The North America species are supported as a clade with C. pumila var. ozarkensis, the Ozark chinkapin, as the basal lineage, sister to the group comprising C. pumila var. pumila, the Allegheny chinkapin, and Castanea dentata, the American chestnut. Morphological evolution of one nut per bur in the genus may have occurred independently on two continents.     

Phylogenetic placement and biogeography of the North American species of Valerianella (Valerianaceae: Dipsacales) based on chloroplast and nuclear DNA

Although Valerianaceae is a relatively small group of angiosperms (ca. 350 species), sample sizes of previous phylogenetic studies have been limited and taxonomic sampling has been usually geographically biased to species from Europe and/or South America. One group that has never been included in any analyses to date is the North American representatives of Valerianella. In this study I sampled 17 additional accessions from Valerianaceae, including six of the 12 described North American Valerianella species and four additional samples of European Valerianella species. Phylogenies based on parsimony and Bayesian methods show strong support for placing the North American Valerianella nested within the European species. These analyses also found Fedia to be nested within Valerianella, making Valerianella paraphyletic, a result consistent with several previously published molecular phylogenies. Divergence times estimated from the molecular data using recently proposed Bayesian 'relaxed' clock methods, suggest Valerianella was in North America by the middle Miocene (ca. 16-14 million years ago). These dates would suggest the North American species of Valerianella arrived in the New World just prior to the North Atlantic land bridge (NALB) no longer being a viable conduit for migration. Given the large amount of uncertainty in the divergence time estimates, dispersal across the North Atlantic may not be the only viable alternative to explain the current distribution of Valerianella. However, biogeographic analyses using an explicit model based approach, strongly favor the NALB as the route of dispersal for Valerianella.     

Revision of the larvae of Leptus Latreille (Acarina: Erythraeidae) of Europe and North America, with descriptions of post-larval instars

The larvae of Leptus Latreille, 1796 (Acarina: Erythraeidae) of Europe and North America are comprehensively revised. Of those described since 1900 a total of 34 species is considered recognizable and capable of being keyed; no species described before 1900 is considered recognizable. The nominal type of the genus, Acarus phalangii de Geer, 1778 is rejected as an illegitimate name. Eighteen European and 17 North American species are described and keyed, of which 17 are new to science. One new subspecies from North America, of a species previously known from Europe, is described and keyed. Standard metric data are given for each species or subspecies from available specimens (except two North American species, L. ariel Southcott and L. clarki Southcott, recently described elsewhere; for these last-named two additional metric data are given). Larvae have been recorded from April to September, with the greatest number found being for July and August.
Protonymphs are described for two North American species ( L. ghiradellae sp. nov. and L. welbourni sp. nov. ), and deutonymphs for two North American species ( L. calix sp. nov. and L. ghiradellae ). Keys are given to separate the reared protonymphs, and three described deutonymphs (the two preceding and the European L. galerucae Feider). Data on the duration of the protonymphal instar suggest that in North America and Europe there are two modes: one lasting 3–4 weeks, the other 5–7 months. Developmental abnormalities are recorded systematically.     

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。     

Genetic evidence suggests a widespread distribution of native North American populations of reed canarygrass

Reed canarygrass is an important agricultural crop thought to be native to Europe, Asia, and North America. However, it is one of the worst wetland invaders in North American wetlands. The native North American status has been supported by the circumstantial evidence of early botanical records and the dating and location of herbarium specimens. The lack of empirical evidence has left the North American native status of the species in doubt and prevented comparisons between native North American and Eurasian populations of the species. We utilized genetic markers to compare a wide range of European and Asian collections to DNA extracted from 38 early North American herbarium specimens. The genetic data confirm the presence of a distinct population present throughout North America in the early twentieth century, but not present in Europe or Asia, ranging from Alaska, USA to New Brunswick, Canada. These native North American populations of reed canarygrass are likely present throughout Alaska today, as one specimen was collected as recently as 1996, and may still be present in other regions of North America. Future research can utilize this dataset to determine the origin of present-day invasive populations in North American wetlands.     

DIFFERENCES IN THE CALLS OF EUROPEAN AND NORTH AMERICAN BLACK-BILLED MAGPIES AND THE YELLOW-BILLED MAGPIE

ABSTRACT

We compared several features of the chatter call of two races of black-billed magpies, the nominate, European race Pica pica pica and the North American race P.p. hudsonia and the yellow-billed magpie P. nuttalli. The chatter calls of the two North American species were much more similar to each other than either was to the European magpie. This information together with the recently determined similarities in the behaviour and social organisation of the two North American species, suggests that the phylogenetic affinities of these two species are closer than is implied by their taxonomic status.     

Comparative phylogeography of the Veronica alpina complex in Europe and North America

The Veronica alpina complex comprises eight species of alpine habitats over a wide range of mountain systems in the Northern Hemisphere. The occurrence of sympatric species in the European and North American mountain systems allowed us not only to investigate the effect of the ice ages on intraspecific phylogeographical patterns and genetic diversity in different continents of the Northern Hemisphere, but also to compare these patterns in closely related species. Plastid DNA trnL-F sequences and AFLP (amplified fragment length polymorphism) fingerprints were used to infer the phylogenetic history of the group and phylogeographical patterns within species. Hybrid origin of tetraploid eastern North American V. wormskjoldii from western North American V. nutans (= V. wormskjoldii s.l.) and Eurasian V. alpina is suggested. A number of phylogeographical groups have been found both in V. alpina from Europe and in V. nutans from western North America. Phylogeographical substructuring in the Alps is inferred for V. alpina but not for V. bellidioides, which is moreover characterized by an overall very low genetic diversity. Western North American V. cusickii is much more genetically diverse than its sympatric relative, V. nutans, an effect that is likely due to differences in the breeding system. Populations of V. nutans are differentiated into three groups, those from the Cascades and from the southern and the northern Rocky Mountains. Genetic diversity seems to be higher in the North American V. nutans than in the morphologically and ecologically similar European V. alpina. A possible scenario to explain this pattern is suggested.     

From Europe to America: pliocene to recent trans-atlantic expansion of cold-water north atlantic molluscs

Data on the geographical distribution, phylogeny and fossil record of cool-temperate North Atlantic shell-bearing molluscs that live in waters shallower than 100 m depth belong to two biogeographic provinces, one in eastern North America north of Cape Cod, the other in northern Europe. Amphi-Atlantic species, which are found in both provinces, comprise 30.8% of the 402 species in the northeastern Atlantic and 47.3% of the 262 species in the northwestern Atlantic. Some 54.8% of these amphi-Atlantic species have phylogenetic origins in the North Pacific. Comparisons among fossil Atlantic faunas show that amphi-Atlantic distributions became established in the Middle Pliocene (about 3.5 million years ago), and that all represent westward expansions of European taxa to North America. No American taxa spread eastward to Europe without human assistance. These results are in accord with previous phylogeographic studies among populations within several amphi-Atlantic species. Explanations for the unidirectional expansion of species across the Atlantic remain uncertain, but may include smaller size and greater prior extinction of the North American as compared to the European fauna and biased transport mechanisms. Destruction of the European source fauna may jeopardize faunas on both sides of the Atlantic.     

Origin and evolution of North American polyploid Silene (Caryophyllaceae)

Nuclear DNA sequences from introns of the low-copy nuclear gene family encoding the second largest subunit of RNA polymerases and the ribosomal internal transcribed spacer (ITS) regions, combined with the psbE-petL spacer and the rps16 intron from the chloroplast genome were used to infer origins and phylogenetic relationships of North American polyploid Silene species and their closest relatives. Although the vast majority of North American Silene species are polyploid, which contrasts to the diploid condition dominating in other parts of the world, the phylogenetic analyses rejected a single origin of the North American polyploids. One lineage consists of tetraploid Silene menziesii and its diploid allies. A second lineage, Physolychnis s.l., consists of Arctic, European, Asian, and South American taxa in addition to the majority of the North American polyploids. The hexaploid S. hookeri is derived from an allopolyploidization between these two lineages. The tetraploid S. nivea does not belong to any of these lineages, but is closely related to the European diploid S. baccifera. The poor resolution within Physolychnis s.l. may be attributed to rapid radiation, recombination among homoeologues, homoplasy, or any combination of these factors. No extant diploid donors could be identified in Physolychnis s.l.     

Phylogenetic relationships of North American nymphophiline gastropods based on mitochondrial DNA sequences

Phylogenetic relationships of 36 nymphophiline species representing 10 genera were inferred from mtCOI sequence data and compared to recent morphology-based classifications of this group. Parsimony and maximum likelihood analyses of the molecular data set suggested monophyly of the North American nymphophilines and a sister or otherwise close relationship between this fauna and a European species assigned to the subfamily. Results also supported a previously hypothesized close relationship between the predominantly freshwater nymphophilines and the brackish-water genus Hydrobia . Our analyses resolved a North American nymphophiline subclade composed of Floridobia , Nymphophilus , and Pyrgulopsis , and depicted the remaining North American genera ( Cincinnatia , Marstonia , Notogillia , Rhapinema , Spilochlamys , Stiobia ) as either a monophyletic or paraphyletic group. Two of the large North American genera ( Floridobia , Marstonia ) were supported as monophyletic groups while monophyly of Pyrgulopsis , a western North American group containing > 100 species, was equivocal. North American nymphophiline phylogeny implies that vicariance of eastern and western North American groups was followed by a secondary invasion of eastern coastal areas from the west. We attribute this to dispersal of salt-tolerant progenitors along the Gulf of Mexico coast     

Cones, Seeds, and Foliage of Tetraclinis Salicornioides (Cupressaceae) from the Oligocene and Miocene of Western North America: A Geographic Extension of the European Tertiary Species

The cupressaceous genus Tetraclinis is recognized from the Oligocene and Miocene of western North America on the basis of co-occurring seed cones, seeds, and foliage branches. Morphological and anatomical comparisons with the two previously recognized European Tertiary species indicate that the North American specimens are morphologically inseparable from Tetraclinis salicornioides (Unger) Kvacek. The North American taxon is treated as a new variety, T. salicornioides (Unger) Kvacek var. praedecurrens (Knowlton) comb. et stat. nov., and is distinguished from the European representatives, T. salicornioides (Unger) Kvacek var. salicornioides, by slight anatomical differences in the leaf epidermis. Although cones and seeds of the fossil species are closely similar to those of extant Tetraclinis articulata, the foliage is more "spreading," composed of flattened segments with fused facial and lateral leaves that are apparently adaptive for a more mesic climate. The recognition of T. salicornioides in western North America along with the absence of Tetraclinis in the fossil and recent flora of eastern Asia provide evidence for communication of the species across the North Atlantic during the early or middle Tertiary.     

Mitochondrial DNA phylogeny of North American field crickets: perspectives on the evolution of life cycles,songs, and habitat associations

North American field crickets (genus Gryllus) exhibit a diversity of life cycles, habitat associations, and calling songs. However, patterns of evolution for these ecological and behavioral traits remain uncertain in the absence of a robust phylogenetic framework. Analyses of morphological variation have provided few clues about species relationships in the genus Gryllus. Here we use comparisons of mitochondrial DNA restriction site maps for 29 individuals representing 11 species (including potential outgroups) to examine relationships among eastern North American field crickets. Initially chosen as likely outgroup taxa, the two European species of Gryllus do not obviously fall outside of an exclusively North American clade and (based on amount of sequence divergence) appear to have diverged from North American lineages at about the same time that major North American lineages diverged from each other. The egg-overwintering crickets comprise a strongly supported monophyletic group, but relationships among these three closely related species cannot be resolved. The mtDNA data are consistent with a single origin of egg diapause and do not support a model of recent life cycle divergence and allochronic speciation for Gryllus pennsylvanicus and G. veletis. The two crickets are not sister species, despite remarkable similarity in morphology, habitat, and calling song. This conclusion is consistent with published data on allozyme variation in North American field crickets. The habitat associations of eastern North American field crickets have been labile, but calling songs sometimes have remained virtually unchanged across multiple speciation events.