Effects of Barriers and Thermal Refugia on Local Movement of the Threatened Leopard Darter, Percina pantherina

Local, short-term dispersal by the U.S. federally-threatened leopard darter, Percina pantherina, was examined in the field and in the laboratory to assess the possible effects of natural versus man-made barriers on movement. Mark-resight studies were conducted in two summers at sites in the Glover River (southeastern Oklahoma, U.S.A.). At one site, patches of 'preferred' habitat were separated by a natural riffle; at the other site, by a low-water road crossing with culverts. At the Natural Riffle site, darters moved downstream across the riffle, but also moved upstream into deeper water when water temperatures exceeded 29°C in the `preferred' habitat. Use of deeper, cooler waters by this species in late summer suggests that thermal refugia may be important habitats for the long-term management of leopard darters. At the Road Crossing site, all documented movement was in a downstream direction, and at least two darters traversed culverts in the low-water bridge. Laboratory studies of movement across several types of culverts suggested that culverts significantly decrease the probability of movement among habitat patches.     

A Plasmid Selection System in Lactococcus lactis and Its Use for Gene Expression in L. lactis and Human Kidney Fibroblasts

We report the development of a nonantibiotic and nonpathogenic host-plasmid selection system based on lactococcal genes and threonine complementation. We constructed an auxotrophic Lactococcus lactis MG1363Δthr strain which carries deletions in two genes encoding threonine biosynthetic enzymes. To achieve plasmid-borne complementation, we then constructed the minimal cloning vector, pJAG5, based on the genes encoding homoserine dehydrogenase-homoserine kinase (the hom-thrB operon) as a selective marker. Using strain MG1363Δthr, selection and maintenance of cells carrying pJAG5 were obtained in threonine-free defined media. Compared to the commonly used selection system based on erythromycin resistance, the designed complementation system offers a competitive and stable plasmid selection system for the production of heterologous proteins in L. lactis. The potential of pJAG5 to deliver genes for expression in eukaryotes was evaluated by insertion of a mammalian expression unit encoding a modified green fluorescent protein. The successful delivery and expression of genes in human kidney fibroblasts indicated the potential of the designed nonantibiotic host-plasmid system for use in genetic immunization.     

Increased frequency of scale anomalies and loss of genetic variation in serially bottlenecked populations of the dice snake, Natrix tessellata

Documented demographic bottlenecks resultingfrom introductions of the dice snake to severallakes in Switzerland provide a rare opportunityto study the effect of serial bottlenecks onthe genetic properties of Natrixtessellata populations. We investigated twointroduced populations using informationderived from eight microsatellite markers. Bothintroduced populations had significantlyreduced levels of allelic diversity relative tonon-bottlenecked populations. The severity ofthe bottlenecks was underlined by thesignificant reduction in observed and expectedheterozygosity. The loss of allelic diversityand observed heterozygosity was stronger in theserially bottlenecked population than in thepopulation that was bottlenecked only once.From previous studies, scale anomalies wereknown to be more common in introducedpopulations relative to native populations. Weinvestigated whether the higher occurrence ofscale anomalies in introduced populations isassociated with individual heterozygosity andmean genomic diversity d ². We founda significant relationship between theoccurrence of scale anomalies and individualheterozygosity but no significant relationshipbetween scale anomalies and the microsatellitespecific measurement, d ², was found.Because of their known history, introducedpopulations in Switzerland may serve as a modelto demonstrate the effect of severe populationbottlenecks on genetic variability anddevelopmental stability in N. tessellata.The results therefore help to device strategiesfor the management and protection of endangerednatural N. tessellata populations.     

A theoretical approach to predicting the success of genetic manipulation of malaria mosquitoes in malaria control

Background  

Mosquitoes that have been genetically modified to better encapsulate the malaria parasite Plasmodium falciparum are being considered as a possible tool in the control of malaria. Hopes for this have been raised with the identification of genes involved in the encapsulation response and with advances in the tools required to transform mosquitoes. However, we have only very little understanding of the conditions that would allow such genes to spread in natural populations.     

The Raynaud's Treatment Study: Biofeedback Protocols and Acquisition of Temperature Biofeedback Skills

The Raynaud's Treatment Study (RTS) compared temperature biofeedback training and a behavioral control procedure (frontalis EMG biofeedback) with nifedipine-XL and a medication placebo for treatment of primary Raynaud's phenomenon (RP) in a large (N = 313) multicenter trial. The present study describes the RTS biofeedback protocols and presents data on the acquisition of digital skin temperature and frontalis EMG responses in the RTS. The findings point to substantial problems with acquisition of physiological self-regulation skills in the RTS. Only 34.6% of the Temperature Biofeedback group (N = 81) and 55.4% of the EMG Biofeedback group (N = 74) successfully learned the desired physiological response. In contrast, 67.4% of a Normal Temperature Biofeedback group (N = 46) learned hand warming. Multivariate analysis found that coping strategies, anxiety, gender, and clinic site predicted acquisition of hand-warming skills whereas variables related to RP disease severity did not. Physiological data showed vasoconstriction in response to the onset of biofeedback and also found that performance in the initial sessions was critical for successful acquisition. These findings indicate that attention to the emotional and cognitive aspects of biofeedback training, and a degree of success in the initial biofeedback sessions, are important for acquisition.     

An integrative approach for studying the etiology of alcoholism and other addictions.

Studies of alcoholism etiology often focus on genetic or psychosocial approaches, but not both. Greater understanding of the etiology of alcohol, tobacco and other addictions will come from integration of these research traditions. A research approach is outlined to test three models for the etiology of addictions--behavioral undercontrol, pharmacologic vulnerability, negative affect regulation--addressing key questions including (i) mediators of genetic effects, (ii) genotype-environment correlation effects, (iii) genotype x environment interaction effects, (iv) the developmental unfolding of genetic and environmental effects, (v) subtyping including identification of distinct trajectories of substance involvement, (vi) identification of individual genes that contribute to risk, and (vii) the consequences of excessive use. By using coordinated research designs, including prospective assessment of adolescent twins and their siblings and parents; of adult substance dependent and control twins and their MZ and DZ cotwins, the spouses of these pairs, and their adolescent offspring; and of regular families; by selecting for gene-mapping approaches sibships screened for extreme concordance or discordance on quantitative indices of substance use; and by using experimental (drug challenge) as well as survey approaches, a number of key questions concerning addiction etiology can be addressed. We discuss complementary strengths and weaknesses of different sampling strategies, as well as methods to implement such an integrated approach illustrated for the study of alcoholism etiology. A coordinated program of twin and family studies will allow a comprehensive dissection of the interplay of genetic and environmental risk-factors in the etiology of alcoholism and other addictions.     

Holly leaf‐miners on two continents: what makes an outbreak species?

1. Some herbivore species periodically undergo damaging, high‐density outbreak phases followed by less damaging low‐density phases. Others maintain steady, low to moderate density levels that do little damage to their hosts. 2. Two closely related holly leaf‐miner species were compared that share many ecological traits and have very similar life cycles, but only one of which exhibits outbreaks. Phytomyza ilicicola in the eastern U.S.A. varied widely in mortality and infestation levels, reaching local densities of over 10 mines per leaf. In contrast, Phytomyza ilicis in the U.K. showed low infestation and high mortality at all sites. Using data from the literature and from field studies, the factors responsible for these contrasting dynamics were sought. 3. Phytomyza ilicicola oviposits into the leaf lamina, and experiences weak larval competition only at high densities. Phytomyza ilicis oviposits into the leaf midrib, which leads to high mortality of young larvae before mine formation. Multiply mined leaves were therefore very common in P. ilicicola but rare in P. ilicis. 4. Differences in the parasitoid complexes of the two systems accounted for further differences in survival to adulthood. The main (larval) parasitoid, which was found to impose high, density‐dependent mortality on P. ilicis, is missing on P. ilicicola. It is replaced by an egg–pupal parasitoid, which varies in its impact at differe～t sites. Multiple emergence of adults from multiply mined leaves is therefore widespread in P. ilicicola but does not occur in P. ilicis. 5. The differences in oviposition behaviour and in the parasitoid complexes are likely to allow P. ilicicola to outbreak when habitat conditions are favourable, while P. ilicis is always tightly regulated.     

The applicability of hns and fimA primers for detecting Salmonella in bioaerosols associated with animal and municipal wastes

The ability to rapidly screen environmental samples for specific pathogens such as Salmonella spp., is of particular importance in molecular epidemiology. Although gene amplification reactions allow the rapid detection of microorganisms, the use of appropriate oligonucleotide primers targeted against specific microbial genes is critical for accurate detection specificity and sensitivity. Primers such as fimA and hns have been previously shown to be specific for pure cultures of Salmonella. However, the analysis of environmental samples requires post-amplification hybridizations to detect amplicons, since the presence of inhibitory environmental components reduces amplification efficiency of the target organism. These sensitive post-amplification approaches also enable the detection of spurious amplification from non-target sequences. Bioaerosols associated with animal facilities and municipal wastes contain a diverse array of pathogens including Clostridium spp. In our studies, hybridization sensor data revealed spurious amplification of clostridial species with Salmonella hns primers. Specificity checks using type cultures of Clostridium spp. revealed non-specific amplification by hns primers. These results suggest that fimA primers may be better suited to screen Salmonella-specific sequences in environmental samples, especially those obtained from animal and municipal waste facilities.     

Comparative Phylogeography of Mississippi Embayment Fishes

The Mississippi Embayment is a prominent physiographic feature of eastern North America consisting of primarily lowland aquatic habitats and a fish fauna that is largely distinct from nearby highland regions. Numerous studies have demonstrated that both pre-Pleistocene and Pleistocene events have had a strong influence on the distributions and relationships of highland fishes in eastern North America. However, the extent to which these same events affected Embayment distributed taxa remains largely unexplored. The purpose of this study was to investigate the relative roles of pre-Pleistocene and Pleistocene events in shaping phylogeographic relationships of four stream dwelling fishes in the Mississippi Embayment. Molecular genetic analyses of the mitochondrial gene cytochrome b were performed for three ictalurid catfish species (Noturus miurus, n = 67; Noturus hildebrandi, n = 93, and Noturus phaeus, n = 44) and one minnow species (Cyprinella camura, n = 78), all distributed in tributary streams of the Mississippi Embayment. Phylogenetic relationships and divergence times among haplotypes for each species were estimated using maximum likelihood and Bayesian methods. Phylogenetic analyses recovered 6 major haplotype clades within N. miurus, 5 within N. hildbrandi, 8 within N. phaeus, and 8 within C. camura. All three Noturus species show a high degree of isolation by drainage, which is less evident in C. camura. A clade of haplotypes from tributaries in the southern portion of the Mississippi Embayment was consistently recovered in all four species. Divergence times among clades spanned the Pleistocene, Pliocene, and Miocene. Novel relationships presented here for C. camura and N. phaeus suggest the potential for cryptic species. Pre-Pleistocene and Pleistocene era sea level fluctuations coincide with some divergence events, but no single event explains any common divergence across all taxa. Like their highland relatives, a combination of both pre-Pleistocene and Pleistocene era events have driven divergences among Embayment lineages.