scholarly journals Multimodal pattern formation in phenotype distributions of sexual populations

2006 ◽  
Vol 274 (1608) ◽  
pp. 347-357 ◽  
Author(s):  
Michael Doebeli ◽  
Hendrik J Blok ◽  
Olof Leimar ◽  
Ulf Dieckmann
Keyword(s):  
Pattern Formation ◽  
Assortative Mating ◽  
Quantitative Genetics ◽  
Adaptive Dynamics ◽  
Potential Mechanism ◽  
Frequency Dependent ◽  
Evolutionary Diversification ◽  
Species Cluster ◽  
Adaptive Radiations ◽  
Phenotype Space

During bouts of evolutionary diversification, such as adaptive radiations, the emerging species cluster around different locations in phenotype space. How such multimodal patterns in phenotype space can emerge from a single ancestral species is a fundamental question in biology. Frequency-dependent competition is one potential mechanism for such pattern formation, as has previously been shown in models based on the theory of adaptive dynamics. Here, we demonstrate that also in models similar to those used in quantitative genetics, phenotype distributions can split into multiple modes under the force of frequency-dependent competition. In sexual populations, this requires assortative mating, and we show that the multimodal splitting of initially unimodal distributions occurs over a range of assortment parameters. In addition, assortative mating can be favoured evolutionarily even if it incurs costs, because it provides a means of alleviating the effects of frequency dependence. Our results reveal that models at both ends of the spectrum between essentially monomorphic (adaptive dynamics) and fully polymorphic (quantitative genetics) yield similar results. This underscores that frequency-dependent selection is a strong agent of pattern formation in phenotype distributions, potentially resulting in adaptive speciation.

Adaptive Diversification and Speciation as Pattern Formation in Partial Differential Equation Models

2011 ◽  
Author(s):  
Michael Doebeli
Keyword(s):  
Differential Equation ◽  
Partial Differential Equation ◽  
Partial Differential Equations ◽  
Pattern Formation ◽  
Differential Equations ◽  
Adaptive Dynamics ◽  
Partial Differential ◽  
Adaptive Diversification ◽  
Differential Equation Models ◽  
Phenotype Distribution

This chapter discusses partial differential equation models. Partial differential equations can describe the dynamics of phenotype distributions of polymorphic populations, and they allow for a mathematically concise formulation from which some analytical insights can be obtained. It has been argued that because partial differential equations can describe polymorphic populations, results from such models are fundamentally different from those obtained using adaptive dynamics. In partial differential equation models, diversification manifests itself as pattern formation in phenotype distribution. More precisely, diversification occurs when phenotype distributions become multimodal, with the different modes corresponding to phenotypic clusters, or to species in sexual models. Such pattern formation occurs in partial differential equation models for competitive as well as for predator–prey interactions.

scholarly journals Acoustic discrimination of sympatric morphs in Darwin's finches: a behavioural mechanism for assortative mating?

2010 ◽  
Vol 365 (1543) ◽  
pp. 1031-1039 ◽  
Author(s):  
Jeffrey Podos
Keyword(s):  
Assortative Mating ◽  
Disruptive Selection ◽  
Evolutionary Divergence ◽  
Santa Cruz Island ◽  
Evolutionary Diversification ◽  
Acoustic Discrimination ◽  
Behavioural Types ◽  
Geospiza Fortis ◽  
Beak Size ◽  
Behavioural Mechanism

Populations with multiple morphological or behavioural types provide unique opportunities for studying the causes and consequences of evolutionary diversification. A population of the medium ground finch ( Geospiza fortis ) at El Garrapatero on Santa Cruz Island, Galápagos, features two beak size morphs. These morphs produce acoustically distinctive songs, are subject to disruptive selection and mate assortatively by morph. The main goal of the present study was to assess whether finches from this population are able to use song as a cue for morph discrimination. A secondary goal of this study was to evaluate whether birds from this population discriminate songs of their own locality versus another St Cruz locality, Borrero Bay, approximately 24 km to the NW. I presented territorial males with playback of songs of their own morph, of the other morph, and of males from Borrero Bay. Males responded more strongly to same-morph than to other-morph playbacks, showing significantly shorter latencies to flight, higher flight rates and closer approaches to the playback speaker. By contrast, I found only minor effects of locality on responsiveness. Evidence for morph discrimination via acoustic cues supports the hypothesis that song can serve as a behavioural mechanism for assortative mating and sympatric evolutionary divergence.

scholarly journals Sympatric Speciation in Threespine Stickleback: Why Not?

2011 ◽  
Vol 2011 ◽  
pp. 1-15 ◽  
Author(s):  
Daniel I. Bolnick
Keyword(s):  
Sexual Dimorphism ◽  
Assortative Mating ◽  
Intraspecific Competition ◽  
Gasterosteus Aculeatus ◽  
Theoretical Models ◽  
Sympatric Speciation ◽  
Threespine Stickleback ◽  
Disruptive Selection ◽  
Evolutionary Diversification ◽  
Trait Variance

Numerous theoretical models suggest that sympatric speciation is possible when frequency-dependent interactions such as intraspecific competition drive disruptive selection on a trait that is also subject to assortative mating. Here, I review recent evidence that both conditions are met in lake populations of threespine stickleback (Gasterosteus aculeatus). Nonetheless, sympatric speciation appears to be rare or absent in stickleback. If stickleback qualitatively fit the theoretical requirements for sympatric speciation, why do they not undergo sympatric speciation? I present simulations showing that disruptive selection and assortative mating in stickleback, though present, are too weak to drive speciation. Furthermore, I summarize empirical evidence that disruptive selection in stickleback drives other forms of evolutionary diversification (plasticity, increased trait variance, and sexual dimorphism) instead of speciation. In conclusion, core assumptions of sympatric speciation theory seem to be qualitatively reasonable for stickleback, but speciation may nevertheless fail because of (i) quantitative mismatches with theory and (ii) alternative evolutionary outcomes.

scholarly journals Can sexual selection and disassortative mating contribute to the maintenance of a shell color polymorphism in an intertidal marine snail?

2012 ◽  
Vol 58 (3) ◽  
pp. 463-474 ◽  
Author(s):  
Emilio Rolán-Alvarez ◽  
María Saura ◽  
Angel P. Diz ◽  
María José Rivas ◽  
Marga Alvarez ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Assortative Mating ◽  
Environmental Variable ◽  
Color Variation ◽  
Main Hypothesis ◽  
Shell Color ◽  
Frequency Dependent ◽  
Color Preferences ◽  
In The Wild ◽  
New Evidence

Abstract Littorina fabalis is an intertidal snail commonly living on the brown algae Fucus vesiculosus and showing frequent shell-color polymorphisms in the wild. The evolutionary mechanism underlying this polymorphism is currently unknown. Shell color variation was studied in mated and non-mated specimens of this species from different microareas in one locality from NW Spain, in order to estimate sexual selection and assortative mating that may (still) be operating in this population. The analyses across microareas allowed us to investigate frequency-dependent selection and assortative mating components, mechanisms that could maintain the polymorphism. The presence of shell scars caused by crab attacks, an environmental variable not related with sexual selection or assortative mating, was used as experimental control. This study provides new evidence of significant disas-sortative mating and some degree of sexual selection against some shell colors, supporting the results found 21 years ago in a similar study, i.e. in the same species and locality. The similarity of these estimates during the studied period suggests that this experimental approach is consistent and valid to be extended to other populations and organisms. In addition, sexual selection and assortative mating estimates did not change across microareas differing in shell color frequencies, suggesting than the polymorphism can not be maintained by a frequency-dependent (sexual selection-based) mechanism. Our main hypothesis is that negative assortative mating could contribute to the maintenance of the polymorphism, perhaps by males showing distinct female color preferences when searching for mates.

scholarly journals Possible human impacts on adaptive radiation: beak size bimodality in Darwin's finches

2006 ◽  
Vol 273 (1596) ◽  
pp. 1887-1894 ◽  
Author(s):  
Andrew P Hendry ◽  
Peter R Grant ◽  
B Rosemary Grant ◽  
Hugh A Ford ◽  
Mark J Brewer ◽  
...  
Keyword(s):  
Adaptive Radiation ◽  
Human Activities ◽  
Human Impacts ◽  
Adaptive Landscape ◽  
Hybrid Fitness ◽  
Evolutionary Diversification ◽  
Adaptive Landscapes ◽  
Adaptive Radiations ◽  
Geospiza Fortis ◽  
Beak Size

Adaptive radiation is facilitated by a rugged adaptive landscape, where fitness peaks correspond to trait values that enhance the use of distinct resources. Different species are thought to occupy the different peaks, with hybrids falling into low-fitness valleys between them. We hypothesize that human activities can smooth adaptive landscapes, increase hybrid fitness and hamper evolutionary diversification. We investigated this possibility by analysing beak size data for 1755 Geospiza fortis measured between 1964 and 2005 on the island of Santa Cruz, Galápagos. Some populations of this species can display a resource-based bimodality in beak size, which mirrors the greater beak size differences among species. We first show that an historically bimodal population at one site, Academy Bay, has lost this property in concert with a marked increase in local human population density. We next show that a nearby site with lower human impacts, El Garrapatero, currently manifests strong bimodality. This comparison suggests that bimodality can persist when human densities are low (Academy Bay in the past, El Garrapatero in the present), but not when they are high (Academy Bay in the present). Human activities may negatively impact diversification in ‘young’ adaptive radiations, perhaps by altering adaptive landscapes.

scholarly journals Coffee Berry Borer (Hypothenemus hampei) and its role in the evolutionary diversification of the coffee market

2021 ◽  
Author(s):  
Hernán Darío Toro-Zapata ◽  
Carlos Andrés Trujillo-Salazar ◽  
Fabio Dercole ◽  
Gerard Olivar-Tost
Keyword(s):  
Ecological Model ◽  
Adaptive Dynamics ◽  
Market Competition ◽  
Market Model ◽  
Economic Losses ◽  
Coffee Berry ◽  
Coffee Berry Borer ◽  
Evolutionary Diversification ◽  
The Impact ◽  
Strong Control

AbstractThe Coffee Berry Borer (CBB) is the main pest that affects coffee crops around the world, causing major economic losses and diminishing beverage quality. A mathematical model is formulated, from the perspective of the Adaptive Dynamics (AD) framework, to describe the evolution of coffee quality as a continuous differentiating attribute related to the mix of healthy and bored coffee. The study involves three stages: first, an agro-ecological model describes coffee production and growth of the CBB population prior to the processing of different qualities of coffee; second, a market model describes the competition between different blends of standard and special coffee; finally, the AD canonical equation is derived to describe the evolution of coffee quality resulting from innovations in the quality attribute filtered by market competition. Interestingly, AD allows to derive conditions for the emergence of diversity, i.e., the establishment of a second type of coffee that coexists with the former and, similarly, for subsequent branching in the quality attributes. The full model provides insights on the impact of CBB control strategies on the long-term market structure. Specifically, a strong control aimed at increasing coffee quality may impoverish the market diversity, independently of the consumers’ budget limitations and corresponding preference for either high or low quality.

scholarly journals What constrains adaptive radiation? Documentation and explanation of under-evolved morphologies in Anolis lizards

2021 ◽  
Vol 288 (1953) ◽  
pp. 20210340
Author(s):  
Steven Poe ◽  
Lorenzo A. H. Donald ◽  
Christopher Anderson
Keyword(s):  
Body Length ◽  
Adaptive Radiation ◽  
Tail Length ◽  
Evolutionary Diversification ◽  
Selective Forces ◽  
Adaptive Radiations

Adaptive radiations fill ecological and morphological space during evolutionary diversification. Why do some trait combinations evolve during such radiations, whereas others do not? ‘Required’ constraints of pleiotropy and developmental interaction frequently are implicated in explanations for such patterns, but selective forces also may discourage particular trait combinations. Here, we use a dataset of 351 species to demonstrate the dearth of some theoretically plausible trait combinations of limb, toe and tail length in Anolis lizards. For example, disproportionately few Anolis species display long limbs and short toes. We evaluate recovered patterns within three species of Anolis , and find that cladewide patterns are not evident at intraspecific levels. For example, within species, the combination of long limbs and short toes is not significantly rarer than long limbs and long toes. Differences in scale complicate inter- and intraspecific comparisons and disallow concrete conclusions of cause. However, the absence of the interspecific pattern at the intraspecific level is more compatible with selection favouring particular trait combinations than with ‘required’ forces dictating which trait combinations are available for selection. We also demonstrate the isometry of toe, tail and hindlimb length relative to body length between species but allometry in four of nine trait–body comparisons within species.

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