Methane-flux-dependent lateral faunal changes in a Late Cretaceous chemosymbiotic assemblage from the Nakagawa area of Hokkaido, Japan

A Late Cretaceous carbonate body (2 m in maximum diameter) surrounded by clastic rocks, recently discovered in the Nakagawa area (Hokkaido, Japan), is interpreted as a methane‐seep deposit, on the basis of negative carbon isotopic composition (as low as ?43.5‰), variable sulphide sulphur isotopic composition, high carbonate content, and in situ fractures. It most likely formed owing to methane‐bearing pore‐water diffusion. We estimate that the concentration of methane decreased toward the margin of the carbonate body, and that only small carbonate concretions were precipitated at a certain distance from the methane‐seep centre. These spatial characteristics coincide well with the observed pattern of faunal distribution. The gastropod‐dominated association (indeterminate abyssochrysids and ataphrids and the acmaeid limpet Serradonta sp. are most common) co‐occurs with lucinid and thyasirid bivalves (Thyasira sp., Myrtea sp., and Miltha sp.), and was found within and just above the methane‐derived carbonate body. Acharax and Nucinella (solemyoid bivalves) are more typical of the peripheral part of the methane‐influenced sediments. We suggest that this pattern of faunal distribution reflects the decreasing concentration of methane and apparently also hydrogen sulphide when moving from the centre of discharge toward the periphery of the methane seep.     

Direct and indirect effects of plant genetic variation on enemy impact

Abstract.

• 1 The Tritrophic and Enemy Impact concepts predict that natural enemy impact varies: (a) among plant genotypes and (b) may depend on the abundance of heterospecific herbivores, respectively. I tested these predictions using three herbivore species on potted, cloned genotypes of Salik sericea Marshall in a common garden experiment.
• 2 Densities of the leaf miner (Phyllonorycter salicifoliella (Chambers)) and two leaf galling sawflies (Phyllocolpa nigrita (Marlatt) and Phyllocolpa eleanorae Smith and Fritz) varied significantly among willow clones, indicating genetic variation in resistance.
• 3 Survival and natural enemy impact caused by egg and larval parasitoids and/or unknown predators differed significantly among willow clones for each of the three herbivore species, indicating genetic variation in survival and enemy impact.
• 4 Survival of Phyllonorycter was negatively density-dependent among clones.
• 5 Survival of Phyllonorycter and Phyllocolpa eleanorae were positively correlated with densities of heterospecific herbivores among clones and parasitism of these species were negatively correlated with densities of the same heterospecific herbivores among clones.
• 6 At least for Phyllonorycter this positive correlation may suggest either facilitation of survival between herbivore species, which do not share natural enemies, or an apparent interaction caused by host plant genetic variation.
• 7 Among clones, egg parasitism of Phyllocolpa eleanorae was weakly positively correlated with density of Phyllocolpa nigrita. Since these species share the same Trichogramma egg parasitoid, this interaction could support the hypothesis of apparent competition.

     

Development and characterization of microsatellite markers for the endangered northern riffleshell mussel Epioblasma torulosa rangiana (Bivalvia: Unionidae)

Primers for six polymorphic microsatellite loci were developed for the endangered northern riffleshell Epioblasma torulosa rangiana from the Sydenham River, Ontario, Canada. These loci along with an additional nine microsatellite loci, developed from other unionoid species, available in the literature, were tested and characterized on individuals from two populations in the Allegheny River; one population in French Creek, PA, USA, and one population from the Sydenham River. Allelic diversity ranged from two to 28 alleles per locus and averaged 13.7 per locus. These primers are being used in a rangewide study on the conservation genetics of remaining extant populations of the northern riffleshell.     

Contrasting Effects of Wolves and Human Hunters on Elk Behavioral Responses to Predation Risk

ABSTRACT Prey behavioral responses to predation risk in wolf-ungulate-plant systems are of interest to wildlife managers. Using Global Positioning System data collected from telemetry-collared elk (Cervus elaphus) and wolves (Canis lupus), we evaluated elk behavioral responses to spatial and temporal variation in wolf- and human-predation risk on a winter range in the Greater Yellowstone Area, USA. We found elk changed grouping patterns and increased movement rates as predation risk increased and that these behavioral changes were habitat dependent. Elk behavioral responses to wolf- and human-predation risk were similar; however, responses to human-predation risk were stronger than responses to wolf-predation risk. These results suggest that predation risk from wolves or human hunters may result in elk spending more time on private rangelands away from public-land winter ranges, which may exacerbate problems of landowner tolerance of elk on livestock pastures. However, increased movement and changing grouping patterns on winter ranges may also disperse elk grazing impacts and lessen elk impacts on any one area.     

Body Size Variations in Caribou Ecotypes and Relationships With Demography

ABSTRACT In many vertebrates size is one of the most influential and variable individual characteristics and a strong determinant of reproductive success. Body size is generally density dependent and decreases when intraspecific competition increases. Frequent and long-distance movements increase energy expenditures and, therefore, may also influence body size, particularly in highly mobile species. Caribou (Rangifer tarandus, also known as reindeer) exhibit tremendous variation in size and movements and thus represent an excellent candidate species to test the relationships between body size, population size, and movements. We analyzed body measurements of adult female caribou from 7 herds of the Québec-Labrador Peninsula, Canada, and we related their morphology to population size, movements, and annual ranges. The herds represented 3 ecotypes (migratory, montane, and sedentary). Ecotypes and herds differed in size (length), shape (roundness), and movements. The sedentary ecotype was larger and moved 4 to 7 times less than the migratory ecotype in the 1990s. At the start of a demographic growth period in the early 1960s, migratory caribou from the Rivière-George (hereafter George) herd had longer mandibles than caribou of the sedentary ecotype. Mandible length in the George herd declined in the 1980s after rapid population growth, while individuals performed extensive movements and the herd's annual range increased. Migratory caribou then became shorter than sedentary caribou. After the George herd decline in the 1990s, mandible length increased again near levels of the 1980s. Caribou from the migratory Rivière-aux-Feuilles herd later showed a similar decline in mandible length during a period of population growth, associated with longer movements and increasing annual range. We hypothesize that the density-dependent effect observed on body size might have been exerted through summer habitat degradation and movement variations during herd growth. Our study has 2 important implications for caribou management: the distinctiveness of different populations and ecotypes, and the correlations between population trajectories and changes in body condition and habitat.     

Disease and the abundance and distribution of bird populations: a summary

Over the past few years, I have written several reviews about the effects of infectious diseases upon the distribution and abundance of their host populations. One general review and synthesis is in the fmd chapter of a book whose earlier chapters focus mainly on human diseases (Anderson & May 1991). A bird-specific discussion, with particular reference to conservation issues, is given by Dobson and May (1991). Broadly related questions about the invasion, persistence and spread of infectious diseases within animal communities are explored by Anderson and May (1986) and with emphasis on bird populations by Dobson and May (1986). Also relevant are a set of papers from the Society for Conservation Biology's first-ever symposium on Conservation and Disease (for an overview, see May 1988, Scott 1988).
Rather than burdening the literature with a recapitulation of these existing reviews, this paper gives a sign-posted guide for those who are not familiar with this particular literature. I first sketch reasons for believing that infectious diseases play an important part in the life history of birds. Next I point towards an analytic framework for understanding the dynamics of host-pathogen associations. Finally I list some of the implications for the conservation biology of bird populations.