Effects of location,exposure and physical structure on juvenile recruitment of the sea urchin Strongylocentrotus droebachiensis in the Gulf of Maine

Summary

Studies of juvenile recruitment of the green sea urchin Strongylocentrotus droebachiensis in the Gulf of Maine were conducted during the summer of 1995. These experiments confirmed 12 years of previous observations that settlement only occurs during the months of June and July. Settlement panels were placed at a series of sites along the Maine and New Hampshire coastline to compare recruitment in the northeastern and southwestern regions of the Gulf of Maine. The densities of urchins recruiting in Casco Bay and at the Isles of Shoals were two orders of magnitude higher than those from Eastport and Winter Harbor. There was a discontinuity in settlement densities at Penobscot Bay. Experiments conducted at the Isles of Shoals showed a positive relationship between water motion and larval supply, but neither parameter correlated with recruitment density over eight stations. Contrary to previous results, recuitment was greater within natural, as well as, artificial kelp beds compared to urchin barren areas and control panels outside the experimental kelp beds. The impact of changing community structure due to urchin harvesting was discussed as an factor influencing differences in juvenile urchin recruitment.     

THE MEASUREMENT OF VOCAL AMPLITUDE AND VOCAL RADIATION PATTERN IN BLUE MONKEYS AND GREY-CHEEKED MANGABEYS

ABSTRACT

The substitution method was adopted from industrial acoustics (Francois and de Montussaint 1972) to “eliminate the influence of the environment” on measurements of the amplitude of vocalizations given by blue monkeysCercopithecus mitis and grey-cheeked mangabeysCercocebus albigena. Measurements were conducted of sound power and sound pressure level of representative utterances. Monkey vocal radiation patterns were also measured. The results showed that vocal amplitude ranged from 62 dB to 100 dB in sound pressure (re 1 pw). At a distance of 2 m, the loudest calls approached an amplitude of 110 dB SPL, a level about equal to the loudest human yell. The measurements of call amplitude conducted here exceeded those derived from the field by approximately 10 dB. It was shown that the discrepancy in amplitude between these laboratory based measurements and earlier measurements conducted under field conditions (Waser and Waser 1977) was probably due to destructive interference between the direct wave and the “ground wave”, a phase shifted wave reflected from the ground. Measurements of radiation patterns of primate vocalizations showed that, like human speech, directivity was a function of frequency, with high-frequency components being radiated more directionally than lower-frequency components. However, primate utterances were in general radiated more omnidirectionally than was human speech.     

Representation of Landcover Along Breeding Bird Survey Routes in the Northern Plains

ABSTRACT The North American Breeding Bird Survey (BBS) is used extensively to make inferences about populations of many North American bird species and is increasingly being used for avian conservation planning. How well BBS routes represent the landscape is poorly known, even though accuracy of representation could significantly affect inferences made from BBS data. We used digital landcover data to examine how well landcover within 400-m buffers around BBS routes represented the surrounding landscape (the route neighborhood) for 52 routes in the Prairie Pothole Region of North Dakota and South Dakota. Differences in composition between landcover along BBS routes and the route neighborhood were not statistically significant for upland cover classes. The area of temporary and seasonal wetland basins was accurately represented by BBS routes in our study area, but the area of semipermanent and permanent wetland basins was significantly underrepresented along BBS routes. Number of wetland basins and upland patches was higher along routes. Area of urban, forest, and hay landcover classes was higher along routes, although differences were not statistically significant. Amount of bias in landcover representation was negatively correlated with the proportion of each landcover type in the study area, but bias was not correlated with area of the route neighborhoods. Differences between landcover along BBS routes and the route neighborhood were primarily attributable to increased anthropogenic activity along roads and siting of roads away from relatively large, deep water bodies. Our results suggest that inferences made from BBS data in our study region are likely biased for species that are associated with deeper-water habitats or are strongly influenced by landscape fragmentation. Inferences made from BBS data for species associated with uplands or shallow wetlands are less likely to be biased because of differences in landcover composition.     

Mandible of the giant panda (Ailuropoda melanoleuca) compared with other Chinese carnivores: functional adaptation

The aim of this study was to understand the mandible of the giant panda in morphometric terms to explore differences between the giant panda and other carnivores distributed in China, in terms of functional adaptation. Twelve mandibular variables were studied using bivariate (allometry) and multivariate (principal components analysis, PCA, and discriminant functional analysis, DFA) tools. When deviations were produced from allometric baselines consisting of all the species studied, the giant panda displayed a much more developed mandibular structure than the bear, leopard, and tiger. This may be related to its specific dietary preference for bamboo, which has very strong fibers. Results also indicate that the mandibular structure among carnivores mainly reflects the differences in their dietary preferences and functional adaptation. Three groups were found referring to dispersal profiles expressed by the first two axes of PCA and DFA: (1) the two panda species – the herbivorous carnivores; (2) the black bear – the omnivorous carnivore; and (3) the tiger and leopard – the hypercarnivores. Nevertheless, a significant separation between the two panda species was also found with the profiles displayed by the first and third axes of DFA. In addition to no close evolutionary relationship and phylogenetic development, a noticeable separation between the two panda species found in DFA analysis may be associated with their variation in consuming different parts of the bamboo plant: the giant panda feeds on stems and the red panda feeds on leaves.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 449–456.     

Elevated atmospheric carbon dioxide increases soil carbon

The general lack of significant changes in mineral soil C stocks during CO₂‐enrichment experiments has cast doubt on predictions that increased soil C can partially offset rising atmospheric CO₂ concentrations. Here, we show, through meta‐analysis techniques, that these experiments collectively exhibited a 5.6% increase in soil C over 2–9 years, at a median rate of 19 g C m^?2 yr^?1. We also measured C accrual in deciduous forest and grassland soils, at rates exceeding 40 g C m^?2 yr^?1 for 5–8 years, because both systems responded to CO₂ enrichment with large increases in root production. Even though native C stocks were relatively large, over half of the accrued C at both sites was incorporated into microaggregates, which protect C and increase its longevity. Our data, in combination with the meta‐analysis, demonstrate the potential for mineral soils in diverse temperate ecosystems to store additional C in response to CO₂ enrichment.     

Eleven polymorphic microsatellite loci for the salmonid trematode Plagioporus shawi

We isolated and characterized 11 microsatellite loci from Plagioporus shawi, a parasitic trematode of salmonid fishes (Oncorhynchus spp.). Extensive polymorphism (expected heterozygosities ranging from 0.476 to 0.981 and number of alleles from 10 to 55) was found in a sample of 94 trematodes from 24 infected cutthroat trout (Oncorhynchus clarki) individuals. Nine of the 11 loci will be useful for future genetic studies on within population dynamics of P. shawi.     

Scale-independent criteria and scale-dependent agents determining the structure of a ground cricket mosaic hybrid zone (Allonemobius socius – Allonemobius fasciatus)

The structure of the hybrid zone between the ground crickets, Allonemobius socius and Allonemobius fasciatus , approximates an environmental mosaic based on temperature/moisture at regional spatial scales. In the present study, we show that the micro-geographic spatial structure (i.e. single fields) of this hybrid zone is governed by the same criteria. Thus, the criteria that structure this hybrid zone are scale independent, even though the agents that implement these criteria may differ at various scales (climate, latitude, and elevation at regional scales; grass height, slope aspect, and field use at micro-geographic scales). Additionally, the study demonstrates a previously unknown barrier to genetic exchange in this system that acts before conspecific sperm precedence.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 777–796.     

Selecting discriminant function models for predicting the expected richness of aquatic macroinvertebrates

1. The predictive modelling approach to bioassessment estimates the macroinvertebrate assemblage expected at a stream site if it were in a minimally disturbed reference condition. The difference between expected and observed assemblages then measures the departure of the site from reference condition. 2. Most predictive models employ site classification, followed by discriminant function (DF) modelling, to predict the expected assemblage from a suite of environmental variables. Stepwise DF analysis is normally used to choose a single subset of DF predictor variables with a high accuracy for classifying sites. An alternative is to screen all possible combinations of predictor variables, in order to identify several ‘best’ subsets that yield good overall performance of the predictive model. 3. We applied best‐subsets DF analysis to assemblage and environmental data from 199 reference sites in Oregon, U.S.A. Two sets of 66 best DF models containing between one and 14 predictor variables (that is, having model orders from one to 14) were developed, for five‐group and 11‐group site classifications. 4. Resubstitution classification accuracy of the DF models increased consistently with model order, but cross‐validated classification accuracy did not improve beyond seventh or eighth‐order models, suggesting that the larger models were overfitted. 5. Overall predictive model performance at model training sites, measured by the root‐mean‐squared error of the observed/expected species richness ratio, also improved steadily with DF model order. But high‐order DF models usually performed poorly at an independent set of validation sites, another sign of model overfitting. 6. Models selected by stepwise DF analysis showed evidence of overfitting and were outperformed by several of the best‐subsets models. 7. The group separation strength of a DF model, as measured by Wilks’Λ, was more strongly correlated with overall predictive model performance at training sites than was DF classification accuracy. 8. Our results suggest improved strategies for developing reliable, parsimonious predictive models. We emphasise the value of independent validation data for obtaining a realistic picture of model performance. We also recommend assessing not just one or two, but several, candidate models based on their overall performance as well as the performance of their DF component. 9. We provide links to our free software for stepwise and best‐subsets DF analysis.