Catastrophic Selection as a Factor in Speciation

Lewis, Harlan

doi:10.1111/j.1558-5646.1962.tb03218.x

Cited by 172 publications

(71 citation statements)

References 21 publications

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“…The results presented here are consistent with Ornduff's (1976) suggestion that catastrophic selection (Lewis 1962) may have played an important role in the early and recent evolution of Lasthenia. In addition to evidence for rapid diversification during the history of Lasthenia, patterns of variation among modern populations in the genus are consistent with expectations for accelerated evolution in peripheral isolates (Simpson 1944).…”

Section: Saltational Diversification In Lastheniasupporting

confidence: 94%

“…Based on extensive crossing and chromosomal studies, Ornduff (1969Ornduff ( , 1976 suggested that the phenotypic diversity present in Lasthenia may represent only minor genetic differences among taxa and that the genus has been especially successful in adapting to the ecological diversity of its present range, as have other genera in which catastrophic selection (Lewis 1962) has presumably operated. Morphological and ecological differences among taxa of Lasthenia are nevertheless so great that species in the genus were once regarded as members of three different genera in two subtribes of Compositae.…”

Section: Introductionmentioning

confidence: 98%

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Goldfields Revisited: A Molecular Phylogenetic Perspective on the Evolution of Lasthenia (Compositae: Heliantheae sensu lato)

Chan

Baldwin

Ornduff

2001

International Journal of Plant Sciences

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to International Journal of Plant Sciences. DNA sequence data from the internal and external transcribed spacers of 18S-26S nuclear ribosomal DNA and the 3 trnK intron of chloroplast DNA provide evidence for patterns of evolutionary diversification and relationships in Lasthenia. Maximum parsimony analysis shows strong support for monophyly of Lasthenia and monophyly of each of seven sections (as treated here) in Lasthenia, with minor revision of Ornduff's (1966) sectional circumscriptions. Lasthenia sect. Amphiachaenia (correct name for L. sect. Baeria sensu Ornduff 1966 and redelimited to include L. leptalea) was resolved as a basally divergent section, i.e., as the sister group of a clade comprising all other Lasthenia taxa. Placement of other sections within Lasthenia is only weakly resolved, except for L. sect. Burrielia (redefined to exclude L. leptalea) and L. sect. Hologymne, which are robust sister clades. The clade comprising L. sect. Burrielia and L. sect. Hologymne and clades corresponding to each of the other sections except L. sect. Amphiachaenia constitute a polytomy, with most clades characterized by a long basal branch and relatively short terminal branches. We suggest that overall patterns of divergence in the molecular trees for Lasthenia conform to expectations of saltational diversification, with an initial rapid radiation followed by long periods of minimal diversification in each group preceding relatively recent episodes of speciation. Results also show that several important taxonomic characters in Lasthenia are homoplastic and that the base chromosome number for Lasthenia is xp8.

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Section: Saltational Diversification In Lastheniasupporting

confidence: 94%

Section: Introductionmentioning

confidence: 98%

Goldfields Revisited: A Molecular Phylogenetic Perspective on the Evolution of Lasthenia (Compositae: Heliantheae sensu lato)

Chan

Baldwin

Ornduff

2001

International Journal of Plant Sciences

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“…Many models of rapid speciation, mainly in insects, reptiles and mammals (White, 1978a) and in plants (Lewis, 1962), are based on the role of chromosomal changes as promotors of evolutionary novelties and reproductive isolation (see Sites & Moritz, 1987, for a review). In fact, some chromosomal rearrangements have been documented as responsible for decreasing the heterozygote viability and fertility, mainly due to the production of aneuploid gametes in meiotic segregation (White, 1978a).…”

Section: Introductionmentioning

confidence: 99%

Genetic instability and rapid speciation: are they coupled?

Fontdevila

1992

Genetica

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Models of rapid speciation by fixation of underdominant chromosomal rearrangements are constrained by multiple conditions on population structure and chromosomal performance. Realistic population conditions impose long periods of time to fixation or reproductive isolation, even under a model of accumulation of successive advantageous slightly underdominant rearrangements. However, when increased mutation rates are considered, fixation time is significantly reduced. Evidence is presented of high rates of chromosomal rearrangement production under genomic stress, such as in inbred and interspecific crosses. These episodes of high instability are most probably the result of mobile element transpositions, since transposition is also increased under genomic stress. Nonetheless, the evolutionary value of mobile elements to speed up speciation will be only significant if their mutagenic potential is activated in concert with population scenarios favorable to speciation events. Although this coupling needs to be demonstrated, many models of rapid speciation are carried out under population conditions favoring inbreeding and/or hybridization.

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“…Endemics were more than likely to be non-sprouting shrubs with seeds dispersed either passively or by ants (short dispersal distance). Short dispersal distance is associated with narrow endemism in Californian (Lewis, 1962) tropical (Gentry, 1986) and Australian floras (Renner, 1990).…”

Section: Taxonomic and Biological Profiles Of Endemicsmentioning

confidence: 99%

Profiling a besieged flora: endemic and threatened plants of the Cape Peninsula, South Africa

1996

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The Cape Peninsula (area: 471 km*), situated at the south-western extremity of the Cape Ploristic Region, has exceptionally high plant species richness (2285 species and infraspecific taxa) and numbers of endemic (90; 88 species and two infraspecific) and threatened (141; 138 species and three infraspecific) taxa (termed species from here on). This biodiversity is threatened by urban development and the spread of invasive alien plants. Peninsula endemics are concentrated in a few, predominantly species-rich families and these correspond well with endemic-rich families in other areas of the Cape Floristic Region. A high level of similarity exists between families with threatened and families with endemic species. A frequency analysis of the biological traits of both endemic and threatened species shows that low growing, ant-dispersed shrubs are over-represented in both groups. Endemics are most likely to be non-sprouters, but threatened plants do not have a specific post-fire regeneration strategy. Threatened species have higher frequencies of geophytes, sprouters and wind-dispersed species compared to endemic species. Numbers of endemic and threatened species are not randomly distributed with regard to occurrence in vegetation types and patterns are similar for both groups. The habitat and biological profiles of both endemic and threatened species suggest that they are highly vulnerable to extinction as a result of increasing rates of alien plant infestation, urbanization and inappropriate fire regimes.

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Catastrophic Selection as a Factor in Speciation

Cited by 172 publications

References 21 publications

Goldfields Revisited: A Molecular Phylogenetic Perspective on the Evolution of Lasthenia (Compositae: Heliantheae sensu lato)

Goldfields Revisited: A Molecular Phylogenetic Perspective on the Evolution of Lasthenia (Compositae: Heliantheae sensu lato)

Genetic instability and rapid speciation: are they coupled?

Profiling a besieged flora: endemic and threatened plants of the Cape Peninsula, South Africa

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