http://webpages.icav.up.pt/PTDC/BIA-BEC/099934/2008/papers/Frankham_2005_Biological_Conservation.pdf

Genetics and extinction

All too often in evolutionary biology we are led to speculate or infer the mode of action of natural selection; we usually do not know why some individuals are more adaptive than others. Very often attempts to measure natural selection are unsuccessful, leading to heated arguments about' the relative importance of selection, genetic drift, and epistasis in evolution (Lewontin, 1974). Until we know more about how and why natural selection occurs, attempts to measure it are quixotic, and discussions of its importance are theandric. It is no coincidence that most of the successful studies of natural selection have dealt with animal color patterns; it should be obvious which color patterns are more adaptive in the presence of visually hunting predators. The adaptive significance of warning coloration and mimicry of distasteful species has been worked out (Cott, 1940; Wickler, 1968; Edmunds, 1974; Rothschild, 1975; Turner, 1977). But most species are neither distasteful nor mimetic; most have inconspicuous or cryptic color patterns in their natural habitats (Poulton, 1890; Thayer, 1909; Cott, 1940; Endler, 1978). Most field and experimental studies have shown that the overall color or tone of inconspicuous species matches or approximates the background (DiCesnola, 1904; Sumner, 1934, 1935; Isley, 1938; Popham, 1942; Dice, 1947; Kettlewell, 1956, 1973; Turner, 1961; Kaufman, 1974; Wicklund, 1975; Curio, 1976), but they treated species with solid colors or

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1558-5646.1980.tb04790.x

Natural selection on color patterns in poecilia reticulata.

Publisher Summary The chapter describes a simple economic model that predicts in a qualitative way on how costs (lost feeding opportunity and risk) interact to produce an optimal flight distance from approaching predators. Animals often defer the decision to flee from an approaching predator and continue with their ongoing activities. The view is that, a profitable approach to the problem of why such decisions are deferred, and how they are eventually made, is to view the process as an economic, one in which the relative costs of fleeing and staying change as a predator approaches. It is suggested that the economic approach will prove useful in analyzing many aspects of predator-prey interactions.

The Economics of Fleeing from Predators

It has long been known that the general colors and tones of animals tend to match their backgrounds (E. Darwin, 1794; Poulton, 1890). The adaptive significance of this has been borne out in numerous experimental studies (DiCesnola, 1904; Sumner, 1934, 1935; Isley, 1938; Popham, 1942; Dice, 1947; Turner, 1961; Kettlewell, 1956, 1973; Kaufman, 1974; Wiklund, 1975; Curio, 1976). There is also a good understanding of warning coloration (Cott, 1940; Wickler, 1968; Edmunds, 1974; Rothschild, 1975). However, the determinants of color pattern are poorly known, although it is known in a general way that the patterns and forms of animals are similar to their backgrounds (Poulton, 1890; Thayer, 1909; Cott, 1940; Wickler, 1968; Robinson, 1969; Edmunds, 1974; Fogden and Fogden, 1974). It is the purpose of this paper to explore the factors that determine color patterns under various specific conditions. The basic assumption is that a color pattern must resemble a random sample of the background seen by predators in order to be cryptic, and must deviate from the background in one or more ways in order to be conspicuous. As a result, the actual pattern evolved in a particular place represents a compromise between factors which favor crypsis and those which favor conspicuous color patterns.

A Predator’s View of Animal Color Patterns

We develop models of the rates of evolution at sex-linked and autosomal loci and of the rates of fixation of chromosomal rearrangements involving sex chromosomes and autosomes. We show that the substitution of selectively favorable mutations often proceeds more rapidly for X- or Y-linked loci than for the autosomes, provided that mutations are recessive or partially recessive on the average. Selection acting on a quantitative character is expected to result in similar long-term rates of gene substitution for X-linked and autosomal loci, unless there is strong directional dominance. Short-term responses to such selection often preferentially fix alleles at autosomal loci. The fixation of slightly deleterious alleles by random drift and the stochastic turnover of alleles at loci controlling quantitative characters under stabilizing selection usually proceed somewhat more slowly at sex-linked loci. In contrast, the fixation of underdominant chromosomal rearrangements by random genetic drift is faster with se...

The Relative Rates of Evolution of Sex Chromosomes and Autosomes

The Evolution of Melanism

The evolution of melanism: The study of a recurring necessity; with special reference to industrial melanism in the Lepidoptera

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The Evolution of Melanism

The evolution of melanism: The study of a recurring necessity; with special reference to industrial melanism in the Lepidoptera