Physical and Serologic Properties of an Antigen Prepared from Erythrocytes of Horses with Acute Babesiosis*

SYNOPSIS. By means of precipitation with protamine sulfate, a soluble antigen (PS) was obtained from erythrocytes of horses with acute babesiosis due to Babesia caballi and B. equi. This antigen reacted in gel diffusion tests with sera from horses recovered from acute babesiosis. The PS antigen was found to be muco-protein, susceptible to destruction by trypsin and taka-diastase. Analysis of the antigen by paper electrophoresis revealed 2 components which were not present in similar preparations made from erythrocytes of Babesia-free horses. When the PS antigen was heated in boiling water for 30 minutes, a serologically inactive precipitate was formed; however, the supernate remained serologically active and was termed boiled PS (BPS) antigen. This antigen was polysaccharide in nature; its serologic activity was destroyed by taka-diastase. In gel diffusion tests with sera of recovered horses, the PS antigen formed 2 lines of precipitation which coalesced in a single line formed between these sera and the BPS antigen. Both PS and BPS antigens reacted with sera of horses recovered from acute babesiosis in the gel-diffusion test, but not with sera of dogs and rats recovered from acute infection with Babesia canis and Babesia rodhaini, respectively. The serologic specificity of these antigens suggests that they might have application in the serodiagnosis of inapparent Babesia infections of equine animals.     

Growth patterns of a stream vertebrate differ between urban and forested catchments

1. Urban development results in the decline of amphibian density and species richness. A logical next step towards understanding why urbanisation negatively impacts amphibians is to track species‐specific demographic responses to urbanisation. 2. We monitored growth of two‐lined salamander (Eurycea cirrigera Green) larvae over two complete cohorts (2006 and 2007) in nine western Georgia, U.S.A. streams. 3. We found that salamanders in streams surrounded by urbanised and developing catchments hatched at the same size as their reference‐stream counterparts, but achieved larger sizes within the first few months of growth. We evaluated the effect of four variables that correlate with the urban‐forest gradient and found that elevated temperatures in the urban environment, coupled with decreased intraspecific competition because of lower survivorship in these same habitats, were two of the most likely explanations for increased growth rates. 4. Such an increase in growth of surviving larvae may maintain population viability in urban areas where it has been shown survival is difficult because of increased in‐channel flow during flood events. Because larvae that do survive in urban streams undergo metamorphosis at large sizes, they may recoup a component of fitness (i.e. increased adult survivorship and reproduction) through growth.     

Cougar Kill Rate and Prey Composition in a Multiprey System

Abstract: Assessing the impact of large carnivores on ungulate prey has been challenging in part because even basic components of predation are difficult to measure. For cougars (Puma concolor), limited field data are available concerning fundamental aspects of predation, such as kill rate, or the influence of season, cougar demography, or prey vulnerability on predation, leading to uncertainty over how best to predict or interpret cougar-ungulate dynamics. Global Positioning System (GPS) telemetry used to locate predation events in the field is an efficient way to monitor large numbers of cougars over long periods in all seasons. We applied GPS telemetry techniques combined with occasional snow-tracking to locate 1,509 predation events for 53 marked and an unknown number of unmarked cougars and amassed 9,543 days of continuous predation monitoring for a subset of 42 GPS-collared cougars in west-central Alberta, Canada. Cougars killed ungulates at rates near the upper end of the previously recorded range, and demography substantially influenced annual kill rate in terms of both number of ungulates (subad F [SAF] = 24, subad M [SAM] = 31, ad M = 35, ad F = 42, ad F with kittens <6 months = 47, ad F with kittens <6 months = 67) and kg of prey (SAF = 1,441, SAM = 2,051, ad M = 4,708, ad F = 2,423, ad F with kittens <6 months = 2,794, ad F with kittens >6 months = 4,280). Demography also influenced prey composition; adult females subsisted primarily on deer (Odocoileus spp.), whereas adult males killed more large ungulates (e.g., moose [Alces alces]), and subadults incorporated the highest proportion of nonungulate prey. Predation patterns varied by season and cougars killed ungulates 1.5 times more frequently in summer when juveniles dominated the diet. Higher kill rate in summer appeared to be driven primarily by greater vulnerability of juvenile prey and secondarily by reduced handling time for smaller prey. Moreover, in accordance with predictions of the reproductive vulnerability hypothesis, female ungulates made up a higher proportion of cougar diet in spring just prior to and during the birthing period, whereas the proportion of males increased dramatically in autumn during the rut, supporting the notion that prey vulnerability influences cougar predation. Our results have implications for the impact cougars have on ungulate populations and have application for using cougar harvest to manage ungulates.     

Rapid Homogenization of Multiple Sources: Genetic Structure of a Recolonizing Population of Fishers

Abstract: Fishers (Martes pennanti) were extirpated from much of southern Ontario, Canada, prior to the 1950s. We hypothesised that the recent recolonization of this area originated from an expansion of the population in Algonquin Provincial Park, which historically served as a refuge for fishers. To test this hypothesis, we created a sampling lattice to encompass Algonquin and the surrounding area, and we collected contemporaneous DNA samples. We sampled fishers from each of 35 sites and genotyped them at 16 microsatellite loci. Using a Bayesian assignment approach, with no a priori geographic information, we inferred 5 discrete genetic populations and used genetic population assignment as a means to cluster sites together. We concluded that the Algonquin Park fisher population has not been a substantial source for recolonization and expansion, which has instead occurred from a number of remnant populations within Ontario, Quebec, and most recently from the Adirondacks in New York, USA. The genetic structure among sampling sites across the entire area revealed a pattern of isolation-by-distance (IBD). However, an examination of the distribution of genetic structure (F_ST/1^- F_ST) at different distances showed higher rates of gene flow than predicted under a strict IBD model at small distances (40 km) within clusters and at larger distances up to 100 km among clusters. This pattern of genetic structure suggests increased migration and gene flow among expanding reproductive fronts.     

Climate‐driven increases in storm frequency simplify kelp forest food webs

Climate models predict a dramatic increase in the annual frequency and severity of extreme weather events during the next century. Here we show that increases in the annual frequency of severe storms lead to a decrease in the diversity and complexity of food webs of giant kelp forests, one of the most productive habitats on Earth. We demonstrate this by linking natural variation in storms with measured changes in kelp forest food web structure in the Santa Barbara Channel using structural equation modeling (SEM). We then match predictions from statistical models to results from a multiyear kelp removal experiment designed to simulate frequent large storms. Both SEM models and experiments agree: if large storms remain at their current annual frequency (roughly one major kelp‐removing storm every 3.5 years), periodic storms help maintain the complexity of kelp forest food webs. However, if large storms increase in annual frequency and begin to occur year after year, kelp forest food webs become less diverse and complex as species go locally extinct. The loss of complexity occurs primarily due to decreases in the diversity and complexity of higher trophic levels. Our findings demonstrate that shifts in climate‐driven disturbances that affect foundation species are likely to have impacts that cascade through entire ecosystems.     

Isolation and characterization of microsatellite markers in hoary marmots (Marmota caligata)

Microsatellite loci were developed from hoary marmots (Marmota caligata) to aid in the investigation of the social structure and mating system of this species. Seven of the microsatellite loci developed were found to be moderately polymorphic with between two and seven alleles per locus. In addition to the microsatellites developed in hoary marmots we also tested markers developed for other scuirids, namely European alpine marmots (M. marmota), Columbian ground squirrels (Spermophilus columbianus) and European ground squirrels (S. citellus). Of these markers, 13 were polymorphic when amplified in hoary marmots with between two and nine alleles per locus.     

Response of grazing snails to phosphorus enrichment of modern stromatolitic microbial communities

1. The effects of added phosphorus (P) on the growth, P and RNA : DNA contents, and survivorship of snails grazing on laminated microbial mats (living ‘stromatolites’) were examined in the Rio Mesquites at Cuatro Ciénegas, Mexico (total P, c. 0.60 μmol L^?1) to test the hypothesis that strong P‐limitation of microautotroph growth produces a stoichiometric constraint on herbivores because of mineral P‐limitation. 2. In a 3‐week experiment performed in summer 2001, addition of phosphorus (+15 μmol L^?1) resulted in a strong decline in stromatolite biomass C : P ratio from very high levels (c. 2300 : 1 by atoms) to moderate levels (c. 550 : 1). The endemic hydrobiid snail Mexithauma quadripaludium responded to P‐enrichment with elevated body P content and higher RNA : DNA ratios, especially for small animals likely to be actively growing. This positive response is consistent with the existence of a stoichiometric constraint on snail growth. 3. In a longer experiment (8 weeks) involving a more moderate P enrichment (+5 μmol L^?1) in summer 2002, P enrichment reduced stromatolite C : P ratio from moderate values in control treatments (c. 750) to very low values (<100 : 1). Snails responded to stromatolite P‐enrichment with increased body P content but, in contrast to the first experiment, with lower RNA : DNA ratio, lower growth rates, and higher mortality. 4. These contrasting results suggest that both very high and very low biomass C : P ratios in stromatolites are detrimental to M. quadripaludium performance, leading us to hypothesise that these herbivores live on a ‘stoichiometric knife edge’.     

Plant functional trait variation in relation to riparian geomorphology: The importance of disturbance

This study examined the patterns of plant functional trait variation in relation to geomorphology, disturbance and a suite of other environmental factors in the riparian margin of the Upper Hunter River, New South Wales, Australia. Vegetation was surveyed on three geomorphic surfaces (point bar, bench and bank) along a 5.5‐km stretch of the Upper Hunter River. Functional traits relating to plant growth and reproduction were collected for the identified species. anova and principal components analysis were used to compare the trait assemblages of species associated with each geomorphic unit. Pearson's correlation coefficients were used to investigate trait variation with respect to environmental variables. There were clear differences in the plant functional trait assemblages associated with the three geomorphic units. Generally the point bar was associated with species that were herbaceous, with small seed mass, a short stature and a high specific leaf area (SLA). Conversely, the bench was associated with grasses that had unassisted seed dispersal and intermediate seed mass and SLA, while species on the bank had tall stature, large seed mass, a high SLA and a perennial life cycle. Variation along the primary gradient of plant functional trait composition was most strongly related to disturbance frequency and to a lesser extent soil nutrients and the proportion of clay and silt, while variation along the secondary gradient was associated with variation in substrate texture as well as soil nutrients.