Article

Genetics of Adaptive Radiation in Hawaiian and Cook Islands Species of Tetramolopium (Asteraceae; Astereae) : I. Nuclear RFLP Marker Diversity

Published by and copyright of the Botanical Society of America. The definitive version of this article is available at  http://www.amjbot.org/content/84/9/1236.full.pdf+html?sid=52169850-4ff7-466d-b182-5388a7e7d10e

Thirty-three nuclear RFLP (restriction fragment length polymorphism) probes were used to study genetic diversity in
 Hawaiian and Cook Islands species of Tetramolopium for comparison with previous morphological and isozyme studies and
 to provide greater resolution of the events associated with adaptive radiation in the genus. Levels of RFLP diversity are
 greater than those reported for isozymes, yet are still low in comparison to continental species. Genetic differentiation is
 greatest among species in sections rather than among sections and is concordant with the hypothesis of phyletic sorting of
 initial variability as suggested for morphological traits. Hypothesized introgression between T. lepidotum and T. filiforme is
 supported, but the evidence suggests bidirectional gene flow. Systematic relationships derived from the data agree with
 hypotheses based on morphology in the placement of populations within their respective species and the recognition of
 three main lineages within Hawaii. Inclusion of the Cook Islands species, however, renders section Tetramolopium paraphyletic,
 contradicting morphological, ecological, and crossing evidence. Interpreting these results in light of evidence from
 previous studies, the genetic diversity and relationships seen among species and sections of Hawaiian and Cook Islands
 Tetramolopium reflect the recent and rapid evolution of this group, limited addition of new variability, and phyletic sorting.

Thirty-three nuclear RFLP (restriction fragment length polymorphism) probes were used to study genetic diversity in Hawaiian and Cook Islands species of Tetramolopium for comparison with previous morphological and isozyme studies and to provide greater resolution of the events associated with adaptive radiation in the genus. Levels of RFLP diversity are greater than those reported for isozymes, yet are still low in comparison to continental species. Genetic differentiation is greatest among species in sections rather than among sections and is concordant with the hypothesis of phyletic sorting of initial variability as suggested for morphological traits. Hypothesized introgression between T. lepidotum and T. filiforme is supported, but the evidence suggests bidirectional gene flow. Systematic relationships derived from the data agree with hypotheses based on morphology in the placement of populations within their respective species and the recognition of three main lineages within Hawaii. Inclusion of the Cook Islands species, however, renders section Tetramolopium paraphyletic, contradicting morphological, ecological, and crossing evidence. Interpreting these results in light of evidence from previous studies, the genetic diversity and relationships seen among species and sections of Hawaiian and Cook Islands Tetramolopium reflect the recent and rapid evolution of this group, limited addition of new variability, and phyletic sorting.

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