Geographic variation in the diet of opaleye (Girella nigricans) with respect to temperature and habitat.

We studied diet variation in an omnivorous fish across its range, which allowed us to test predictions about the effect of ocean temperature and habitat on herbivory. Throughout most of its geographic range, from Southern California to central Baja California, the opaleye (Girella nigricans) fed primarily on red and green algae, but there was significant variation in the amount of algal material in the diet among sites. The proportion of algal material in the diet was related to habitat, with algae making up a larger proportion of a fish's diet in algal-dominated habitats than in urchin barrens. Independent of habitat, the proportion of algal material in the diet increased with environmental temperature. Analyses of stable isotopes revealed similar changes in trophic position and confirmed that these associations with diet persisted over relatively long time scales. The shift to a more herbivorous diet at warmer temperatures is in agreement with past laboratory studies on this species that show a diet-dependent change in performance with temperature and can indicate a diet shift across the species' geographic range to meet its physiological demands. A possible plastic response to herbivory was a longer gut relative to body size. The results of this study are consistent with past findings that associate temperature with increases in the relative diversity of herbivorous fishes in tropical parts of the ocean.

Salmonella isolates from wild-caught Tokay geckos (Gekko gecko) imported to the U.S. from Indonesia.

Reptiles account for ∼10% of live animal shipments imported to the United States (U.S.), the majority of which are sold in the pet trade. Characterizing Salmonella shedding by imported reptiles is of value to public health, the pet industry, and veterinary medicine. Here we report results of a pilot survey of Salmonella serotypes isolated from wild-caught Indonesian Tokay geckos (Gekko gecko) imported to the U.S. Upon arrival, the geckos were individually housed until a fecal sample was acquired for Salmonella culture. The geckos were divided into three groups with variable numbers to investigate density effects. A second group was imported after 3 months and combined with the previous groups. A total of 88 Salmonella isolates were obtained from 110 geckos surveyed, representing 14 serogroups and 17 unique serotypes. Group prevalence ranged from 31-73%. A significant increase in prevalence and a change in serotype richness were detected between the time of import and 6 months later at necropsy. Six isolates (6.8%) expressed resistance to more than one antibiotic. All S. enterica subsp. enterica Adelaide isolates were resistant to nalidixic acid and sulfisoxazole, one S. enterica subsp. arizonae 61:k:z35 isolate was resistant to ampicillin and sulfisoxazole, and another 61:k:z35 isolate was resistant to streptomycin and sulfisoxazole. Forty-three additional isolates expressed resistance only to sulfisoxazole. The mechanisms for increased prevalence and apparent change in serotype richness are unknown, but could be due to stress associated with trade, transport, and captivity, increased transmission from unnaturally high densities, or contact with other species shedding Salmonella along the trade route. Future studies to differentiate the physical, social, and physiological effects of trade-related conditions on Salmonella shedding and transmission among reptiles will benefit the industry by identifying ways to reduce mortality, and safeguard the individuals handling animals along the transport chain and other species encountered en route.

Local scale effects of disease on biodiversity.

To date, ecologists and conservation biologists have focused much of their attention on the population and ecosystem effects of disease at regional scales and the role that diseases play in global species extinction. Far less research has been dedicated to identifying the effects that diseases can have on local scale species assemblages. We examined the role of infectious disease in structuring local biodiversity. Our intention was to illustrate how variable outcomes can occur by focusing on three case studies: the influence of chestnut blight on forest communities dominated by chestnut trees, the influence of red-spot disease on urchin barrens and kelp forests, and the influence of sylvatic plague on grassland communities inhabited by prairie dogs. Our findings reveal that at local scales infectious disease seems to play an important, though unpredictable, role in structuring species diversity. Through our case studies, we have shown that diseases can cause drastic population declines or local extirpations in keystone species, ecosystem engineers, and otherwise abundant species. These changes in local diversity may be very important, particularly when considered alongside potentially corresponding changes in community structure and function, and we believe that future efforts to understand the importance of disease to species diversity should have an increased focus on these local scales.