1,721,050 research outputs found
Molecular Systematics of the Texas Genera of Nyctaginaceae
No full textFor a family well known for its confusing morphological taxonomy, surprisingly little molecular phylogenetic work has been published for the Nyctaginaceae (four o’clock family). This plant group is important in Texas because it includes the endangered endemic Abronia macrocarpa. Elucidating phylogenetic relationships, especially sister group relationships, offers insight into areas like speciation and character evolution. With endangered taxa, this insight may help guide management strategies. Approximately twelve genera (ca. 68 species) of Nyctaginaceae occur in Texas. A molecular phylogenetic investigation was undertaken to determine the relationships among eleven of these genera. DNA sequences of the ITS nrDNA were used to reconstruct relationships via maximum parsimony, distance, and maximum likelihood methods. Phylogenetic relationships within Tribe Nyctagineae do not agree with any of the current classifications. Other relationships within the family, as well as recommendations for needed taxonomic changes, are discussed.Biolog
Isolation and Sequencing of the cDNA Encoding a-actinin 3 in Rat Skeletal Muscle
No full textAlpha-actinins are a family of proteins that have been characterized as crosslinkers of filamentous actin in eukaryotes. Their structure is marked by an actin-binding region followed by four spectrin-like repeats which in turn is followed by two EF-hand regions that may or may not bind calcium depending on the isoform. Alpha-actinin 3 (AA3) is a calcium insensitive isoform that is found only in skeletal muscle. Isolation of the cDNA that potentially encodes this protein in rat skeletal muscle was carried out using the Uni-ZAP XR cDNA library and immunoscreenmg with an anti-sarcomenc-cxactimn antibody. A phagemid containing this cDNA was transfected into E. coli and isolated. Primers designed against the multiple cloning site allowed for partial sequencing of the 5' and 3' ends of the insert. Partial sequences facilitated the designing of new pnmers to eventually bridge the two ends of the cDNA, and to determine a contiguous sequence of the insert using Sequencher software. The cDNA sequence shows strong identity to the AA3s found in mouse and human. The inferred protein sequence also showed 99.32% identity to AA3 in mouse and 96.00% to that of human. Each of the regions contained within the protein individually show strong identity with A A3 in mouse and human implying similar function and structure.Biolog
Diversity and Conservation Genetics of the Mexican Beaded Lizard (Heloderma horridum)
No full textThe Mexican beaded lizard (Heloderma horridum), one of only two venomous lizards in the world, is distributed throughout central and western Mexico. There are four currently recognized subspecies including: H. h. horridum, H. h. charlesbogerti, H. h. alvarezi, and H. h. exasperatum and all are now considered threatened. Due to the lack of verifiable locality data and ambiguities in diagnostic characters, it is often difficult to determine subspecific identity among captive individuals. Because uncertainties exist, genetic analyses of mitochondrial DNA (mtDNA) and nuclear microsatellites were used to define the patterns of genetic variation and population structure for the captive populations of H. horridum in order to make a genetically effective management program. Both categories of markers revealed a high level of genetic differentiation indicating significant population structure. All phylogenetic results converge toward a similar evolutionary hypothesis, with five mtDNA groups present among two major clades. Clustering obtained from microsatellites is not congruent with the mtDNA phylogenies, but is consistent with the unification of the subspecies H. h. charlesbogerti and H. h. alvarezi. The most conservative management plan would be to preserve six populations of H. horridum until the taxonomy can be revised.Biolog
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Molecular Identification, Phylogeny and Systematics of Haemogregarina in Turtles
No full textNo abstract prepared.Biolog
Estimates and Effects of Vertebrate Predation on Drift Fence Associated Pitfall Traps
No full textDrift fence sampling with associated pitfall traps is a technique used to assess small vertebrate communities among a variety of taxa. Researchers using this trapping technique have analyzed a number of factors from drift fence design to associated problems. One potential problem often overlooked is the effect foraging vertebrate predators might have on animals captured in pitfall traps. Removal of animals from pitfalls by vertebrate predators might lead researchers to inaccurate conclusions regarding the composition of small vertebrate animal communities and their populations. Motion-sensitive cameras and track monitoring stations were used to estimate the amount and variety of vertebrate predators attending a series of 18 pitfall arrays monitoring the endangered Houston toad (Bufo houstonensis) on the Griffith League Ranch in Bastrop County, Texas. Ten potential vertebrate predators were documented visiting pitfall arrays with the northern raccoon (Procyon lotor) being the most frequently recorded visitor for both the motion-sensitive cameras (41.8% of total photographs) and track monitoring stations (64.5% of total tracks recorded). Proportions of pitfalls with tracks and animals present were compared to the proportion of pitfall traps without tracks and animals using a 95% confidence interval of two proportions and nominal logistic regression analyses. No statistical difference was detected in number of animals captured in pitfalls visited by predators verse number of animals captured in pitfalls without predator activity (95% Cl = -0.026 < Pr P2 < 0.035; r2= 0.0012, p = 0.2712). Although the presence of predators did not seem to affect the overall capture success of pitfall traps, the frequency of predator visits to pitfalls indicated risks still existed for confined animals. This risk increases when dealing with rare or endangered taxa, which could potentially be exposed to higher levels of predation when confined to pitfall traps. The generally low capture success of 18 pitfall arrays during my study and the difficulty in addressing direct predation might have limited my ability to detect the true effects of predators on drift fence sampling. Future studies should focus on different monitoring techniques such as infrared video camera systems and other ways to estimate the loss of individual animals from pitfall traps. Additionally, precautionary measures should be encouraged for researchers using pitfall sampling to survey rare or endangered taxa.Biolog
Effects of a pleistocene barrier on herpetofaunal distributions in southwestern North America
No full textLake Cabeza de Vaca existed in the northern portion of the Chihuahuan Desert during the Pleistocene, possibly limiting taxon ranges and driving diversification of taxa by sundering once continuous populations occurring across this region. I reevaluate phylogenetic studies in light of evidence of Cabeza de Vaca and present molecular data that addresses the biological influence of the lake. Supplementing our reevaluations of previous studies, we identified taxa likely to show genetic differentiation consequent of the lake and tested them. Specimens from the colubrid snake Rhinocheilus lecontei and the phrynosomatid lizard taxa Phrynosoma cornutum and Urosaurus ornatus were collected, followed by DNA sequencing of a mitochondrial gene region that included Nicotinamide Adenine Dinucleotide subunit 4 (ND4), and the tRNAs Serine, Histidine, and Leucine. Phylogenetic analyses using maximum likelihood and Bayesian methods were used to construct evolutionary relationships between individuals of each taxo based on the obtained nucleotide sequences. In order to determine if correlations existed between sequence data variation and geography, haplotype networks were constructed and nested clade analysis was performed on P. cornutum using a combined data set that included other available sequence of the ND4 gene region. Deep molecular divergences were found within each taxon from specimens collected across the northern Chihuahuan Desert. Application of a molecular clock using three calibration rates suggests that the divergences predate the age of the lake. Orogeny of the southern extension of the Rocky Mountains in the Miocene and Pliocene likely produced the molecular signatures recovered in each taxon. These findings corroborate a more widely known hypothesis invoked to account for the split of the Sonoran and Chihuahuan Desert faunas.Biolog
Consequences of Variation in Dietary Protein on Captive-raised Black Knob Map Turtles (Graptemys nigrinoda, emydidae)
No full textMany turtle species are threatened with extinction worldwide. Because of their slow maturation rates, low juvenile survivorship and slow population recovery status, more aggressive conservation tools including captive propagation may be required to prevent extinctions. Captive propagation is the practice of hatching eggs in an environment with fewer natural predators, better living conditions, and consequently decreased mortality. Often adults are kept to create a "farmed population" and the juveniles are released into the natural habitat. However for any conservation tool to be effective, the released juveniles must have a realistic chance of survival and reproductive success in the natural environment. This study was designed to gather information about the potential consequences ( e.g. growth and mortality) of variable protein diets on captive-hatched juvenile Graptemys nigrinoda (Black Knob Map Turtle). The experiment had two distinct parts: a 9-month exposure to one of three dietary proteins, followed by a 9-month exposure to the medium-level dietary protein. Over the variable portion of the experiment, all three diets had significantly different growth curves. After the 9-month medium protein level diet, all turtles, regardless of previous protein level, achieved the same end point. Importantly for propagation efforts, juvenile mortality does appear to be related to protein level; the highest dietary protein level sustained the fewest number of mortalities while the lowest protein had the lowest survivorship.Biolog
Population Genetic Structure of a Cave-Dwelling Bat, Myotis velifer
No full textMyotis velifer is known to exhibit a wide-range of geographically correlated morphological and behavioral variation, reflecting genetically unexplored ecological subdivisions. Unlike migratory chiropterans, genetic structure is generally found among chiropterans exhibiting non-migratory behavior. Interestingly, both migratory and nonmigratory behavior is noted among M. velifer. Previous morphometric analyses proposed existing barriers to gene flow among taxonomic subdivisions. Also, abandonment of historical roosts has been used to designate M. velifer as a species of concern throughout Texas. Genetic methods were used to evaluate whether population genetic structure is congruent with behavioral or taxonomic subdivisions and, assuming a decline is associated with roost abandonment, whether a population decline in Texas is the result of a history of demographic contraction. To explore these proposals and concerns, tissue samples were collected from roosts in the Texas Panhandle (3), central and west Texas (13) and the California-Arizona border (4), representing both behavioral designations and three taxonomic subdivisions. Mitochondrial sequence data (982 base pairs of Cytochrome b) from 104 individuals recovered 54 haplotypes and three haplogroups. Thirty-four microsatellite loci evaluated for cross-species amplification yielded four suitably polymorphic autosomal loci and one X-linked locus. Mitochondrial structure is not congruent with behavior, taxonomy, or geography and microsatellite data (n = 192) recovered no genetic structure. Mitochondrial data indicate weak regional fidelity, nuclear data indicate substantial gene flow, and demographic analyses indicate historic demographic expansion among M. velifer. The current subspecies of M. velifer are not genetically supported; however, incorporation of (or “accounting for”) morphological and behavioral data leads me to conclude that M. v. magnamolaris should be maintained for non-migratory populations. California specimens should be assigned to M. v. incautus designating M. v. velifer to only occur south of the United States border with Mexico. Analysis of Mexican and Central American specimens is needed to determine support for this nominator subspecies. Management of the two proposed United States subspecies should be across areas containing multiple roosts until conclusive evidence suggests causes of roost abandonment.Biolog
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