Phylogeny of the side-blotched lizards (Phrynosomatidae:Uta) based on mtDNA sequences: support for midpeninsular seaway in Baja California

We investigated the phylogenetic relationships of western North American Side-blotched lizards, genus Uta, using mitochondrial DNA partial gene sequences from cytochorme b and ATPase 6. Uta stejnegeri appeared basal in our tree followed by U. palmeri. Uta stansburiana from the islands of Angel de la Guarda, Mejia, and Raza formed the next clade, followed by U. antiqua and other populations of U. stansburiana. These relationships suggest that the populations on the Angel de la Guarda island block should be recognized as a distinct species. Remaining populations of U. stansburiana formed two clades, corresponding to the northern and southern Baja California peninsula. Uta stellata and U. squamata occurred within the northern and southern clades, respectively. The discontinuity requires a long-lasting isolation, the only reasonable explanation being a former midpeninsular seaway. Correlations between our cladogram and magnetic anomalies in the Gulf of California date formation of the seaway at 1 million years ago.

Flow cytometry in biodiversity surveys: methods, utility, and constraints

Abstract

Flow cytometry of blood is a powerful tool for rapidly sorting individual specimens on the basis of cellular DNA content. During biodiversity surveys, the method enabled the early identification of both cryptic sympatric and allopatric species of Vietnamese ranid frogs. This method may be extremely valuable in sorting individuals from other taxa and geographic regions, especially when cellular DNA content is known to vary among closely related taxa, and in tropical situations where crypsis is a relatively common phenomenon. Protocols for preparation of freezing solution, field procedures, preparation of reference standards, and flow cytometric analysis are provided. The best method for field preservation of blood is freezing in liquid nitrogen; field fixation of blood in ethanol was less efficient and resulted in drastically increased coefficients of variation. Once samples have been transferred to freezer storage, they should not be returned to a lower storage temperature in liquid nitrogen.

Recombinant human bone morphogenetic proteins-2 and -4 induce several mesenchymal phenotypes in culture

Bone morphogenetic protein has previously been shown to induce the formation of cartilage and bone in vivo. We have isolated a population of mesenchymal stem cells from rat skeletal muscle capable of forming multiple mesodermal morphologies in vitro. These cells were treated with recombinant human bone morphogenetic proteins-2 and -4 to determine the differentiation-inducing activities of bone morphogenetic protein on these cells. The mesenchymal stem cells were cultured in medium with 10% preselected horse serum containing 0 to 100 ng/ml recombinant human bone morphogenetic proteins-2 or -4 for a maximum of 4 weeks. Control cultures maintained the stellate morphology of mesenchymal stem cells. Cultures treated with recombinant human bone morphogenetic protein-2 exhibited discrete cartilage nodules and mineralized bone nodules. The first increase in chondrogenesis was seen at 0.5 ng/ml. Cultures treated with recombinant human bone morphogenetic protein-4 also exhibited an increase in chondrogenesis at the higher concentration of 2 ng/ml. Skeletal myotubes and adipocytes also appeared in cultures treated with either bone morphogenetic protein. Mesenchymal stem cells do respond to inductive factors, but bone morphogenetic proteins-2 and -4 were not specific for the induction of cartilage and bone.

Allozyme variation in populations of Lacerta raddei and Lacerta nairensis (Sauria: Lacertidae) from Armenia

Abstract

Lacertca raddei and Lacerta nairensis have been recognized as two separate species based on morphology and behavior, and each has been implicated as a sexual parent of different parthenogenetic forms. However, recent mitochondrial DNA work failed to distinguish these two as separate species. We examined genetic diversity at 36 allozyme loci from six populations of L. nairensis and four populations of L. raddei. There were no fixed allelic differences between the two. Mean heterozygosity was slightly higher among populations of L. raddei than among populations of L. nairensis. A Distance Wagner phenogram showed that the northernmost population of L. raddei clustered with the L. nairensis populations; the other L. raddei populations clustered together. We suggest that L. raddei and L. nairensis may not be separate species, a finding which has important implications for determining the origins of some parthenogenetic Lacerta.

mtDNA gene sequence, allozyme, and morphological uniformity among red diamond rattlesnakes,Crotalus ruberandCrotalus exsul

Genetic and morphological diversity were investigated in two species of red diamond rattlesnakes. Crotalus exsul Garman, 1884 occurs on Isla de Cedros, and Crotalus ruber Cope, 1892 is found on the peninsula of Baja California, in southern California, and on many islands in the Gulf of California. A partial sequence consisting of 297 nucleotide base pairs from cytochrome b of the mitochondrial DNA genome revealed a single difference only, a level of variation common between rattlesnake subspecies. A phylogenetic analysis showed C. exsul to possess the derived state. The products of 29 gene loci were resolved using horizontal starch gel electrophoresis. No fixed differences were observed to occur, although gene frequencies at one locus, catalase-A, were significantly different (P < 0.00004). Among the 16 morphological characters gathered, none served to unequivocally identify the two taxa. The results of a principal components analysis, using eight morphological characters, revealed that the characters of the Isla de Cedros specimens represented a small subset found in the peninsular Baja California specimens. A multivariate discriminate function analysis could correctly identify 94% of C. ruber and 83% of C. exsul. Because of the close similarity among these two taxa, we believe the red diamond rattlesnakes are best considered a single species, C. exsul, and the peninsular population retained as C. e. ruber; one Gulf of California population is recognized as C. e. lorenzoensis.

Allozyme variation in three closely related species of Caucasian rock lizards (Lacerta)

Abstract

Genetic diversity at 37 allozyme loci was surveyed from Lacerta valentini (4 populations), L. portschinskii and L. rudis (1 population each). The number of polymorphic loci ranged from 1 (L. valentini) to 11 (L. rudis). Mean heterozygosity (direct count) ranged from 0.003 (L. valentini) to 0.071 (L. rudis). Nei's (1978) genetic distance ranged from 0-0.03 among populations of L. valentini, 0.127-0.163 between L. valentini and L. rudis and 0.366-0.487 between L. portschinskii and the two other taxa. Indices of genetic variability for species having disjunct distributions were lower than in species with contiguous distributions, similar to the case of insular populations, which have lower values than do mainland populations.

GA, Murphy RW. Allozyme differentiation among gopher tortoises (Gopherus): conservation genetics and phylogenetic and taxonomic implications

The genetic diversity among 18 loci within and among four species of gopher tortoises was investigated using horizontal starch gel electrophoresis. Within species variation ranged from 2 to 4% by direct count and from 2 to 8% by Hardy–Weinberg expectation. Of the loci resolved, 11–22% expressed variation. The northern and southern populations of Gopherus flavomarginatus could not be distinguished. No fixed differences were observed between G. agassizii and G. berlandieri, as reflected in a Nei genetic distance of 0.008. These latter species may be little more than allopatric populations of G. agassizii. Differentiation between the two remaining species was not extensive; G. polyphemus was only slightly distinct from G. flavomarginatus, being separated by a Nei genetic distance of only 0.006. The two pairs of species were separated by an average genetic distance of 0.200. The evolutionary rates of divergence were observed to be unequal, especially between G. polyphemus and G. flavomarginatus. The overall genetic similarity suggests a relatively recent age of origin.

A comparison of controlled negative pressure and aerosol quantitative respirator fit test systems by using human subjects

A quantitative respirator fit test system based on controlled negative pressure was evaluated by comparison testing with a computerized aerosol fit test system. Experiments ranged from multiple sequential tests of a single subject wearing a respirator equipped with a series of fixed leaks to sequential fit tests of 125 U.S. Air Force personnel using both systems. Throughout each test phase, measured negative pressure fit factors were consistently more conservative and less variable than aerosol fit factors. Comparison of subject and fixed leak fit factors indicated significant loss of aerosol during subject fit tests. Negative pressure system results did not show any effect from subject-related losses.

Isozyme evidence for independently derived, duplicate G3PDH loci among squamate reptiles

We report evidence for several independent gene duplications for the locus encoding the enzyme glycerol-3-phosphate dehydrogenase (G3PDH) in squamate reptiles. Evidence for the duplication comes from population genetic studies demonstrating "fixed" heterozygosity in all members of some lizard species, the documentation of independent allelic heterozygosity at each of the two G3PDH loci in these same species, and tissue-specific gene expression surveys in a taxonomically diverse array of groups. The duplicated condition is present at both low and high taxonomic levels (selected populations of the phrynosomatid lizard Sceloporus grammicus, and almost all snakes, respectively), and appears to represent the derived condition in most of these groups. One notable exception is the colubrid snake genus Masticophis, which appears to be characterized by an apomorphic secondary silencing event. Evolutionary implications of the duplication and silencing events within squamates are discussed, and we suggest that the overall phylogenetic utility of this marker is low in this radiation as a result of extensive homoplasy.

A comparison of controlled negative pressure and aerosol quantitative respirator fit test systems by using fixed leaks

An automated version of a new method for quantitative respirator fit testing by controlled negative pressure was compared with a computerized aerosol fit test system. The controlled negative pressure technique eliminates many of the problems associated with aerosol and pressure decay fit test methods. A series of fixed leaks was used to compare the leak measurement capabilities of the controlled negative pressure system against a standard computerized aerosol fit test system. Negative pressure and aerosol fit factors determined for a series of fixed leaks through hypodermic needles were highly correlated with each other (r = 0.998) and with the cross-sectional areas of the leak needles (r greater than 0.995).

The problematic phylogenetic analysis of interlocus heteropolymer isozyme characters: a case study from sea snakes and cobras

Multiple cases of parallel advancement (isozyme silencing) of L-lactate dehydrogenase heterotetramer isozymes are encountered when the observed isozyme patterns are superimposed on a well-corroborated cladogram depicting the phylogenetic relationships of some sea snakes, cobras, and coral snakes. This finding may be common among similar data sets because of parallel evolution and the inability to discern transformation sequences. Thus, the utility of this isozyme character in phylogenetic investigations may be severely limited, depending on the taxonomic group or level of universality being investigated.

Form and function of the tooth crown structure in gekkonid lizards (Reptilia, Squamata, Gekkonidae)

The shapes of gekkonid teeth are examined in detail using scanning electron microscopy. The teeth are found to have lingually tilted cusps similar to those reported in caecilians and extinct dissorophoid amphibians. In most species, teeth possess two cusps separated by a concave sulcus, but in (at least) one species, teeth have four well-developed cusps. Because the cusps are weakly developed or absent in large or noninsectivorous geckos, we suggest that the observed arrangement of cusps aids smaller species in grasping hard-bodied prey. The cusps of most gekkonid teeth possess well-developed median tips which are more pronounced than those of amphibians with bicuspid teeth. The shapes of these teeth may be of value in phylogenetic investigations.