▪ Abstract Mimicry and warning color are highly paradoxical adaptations. Color patterns in both Mullerian and Batesian mimicry are often determined by relatively few pattern-regulating loci with major effects. Many of these loci are “supergenes,” consisting of multiple, tightly linked epistatic elements. On the one hand, strong purifying selection on these genes must explain accurate resemblance (a reduction of morphological diversity between species), as well as monomorphic color patterns within species. On the other hand, mimicry has diversified at every taxonomic level; warning color has evolved from cryptic patterns, and there are mimetic polymorphisms within species, multiple color patterns in different geographic races of the same species, mimetic differences between sister species, and multiple mimicry rings within local communities. These contrasting patterns can be explained, in part, by the shape of a “number-dependent” selection function first modeled by Fritz Muller in 1879: Purifying selectio...

Animal species and evolution

Evolution of Diversity in Warning Color and Mimicry: Polymorphisms, Shifting Balance, and Speciation

Differentiation of Populations: Gene flow seems to be less important in speciation than the neo-Darwinians thought.

Ernst Mayr has argued that Darwinian theory discredited essentialist modes of thought and replaced them with what he has called "population thinking". In this paper, I characterize essentialism as embodying a certain conception of how variation in nature is to be explained, and show how this conception was undermined by evolutionary theory. The Darwinian doctrine of evolutionary gradualism makes it impossible to say exactly where one species ends and another begins; such line-drawing problems are often taken to be the decisive reason for thinking that essentialism is untenable. However, according to the view of essentialism I suggest, this familiar objection is not fatal to essentialism. It is rather the essentialist's use of what I call the natural state model for explaining variation which clashes with evolutionary theory. This model implemented the essentialist's requirement that properties of populations be defined in terms of properties of member organisms. Requiring such constituent definitions is r...

Evolution population thinking and essentialism.

Asexual organisms that are descended from ancient asexual lineages defy current thinking on the evolution of sexual reproduction; theoreticians have been anxious to explain away their existence. However, a number of groups of organisms, from ferns to rotifers, have been suggested to be anciently asexual, and favourable evidence is being accumulated. Furthermore, new techniques for assessing claims of ancient asexuality have been proposed. Although ancient asexuals challenge current theories of sex, understanding how they manage to persist will help to explain why most organisms are sexual.

Ancient asexual scandals

Evolutionary branching occurs when frequency-depen- dent selection splits a phenotypically monomorphic population into two distinct phenotypic clusters. A prerequisite for evolutionary branching is that directional selection drives the population toward a fitness minimum in phenotype space. This article demonstrates that selection regimes leading to evolutionary branching readily arise from a wide variety of different ecological interactions within and between species. We use classical ecological models for symmetric and asymmetric competition, for mutualism, and for predator-prey interactions to describe evolving populations with continuously vary- ing characters. For these models, we investigate the ecological and evolutionary conditions that allow for evolutionary branching and establish that branching is a generic and robust phenomenon. Evo- lutionary branching becomes a model for sympatric speciation when population genetics and mating mechanisms are incorporated into ecological models. In sexual populations with random mating, the continual production of intermediate phenotypes from two incipient branches prevents evolutionary branching. In contrast, when mating is assortative for the ecological characters under study, evolutionary branching is possible in sexual populations and can lead to speciation. Therefore, we also study the evolution of assortative mating as a quantitative character. We show that evolution under branching con- ditions selects for assortativeness and thus allows sexual populations to escape from fitness minima. We conclude that evolutionary branching offers a general basis for understanding adaptive speciation and radiation under a wide range of different ecological conditions.

https://user.iiasa.ac.at/~dieckman/reprints/DoebeliDieckmann2000.pdf

Animal species and evolution

Citations

Evolution of Diversity in Warning Color and Mimicry: Polymorphisms, Shifting Balance, and Speciation

Differentiation of Populations: Gene flow seems to be less important in speciation than the neo-Darwinians thought.

Evolution population thinking and essentialism.

Ancient asexual scandals

Evolutionary Branching and Sympatric Speciation Caused by Different Types of Ecological Interactions.

Related Papers (5)

Systematics and the Origin of Species

Genetics and the Origin of Species

The Genetical Theory of Natural Selection

Evolution in Mendelian Populations.

On the Origin of Species by Means of Natural Selection, or, The Preservation of Favoured Races in the Struggle for Life