The effect of biodiversity on the ability of parasites to infect their host and cause disease (i.e. disease risk) is a major question in pathology, which is central to understand the emergence of infectious diseases, and to develop strategies for their management. Two hypotheses, which can be considered as extremes of a continuum, relate biodiversity to disease risk: One states that biodiversit...

The risk of Lyme disease for humans in the eastern United States is dependent on the density of host-seeking Ixodes scapularis Say nymphal stage ticks infected with Borrelia burgdorferi. Although many local and regional studies have estimated Lyme disease risk using these parameters, this is the first large-scale study using a standardized methodology. Density of host-seeking I. scapularis nymp...

Seasonal multiplication and overwinter survival are density-dependent in Heterodera glycines. At low to moderate population densities, the nematode is capable of large population increases on susceptible soybean cultivars and high rates of oversummer or overwinter survival in the absence of a host. To improve estimates of H. glycines multiplication and survival rates, egg densities were monitor...

a two-year laboratory study on the biology (including self-fertilization) of bulinus truncatus, the intermediate host of schistosoma haematobium, s. bovis and paramphistomum microbotrium in iran, has revealed information on the longevity, reproduction, hatchability rate, hatching time during various months of the year, and growth and mortality rates of this snail. it was found that the reproduc...

The host galaxies associated with GRBs are observed to have magnitudes R ∼ 25. Here we compare the observed redshifts and magnitudes of the host galaxies with the predictions of three basic models: the comoving rate density of GRBs is (1) proportional to the cosmic star formation rate density, (2) proportional to the total integrated stellar density and (3) constant. All models make the assumpt...

We consider a framework for bi-objective network construction problems where one objective is to be maximized while the other is to be minimized. Given a host graph G = (V,E) with edge weights we ∈ Z and edge lengths `e ∈ N for e ∈ E we define the density of a pattern subgraph H = (V ′, E′) ⊆ G as the ratio %(H) = ∑ e∈E′ we/ ∑ e∈E′ `e. We consider the problem of computing a maximum density patt...

Destructive host-feeding is common in hymenopteran parasitoids. Such feeding may be restricted to host stages not preferred for oviposition. However, whether this is a fixed strategy or can vary according to resource levels or parasitoid needs is less clear. We tested the trade-off between host feeding and oviposition on two whitefly parasitoids under varying host densities. Females of two aphe...

1. It is widely accepted that density-dependent processes play an important role in most natural populations. However, persistent challenges in our understanding of density-dependent population dynamics include evaluating the shape of the relationship between density and demographic rates (linear, concave, convex), and identifying extrinsic factors that can mediate this relationship. 2. I studi...

Predators and parasites that eavesdrop on the mating signals of their prey often preferentially select individuals within a prey/host species that produce specific cues. Mechanisms driving such signal preferences are poorly understood. In the tungara frog Physalaemus pustulosus, conspecific females, frog-eating bats, and blood-sucking flies all prefer complex to simple mating calls. In this stu...

Experimental studies have shown that parasites can reduce host density and even drive host population to extinction. Conventional mathematical models for parasite-host interactions, while can address the host density reduction scenario, fail to explain such deterministic extinction phenomena. In order to understand the parasite induced host extinction, Ebert et al. (2000) formulated a plausible...