We conducted a historical (40 y) floristic assessment of a small (4 km²) park in eastern Canada (Bonaventure Island National Park, Quebec) to evaluate whether small protected areas located in rural landscapes suffer declines in vascular plant populations. We hypothesized that the limited park access (an island accessible only by boat) has a greater influence than the size of the park per se on the preservation of the integrity of the flora. The island flora just before the creation of the protected area (1971) was compared to the flora surveyed during 2 consecutive summers (2007–2008). Of the 358 taxa that were identified before 1971, only 21 (6% of the total) were not found in 2007–2008; of these 21, all but 1 were native taxa, and 17 are likely extirpated, which represents a “natural” extirpation rate of about 1 taxon every 2 or 3 y. Twenty-four taxa found in 2007–2008 were apparently not present before 1971, 14 native taxa and 10 exotic taxa. This represents an introduction rate of 1 native and 1 exotic species every 2 or 3 y. The creation of the protected area did not totally prevent the extinction of native plants or the introduction of exotic species, but the island lost very few species during recent decades, at least compared to small urban parks where historical floristic assessments have been conducted. These urban parks were visited much more frequently than the island, which probably accounts for most of the differences. Strict regulations for visiting the island are apparently an excellent tool for preventing plant introduction (or extirpation), although they are by no means a barrier against the most invasive species.

Stable isotopes are an important tool for studying invertebrate food webs and movement of invertebrates in farmland. However, stable isotope values of farmland invertebrates have been reported for only a few crop types, and rarely for other land uses within farmland. We compared δO¹³C and δ¹⁵N of invertebrates captured in corn, soybean, hay, and hedgerows in eastern Ontario, Canada. δ¹³C was significantly lower in invertebrates captured in hay and hedgerows than in invertebrates captured in soybean and corn, but was not different between invertebrates captured in corn and soybean. This suggests invertebrates may be moving between crop fields during the growing season, using alternative food sources within crop fields, or retaining δ¹³C values from the previous year. When all invertebrates were examined together, δ¹⁵N was significantly higher in invertebrates captured in manured corn than in those captured in soybeans, hedgerows, or manured or unmanured hay, but there was no difference between invertebrates captured in manured or unmanured corn. However, spiders from manured corn had significantly higher δ¹⁵N than those from unmanured corn. Spiders had less variable δ¹⁵N than other taxa in this study, because they occupy a single trophic level. This may make spiders more suitable for detecting changes in fertilization regimes. By demonstrating how invertebrate δ¹³C and δ¹⁵N vary with land use, this study will contribute to the understanding of agricultural food webs and of responses of invertebrates to land use change.

Invasive species are often managed with the objective of population control or eradication. Here we tested whether clipping techniques influenced the aboveground and belowground structures of 2 closely related invasive taxa: Fallopia japonica and Fallopia × bohemica. We compared the aboveground response (plant height, number of stems, and number of leaves) of rhizome fragments to clipping of both taxa. The second experiment was aimed at comparing the belowground response of both taxa to the same clipping disturbance. Rhizome fragments were planted in rhizoboxes and subjected to a clipping disturbance after 4 weeks of growth. Regrowth, belowground biomass, specific root length, total root length, and distribution of roots in 3 soil layers were measured. Aboveground plant traits of both taxa were unaffected by clipping. On the other hand, clipping induced a reduction in belowground dry mass and an increased proportion of roots in the upper layer of soil in F. japonica. Both taxa of Asian knotweeds are highly tolerant to clipping because they are able to cope with aerial biomass loss. Nevertheless, this tolerance seems to be lower in F. japonica. The potential implications for the impact of these invasive species are discussed.

Air pollution has been found to have direct and indirect effects on forest passerines, but there is very little information on the effects of emissions from the pulp and paper industry. This long-term (7 y) study compares breeding parameters of Great tits in industrial and rural sites in maritime pine forests on the west coast of Portugal. We found that Great tits bred earlier, laid more eggs, and produced more fledglings in the industrial area, where we also found a higher biomass of caterpillars, an important food source for tits. There were also differences in ground arthropod numbers, the industrial area having more beetles and millipedes and the rural area more spiders and silverfish. Our results suggest that there are no direct toxic effects of emissions from the paper industry on the study species. However, invertebrate food availability is clearly related to pollution levels, which indirectly affect the breeding performance of the Great tit.

Phenotypic change in closely related lineages frequently follows a common pathway in response to similar environmental conditions. This process, termed parallel evolution, results in the evolution of similar but independently derived ecotypes. Individuals with a blue phenotype are observed in some populations of walleye (Sander vitreus) from Laurentian Shield lakes. The blue phenotype may represent a case of parallel evolution: previous morphological studies revealed significant differences compared with the yellow phenotype as well as numerous lake-specific characteristics among blue individuals. The genetic variability of blue and yellow walleye phenotypes from 6 Laurentian Shield lakes was estimated using AFLP. Results clearly indicate that, whatever their phenotype, individuals from a given lake were more similar genetically than those from other lakes. However, blue and yellow phenotypes represent different populations within each lake. These results suggest the colonization of each lake by a single group of walleye followed by the parallel origin of the blue phenotype. The parallel evolution of the blue walleye phenotype could represent an excellent model for studying mechanisms underlying divergent selection and reproductive isolation.

Climate can shape the nature of plant—animal interactions. The yellow pine chipmunk (Tamias amoenus), which occupies semi-arid pine forests of western North America, engages in mutualistic relationships with its food plants by dispersing seeds. These chipmunks scatter hoard seeds during spring, summer, and early autumn in soil; unrecovered seeds germinate in the spring. The eastern chipmunk (Tamias striatus) of eastern North America occupies mesic deciduous forests. These chipmunks primarily larder hoard seeds and nuts. Seeds in burrow larders cannot establish seedlings, so these chipmunks have not been documented to be involved in mutualistic plant—animal interactions. The differences in behaviour and the roles that these 2 species play in their communities appear to be caused by differences in precipitation. Scattered caches are more secure from pilferers in the dry western environment because olfaction is moisture dependent. In the more mesic eastern forests, scattered caches are quickly pilfered, causing chipmunks to store most food in larders, which they defend. Climate (i.e., amount of precipitation) also influences many other aspects of the ecology of these species, including home range size, the size and role of the home burrow, mode of foraging, and diet.

We determined the proportion of butterfly species that occur as metapopulations with grasslands as the only habitat. We counted all butterflies in 19 semi-natural grassland patches in a forest-dominated landscape in southern Sweden over a 5-y period. Seven of the 44 butterfly species observed exhibited a metapopulation structure. The other species either use grassland mainly for adult feeding but not for breeding (8 species), breed both in grassland and in surrounding habitat types (19 species), or are grassland specialists but their colonization-extinction dynamics are probably not significant, since they were present in nearly all (> 80%) patches (10 species). Occupancy was generally higher in larger patches, and tended to increase with patch connectivity. Among grassland specialists and habitat generalists, the connectivity measure tended to explain more of the variation in occupancy if the shortest dispersal paths avoiding routes over water were considered rather than a measure based on the Euclidian distance between patches. This indicates that lakes, even when they are just a few hundred metres wide, can act as barriers to dispersal for butterflies. We conclude that for many butterflies that occur in semi-natural grasslands in forest-dominated landscapes, intervening habitats are important as breeding sites or as dispersal barriers.

In a heterogeneous landscape, birds must evaluate environmental cues that signal the fitness benefits to be gained from a breeding site. Little study has been devoted to the factors that influence settlement decisions and their implications for breeding in northern populations of American kestrels. We examined nest-site selection and reproductive investment and success of this species in relation to the abundance of small mammals from 1990 to 1997 and territory and nest-site attributes in 2008. Nest-site selection was not associated with prey abundance; however, females initiated laying earlier on territories with higher prey abundance. Kestrels were more likely to choose nest boxes with unobstructed entrances and in recently harvested forests and laid clutches of lower volume in forests with a heavier deciduous component. Nestling mass (females) was greater in boxes at the forest edge and on jack pine, and feather lengths (males) were greater in nests on trees in poor health. We discuss the importance of these features for provisioning and nest vigilance and propose that kestrels in our area make decisions based on interactions occurring at scales intermediate to the landscape and territory levels.

Woody encroachment of grasslands is a common phenomenon worldwide, but the consequences of this encroachment for ecosystem carbon storage, particularly belowground are not clear. We quantified total ecosystem carbon in the 3 major natural upland vegetation communities (grassland, shrubland, and forest) at the northern edge of the North American Great Plains. Total ecosystem carbon storage was significantly greater in forest (125.3 mg C·ha^-1) than in shrubland (92.4 mg C·ha^-1) or grassland (80.7 mg C·ha^-1), and this difference was due mainly to greater aboveground biomass, coarse root biomass, and the presence of a humus layer in the forest. Fine and total root biomass were also greater in forest than shrubland or grassland. In contrast, soil carbon was significantly greater in shrubland (80.6 mg C·ha^-1) and grassland (75.4 mg C·ha^-1) than in forest (48.6 mg C·ha^-1). We also investigated whether aboveground variables could be used to predict belowground carbon pools. Soil carbon increased significantly with aboveground herbaceous biomass, while fine root biomass increased with foliar biomass, but the strongest relationship was between total root biomass and total aboveground biomass (r² = 0.785). These are simple and effective predictors of belowground carbon pools. The rapid shift in carbon storage with forest encroachment, from being dominated by soil carbon in grassland to woody vegetation in forest, represents a significant change in ecosystem structure with implications for the carbon budget.

Garlic mustard (Alliaria petiolata) is an invasive Eurasian species that is now widespread in North America. Like some other invasive species, garlic mustard is known to exude biochemical compounds that can reduce the fitness of native species when it invades a new habitat. Compounds leached from garlic mustard can reduce growth and survival of mycorrhizal fungi associated with forest trees in eastern North America. We tested whether these compounds could also inhibit the growth or survival of fungi known to infect arthropods, the so-called entomopathogenic (EM) fungi. We found that growth of Beauveria bassiana (Bb), a widespread EM fungus, was significantly reduced when spores were incubated on agar plates made with leachate from garlic mustard. When leachate was added to soil that had been inoculated with Bb spores, waxworms were significantly less infected with Bb than they were on soil inoculated with Bb spores alone. Finally, waxworms were less infected with EM spores when they were held in soil collected from field plots with abundant garlic mustard plants compared to neighbouring soils without garlic mustard plants. Together, these results demonstrate the potential for garlic mustard leachate to significantly inhibit the growth of EM fungi and thereby suppress the effects of EM fungi on arthropods. This effect of garlic mustard could be beneficial to humans if it reduces mortality of arthropods that provide ecosystem services, but it could also be harmful to humans if it reduces mortality of pest insects or arthropod vectors of disease, such as ixodid ticks.