Richard Whitkus

Genetics of adaptive radiation in Hawaiian and Cook Islands species of Tetramolopium (Asteraceae; Astereae). I. Nuclear RFLP marker diversity.

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.

RAPD Marker Variation in Eriastrum densifolium (Polemoniaceae): Implications for Subspecific Delimitation and Conservation

Eriastrum densifolium is a perennial sub-shrub exhibiting complex morphological variation. Five subspecies are recognized, differentiated by flower dimensions and geographic/elevational distribution. One subspecies, E. d. subsp. sanctorum, is known from a single population and is recognized as a federally endangered taxon. The subspecies are difficult to distinguish and do not adequately represent the total morphological diversity in the species. Variation in the species is examined with Random Amplified Polymorphic DNA markers in an attempt to identify genetically cohesive groups of populations. Random Amplified Polymorphic DNA marker diversity indicates that genetic variation is not partitioned geographi- cally or elevationally in the species, but genetic distance and geographic distance are well correlated. Furthermore, population relationships suggest that the currently recognized subspecies are not natural groups. Eriastrum densifolium subsp. sanctorum possesses relatively low genetic diversity in comparison to close geographic neighbors, is not genetically divergent from other populations, and is not a member of a distinct population group. In general, geographic variation in different Random Amplified Polymorphic DNA markers is discordant, and the resulting pattern suggests a continuum of neutral genetic marker variation in Eriastrum densifolium, with no intraspecific taxa evident.

A New Species Of Tetramolopium (Asteraceae) from Mitiaro, Cook Islands: Biogeography, Phylogenetic Relationships, and Dispersal

Abstract A new species endemic to Mitiaro, Cook Islands, Tetramolopium mitiaroense, is described and illustrated. The species is most closely related to Hawaiian species of Tetramolopium section Tetramolopium. Tetramolopium mitiaroense shares an upright dwarf shrub habit with T. remyi and T. capillare but differs in possessing semi-succulent, linear-oblanceolate leaves versus sclerophyllous, involute, linear leaves for the latter two taxa. Tetramolopium sylvae also has succulent leaves but differs from T. mitiaroense in having a prostrate, rosette habit and spatulate leaves. A key is provided for all eastern Pacific species of Tetramolopium. Published morphological, molecular, and geological data are reviewed to assess relationships amongst Tetramolopium taxa in the eastern Pacific and elucidate the biogeographic pattern of dispersal. The data support the hypothesis that Tetramolopium was first dispersed to the Hawaiian Archipelago from New Guinea with a secondary dispersal event from the Hawaiian Islands to the Cook Islands. Available evidence indicates that the Pacific Golden-Plover is the probable agent of dispersal from the Hawaiian Islands to the Cook Islands.

Assessment of Morphological Variation in Eriastrum densifolium (Polemoniaceae): Implications for Subspecific Delimitation and Conservation

Intraspecific morphological variation was investigated in the perennial sub-shrub Eriastrum densifolium to assess whether the five currently recognized subspecies adequately reflect the pattern and range of variation expressed in the species, and to determine if the endangered E. densifolium subsp. sanctorum is morphologically distinct from other populations. Vegetative and floral variation were analyzed at the species and population level, employing herbarium specimens, field collections, and common garden plants. The results of the analyses indicate that morphological variation within the species is largely continuous. The only exception is a group of plants distinguished from the remainder of the species by a single character, corolla tube length. This group of individuals matches the circumscription of E. densifolium subsp. sanctorum. The other four recognized subspecies fail to form well defined morphological groups in all analyses. Patterns of morphological variation are not correlated with either genetic variation or geography. The overall pattern supports the recognition of only two subspecies in E. densifolium. One group represents a single morphologi- cally divergent population (E. densifolium subsp. sanctorum), and the other group the remainder of the species, containing multiple, less divergent populations.

Quantitative morphological variation inTetramolopium (Asteraceae) in Hawaii and the Cook Islands

Multivariate analyses of quantitative characters were undertaken to examine the pattern of variation resulting from adaptive radiation ofTetramolopium in Hawaii and to investigate the systematics of an undescribed species in the Cook Islands and a group of populations of uncertain affinity on Kalaupapa Peninsula in Hawaii. Taxa differentiated on quantitative characters in the absence of qualitative characters. Differentiation was observed in multiple characters which could be organized into a few principal components. The analyses supported the species rank of the Cook Islands plants. The relationship of the Kalaupapa Peninsula populations to the rest of the taxa needs further study.

ANALYSIS OF CROSS-COMPATIBILITY IN ERIASTRUM DENSIFOLIUM (POLEMONIACEAE)

Cross-compatibility within and among populations of the perennialEriastrum densifolium was investigated to determine if sterility barriers have evolved within this polytypic species, and to correlate any such barriers to previously known patterns of genetic and morphological variation. Furthermore, the reproductive affinities of the endangeredE. densifolium subsp.sanctorum are investigated. Results indicate that no single population or group of populations is reproductively isolated from all other populations, and that F1 hybrids are fully fertile. Interspecific crosses (withE. eremicum andE. sapphirinum) were largely unsuccessful. The endangeredE. densifolium subsp.sanctorum demonstrates high interfertility with all other populations.