HABITAT-RELATED DIFFERENCES IN NECROPH- ILOUS SPECIES COMPOSITION: IMPLICATIONS FOR RESOURCE COMPETITION

Competition for resources is one of the most important selective factors influencing the expression of life history traits in both plants and animals (Darwin 1859). In grasslands, competition for resources such as nutrients, water, and space often is constrained by stochastic processes (Axelrod 1985). Disturbance factors such as fire, grazing by large herbivores, and fluctuating climatic conditions tend to alter the structure and magnitude of competition for limited resources among grassland communities more frequently than in other ecosystems (Snaydon 1987, van der Maarel 1993). Vertebrate carrion is one important resource used by both plants and animals in grasslands, providing a rich but ephemeral point source of nutrients (Towne 2000, Barton et al. 2013). A complex ecological network of vertebrate and invertebrate necrophilous animal species compete intensely for these carrion resources, often aided by specialized sensory and motility adaptations that aid resource discovery and sequestration (Putman 1978, Scott et al. 1979, DeVault et al. 2003)

Yellow-crowned Night Herons Sighted in North Dakota

Yellow-crowned night herons (Nyctanassa violacea) sighted at four locations in North Dakota during 1976 appear to be the first observations of this species for the State. We sighted a single individual about 8 km south of Medina, North Dakota in western Stutsman County during several visits in June and July 1976. The bird was first seen on 23 June standing in a pasture adjoining an 8.5 ha semi-permanent marsh. On following visits, the heron usually was seen perched in trees at the edge of the wetland. A single yellow-crowned night heron was sighted on the same wetland on three separate occasions in June 1977. It is not known whether this was the same individual that was seen in 1976. The wetland contains dense stands of cattail (Typha spp.), hardstem bulrush (Scirpus acutus), and reed (Phragmites communis), and is bordered by open stands of cottonwood (Populus deltoides) and peach-leaved willow (Salix amygdaloides). Several black-crowned night herons (Nycticorax nycticorax) also were observed at the marsh during 1976 and 1977. Herons may have been attracted to the wetland by the presence of large numbers of leopard frogs (Rana pipiens). No yellow-crowned night heron nests were found during nest searches of the wetland in 1976 and 1977

Yellow-crowned Night Herons Sighted in North Dakota

Yellow-crowned night herons (Nyctanassa violacea) sighted at four locations in North Dakota during 1976 appear to be the first observations of this species for the State. We sighted a single individual about 8 km south of Medina, North Dakota in western Stutsman County during several visits in June and July 1976. The bird was first seen on 23 June standing in a pasture adjoining an 8.5 ha semi-permanent marsh. On following visits, the heron usually was seen perched in trees at the edge of the wetland. A single yellow-crowned night heron was sighted on the same wetland on three separate occasions in June 1977. It is not known whether this was the same individual that was seen in 1976. The wetland contains dense stands of cattail (Typha spp.), hardstem bulrush (Scirpus acutus), and reed (Phragmites communis), and is bordered by open stands of cottonwood (Populus deltoides) and peach-leaved willow (Salix amygdaloides). Several black-crowned night herons (Nycticorax nycticorax) also were observed at the marsh during 1976 and 1977. Herons may have been attracted to the wetland by the presence of large numbers of leopard frogs (Rana pipiens). No yellow-crowned night heron nests were found during nest searches of the wetland in 1976 and 1977

Life history and demographic determinants of effective/census size ratios as exemplified by brown trout (Salmo trutta)

A number of demographic factors, many of which related to human-driven encroachments, are predicted to decrease the effective population size (Ne) relative to the census population size (N), but these have been little investigated. Yet, it is necessary to know which factors most strongly impact Ne, and how to mitigate these effects through sound management actions. In this study, we use parentage analysis of a stream-living brown trout (Salmo trutta) population to quantify the effect of between-individual variance in reproductive success on the effective number of breeders (Nb) relative to the census number of breeders (Ni). Comprehensive estimates of the Nb/N ratio were reduced to 0.16–0.28, almost entirely due to larger than binomial variance in family size. We used computer simulations, based on empirical estimates of age-specific survival and fecundity rates, to assess the effect of repeat spawning (iteroparity) on Ne and found that the variance in lifetime reproductive success was substantially higher for repeat spawners. Random family-specific survival, on the other hand, acts to buffer these effects. We discuss the implications of these findings for the management of small populations, where maintaining high and stable levels of Ne is crucial to extenuate inbreeding and protect genetic variability.publishedVersio

mtDNA Variation in Caste Populations of Andhra Pradesh, India.

Various anthropological analyses have documented extensive regional variation among populations on the subcontinent of India using morphological, protein, blood group, and nuclear DNA polymorphisms. These patterns are the product of complex population structure (genetic drift, gene flow) and a population history noted for numerous branching events. As a result, the interpretation of relationships among caste populations of South India and between Indians and continental populations remains controversial. The Hindu caste system is a general model of genetic differentiation among endogamous populations stratified by social forces (e.g., religion and occupation). The mitochondrial DNA (mtDNA) molecule has unique properties that facilitate the exploration of population structure. We analyzed 36 Hindu men born in Andhra Pradesh who were unrelated matrilineally through at least 3 generations and who represent 4 caste populations: Brahmin (9), Yadava (10), Kapu (7), and Relli (10). Individuals from Africa (36), Asia (36), and Europe (36) were sampled for comparison. A 200-base-pair segment of hypervariable segment 2 (HVS2) of the mtDNA control region was sequenced in all individuals. In the Indian castes 25 distinct haplotypes are identified. Aside from the Cambridge reference sequence, only two haplotypes are shared between caste populations. Middle castes form a highly supported cluster in a neighbor-joining network. Mean nucleotide diversity within each caste is 0.015, 0.012, 0.011, and 0.012 for the Brahmin, Yadava, Kapu, and Relli, respectively. mtDNA variation is highly structured between castes (GST = 0.17; p < 0.002). The effects of social structure on mtDNA variation are much greater than those on variation measured by traditional markers. Explanations for this discordance inelude (1) the higher resolving power of mtDNA, (2) sex-dependent gene flow, (3) differences in male and female effective population sizes, and (4) elements of the kinship structure. Thirty distinct haplotypes are found in Africans, 17 in Asians, and 13 in Europeans. Mean nucleotide diversity is 0.019, 0.014, 0.009, and 0.007 for Africans, Indians, Asians, and Europeans, respectively. These populations are highly structured geographically (GST = 0.15;p < 0.001). The caste populations of Andhra Pradesh cluster more often with Africans than with Asians or Europeans. This is suggestive of admixture with African populations.We would like to thank T. Jenkins, H. Soodyall, P. Nute, and J. Kidd for providing DNA samples and S. Austin, A. Comuzzie, R. Duggirala, R. Feldman, K. Lum, A. Rogers, and S. Watkins for technical advice, critical comments, and thoughtful discussion. This work was supported in part by the National Science Foundation through grant NSF-DBS-9211255, the Clinical Research Center at the University of Utah through grant NIH RR-00064, and the Technology Access Center of the Utah Human Genome Project

Effect of Intraduodenal Bile and Na-Taurodeoxycholate on Exocrine Pancreatic Secretion and on Plasma Levels of Secretin, Pancreatic Polypeptide, and Gastrin in Man

The effect of intraduodenally administered cattle bile (CB) and Na-taurodeoxycholate (TDC) on basal pancreatic secretion and plasma levels of secretin, pancreatic polypeptide (PP), and gastrin were investigated on two separate days in 10 fasting volunteers. Doses of 2-6 g CB and 20&600 mg TDC were given intraduodenally at 65-min intervals. Volume, bicarbonate, lipase, trypsin, amylase, and bilirubin were measured in 10-min fractions of duodenal juice, and GI peptides determined by radioimmunoassay. CB and TDC enhanced significantly and dose-dependently volume, bicarbonate and enzyme secretion, and plasma secretin and PP levels. In contrast, plasma gastrin showed only a marginal increase. We conclude that the hydrokinetic effect of intraduodenal CB and TDC is at least partially mediated by secretin. Gastrin could be ruled out as a mediator of the ecbolic effect, whereas other GI peptides, primarily CCK, and/or neural mechanisms must be considered possible mediators. Both pathways may also play a role in the PP release