Showing papers in "Ecoscience in 2001"
TL;DR: It is suggested that males would experience senescence in survival earlier than females in a non-hunted population, and an increase in hunting mortality with age for both sexes, with males facing a higher risk of dying than females.
Abstract: We tested whether the ungulate moose (Alces alces) showed senescence in survival Senescence, ie, a progressive deterioration with age, may be obscured by multiple mortality causes in a wild population Thus, we followed radio-marked individuals of known age to separate different mortality causes in adult moose The risk of dying of causes not linked to humans increased with age For females, the increase in natural mortality was first observable after age 10 Tooth wear was significantly related to age for both sexes, but was stronger for males It suggests that males would experience senescence in survival earlier than females in a non-hunted population The senescence in mortality observed for female moose may be a result of delayed cost of reproduction acting in concert with tooth wear due to a reduced ability to process food We also found an increase in hunting mortality with age for both sexes, with males facing a higher risk of dying than females The age-related hunting mortality may be
106 citations
TL;DR: The effect of the spittlebug Philaenus spumarius on the reproductive output of the monocarpic forb Rudbeckia hirta is examined.
Abstract: In this study, I examined the effect of the spittlebug Philaenus spumarius on the reproductive output of the monocarpic forb Rudbeckia hirta Herbivores may affect reproductive output either by red
66 citations
TL;DR: This article examined the relationship between contemporary vegetation and surface soil phytolith assemblages, and used phytolines and d13C of soil organic matter (SOM) to explore forest-gr
Abstract: Our objectives were to examine the relationship between contemporary vegetation and surface soil phytolith assemblages, and use phytoliths and d13C of soil organic matter (SOM) to explore forest-gr
57 citations
TL;DR: Results of the rates of thermal time constants suggest mechanisms to cope with the fast decrease of environmental temperature that occurs in the desert during the mid-afternoons and the manner in which selection of low body temperatures may allow survival in desert conditions is discussed.
Abstract: The behavioral and physiological thermoregulation of three Atacama desert-dwelling Liolaemus lizards was studied and compared with previous data on Liolaemus from other ecosystems The thermoregulatory mechanisms of the desert-dwelling species differed from those of the others, a consequence of differences in the habitat structure of the species Desert species have higher critical thermal minima and, contrary to expectations, lower selected body temperatures than Liolaemus from Mediterranean environments Results of the rates of thermal time constants suggest mechanisms to cope with the fast decrease of environmental temperature that occurs in the desert during the mid-afternoons Finally, the manner in which selection of low body temperatures may allow survival in desert conditions is discussed
55 citations
TL;DR: In this paper, the authors analyzed the risk of browsing on aspen trees in the temperate and boreal landscape due to heavy browsing and found that browsing on the aspen can result in the regeneration of several tree species.
Abstract: There is considerable circumpolar concern regarding the regeneration of several tree species in the temperate and boreal landscape due to heavy browsing We analyzed the risk of browsing on aspen (
55 citations
TL;DR: In this paper, the authors compared rural and forest coyotes in northeastern North America under the hypothesis that the forest landscape represents a marginal habitat for this species, and concluded that eastern coyotes cannot replace gray wolves in this biome, and speculate on the consequences of the arrival of this new predator for the conservation of other mesocarnivores.
Abstract: We compared rural and forest coyotes in northeastern North America under the hypothesis that the forest landscape represents a marginal habitat for this species. We predicted that forest coyotes would have larger home ranges and higher rates of mortality and/or emigration than rural coyotes. We also predicted that coyotes would select for open habitats in both landscapes throughout the year, and would not follow white-tailed deer in their migration to wintering areas. Forest (n = 14) and rural (n = 10) coyotes foraged over 89 and 27 km2, respectively, during the trapping season (18 October - 1 March), and over 1 1 1 and 48 km2 during the rest of the year. Annual survival rate did not vary significantly ( P = 0.34) between adult forest and rural coyotes, averaging 74% and 60%, respectively; pups died at a higher rate in both landscapes (P < 0.01). All monitored coyotes died from anthropogenic factors, mostly from trapping. Forest coyotes exhibited a tendency to disperse and to make forays in the rural landscape where some died. We detected no selection for open habitats, irrespective of season or landscape, nor did coyotes show a strong preference for deer wintering areas. However, coyotes with deer wintering areas in their home ranges intensified their use of these areas when deer concentrated in them between December and April. We conclude that the forest landscape of northeastern North America possesses a low carrying capacity for coyotes even in the absence of wolves. We also conclude that eastern coyotes cannot replace gray wolves in this biome, and we speculate on the consequences of the arrival of this new predator for the conservation of other mesocarnivores.
50 citations
TL;DR: A large sample size, plus the fact that these plants develop in patches in which stems are frequently in contact, suggested that a certain selectivity occurs for plant choice by ant workers.
Abstract: In contrast to many myrmecophytes, which shelter ants in hollowed structures called domatia, plants bearing extrafloral nectaries do not have specific relationships with certain ant species. However, we hypothesized that different plants might be associated with different assemblages of ants. We studied three pioneer plant species from French Guiana: Passiflora glandulosa, Passiflora coccinea (Passifloraceae) and Mimosa myriadena (Mimosaceae) that occur together in the same habitat. The guild of ants associated with each of these plants was different from the overall ant community in the study area. Ant assemblages varied among plant species and, for a given plant species, from day to night. Certain ant species frequent in the study area were rare or even absent on these plants, even species known to be very aggressive at the interspecific level, such as Wasmannia auropunctata. While territoriality between ant species probably plays some role in determining distributions across plants, differentia...
44 citations
TL;DR: In this paper, the authors show that anuran richness in 77 southeastern Ontario wetlands is negatively correlated with the density of roads on lands within 1 km of the wetland, and positively associated with the percentage of forest cover.
Abstract: In light of increasing evidence of declining anuran populations worldwide, an important conservation issue is the extent to which declines are consequences of smaller-scale stresses such as local habitat loss or degradation, or larger-scale stresses such as climate change Here we show that anuran richness in 77 southeastern Ontario wetlands is negatively correlated with the density of roads on lands within 1 km of the wetland, and positively correlated with the percentage of forest cover Logistic regression analysis shows that the presence of at least two species, the mink frog (Rana septentrionalis) and the wood frog (Rana sylvatica), is negatively related to road density, while the pickerel frog (Rana palustris) shows significant positive association with adjacent forest cover These results suggest that in southeastern Ontario, significant conservation gains can be achieved through local land-use planning and management decisions that mitigate the effects of existing roads, minimize the const
42 citations
TL;DR: It was showed that deer browsing delayed vertical and radial growth and altered the stand structure in favor of white spruce, and browsing intensity on fir may increase in years to come because of an expected higher site attendance and increased spruce budworm activity.
Abstract: White-tailed deer (Odocoileus virginianus Zimmermann) was introduced on Anticosti Island in the late 1890s. The current population, estimated at 120 000 (15 animals/km2), jeopardizes balsam fir (Abies balsamea [L.] Mill.) growth and recruitment to the canopy. Balsam fir is a preferred browsed species of white-tailed deer during winter. In a second-growth stand resulting from a clearcut and a fire in 1959, we investigated the stand structure and developmental patterns of fir stems using dendroecological methods. White spruce (Picea glauca [Moench] Voss), a less palatable, occasionally browsed species, was used as a control to evaluate the influence of repeated browsing on fir and to differentiate it from the possible effects of other factors. Our data showed that deer browsing delayed vertical and radial growth and altered the stand structure in favor of white spruce. Browsing resulted in a semi-open stand with a tree layer dominated by white spruce and a scattered understory of predominantly small...
38 citations
TL;DR: In this article, the authors analyzed scat contents to study seasonal variations in coyote diet, from January to December 1996, between a protected area (Kouchibouguac National Park, New Brunswick, N = 311) and an adjacent unprotected area (N = 364).
Abstract: In forested areas of the northern portion of their range, coyote (Canis latrans) populations are thought to depend mainly on areas disturbed by humans Within a forested landscape, we analyzed scat contents to study seasonal variations in coyote diet, from January to December 1996, between a protected area (Kouchibouguac National Park, New Brunswick, N = 311) and an adjacent unprotected area (N = 364) Coyote diet changed significantly between May-July and August-September in both areas, and between October-December and January-April in the protected area From January to July, the proportion of snowshoe hare (Lepus americanus) in coyote diet was significantly higher in the unprotected area than in the protected area, but no other items differed between areas Diet also differed between the two areas during August-December In the protected area, the proportion of mammals in the diet was significantly lower, while the proportions of fruits and insects were significantly higher Diet diversity was
38 citations
TL;DR: Results converge with other studies in demonstrating that the success of hybrid frogs depends on niche partitioning along an ecological gradient, which is probably a relevant templet for water frog evolution.
Abstract: The hypothesis of hybrids occupying intermediate niche was tested in the water frog hybridogenetic complex by investigating the variation of assemblage compositions in different habitats along a gradient of river influence in a large floodplain (upper Rhone, France) The parental species strongly differed in their habitat use Whereas Rana ridibunda Pallas occupied dead arms close to the active channels, Rana lessonae Camerano occupied marsh ponds The hybrid Rana kl esculenta Linnaeus was found in the same ponds as Rana lessonae, as expected in L-E systems where Rana kl esculenta females act as sexual parasites of Rana lessonae males However, the proportions of each of these two taxa in mixed assemblages varied according to the degree of river influence, with Rana kl esculenta predominating in ponds experiencing an intermediate level of flooding (alluvial marsh) and Rana lessonae predominating in less frequently flooded ponds (peat marsh) These results converge with other studies in demonstr
TL;DR: The impact of fire on the viability of the entire soil seed bank in a Mediterranean pasture dominated by weeds originating from arable fields, and its recovery in the first post-fire year, were investigated in this article.
Abstract: The impact of fire on the viability of the entire soil seed bank in a Mediterranean pasture dominated by weeds originating from arable fields, and its recovery in the first post-fire year, were inv
TL;DR: Wetlands in continental western Canada are a significant, active biosphere carbon sink following accumulation patterns of the last one thousand years, and future changes, particularly in fire frequency or intensity, may alter this accumulation pattern.
Abstract: Net primary production in wetlands of continental western Canada (Alberta, Saskatchewan, Manitoba) is mapped and summarized by wetland type and ecoregion. The region contains 405 300 km2 of wetlands, with peatlands representing 90.1% of all wetlands. Based on a regional synthesis of published values of net primary production, shrubby swamp and marsh wetlands produce more biomass annually through the process of net primary production than peatlands. Different peatland types appear to sequester similar amounts of plant biomass on an annual basis, with the exception of permafrost bogs that sequester less. Wetland net primary production for the region is calculated as 2.1 ¥ 1014 g yr-1 of plant biomass, with 73.5% sequestered in peatlands. This is equivalent to 9.95 ¥ 1013 g yr-1 of carbon. Provincially this carbon is partitioned into 50% for Manitoba, 30% for Alberta, and 20% for Saskatchewan. Over the last 1000 years, an average of only 5% of this biomass (and carbon) accumulate as peat, with most l...
TL;DR: The mechanisms and developmental sequence that allow the growth, maintenance and expansion of long-lived (several hundred years old to more than one thousand years old), stunted black spruce clones are examined using architectural and tree ring analyses.
Abstract: Black spruce (Picea mariana [Mill.] BSP.) is the dominant tree species across the North American boreal forest. In the northernmost parts of its natural range, the species thrives in the form of scattered or aggregated stunted clones (krummholz) in winter-exposed subarctic and arctic sites. In this study, we have examined the mechanisms and developmental sequence that allow the growth, maintenance and expansion of long-lived (several hundred years old to more than one thousand years old), stunted black spruce using architectural and tree ring analyses. The development of stunted black spruce clones is the result of the reiteration potential of the species through layering. Exposed snow-drift sites are favourable to layering because branches are maintained close to the soil surface; these site conditions promote layering through adaptive reiteration associated with dedifferentiation of growing axes. Because the lower branches are held near the soil surface and buried beneath the litter, the formati...
TL;DR: The dynamics indices provide an easily quantified measure of the diversity dynamics at various scales and, specifically, provide a measure of within-habitat temporal turnover in habitats where P can be reliably evaluated.
Abstract: A simple, yet highly promising method of quantifying temporal diversity dynamics is to use the ratio of mean species richness, S, to potential species richness, P (cumulative S at a locality). In a rock pool meta-community of aquatic micro-invertebrates, this ratio, which we call the dynamics index (I), proved reliable as a predictor of assemblage type. We calculated within-habitat diversity dynamics for each of 49 pools that differed in environmental variability. The resulting dynamics indices provide an easily quantified measure of the diversity dynamics at various scales and, specifically, provide a measure of within-habitat temporal turnover in habitats where P can be reliably evaluated.
TL;DR: It is concluded that computing LPI values for the entire landscape as a single window is inappropriate for testing habitat selection at the home range scale, and that windows of similar size as the home ranges should be used instead.
Abstract: Habitat selection studies at the home range scale involve testing whether an animal selects a particular spatial arrangement of habitats within a landscape We propose a technique based on comparin
TL;DR: Evidence is presented for a short-term reduction of ant activity on extrafloral nectaries (EFNs) of Passiflora coccinea after episodes of rainfall, suggesting the anti-herbivore activity of ants visiting EFNs may be constrained by rainfall.
Abstract: In this study we present evidence for a short-term reduction of ant activity on extrafloral nectaries (EFNs) of Passiflora coccinea (Aubl., Passifloraceae) after episodes of rainfall. We monitored ant attack of simulated herbivores (termites) before and after watering treatments on reproductive branches of P. coccinea and the adjacent vegetation, in the lowland moist forest of French Guiana. Besides a delayed ant response, watering resulted in reduced rates of encounter, attack, and removal of termites. Other kinds of disturbances, such as herbivore presence, artificial and natural damage, or even shaking have been shown to induce increased ant activity on ant-plants. In contrast, rain events may be considered a type of disturbance that reduces ant activity. Consequently, the anti-herbivore activity of ants visiting EFNs may be constrained by rainfall.Keywords: Amazon forest, ant-plant interaction, extrafloral nectaries, French Guiana, Passiflora coccinea, rainfall, temporal variability.
TL;DR: In the mixedwood boreal forest of northeastern Alberta, Alberta-Pacific Forest Industries Inc alters cutblock size, structure, and distribution over the landscape to simulate fires, the dominant disturbance type as mentioned in this paper.
Abstract: Ecosystem management is a theoretical framework in which land managers attempt to approximate natural disturbance with harvesting practices In the mixedwood boreal forest of northeastern Alberta, Alberta-Pacific Forest Industries Inc alters cutblock size, structure, and distribution over the landscape to simulate fires, the dominant disturbance type In 1997 and 1998, we sampled for Rana sylvatica (Le Conte) and Pseudacris triseriata maculata (Wied-Neuwied) near Owl River and Mariana Lake, Alberta, in undisturbed, harvested, and naturally burned landscapes We compared patterns of distribution and relative abundance using transects, time-constrained lake margin searches, and opportunistic detections In 1998, we characterized the understory, shrub layer, and canopy layer on each transect We used stepwise logistic regression to describe microhabitat use by each species We did not detect consistent differences between burned and logged areas This may reflect pre-treatment variation in regional
TL;DR: Roosts and food supply appear to insulate M. lucifugus from the effects of cool, wet weather, and greater use of clustering by roosting bats is suggested.
Abstract: At the Chautauqua Institution in southwestern New York State, the period between May and September in 1991 differed in rainfall and temperature from the same period in 1992 1992 was significantly cooler and wetter than 1991, reflecting the global impact of the 1991 eruption of Mt Pinatubo Some buildings at the Institution are used as nursery roosts by thousands of Myotis lucifugus (little brown bats) and in one roost, maximum temperatures were significantly lower in 1992 than in 1991 There were no significant differences between these two summers in the diet of M lucifugus, which mainly comprised aquatic insects that did not differ significantly in availability There were significant differences in the numbers of bats using some roosts between years, with more bats in larger colonies and fewer in smaller colonies in 1992 This suggests greater use of clustering by roosting bats, which was supported by direct observation There were no significant differences between years in the timing of rep
TL;DR: Reduced optomotor performance has the potential to affect a host’s ability to detect and respond to prey, predators and conspecifics.
Abstract: Many populations of fathead minnows (Pimephales promelas Rafinesque) in northern Alberta, Canada, contain individuals with hundreds of trematode (Ornithodiplostomum ptychocheilus Faust) cysts on th
TL;DR: In 1998, the worst ice storm of the last century hit regions of southeastern Ontario, Quebec, New Brunswick, and the northeastern United States using standard multiple regression as mentioned in this paper, which was the first time for such an event.
Abstract: In January 1998, the worst ice storm of the last century hit regions of southeastern Ontario, Quebec, New Brunswick, and the northeastern United States Using standard multiple regression a
TL;DR: It is suggested that hosts can resist high parasite pressures, and understanding the mechanisms involved in host-parasite interactions requires both experimental and long-term multi-factor analyses.
Abstract: The impact of nest ectoparasites on chicks was studied for the first time in a free-living North African cavity nesting bird, an Algerian population of blue tits, Parus caeruleus ultramarinus The
TL;DR: The results have shown that the effects of biotic factors may change from facilitation at emergence, to competition at the seedling stage, and depended on physical stress, and on the intensity and distribution of damage, while growth depended on the competitive conditions.
Abstract: We investigated the effects of competition, abiotic factors and defoliation on the emergence, survival and growth of downy oak (Quercus pubescens Willd.). Acorns were sown in three types of vegetation (annuals, perennials, perennials and Brachypodium phoenicoides), combined with two abiotic factors (addition of water and nutrients, shade). Three months after emergence, three defoliation treatments were performed including the ablation of stem and leaves, removal of half of the leaves and removal of the half blade of each leaf. Seedlings from heavier acorns emerge more frequently and survive better after browsing than those with a lighter mass. The highest percentages of seedling emergence were observed in the plots with Brachypodium phoenicoides, showing a facilitative effect of grasses. Shade as well as water and nutrient addition increased the survival of seedlings after defoliation. Seedlings whose stems were cut had lower survival rates than controls. Competition with Brachypodium phoenicoides significantly decreased leaf biomass but did not increase the mortality of individuals. Overall, our results have shown that the effects of biotic factors may change from facilitation at emergence, to competition at the seedling stage. Finally, emergence, survival and the responses to herbivory depended on physical stress, and on the intensity and distribution of damage, while growth depended on the competitive conditions.
TL;DR: A range of anatomical features of northern leopard frogs collected from areas where deformity rates were low and high were compared to determine if one or more of these characters might be useful in detecting developmental stress.
Abstract: We compared a range of anatomical features of northern leopard frogs (Rana pipiens Schreber) collected from areas where deformity rates were low (-2% in nonstressed regions) and high (-40% in the stressed region) to determine if one or more of these characters might be useful in detecting developmental stress Deformed individuals from the stressed region were significantly lighter than normal frogs both from the same region and from nonstressed regions Body length, head width, femur length, and forelimb length were also significantly shorter in deformed and normal individuals from the stressed region than in individuals from nonstressed regions Despite being smaller, deformed individuals had significantly larger pigment spots Fluctuating asymmetry in femur length, femur spot area, femur spot number, and tibio-fibula length was significantly greater in deformed frogs than in normal frogs from the stressed population and the nonstressed group Of these characters, however, only femur spot number
TL;DR: In this article, the authors show that variation in the composition of spider communities can be related to the management conditions of dry grassland, where spiders are very sensitive to habitat conditions.
Abstract: The spider communities of dry grassland are diverse and very sensitive to habitat conditions This paper shows that variation in the composition of spider communities can be related to (i) manageme
TL;DR: It is concluded that despite the terrestrial agility problems suspected to hinder aerial insectivores, they are capable of collecting calcium-rich objects, and that the growth rate of their young is not limited by a calcium-deficient diet.
Abstract: The calcium content of insects is postulated to be insufficient to meet the high demands of skeletal growth incurred by nestling insectivorous birds To compensate for this calcium deficiency, adul
TL;DR: This is the first experimental study on the cost of reproduction in a long-lived woody species showing clear trade-offs, and it is shown that there is no detectable trade-off between the male and female functions.
Abstract: An organism has a finite amount of resources which must be allocated to different functions such as maintenance, growth and reproduction. In cosexual plants, allocation to reproduction is in both m...
TL;DR: Many farmland bird species are declining in North America and Europe, yet there are few data documenting bird use of agricultural landscapes, especially in Canada This information is needed in order to predict the future of farmland bird populations as discussed by the authors.
Abstract: Many farmland bird species are declining in North America and Europe, yet there are few data documenting bird use of agricultural landscapes, especially in Canada This information is needed in ord
TL;DR: Sapling bank dynamics is influenced not only by the difference between closed canopy and gap but also by the Difference between evergreen and deciduous canopies, and the main factor of this influence may be an understory light environment.
Abstract: Sapling bank dynamics under different canopy conditions were examined in 1997-1999 in a subalpine old-growth forest of the northern Yatsugatake Mountains, central Japan Three 5 m × 5 m quadrats es
TL;DR: Ammophila breviligulata is a pioneer plant on coastal dunes of northeastern North America, where it forms dense, monospecific stands on the foredune as discussed by the authors.
Abstract: American beachgrass (Ammophila breviligulata) is a pioneer plant on coastal dunes of northeastern North America, where it forms dense, monospecific stands on the foredune Although both pla