Life Sciences Commons^™

1. We compare biases in estimates of the rate constant of the logistic and Gompertz functions applied to avian growth using three methods of parameter estimation. The methods differ in how the asymptote is determined, and consist of either floating asymptotes estimated from the full data (floating A) or data truncated at 70% of the adult mass (70%A), or fixing the asymptote at the adult mass (fixed A).

2. First, using data for two passerine species exhibiting different growth patterns, we truncated mass measurements at different ages to explore how each method of growth rate estimation responded to simulated differences …

Haemosporidian parasites of birds and mammals reproduce asexually inside nucleated and nonnucleated host erythrocytes, respectively. Because of these different parasite environments and because bird parasites are paraphyletic, we evaluated whether patterns of parasite molecular evolution differ between host groups. We compared two mitochondrial (mt) genes and one apicoplast gene across mammal Plasmodium, bird Plasmodium, and bird Parahaemoproteus. Using a molecular phylogenetic approach, we show that the parasite mt cytochrome b (cyt b), mt cytochrome oxidase I (COI), and the apicoplast caseinolytic protease C (ClpC) exhibit similar levels of sequence divergence, yet each gene tree presents a strikingly different pattern of …

Susceptibility of an area to invasion by exotic species is often judged by the fraction of introduced species in the local biota. However, the degree of invasion, particularly in mainland areas, has often been underestimated because of the exclusion of ‘domestic exotics’ (those introduced to internal units from within the national border) in calculations. Because all introduced species on islands are considered as exotics, this contributes to the perception that islands are more susceptible to invasion than are continental regions. Here, we determine the contribution of domestic exotic species to the degree of invasion (exotic fraction) in mainland areas. We …

Many laboratory models used in aging research are inappropriate for understanding senescence in mammals, including humans, because of fundamental differences in life history, maintenance in artificial environments, and selection for early aging and high reproductive rate. Comparative studies of senescence in birds and mammals reveal a broad range in rates of aging among a variety of taxa with similar physiology and patterns of development. These comparisons suggest that senescence is a shared property of all vertebrates with determinate growth, that the rate of senescence has been modified by evolution in response to the potential life span allowed by extrinsic mortality …