Bur Buttercup, Ranunculus testiculatus, New to Eastern Canada

Bur Buttercup (Ranunculus testiculatus) is newly reported for eastern Canada based on two collections from campgrounds in southern Ontario. This vernal, annual, Eurasian weed is widespread in western North America and is expanding its range in the east; it should be expected elsewhere in eastern Canada. Bur Buttercup is known to be toxic to livestock

A substantial eastern disjunction of Douglas’ Knotweed (Polygonum douglasii Greene, Polygonaceae) in New Brunswick, Canada

We report an isolated population of the native annual Douglas’ Knotweed (Polygonum douglasii Greene) from a dry, south-facing outcrop of conglomerate and sandstone at Big Bluff, near Sussex Corner, New Brunswick, Canada, consisting of about 2500 plants in 2018 and 2022. This occurrence is disjunct by ~450 km from the eastern limit of the known range of Douglas’ Knotweed in southwestern Maine, USA. The nearest known occurrence in Canada is in southern Quebec, ~660 km from Big Bluff. Several lines of evidence indicate that the population in New Brunswick is native. New state records for Wisconsin and Alaska found in online data sources are also verified

Travel Tales of a Worldwide Weed: Genomic Signatures of Plantago major L. Reveal Distinct Genotypic Groups With Links to Colonial Trade Routes

Retracing pathways of historical species introductions is fundamental to understanding the factors involved in the successful colonization and spread, centuries after a species’ establishment in an introduced range. Numerous plants have been introduced to regions outside their native ranges both intentionally and accidentally by European voyagers and early colonists making transoceanic journeys; however, records are scarce to document this. We use genotyping-by-sequencing and genotype-likelihood methods on the selfing, global weed, Plantago major, collected from 50 populations worldwide to investigate how patterns of genomic diversity are distributed among populations of this global weed. Although genomic differentiation among populations is found to be low, we identify six unique genotype groups showing very little sign of admixture and low degree of outcrossing among them. We show that genotype groups are latitudinally restricted, and that more than one successful genotype colonized and spread into the introduced ranges. With the exception of New Zealand, only one genotype group is present in the Southern Hemisphere. Three of the most prevalent genotypes present in the native Eurasian range gave rise to introduced populations in the Americas, Africa, Australia, and New Zealand, which could lend support to the hypothesis that P. major was unknowlingly dispersed by early European colonists. Dispersal of multiple successful genotypes is a likely reason for success. Genomic signatures and phylogeographic methods can provide new perspectives on the drivers behind the historic introductions and the successful colonization of introduced species, contributing to our understanding of the role of genomic variation for successful establishment of introduced taxa.publishedVersio

Travel Tales of a Worldwide Weed: Genomic Signatures of Plantago major L. Reveal Distinct Genotypic Groups With Links to Colonial Trade Routes

Retracing pathways of historical species introductions is fundamental to understanding the factors involved in the successful colonization and spread, centuries after a species’ establishment in an introduced range. Numerous plants have been introduced to regions outside their native ranges both intentionally and accidentally by European voyagers and early colonists making transoceanic journeys; however, records are scarce to document this. We use genotyping-by-sequencing and genotype-likelihood methods on the selfing, global weed, Plantago major, collected from 50 populations worldwide to investigate how patterns of genomic diversity are distributed among populations of this global weed. Although genomic differentiation among populations is found to be low, we identify six unique genotype groups showing very little sign of admixture and low degree of outcrossing among them. We show that genotype groups are latitudinally restricted, and that more than one successful genotype colonized and spread into the introduced ranges. With the exception of New Zealand, only one genotype group is present in the Southern Hemisphere. Three of the most prevalent genotypes present in the native Eurasian range gave rise to introduced populations in the Americas, Africa, Australia, and New Zealand, which could lend support to the hypothesis that P. major was unknowlingly dispersed by early European colonists. Dispersal of multiple successful genotypes is a likely reason for success. Genomic signatures and phylogeographic methods can provide new perspectives on the drivers behind the historic introductions and the successful colonization of introduced species, contributing to our understanding of the role of genomic variation for successful establishment of introduced taxa.info:eu-repo/semantics/publishedVersio

The First Record for Altai Fescue, Festuca altaica (Poaceae), in Nova Scotia, from an Eastern Alpine Site on Cape Breton Island

Altai Fescue, Festuca altaica Trinius, is an amphi-Beringian grass species also known from isolated, but widespread, locations in northeastern North America. The occurrence reported here, at the southern limit of eastern alpine habitat in Canada, represents the first for Nova Scotia

Comparative seed ecology of native and alien plants of open uplands

grantor: University of TorontoPlant invaders may gain an advantage over natives because only enemy-free species are likely to invade (the predator filter hypothesis), or because invaders lose enemies while moving to a new area (the predator escape hypothesis). Working at the Joker's Hill Field Station, near Newmarket, Ontario, I have combined site descriptions, surveys, and experiments to investigate the role of predators and pathogens in seed ecology, and to understand their role in the establishment and spread of exotic species. Results indicate that seeds of both natives and exotics suffered significant losses to above-ground predators and below-ground pathogens. Losses varied among species and habitats; wetlands had particularly high levels of fungal mortality. Aliens and natives did not consistently differ in their susceptibility to predators and pathogens, even when analyzed using methods that controlled for phylogenetic biases. These results suggest natural enemies of seeds do not as a general rule determine invasive ability.M.Sc

Wintercresses (Barbarea W.T. Aiton, Brassicaceae) of the Canadian Maritimes

We conducted a review of herbarium collections of the Wintercress genus (Barbarea W.T. Aiton) from the Maritime provinces. Most specimens previously determined to be the regionally rare native species Erect-fruit Wintercress (Barbarea orthoceras Ledebour) are in fact the uncommon exotic Small-flowered Wintercress (Barbarea stricta Andrzejowski). The latter species is here reported as new to Atlantic Canada, where it is scattered but widespread in the three Maritime provinces. Only three collections (two from New Brunswick and one from Nova Scotia) were confirmed as B. orthoceras. Its known range extent and area of occupancy in the Maritimes has been significantly revised, and B. orthoceras is now considered potentially extirpated in New Brunswick and extremely rare in Nova Scotia. One collection from Nova Scotia was referred to another rare exotic species, Early Wintercress (Barbarea verna (Miller) Ascherson), which represents the first record for the Maritimes

Round-fruited St. John’s-wort (Hypericum sphaerocarpum, Hypericaceae) in Canada

Round-fruited St. John’s-wort (Hypericum sphaerocarpum), a native North American herbaceous, perennial vascular plant, is reported from four sites in southern Ontario, Canada. All four sites are along abandoned railway lines. Although the rich association of native flora suggests native status at one site, H. sphaerocarpum is believed to be introduced elsewhere in its Canadian range in Ontario

Post-dispersal losses to seed predators: an experimental comparison of native and exotic old field plants

This is the accepted manuscript of an article published by NRC Research Press.Invasions by exotic plants may be more likely if exotics have low rates of attack by natural enemies, including post-dispersal seed predators (granivores). We investigated this idea with a field experiment conducted near Newmarket, Ontario, in which we experimentally excluded vertebrate and terrestrial insect seed predators from seeds of 43 native and exotic old-field plants. Protection from vertebrates significantly increased recovery of seeds: vertebrate exclusion produced higher recovery than controls for 30 of the experimental species, increasing overall seed recovery from 38.2% to 45.6%. Losses to vertebrates varied among species, significantly increasing with seed mass. In contrast, insect exclusion did not significantly improve seed recovery. There was no evidence that aliens benefitted from a reduced rate of post-dispersal seed predation. The impacts of seed predators did not differ significantly between natives and exotics, which instead showed very similar responses to predator exclusion treatments. These results indicate that while vertebrate granivores had important impacts, especially on large-seeded species, exotics did not generally benefit from reduced rates of seed predation. Instead, differences between natives and exotics were small compared with interspecific variation within these groups.This research was supported by an NSERC Research Grant to PMK and an NSERC PGS to CSB. Additional support was provided by The University of Toronto, the Connaught Fund, and Human Resources Development Canada

Effects of fungal pathogens on seeds of native and exotic plants: a test using congeneric pairs

This is the accepted manuscript of an article published by Wiley.It has previously been hypothesized that low rates of attack by natural enemies may contribute to the invasiveness of exotic plants. We tested this hypothesis by investigating the influence of pathogens on survival during a critical life-history stage: the seed bank. We used fungicide treatments to estimate the impacts of soil fungi on buried seeds of a taxonomically broad suite of congeneric natives and exotics, in both upland and wetland meadows. Seeds of both natives and exotics were recovered at lower rates in wetlands than in uplands. Fungicide addition reduced this difference by improving recovery in wetlands, indicating that the lower recovery was largely attributable to a higher level of fungal mortality. This suggests that fungal pathogens may contribute to the exclusion of upland species from wetlands. The effects of fungicide on the recovery of buried seeds did not differ between natives and exotics. Seeds of exotics were recovered at a higher rate than seeds of natives in uplands, but this effect was not attributable to fungal pathogens. Fungal seed pathogens may offer poor prospects for the management of most exotic species. The lack of consistent differences in the responses of natives vs. exotics to fungicide suggests few aliens owe their success to low seed pathogen loads, while impacts of seed-pathogenic biocontrol agents on non-target species would be frequent.This research was supported by an NSERC Research Grant to PMK and an NSERC PGS to CSB. Additional support was provided by The University of Toronto, the Connaught Fund, and Human Resources Development Canada