Reproductive isolation as a pleiotropic effect of copper tolerance in Mimulus guttatus?

Macnair, Mark R.; Christie, Paul T.

doi:10.1038/hdy.1983.31

Cited by 141 publications

(132 citation statements)

References 19 publications

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“…4). A similar mechanism, involving phenotypic divergence in response to divergent edaphic selection and associated flowering time divergence, perhaps as a pleiotropic by-product, has been proposed for species occupying heavy metal contaminated mine tailings (McNeilly and Antonovics 1968) and for serpentine endemics (Macnair and Christie 1983;Macnair and Gardner 1998).…”

Section: Mechanisms Of Evolutionary Divergence In Argyrodermamentioning

confidence: 99%

Evolutionary Radiation of "Stone Plants" in the Genus Argyroderma (Aizoaceae): Unraveling the Effects of Landscape, Habitat, and Flowering Time

2006

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Abstract. Recent phylogenetic evidence suggests that the extraordinary diversity of the Cape Floristic Kingdom in South Africa may be the result of widespread evolutionary radiation. Our understanding of the role of adaptive versus neutral processes in these radiations remains largely speculative. In this study we investigated factors involved in the diversification of Argyroderma, a genus within the most spectacular of the Cape radiations, that of the Ruschioid subfamily of the Aizoaceae. We used amplified fragment length polymorphisms and a suite of morphological traits to elucidate patterns of differentiation within and between species of Argyroderma across the range of the genus. We then used a matrix correlation approach to assess the influence of landscape structure, edaphic gradients, and flowering phenology on phenotypic and neutral genetic divergence in the system. We found evidence for strong spatial genetic isolation at all taxonomic levels. In addition, genetic differentiation occurs along a temporal axis, between sympatric species with divergent flowering times. Morphological differentiation, which previous studies suggest is adaptive, occurs along a habitat axis, between populations occupying different edaphic microenvironments. Morphological differentiation is in turn significantly associated with flowering time shifts. Thus we propose that diversification within Argyroderma has occurred through a process of adaptive speciation in allopatry. Spatially isolated populations diverge phenotypically in response to divergent habitat selection, which in turn leads to the evolution of reproductive isolation through divergence of flowering phenologies, perhaps as a correlated response to morphological divergence. Evidence suggests that diversification of the group has proceeded in two phases: the first involving divergence of allopatric taxa on varied microhabitats within a novel habitat type (the quartz gravel plains), and the second involving range expansion of an early flowering phenotype on the most extreme edaphic habitat and subsequent incomplete differentiation of allopatric populations of the early flowering group. These results point to adaptive speciation in allopatry as a likely model for the spectacular diversification of the ice-plant family in the dissected landscapes of the southern African winter rainfall deserts.

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Section: Mechanisms Of Evolutionary Divergence In Argyrodermamentioning

confidence: 99%

Evolutionary Radiation of "Stone Plants" in the Genus Argyroderma (Aizoaceae): Unraveling the Effects of Landscape, Habitat, and Flowering Time

2006

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“…Exceptions include mine populations of Mimulus guttatus, which possess an unidentified copper tolerance gene or gene complex that is favored by ecological selection but that interacts with 1 or more other loci to cause the death of F 1 hybrids in crosses to nonmine populations (29). Another exception involves sympatric dwarf and normal forms of lake whitefish (Coregonus clupeaformis), which show elevated mortality of embryos (30).…”

Section: Divergent Selection and Postzygotic Isolationmentioning

confidence: 99%

Genetics and ecological speciation

Schluter

Conte

2009

Proc. Natl. Acad. Sci. U.S.A.

559

616

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Species originate frequently by natural selection. A general mechanism by which this occurs is ecological speciation, defined as the evolution of reproductive isolation between populations as a result of ecologically-based divergent natural selection. The alternative mechanism is mutation-order speciation in which populations fix different mutations as they adapt to similar selection pressures. Although numerous cases now indicate the importance of ecological speciation in nature, very little is known about the genetics of the process. Here, we summarize the genetics of premating and postzygotic isolation and the role of standing genetic variation in ecological speciation. We discuss the role of selection from standing genetic variation in threespine stickleback (Gasterosteus aculeatus), a complex of species whose ancestral marine form repeatedly colonized and adapted to freshwater environments. We propose that ecological speciation has occurred multiple times in parallel in this group via a ''transporter'' process in which selection in freshwater environments repeatedly acts on standing genetic variation that is maintained in marine populations by export of freshwater-adapted alleles from elsewhere in the range. Selection from standing genetic variation is likely to play a large role in ecological speciation, which may partly account for its rapidity.reproductive isolation ͉ stickleback ͉ standing genetic variation ͉ transporter hypothesis O ne of Darwin's greatest ideas was that new species originate by natural selection (1). It has taken evolutionary biologists almost until now to realize that he was probably correct. Darwin looked at species mainly as sets of individuals closely resembling each other (1), in which case adaptive divergence in phenotype eventually leads to speciation almost by definition. Later, Dobzhansky (2) and Mayr (3) defined species and speciation by the criterion of reproductive isolation instead. Recent evidence indicates that reproductive isolation also evolves frequently by natural selection (4-7).Speciation by natural selection occurs by 2 general mechanisms (4, 7). The first of these is ecological speciation, defined as the evolution of reproductive isolation between populations, or subsets of a single population, as a result of ecologically-based divergent natural selection (6,(8)(9)(10). Under this process natural selection acts in contrasting directions between environments, which drives the fixation of different alleles each advantageous in one environment but not in the other (Fig. 1). In contrast, under mutation-order speciation (7, 11), populations diverge as they accumulate a different series of mutations under similar selection pressures (Fig. 1). Natural selection drives alleles to fixation in both speciation mechanisms, but selection favors divergence only under ecological speciation. Divergence occurs by chance under the mutation-order process.There is growing evidence in support of both ecological and mutation-order speciation in nature (4, 7), yet numerous aspects of ...

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“…Thus, the few artificial hybridization experiments that investigate habitat and temporal isolation have largely focused on the genetic basis of these traits (e.g. Macnair & Christie, 1983 ;Macnair, Smith & Cumbes, 1993 ;Schat, Vooijs & Kuiper, 1996 ;Kuittinen, Sillanpa$ a$ & Savolainen, 1997). Glasshouse experiments offer little for studying how hybridization affects pollinator preferences, although substantial information has been gathered on the genetic basis of floral traits that affect these preferences (e.g.…”

Section: Prezygotic Barriersmentioning

confidence: 99%

Plant hybridization

1998

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Summary 599 I. Introduction 599 II. Concepts and terminology 600 III. Historical background 600 IV. Studies of experimental hybrids 601 1. Isolating mechanisms 601 2. Prezygotic barriers 602 (a) Gametic barriers to hybridization 602 3. Postzygotic barriers 603 (a) Chromosomal rearrangements 604 (b) Genic sterility or inviability 604 4. Hybrid vigour 605 5. Introgression 606 6. Hybrid speciation 607 V. Experimental manipulations of natural hybrid populations 609 1. Hybrid‐zone formation 610 2. Pollinator‐mediated selection 610 3. Habitat selection 612 VI. The biology of different classes of hybrids 612 1. Character expression 613 (a) Morphological characters 613 (b) Chemical characters 613 (c) Molecular characters 613 2. The fitness of different classes of hybrids 614 (a) The importance of variance 614 (b) Estimating hybrid fitness 615 3. Interactions with parasites and herbivores 616 4. Patterns of mating 617 (a) Outcrossing rate 617 (b) Hybridization frequency 618 (c) Mate choice 618 VII. Conclusions and future research 619 Acknowledgements 620 References 620 Most studies of plant hybridization are concerned with documenting its occurrence in different plant groups. Although these descriptive, historical studies are important, the majority of recent advances in our understanding of the process of hybridization are derived from a growing body of experimental microevolutionary studies. Analyses of artificially synthesized hybrids in the laboratory or glasshouse have demonstrated the importance of gametic selection as a prezygotic isolating barrier; the complex genetic basis of hybrid sterility, inviability and breakdown; and the critical role of fertility selection in hybrid speciation. Experimental manipulations of natural hybrid zones have provided critical information that cannot be obtained in the glasshouse, such as the evolutionary conditions under which hybrid zones are formed and the effects of habitat and pollinator‐mediated selection on hybrid‐zone structure and dynamics. Experimental studies also have contributed to a better understanding of the biology of different classes of hybrids. Analyses of morphological character expression, for example, have revealed transgressive segregation in the majority of later‐generation hybrids. Other studies have documented a high degree of variability in fitness among different hybrid genotypes and the rapid response of such fitness to selection – evidence that hybridization need not be an evolutionary dead end. However, a full accounting of the role of hybridization in adaptive evolution and speciation will probably require the integration of experimental and historical approaches.

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Reproductive isolation as a pleiotropic effect of copper tolerance in Mimulus guttatus?

Cited by 141 publications

References 19 publications

Evolutionary Radiation of "Stone Plants" in the Genus Argyroderma (Aizoaceae): Unraveling the Effects of Landscape, Habitat, and Flowering Time

Evolutionary Radiation of "Stone Plants" in the Genus Argyroderma (Aizoaceae): Unraveling the Effects of Landscape, Habitat, and Flowering Time

Genetics and ecological speciation

Plant hybridization

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