Scales of variation in otolith elemental chemistry of juvenile staghorn sculpin (<Emphasis Type="Italic">Leptocottus armatus</Emphasis>) in three Pacific Northwest estuaries

Although distinct otolith elemental signatures are often observed in fish collected from different estuaries, significant differences are also observed among sites within estuaries. Variation at these smaller spatial scales is not well quantified and has the potential to lead to inappropriate interpretations of otolith elemental data. To quantify variation at multiple scales, the otolith elemental composition (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca, and Pb:Ca) of juvenile staghorn sculpin (Leptocottus armatus Girard, 1854) collected from five sites within three estuaries, the Columbia River (two sites) and Coos Bay (one site), Oregon, and Humboldt Bay, California (two sites), was examined. Using laser ablation-inductively coupled plasma mass spectrometry, each otolith was sampled at three zones: (1) within the primordium, which represents the egg and early larval periods; (2) at the outer edge, which represents the juvenile period just prior to collection; and (3) midway between the primordial and edge samples, which represents the late larval and early juvenile period. There were significant differences in otolith metal-to-calcium ratios at all scales examined. Using multi-element otolith signatures, fish were classified to estuary and site within estuary with relatively high levels of accuracy (av = 70–90%). The largest differences in metal-to-calcium ratios were observed between sites within estuaries (<5 km apart) and the smallest differences were observed among otolith zones. Variation in otolith chemistry may be used to provide information on probable habitat use by estuarine fish but studies must be carefully designed. Electronic supplementary material  Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Perceptions of executive pay: does pay enhance a leader's aura?

This study used policy capturing to test the ‘figurehead’ assertion that executive pay level contributes to followers' perceptions of a leader's ability. Findings indicated human capital factors including promotion history, degree earned and university prestige all furnished more explanation than pay for CEO ratings. Results challenged the underlying logic of figurehead explanations for executive compensation to the rank and file. Copyright © 2001 John Wiley & Sons, Ltd.     

IMMEDIATE CONTEXTUAL INFLUENCES ON MATERNAL BEHAVIOR: ENVIRONMENTAL AFFORDANCES AND DEMANDS

Although it is commonly recognized that parenting is multiply determined, mechanisms by which the context influences parental behavior have rarely been examined. In this paper, the role of environmental affordances and demands are described and tested in two observational studies. In Study 1, mothers and their 3-year-old children were observed in three settings where affordances and demands differed: the home, park, and laboratory. In Study 2, mothers and their children engaged in three laboratory conditions in which the amount of demands on the mother was manipulated. Several child-rearing variables showed systematic relations with the presence of affordances and demands. It is concluded that affordances and demands play an important role in influencing maternal behavior by acting as environmental cues for place-related behavior. Further, it is proposed that parental perceptions of the immediate context and the recognition of appropriate environmental cues are paramount in understanding the variability of parental behavior across situational contexts.     

Vascular plant extinction in the continental United States and Canada

Extinction rates are expected to increase during the Anthropocene. Current extinction rates of plants and many animals remain unknown. We quantified extinctions among the vascular flora of the continental United States and Canada since European settlement. We compiled data on apparently extinct species by querying plant conservation databases, searching the literature, and vetting the resulting list with botanical experts. Because taxonomic opinion varies widely, we developed an index of taxonomic uncertainty (ITU). The ITU ranges from A to F, with A indicating unanimous taxonomic recognition and F indicating taxonomic recognition by only a single author. The ITU allowed us to rigorously evaluate extinction rates. Our data suggest that 51 species and 14 infraspecific taxa, representing 33 families and 49 genera of vascular plants, have become extinct in our study area since European settlement. Seven of these taxa exist in cultivation but are extinct in the wild. Most extinctions occurred in the west, but this outcome may reflect the timing of botanical exploration relative to settlement. Sixty-four percent of extinct plants were single-site endemics, and many occurred outside recognized biodiversity hotspots. Given the paucity of plant surveys in many areas, particularly prior to European settlement, the actual extinction rate of vascular plants is undoubtedly much higher than indicated here.     

The effect of water temperature on drilling and ingestion rates of the dogwhelk Nucella lapillus feeding on Mytilus edulis mussels in the laboratory

In highly seasonal intertidal habitats, changes in temperature through the year may drive substantial shifts in feeding and growth rates of organisms. For the dogwhelk Nucella lapillus, attacking and consuming Mytilus edulis mussels can take hours or days, depending on temperature. Handling time of dogwhelks feeding on mussels is therefore greatly affected by ocean temperature. I recorded attack time in the laboratory, partitioned into drilling and consumption time, for juvenile dogwhelks across a range of seawater temperatures representative of field seawater temperatures during the main growing seasons of summer and autumn. The combined length of a drilling attack and subsequent ingestion time tripled across the 10 °C decline in water temperatures from July through November, driven primarily by an increase in ingestion time. The observed reduction in handling time, coupled with projected sea surface warming in New England by the end of the twenty-first century, could extend the length of the growing season for Nucella and subsequently have cascading effects on the prey community.     

General methods for sensitivity analysis of equilibrium dynamics in patch occupancy models

Sensitivity analysis is a useful tool for the study of ecological models that has many potential applications for patch occupancy modeling. Drawing from the rich foundation of existing methods for Markov chain models, I demonstrate new methods for sensitivity analysis of the equilibrium state dynamics of occupancy models. Estimates from three previous studies are used to illustrate the utility of the sensitivity calculations: a joint occupancy model for a prey species, its predators, and habitat used by both; occurrence dynamics from a well-known metapopulation study of three butterfly species; and Golden Eagle occupancy and reproductive dynamics. I show how to deal efficiently with multistate models and how to calculate sensitivities involving derived state variables and lower-level parameters. In addition, I extend methods to incorporate environmental variation by allowing for spatial and temporal variability in transition probabilities. The approach used here is concise and general and can fully account for environmental variability in transition parameters. The methods can be used to improve inferences in occupancy studies by quantifying the effects of underlying parameters, aiding prediction of future system states, and identifying priorities for sampling effort.