Adaptive Radiation and Genetic Differentiation in the Hawaiian Silversword Alliance (Compositae: Madiinae)

Witter, Martha S.; Carr, Gerald D.

doi:10.2307/2409011

Cited by 62 publications

(47 citation statements)

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“…It is unclear that the results for the ASCAB9 locus are representative of other structural genes. However, the results for this locus are in general agreement with previous studies indicating limited genetic differentiation in structural allozyme loci between species in the Hawaiian silversword alliance (15). Thus, accelerated regulatory gene evolution, more than structural gene evolution, appears closely correlated with the rapid morphological diversification of the Hawaiian silversword alliance.…”

Section: Accelerated Regulatory Gene Evolution and Adaptive Radiationsupporting

confidence: 90%

“…Both cytogenetic (14) and allozyme (15) data indicate that the Hawaiian species are tetraploids (n ϭ [13][14], in contrast to the basally diploid condition (n ϭ 6-9) in the most closely related North American species within the ''Madia'' lineage (13,16). Results of our recent phylogenetic analyses using two floral homeotic genes have led us to conclude that the Hawaiian silversword alliance descended from an interspecific hybrid between members of the Anisocarpus scabridus and Carlquistia muirii lineages of North American tarweeds (16).…”

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confidence: 99%

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Accelerated regulatory gene evolution in an adaptive radiation

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Robichaux

Purugganan

2001

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

183

110

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The disparity between rates of morphological and molecular evolution remains a key paradox in evolutionary genetics. A proposed resolution to this paradox has been the conjecture that morphological evolution proceeds via diversification in regulatory loci, and that phenotypic evolution may correlate better with regulatory gene divergence. This conjecture can be tested by examining rates of regulatory gene evolution in species that display rapid morphological diversification within adaptive radiations. We have isolated homologues to the Arabidopsis APETALA3 (ASAP3͞TM6) and APETALA1 (ASAP1) floral regulatory genes and the CHLOROPHYLL A͞B BINDING PROTEIN9 (ASCAB9) photosynthetic structural gene from species in the Hawaiian silversword alliance, a premier example of plant adaptive radiation. We have compared rates of regulatory and structural gene evolution in the Hawaiian species to those in related species of North American tarweeds. Molecular evolutionary analyses indicate significant increases in nonsynonymous relative to synonymous nucleotide substitution rates in the ASAP3͞TM6 and ASAP1 regulatory genes in the rapidly evolving Hawaiian species. By contrast, no general increase is evident in neutral mutation rates for these loci in the Hawaiian species. An increase in nonsynonymous relative to synonymous nucleotide substitution rate is also evident in the ASCAB9 structural gene in the Hawaiian species, but not to the extent displayed in the regulatory loci. The significantly accelerated rates of regulatory gene evolution in the Hawaiian species may reflect the influence of allopolyploidy or of selection and adaptive divergence. The analyses suggest that accelerated rates of regulatory gene evolution may accompany rapid morphological diversification in adaptive radiations.floral regulatory loci ͉ MADS-box ͉ CAB9 ͉ Hawaiian silversword alliance R ates of morphological evolution are generally not correlated with rates of molecular evolution. This paradoxical observation was highlighted early by Wilson and coworkers (1-3), and subsequent molecular studies in species groups that have undergone recent adaptive radiations, such as African rift lake cichlids (4), columbines (5), and the Hawaiian silversword alliance (6), have documented marked incongruities in rates of morphological and molecular evolution. A proposed resolution to this paradox has been the conjecture that evolutionary changes in regulatory genes, rather than large-scale diversification in structural genes, may be responsible for interspecific variation in organismal morphologies (1)(2)(3)(7)(8)(9). This conjecture is reinforced by molecular developmental studies that indicate that dramatic shifts in organismal structure may arise from mutations at key regulatory loci (7-9). One test of this conjecture is to examine whether there is a significant acceleration in rates of regulatory gene evolution in species that display rapid morphological diversification within adaptive radiations.The Hawaiian silversword alliance (Asteraceae: Heliantheae-Madiinae) is...

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Section: Accelerated Regulatory Gene Evolution and Adaptive Radiationsupporting

confidence: 90%

mentioning

confidence: 99%

Accelerated regulatory gene evolution in an adaptive radiation

Barrier

Robichaux

Purugganan

2001

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

183

110

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“…The isolation of these islands (both from the mainland and from one another), plus the wealth of different habitats available, provides ideal settings for rapid diversification and adaptation (Emerson, 2002). The Hawaiian archipelago, which lies greater than 3700 km from the nearest continental landmass, provides several famous examples of organismal radiations, including Drosophila (Kambysellis et al, 1995), spiders (Gillespie et al, 1994), birds (Lerner et al, 2011), and plants, such as the silversword alliance (Witter and Carr, 1988), and lobelioids (Givnish et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

The quest to resolve recent radiations: Plastid phylogenomics of extinct and endangered Hawaiian endemic mints (Lamiaceae)

Welch

Collins

Drautz–Moses

et al. 2016

Molecular Phylogenetics and Evolution

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(2016) 'The quest to resolve recent radiations : plastid phylogenomics of extinct and endangered Hawaiian endemic mints (Lamiaceae).', Molecular phylogenetics and evolution., 99 . pp. 16-33. Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThe Hawaiian mints (Lamiaceae), one of the largest endemic plant lineages in the archipelago, provide an excellent system to study rapid diversification of a lineage with a remote, likely paleohybrid origin. Since their divergence from New World mints 4-5 million years ago the members of this lineage have diversified greatly and represent a remarkable array of vegetative and reproductive phenotypes. Today many members of this group are endangered or already extinct, and molecular phylogenetic work relies largely on herbarium samples collected during the last century. So far a gene-by-gene approach has been utilized, but the recent radiation of the Hawaiian mints has resulted in minimal sequence divergence and hence poor phylogenetic resolution. In our quest to trace the reticulate evolutionary history of the lineage, a resolved maternal phylogeny is necessary. We applied a high-throughput approach to sequence 12 complete or nearly complete plastid genomes from multiple Hawaiian mint species and relatives, including extinct and rare taxa. We also targeted 108 hypervariable regions from throughout the chloroplast genomes in nearly all of the remaining Hawaiian species, and relatives, using a nextgeneration amplicon sequencing approach. This procedure generated ~20Kb of sequence data for each taxon and considerably increased the total number of variable sites over previous analyses. Our results demonstrate the potential of high-throughput sequencing of historic material for evolutionary studies in rapidly evolving lineages. Our study, however, also highlights the challenges of resolving relationships within recent radiations even at the genomic level.

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“…Likewise, examples of strong morphological differentiation between species without much genetic differentiation are known (e.g. Witter and Carr 1988 ;Soltis et al 1996 ), as are examples of strong genetic differentiation without obvious morphological divergence (e.g. Odrzykoski and Szweykowski 1991 ).…”

Section: Discussionmentioning

confidence: 99%