Proximate Determinants (proximate + determinant)

Distribution by Scientific Domains


Selected Abstracts


Proximate Determinants of Reproductive Skew in Polygyne Colonies of the Ant Formica fusca

ETHOLOGY, Issue 11 2002
Minttumaaria Hannonen
Understanding the determinants of reproductive skew (the partitioning of reproduction among co-breeding individuals) is one of the major questions in social evolution. In ants, multiple-queen nests are common and reproductive skew among queens has been shown to vary tremendously both within and between species. Proximate determinants of skew may be related to both queen and worker behaviour. Queens may attempt to change their reproductive share through dominance interactions, egg eating and by changing individual fecundity. Conversely, workers are in a position to regulate the reproductive output of queens when rearing the brood. This paper investigates queen behaviour at the onset of egg laying and the effect of queen fecundity and worker behaviour on brood development and reproductive shares of multiple queens in the ant Formica fusca. The study was conducted in two-queen laboratory colonies where the queens produced only worker offspring. The results show that in this species reproductive apportionment among queens is not based on dominance behaviour and aggression, but rather on differences in queen fecundity. We also show that, although the queen fecundity at the onset of brood rearing is a good indicator of her final reproductive output, changes in brood composition occur during brood development. Our results highlight the importance of queen fecundity as a major determinant of her reproductive success. They furthermore suggest that in highly derived polygyne species, such as the Formica ants, direct interactions as a means for gaining reproductive dominance have lost their importance. [source]


An examination of perceived behavioral control: Internal and external influences on intention

PSYCHOLOGY & MARKETING, Issue 7 2003
Blair Kidwell
We explore the dimensionality and structure of internal and external perceived behavioral control, extending research on the relationship between these control components. Two conceptual models were identified and tested in Study 1. External control was manipulated in Study 2 to further explicate hypothesized variation in perceived internal control. The results from both studies provide support for an antecedent relationship between control constructs with external control as an antecedent and internal control as the more proximate determinant of behavioral intent. Theoretical implications of findings are discussed. © 2003 Wiley Periodicals, Inc. [source]


Capuchin monkey tool use: Overview and implications

EVOLUTIONARY ANTHROPOLOGY, Issue 4 2008
Eduardo B. Ottoni
Abstract Nutcracking capuchins are mentioned in reports dating as far back as the sixteenth century,1, 2 as well as in Brazilian folklore.3 However, it was barely a decade ago that primatologists "discovered" the spontaneous use of stones to crack nuts in a semi-free ranging group of tufted capuchin monkeys. Since then, we have found several more capuchin populations in savanna-like environments which employ this form of tool use.5,7 The evidence so far only weakly supports genetically based behavioral differences between populations and does not suggest that dietary pressures in poor environments are proximate determinants of the likelihood of tool use. Instead, tool use within these capuchin populations seems to be a behavioral tradition that is socially learned and is primarily associated with more terrestrial habits. However, differences in the diversity of "tool kits" between populations remain to be understood. [source]


VARYING EFFECT OF FERTILITY DETERMINANTS AMONG MIGRANT AND INDIGENOUS FEMALES IN THE TRANSITIONAL AGRO-ECOLOGICAL ZONE OF GHANA

GEOGRAFISKA ANNALER SERIES B: HUMAN GEOGRAPHY, Issue 1 2007
Samuel Nii Ardey Codjoe
ABSTRACT. The transitional agro-ecological zone of Ghana, located between the richly endowed south and the impoverished north, has attracted seasonal and permanent farm migrants, mainly from northern Ghana, who now live side by side with the indigenous people. While migrants have higher numbers of Muslims, indigenous people are mainly Christians. Although the majority of the migrants live in migrant quarters with less favourable socio-economic conditions, they are more successful farmers and therefore wealthier. The objectives are to examine the varying effect of fertility determinants among migrants and indigenous females. This paper uses data collected in 2002 among 194 females aged 15 to 49 years. Multiple regression models are used to assess fertility determinants. Results show that although migrant households were wealthier, migrant females were more traditional. They had more children living in foster care, and a lower proportion of them approved of men participating in household activities. In addition, they were less well educated, recorded higher infant mortality, gave birth earlier and used less contraception. Furthermore, while a female's migration status is statistically significant so far as non-proximate determinants of fertility are concerned, the same variable is not significant with respect to proximate determinants. In addition, a married female migrant would on average have almost one more child compared to her indigenous counterpart, and migrant females who had experienced the loss of a child would on average have 2.5 more children compared to their indigenous counterparts. Finally, more affluent migrant females have 0.08 fewer children compared to their indigenous counterpart. [source]


Modeling the effects of health status and the educational infrastructure on the cognitive development of Tanzanian schoolchildren

AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 3 2005
Alok Bhargava
This paper models the proximate determinants of school attendance and scores on cognitive and educational achievement tests and on school examinations of over 600 schoolchildren from the Control group of a randomized trial in Tanzania, where children in the Intervention group heavily infected with hookworm and schistosomiasis received treatment. The modeling approach used a random effects framework and incorporated the inter-relationships between school attendance and performance on various tests, controlling for children's health status, socioeconomic variables, grade level, and the educational infrastructure. The empirical results showed the importance of variables such as children's height and hemoglobin concentration for the scores, especially on educational achievement tests that are easy to implement in developing countries. Also, teacher experience and work assignments were significant predictors of the scores on educational achievement tests, and there was some evidence of multiplicative effects of children's heights and work assignments on the test scores. Lastly, some comparisons were made for changes in test scores of treated children in the Intervention group with the untreated children in the Control group. Am. J. Hum. Biol. 17:280,292, 2005. © 2005 Wiley-Liss, Inc. [source]


Sex, Breastfeeding, and Marital Fertility in Pretransition China

POPULATION AND DEVELOPMENT REVIEW, Issue 2 2007
William Lavely
Coital frequency is at the heart of the debate over low marital fertility in pretransition China. This study argues that coital frequency in contemporary China is indicative of sexual behavior in an earlier era. Frequency of intercourse is low in China relative to Europe, a natural outgrowth of a traditional family system and related sexual culture only partially transformed by a century of family revolution. Customary sexual behaviors and breastfeeding practices together shaped the Chinese historical fertility regime as they did the European. As explanations for China's low marital fertility, these proximate determinants leave little scope for the operation of fecundity-reducing malnutrition on the one hand, or deliberate fertility control on the other. The fertility regimes of other pretransition agrarian societies more closely resemble China's than Europe's, seeming to confirm a pattern of European demographic exceptionalism. [source]


Body size variation in insects: a macroecological perspective

BIOLOGICAL REVIEWS, Issue 1 2010
Steven L. Chown
Body size is a key feature of organisms and varies continuously because of the effects of natural selection on the size-dependency of resource acquisition and mortality rates. This review provides a critical and synthetic overview of body size variation in insects from a predominantly macroecological (large-scale temporal and spatial) perspective. Because of the importance of understanding the proximate determinants of adult size, it commences with a brief summary of the physiological mechanisms underlying adult body size and its variation, based mostly on findings for the model species Drosophila melanogaster and Manduca sexta. Variation in nutrition and temperature have variable effects on critical weight, the interval to cessation of growth (or terminal growth period) and growth rates, so influencing final adult size. Ontogenetic and phylogenetic variation in size, compensatory growth, scaling at the intra- and interspecific levels, sexual size dimorphism, and body size optimisation are then reviewed in light of their influences on individual and species body size frequency distributions. Explicit attention is given to evolutionary trends, including gigantism, Cope's rule and the rates at which size change has taken place, and to temporal ecological trends such as variation in size with succession and size-selectivity during the invasion process. Large-scale spatial variation in size at the intraspecific, interspecific and assemblage levels is considered, with special attention being given to the mechanisms proposed to underlie clinal variation in adult body size. Finally, areas particularly in need of additional research are identified. [source]