Ancestry and divergence of subtropical montane forest isolates: molecular biogeography of the genus Abies (Pinaceae) in southern México and Guatemala.

The genus Abies has a complex history in southern México and Guatemala. In this region, four closely related species, Abies flinckii, A. guatemalensis, A.

Genetic variation and population structure in central and isolated populations of balsam fir, Abies balsamea (Pinaceae).

Genetic variation and spatial genetic structure in balsam fir (Abies balsamea) were examined in two isolated populations in Iowa and Minnesota thought to be paleorefugia and in two ecologically central populations in old-growth forests of Upper Michigan. Overall levels of genetic variability at 22 allozyme loci were lower than that found in most conifer species (H(o) values ranged from 0.005 in the isolated populations to 0.

What data determine whether a plant taxon is distinct enough to merit legal protection? A case study of Sedum integrifolium (Crassulaceae).

Measures of molecular and morphological genetic variation are often used to set conservation priorities and design management strategies for plant taxa. Evaluated together they can give insights into a taxon's evolutionary status that neither data type alone can achieve. We investigated the distinctness and variability of Sedum integrifolium ssp.

Low levels of genetic variation within and high levels of genetic differentiation among populations of species of Abies from southern Mexico and Guatemala.

Populations of Abies in southern Mexico and Guatemala (A. flinckii, A. guatemalensis, A.

Genetic diversity of the endangered endemic Agave victoriae-reginae (Agavaceae) in the Chihuahuan Desert.

Long-lived perennials are a species-rich, ecologically important component of the North American deserts, yet we know little about their genetic structure, information important for their conservation. Agave victoriae-reginae is an endemic of the Chihuahuan Desert of northern Mexico that is endangered by collection for the ornamental trade. We examined levels and patterns of variation at ten polymorphic allozyme loci in ten populations representing the range of the species.

Evidence that the phytochrome gene family in black cottonwood has one PHYA locus and two PHYB loci but lacks members of the PHYC/F and PHYE subfamilies.

The phytochrome photoreceptors play important roles in the photoperiodic control of vegetative bud set, growth cessation, dormancy induction, and cold-hardiness in trees. Interestingly, ecotypic differences in photoperiodic responses are observed in many temperate-zone tree species. Northern and southern ecotypes of black cottonwood (Populus trichocarpa Torr.

Reproduction and development of the endangered Sedum integrifolium ssp. leedyi (Crassulaceae).

Information on reproduction and life history is important for the conservation of endangered plants. We investigated rates of flowering, seed set, and germination in populations of the endangered perennial plant Sedum integrifolium ssp. leedyi.

Morphological and molecular variation among populations of octoploid Fragaria virginiana and F. chiloensis (Rosaceae) from North America.

Relationships among 37 North American octoploid strawberry populations were studied by evaluating 44 morphological traits and 36 randomly amplified polymorphic DNA (RAPD) markers. Both data sets were analyzed by principal components analysis and UPGMA clustering based on genetic distances. Morphological data defined five groups: east of the Missouri River (Fragaria virginiana ssp.

Pinus banksiana has at least seven expressed alcohol dehydrogenase genes in two linked groups.

The alcohol dehydrogenase (Adh) gene family is much more complex in Pinus banksiana than in angio-sperms, with at least seven expressed genes organized as two tightly linked clusters. Intron number and position are highly conserved between P. banksiana and angiosperms.

Comparison of allozyme, RFLP, and RAPD markers for revealing genetic variation within and between trembling aspen and bigtooth aspen.

We examined genetic variation in allozyme loci, nuclear DNA restriction fragment length polymorphisms (RFLPs), and random amplified polymorphic DNAs (RAPDs) in 130 trembling aspen (Populus tremuloides) and 105 bigtooth aspen (P. grandidentata) trees. In trembling aspen 10 out of 13 allozyme loci assayed (77%) were polymorphic (P), with 2.

Constraints on the evolution of plastid introns: the group II intron in the gene encoding tRNA-Val(UAC).

The evolution of the group II intron in the plastid gene encoding tRNA(Val)UAC (trnV) from seven plant taxa was studied by aligning secondary and other structural features. Levels of evolutionary divergence between six angiosperms and a liverwort, Marchantia polymorpha, were compared for the six domains commonly demonstrated for group II introns and were shown to be statistically heterogeneous. Evolutionary rates varied substantially among various domains and other features.

Evolution of the ribosomal DNA spacers of Drosophila melanogaster: different patterns of variation on X and Y chromosomes.

Length variation of the ribosomal gene spacers of Drosophila melanogaster was studied. Analysis of 47 X chromosomal and 47 Y chromosomal linked rDNA arrays collected from five continents indicates that the arrays on the two chromosomes differ qualitatively. The Y-linked arrays from around the world share little or no similarity for either their overall length or the organization of their spacers.

EFFECTS OF AVIAN SEED DISPERSAL ON THE GENETIC STRUCTURE OF WHITEBARK PINE POPULATIONS.

We used allozyme analysis to examine family structure, the spatial patterning of related individuals, in two populations of whitebark pine (Pinus albicaulis), a subalpine conifer that commonly displays a multistem form. The individual stems within clumps are genetically distinct individuals, having arisen from separate seeds. Individuals within a clump are genetically more similar than individuals in different clumps, but individuals in neighboring clumps do not appear to be more similar than individuals in distant clumps.

Chloroplast DNA polymorphisms in lodgepole and jack pines and their hybrids.

Samples taken from throughout the ranges of distribution of lodgepole pine (Pinus contorta Dougl. ex. Loud.