Mark L. McKnight

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We present phylogenetic analyses of both molecular and morphological data for the 23 major lineages of living turtles and seven key fossil taxa. Nearly 1 kilobase of cytochrome b sequence, 325 base pairs of 12S ribosomal DNA, and 115 morphological characters contained similar phylogenetic information, although each provided unique information on different(More)
We present a phylogenetic analysis of the Ambystoma tigrinum complex, based on approximately 840 base pairs of mitochondrial-DNA sequence from the rapidly evolving D-loop and an adjacent intron. Our samples include populations of the continentally distributed species, A. tigrinum, plus all described species of Mexican ambystomatids. Sequence divergence is(More)
We report the presence, in the mitochondrial DNA (mtDNA) of all of the sexual species of the salamander family Ambystomatidae, of a shared 240-bp intergenic spacer between tRNAThr and tRNAPro. We place the intergenic spacer in context by presenting the sequence of 1,746 bp of mtDNA from Ambystoma tigrinum tigrinum, describe the nucleotide composition of the(More)
Substantiated cases of ring species in mammals are rare. I examined the variation in mitochondrial DNA (mtDNA) of Perognathus amplus and P. longimembris in and around Arizona to test the hypothesis proposed by Hoffmeister (1986) that these two taxa are members of a single ring species demonstrating circular overlap. Through digestion of purified mtDNA from(More)
 Horse (Equus caballus) immunoglobulin mu chain-encoding (IgM) variable, joining, and constant gene segments were cloned and characterized. Nucleotide sequence analyses of 15 cDNA clones from a mesenteric lymph node library identified 7 unique variable gene segments, 5 separate joining segments, and a single constant region. Based on comparison with human(More)
Eighty-five consecutively seen HIV-positive persons with oral candidiasis were evaluated for clinical characteristics, staging of HIV disease, quantitation of candidal colony formation, and response to systemic antifungal treatment with Nizoral (ketoconazole). Fifty-five had CD4 counts less than 200. There was an inconsistent association between clinical(More)
Using polymerase chain reaction, interleukin-6 (IL-6) cDNA fragments from harbor seal (Phoca vitulina), killer whale (Orcinus orca), and Southern sea otter (Enhydra lutris nereis) were cloned and sequenced. For all three species, a continuous open reading frame encoding 203 residues for harbor seal, 199 residues for killer whale, and 201 residues fro sea(More)
We investigate kin-structured migration and its effects on patterns of genetic variation in cytoplasmic and nuclear genomes. We show that colonization events involving close relatives, such as those that might characterize range expansion and the invasion of new habitats, can change the patterns of nuclear and cytoplasmic genetic variation expected at(More)
Until recently, two surface-dwelling species of multi-ribbed brook salamanders (i.e., the metamorphic Eurycea multiplicata griseogaster [Graybelly Salamander], and the strictly paedomorphic E. tynerensis [Oklahoma Salamander]) were recognized as living in the Missouri Ozarks. The current understanding is that a single species (Oklahoma Salamander) is(More)