Search

The African genus Welwitschiella has traditionally been placed in tribe Heliantheae. Our phylogenetic analysis of chloroplast DNA ndhF sequence data, however, reveals that it is part of tribe Astereae. In order to assess the relationships of this genus within the tribe, we produced a phylogeny based on ITS (nrDNA) sequence data of a sample including Amellus, African Conyza, Chrysocoma, Felicia spp., Mairia, Poeciliopsis, Printzia, Welwitschiella and Zyrphelis. Both parsimony and Bayesian analyses were done. The Bayesian analysis showed that African genera form a basal grade in tribe Astereae along with the Chinese Nannoglottis and South American and New Zealand genera, with Printzia being the earliest diverging member of the tribe. Mairia occupies an isolated position. Amellus, Chrysocoma, Felicia, Poecilolepis and Zyrphelis belong to subtribe Homochrominae, a South African radiation that also includes the St Helena endemics Commidendron and Melanodendron. Pteronia appears isolated, though it might be close to the Homochrominae. Welwitschiella is placed in the latest diverging African clade, subtribe Grangeinae, which also includes Grangea, Psiadia, Nidorella, and the African Conyza species except C. gouani. This subtribe is sister to the Eurasiatic subtribe Bellidinae, and together they are sister to the Astereae crown lineages of Australasia-Asia and South and North America.

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...

We examined isozyme variation in the dominant Chihuahuan Desert shrub, Larrea tridentata (creosotebush), to determine the genetic variation within and among populations, the biogeographic relationships of populations, and the potential inbreeding in the species. We surveyed 17 populations consisting of 20 to 50 individuals per population along a 1600-km north-south transect across the Chihuahuan Desert. The southernmost population was near Villa Hidalgo, Mexico, and the northernmost near Isleta Pueblo, New Mexico. All 12 isozyme loci examined were polymorphic (H(t) = 0.416), with up to nine alleles per locus. Despite high levels of variation, we detected moderate inbreeding in L. tridentata populations. Most variation was found within rather than among populations (G(ST) = 0.118). Furthermore, recently established populations in the northern limits of the Chihuahuan Desert did not show decreased levels of genetic variation (H(o) = 0.336). A significant correlation was found between pairwise genetic and geographic distances (r = 0.305). Larrea tridentata showed and continues to show a massive range expansion into the arid and semi-arid regions of the American Southwest, but as shown by the high genetic variation, this expansion took place as a wave, rather than a series of founder events.

Morphological and ITS (internal transcribed spacer) sequence data for 40 species of the Austral-Pacific genera Camptacra, Kippistia, Minuria, Peripleura, Tetramolopium, and Vittadinia as well as one semiherbaceous species of Olearia were subjected to cladistic analysis, separately and together. Minuria, Peripleura, and Tetramolopium are paraphyletic as currently defined. Tetramolopium vagans from Australia appears to represent an undescribed genus. Both Kippistia suadefolia and Peripleura diffusa show close affinity to Minuria species, and Minuria macrorhiza appears to contain two distinct but closely related species. Vittadinia and the remaining species of Tetramolopium and Peripleura form a strong affinity group. The distribution of indels and the combined analysis each provide evidence that the Hawaiian and Cook Island species of Tetramolopium are descended from New Guinea species. The combined analysis also suggests that the Cook Island species T. mitiaroense is sister to the Hawaiian clade. Olearia arguta groups strongly with Camptacra and shows no close affinity with either of the arborescent species of Olearia used to root these analyses. Marked homoplasy among morphological characters indicates why generic delimitation in the group has been problematic.

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.

Townsendia gypsophila, a new species from Sandoval Co., New Mexico, is described and illustrated. It is a narrowly distributed obligate gypsophile closely related toT. fendleri andT. incana. It overlaps the ranges of the two taxa at the edge of their distributional limits in New Mexico.

Tetramolopium is a genus of shrubby to suffrutescent perennial Compositae known only from New Guinea and the Hawaiian Islands. Evidence from biogeography suggests the genus was introduced into Hawaii from New Guinea recently, and perhaps originated from a single introduction. The morphological and ecological diversity of Tetramolopium in the Hawaiian Islands suggest there has been rapid divergence associated with adaptive radiation. Despite the diversity, all taxa are completely interfertile with fertile F1, F2, and F3 hybrids having been obtained. An electrophoretic study of allozymes revealed little divergence at 22 genes coding soluble enzymes. The mean genetic identity for pairwise comparisons of 19 populations from seven species is 0.95, a very high value normally obtained for conspecific plant populations. The results for Tetramolopium contrast sharply with other instances of high genetic identity between species, where taxa are similar morphologically and usually reproductively isolated. The enzyme data also support the hypothesis of recent, rapid divergence in Hawaiian Tetramolopium.

Erigeron campanensis, sect.Erigeron, is described as new from Central Chile (Cerro Campana, near Valparaiso). It is most similar toE. fasciculatus, from which it differs in leaf shape, leaf arrangement, pubescence of leaves, stems, and phyllaries, and stigmatic branches, of disc florets.

A new species,Sphaeromeria ruthiae, from Zion National Park, and three new combinations,S. martirensis,S. compacta, andS. potentilloides var.nitrophila, are presented. Morphological and anatomical evidence is used to support the recognition ofSphaeromeria as distinct fromTanacetum.