An animal's relative body mass (i.e., mass adjusted for length or some other size dimension) is a potential indicator of its body condition, which in turn can influence demographic traits. In this study, I revisited data collected in 1969–1970 on garter snakes, Thamnophis sirtalis parietalis, at a communal hibernaculum in Manitoba, to test hypotheses generated by more recent literature. First, I compared fall-through-spring variation in relative mass to a similar study of another species of Thamnophis in a milder, Mediterranean climate and found a similar temporal pattern, suggesting common features across a wide latitudinal range. Female snakes had a higher relative mass than males and experienced lower decline in relative mass overwinter and through the spring. This suggests different hibernation strategies of the 2 sexes, possibly involving different temperatures or differences in metabolism, and also reflects the preoccupation of males upon spring emergence with searching for mates, at energetic cost while not feeding. Comparison of my data with a second study of the same species at another den in Manitoba indicated nearly identical patterns of loss of mass, based on recaptures of males throughout the spring, and also corroborated that study's finding that initially relatively heavy males remained at the den longer. Thus, males that have accumulated more capital the previous year presumably have more opportunities to mate. Although recapture intervals of most males were only a few days long, similar to the previous study, some males remained in the vicinity of the den for up to 5 weeks. These findings underscore the fundamental differences between males and females in the temporal distribution of their costs of reproduction.

In Quebec, Canada, 5 out of the 8 species of bats are considered potentially threatened or vulnerable. Measuring the impact on bat species of environmental changes brought about by urban development is crucial for bat species conservation. At which spatial scale does a gradient of increasing urbanization have the most significant effect on the distribution and activity of bats? To address this question, 3 sampling points in each of 24 green spaces (of different sizes, degree of “naturalness”, and presence or not of water) across Montréal Island were sampled over 3 separate nights in June and July 2006. Echolocation calls of bats were recorded with Anabat detectors. Bat activity was determined by species or group of species for each green space. Various habitat factors associated with the urban gradient were acquired using GIS along a range of spatial scales, from local to landscape scales (areas of 0.1 km to 2 km radius around sampling points). Results show that patterns of distribution and bat activity differ according to species. Bats of the Myotis genus and Perimyotis subflavus were found mostly in areas with a high percentage of forest cover and near running water. Eptesicus fuscus and Lasiurus cinereus appeared to be less selective, as they were distributed much more uniformly across the study area. The more local spatial scales (from 0.1 km to 0.5 km radius) seem to have had a predominant influence on habitat requirements of bats, particularly for forest-dwelling species.

Changes in climate that affect breeding phenology can have important ramifications for the population dynamics of migratory wildlife. In birds, predicted changes in global climate raise concerns over the ability of migratory species, especially long-distance migrants, to adapt to changes in spring weather conditions. At a riparian breeding site in southern Manitoba, we found that over 3 decades (1974 to 2003), migratory yellow warblers (Dendroica petechia) exhibited considerable plasticity in their timing of clutch initiation in response to mean May temperatures at the breeding site. Spring arrival dates estimated during the last 9 y of our study were also highly variable and correlated with mean May temperatures. By contrast, we found no support for an effect of the El Niño/Southern Oscillation, a climatic phenomenon known to affect weather conditions on wintering grounds of yellow warblers, on spring arrival dates or timing of breeding. This suggests that El Niño/ Southern Oscillation did not have carry-over effects on spring arrival dates or timing of clutch initiation. The results from our study are consistent with the timing of breeding in Neotropical migrant songbirds being flexible and closely coupled with spring temperatures (mean daily May temperatures) at breeding sites. These findings are important for predicting how sensitive long-distance migrant birds may be to changes in spring conditions caused by climatic warming.

Ovenbird (Seiurus aurocapilla) demography and nest-site selection were examined in mature tolerant hardwood stands and stands at 3 stages of recovery (1–5, 10–15, and 20–25 y) following single-tree selection in the continuously forested landscape of Algonquin Provincial Park, central Ontario. This is one of a few studies to provide evidence of these responses in a continuously forested landscape. No differences in nesting success or finite rates of increase were detected among treatments. Ovenbirds were more selective of nest sites with deep leaf-litter and basal areas with a greater proportion of larger trees in recently harvested stands than in other stages of recovery. By 20–25 y post-harvest, most nest-site and random-plot microhabitat parameters did not differ. During the study, Algonquin Provincial Park was designated as a sink, probably due to heavy mast production in 2006, after which some mast-consuming small mammal populations increased by 9-fold, dramatically increasing rates of nest predation. Single-tree selection did not appear to affect ovenbird per capita productivity among stages of forest recovery, and by 20–25 y post-harvest many structural features of the forest had returned to pre-harvest conditions. Thus, in Algonquin Provincial Park, single-tree selection appears to be appropriate for maintaining sufficient ovenbird nest-site features by the end of the first cutting cycle. However, future source-sink modeling of this landscape should consider the influence of resource-pulse dynamics as an important parameter and track changes over the long term, to determine how sustainable populations of ovenbirds are within this region.

Mediterranean xero-halophytic meadows are a priority habitat for conservation in the European Union. In the Camargue (Rhône delta, south of France), these meadows are heavily colonized by Phillyrea angustifolia shrub. In order to evaluate the respective roles of livestock and rabbits in Phillyrea control, we recorded and aged Phillyrea individuals in meadows subjected to 3 different treatments: grazing by rabbit plus traditional extensive grazing by cattle and horses from the beginning of the 1970s, grazing by rabbit only, and grazing by rabbit only with their temporary elimination in 1987. We found little difference in either the age distribution or the density of Phillyrea individuals between meadows grazed and ungrazed by domestic herbivores. In meadows where rabbits were temporarily eliminated we recorded a strong increase in the number of Phillyrea individuals from the time of this exclusion onwards. In addition, we aged Phillyrea shrubs in 35-y-old experimental plots grazed by cattle, horses, and rabbits, grazed by rabbits only, or ungrazed by livestock or rabbits. We found 90% of Phillyrea individuals in the plots ungrazed by rabbits. Thus, the current decline of rabbit populations appears to be a new threat for Mediterranean xero-halophytic meadows.

Neotropical bats exhibit great diversity in terms of resource use, so their species richness can vary both spatially and temporally over fine and coarse scales. In this paper we analyze the relative contribution of the alpha (a) and beta (β) components of bat species richness at different spatial and temporal scales in deciduous and semideciduous tropical forests in Yucatan, Mexico. We used different levels of the spatial (understory and subcanopy height, site, and vegetation type) and temporal (sampling period within a night, sampling night, and season) dimensions. For the spatial dimension, we found that the finer level (α) accounted for more than 50% of total richness and was higher (72% of total richness) within the semideciduous tropical forest. Although lower than for a, the percentage contribution of β among sites and β between vegetation types was higher than expected by chance. For the temporal dimension, α contribution was lower than 25% of total richness in all cases, while β at different time scales had a great influence on bat species richness. Our results indicate that the species composition of bat assemblages is dynamic in space and time. Thus, a proper assessment of diversity requires the inclusion of a variety of spatial and temporal scales in sampling designs.

Ecological theory suggests that environmental filtering (the survival or elimination of species in the community in response to environmental constraints) is a key process in the species assemblages of communities. Environmental filters, such as sand movement and soil salinity in coastal dunes and beaches, may result in shared ecological tolerances and functional types, independently of phylogenetic and evolutionary history. In 19 beach—foredune sites located along the coast of the Gulf of Mexico we studied plant functional composition and diversity of vascular plants. Functional groups were determined with a classification analysis. Relative importance values and diversity indices of species and functional groups were compared with ANOVA tests. We distinguished 5 groups: a group of species tolerant to soil salinity and burial, most abundant on accreting beaches; a group of species tolerant only to burial, which were abundant on all coasts; and 3 groups that lacked specific responses to burial and soil salinity and were most abundant on stable and erosive coasts. Accreting foredunes showed the lowest species richness and functional diversity, because only a few species were tolerant to burial and soil salinity. In the foredune environment, sediment dynamics and geomorphological processes act as environmental filters that largely determine the floristic and functional composition of the community.

The invasion of Norway maple (Acer platanoides) into North American forests is considered to have deleterious effects on native flora richness. One explanation for Norway maple's success is that it may have escaped its natural enemies and thus is less predated upon than its indigenous congener, sugar maple (Acer saccharum). However, Norway maple has been recently reunited with one of its natural enemies from Europe, Rhytisma acerinum, an adventive fungus that causes tar spot disease. The study reported here quantified the impacts of the disease on the growth and survival of Norway maple. In the urban forest of Mount Royal, we compared the growth of maple saplings and trees before the disease was first observed and after tar spot outbreaks of 2006 and 2007. We found a strong link between the outbreak of the disease and a very sharp decline in sapling and tree growth, together with high mortality of Norway maple saplings that could not be attributed to normal senescence or detrimental climatic conditions. While Norway maple usually exhibits higher growth rates than sugar maple, the reverse situation was observed after the epidemics. Our results suggest that the invasion potential of Norway maple could be reduced by the exotic disease.

Fish can affect amphibian larvae directly through consumption or indirectly by eliciting antipredator behaviours that incur fitness costs. Because of predation, long-toed salamanders (Ambystoma macrodactylum) typically show an allotopic distribution with fish. Linnet Lake (Waterton Lakes National Park, Alberta, Canada) represents the unusual situation in which salamanders coexist with a small-bodied cyprinid, lake chub (Couesius plumbeus). However, the salamander population resident to Linnet Lake has declined in recent years. Our objective was to assess the role of lake chub in the decline of this salamander population by combining field observations and laboratory experiments. We used mark-recapture techniques to estimate the size of the 2 populations. We found little evidence of successful salamander reproduction, and the adult population had decreased by 60% in 14 y. In contrast, a large population of lake chub was present. Experiments showed that lake chub between 70 and 100 mm could consume salamander larvae < 40 mm in length. Larvae responded to the presence of lake chub by reducing activity and increasing refuge use, especially during the day. Our study is one of few to document the ability of a native small-bodied fish to consume amphibian larvae. The coexistence of fish and salamanders may result from a dynamic interplay between periodic extirpation of fish by winter hypoxia and of salamanders by predation, punctuated by episodes of re-colonization or strong recruitment.

Seed dispersal along watercourses can favour the long-distance migration of invasive species, not only for aquatic or wetland species, but also for terrestrial wind-dispersed plants. It is crucial to investigate the role of watercourses in the dispersal of the knotweed hybrid complex (Fallopia × bohemica) due to its frequent occurrence on riverbanks and production of fertile achenes. For this purpose, we experimentally studied buoyancy and germinability of F. × bohemica achenes in stirred water, over 28 d. We also measured the long-term survival and growth of seedlings according to exposure time to water. After nearly 2 d in the water, 50% of achenes were still afloat. After 3 d, germination occurred in water and the seedlings also floated. Moreover, the exposure of achenes to water, for however long, significantly favoured their germination rate, without affecting seedling survival, compared to a direct planting in soil. Furthermore, a maximum seedling dry mass was reached following exposure to water for 277 h (11.5 d), surpassing significantly the dry mass of seedlings planted directly in soil. Water exposure strongly favours achene germination and seedling survival. Our results demonstrate a high potential for the seeds and seedlings of Fallopia to be dispersed successfully by water.