Parental care and EGG size in salamanders: An examination of the safe harbor hypothesis

Summary The safe harbor hypothesis includes the suggestion that parental care causes the embryonic stage to be the safest harbor, and, therefore, egg size will increase in populations with parental care to decrease the duration of subsequent, higher risk stages. Neither the safe habor hypothesis nor r and K theory seem adequate to explain the correlation between egg size and the presence/absence of parental care among salamanders, a group in which there is a further correlation between the larval (hatchling) habitat and egg size/parental care. Pond-breeding salamanders generally have small eggs and lack parental care, and stream-breeding salamanders generally have large eggs and parental care. I argue that the fundamental difference in the food available to hatchling salamanders between lentic (plankton-rich) and lotic (plankton-poor) environments selects for relatively lower parental investment in the lentic environment. From the standpoint of parental fitness, small (more numerous) hatchlings have a greater payoff where the available food is mall and dense (zooplankton in lentic environments), and large hatchlings are selectively advantageous where the food is of large size and less dense (benthic invertebrates in lotic environments). Selection for larger hatchlings in lotic environments results in longer embryonic periods and,ceteris paribus, greater total embryonic mortality. Embryo hiding and guarding have evolved among lotic-breeding salamanders as compensatory mechanisms to reduce the rate of embryonic mortality. In this view, parental care is a consequence of selection for larger egg size and not an umbrella that allows egg size to increase, contrary to the safe harbor hypothesis. The relationship between variance in parental investment and food available to offspring, developed here for salamanders, may be of general significance. YosiakiIt?, a critic of r and K theory, independently arrived at a similar conclusion from a broader data base.     

The family building life course and contraceptive use: Nang Rong, Thailand

This paper incorporates the insights of the life course perspective in an examination of the determinants of contraceptive use. It views decision-making about contraceptive methods in the context of personal history and the broader social setting. Three stages in the reproductive life course of married women are considered. In the early years, timing decisions dominate. Contraception is used to delay the first birth and control the tempo of fertility. Mid-career, the major concern is whether to have a sterilizing operation. Towards the end of the fecund period, couples must decide when to stop using contraception, given that they have not already opted for sterilization. We examine choice among nonpermanent methods, as well as sterilization, in the context of a theoretical model that explicitly recognizes the permanence of the sterilization decision. Our statistical procedures control for unobserved community influences. The data are from Nang Rong district, Thailand, a relatively poor area near the Cambodian border under going substantial socioeconomic change during the 1980s. Our results clearly show variation in method choice over the reproductive life course, and variation in the effects of specific determinants including age of husband and wife, living arrangements, and village location. They also demonstrate gains in the understanding of any particular stage in the life course that accrue from an integrated examination of all of them.     

Population and Upland Crop Production in Nang Rong,Thailand

This paper estimates village-level models of the effects of population variables on the area devoted to upland crop production in Nang Rong district, Thailand. The expansion of upland crops is part of the growth of market agriculture in Nang Rong, and a correlate of deforestation in this setting, The results show that population density (measured as density of village settlement) negatively affects area in upland crops while population growth has a positive effect. Changes in land use associated with population change appear to radiate outward from nuclear village centers. As cash economies are established in rural settings, household formation requires a source of income as well as a subsistence stake. Growth in the population of households is a stronger predictor of the area in upland crops than growth in the number of persons.     

Diet of Florida coyotes in a protected wildland and suburban habitat

Coyotes (Canis latrans) arrived to Florida (USA) in the 1960s and are currently found throughout most of the state. The purpose of this study was to determine if the diet of Florida coyotes differed between suburban and wildland habitat types or across seasons. Fresh coyote fecal samples were collected from wildland and suburban habitats in Pinellas County, Florida (USA; 27°54′N, 82°41′W) from May 2005 to March 2007. Diet items in the 49 wildland and 71 suburban samples were identified to the lowest possible taxonomic level by gross morphological characteristics and medullary configurations of dorsal guard hairs. A Poisson regression was utilized to determine the main and interactive effects of habitat and season on the number of different food items per sample. Coyotes in the wildland habitat had greater diet diversity than suburban coyotes. In addition, anthropogenic waste was recovered over twice as often from coyote fecal samples collected in the suburban habitat. In the wildland habitat, vegetative matter (96%), Insecta (53%), and Rodentia (45%) were recovered most often, as opposed to berries (56%) and Lagomorpha (32%) in the suburban habitat. In both habitats, vegetative matter, berries, and Lagomorpha were recovered most often from coyote fecal samples, whereas Odocoileus virginianus, Lagomorpha, and berries varied the most between wet and dry seasons. This study suggests that as urbanization increases, diet diversity for the coyote will likely decrease and consumption of anthropogenic items will likely increase. As a result of this, human–coyote conflicts may become more common—particularly in counties, like Pinellas, that are undergoing urbanization.     

Managing a crisis of confidence in Nigeria's banking and financial industry

An ongoing crisis of confidence in the banking and financial industry in Nigeria's emerging economy calls for using integrated marketing communications (IMC) in optimizing five potentially normative actions as a beachhead in procuring corporate benefits from three variables that predict significantly customers’ favorable impressions of business: satisfaction, trust, relationship commitment. The actions: (a) personalize the stakeholder experience, (b) integrate ethics into the workplace and into corporate communications, (c) participate in training sessions in applied ethics, (d) use brandstanding expansively and integratively, and (e) conduct rigorous outcomes assessment and disseminate its results promptly to stakeholders.     

International Migration as a Tool in Development Policy: A Passing Phase?

This essay examines the recent emergence of migration and development as a major area of policy concern. The focus up to now has been almost entirely upon international migration, which accounts for the minority of people who move. A consensus has emerged that migration can be managed so as to promote development, and the essay critically assesses three of the major areas of concern: remittances, skilled migration, and the diaspora. While welcoming the growing acceptance that migration is no longer seen as negative for development, the essay cautions against essentializing migration and placing too great a responsibility upon migrant agency at the expense of the institutional change necessary to bring about development. Internal as well as international migrations will need to be integrated into any development framework, and it is further argued that these migrations are essentially a consequence of development. Planning for migration as an outcome rather than a cause of development is likely to provide a more balanced policy approach.     

Dynamic models and cross-sectional data: Estimation of dynamic parameters in cross-sectional data

Serious difficulties in the interpretation of structural coefficients may arise when a static, cross-sectional model is applied to data generated by a dynamic process. One alternative is to collect data at several points in time, and specify the dynamic features that are proposed to exist. Another alternative is discussed here. Overidentifying restrictions in a static simultaneous equation system may, under certain conditions, be used to identify dynamic parameters (autoregression and autocorrelation coefficients) when data are available at only one point in time.     

Model Selection and Estimation with Quantal‐Response Data in Benchmark Risk Assessment

This article describes several approaches for estimating the benchmark dose (BMD) in a risk assessment study with quantal dose‐response data and when there are competing model classes for the dose‐response function. Strategies involving a two‐step approach, a model‐averaging approach, a focused‐inference approach, and a nonparametric approach based on a PAVA‐based estimator of the dose‐response function are described and compared. Attention is raised to the perils involved in data “double‐dipping” and the need to adjust for the model‐selection stage in the estimation procedure. Simulation results are presented comparing the performance of five model selectors and eight BMD estimators. An illustration using a real quantal‐response data set from a carcinogenecity study is provided.