Search

We examined the effect of reproductive and life history strategies on the amount and partitioning of genetic variation in three annual species of Nuttallanthus. The North American species N. canadensis, N. floridanus, and N. texanus have regional to widespread ranges that overlap in the southeastern USA, are characterized by homogeneous populations and high fecundity, and possess showy, fragrant flowers seemingly adapted for insect pollination and outbreeding. Field and greenhouse studies on plants from 25 populations indicated that reproductive strategies were similar among species and showed predominant self- fertilization via cleistogamy and self-pollination prior to anthesis in chasmogamous flowers. Species were reproductively isolated and demonstrated complete cross-incompatibility after experimental crosses and no evidence for hybridization in mixed populations. Genetic variation was assessed using starch gel electrophoresis to resolve 15 isozyme loci in 50 populations. Conspecific genetic identity (I) values were high (0.819-0.936), but interspecific comparisons indicated many qualitative allelic differences and correspondingly low I values (0.516-0.623). Low levels of polymorphism and observed heterozygosity within populations and the disproportionate amount of gene diversity distributed among populations were concordant with reproductive data. The pattern of genetic differentiation was most similar to that observed in species with a predominantly inbreeding mating system. Key words: cleistogamy; isozyme; Nuttallanthus; Plantaginaceae; reproductive biology.

The Buddlejaceae sensu stricto is a small group of plants which recent evidence has shown to consist of four genera. The genus Buddleia is the largest and most widely distributed genus, consisting of approximately 100 species distributed in Asia, Africa, and the Americas. Emorya, Gomphostigma, and Nicodemia, each mono- or ditypic genera, are more geographically restricted. Sequences from 28 ingroup and seven outgroup taxa were examined in a phylogenetic analysis of the trnL intron and trnL-F intergenic spacer region of the chloroplast DNA to test monophyly of the ingroup and to determine relationships among Buddleia and related genera. Parsimony analyses result in two major clades with modest support. One clade consists primarily of Asian species of Buddleia and the segregate genera. The sister clade is composed of New World and South African species of Buddleia. High bootstrap values support the close relationships among the four genera, but our data do not support recognition of Emorya, Gomphostigma, and Nicodemia as separate genera. Traditional sectional treatments of Buddleia, based primarily on floral morphological characters, are well supported. The two species of Nicodemia, often regarded as a section within Buddleia based upon its fleshy fruits, are shown to be closely related. Other interspecific relationships are poorly supported or unresolved.

Pollen grains of tribe Sanguisorbeae (Rosaceae, Rosoideae) were examined using scanning electron microscopy to identify useful characters, test taxonomic and phylogenetic hypotheses among genera, and elucidate pollen character evolution based on a molecular phylogeny. Aperture number, aperture structure, pollen shape, and exine sculpturing were variable within Sanguisorbeae and were used to delineate six pollen types. Four types (I–IV) were observed only in subtribe Sanguisorbinae whereas two types (V–VI) were found only in subtribe Agrimoniinae. Pollen grains of tribe Sanguisorbeae were generally subprolate to spheroidal in shape, had operculate or pontoperculate apertures, and had three apertures, except for Margyricarpus (tetraperturate). Exine sculpturing within Sanguisorbinae represented variations of striate, verrucate, rugulate, and perforate patterns often with microechinate sculpturing. Striate exine patterns and prolate shapes characterized the pollen of the Agrimoniinae, except for the microechinate-verrucate pattern and subprolate to spheroidal shapes observed in Hagenia. Pollen characters are most useful at the generic level and, when mapped on to a molecular phylogenetic tree of the tribe, are concordant with a monophyletic Agrimoniinae and a clade comprising Margyricarpus + Acaena + Polylepis + Cliffortia + Sanguisorba in the Sanguisorbinae. Outgroup comparison indicated that operculate colpi, three apertures, and polymorphism for striate or microverrucate exines represented primitive states for tribe Sanguisorbeae. [ABSTRACT FROM AUTHOR]

Investigates the phylogenetics of a tribe Euphorbieae, a monophyletic lineage of spurge plants. Details on the cladistic analysis of 52 morphological characters of 61 species; Relationship between genus Anthostema and tribe Euphorbieae; Evidence on the monophyletic origin of subtribe Euphorbiinae; Suggestion for the taxonomic treatment of Euphorbieae.