Evolutionary Divergence of the Genetic Architecture Underlying Photoperiodism in the Pitcher-Plant Mosquito, Wyeomyia Smithii

We determine the contribution of composite additive, dominance, and epistatic effects to the genetic divergence of photoperiodic response along latitudinal, altitudinal, and longitudinal gradients in the pitcher-plant mosquito, Wyeomyia smithii. Joint scaling tests of crosses between populations showed wide-spread epistasis as well as additive and dominance differences among populations. There were differences due to epistasis between an alpine population in North Carolina and populations in Florida, lowland North Carolina, and Maine. Longitudinal displacement resulted in differences due to epistasis between Florida and Alabama populations separated by 300 km but not between Maine and Wisconsin populations separated by 2000 km. Genetic differences between New Jersey and Ontario did not involve either dominance or epistasis and we estimated the minimum number of effective factors contributing to a difference in mean critical photoperiod of 5 SD between them as n(E) = 5. We propose that the genetic similarity of populations within a broad northern region is due to their more recent origin since recession of the Laurentide Ice Sheet and that the unique genetic architecture of each population is the result of both mutation and repeated migration-founder-flush episodes during the dispersal of W. smithii in North America. Our results suggest that differences in composite additive and dominance effects arise early in the genetic divergence of populations while differences due to epistasis accumulate after more prolonged isolation.     

Reproductive compatibility among latitudinally separated Scottolana canadensis (Willey) (Harpacticoida)

Scottolana canadensis is distributed widely along the east coast of North America. Although males exhibited mating behavior with females copepodites, copulation occurred following the female terminal molt. Crossing experiments revealed that in some cases, male mating behavior decreased with increasing latitudinal distance of male and female source locales. However, latitudinally-related differences in copepod body size most likely did not contribute to variation in male mating behavior. Survival patterns of fertilized eggs and fertility of offspring revealed postzygotic reproductive isolation of Florida populations from all others collected north to Maine.     

Global phylogeography of a cryptic copepod species complex and reproductive isolation between genetically proximate "populations"

The copepod Eurytemora affinis has a broad geographic range within the Northern Hemisphere, inhabiting coastal regions of North America, Asia, and Europe. A phylogenetic approach was used to determine levels of genetic differentiation among populations of this species, and interpopulation crosses were performed to determine reproductive compatibility. DNA sequences from two mitochondrial genes, large subunit (16S) rRNA (450 bp) and cytochrome oxidase I (COI, 652 bp), were obtained from 38 populations spanning most of the species range and from two congeneric species, E. americana and E. herdmani. Phylogenetic analysis revealed a polytomy of highly divergent clades with maximum sequence divergences of 10% in 16S rRNA and 19% in COI. A power test (difference of a proportion) revealed that amount of sequence data collected was sufficient for resolving speciation events occurring at intervals greater than 300,000 years, but insufficient for determining whether speciation events were approximately simultaneous. Geographic and genetic distances were not correlated (Mantel's test; r = 0.023, P = 0.25), suggesting that populations had not differentiated through gradual isolation by distance. At finer spatial scales, there was almost no sharing of mtDNA haplotypes among proximate populations, indicating little genetic exchange even between nearby sites. Interpopulation crosses demonstrated reproductive incompatibility among genetically distinct populations, including those that were sympatric. Most notably, two geographically distant (4000 km) but genetically proximate (0.96% 16S, 0.15% COI) populations exhibited asymmetric reproductive isolation at the F2 generation. Large genetic divergences and reproductive isolation indicate that the morphologically conservative E. affinis constitutes a sibling species complex. Reproductive isolation between genetically proximate populations underscores the importance of using multiple measures to examine patterns of speciation.     

Relationships among cave swallow populations (Petrochelidon fulva) determined by comparisons of microsatellite and cytochrome b data

The cave swallow (Petrochelidon fulva) is a polytypic species with isolated populations in northwestern South America, southwestern North America, Yucatan, Greater Antilles, and Florida. We compared microsatellite genotypes of at least five individuals each from five populations and cytochrome b sequence data of two individuals each from seven populations plus two outgroups. Microsatellite allelic diversity was substantial, and the North American populations were about equally variable. In contrast, the Ecuadorian population had far less genetic variation. Gene flow was apparent among populations, especially between Texas and Florida. Genetic structure was greater than in widespread North American species but less than that of sedentary Neotropical birds. Microsatellite genetic distances indicated a close affinity between Ecuadorian and northern populations, especially Texas and Florida, but this finding was inconsistent with cytochrome b data, which indicated that the Ecuadorian population is the clear outgroup to the northern populations. Its outgroup status is consistent with recent classifications that designate South American populations as their own species (P. rufocollaris). The cytochrome b data further suggested that the northern populations are divided into two clades: Texas/Yucatan and Florida/Greater Antilles. The microsatellite data incorrectly measured the diversity and affinities of Ecuadorian birds apparently because of an ascertainment bias that results from the use of heterologous PCR primers. Despite these problems in measuring phylogenetic relationships, the microsatellite data appeared to work well as a population genetic marker in indicating population structure and gene flow.     

Sunshine versus gold: The effect of population age on genetic structure of an invasive mosquito

The genetic diversity and structure of invasive species are affected by the time since invasion, but it is not well understood how. We compare likely the oldest populations of Aedes aegypti in continental North America with some of the newest to illuminate the range of genetic diversity and structure that can be found within the invasive range of this important disease vector. Aedes aegypti populations in Florida have probably persisted since the 1600‐1700s, while populations in southern California derive from new invasions that occurred in the last 10 years. For this comparison, we genotyped 1,193 individuals from 28 sites at 12 highly variable microsatellites and a subset of these individuals at 23,961 single nucleotide polymorphisms (SNPs). This is the largest sample analyzed for genetic structure for either region, and it doubles the number of southern California populations previously analyzed. As predicted, the older populations (Florida) showed fewer indicators of recent founder effect and bottlenecks; in particular, these populations have dramatically higher genetic diversity and lower genetic structure. Geographic distance and driving distance were not good predictors of genetic distance in either region, especially southern California. Additionally, southern California had higher levels of genetic differentiation than any comparably sized documented region throughout the worldwide distribution of the species. Although population age and demographic history are likely driving these differences, differences in climate and transportation practices could also play a role.     

Phylogeography and cryptic introduction of the ragworm Hediste diversicolor (Annelida,Nereididae) in the Northwest Atlantic

Many benthic marine invertebrates show striking range disjunctions across broad spatial scales. Without direct evidence for endemism or introduction, these species remain cryptogenic. The common ragworm Hediste diversicolor plays a pivotal role in sedimentary littoral ecosystems of the North Atlantic as an abundant prey item and ecosystem engineer, but exhibits a restricted dispersal capacity that may limit connectivity at both evolutionary and ecological time scales. In Europe, H. diversicolor is subdivided into cryptic taxa and genetic lineages whose distributions have been modified by recent invasions. Its origin in the northwest Atlantic has not been adequately addressed. To trace the age and origin of North American ragworm populations, we analyzed mtDNA sequence data (COI) from the Gulf of Maine and Bay of Fundy (n=73 individuals) and compared our findings with published data from the northeast Atlantic. Our results together with previous data indicate that two species of the H. diversicolor complex have independently colonized the northwest Atlantic at least three different times, resulting in two distinct conspecific assemblages in the Bay of Fundy and Gulf of Maine (respectively) that are different from the species found in the Gulf of St. Lawrence. North American populations had significantly lower genetic diversity compared with populations in the northeast Atlantic, and based on patterns of shared identity, populations in the Bay of Fundy originated from the Baltic Sea and North Sea. Populations from the Gulf of Maine were phylogenetically distinct and most likely originated from unsampled European populations. Analyses of the North American populations revealed patterns of post‐colonization gene flow among populations within the Gulf of Maine and Bay of Fundy. However, we failed to detect shared haplotypes between the two regions, and this pattern of complete isolation corroborates a strong phylogeographic break observed in other species.     

The parasite that causes whirling disease, Myxobolus cerebralis, is genetically variable within and across spatial scales

Understanding the genetic structure of parasite populations on the natural landscape can reveal important aspects of disease ecology and epidemiology and can indicate parasite dispersal across the landscape. Myxobolus cerebralis (Myxozoa: Myxosporea), the causative agent of whirling disease in the definitive host Tubifex tubifex, is native to Eurasia and has spread to more than 25 states in the USA. The small amounts of data available to date suggest that M. cerebralis has little genetic variability. We examined the genetic variability of parasites infecting the definitive host T. tubifex in the Madison River, MT, and also from other parts of North America and Europe. We cloned and sequenced 18S ribosomal DNA and the internal transcribed spacer-1 (ITS-1) gene. Five oligochaetes were examined for 18S and five for ITS-1, only one individual was examined for both genes. We found two different 18S rRNA haplotypes of M. cerebralis from five worms and both intra- and interworm genetic variation for ITS-1, which showed 16 different haplotypes from among 20 clones. Comparison of our sequences with those from other studies revealed M. cerebralis from MT was similar to the parasite collected from Alaska, Oregon, California, and Virginia in the USA and from Munich, Germany, based on 18S, whereas parasite sequences from West Virginia were very different. Combined with the high haplotype diversity of ITS-1 and uniqueness of ITS-1 haplotypes, our results show that M. cerebralis is more variable than previously thought and raises the possibility of multiple introductions of the parasite into North America.     

Populations of the European freshwater pulmonate Physa acuta are not reproductively isolated from American Physa heterostropha or Physa integra

Abstract. It has long been speculated that Physa acuta , a pulmonate snail widespread and invasive in fresh waters of the old world, may have originated in North America. But the identification of a new-world cognate has been complicated by the confused systematics and taxonomy of the Physidae in America. More than 40 species of physids are currently recognized in the United States, many with variable and overlapping morphology. We have previously established that premating reproductive isolation is negligible among physid snails. Here we report the results from no-choice crosses each involving 2 populations of the widespread American species Physa heterostropha and Physa integra , both with each other and with P. acuta , designed to compare measures of reproductive success between species and between populations within species. Samples of P. acuta were collected from France and Ireland, P. heterostropha from eastern Pennsylvania and South Carolina, and P. integra from southern Indiana and northern Michigan. The 6 intrapopulation controls varied quite significantly in their survival, age at first reproduction, parental fecundity, F₁ viability, and F₁ fertility under our culture conditions. Measures of survival and reproduction in the 6 interpopulation crosses were generally intermediate, but in no case significantly worse than the more poorly performing control. Thus we were unable to detect evidence of reproductive isolation among our 6 populations of snails from 2 continents. All should be referred to the oldest available nomen, P. acuta .     

Hierarchical structure of mitochondrial DNA gene flow among humpback whales Megaptera novaeangliae, world-wide

The genetic structure of humpback whale populations and subpopulation divisions is described by restriction fragment length analysis of the mitochondrial (mt) DNA from samples of 230 whales collected by biopsy darting in 11 seasonal habitats representing six subpopulations, or 'stocks', world-wide. The hierarchical structure of mtDNA haplotype diversity among population subdivisions is described using the analysis of molecular variance (AMOVA) procedure, the analysis of gene identity, and the genealogical relationship of haplotypes as constructed by parsimony analysis and distance clustering. These analyses revealed: (i) significant partitioning of world-wide genetic variation among oceanic populations, among subpopulations or 'stocks' within oceanic populations and among seasonal habitats within stocks; (ii) fixed categorical segregation of haplotypes on the south-eastern Alaska and central California feeding grounds of the North Pacific; (iii) support for the division of the North Pacific population into a central stock which feeds in Alaska and winters in Hawaii, and an eastern or 'American' stock which feeds along the coast of California and winters near Mexico; (iv) evidence of genetic heterogeneity within the Gulf of Maine feeding grounds and among the sampled feeding and breeding grounds of the western North Atlantic; and (v) support for the historical division between the Group IV (Western Australia) and Group V (eastern Australia, New Zealand and Tonga) stocks in the Southern Oceans. Overall, our results demonstrate a striking degree of genetic structure both within and between oceanic populations of humpback whales, despite the nearly unlimited migratory potential of this species. We suggest that the humpback whale is a suitable demographic and genetic model for the management of less tractable species of baleen whales and for the general study of gene flow among long-lived, mobile vertebrates in the marine ecosystem.     

European green crabs (Carcinus maenas) in the northeastern Pacific: genetic evidence for high population connectivity and current-mediated expansion from a single introduced source population

Aim The European green crab (Carcinus maenas) expanded dramatically after its introduction to the west coast of North America, spreading over 1000 km in < 10 years. We use samples of Carcinus maenas collected over time and space to investigate the genetic patterns underlying the species’ initial establishment and spread, and discuss our findings in the context of the species’ life history characteristics and demography. Location The central west coast of North America, encompassing California, Oregon, and Washington (USA) and British Columbia (Canada). Methods We collected 1040 total samples from 21 sites representing the major episodes of population establishment and expansion along the west coast of North America. Microsatellite markers were used to assess genetic diversity and structure at different time points in the species’ spread, to investigate connectivity between embayments and to estimate both short‐term effective population sizes and the number of original founders. Assignment testing was performed to determine the likely source of the introduction. Results Carcinus maenas in western North America likely derived from a single introduction of a small number of founders to San Francisco Bay, CA from the east coast of North America. Throughout its western North American range, the species experiences periodic migration between embayments, resulting in a minor loss of genetic diversity in more recently established populations versus the populations in the area of initial establishment. Main conclusions Low genetic diversity has not precluded the ability of C. maenas to successfully establish and spread on the west coast of North America. An efficient oceanographic transport mechanism combined with highly conducive life history traits are likely the major drivers of C. maenas spread. Evidence for a single introduction underscores the potential utility of early detection and eradication of high‐risk invasive species.     

Variation in genetic structure among populations of the caddisfly Helicopsyche borealis from three streams in northern California, U.S.A.

1. Allozyme electrophoresis was used to describe the genetic structure of Helicopsyche borealis caddisflies collected from three sites in each of three streams in northern California, U.S.A.: the Rice Fork of the Eel River; Big Sulphur Creek; and Alameda Creek. Between 7 and 11km separated adjacent sites within these three streams. Helicopsyche borealis from three additional streams in eastern North America (Christiana Creek, Indiana; Byrd's Mill Creek, Oklahoma; Susquehanna River, Pennsylvania) were also analysed electrophoretically to address taxonomic questions that arose during the study. 2. Four genetically distinct groups of individuals were identified (i.e. Helicopsyche types A, B, C, and D). Lack of interbreeding between sympatric groups (as evidenced by fixed allelic differences) and large genetic differences (mean Nei's genetic distances = 0.396–0.693) indicate that these four groups of Helicopsyche were actually reproductively isolated species rather than genetic variants of a single species. 3. Occurrence of Helicopsyche type A at multiple sites permitted an analysis of spatial variation in genetic structure. Within a drainage basin, small differences in allele frequencies were observed among sites in the Rice Fork and Big Sulphur Creek, but not in Alameda Creek. Larger genetic differences were found among sites in separate drainage basins. Genetic distances (Nei's) between Helicopsyche type A from California and from eastern North America sites (mean = 0.236) were greater than interpopulation differences commonly observed for insects, which suggests that Helicopsyche type A from California may represent a different species than Helicopsyche type A from eastern North America. 4. Geographical and taxonomic differences observed in this study underscore the importance of understanding both population structure and genetic relationships among populations in the design and interpretation of stream faunal studies.     

AFLP and breeding system studies indicate vicariance origin for scattered populations and enigmatic low fecundity in the Moroccan endemic Hypochaeris angustifolia (Asteraceae), sister taxon to all of the South American Hypochaeris species

We used Amplified Fragment Length Polymorphism markers (AFLP) and breeding system studies to investigate the population structure and reproductive biology of Hypochaeris angustifolia (Asteraceae: Cichorieae). This species is endemic to altiplanos of the Atlas Mountains (Morocco) where it occurs in scattered populations, and it is the sister species to c. 40 species of this genus in South America. PCoA, NJ, and Bayesian clustering, revealed that the populations are very isolated whilst AFLP parameters show that almost all populations have marked genetic divergence. We contend that these features are more in accord with a vicariance origin for the scattered populations of H. angustifolia, rather than establishment by long-distance dispersal. The breeding system studies revealed that H. angustifolia is a self-incompatible species, with low fecundity in natural and in experimental crosses, probably due to a low frequency of compatible phenotypes within and between the populations.     

Effects of Pleistocene climatic fluctuations on the phylogeographic and demographic histories of Pacific herring (Clupea pallasii)

We gathered mitochondrial DNA sequences (557 bp from the control region in 935 specimens and 668 bp of the cytochrome b gene in 139 specimens) of Pacific herring collected from 20 nearshore localities spanning the species' extensive range along the North Pacific coastlines of Asia and North America. Haplotype diversity and nucleotide diversity were high, and three major phylogeographic lineages (sequence divergences ca. 1.5%) were detected. Using a variety of phylogenetic methods, coalescent reasoning, and molecular dating interpreted in conjunction with paleoclimatic and physiographic evidence, we infer that the genetic make-up of extant populations of C. pallasii was shaped by Pleistocene environmental impacts on the historical demography of this species. A deep genealogical split that cleanly distinguishes populations in the western vs. eastern North Pacific probably originated as a vicariant separation associated with a glacial cycle that drove the species southward and isolated two ancestral populations in Asia and North America. Another deep genealogical split may have involved either a vicariant isolation of a third herring lineage (perhaps originally in the Gulf of California) or it may have resulted simply from the long coalescent times that are possible in large populations. Coalescent analyses showed that all the three evolutionary lineages of C. pallasii experienced major expansions in their most recent histories after having remained more stable in the preceding periods. Independent of the molecular calibration chosen, populations of C. pallasii appear to have remained stable or grown throughout the periods that covered at least two major glaciations, and probably more.     

Geological barriers and restricted gene flow in the holarctic skipper Hesperia comma (Hesperiidae)

Patterns of genetic variation within a species may be a consequence of historical factors, such as past fragmentation, as well as current barriers to gene flow. Using sequence data from the mitochondrial cytochrome oxidase subunit II region (COII) and the nuclear gene wingless, we conducted a phylogeographical study of the holarctic skipper Hesperia comma to elucidate patterns of genetic diversity and to infer historical and contemporary processes maintaining genetic variation. One hundred and fifty-one individuals were sampled from throughout North America and Eurasia, focusing on California and adjacent regions in the western United States where morphological diversity is highest compared to the rest of the range. Analyses of sequence data obtained from both genes revealed a well-supported division between the Old and New World. Within western North America, wingless shows little geographical structure, while a hierarchical analysis of genetic diversity of COII sequences indicates three major clades: a western clade in Oregon and Northern California, an eastern clade including the Great Basin, Rocky Mountains and British Columbia, and a third clade in southern California. The Sierra Nevada and the Transverse Ranges appear to be the major barriers to gene flow for H. comma in the western United States. Relatively reduced haplotype diversity in Eurasia compared to North America suggests that populations on the two continents have been affected by different historical processes.     

GEOGRAPHIC VARIATION IN ALLOZYMES IN A “RING SPECIES,” THE PLETHODONTID SALAMANDER ENSATINA ESCHSCHOLTZII OF WESTERN NORTH AMERICA

The ring species Ensatina eschscholtzii (a plethodontid salamander) of western North America has a circle of subspecies surrounding the Central Valley of California which come into contact and are sympatric in southern California. We examined 26 proteins in 19 populations (maximum of 10 specimens per population) collected throughout the range in order to gain an understanding of the degree of differentiation in the group. Allozymic differentiation is profound, with genetic distances in excess of 0.5 (Rogers or Nei) between populations. Naturally hybridizing populations differ by genetic distances greater than 0.4. Two general classes of color morphs, blotched and unblotched, are segregated geographically, but they do not form discrete genetic units. Both are deeply differentiated, and genetic distances among populations of either class exceed those measured between the classes where they are sympatric in southern California. This study disclosed little evidence of gene exchange around the ring of populations and sampling of many additional populations in regions between populations sampled thus far will be required to determine whether smooth intergradation occurs. Although genetic distances measured exceed those between some co-occurring species of plethodontid salamanders, we find no evidence of borders between cryptic species.     

Genetic impoverishment and cross-incompatibility in remnant genotypes of Ziziphus celata (Rhamnaceae), a rare shrub endemic to the Lake Wales Ridge, Florida

The loss of genetic diversity in fragmented populations ofself-incompatible plant species may result in sexual reproductive failure andlocal extinctions. Florida ziziphus (Ziziphus celata) is aself-incompatible clonal shrub known only from five genetically depauperatepopulations on the Lake Wales Ridge, Florida, USA. Recovery of this speciesrequires identification of cross-compatible genotypes that can be used to createviable (i.e., sexually reproducing) populations. To further development of arecovery program for this highly imperiled species, we investigated its geneticstructure and sexual reproductive viability. We used random amplifiedpolymorphic DNAs (RAPDs) to investigate genetic variability within remnantpopulations and we conducted experimental compatibility trials to determine thecross-compatibility of remnant genotypes. One hundred and ninety-nine uniquestem samples collected from one ex situ and fivein situ populations were assayed for the presence orabsence of a band for 32 RAPD markers. Based on unweighted pair-group meancluster analysis (UPGMA), only 11 multi-locus genotypes (MLGs) were identified.Eight of these MLGs correspond to MLGs identified in an earlier allozyme study.In addition, we identified three new RAPD-based MLGs. Three of the five naturalpopulations consisted of only one MLG, while the largest and most geneticallydiverse population comprised only four MLGs. Coefficients of similarity rangedfrom 96.6% for the most closely related MLGs to 20.7% for the most distantlyrelated. The compatibility trials demonstrated that most MLGs arecross-incompatible. With 69% of all possible one-way crosses tested (38/55), wehave identified only eight compatible crosses via germination trials. Based onthe results of the compatibility trials, we assigned MLGs toself-incompatibility (SI) mating types. On present evidence, the currentbreeding population of Florida ziziphus may comprise as few as two SI matingtypes. These SI mating types will be used to guide future breeding efforts andan experimental introduction.     

Global Population Genetic Structure of Caenorhabditis remanei Reveals Incipient Speciation

Mating system transitions dramatically alter the evolutionary trajectories of genomes that can be revealed by contrasts of species with disparate modes of reproduction. For such transitions in Caenorhabditis nematodes, some major causes of genome variation in selfing species have been discerned. And yet, we have only limited understanding of species-wide population genetic processes for their outcrossing relatives, which represent the reproductive state of the progenitors of selfing species. Multilocus-multipopulation sequence polymorphism data provide a powerful means to uncover the historical demography and evolutionary processes that shape genomes. Here we survey nucleotide polymorphism across the X chromosome for three populations of the outcrossing nematode Caenorhabditis remanei and demonstrate its divergence from a fourth population describing a closely related new species from China, C. sp. 23. We find high genetic variation globally and within each local population sample. Despite geographic barriers and moderate genetic differentiation between Europe and North America, considerable gene flow connects C. remanei populations. We discovered C. sp. 23 while investigating C. remanei, observing strong genetic differentiation characteristic of reproductive isolation that was confirmed by substantial F(2) hybrid breakdown in interspecific crosses. That C. sp. 23 represents a distinct biological species provides a cautionary example of how standard practice can fail for mating tests of species identity in this group. This species pair permits full application of divergence population genetic methods to obligately outcrossing species of Caenorhabditis and also presents a new focus for interrogation of the genetics and evolution of speciation with the Caenorhabditis model system.     

Weedy adaptation in Setaria spp. II. Genetic diversity and population genetic structure in S. glauca,S. geniculata,and S. faberii (Poaceae)

Setaria glauca (yellow foxtail), S. geniculata (knotroot foxtail), and S. faberii (giant foxtail) are important cosmopolitan weeds of temperate and tropical regions. Isozyme markers were used to investigate genetic diversity and population genetic structure in 94 accessions of yellow foxtail, 24 accessions of knotroot foxtail, and 51 accessions of giant foxtail, collected mainly from North America and Eurasia. Giant foxtail populations were nearly identical genetically, with only one population exhibiting isozyme polymorphism. Yellow and knotroot foxtail populations had low genetic diversity but marked population differentiation. Although the latter species are similar morphologically, they are readily distinguished electrophoretically, with Nei's genetic identity being 0.83. In both species, genetic divergence between accessions from Eurasia and North America was minimal. Populations from the native ranges had slightly greater genetic diversity than those from the respective introduced ranges. Yellow foxtail populations genetically clustered into Asian, European, and North American groups. Within North America, yellow foxtail populations from Iowa were genetically diverse whereas populations collected from other North American locations were nearly monomorphic for the same multilocus genotype. Knotroot foxtail populations in North America were genetically differentiated into northern and southern groups on either side of a line at ≈37° N latitude. No genetic patterning was evident in knotroot foxtail populations from Eurasia. In both yellow and knotroot foxtail, patterns of population genetic structure have been influenced by several factors, including genetic bottlenecks associated with founder events, genetic drift, and natural selection.     

The ectomycorrhizal fungus Amanita phalloides was introduced and is expanding its range on the west coast of North America

The deadly poisonous Amanita phalloides is common along the west coast of North America. Death cap mushrooms are especially abundant in habitats around the San Francisco Bay, California, but the species grows as far south as Los Angeles County and north to Vancouver Island, Canada. At different times, various authors have considered the species as either native or introduced, and the question of whether A. phalloides is an invasive species remains unanswered. We developed four novel loci and used these in combination with the EF1α and IGS loci to explore the phylogeography of the species. The data provide strong evidence for a European origin of North American populations. Genetic diversity is generally greater in European vs. North American populations, suggestive of a genetic bottleneck; polymorphic sites of at least two loci are only polymorphic within Europe although the number of individuals sampled from Europe was half the number sampled from North America. Endemic alleles are not a feature of North American populations, although alleles unique to different parts of Europe were common and were discovered in Scandinavian, mainland French, and Corsican individuals. Many of these endemic European haplotypes were found together at single sites in California. Early collections of A. phalloides dated prior to 1963 and annotated using sequences of the ITS locus proved to be different species of Amanita. The first Californian collections that we confirmed as A. phalloides were made from the Del Monte Hotel (now the Naval Postgraduate School) in Monterey, and on the campus of the University of California, Berkeley, in 1938 and in 1945. These historical data are used in combination with data on A. phalloides’ current distribution to estimate a rate of spread for A. phalloides in California. Many species of ectomycorrhizal (EM) fungi have been introduced across and among continents, but with this evidence, the death cap becomes the only known invasive EM fungus in North America.     

Distribution of an invasive ant, Myrmica rubra (Hymenoptera: Formicidae), in Maine

Introduced populations of the north temperate ant species, Myrmica rubra (L.), have become pestiferous in various locations in the northeastern United States, particularly in coastal communities in Maine. Native populations of this ant are widely distributed throughout northern Europe and western Asia; however, nest densities in its native range do not usually reach the high levels observed for many introduced populations. This aggressive ant readily stings, and because of its high densities, homeowners continually encounter nests at a frequency that interferes with use of their properties. Surveys were conducted in Maine from 2001 through 2004 to determine the statewide extent of current infestations. Nests in established populations in coastal Maine were sampled from April through September to assess seasonal changes in the density and composition of colonies. Similarities and differences between introduced populations of M. rubra in Maine and published reports of this species in Europe are discussed. Museum records of this species in North America were also researched and are presented.