Showing papers by "Museum of Texas Tech University published in 2005"

SYSTEMATICS OF THE GENUS SIGMODON: DNA SEQUENCES FROM BETA-FIBRINOGEN AND CYTOCHROME b

Abstract: Nucleotide sequences from intron 7 of the beta-fibrinogen gene (Fgb-I7) were used to evaluate phylogenetic relationships among members of the genus Sigmodon. In addition, these sequences were combined with mitochondrial cytochrome-b sequences and analyzed from a total evidence perspective. Results from parsimony and Bayesian analyses indicated support for 3 species groups (alstoni, fulviventer, and hispidus). A sister relationship was depicted for S. alleni and S. hirsutus, followed by the addition of S. toltecus; however, little resolution was provided for relationships between other members of the hispidus species group.

Sexing Bison Metapodials Using Principal Component Analysis

Abstract: Bison remains are a common and important component of many North American archaeological and paleontological sites. Interpretations of bison remains, however, often are hampered by the inability to determine sex reliably in this dimorphic taxon. Metapodials are among the most common bison element recovered in archaeological assemblages, but have proven difficult to sex. The methods currently in use to estimate sex range from those using only bivariate plots and ratios of various metapodial measurements to those using discriminant function analysis. Each method has advantages and disadvantages, with no one method producing certain, unambiguous results. The designation of sex in borderline specimens remains uncertain in all current methods and must be determined subjectively. By reducing data through the use of ratios, the current bivariate methods fail to make full use of the size variation present between male and female bison. The requirements of discriminant function analysis likewise limit this method’s utility for sexing metapodials, particularly for assemblages containing small sample sizes. The use of principal component analysis utilizing several of the most dimorphic, commonly measured variables produces a more confident assessment of sex for both complete and partial specimens of modern bison metapodials.

Genetic diversity within the southern plains woodrat (neotoma micropus) in southern texas.

Abstract: Genetic diversity within a population of the southern plains woodrat was examined using DNA sequences (967 base pairs [bp]) obtained from the control or d-loop region of the mitochondrial genome. One hundred fourteen individuals from 10 collection sites were assigned to 42 haplotypes. Haplotype diversity values were moderate to high (0.974 overall and ranged from 0.524 to 0.964 across collecting sites), whereas nucleotide diversity values were low (0.008 overall and ranged from 0.001 to 0.010 across sites), indicating that this population possesses a high number of closely related haplotypes. Seventy-nine percent of the genetic variability was partitioned within groups that corresponded to the collecting sites. In addition, 13 samples from Texas, New Mexico, and Mexico were included as references for evaluating the evolutionary history of haplotypes. Nested clade analysis revealed that restricted gene flow with isolation by distance in conjunction with contiguous range expansion was responsible for the observed pattern of genetic diversity. A test of neutrality supported the diagnosis of restricted gene flow, but failed to support contiguous range expansion due solely to population growth. Examination of the spatial distribution of the haplotypes indicated that most haplotypes were restricted to a single collecting site; however, a small number of haplotypes were found at 2 or more sites. A phylogenetic analysis indicated that some haplotypes (28.6%) were restricted to the study area whereas the remaining haplotypes occupied a broader geographic region.

Mygalomorph spiders from southwestern Oregon, USA, with descriptions of four new species

Abstract: Extensive pitfall trapping in the Siskiyou and southern Cascade Mountains in southwestern Oregon, USA, revealed the presence of four new species of Antrodiaetus spiders (Antrodiaetidae) as well as numerous examples of the rarely reported Hexura rothi (Mecicobothriidae). The new species are: Antrodiaetus ashlandensis, A. coylei, A. effeminatus, and A. metapacificus. Additional records were also obtained for Antrodiaetus pugnax and Atypoides gertschi (Antrodiaetidae). Distributional data are provided for each species. The four new species are described and illustrated and a taxonomic key to all mygalomorph spiders from southwestern Oregon is provided. Further, each of the previously described Antrodiaetus spp. from the region is diagnosed. The morphology of the male genital plate is proposed as a potentially useful taxonomic character.