Project description:The increase of biodiversity from poles to equator is one of the most pervasive features of nature. For 2 centuries since von Humboldt, Wallace, and Darwin, biogeographers and ecologists have investigated the environmental and historical factors that determine the latitudinal gradient of species diversity, but the underlying mechanisms remain poorly understood. The recently proposed metabolic theory of ecology (MTE) aims to explain ecological patterns and processes, including geographical patterns of species richness, in terms of the effects of temperature and body size on the metabolism of organisms. Here we use 2 comparable databases of tree distributions in eastern Asia and North America to investigate the roles of environmental temperature and spatial scale in shaping geographical patterns of species diversity. We find that number of species increases exponentially with environmental temperature as predicted by the MTE, and so does the rate of spatial turnover in species composition (slope of the species-area relationship). The magnitude of temperature dependence of species richness increases with spatial scale. Moreover, the relationship between species richness and temperature is much steeper in eastern Asia than in North America: in cold climates at high latitudes there are more tree species in North America, but the reverse is true in warmer climates at lower latitudes. These patterns provide evidence that the kinetics of ecological and evolutionary processes play a major role in the latitudinal pattern of biodiversity.
Project description:Broad-scale, quantitative assessments of insect biodiversity and the factors shaping it remain particularly poorly explored. Here we undertook a spatial phylogenetic analysis of North American butterflies to test whether climate stability and temperature gradients have shaped their diversity and endemism. We also performed the first quantitative comparisons of spatial phylogenetic patterns between butterflies and flowering plants. We expected concordance between the two groups based on shared historical environmental drivers and presumed strong butterfly-host plant specializations. We instead found that biodiversity patterns in butterflies are strikingly different from flowering plants, especially warm deserts. In particular, butterflies show different patterns of phylogenetic clustering compared with flowering plants, suggesting differences in habitat conservation between the two groups. These results suggest that shared biogeographic histories and trophic associations do not necessarily assure similar diversity outcomes. The work has applied value in conservation planning, documenting warm deserts as a North American butterfly biodiversity hotspot.
Project description:The disjunct distribution of plants between eastern Asia (EA) and North America (NA) is one of the most well-known biogeographic patterns. However, the formation and historical process of this pattern have been long debated. Chamaecyparis is a good model to test previous hypotheses about the formation of this disjunct pattern as it contains six species disjunctly distributed in EA, western North America (WNA) and eastern North America (ENA). In this study, we applied ecological niche models to test the formation of the disjunct pattern of Chamaecyparis. The model calibrated with the EA species was able to predict the distribution of eastern NA species well, but not the western NA species. Furthermore, the eastern Asian species were shown to have higher niche overlap with the eastern North American species. The EA species were also shown to share more similar habitats with ENA species than with WNA species in the genus. Chamaecyparis species in WNA experienced a significant niche shift compared with congeneric species. Chamaecyparis had a low number of suitable regions in Europe and the middle and western NA during the Last Glacial Maximum (LGM) period, and became extinct in the former region whereas it retains residual distribution in the latter. The extirpations in western NA and Europe in response to the late Neogene and Quaternary climatic cooling and the more similar habitats between ENA and EA ultimately shaped the current intercontinental disjunct distribution of Chamaecyparis. Both current hypotheses may be also jointly applied to explain more eastern Asian and eastern North American disjunctions observed today.
Project description:The genus Nekemias (Vitaceae) was first recognized by Rafinesque in 1838. It has been treated as a synonym of Ampelopsis Michx. Recent phylogenetic studies suggest that Ampelopsis as traditionally delimited is paraphyletic. To maintain the monophyly of each of the genera of Vitaceae, we herein segregate the Ampelopsissect.Leeaceifoliae lineage from Ampelopsis and recognize these taxa in Nekemias Raf., which has a disjunct distribution in eastern to southeastern Asia and eastern North America. Nomenclatural changes are made for nine species and one variety: Nekemiasarborea (L.) J. Wen & Boggan, Nekemiascantoniensis (Hook. & Arn.) J. Wen & Z.L. Nie, Nekemiascelebica (Suess.) J. Wen & Boggan, Nekemiaschaffanjonii (H. Lév. & Van.) J. Wen & Z.L. Nie, Nekemiasgongshanensis (C.L. Li) J. Wen & Z.L. Nie, Nekemiasgrossedentata (Hand.-Mazz.) J. Wen & Z.L. Nie, Nekemiashypoglauca (Hance) J. Wen & Z.L. Nie, Nekemiasmegalophylla (Diels & Gilg) J. Wen & Z.L. Nie, Nekemiasmegalophyllavar.jiangxiensis (W.T. Wang) J. Wen & Z.L. Nie, and Nekemiasrubifolia (Wall.) J. Wen & Z.L. Nie. A taxonomic key is provided for the genus to facilitate identification.
Project description:Background:This paper describes 11 of 18 new species recognised in the recent book, "Field Guide to the Flower Flies of Northeastern North America". Four species are omitted as they need to be described in the context of a revision (three Cheilosia and a Palpada species) and three other species (one Neoascia and two Xylota) will be described by F. Christian Thompson in a planned publication. Six of the new species have been recognised for decades and were treated by J. Richard Vockeroth in unpublished notes or by Thompson in his unpublished but widely distributed "A conspectus of the flower flies (Diptera: Syrphidae) of the Nearctic Region". Five of the 11 species were discovered during the preparation of the Field Guide. Eight of the 11 have DNA barcodes available that support the morphology. New information:New species treated in this paper include: Anasimyia diffusa Locke, Skevington and Vockeroth (Smooth-legged Swamp Fly), Anasimyia matutina Locke, Skevington and Vockeroth (Small-spotted Swamp Fly), Brachyopa caesariata Moran and Skevington (Plain-winged Sapeater), Brachyopa cummingi Moran and Skevington (Somber Sapeater), Hammerschmidtia sedmani Vockeroth, Moran and Skevington (Pale-bristled Logsitter), Microdon (Microdon) scauros Skevington and Locke (Big-footed Ant Fly), Mixogaster fattigi Locke, Skevington and Greene (Fattig's Ant Fly), Neoascia guttata Skevington and Moran (Spotted Fen Fly), Orthonevra feei Moran and Skevington (Fee's Mucksucker), Psilota klymkoi Locke, Young and Skevington (Black Haireye) and Trichopsomyia litoralis Vockeroth and Young (Coastal Psyllid-killer). Common names follow the "Field Guide to the Flower Flies of Northeastern North America" (Skevington et al. 2019).
Project description:Alcoholic liver diseases comprise a spectrum of clinical disorders and changes in liver tissue that can be detected by pathology analysis. These range from steatosis to more severe signs and symptoms of liver disease associated with inflammation, such as those observed in patients with alcoholic hepatitis or cirrhosis. Although the relationship between alcohol consumption and liver disease is well established, severe alcohol-related morbidities develop in only a minority of people who consume alcohol in excess. Inter-individual differences in susceptibility to the toxic effects of alcohol have been studied extensively-they include pattern of alcohol consumption, sex, environmental factors (such as diet), and genetic factors, which vary widely among different parts of the world. Alcoholic liver disease is becoming more common in many parts of Asia, but is decreasing in Western Europe. Treatment approaches, including availability of medications, models of care, and approach to transplantation, differ among regions.
Project description:Clonal emergence is a major driver for changes in bacterial disease epidemiology. Recently, it has been proposed that episodic emergence of novel, hypervirulent clones of group A Streptococcus (GAS) results from horizontal gene transfer (HGT) and recombination events leading to increased expression of the cytotoxins Nga (NADase) and SLO (streptolysin O). We previously described a gene fusion event involving the gene encoding the GAS M protein (emm) and an adjacent M-like protein (enn) in the emm4 GAS population, a GAS emm type that lacks the hyaluronic acid capsule. Using whole genome sequencing of a temporally and geographically diverse set of 1,127 isolates, we discovered that the North American emm4 GAS population has undergone clonal replacement with emergent GAS strains completely replacing historical isolates by 2017. Emergent emm4 GAS strains were defined by a handful of small genetic variations, including the emm-enn gene fusion, and showed a marked in vitro growth defect compared to historical strains. In contrast to other previously described GAS clonal emergence events, emergent emm4 GAS lacked significant HGT events and showed no significant increase in transcript levels of nga/slo toxin gene via RNA sequencing and quantitative real-time PCR analysis relative to historic strains. Despite the in vitro growth differences, emergent emm4 GAS strains demonstrated hypervirulence in mouse and ex vivo growth in human blood compared to historical strains. Thus, these data detail the emergence and dissemination of a hypervirulent acapsular GAS clone defined by small genetic variation thereby defining a novel model for GAS strain replacement.
Project description:Two genetically distinct lineages of European green crabs (Carcinus maenas) were independently introduced to eastern North America, the first in the early 19th century and the second in the late 20th century. These lineages first came into secondary contact in southeastern Nova Scotia, Canada (NS), where they hybridized, producing latitudinal genetic clines. Previous studies have documented a persistent southward shift in the clines of different marker types, consistent with existing dispersal and recruitment pathways. We evaluated current clinal structure by quantifying the distribution of lineages and fine-scale hybridization patterns across the eastern North American range (25 locations, ~39 to 49°N) using informative single nucleotide polymorphisms (SNPs; n = 96). In addition, temporal changes in the genetic clines were evaluated using mitochondrial DNA and microsatellite loci (n = 9-11) over a 15-year period (2000-2015). Clinal structure was consistent with prior work demonstrating the existence of both northern and southern lineages with a hybrid zone occurring between southern New Brunswick (NB) and southern NS. Extensive later generation hybrids were detected in this region and in southeastern Newfoundland. Temporal genetic analysis confirmed the southward progression of clines over time; however, the rate of this progression was slower than predicted by forecasting models, and current clines for all marker types deviated significantly from these predictions. Our results suggest that neutral and selective processes contribute to cline dynamics, and ultimately, highlight how selection, hybridization, and dispersal can collectively influence invasion success.
Project description:We analyzed the geographic distribution of the Ixodes ricinus-like ticks in eastern North America by comparing the mitochondrial 16S rDNA sequences of specimens sampled directly from the field during the 1990s. Two distinct lineages are evident. The southern clade includes ticks from the southeastern and middle-eastern regions of the United States. The range of the northern clade, which appears to have been restricted to the northeastern region until the mid-1900s, now extends throughout the northeastern and middle-eastern regions. These phyletic units correspond to northern and southern taxa that have previously been assigned specific status as Ixodes dammini and Ixodes scapularis, respectively. The expanding range of I. dammini appears to drive the present outbreaks of zoonotic disease in eastern North America that include Lyme disease and human babesiosis.
Project description:BackgroundKirtland's warblers are the rarest songbird species in North America, rarity due in part to a reliance on early successional Jack Pine forests. Habitat loss due to fire suppression led to population declines to fewer than 200 males during the 1970s. Subsequent conservation management has allowed the species to recover to over 1700 males by 2010. In this study, we directly examine the impact that low population sizes have had on genetic variation in Kirtland's warblers. We compare the molecular variation of samples collected in Oscoda County, Michigan across three time periods: 1903-1912, 1929-1955 and 2008-2009.ResultsIn a hierarchical rarified sample of 20 genes and one time period, allelic richness was highest in 1903-1912 sample (A(R) = 5.96), followed by the 1929-1955 sample (A(R) = 5.74), and was lowest in the 2008-2009 sample (A(R) = 5.54). Heterozygosity measures were not different between the 1929-1955 and 2008-2009 samples, but were lower in the 1903-1912 sample. Under some models, a genetic bottleneck signature was present in the 1929-1955 and 2008-2009 samples but not in the 1903-1912 sample.ConclusionsWe suggest that these temporal genetic patterns are the result of the declining Kirtland's warbler population compressing into available habitat and a consequence of existing at low numbers for several decades.