Development of cytochrome b primers for mitotyping of barbels (Barbus spp.).

Primers were developed that allow for rapid, reliable and inexpensive screening of cytochrome b by analysis of single-stranded conformational polymorphisms. Twenty different haplotypes were identified from six species of Iberian Barbus. These primers proved useful for population and species level studies, and could also be valuable in population genetic and phylogenetic studies of other cyprinin fishes.

Body mass and temperature influence rates of mitochondrial DNA evolution in North American cyprinid fish.

The mass-specific metabolic rate hypothesis of Gillooly and others predicts that DNA mutation and substitution rates are a function of body mass and temperature. We tested this hypothesis with sequence divergences estimated from mtDNA cytochrome b sequences of 54 taxa of cyprinid fish. Branch lengths estimated from a likelihood tree were compared with metabolic rates calculated from body mass and environmental temperatures experienced by those taxa. The problem of unknown age estimates of lineage splitting was avoided by comparing estimated amounts of metabolic activity along phyletic lines leading to pairs of modern taxa from their most recent common ancestor with sequence divergences along those same pairs of phyletic lines. There were significantly more pairs for which the phyletic line with greater genetic change also had the higher metabolic activity, when compared to the prediction of a hypothesis that body mass and temperature are not related to substitution rate.

Genetic monitoring of wild and repatriated populations of endangered razorback sucker (Xyrauchen texanus, Catostomidae, Teleostei) in Lake Mohave, Arizona-Nevada.

The Native Fishes Work Group, formed in 1991, developed and implemented a protocol to enhance the dwindling razorback sucker population in Lake Mohave, Arizona-Nevada. This large, genetically diverse population is severely reduced in size as a result of recruitment failure associated with predation on larvae. To circumvent this problem, wild larvae are captured, reared in protective custody until they are large enough to escape predation, and then released back into the lake. We present results of a monitoring program designed to assess the effectiveness of the sampling design in transmitting the high genetic diversity found in wild adults. Variation in a fragment from the mitochondrial DNA gene cytochrome b was examined by analysis of single-stranded polymorphisms and direct sequencing. Samples were characterized from three life history stages. Characterization of wild adults verified previous results that identified considerable diversity and provided baseline data. Samples of larvae from several temporal collections from throughout the spawning season and four geographical areas were characterized for 7 years (1997-2003) to assess the transmission of genetic variation from wild adults to larvae. Several analyses identified significant differences among temporal collections, resulting from sampling errors associated with finite number of females spawning at a given time and place. Comparisons among areas and years failed to identify significant variation, indicating that pooled collections for each year possess the same levels and patterns of genetic variation. Examination of repatriates representing 11 years (1992-2002) also failed to identify significant differences among cohorts; however, some sample sizes were small and the amova may lack sufficient power to detect differences. Contrasts of wild adults, larvae, and repatriates identified statistically significant differences among collections within these three groups; however, levels of variation are small and not biologically meaningful. More importantly, this analysis failed to detect significant differences among adults, larvae, and repatriates indicating that the program has been achieving its goal of transmitting variation from adults through the larvae and into the repatriate population. The reproductive capability of repatriates has not been examined, so it is unknown if the program will maintain genetic variation found in the original adult population. This will be most easily achieved by periodic monitoring of genetic variation in larval samples. If levels of variation become reduced in repatriates, levels and patterns of diversity in larvae are also expected to become reduced, and deviations in estimates of genetic diversity may become larger and more frequent. If this is the case, intervention may be necessary to ensure that certain individuals are not over-represented in the repatriate population.

Does nonneutral evolution shape observed patterns of DNA variation in animal mitochondrial genomes?

Early studies of animal mitochondrial DNA (mtDNA) assumed that nucleotide sequence variation was neutral. Recent analyses of sequences from a variety of taxa have brought the validity of this assumption into question. Here we review analytical methods used to test for neutrality and evidence for nonneutral evolution of animal mtDNA. Evaluations of mitochondrial haplotypes in different nuclear backgrounds identified differences in performance, typically favoring coevolved mitochondrial and nuclear genomes. Experimental manipulations also indicated that certain haplotypes have an advantage over others; however, biotic and historical effects and cyto-nuclear interactions make it difficult to assess the relative importance of nonneutral factors. Statistical analyses of sequences have been used to argue for nonneutrality of mtDNA; however, rejection of neutral patterns in the published literature is common but not predominant. Patterns of replacement and synonymous substitutions within and between species identified a trend toward an excess of replacement mutations within species. This pattern has been viewed as support for the existence of mildly deleterious mutations within species; however, other alternative explanations that can produce similar patterns cannot be eliminated.

The role of introgressive hybridization in the evolution of the Gila robusta complex (Teleostei: Cyprinidae).

The extent and impact of introgressive hybridization was examined in the Gila robusta complex of cyprinid fishes using mitochondrial DNA (mtDNA) sequence variation. Lower Colorado River basin populations of G. robusta, G. elegans, and G. cypha exhibited distinct mtDNAs, with only limited introgression of G. elegans into G. cypha. The impact of hybridization was significant in upper Colorado River basin populations; most upper basin fishes sampled exhibited only G. cypha mtDNA haplotypes, with some individuals exhibiting mtDNA from G. elegans. The complete absence of G. robusta mtDNA, even in populations of morphologically pure G. robusta, indicates extensive introgression that predates human influence. Analysis of the geographic distribution of variation identified two distinctive G. elegans lineages; however, the small number of individuals and localities sampled precluded a comprehensive analysis. Analysis of haplotype and population networks for G. cypha mtDNAs from 15 localities revealed low divergence among haplotypes; however, significant frequency differences among populations within and among drainages were found, largely attributable to samples in the Little Colorado River region. This structure was not associated with G. cypha and G. robusta, as morphotypes from the same location are more similar than conspecific forms in other locations. This indicates that morphological and mtDNA variation are affected by different evolutionary forces in Colorado River Gila and illustrates how both hybridization and local adaptation can play important roles in evolution.

Nonlinear simulations of Jupiter's 5-micron hot spots.

Large-scale nonlinear simulations of Jupiter's 5-micron hot spots produce long-lived coherent structures that cause subsidence in local regions, explaining the low cloudiness and the dryness measured by the Galileo probe inside a hot spot. Like observed hot spots, the simulated coherent structures are equatorially confined, have periodic spacing, propagate west relative to the flow, are generally confined to one hemisphere, and have an anticyclonic gyre on their equatorward side. The southern edge of the simulated hot spots develops vertical shear of up to 70 meters per second in the eastward wind, which can explain the results of the Galileo probe Doppler wind experiment.

Establishing a captive broodstock for the endangered bonytail chub (Gila elegans).

It is crucial for endangered species to retain as much genetic variation as possible to enhance recovery. Bonytail chub (Gila elegans) is one the most imperiled freshwater fish species, persisting as a declining population of large and old individuals primarily in Lake Mohave on the lower Colorado River. Establishment of a new captive broodstock from the 1981 F1 progeny of at most 10 wild fish plus any newly captured wild fish is evaluated and reviewed. The effective number of founders contributing to the 1981 F1 progeny appears quite small, varying from approximately 3.5, based on F1 allozyme data and supported by mtDNA data, to approximately 8.5, based on the original production records. Using a sample of these progeny to initiate a new broodstock further reduces the effective number of founders. With even the most optimistic evaluation of the amount of genetic variation in F1 progeny, it is obvious that including wild fish in the broodstock is essential to increase the amount of genetic variation. The approach given here could be applied to retain genetic variation in other endangered species in a captive broodstock until they have stable natural populations of adequate size.

Evolutionary dynamics of tandem repeats in the mitochondrial DNA control region of the minnow Cyprinella spiloptera.

Length variation due to tandem repeats is now recognized as a common feature of animal mitochondrial DNA; however, the evolutionary dynamics of repeated sequences are not well understood. Using phylogenetic analysis, predictions of three models of repeat evolution were tested for arrays of 260-bp repeats in the cyprinid fish Cyprinella spiloptera. Variation at different nucleotide positions in individual repeats supported different models of repeat evolution. One set of characters included several nucleotide variants found in all copies from a limited number of individuals, while the other set included an 8-bp deletion found in a limited number of copies in all individuals. The deletion and an associated nucleotide change appear to be the result of a deterministic, rather than stochastic, mutation process. Parallel origins of repeat arrays in different mitochondrial lineages, possibly coupled with a homogenization mechanism, best explain the distribution of nucleotide variation.

MATERNAL ANCESTRY OF THE RUTILUS ALBURNOIDES COMPLEX (TELEOSTEI, CYPRINIDAE) AS DETERMINED BY ANALYSIS OF CYTOCHROME b SEQUENCES.

Cytochrome b (cyt b) sequences from specimens of the Rutilus alburnoides unisexual complex and five bisexual species were compared to examine hypotheses regarding the origin and maternal ancestry of this complex. Phylogenetic analysis revealed a monophyletic relationship among unisexuals and Leuciscus pyrenaicus, clearly identifying this species as the maternal ancestor. Considerable mtDNA diversity exists among R. alburnoides populations, with many localities exhibiting unique haplotypes. The topology recovered from analysis of cyt b variation among populations suggested that R. alburnoides is polyphyletically derived from their sympatric L. pyrenaicus populations, indicating that unisexual lineages have been generated through multiple hybridization events. Although much less abundant, R. alburnoides is present outside the range of L. pyrenaicus, suggesting that it may have dispersed from the Tejo drainage into the northern basins. In this region, Leuciscus carolitertii is most likely the sexual host for the unisexual complex.

HST imaging of atmospheric phenomena created by the impact of comet Shoemaker-Levy 9.

Hubble Space Telescope (HST) images reveal major atmospheric changes created by the collision of comet Shoemaker-Levy 9 with Jupiter. Plumes rose to 3000 kilometers with ejection velocities on the order of 10 kilometers second-1; some plumes were visible in the shadow of Jupiter before rising into sunlight. During some impacts, the incoming bolide may have been detected. Impact times were on average about 8 minutes later than predicted. Atmospheric waves were seen with a wave front speed of 454 +/- 20 meters second-1. The HST images reveal impact site evolution and record the overall change in Jupiter's appearance as a result of the bombardment.

Length variation in mitochondrial DNA of the minnow Cyprinella spiloptera.

Length differences in animal mitochondrial DNA (mtDNA) are common, frequently due to variation in copy number of direct tandem duplications. While such duplications appear to form without great difficulty in some taxonomic groups, they appear to be relatively short-lived, as typical duplication products are geographically restricted within species and infrequently shared among species. To better understand such length variation, we have studied a tandem and direct duplication of approximately 260 bp in the control region of the cyprinid fish, Cyprinella spiloptera. Restriction site analysis of 38 individuals was used to characterize population structure and the distribution of variation in repeat copy number. This revealed two length variants, including individuals with two or three copies of the repeat, and little geographic structure among populations. No standard length (single copy) genomes were found and heteroplasmy, a common feature of length variation in other taxa, was absent. Nucleotide sequence of tandem duplications and flanking regions localized duplication junctions in the phenylalanine tRNA and near the origin of replication. The locations of these junctions and the stability of folded repeat copies support the hypothesized importance of secondary structures in models of duplication formation.

Origin of Gila seminuda (Teleostei: Cyprinidae) through introgressive hybridization: implications for evolution and conservation.

Morphological and genetic characters from cyprinid fishes of the genus Gila were examined to assess a hypothesized hybrid origin of Gila seminuda from the Virgin River, Arizona-Nevada-Utah. The presumed parents, Gila robusta robusta and Gila elegans, are clearly differentiated from one another based on morphology, allozymes, and mtDNA haplotypes. G. seminuda is morphologically intermediate and polymorphic at allozyme loci diagnostic for the parental species. Restriction endonuclease analysis of mtDNA showed G. seminuda nearly identical to G. elegans. These results support an origin of the bisexual taxon G. seminuda through introgressive hybridization. The Gila population in the Moapa River, Nevada, also appears to be of hybrid origin and is considered a distinctive population of G. seminuda. Inter-specific hybridization is potentially an important mode of evolution among western North American fishes, and valid species of hybrid origin may exist in other groups as well. Consideration of this mode of evolution argues for the need to conserve entire species complexes.

Voyager 2 in the uranian system: imaging science results.

Voyager 2 images of the southern hemisphere of Uranus indicate that submicrometersize haze particles and particles of a methane condensation cloud produce faint patterns in the atmosphere. The alignment of the cloud bands is similar to that of bands on Jupiter and Saturn, but the zonal winds are nearly opposite. At mid-latitudes (-70 degrees to -27 degrees ), where winds were measured, the atmosphere rotates faster than the magnetic field; however, the rotation rate of the atmosphere decreases toward the equator, so that the two probably corotate at about -20 degrees . Voyager images confirm the extremely low albedo of the ring particles. High phase angle images reveal on the order of 10(2) new ringlike features of very low optical depth and relatively high dust abundance interspersed within the main rings, as well as a broad, diffuse, low optical depth ring just inside the main rings system. Nine of the newly discovered small satellites (40 to 165 kilometers in diameter) orbit between the rings and Miranda; the tenth is within the ring system. Two of these small objects may gravitationally confine the e ring. Oberon and Umbriel have heavily cratered surfaces resembling the ancient cratered highlands of Earth's moon, although Umbriel is almost completely covered with uniform dark material, which perhaps indicates some ongoing process. Titania and Ariel show crater populations different from those on Oberon and Umbriel; these were probably generated by collisions with debris confined to their orbits. Titania and Ariel also show many extensional fault systems; Ariel shows strong evidence for the presence of extrusive material. About halfof Miranda's surface is relatively bland, old, cratered terrain. The remainder comprises three large regions of younger terrain, each rectangular to ovoid in plan, that display complex sets of parallel and intersecting scarps and ridges as well as numerous outcrops of bright and dark materials, perhaps suggesting some exotic composition.

Heat activation of the Fe protein of nitrogenase from Rhodospirillum rubrum.

The Fe protein of nitrogenase from Rhodospirillum rubrum isolated in the inactive form was found to be activated in vitro by heating. This heat activation was dependent upon temperature, pH, and enzyme concentration. During activation by heating, a change in the subunit composition of Fe protein was observed on sodium dodecyl sulfate gels. The upper subunit decreases and the lower subunit increased. All components of the modifying group on inactive Fe protein appear to be lost upon heat activation.

Comparison of active and inactive forms of iron protein from Rhodospirillum rubrum.

The Fe protein of nitrogenase from Rhodospirillum rubrum was purified in its active and inactive forms. It is shown that the inactive form exists as a two-subunit modified form of the enzyme as previously reported [Ludden & Burris (1978) Biochem. J. 175, 251--259]. In contrast, the active form exists as a single-subunit unmodified form of the enzyme. The upper subunit (on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis) of the inactive form was shown to contain at least the phosphate group of the covalently bound modifying group. The active and inactive forms of the enzyme were shown to be identical proteins on the basis of amino-acid composition, tryptic-digest pattern and immunological cross-reactivity.