Tetranucleotide and dinucleotide microsatellite loci from the northern bobwhite (Colinus virginianus)

We describe polymerase chain reaction (PCR) primers and conditions to amplify eight dinucleotide, one trinucleotide and 14 tetranucleotide microsatellite DNA loci isolated from the northern bobwhite (Colinus virginianus). The PCR primers were tested on 16 individuals collected from a population located within the Red Hills region of south Georgia and north Florida. The 23 primer pairs developed in this study yielded an average of 6.5 alleles per locus (range 2–11), an average observed heterozygosity of 0.47 (range 0.06–0.94) and average polymorphic information content of 0.60 (range 0.06–0.85).     

Estimates of Survival from Radiotelemetry: a Response to Guthery and Lusk

Abstract: Radiotelemetry has become an important and frequently used tool in wildlife research. Inferences drawn from radiotelemetry data depend on the assumption that the radiotransmitters are not influencing parameter(s) of interest. An article by Guthery and Lusk (2004) in the Wildlife Society Bulletin questioned the validity of this assumption for estimating survival rates of northern bobwhites (Colinus virginianus) using radiotelemetry data. In this evaluation, we address technical and philosophical flaws in Guthery and Lusk's (2004) critique of northern bobwhite studies utilizing radiotelemetry. They concluded that biologists should be skeptical of radiotelemetry studies and they advised researchers to design studies to address potential biases caused by radiotransmitters using independent data. Although we agree that researchers are responsible for testing key assumptions of their techniques, we believe Guthery and Lusk's (2004) conclusions were not well supported and were based on tenuous assumptions. Guthery and Lusk (2004) calculated the level of productivity (given as a fall age ratio) required to balance a simple population model that contained published estimates of annual survival and assumed an annual finite population growth rate of 1.0. We review their population model and show that the relationship between an annual survival rate and fall age ratio is nonlinear. This nonlinearity can lead to biased estimates of a fall age ratio, especially at lower values of annual survival. We also question the validity of using fall age ratios as an estimator of productivity. Further, we suggest that this assessment of a radiotransmitter effect from a survival rate itself is not appropriate. This rate can be depressed (or elevated) for a variety of reasons not related to the influence of radiotransmitters. In addition, Guthery and Lusk (2004) assumed that daily survival rates (as calculated from both annual and seasonal published estimates) were constant throughout the year; thus, they scaled daily survival rates from seasonal to annual estimates. Further, their meta-analysis was hindered by temporal pseudoreplication and a lack of independence among the observations used in the analysis. We conclude the weight of the evidence presented by Guthery and Lusk (2004) is not as strong as they claim because it fails to meet the test of sufficient causation. While scientists should always be skeptical and critical of assumptions of all methods employed in wildlife research, more rigorous tests are necessary before we discredit a valuable technique without sufficient empirical evidence.     

Thermal physiology and the origin of terrestriality in vertebrates

The adaptive reasons for the evolutionary transition between obligatorily aquatic lobe-finned fish and facultatively terrestrial early tetrapods have long been debated. The oldest adequately known amphibians, Acanthostega and Ichthyostega , from the final stage in the Upper Devonian (Famennian), can be clearly distinguished from the most advanced choanate sarcopterygian fish from the next older stage (Frasnian) by the presence of large pectoral and pelvic girdles, limbs generally resembling those of later Palaeozoic land vertebrates, and the absence of bones linking the back of the skull with the shoulder girdle. Upper Devonian and most Lower Carboniferous amphibians, like their aquatic predecessors, differed significantly from modern amphibians in their much larger size, up to a metre or more in length. Animals of this size, resembling modern crocodiles and the marine iguana, could have raised their body temperatures by basking in the sun and sustained them upon re-entry into the water. It is hypothesized that the physiological advantages of thermoregulation were a major selective force that resulted in the increasing capacity for the ancestors of tetrapods to move into shallow water, and later to support their bodies against the force of gravity and increase the size and locomotor capacities of the limbs.  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 143 , 345–358.