When to worry about the weather: role of tidal cycle in determining patterns of risk in intertidal ecosystems

Species range boundaries are determined by a variety of factors of which climate is one of the most influential. As a result, climate change is expected to have a profound effect on organisms and ecosystems. However, the impacts of weather and climate are frequently modified by multiple nonclimatic factors. Therefore, the role of these nonclimatic factors needs to be examined in order to understand and predict future change. Marine intertidal ecosystems are exposed to heat extremes during warm, sunny, midday low tides. Thus, the timing of low tide, a nonclimatic factor, determines the potential contact intertidal invertebrates and algae have with heat extremes. We developed a method that quantifies the daily risk of high temperature extremes in the marine intertidal using solar elevations and spatially continuous tidal predictions. The frequency of 'risky days' is variable over time and space along the Pacific Coast of North America. Results show that at some sites the percentage of risky days in June can vary by 30% across years. In order to do a detailed analysis, we selected San Francisco as a study site. In San Francisco, May is the month with the greatest frequency of risky days, even though September is the month with the greatest frequency of high air temperature, ≥30 °C. These results indicate that marine intertidal organisms can be protected from high temperature extremes due to the timing of tides and local weather patterns. In addition, annual fluctuations in tides influence the frequency of intertidal zone exposures to high temperature extremes. Peaks in risk for heat extremes in the intertidal zone occur every 18 years, the length of the tidal epoch. These results suggest that nonclimatic variables can complicate predictions of shifts in species ranges due to climate change, but that mechanistic approaches can be used to produce predictions that include these factors.     

Validation of Fecal Glucocorticoid Metabolite Assays for South African Herbivores

ABSTRACT Fecal glucocorticoid metabolite (FGM) assays are a popular means of monitoring adrenocortical activity (i.e., physiological stress response) in wildlife. Species-specific differences in glucocorticoid metabolism and excretion require assay validation, including both laboratory and biological components, before assay use in new species. We validated a commercially available radioimmunoassay (MP ¹²⁵I corticosterone RIA kit [MP Biomedicals, Solon, OH]) for measuring FGMs of several South African herbivores, including giraffe (Giraffa camelopardalis), impala (Aepyceros melampus), nyala (Tragelaphus buxtoni), kudu (Tragelaphus strepsiceros), wildebeest (Connochaetes taurinus), and zebra (Equus burchelli). These herbivores are important in South African parks and reserves for ecotourism and as a prey base for predators and serve an integral role in ecosystem processes. Standard biochemical validations (e.g., recovery of exogenous corticosterone, intra- and interassay variation, and parallelism) demonstrated that the assay accurately and precisely measured FGMs of all 6 herbivore species. Our biological validations demonstrated that the assay was sensitive enough to detect changes in FGM production associated with season. Samples collected during the dry season (Jun-Aug) contained higher FGM concentrations than those from the wet season (Dec-Feb) in all species. We established optimal sample dilutions and reference FGM levels for these 6 herbivores, which can now be used to monitor the effects of management and ecotourism activities on the stress responses of these herbivores.     

Epidermal club cells do not protect fathead minnows against trematode cercariae: a test of the anti‐parasite hypothesis

Epidermal club cells of fishes in the superorder ostariophysi have puzzled evolutionary biologists because they were historically linked to chemical alarm signalling and relied on group selectionist explanations. Alternative hypotheses to explain the existence of these cells include the possibility of an anti‐pathogenic or anti‐parasitic function. If this is so, individual fish should invest in increased numbers of club cells after exposure to parasites, and club cells should contain components that reduce the infectivity of skin‐penetrating larvae. Infectivity of cercariae of the trematode Ornithodiplostomum sp. was significantly reduced when exposed to the skin extract of fathead minnows (an ostariophysan), but also to skin extract of mollies (a non‐ostariophysan that lacks club cells), respectively, compared to controls. Moreover, club cell density was not affected by exposure to cercariae. Taken together, these results are inconsistent with an anti‐parasite function for these cells and instead suggest a generic role in response to injury. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 884–890.     

Effects of pH and predation by Chaoborus larvae on the plankton of a shallow and acidic forest lake

1. Eutrophic acid lakes are not common. Delamere Lake in Cheshire, U.K. is shallow and acid (mean pH 4.5) with a very high phytoplankton crop (mean 290 μg chlorophyll a L^?1), dominated by Dictyosphaerium pulchellum. Rotifers were dominant in the pelagic waters but small cladocerans (Alona guttata, Chydorus sphaericus and Scapholeberis mucronata) were occasional in the littoral waters. Chaoborus flavicans larvae were the top predators in this fishless lake. Two mesocosm experiments were carried out in which pH and Chaoborus populations were manipulated. 2. Progressively higher concentrations of D. pulchellum were maintained in the elevated pH treatments (pH 6 and 8; P < 0.001) with increased amounts of a Chlamydomonas species at the end of the experiment. Highest species richness was seen at ambient pH. Thus the low pH of Delamere Lake alone did not control the structure of the phytoplankton community. Keratella quadrata showed significantly higher abundance at pH 6 than in other pH treatments (P < 0.001). Species richness of rotifers was unaffected by pH. 3. Most Cladocera were C. sphaericus. Although never seen in the open lake, Daphnia pulex appeared in all the pH treatments. Low pH did not control small Cladocera abundance in Delamere Lake, but probably hampered reproduction in Daphnia. Negative correlations between chlorophyll a concentrations and Daphnia in the mesocosms (r² = 0.215, P < 0.05), however, indicated the potential of large‐bodied daphniids in controlling phytoplankton. 4. Neither different combinations of Chaoborus instars (none, instars 1 and 2 and instars 3–5) nor different densities of instars 3–5 (0.15, 0.5 and 1.0 L^?1) had a negative impact on Cladocera. Daphnia pulex remained unaffected in the experiment, perhaps because of its large size, and C. sphaericus because of its high reproductive rate compensating predatory losses. 5. Very low pH in Delamere Lake might suppress Daphnia by hampering its reproduction. Consequently, Daphnia may be vulnerable to invertebrate predation even at low predator density in the lake.     

Confirmation of Ancient Polyploidy in Dahlia (Asteraceae) Species using Genomic In Situ Hybridization

The successful production of interspecific hybrids between membersof the dysploid chromosome series inDahlia offers a unique opportunityto investigate chromosome evolution. Analysis of meiotic metaphaseI in these hybrids using genomic in situ hybridization (GISH)has shown that pairing occurs both between and within parentalgenomes. These results have provided clear evidence for theallotetraploid origin of Dahlia species with 2n=32 and suggeststhat species with 2n=34 and 2n=36 have also arisen via allopolyploidy.A bivalent promoting mechanism proposed for species with 2n=32also appears to be present in Dahlia species with 2n=34 and2n=36 .Copyright 1999 Annals of Botany Company Dahlia , GISH, dysploidy, chromosome pairing, karyotype analysis, polyploidy.     

Methodologies for Surveying Herpetofauna Mortality on Rural Highways

Abstract: Road mortality can contribute to local and regional declines in amphibian and reptile populations. Thus, there is a need to accurately and efficiently identify hotspots of road-mortality for hazard assessment and mitigation. In 2002, we conducted walking and driving surveys throughout an extensive rural highway network in northern New York, USA, to evaluate survey methods and to quantify spatial and temporal patterns of herpetofauna road-mortality. In 2004, we repeated the surveys at a subset of locations to quantify interannual repeatability. Reptile and amphibian species had different peak periods of road-mortality because they differed in the causes of movements that resulted in crossings. Spatial locations of herpetofauna road-mortality were concentrated at a limited number of hotspots. Hotspots overlapped across species and were located at consistent locations across years. Results of walking and driving surveys were highly repeatable among survey teams, but driving surveys underestimated the density of road-mortality because many animals were missed. Detection failure was higher in some taxa (e.g., frogs) than others (e.g., turtles). Our results indicate that it is possible to design a valid, efficient methodology for locating hotspots of reptile and amphibian road-mortality along a road network and, thus, pinpoint priority sites for mitigation.     

The Metabolic Fate of (4-Chloro-2-Methylphenoxy)Acetic Acid in Higher Plants: I. GENERAL RESULTS

The metabolic fate of the auxin herbicide (4-chloro-2-methylphenoxy)aceticacid (MCPA) has been determined in a number of species usinga vacuum infiltration technique. In all cases MCPA became hydroxylatedto form (4-chloro-2-hydroxymethylphenoxy)acetic acid, whichaccumulated largely as a glycosidic conjugate. The nature ofthe oxidized metabolite from oat (Avena sativa L.) was verifiedby GC/MS. In all cases at least one diethyl ether-soluble conjugateof MCPA was formed; these are suggested to be amino acid conjugates.Several minor aglycones were also formed. Important speciesvariations in both the rate and quantitative nature of metabolismwere observed. Pretreatment of potato (Solarium tuberosum L.)tuber slices with unlabelled MCPA and other auxins increasedthe capacity for hydroxylation, but particularly induced theformation of an MCPA-glycoside. This was never a major metaboliteunder normal circumstances. The rate of hydroxylation was alsoenhanced by ageing in MnCl₂. Although the ether-soluble conjugatesof MCPA were stable metabolites, exogenously applied conjugateisolated from carrot (Daucus carota L.) was readily cleavedin four species. Free MCPA and the products normally derivedfrom it were identified. MCPA Metabolism Hydroxylation Conjugation     

Deer Forage Response to Herbicide and Fire in Mid-Rotation Pine Plantations

ABSTRACT Mid-rotation management practices for pine (Pinus spp.) plantations enrolled in cost-share programs have not been widely evaluated for wildlife. Mid-rotation pine plantations often have a substantial hardwood mid-story that limits growth of desirable understory forage species important to white-tailed deer (Odocoileus virginianus; deer). We treated with imazapyr herbicide and prescribed burning (HB) 11 thinned, 13–22-year-old loblolly pine (P. taeda) plantations in the Upper Coastal Plain (UCP; n = 5) and the Lower Coastal Plain (LCP; n = 6) of Mississippi, USA, enrolled in cost-share programs. We then sampled these plantations for production of important deer forages during July of 2003 and 2004, years 1 and 2 posttreatment. Deer foraging habitat was clearly improved by the HB treatment in both regions by year 2. Forb species of annual importance to deer increased in percent cover and biomass in the UCP and in biomass in the LCP. We estimated nutritional carrying capacity using a target diet quality of 14% crude protein; estimates in HB plots were 3 times greater than controls in the UCP and 19 times greater in the LCP. Although UCP sites had baseline carrying capacities nearly 8 times greater than LCP sites, the greater relative response to HB in the LCP eliminated the regional difference. Our results indicate that imazapyr herbicide treatment followed by prescribed fire is a beneficial tool for deer management in mid-rotation pine plantations.     

Landscape-Genetic Analysis of Population Structure in the Texas Gray Fox Oral Rabies Vaccination Zone

ABSTRACT In west-central Texas, USA, abatement efforts for the gray fox (Urocyon cinereoargenteus) rabies epizootic illustrate the difficulties inherent in large-scale management of wildlife disease. The rabies epizootic has been managed through a cooperative oral rabies vaccination program (ORV) since 1996. Millions of edible baits containing a rabies vaccine have been distributed annually in a 16-km to 24-km zone around the perimeter of the epizootic, which encompasses a geographic area >4 × 10⁵ km². The ORV program successfully halted expansion of the epizootic into metropolitan areas but has not achieved the ultimate goal of eradication. Rabies activity in gray fox continues to occur periodically outside the ORV zone, preventing ORV zone contraction and dissipation of the epizootic. We employed a landscape-genetic approach to assess gray fox population structure and dispersal in the affected area, with the aim of assisting rabies management efforts. No unique genetic clusters or population boundaries were detected. Instead, foxes were weakly structured over the entire region in an isolation by distance pattern. Local subpopulations appeared to be genetically non-independent over distances >30 km, implying that long-distance movements or dispersal may have been common in the region. We concluded that gray foxes in west-central Texas have a high potential for long-distance rabies virus trafficking. Thus, a 16-km to 24-km ORV zone may be too narrow to contain the fox rabies epizootic. Continued expansion of the ORV zone, although costly, may be critical to the long-term goal of eliminating the Texas fox rabies virus variant from the United States.