Colonized North America Research Articles

Aedes albopictus (Diptera: Culicidae) eggs: field survivorship during northern Indiana winters.

Aedes albopictus (Skuse) is an Asian mosquito that recently has colonized North America via used tire transport. Temperate Ae. albopictus populations overwinter as diapausing eggs, but tropical populations cannot diapause. Eggs of tropical (SABAH) and temperate (INDY) Ae. albopictus were obtained in diapause-inducing conditions and placed inside a scrap tire to monitor overwintering survival in northern Indiana during the winters of 1989-1990 and 1990-1991. Diapause eggs of Ae. triseriatus (Say), a native North American mosquito, were included for comparison. Tropical Ae. albopictus from Malaysia did not survive either winter. Temperate Ae. albopictus from Indianapolis, IN, did not survive the winter of 1989-1990, but 78% survived the winter of 1990-1991. In contrast, 92 and 96% of Ae. triseriatus survived the winters of 1989-1990 and 1990-1991, respectively. Neither mean temperature nor absolute minimum temperature (a winter's lowest temperature) accurately predicted Ae. albopictus overwintering survivorship in the field. The possible effect of snow and other insulating materials on the overwintering survivorship of Ae. albopictus eggs is discussed.

National Battles: Canadian Monumental Drama and the Investiture of History

English[-speaking] Canada is a nation by default, neither a political entity nor manifest national sentiment; more than a land but less than a country. Few would dispute that Quebec is a nation within a nation, but fewer might assert with confidence that Canada is therefore a nation surrounding a nation. The paradox in that formulation is the paradox of postcolonialism as it is manifest in Canadian experience. The prospect of an independent Quebec (and for that matter, the present reality of an independentiste Quebec) exposes "the rest of Canada" (as what used to be called "English Canada" is now commonly named in awkward but accurate journalistic practice) as a political arrangement wanting historical mission. (Canada: what was left when American republicanism transformed the larger part of colonized North America into ideology; the rest of Canada: what is left when Quebec repudiates the proposal that the rebellion of thirteen British colonies forced the condition of nationhood on the ones that were left.)

Phylogenetic analysis of alphaviruses in the venezuelan equine encephalitis complex and identification of the source of epizootic viruses

We studied the evolution of alphaviruses in the Venezuelan equine encephalitis (VEE) complex using phylogenetic analysis of RNA nucleotide sequences from limited portions of the nsP4, El, and 3′ untranslated genome regions of representative strains. The VEE complex constituted a monophyletic group of viruses (descended from a common ancestor); some serologic VEE varieties such as subtype III formed monophyletic groups while subtype I did not. Subtype II Everglades and variety ID enzootic viruses formed a monophyletic group which also included all epizootic variety IAB and IC VEE isolates. Everglades virus diverged from this ID lineage (colonized North America) ca. 100–150 years ago, followed by divergence of variety IAB and IC epizootic viruses. Variety IAB viruses probably emerged from the variety ID lineage once during the early part of this century, while variety IC viruses evolved at least two times. These results identify the source of epizootic VEE viruses as the variety ID enzootic virus lineage which occurs in northern South America and Panama. Even if variety IAB and IC viruses are extinct, recent, multiple emergences of epizootic viruses from an enzootic lineage suggests that other epizootic VEE viruses may evolve again in the future. The close genetic relationship of subtype II Everglades virus to the variety ID lineage also implies the potential for emergence of equine-virulent VEE viruses in Florida.

Phylogenetic relationships among four members of Stizostedion (Percidae) determined by mitochondrial DNA and allozyme analyses

Phylogenetic relationships among four Stizostedion species were examined using mitochondrial DNA (mtDNA) and allozyme analyses. Twenty‐six allozyme loci were scored, and mtDNA variation was examined using 24 restriction endonucleases, yielding 48–57 restriction sites among the species. Genetic distance analyses show that the two North American species (S. canadense and S. vitreum) cluster in one group, while the two European species (S. hciopercu and S. vogense) form a second group. Nei's genetic distance between these two groups was 0.7 ± 0.2 for allozymes, while the corresponding mtDNA sequence divergence was 14.8 ± 2.0%, suggesting that these two groups diverged approximately 10 million years ago. Thus, these data are consistent with the hypothesis that Stizostedion colonized North America during the Pliocene.

CHLOROPLAST‐DNA PHYLOGENETICS AND BIOGEOGRAPHY IN A RETICULATING GROUP: STUDY IN POA (POACEAE)

Cladistic analysis of Poa chloroplast DNA (cpDNA) restriction sites tested previously hypothesized relationships within the genus. Forty‐six taxa representing 19 sections or groups and three subgenera of Poa and two out‐group genera, Puccinellia and Bellardiochloa, are analyzed. Five major and several minor cpDNA groups are identified. The cpDNA cladogram is generally congruent with the subgeneric taxonomy of Poa. Exceptions are reclassified or are discussed in terms of character incompatibilities and possible reticulation events. The cpDNA tree detected relationships among sections that were unresolved using traditional character sets and provides a basis for polarization of morphological character states. An assessment of biogeographic events based on the cpDNA tree suggests: 1) Poa originated in Eurasia; 2) at least six groups of species independently colonized North America; and 3) two of the latter groups colonized South America, and one closely related group colonized New Zealand and Australia. The cpDNA tree provided a conservative estimate of the number of amphi‐neotropical disjunctions when compared to the known number of species disjunctions.

Allozyme and Mitochondrial DNA Variation among Three Species of Stizostedion (Percidae): Phylogenetic and Zoogeographical Implications

The percid genus Stizostedion consists of five species, three in Europe and two in North America, and is believed to have evolved in Europe and then later colonized North America. Three hypotheses exist concerning the route and timing of this colonization: a Miocene Atlantic "riverine" route; a Pliocene Beringian route; and a late-Pleistocene Atlantic route. To test these hypotheses, allozyme and mitochondrial DNA variation were compared in three Stizostedion species, S. canadense and S. vitreum from North America, and S. lucioperca from Europe, to determine their genetic relatedness. Divergence times between S. canadense and S. vitreum were estimated as 3.12 ± 1.33 million years before present (MYBP) from allozyme data and 4.06 ± 0.73 MYBP for mtDNA data, while divergence times between the North American species and S. lucioperca were 10.59 ± 2.74 MYBP and 7.86 ± 1.18 MYBP, respectively. These results are concordant with the hypothesis that colonization of North America by Stizostedion occurred during the Pliocene via Beringia.

Dynamic Relations between the Antler Moth and Meadow Vegetation in Northern Sweden

The antler moth (Cerapteryx graminis L.) is a noctuid that occurs over wide areas of Europe and that has recently colonized North America. The larvae feed almost exclusively on grasses in spring and early summer. In northern latitudes and at high altitudes they can reach densities of 100—1500 individuals/m2. During the outbreak years this herbivore may have a great impact upon the vegetation. In a long—term investigation (11 yr) we recorded the larval densities, plant standing crop, and number of shoots of the abundant grass and herb species in northern Sweden. We also experimentally increased the density of larvae to study the effect of larvae on the individual size, mass, and nutrient concentration of grasses and herbs. During the study period the larval density was negatively correlated with the mean June temperature. We observed two outbreaks of Cerapteryx, which reduced grass biomass and led to increased population sizes of some herb species during the same and/or subsequent years. The annual herb Rhinanthus minor increased in abundance in the years of the Cerapteryx peaks. Increased numbers of flowering shoots were recorded in the following year for the perennial herbs Gnaphalium sylvaticum, Leontodon autumnalis, Trifolium repens, and Veronica serpyllifolia. The abundance of herbs decreased in the following 3—4 yr when the larval densities of Cerapteryx declined, while the grasses increased. There was a negative correlation between the biomass of grasses and the biomass of herbs harvested in early September for the 11 yr. suggesting that herbs also responded to grass consumption by larvae. The nitrogen concentrations in the aboveground parts of grasses and herbs were highest in the same year or in the year following the outbreak. The experiment with increased larval density (°560 larvae/m2) showed that at this level: (1) grass ramets of four species in late summer were lower in height and biomass while the individuals of four out of five species of herbs had greater dry mass, but not height; (2) the concentrations of nitrogen, phosphorus, and potassium in the aboveground parts of the plants were higher than found at the control level (°60 larvae/m2). Our data thus indicate that the grass—herb dynamics are influenced by Cerapteryx. Other important factors affecting the grass—herb dynamics are voles, summer air temperature, and precipitation.

A People and a Nation: A History of the United States

A People and a Nation: A History of the United States

Self-Fertilization and Genetic Population Structure in a Colonizing Land Snail

The pulmonate land snail Rumina decollata in its native Mediterranean range is a complex of monogenic or weakly polygenic strains generated by a breeding system of facultative self-fertilization. One strain colonized North America and now occupies much of the southern United States and northern Mexico. No genetic variation within or among populations in the United States was detected in an electrophoretic analysis of proteins encoded by 25 loci. These findings emphasize the potential for adaptive convergence in the genetic systems of hermaphroditic animals and plants.