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J G Kingsolver

Publications and source records attributed to J G Kingsolver.

6 recordsLinked to original sources
PubMed2001

Strength and tempo of directional selection in the wild.

Directional selection is a major force driving adaptation and evolutionary change. However, the distribution, strength, and tempo of phenotypic selection acting on quantitative traits in natural populations remain unclear across different study systems. We reviewed the literature (1984-1997) that reported the strength of directional selection as indexed by standardized linear selection gradients (beta). We asked how strong are viability and sexual selection, and whether strength of selection is correlated with the time scale over which it was measured. Estimates of the magnitude of directional selection (absolute value of beta) were exponentially distributed, with few estimates greater than 0.50 and most estimates less than 0.15. Sexual selection (measured by mating success) appeared stronger than viability selection (measured by survival). Viability selection that was measured over short periods (days) was typically stronger than selection measured over longer periods (months and years), but the strength of sexual selection did not vary with duration of selection episodes; as a result, sexual selection was stronger than viability selection over longer time scales (months and years), but not over short time scales (days).

Animals↗
PubMed2001

Variation, selection and evolution of function-valued traits.

We describe an emerging framework for understanding variation, selection and evolution of phenotypic traits that are mathematical functions. We use one specific empirical example--thermal performance curves (TPCs) for growth rates of caterpillars - to demonstrate how models for function-valued traits are natural extensions of more familiar, multivariate models for correlated, quantitative traits. We emphasize three main points. First, because function-valued traits are continuous functions, there are important constraints on their patterns of variation that are not captured by multivariate models. Phenotypic and genetic variation in function-valued traits can be quantified in terms of variance-covariance functions and their associated eigenfunctions: we illustrate how these are estimated as well as their biological interpretations for TPCs. Second, selection on a function-valued trait is itself a function, defined in terms of selection gradient functions. For TPCs, the selection gradient describes how the relationship between an organism's performance and its fitness varies as a function of its temperature. We show how the form of the selection gradient function for TPCs relates to the frequency distribution of environmental states (caterpillar temperatures) during selection. Third, we can predict evolutionary responses of function-valued traits in terms of the genetic variance-covariance and the selection gradient functions. We illustrate how non-linear evolutionary responses of TPCs may occur even when the mean phenotype and the selection gradient are themselves linear functions of temperature. Finally, we discuss some of the methodological and empirical challenges for future studies of the evolution of function-valued traits.

Animals↗
PubMed1983

Feeding strategy and the mechanics of blood sucking in insects.

As a means of exploring foraging strategies of blood-feeding insects, we studied the mechanics of blood feeding. We develop a mechanistic model for the dynamics of non-Newtonian fluid flow to describe the feeding process for blood feeders. Using available feeding and morphological data, we examine the relationship of feeding time to proboscis design, and consider optimal foraging strategies for blood feeders. Because of the flow rates typical of many blood feeders, the non-Newtonian nature of blood is of little importance for flow dynamics. Observed feeding times and flow rates do not necessarily reflect the energy requirements for feeding. The radius of the food canal is the major morphological determinant of flow dynamics. Feeding time is a monotonically increasing function of blood hematocrit. There is an optimal blood hematocrit of 0.3 which maximizes the rate of total protein intake for blood feeders, regardless of the energy output or proboscis design. This hematocrit level is typical of humans with blood parasite infections. In contrast, the rate of red blood cell intake is maximized at a hematocrit of 0.4. We argue that the existence of such optima may be a general consequence of the mechanics of feeding on nutrients dissolved or suspended in a fluid medium. Results are discussed in relation to foraging strategy, proboscis design, and the coevolution among host, vector, and parasite in blood feeding insects.

Aedes↗
PubMedDate not supplied

Feeding, growth, and the thermal environment of cabbage white caterpillars, Pieris rapae L.

Laboratory studies of temperature effects on short-term feeding and growth rates were combined with field data on thermal environments to explore the consequences of temperature variation for growth of caterpillars of the cabbage white butterfly, Pieris rapae. Mean short-term (24-h) consumption and growth rates of fourth-instar P. rapae feeding on collard leaves increased continuously with increasing temperatures between 10 degrees and 35 degrees C, peaked at 35 degrees C, and declined rapidly with temperatures above 35 degrees C. Physical models can mimic temperatures of real fifth-instar caterpillars under collard leaves within 1 degrees -2 degrees C in sunny summer conditions in Seattle, Washington. Continuous recordings of operative temperatures of model caterpillars in a collard garden suggest that, at the timescale of the duration of the fifth instar (5-8 d in the field), P. rapae caterpillars frequently experience temperatures spanning a 25 degrees C range, they spend most of their time at temperatures well below those that maximize growth, and they encounter substantial variation in the frequency distribution of operative temperatures between time periods. Combining these data on growth rate as a function of temperature and the distribution of operative temperatures in the field, I illustrate how growth rates at higher temperatures can make disproportionate contributions to the overall mean growth rates even when higher temperatures are relatively infrequent. Fluctuating thermal conditions may generate variable patterns of selection on reaction norms for growth rate in the field.

Adaptation, Physiological↗
PubMedDate not supplied

Thermal sensitivity of growth and feeding in Manduca sexta caterpillars.

We explore how the thermal sensitivity of organismic performance emerges from the thermal sensitivity of the underlying component processes involved, using growth and feeding of Manduca sexta caterpillars as a model system. We measured thermal performance curves for the short-term rates of growth, consumption, protein (casein) digestion, amino acid (methionine) uptake, and respiration in fifth-instar caterpillars over a biologically realistic temperature range from 14 degrees to 42 degrees C. Growth and consumption rates increased between 14 degrees and 26 degrees C, reached a maximum value near 34 degrees C, and declined rapidly above 38 degrees C. In contrast, protein digestion rate and respiration rate increased monotonically over the entire temperature range, and amino acid uptake rate increased with temperatures up to 38 degrees C and then leveled off between 38 degrees and 42 degrees C. These results suggest that the shape and position of the thermal performance curve for growth rate--in particular the maximum at 34 degrees C and rapid decline above 38 degrees C--was most closely correlated with the thermal sensitivity of consumption rate; the declining growth performance above 38 degrees C was not associated with declines in digestion or uptake rates or with accelerated respiration rates at these temperatures.

Animals↗