Genetic structure of the scleractinian coral<Emphasis Type="Italic"> Platygyra sinensis</Emphasis> in Hong Kong

Genetic structure was studied in Platygyra sinensis from six sites in Hong Kong by allozyme electrophoresis using an isoelectric focusing gel (IEF). Seven variable loci were detected using six enzyme systems. The number of alleles per locus ranged from 3.3 to 3.6 in the six samples, and heterozygosity from 0.429 to 0.540. Genotype frequencies were generally close to Hardy–Weinberg expectations. The values of unique multilocus genotype to the number of individuals for each sample (N_G/N) and observed genotypic diversity to expected genotypic diversity (G_O/G_E) were high, indicating a high level of sexual reproduction. Variation in allele frequencies among sites was low (F_ST=0.017), as was Nei's unbiased genetic distance (D), suggesting genetic similarity among sites.Communicated by T. Ikeda, Hakodate     

Geographic Range Fragmentation and Abundance in Neotropical Migratory Birds

Populations of neotropical migrant landbirds have experienced significant declines in recent years. We investigated potential consequences of these declines by examining the relationship between abundance and fragmentation of geographic ranges of species on the North American breeding grounds. We estimated areograpbic fragmentation using the box dimension of a species' geographic range and demographic fragmentation using the fractal dimension of the semivariance function calculated from samples of population abundance across species' geographic ranges. We found a negative relationship between average abundance and demographic fragmentation for neotropical migrants, but not for residents. We also showed that demographic fragmentation and areographic fragmentation are inversely related for residents, but not for neotropical migrants. These results imply that neotropical migrants may be more sensitive to extinction than are residents.     

Effects of Land-Use and Tsetse Fly Control on Bird Species Richness in Southwestern Ethiopia

Successful control of tsetse (Glossina spp.)-transmitted trypanosomiasis in the Ghibe Valley, Ethiopia, appears to have accelerated conversion of wooded grassland into cropland. Land conversion, in turn, may have fragmented wildlife habitat. Our objective was to assess the influence of the expansion of agricultural land-use, brought about by tsetse control, on ecological properties by using bird species richness and composition as indicators of environmental impacts. We sampled bird species richness and composition (using Timed-Species counts) and habitat structure (using field sampling and remote sensing) in four land cover/land-use types in areas subjected to tsetse fly control and adjacent areas without control. At the height of the growing season bird species numbers and vegetative complexity were greater in the small-holder, oxen-plowed fields and riparian woodlands than in wooded grasslands or in large-holder, tractor-plowed fields. Species composition was highly dissimilar (40–70% dissimilarity) comparing among land-use types, with many species found only in a single type. This implies that trypanosomiasis control that results in land conversion from wooded grasslands to small-holder farming in this region may have no adverse impacts on bird species numbers but will alter composition. These results also suggest that moderate land-use by humans (e.g., small-holder field mosaics) increases habitat heterogeneity and bird species richness relative to high levels of use (e.g., tractor-plowed fields). Tsetse control may be indirectly maintaining species richness in the valley by encouraging the differential spread of these small-scale, heterogeneous farms in place of large-scale, homogeneous farms. Nevertheless, if the extent of small-holder farms significantly exceeds that of present levels, negative impacts on bird species richness and large shifts in species composition may occur.     

Stable lead isotope profiles in smelter and general urban communities: a comparison of environmental and blood measures

High-precision lead isotope ratios and lead concentrations have been compared statistically and graphically in women of child-bearing age (n = 77) from two smelter communities and one general urban community to evaluate the relative contributions to blood lead of tissue lead stores and lead from the contemporaneous environment (soil, floor dust, indoor airborne dust, water, food). Blood lead (PbB) contents were generally low (e.g. <10 g dL^–1). Statistically significant isotopic differences in blood and environmental samples were observed between the three cities although isotopic differences in blood for individual subjects living in close proximity (200 m radius) was as large as the differences within a city. No single environmental measure dominated the biological isotope profile and in many cases the low levels of blood lead meant that their isotopic profiles could be easily perturbed by relatively small changes of environmental exposure. Apportioning of sources using lead isotopes is possibly not feasible, nor cost effective, when blood lead levels are <5 g dL^–1. Interpretations based on statistical analyses of city-wide data do not give the same conclusions as when the houses are considered individually. Aggregating data from multiple subjects in a study such as this obscures potentially useful information. Most of the measures employed in this study, and many other similar studies, are markers of only short-to-medium integration of lead exposure. Serial sampling of blood and longer sampling times, especially for household variables, should provide more meaningful information.     

Can Eco-Labels Tune a Market? Evidence from Dolphin-Safe Labeling

In this paper we test whether the dolphin-safe labels altered consumer purchases of tuna. We also provide a partial measure of the total welfare effects of the dolphin-safe labeling policy. The results confirm our hypothesis that the dolphin–tuna controversy and the subsequent implementation of dolphin-safe labeling affected consumer behavior. Further, the paper provides market-based evidence that consumers can respond to eco-labels; the dolphin-safe label increased the market share of canned tuna. The welfare analysis provides a partial measure of society's willingness to pay to avoid personally contributing to dolphin mortality as a result of tuna fishing.     

Worker population structure and gyne production in the ant Myrmica

Summary Wild colonies of Myrmica rubra L. were sampled and cultured in the laboratory to assess their reproductive capability. Correlation analysis was then used to relate the reproductive performance to a number of worker population characteristics. This revealed an association between the magnitude of gyne production and the proportion of nurses in the population. The absence of big workers also increased gyne production.Artificially composed cultures were then made and used to confirm greater resistance of nurses and small workers to queen domination.It is suggested that rapidly growing colonies will have higher proportions of young nurse workers refractory to queens and able to deliver the food necessary for gyne production. Such colonies could optimise their reproduction in this way.     

Heritable variation in learning performance affects foraging preferences in the honey bee (Apis mellifera)

There has now been an abundance of research conducted to explore genetic bases that underlie learning performance in the honey bee (Apis mellifera). This work has progressed to the point where studies now seek to relate genetic traits that underlie learning ability to learning in field-based foraging problems faced by workers. Accordingly, the focus of our research is to explore the correlation between laboratory-based performance using an established learning paradigm and field-based foraging behavior. To evaluate learning ability, selected lines were established by evaluating queens and drones in a proboscis extension reflex (PER) conditioning procedure to measure learning in a laboratory paradigm—latent inhibition (LI). Hybrid queens were then produced from our lines selected for high and low levels of LI and inseminated with semen from many drones chosen at random. The genetically diverse worker progeny were then evaluated for expression of LI and for preference of pollen and/or nectar during foraging. Foragers from several different queens, and which had resulted from fertilization by any of several different drone fathers, were collected as they returned from foraging flights and analyzed for pollen and nectar contents. They were subsequently evaluated for expression of LI. Our research revealed that pollen foragers exhibited stronger learning, both in the presence (excitatory conditioning) and absence (LI) of reinforcement. The heightened overall learning ability demonstrated by pollen foragers suggests that pollen foragers are in general more sensitive to a large number of environmental stimuli. This mechanism could contribute toward explanations of colony-level regulation of foraging patterns among workers.Communicated by R. Page