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In the tropical dry forest of the central Pacific coast of Mexico the pollination and reproductive success of the bombacaceous tree Ceiba grandiflora was negatively affected by habitat disruption. Two of the three bat species that function as effective pollinators for this species (Glossophaga soricina and Musonycteris harrisoni) visited flowers found in trees in disturbed habitats significantly less...
Ants are a major environmental factor for many insect species. For example, aphids and lycaenids have evolved an array of associations with ants ranging from obligate myrmecophily to the avoidance of contact. Here we (1) analyze the predictive power of different ecological and morphological traits for explaining the strength of the association between ants and aphids/lycaenids and (2) contrast different...
Changes to the radiative environment arising from stratospheric ozone (O3) depletion and subsequent associations between these changes and the pigmentation of the moss Andreaea regularis were measured in late austral spring and early summer 1998at Rothera Point on the western Antarctic Peninsula (67S, 68W). A strong relationship between O3 column depth and the ratio of UV-B to PAR irradiance (Fuv-b/Fpar)...
Maternal phenotype and maternal environment can profoundly affect the phenotype and fitness of offspring. Yet the causes of variation in such maternal effects are rarely known. Embryos in avian eggs cannot develop without being incubated and this creates an opportunity for maternal control of duration and onset of offspring development. However, females might adjust the start of incubation (e.g.,...
Parasitism influences many aspects of a hosts behavior and physiology. Therefore, parasitism is also likely to influence the competitive ability of the host. Field populations of phytophagous insects are often a mix of parasitized and unparasitized conspecifics and the inclusion of parasitism in their competitive dynamics may alter expected outcomes. We investigated the influence of parasitism by...
The physical structure of a habitat generally has a strong influence on the diversity and abundance of associated organisms. I investigated the role of coralline algal turf structure in determining spatial variation of gastropod assemblages at different tidal heights of a rocky shore near Sydney, Australia. The structural characteristics of algal turf tested were frond density (or structural complexity)...
The mast depression hypothesis has been put forward to explain the 9- to 10-year population cycle of the autumnal moth (Epirrita autumnata; Lepidoptera: Geometridae) in northern Fennoscandia. We analysed long-term data from Finnish Lapland in order to evaluate the critical assumption of the mast depression hypothesis: that better individual performance of herbivores, followed by high annual growth...
We tested the relationship between Sphagnum growth and the amount of nitrogen stored in free amino acids in a fertilisation experiment with intact peat monoliths in an open greenhouse in The Netherlands. Three nitrogen deposition scenarios were used: no nitrogen deposition, field conditions and a doubling of the latter, corresponding to 0, 40 and 80kg N ha1 year1. Growth of Sphagnum as expressed by...
Invasive plants are often larger in their introduced range compared to their native range. This may reflect an evolved reduction in defense and increase in growth in response to low herbivory in their introduced range. Key elements of this scenario include genetic differences in defense and growth yet uniformly low rates of herbivory in the field that dissociate defense and herbivore damage for alien...
Food quantity and especially food quality are thought to be key factors driving reproductive changes in the house mouse, Mus domesticus, leading to outbreaks of house mouse populations in the Australian grain-growing region. Characteristic changes during an incipient mouse plague are an early start of breeding, a high proportion of females breeding at a young age and a prolonged breeding season. We...
Fruit abortion has been hypothesized to be a parental means of selective removal of propagules with low viability. In particular, aborted zygotes have been suggested to have developmentally deviant phenotypes, and surviving offspring may therefore give rise to adults with a developmentally stable phenotype. We tested predictions from this hypothesis using acorns of holm oaks Quercus ilex as a model...
Two hypotheses of bottom-up control that predict that the species richness of Carabidae will depend either on the taxonomic diversity of plants (taxonomic diversity hypothesis) or on the structural heterogeneity of the vegetation (structural heterogeneity hypothesis) were tested. Plant species were classified into nine plant structural groups through cluster analysis of morphological traits (e.g....
Covariance between preference and performance was quantified for Papilio glaucus strains derived from a locally monophagous Florida population and a locally polyphagous Ohio population. I used two-choice assays to assess relative host preferences of mothers for plant species that represent reciprocal normal and novel hosts for each population (i.e., Liriodendron tulipifera and Magnolia virginiana)...
Species such as Dreissena polymorpha sometimes contribute substantially in the transfer of primary to secondary production. During the ontogenetic cycle, the reproductive investment of adult mussels is one of the main parameters that affect recruitment success. We studied how food quality and temperature affect the reproductive investment in term of egg mass of D. polymorpha in a lake by sampling...
Two field studies were carried out to determine the influence of Abies balsamea foliage age on the preference and performance of larvae of Neodiprion abietis, a specialist Diprionid sawfly. Preference was determined by examining N. abietis defoliation on all age classes of foliage. Performance was estimated using larval survival, cocoon weights and the percentage of adults that were females. Neodiprion...
We examined the potential of a leaf roller to indirectly influence a community of arthropods. Two mite species are the key herbivores on papaya leaves in Hawaii: a spider mite, Tetranychus cinnabarinus Boisduval, and an eriophyid mite, Calacarus flagelliseta, which induces upward curling of the leaf margin at the end of the summer when populations reach high densities. A survey and three manipulative...
This study explores the relationship between the normalized difference vegetation index (NDVI), aboveground plant biomass, and ecosystem C fluxes including gross ecosystem production (GEP), ecosystem respiration (ER) and net ecosystem production. We measured NDVI across long-term experimental treatments in wet sedge tundra at the Toolik Lake LTER site, in northern Alaska. Over 13years, N and P were...
In ungulates, tooth wear is often suggested as a proximate cause of senescence. Tooth wear is expected to be sex-dependent since energetic requirements and food selection varies largely between sexes in sexually dimorphic ungulates. Furthermore, tooth wear may lower mastication efficiency, and we predict a negative correlation between tooth wear and body weight or condition. We tested these predictions...
We examined avian communities of kopjes (naturally occurring insular rock outcrops) in grassland and thorn tree woodland habitats in the Seronera region of Serengeti National Park, northwestern Tanzania. Although kopjes cover a small proportion of the Parks area, they provide resources that are uncommon in the Serengeti landscape and are known to host diverse, yet poorly documented, biotic communities...
We tested the hypothesis that exposure of leopard frogs (Rana pipiens) to agricultural pesticides can affect the infection dynamics of a common parasite of ranid frogs, the lungworm Rhabdias ranae. After a 21-day exposure to sublethal concentrations of a pesticide mixture composed of atrazine, metribuzin, aldicarb, endosulfan, lindane and dieldrin, or to control solutions (water, dimethyl sulfoxide),...
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