Mating behavior of <Emphasis Type="Italic">Abdopus aculeatus</Emphasis> (d’Orbigny 1834) (Cephalopoda: Octopodidae) in the wild

The mating system of Abdopus aculeatus incorporates sneaker matings, mate guarding, sex-specific body patterns, frequent copulations, and male–male competition for mates, making it more similar to that of aggregating decapod cephalopods than any previously known octopus social system. Large male–female A. aculeatus occupy ‘Adjacent’ (G_A) dens and copulate frequently in mate-guarding situations over successive days. Nearby individuals copulate in ‘Temporary guarding’ (G_T) and ‘Transient’ (T; non-guarding) situations, the latter of which can involve ‘Sneaker’ (S) mating. In a focal animal study of these octopuses in the wild (Sulawesi, Indonesia) we addressed the hypotheses that they demonstrate: (1) precopulatory mate choice, (2) differential copulation rates by individuals employing different mating tactics, and (3) distant sex identification. We quantified daily copulation rates of A. aculeatus of reproductive size as well as aspects of copulation duration, display, mate-competition, and mate rejection. Mating tactic correlated with daily copulation rates. ♂G_A spent significantly more time copulating than did ♂T, while ♀G_A spent more than twice as much time per day in copula than did other females. Sneaker copulations lasted longer than those by males adopting other tactics. Mate-guarding was an effective and important tactic used by males to temporarily monopolize mating with apparently non-selective females. Males demonstrated clear pre-copulatory mate choice by guarding and mating repeatedly with large females (typically ♀G_A). While foraging alone away from the den, ♂G procured ‘Transient’ copulations with unguarded females. However, mate-guarding reduced the amount of time ♂G were alone and may impede their ability to seek out new mates. Low-copulation rates by ♀T, the smallest female tactic on average, may reflect this trade-off between mate preference and mate-searching by males, or non-receptivity of some females. A male-typical body pattern (black and white stripes) appeared to facilitate distant sex identification. Although mating and aggression were often initiated before contact between individuals, same-sex copulations and intense male–female aggression were rare. By contrast frequent male–female copulations and intense male–male aggression were consistent behavioral components of mating in A. aculeatus at these sites. Because the behavioral and ecological characters conducive to this complex system are not exclusive to A. aculeatus, it is possible that other octopuses exhibit some or all of these behaviors. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Protective values for soil lead with respect to child health: a critique of UK guidelines

In 2002, The (UK) Department for Environment, Food and Rural Affairs (DEFRA) together with the Environment Agency published document SGV10 “Contaminants in soil: collation of toxicological data and intake values for humans. Lead”. This publication sets out the derivation of Soil Guideline Values for lead contamination. Values for soil lead that are protective of the health of children and also for adults are derived using the model recommended by an international task force working under the auspices of the Society for Environmental Geochemistry and Health (SEGH) (Wixson and Davies 1993, 1994). Detailed examination of the DEFRA publication shows it uses unrealistic values for two variables in the SEGH model. The consequence is both actual and has potential adverse societal impacts. These impacts could be avoided if the appropriate scientific community were regarded as stakeholders in the legislative outcome and not simply the providers of the research data.     

Within-nest temporal polyethism in the honey bee

A well-regulated division of labor has been one of the core adaptations leading to the success of the social insects. Honeybee division of labor has been classically viewed as a sequence of age-related changes in task performance. Kolmes questioned this view arguing that his studies did not support the existence of any age-related within-nest specialization. To resolve this controversy, Kolmes and Seeley conducted a joint study with mixed results. They found support for a cell cleaning caste, but diverged on whether their results supported distinct nursing and middle age castes. In this paper, I follow up on their work to resolve the question of caste number in within-nest honey bees. To determine whether nurses (typically aged 4–12 days) and middle-aged bees (aged 12–20 days) have distinct task repertoires, I conducted focal animal observations on a large number of workers in both age groups working within the same nests at the same time. The results support their being two castes of within-nest bees. Young bees specialized on brood care tasks, while middle-aged bees specialized on nectar processing and nest maintenance. Middle-aged bees were observed caring for brood in less than 1% of the observations. Moreover, both castes exhibited movement patterns that correspond to the traditional view that nurses stay within the broodnest, while middle-aged bees move around a great deal in search of work throughout the nest. A review of studies conducted since the debate of Seeley and Kolmes supports the reliability of these results. This work has relevance for proximate models of temporal polyethism, as it is often assumed by such models that there is only one within-nest caste in the honeybee.     

Reproduction on the edge: large-scale patterns of individual performance in a marine invertebrate

Reproductive output is a central attribute of life history, providing a measure of individual and population performance. The fields of ecology, biogeography, and evolutionary biology take disparate approaches in addressing spatial variation in reproduction, and thus we lack clear predictions for how reproductive output should vary geographically. We empirically investigate these contrasting theoretical approaches by determining geographic patterns in reproductive output for intertidal populations of the purple sea urchin, Strongylocentrotus purpuratus, at 15 sites spanning a large geographic distance (9 degrees span of latitude) from central California, USA, to Baja California, Mexico. Contrary to predictions from biogeography, some of the highest values of reproductive output are at sites near the species' southern range boundary. Additionally, sea urchins do not exhibit a latitudinal gradient in reproduction, but rather show considerable mesoscale variation in reproductive output. Spatial analyses reveal that this variation is correlated with coastal topographic features that are known to influence the pattern of nearshore nutrient flux and circulation. We hypothesize that urchins' reproductive output may be driven by the spatial distribution of their food supply, drift macroalgae, the abundance of which is influenced by both nutrient supply and alongshore transport processes that are coupled to topographic features. Large-scale studies such as this provide valuable insight into the causes of species' range limits, population connectivity, habitat reserve design, and forecasting the effects of climate change on species' distributions.     

Estimating trend precision and power to detect trends across grouped count data

Ecologists commonly use grouped or clustered count data to estimate temporal trends in counts, abundance indices, or abundance. For example, the U.S. Breeding Bird Survey data represent multiple counts of birds from within each of multiple, spatially defined routes. Despite a reliance on grouped counts, analytical methods for prospectively estimating precision of trend estimates or statistical power to detect trends that explicitly acknowledge the characteristics of grouped count data are undescribed. These characteristics include the fact that the sampling variance is an increasing function of the mean, and that sampling and group-level variance estimates are generally estimated on different scales (the sampling and log scales, respectively). We address these issues for repeated sampling of a single population using an analytical approach that has the flavor of a generalized linear mixed model, specifically that of a negative binomial-distributed count variable with random group effects. The count mean, including grand intercept, trend, and random group effects, is modeled linearly on the log scale, while sampling variance of the mean is estimated on the log scale via the delta method. Results compared favorably with those derived using Monte Carlo simulations. For example, at trend = 5% per temporal unit, differences in standard errors and in power were modest relative to those estimated by simulation (< or = /11/% and < or = /16/%, respectively), with relative differences among power estimates decreasing to < or = /7/% when power estimated by simulations was > or = 0.50. Similar findings were obtained using data from nine surveys of fingernail clams in the Mississippi River. The proposed method is suggested (1) where simulations are not practical and relative precision or power is desired, or (2) when multiple precision or power calculations are required and where the accuracy of a fraction of those calculations will be confirmed using simulations.     

Windows of opportunity: historical and ecological controls on Berberis thunbergii invasions

Attempts to determine characteristics that render habitats invasible to nonnative species have met with limited success. This may be because most studies focus on modern habitat conditions and do not consider invasibility in the context of a historically dynamic landscape in which both the abundance of a species and the invasibility of a site may change. We surveyed 159 currently forested sites for the occurrence and abundance of Berberis thunbergii (Japanese barberry), an invasive, nonnative shrub in forests of the northeastern United States, relative to modern environmental conditions, contemporary logging activity, and two periods of historical land use. Berberis thunbergii occurred more frequently and was more abundant in post-agricultural forests than in continuously wooded sites. This relationship was stronger for agricultural sites that were abandoned and reforested after B. thunbergii was introduced to the region than for sites that reforested prior to B. thunbergii introduction. In contrast, recent forest harvesting did not influence the occurrence or abundance of B. thunbergii. Modern soil fertility explained a significant portion of the variation in B. thunbergii occurrence, whereas site history considerably improved predictions of population density and helped evaluate potential invasion mechanisms. While land-use history covaries with soil fertility and distance to putative seed sources, the strong relationship between modern abundance patterns and historical agriculture suggests that B. thunbergii colonized recently abandoned agricultural lands in the early 20th century and then persisted and spread locally during subsequent reforestation. Our results indicate that interpretations of both native community composition and modern plant invasions must consider the importance of historical landscape changes and the timing of species introduction along with current environmental conditions.     

Source identification and assessment of sediment contamination of trace metals in Kogarah Bay,NSW, Australia

The distribution of trace metals (spatial and temporal) and sedimentary fractions were investigated to identify the concentrations and sources of trace metals within Kogarah Bay, NSW, Australia. A total of 59 surface sediments and six subsurface samples from core of the sediment were collected. The contamination factor and pollution load index indices used to evaluate environmental effects of trace metals. The study area was found to be uncontaminated with Cr and Ni, moderately contaminated with As and considerably contaminated with Cu, Zn and Pb. The concentrations of Cr and Ni were below both effect range low and effect range median, while As, Cu, Zn and Pb were slightly above effect range low. The highest concentrations of these trace metals such as Cu, Zn and Pb were found in the north, northwest and southeast of the bay, close to discharge points, stormwater outlets and around boatyards and watercrafts. The spatial distributions of metals were strongly related to muddy particles and organic matter. The temporal sediments of metals declined with increased sediment depth, which reflects accumulation of trace metals since European settlement in this area. Furthermore, the source of the trace metals was found to be stormwater outlets, gasoline fumes, boatyards and other human activities.