Understanding factors that influence host-pathogen interactions is key to predicting outbreaks in natural systems experiencing environmental change. Many amphibian population declines have been attributed to an amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd). While this fungus is widespread, not all Bd-positive populations have been associated with declines, which could be attribu...

A greater knowledge of the morphology and the development of the infective third larval stage of Neoaplectana bibionis Bovien, 1937, a parasite of arthropods, makes it possible to recognise the second larval stage and present a description of all the developmental stages in the life cycle of the species. Four larval stages can be recognised. L1 hatches from the egg. In a suitable host, when the...

Field populations of aquatic organisms, particularly those inhabiting flowing waters, likely are exposed to short pulses of pesticides following periods of spray drift, surface runoff, or drain flow. In the present study, we investigated the effect of pulse exposures of a pyrethroid insecticide, esfenvalerate, on survival, development, and reproduction of the midge, Chironomus riparius. The fir...

We present the results of selection experiments designed to distinguish between antagonistic pleiotropy and mutation accumulation, two mechanisms for the evolution of senescence. Reverse selection for early-life fitness was applied to laboratory populations of Drosophila melanogaster that had been previously selected for late-life fitness. These populations also exhibited reduced early-age fema...

1. Hosts experiencing frequent variation in density are thought to benefit from allocating more resources to parasite defence when density is high (‘densitydependent prophylaxis’). However, high density conditions can increase intra-specific competition and induce physiological stress, hence increasing host susceptibility to infection (‘crowding-stress hypothesis’). 2. We studied monarch butter...

Dispersal heterogeneity is an important process that can compensate for downstream advection, enabling aquatic organisms to persist or spread upstream. Our main focus was the effect of year-to-year variation in larval dispersal on invasion spread rate. We used the green crab, Carcinus maenas, as a case study. This species was first introduced over 200 years ago to the east coast of North Americ...

The evolution of foraging in Drosophila melanogaster (Meigen) is studied using outbred populations that had been differentiated using laboratory selection. The foraging behaviour of Drosophila larvae is measured using the foraging path length of 72-h-old larvae. The foraging path length is the distance travelled by foraging larvae over 5 min. Populations of Drosophila selected for rapid develop...

Mediterranean flour moth, Ephestia kuehniella, is a cosmopolitan pest of stored products, and its eggs are widely used to rear parasitoids and predators for biological control programmes. This experiment investigated how larval population density affected the survival rate and reproductive output of this species under four rearing densities ( larva per 2 g food per vial; or 00, 500 or 000 larva...

An important question for mosquito population dynamics, mosquito-borne pathogen transmission and vector control is how mosquito populations are regulated. Here we develop simple models with heterogeneity in egg laying patterns and in the responses of larval populations to crowding in aquatic habitats. We use the models to evaluate how such heterogeneity affects mosquito population regulation an...

In an earlier study, exploitative intraspecific competition was demonstrated for middle instars of the caddisfly Helicopsyche borealis in Big Sulphur Creek, a stream in northern coastal California. This population is univoltine with early instars first appearing in June, growing into late instars the following spring, and emerging as adults in May. Competition occurs during the summer dry seaso...