Sex allocation in a monomorphic seabird with a single-egg clutch: test of the environment, mate quality, and female condition hypotheses

Sex allocation theory posits that mothers should preferentially invest in sons when environmental conditions are favorable for breeding, their mates are of high quality, or they are in good body condition. We tested these three hypotheses in rhinoceros auklets (Cerorhinca monocerata), monomorphic seabirds that lay a single-egg clutch, in 2 years that differed in environmental conditions for breeding. Results supported the environment and mate quality hypotheses, but these effects were interactive: offspring sex was independent of paternal traits in the poor year for breeding, while females mated to larger and more ornamented males reared more sons in the better year. Conversely, offspring sex was unrelated to female condition, as indexed by hatching date. We propose that good rearing conditions enable females to rear sons possessing the desirable phenotypic attributes of their mates. Results also supported two critical assumptions of sex allocation theory: (1) dimorphism in offspring condition at independence: daughters fledged with higher baseline levels of corticosterone than sons and (2) differential costs of rearing sons versus daughters: mothers rearing sons when environmental conditions were poor completed parental care in poorer condition than mothers rearing daughters in the same year and mothers rearing either sex when conditions were better. These novel results may help to explain the disparate results of previous studies of avian sex allocation.     

Tracking post-nesting movements of loggerhead turtles (Caretta caretta) with sonic and radio telemetry on the southwest coast of Florida, USA

Nine post-nesting loggerhead turtles (Caretta caretta) were tracked using sonic and radio telemetry. Tracking began immediately after the turtles left the beach and continued until contact was either lost or terminated. As sonic tags transmit continuously underwater, they were much more effective than the radio tags in determining the paths of the turtles. Radio tags transmit only at the surface and were useful in ascertaining submergence durations. For nine of the ten turtles tracked with sonic signals, the gross movement was away from the beach in a westerly direction. The tracking periods ranged from 3.35 to 8.25 h, while the straight-line movements ranged from 3.05 to 12.88 km, respectively. Sixty-seven percent of the submergence durations recorded were <3 min. This respiratory behavior suggests continuous swimming, and the paths of the turtles suggested directed movement offshore immediately after nesting. The gradual littoral slope and lack of nearshore structure in this part of the Gulf of Mexico could be contributing factors to the patterns of dispersal observed, as benthic structures provide resting and foraging habitat for loggerheads.     

Measurement of vapour pressures of Fenitrothion and Matacil

Vapour pressures of Fenitrothion and Matacil were measured using a gas saturation method. Polyurethane foam was used to trap the volatilized materials from sand and glass surfaces, and Porapak Q for trapping materials volatilized from leaf surfaces. The vapour pressures (VP) were linearly related to the reciprocal temperature by the equation: $\text{Log (VP)}\text{= 6.3362 ? (}\text{3197.8}\text{T}\text{)}$ for a sand incorporated with Fenitrothion and $\text{Log (VP)}\text{= 8.8316 ? (}\text{4021.4}\text{T}\text{)}$ for a sand incorporated with Matacil. The greatest vapour loss rates were from sand incorporated with fenitrothion, followed by vapour loss rates from glass surfaces; the least vapour loss rate was from leaf surfaces.     

Multiscale patterns of genetic structure in a marine snail (Solenosteira macrospira) without pelagic dispersal

The northern Gulf of California (NGC) is one of the most dynamic and productive marine ecosystems in the world, yet knowledge about population connectivity and dispersal patterns is lacking for many of its resident species. Using nuclear and mitochondrial markers, we investigated the effects of open water, geographical distance and suitable habitat on patterns of genetic structure of Solenosteira macrospira, a benthic buccinid whelk with direct development. We collected samples in April 2004, 2005 and May 2007 from the upper NGC (31°34.39″N, 114°44.45″W). Phylogenetic analyses, hierarchical analyses of variance and Bayesian assignment tests substantiated a break between the east and west coasts. Genetic distance between population pairs increased with geographical distance, but only when assuming a U-shaped dispersal pathway over the open water of the NGC. Given S. macrospira’s association with rocky intertidal habitats, and its limited dispersal potential, we assumed that the geographical distribution of rocky habitat would play a significant role in genetic differentiation of S. macrospira. Nevertheless, populations separated by sand were more similar than populations separated by rocks. The influence of open water, geographical distance and suitable habitat (rocks vs. sand) also varied significantly across different genetic markers that presumably evolve at different rates. Specifically, the more rapidly evolving nuclear microsatellites suggested that physical transport processes strongly influence genetic differentiation on contemporary time scales, even in a species with direct benthic development. This underscores the strong, and potentially homogenizing, effect of present-day ocean circulation patterns in the NGC.     

Hydrology influences population genetic structure and connectivity of the intertidal amphipod Corophium volutator in the northwest Atlantic

The mechanisms driving genetic structure in marine systems are elusive due to the difficulty of identifying temporal and spatial barriers to dispersal. By studying marine invertebrate species with limited dispersal potential, genetic structure can be directly related to physical and biological factors restricting connectivity. In the northwest Atlantic, the benthic brood-rearing amphipod Corophium volutator is distributed across basins with distinct circulation patterns and has the potential to disperse passively during its adult stage. We analyzed spatial genetic variation and migration rates across C. volutator’s North American range with sequence data for mitochondrial DNA and three novel nuclear markers using frequency and coalescent-based methods. We found low genetic differentiation within basins, but strong subdivision within the Bay of Fundy and a striking biogeographic break between the Bay of Fundy and Gulf of Maine, suggesting that genetic drift may act on populations in which connectivity is restricted due to the limitation of passive dispersal by hydrological patterns.     

An Integrated Approach to Street Canyon Pollution Modelling

An integrated method for the prediction of the spatial pollution distribution within a street canyon directly from a microscopic traffic simulation model is outlined. The traffic simulation package Paramics is used to model the flow of vehicles in realistic traffic conditions on a real road network. This produces details of the amount of pollutant produced by each vehicle at any given time. The authors calculate the dispersion of the pollutant using a particle tracking diffusion method which is superimposed on a known velocity and turbulence field. This paper shows how these individual components may be integrated to provide a practical street canyon pollution model. The resulting street canyon pollution model provides isoconcentrations of pollutant within the road topography.     

Effect of elemental sulphur on the vegetation of a Lodgepole pine stand

Shrub and herb cover decreased 98% and diversity 76% after particulate elemental sulphur was deposited in a Pinus contorta Loudon var. latifolia Engelm. forest in west-central Alberta, Canada. Decreases were measured over four years and, initially, were greater for the herbs than they were for the shrubs. The decline in the herbs occurred one year before decreases in half the shrub species. The dramatic decline of the vegetation appeared related to the changes in the soil chemistry of the surface organic horizon following the oxidation of elemental sulphur.     

Monitoring the health of a forest: A Canadian approach

In Canada, acid rain is the generic term encompassing all forms of air pollution — wet and dry deposition, gaseous pollutant concentrations, and airborne particulates. It was because these pollutants, alone or in combination, may directly or indirectly affect the heath of Canada's forests, that in 1984, the Canadian Forestry Service initiated a national forest monitoring program (Acid Rain National Early Warning System or ARNEWS).Research studies on pollutant effects of the past 15–20 years have demonstrated that it is not possible to define specific symptoms of acid rain or mixtures of pollutants on native tree species or specific responses of the forest ecosystem. Consequently, ARNEWS monitored incipient acid rain effects by determining the forest's state of health rather than by concentrating on specific pollutant responses.The detection system entails experienced insect and disease survey forest rangers assessing both specific plots and the forest as a whole for extraordinary forest damage. The techniques used include mensurational and symptomatological measurements as well as evaluation of stands for damage from natural and anthropogenic causes. Critical also to the system was the capability of the Canadian Forestry Service to support the detection system with research staff who could carry out studies to explain any abnormalities in forest condition detected during the annual surveys. The ultimate outcome of the monitoring system if unexplained forest damage is detected is a research project on possible causes.Contribution from Fourth World Wilderness Congress — Acid Rain Symposium, Denver (Estes Park), Colorado, September 11–18, 1987.