Winter and summer weather modulate the demography of wild turkeys at the northern edge of the species distribution

Temperate species occupying habitats at the northern limit of their geographical distribution are limited by weather and climatic conditions. Such conditions often directly affect population dynamics, and thus, influence shifts in distribution via changes in demographic parameters. We examined this question by following three distinct populations of wild turkeys inhabiting areas exposed to a gradient of meteorological conditions at the northern limit of the species distribution. Four years of radio-telemetry on 181 birds and monitoring of 95 nests revealed that population demographics of wild turkeys were influenced by snow depth, winter temperature and summer rainfall. During winter, survival of turkeys decreased drastically when snow depth remained >30 cm for >10 days and also decreased as temperatures got colder. In the spring, snow persistence delayed nest initiation, whereas nest survival was negatively affected by rainfall. Our findings show that the effects of critical meteorological factors such as snow and temperature can be compounded when both reach the limit of a species tolerance simultaneously.     

Gene Order Breakpoint Evidence in Animal Mitochondrial Phylogeny

Multiple genome rearrangement methodology facilitates the inference of animal phylogeny from gene orders on the mitochondrial genome. The breakpoint distance is preferable to other, highly correlated but computationally more difficult, genomic distances when applied to these data. A number of theories of metazoan evolution are compared to phylogenies reconstructed by ancestral genome optimization, using a minimal total breakpoints criterion. The notion of unambiguously reconstructed segments is introduced as a way of extracting the invariant aspects of multiple solutions for a given ancestral genome; this enables a detailed reconstruction of the evolution of non-tRNA mitochondrial gene order. Received: 15 July 1998 / Accepted: 5 March 1999