Experimental evolution: Assortative mating and sexual selection, independent of local adaptation, lead to reproductive isolation in the nematodeCaenorhabditis remanei

Evolution ◽  
2015 ◽  
Vol 69 (12) ◽  
pp. 3141-3155 ◽  
Author(s):  
Dean M. Castillo ◽  
Melissa K. Burger ◽  
Curtis M. Lively ◽  
Lynda F. Delph
2012 ◽  
Vol 58 (3) ◽  
pp. 475-483 ◽  
Author(s):  
Michael J. Pauers ◽  
Jeffrey S. Mckinnon

Abstract Sexual selection is widely viewed as playing a central role in haplochromine cichlid speciation. Hypothetically, once divergent mate preferences evolve among populations of these fishes, reproductive isolation follows and the populations begin to behave as different species. Various studies have examined patterns of assortative mating among species and sometimes populations, but few have examined variation in directional preferences, especially among populations of the same species. We investigated mate choice behavior in two populations of Labeotropheus fuelleborni, a Lake Malawi endemic. We test whether mating preferences between populations are based on the same traits and in the same direction as preferences within populations. We examine the potential contributions of two classes of trait, color patterns and behaviors, to reproductive isolation. When females chose between either two males of their own population, or two from another, female preferences were generally similar (for the female population) across the two contexts. Mate choice patterns differed between (female) populations for a measure of color, but only modestly for male behavior. In a separate experiment we simultaneously offered females a male of their own population and a male from a different population. In these trials, females consistently preferred males from their own population, which were also the males that displayed more frequently than their opponents, but not necessarily those with color traits suggested to be most attractive in the previous experiment. Thus directional preferences for chroma and related aspects of color may be important when females are presented with males of otherwise similar phenotypes, but may play little role in mediating assortative mating among populations with substantially different color patterns. A preference for male behavior could play some role in speciation if males preferentially court same-population females, as we have observed for the populations studied herein.


1985 ◽  
Vol 27 (4) ◽  
pp. 405-409 ◽  
Author(s):  
Bashisth N. Singh ◽  
Sujata Chatterjee

Male-choice experiments using five isofemale lines of Drosophila ananassae originating from different localities were performed to study sexual isolation within the species. In most of the crosses homogamic matings outnumber heterogamic ones, and deviation from randomness is statistically significant in 11 of 20 crosses. This provides evidence for positive assortative mating within D. ananassae. Isolation indices range from −0.057 to 0.555. Eleven positive isolation indices are significantly greater than zero. Both types of sexual isolation, symmetrical and asymmetrical, have been observed among different strains. Thus the present results clearly indicate that the laboratory strains of D. ananassae have developed behavioural reproductive isolation as a result of genetic divergence.Key words: Drosophila, assortive mating, sexual selection, behaviour.


2018 ◽  
Author(s):  
Yann XC Bourgeois ◽  
Joris AM Bertrand ◽  
Boris Delahaie ◽  
Hélène Holota ◽  
Christophe Thébaud ◽  
...  

AbstractRecently diverged taxa showing marked phenotypic and ecological diversity are optimal systems to test the relative importance of two major evolutionary mechanisms, adaptation to local ecological conditions by natural selection, or mechanisms of reproductive isolation such as assortative mating mediated by sexually selected mating signals or post-zygotic incompatibilities. Whereas local adaptation is expected to affect many loci throughout the genome, traits acting as mating signals are expected to be located on sex chromosomes and have a simple genetic basis. We used genome-wide markers to test these predictions in Reunion Island’s gray-white eye (Zosterops borbonicus), which has recently diversified into five distinct plumage forms. Two of them correspond to a polymorphic highland population that is separated by a steep ecological gradient from three distinct lowland forms that show narrow contact zones in plumage color traits, yet no association with environmental variables. An analysis of population structure using genome-wide SNP loci revealed two major clades corresponding to highland and lowland forms, respectively, with the latter separated further into three independent lineages corresponding to plumage forms. Coalescent tests of alternative demographic scenarios provided support for divergence of highland and lowland lineages with an intensification of gene flow in the last 60,000 years. Landscapes of genomic variation revealed that signatures of selection associated with elevation are found at multiple regions across the genome, whereas most loci associated with the lowland forms are located on the Z sex chromosome. A gene ontology analysis identified TYRP1, a Z-linked color gene, as a likely candidate locus underlying color variation among lowland forms. Our results are consistent with the role of natural selection in driving the divergence of locally adapted highland populations, and the role of sexual selection in differentiating lowland forms through reproductive isolation mechanisms, showing that both modes of lineage divergence can take place at very small geographic scales in birds.


2020 ◽  
Author(s):  
Samuel Perini ◽  
Marina Rafajlović ◽  
Anja M. Westram ◽  
Kerstin Johannesson ◽  
Roger K. Butlin

AbstractWhen divergent populations are connected by gene flow, the establishment of complete reproductive isolation usually requires the joint action of multiple barrier effects. One example where multiple barrier effects are coupled consists of a single trait that is under divergent natural selection and also mediates assortative mating. Such multiple-effect traits can strongly reduce gene flow. However, there are few cases where patterns of assortative mating have been described quantitatively and their impact on gene flow has been determined. Two ecotypes of the coastal marine snail, Littorina saxatilis, occur in North Atlantic rocky-shore habitats dominated by either crab predation or wave action. There is evidence for divergent natural selection acting on size, and size-assortative mating has previously been documented. Here, we analyze the mating pattern in L. saxatilis with respect to size in intensively-sampled transects across boundaries between the habitats. We show that the mating pattern is mostly conserved between ecotypes and that it generates both assortment and directional sexual selection for small male size. Using simulations, we show that the mating pattern can contribute to reproductive isolation between ecotypes but the barrier to gene flow is likely strengthened more by sexual selection than by assortment.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kensuke Okada ◽  
Masako Katsuki ◽  
Manmohan D. Sharma ◽  
Katsuya Kiyose ◽  
Tomokazu Seko ◽  
...  

AbstractTheory shows how sexual selection can exaggerate male traits beyond naturally selected optima and also how natural selection can ultimately halt trait elaboration. Empirical evidence supports this theory, but to our knowledge, there have been no experimental evolution studies directly testing this logic, and little examination of possible associated effects on female fitness. Here we use experimental evolution of replicate populations of broad-horned flour beetles to test for effects of sex-specific predation on an exaggerated sexually selected male trait (the mandibles), while also testing for effects on female lifetime reproductive success. We find that populations subjected to male-specific predation evolve smaller sexually selected mandibles and this indirectly increases female fitness, seemingly through intersexual genetic correlations we document. Predation solely on females has no effects. Our findings support fundamental theory, but also reveal unforseen outcomes—the indirect effect on females—when natural selection targets sex-limited sexually selected characters.


2021 ◽  
Author(s):  
Nathan J. White ◽  
Andrew P. Beckerman ◽  
Rhonda R. Snook ◽  
Michael A. Brockhurst ◽  
Roger K. Butlin ◽  
...  

2021 ◽  
Author(s):  
Masaomi Kurokawa ◽  
Issei Nishimura ◽  
Bei-Wen YING

As a central issue in evolution and ecology, the quantitative relationship among the genome, adaptation and the niche was investigated. Local adaptation of five Escherichia coli strains carrying either the wild-type genome or reduced genomes was achieved by experimental evolution. A high-throughput fitness assay of the ancestor and evolved populations across an environmental gradient of eight niches resulted in a total of 80 fitness curves generated from 2,220 growth curves. Further analyses showed that the increases in both local adaptiveness and niche broadness were negatively correlated with genetic richness. Local adaptation caused common niche expansion, whereas niche expansion for generality or speciality was decided by genetic richness. The order of the mutations accumulated stepwise was correlated with the magnitude of the fitness increase attributed to mutation accumulation. Pre-adaptation probably participated in coordination among genetic richness, local adaptation and niche expansion.


2020 ◽  
Vol 35 (3) ◽  
pp. 220-234 ◽  
Author(s):  
Melissah Rowe ◽  
Liisa Veerus ◽  
Pål Trosvik ◽  
Angus Buckling ◽  
Tommaso Pizzari

2020 ◽  
Vol 375 (1806) ◽  
pp. 20190532 ◽  
Author(s):  
Alexandre Blanckaert ◽  
Claudia Bank ◽  
Joachim Hermisson

Gene flow tends to impede the accumulation of genetic divergence. Here, we determine the limits for the evolution of postzygotic reproductive isolation in a model of two populations that are connected by gene flow. We consider two selective mechanisms for the creation and maintenance of a genetic barrier: local adaptation leads to divergence among incipient species due to selection against migrants, and Dobzhansky–Muller incompatibilities (DMIs) reinforce the genetic barrier through selection against hybrids. In particular, we are interested in the maximum strength of the barrier under a limited amount of local adaptation, a challenge that many incipient species may initially face. We first confirm that with classical two-locus DMIs, the maximum amount of local adaptation is indeed a limit to the strength of a genetic barrier. However, with three or more loci and cryptic epistasis, this limit holds no longer. In particular, we identify a minimal configuration of three epistatically interacting mutations that is sufficient to confer strong reproductive isolation. This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers’.


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