Jocelyn Martel

York University · Glendon Bilingual Biology Program

Vole damage to woody plants reflects cumulative rather than peak herbivory pressure. — Ann. Zool. Fennici 50: 189–199. Vole grazing may be a step-function, with a critical threshold density, at which voles expand their preferred diet to lower quality forage (threshold herbivory hypothesis). Accordingly, we predicted that the establishment of unpala...

Overall, mammalian herbivores are more harmful in mixed plantations than in monocultures, but the effect of herbivore abundance has not been experimentally tested in this context. It has been proposed that there is a critical threshold density where herbivore pressure spreads from preferred plants to everything edible, leading to non-linear density...

Abstract 1. The phenological window of opportunity hypothesis posits that an insect herbivore cannot survive outside a specific leaf age interval of its host plant. 2. Previous studies have shown that mountain birch displays extensive seasonal changes in leaf biochemical characteristics. Young, expanding leaves are full of water and amino acids but...

Most insect herbivores are specialised on a particular plant taxon. To have a better understanding of host shift functions and consequences for insect herbivores, it is essential to gather more information on the effects of variation in host quality on specialists across species and environments. We examined the effects of seasonally atypical food...

We studied how fluctuating asymmetry (FA), which is commonly used as an non-specific stress indicator, is influenced by abiotic stress along a moisture gradient and by rapid growth, i.e. the production of larger than normal leaves after simulated browsing, in white birch (Betula pubescens) growing in a mire. Variation of abiotic stress (plots near...

M. 2002. Developmental plasticity in birch leaves: defolia-tion causes a shift from glandular to nonglandular trichomes. – Oikos 98: 437– 446. The structures on leaf surfaces, e.g. trichomes, can act as effective antiherbivory mechanisms as chemical repellents. Structural defences usually represent constitutive resistance, but there are also a few...

Fluctuating asymmetry (FA) is used to describe developmental instability in bilateral structures. In trees, high FA of leaves has been assumed to indicate the level of environmental or genetic stress, and for herbivores leaves from such trees have been shown to be in some cases (though not invariably) of higher quality compared to trees with symmet...

Abundant nitrogen improves seedling growth and establishment. Vigorous growth brings about changes in rates and patterns of plant development and changes in the relationship between primary and secondary metabolism, which may make seedlings more susceptible to herbivores and pathogens than are slow-growing seedlings. We studied how nitrogen fertili...

A greenhouse experiment was conducted to study the indirect effects of soil salinity on a caterpillar that induces gall formation on a non-halophilic plant. Larvae of Epiblema scudderiana (Clemens) were allowed to feed on potted goldenrods (Solidago altissima L.) treated with 3 concentrations of NaCl (0, 8,000, 16,000 PPM). Experiments were also ca...

Forest decline can be the result of multiple stresses such as air pollution or natural processes. This phenomenon can directly affect trees as well as the fauna and nonarborescent nora within these ecosystems. From 1987 to 1989 we studied insectivorous bird, arthropod, and plant populations in 18 sugar maple (Acer saccharum Marsh.) stands affected...

We surveyed immature lepidopteran communities in maple forests with varying degrees of forest decline over three consecutive growing seasons (June, July and August; 1987-1989), assuming that leaf-feeding Lepidoptera would be positively influenced by slight or moderate stress to trees. We sampled and identified the species and feeding habits of larv...

Populations of Eurosta solidaginis Fitch and Epiblema scudderiana (Clemens) attacking ramets of Solidago altissima L. were sampled in 1991 and 1992 on road margins (10 and 60 m from the road edge)in the Ottawa metropolitan area to investigate the effects of roadside conditions on the performance of gall-forming insects and their host plants. The gr...

A transplant experiment using potted plants was performed over two years in a field located along a heavily used highway to test for the effects of seasonal variations in roadside conditions on the performance of a gall-forming insect, Eurosta solidaginis Fitch, and its perennial host plant, Solidago altissima L. The experiment was designed to sepa...

A canopy thinning index (CTI) based on severity and incidence of dieback, and on tree basal area was calculated for each of the 72 stations sampled. Analysis of variance shows that canopy dieback had a significant effect on carabid beetle activity in 1988. The CTI was negatively correlated with the carabid species richness and diversity. Number of...

A study was carried out during the summers of 1987 and 1988 in healthy and declining maple forests in southeastern Quebec to estimate the impact of forest decline on the litter's invertebrate mesofauna communities. Insects, arachnids (opilions and spiders), gastropods, and myriapods were the four major groups sampled. The class Insecta represented...