Biology undergraduates' misconceptions about genetic drift.

This study explores biology undergraduates' misconceptions about genetic drift. We use qualitative and quantitative methods to describe students' definitions, identify common misconceptions, and examine differences before and after instruction on genetic drift. We identify and describe five overarching categories that include 16 distinct misconceptions about genetic drift. The accuracy of students' conceptions ranges considerably, from responses indicating only superficial, if any, knowledge of any aspect of evolution to responses indicating knowledge of genetic drift but confusion about the nuances of genetic drift. After instruction, a significantly greater number of responses indicate some knowledge of genetic drift (p = 0.005), but 74.6% of responses still contain at least one misconception. We conclude by presenting a framework that organizes how students' conceptions of genetic drift change with instruction. We also articulate three hypotheses regarding undergraduates' conceptions of evolution in general and genetic drift in particular. We propose that: 1) students begin with undeveloped conceptions of evolution that do not recognize different mechanisms of change; 2) students develop more complex, but still inaccurate, conceptual frameworks that reflect experience with vocabulary but still lack deep understanding; and 3) some new misconceptions about genetic drift emerge as students comprehend more about evolution.

Genetic structure of the blue ridge dusky salamander (Desmognathus orestes): inferences from allozymes, mitochondrial dna, and behavior.

The plethodontid salamander Desmognathus orestes, a member of the D. ochrophaeus species complex, is distributed in southwestern Virginia, eastern Tennessee, and western North Carolina. Previous allozyme analyses indicate that D. orestes consists of two distinct groups of populations (D. orestes 'B' and D. orestes 'C') with extensive intergradation and probable gene flow between these two groups. Spatially varying allele frequencies can reflect historical associations, current gene flow, or a combination of population-level processes. To differentiate among these processes, we use multiple markers to further characterize divergence among populations of D. orestes and assess the degree of intergradation between D. orestes 'B' and D. orestes 'C', specifically investigating variation in allozymes, mitochondrial DNA (mtDNA), and reproductive behavior among populations. On a broad scale, the mtDNA genealogies reconstruct haplotype clades that correspond to the species identified from previous allozyme analyses. However, at a finer geographic scale, the distributions of the allozyme and mtDNA markers for D. orestes 'B' and D. orestes 'C' are discordant. MtDNA haplotypes corresponding to D. orestes 'B' are more broadly distributed across western North Carolina than predicted by allozyme data, and the region of intergradation with D. orestes 'C' indicates asymmetric gene flow of these markers. Asymmetric mating may contribute to observed discordance in nuclear versus cytoplasmic markers. Results support describing D. orestes as a single species and emphasize the importance of using multiple markers to examine fine-scale patterns and elucidate evolutionary processes affecting gene flow when making species-level taxonomic decisions.