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Main Predictions (main + prediction)
Selected AbstractsAge-related patterns of reproductive success in house sparrows Passer domesticusJOURNAL OF AVIAN BIOLOGY, Issue 5 2007Margret I. Hatch A common life history pattern in many organisms is that reproductive success increases with age. We report a similar pattern in house sparrows Passer domesticus, older individuals performed better than yearlings for most measures of reproductive success. Older males and females began breeding earlier in a given season and fledged more young than their yearling counterparts. Individual males also fledged more young in their second breeding season than they did in their first, but individual females did not show consistent improvement in reproductive success from year one to two. A path analysis indicated that age in both sexes acted primarily through the timing of breeding; earlier nesters laid more eggs and hence fledged more young but did not have more nesting attempts. We tested whether the increased reproductive success with age arose from high quality individuals surviving to be older (selection hypothesis). In contrast to the main prediction of this hypothesis that reproductive success and survival should be positively related, we found that survival from one year of age to two years of age was negatively related to reproductive success in the first year for males and females combined. Additionally, individuals that survived to breed as two-year-olds did not differ in total young fledged in their first year from those that did not survive to their second season of breeding. Our results indicate that fledgling production increases with age due to improvements in timing of breeding, particularly in females, and not because of the loss of poor breeders or increased output. Mechanisms producing age-related differences in timing of breeding warrant further study. [source] The Multipredator Hypothesis and the Evolutionary Persistence of Antipredator BehaviorETHOLOGY, Issue 3 2006Daniel T. Blumstein Invited Review Abstract Isolation from predators affects prey behavior, morphology, and life history, but there is tremendous variation in the time course of these responses. Previous hypotheses to explain this variation have limited predictive ability. I develop a ,multipredator' hypothesis to explain the evolutionary persistence of antipredator behavior after the loss of some, but not all, of a species' predators. The hypothesis assumes pleiotropy, whereby elements of antipredator behavior may function in non-predatory situations, and linkage, such that genes influencing the expression of antipredator behavior do not assort independently. The hypothesis is restricted to species with multiple predators (most species) and aims to predict the conditions under which antipredator behavior will persist following the loss of one or more of a species' predators. I acknowledge that the relative costs of non-functional antipredator behavior will influence the likelihood of linkage and therefore persistence. The hypothesis makes two main predictions. First, genes responsible for antipredator behavior will not be scattered throughout the genome but rather may be found close together on the same chromosome(s). Secondly, the presence of any predators may be sufficient to maintain antipredator behavior for missing predators. Advances in behavioral genetics will allow tests of the first prediction, while studies of geographic variation in antipredator behavior provide some support for the second. [source] Lobbying with conflicting interests: Norwegian local-central relationsEUROPEAN JOURNAL OF POLITICAL RESEARCH, Issue 2 2008LEIF HELLAND A total of 239 interactions are studied. Survey responses by a large number of voters and politicians, as well as registry data on fiscal standing, demographics and elections are utilised. Two of the main predictions of the costly lobbying model gain support in the data. The probability of obtaining substantial discretionary funding from the central level increases: with decreasing conflict of interest between local and central politicians; and with the lobbying cost incurred by local politicians. For a given conflict and cost, however, the rate of lobbying success depends crucially on structural characteristics of the municipality. In particular, the success rate is significantly higher for poor municipalities located in national electoral districts with many seats per voter than for rich municipalities located in districts with few seats per voter. [source] Microgeographic life history variation in an alpine caddisfly: plasticity in response to seasonal time constraintsFRESHWATER BIOLOGY, Issue 1 2009LISA N. S. SHAMA Summary 1.,Temporally constrained environments, such as habitats with short growth seasons or short hydroperiods, cause potentially strong selection on life histories. Depending on the predictability of these events and the extent of spatial and temporal heterogeneity, local populations could become adapted either via a fixed phenotype or via life history plasticity in response to these environmental cues. 2.,We used a common garden experiment to investigate microgeographic variation in life history responses to combined changes in photoperiod (ambient/late) and hydroperiod (constant/drying) time constraint cues in an alpine caddisfly (Trichoptera). We compared six populations (three permanent/three temporary streams) originating from a small, alpine floodplain and which spanned an expected gradient in growth period duration (GPD) with distance from glaciers. 3.,We made two main predictions in relation to locally varying selection pressures: (i) populations nearest glaciers (shorter GPD and strongest time constraints) should have the fastest development rates and (ii) populations from permanent streams should be less able to respond to drying hydroperiods than populations from temporary streams. 4.,All populations and both sexes accelerated development in response to late season photoperiod cues. However, only permanent stream populations showed an increase in development time with increasing GPD, suggesting that other factors were influencing populations in temporary streams. 5.,Permanent stream populations showed countergradient variation (genetic and environmental influences were in opposition) in development time, and under-compensation of growth rates resulted in a converse Bergmann cline in body size (smaller body size along gradients of declining season length). The extent of plasticity in response to hydroperiod, and the combined effects of both time constraints, differed between populations and sexes, but were not consistent among populations. 6.,Taken together, our results suggest adaptive plasticity in response to season length. The lack of a predictable pattern in response to hydroperiod may be due to gene flow or weak selection. We conclude that spatially structured populations can strongly differ in phenotypic plasticity even at microgeographic scales. [source] Retrograde amnesia and the volume of critical brain structuresHIPPOCAMPUS, Issue 8 2003M.D. Kopelman Abstract There are many controversies concerning the structural basis of retrograde amnesia (RA). One view is that memories are held briefly within a medial temporal store ("hippocampal complex") before being "consolidated" or reorganised within temporal neocortex and/or networks more widely distributed within the cerebral cortex. An alternative view is that the medial temporal lobes are always involved in the storage and retrieval (reactivation) of autobiographical memories (multiple trace theory). The present study used quantitative magnetic resonance imaging (MRI) in 40 patients with focal pathology/volume loss in different sites, to examine the correlates of impairment on three different measures of RA. The findings supported the view that widespread neural networks are involved in the storage and retrieval of autobiographical and other remote memories. Brain volume measures in critical structures could account for 60% of variance on autobiographical memory measures (for incidents and facts) in diencephalic patients and for 60,68% of variance in patients with frontal lesions. Significant correlations with medial temporal lobe volume were found only in the diencephalic group, in whom they were thought to reflect thalamic changes, but not in patients with herpes encephalitis or hypoxia in whom the temporal lobes were particularly implicated. The latter finding fails to support one of the main predictions of multiple trace theory, as presently expounded. © 2003 Wiley-Liss, Inc. [source] RELATIONAL GOODS, MONITORING AND NON-PECUNIARY COMPENSATIONS IN THE NONPROFIT SECTOR: THE CASE OF THE ITALIAN SOCIAL SERVICESANNALS OF PUBLIC AND COOPERATIVE ECONOMICS, Issue 1 2007Michele Mosca ABSTRACT,:,This paper investigates the nonprofit wage gap suggesting a theoretical framework where, like inAkerlof (1984), effort correlates not only with wages, but also with non-monetary compensations. These take the form of relational goods by-produced in the delivery of particular services. By paying higher non-pecuniary compensations, the nonprofit sector attracts intrinsically similarly skilled, but more motivated workers, able to provide in fact a similar (or potentially higher) level of effort than their counterparts in the forprofit sector. On an empirical ground, the paper provides a number of econometric tests that confirm the main predictions of the model in Italy's case. It adds to the available empirical literature by introducing in the analysis direct measures of non-pecuniary compensations and job satisfaction. [source] Control of Cell Volume in Skeletal MuscleBIOLOGICAL REVIEWS, Issue 1 2009Juliet A. Usher-Smith Abstract Regulation of cell volume is a fundamental property of all animal cells and is of particular importance in skeletal muscle where exercise is associated with a wide range of cellular changes that would be expected to influence cell volume. These complex electrical, metabolic and osmotic changes, however, make rigorous study of the consequences of individual factors on muscle volume difficult despite their likely importance during exercise. Recent charge-difference modelling of cell volume distinguishes three major aspects to processes underlying cell volume control: (i) determination by intracellular impermeant solute; (ii) maintenance by metabolically dependent processes directly balancing passive solute and water fluxes that would otherwise cause cell swelling under the influence of intracellular membrane-impermeant solutes; and (iii) volume regulation often involving reversible short-term transmembrane solute transport processes correcting cell volumes towards their normal baselines in response to imposed discrete perturbations. This review covers, in turn, the main predictions from such quantitative analysis and the experimental consequences of comparable alterations in extracellular pH, lactate concentration, membrane potential and extracellular tonicity. The effects of such alterations in the extracellular environment in resting amphibian muscles are then used to reproduce the intracellular changes that occur in each case in exercising muscle. The relative contributions of these various factors to the control of cell volume in resting and exercising skeletal muscle are thus described. [source] | ||||||||||