Cytogeography of the subalpine marsh marigold polyploid complex (Caltha leptosepala s.l., Ranunculaceae).

PREMISE OF THE STUDY: Unrecognized variation in ploidy level can lead to an underestimation of species richness and a misleading delineation of geographic range. Caltha leptosepala (Ranunculaceae) comprises a complex of hexaploids (6x), rare nonaploids (9x), and dodecaploids (12x), all with unknown distributions. We delineate the geographic distribution and contact zones of the cytotypes, investigate morphologies of cytotypes and subspecies, and discuss the biogeography and evolutionary history of the polyploid complex. METHODS: Using cytologically determined specimens as reference, propidium iodide flow cytometry was performed on silica-dried samples and herbarium specimens from across the range of C. leptosepala s.l. Genome size estimates from flow cytometry were used to infer cytotypes. A key morphological character, leaf length-to-width ratio, was measured to evaluate whether these dimensions are informative for taxon and/or cytotype delimitation. KEY RESULTS: Dodecaploids were more northerly in distribution than hexaploids, and a single midlatitude population in the Northern Rockies yielded nonaploids. Genome size estimates were significantly different between all cytotypes and between hexaploid subspecies. Leaf length-to-width ratios were significantly different between subspecies and some cytotypes. CONCLUSIONS: Caltha leptosepala presents clear patterns of cytotype distribution at the large scale. Marked differences in morphology, range, and genome size were detected between the hexaploid subspecies, C. leptosepala subsp. howellii in the Cascade-Sierra axis and C. leptosepala subsp. leptosepala in the Rockies. Sympatry between cytotypes in the Cascades and a parapatric distribution in the Northern Rockies suggest unique origins and separate lineages in the respective contact zones.

Phylogeny and fruit evolution in Menispermaceae.

PREMISE OF THE STUDY: This work surveys endocarp morphology of Menispermaceae in the context of a well-supported molecular phylogeny. The study is important since menispermaceous endocarps appear often in the fossil record and indicate the presence of a wet forest ecosystem. • METHODS: Three chloroplast regions were used to derive phylogenies for 53 genera and 60 species. Endocarps of 47 genera and 92 species were dissected and morphological characters scored. Photographs of key features are presented. We superimposed our morphological matrix onto the phylogeny to explore character evolution. A detailed key to fruits is presented, allowing identification of extant and fossil specimens to the level of clade or genus. • KEY RESULTS: Menispermaceae consists of two major subfamilies: Tinosporoideae and Menispermoideae. Within Tinosporoideae, tribe Coscineae is basal. Within Menispermoideae, tribe Menispermeae is basal. Tinosporoideae consists mainly of taxa with apical style scars, bilateral curvature, subhemispherical condyles, and foliaceous cotyledons with divaricate or imbricate orientation. Menispermoideae consists almost entirely of taxa with basal or subbasal style scars, dorsoventral curvature, bilaterally and/or dorsoventrally compressed condyles, and subterete or fleshy cotyledons oriented dorsoventrally or laterally. • CONCLUSIONS: Several fruit characters differentiate major clades, and further synapomorphies are diagnostic of various subclades. Fruit characters that can be inferred as ancestral in the family are basal or subbasal stylar scars, endocarps with dorsoventral curvature, endocarp walls woody or bony, presence of a condyle, locule without ribs, sublateral vascular traces, presence of endosperm, and foliaceous or subterete cotyledons.

Phytogeographic implications of fossil endocarps of Menispermaceae from the Paleocene of Colombia.

PREMISE OF THE STUDY: Fossil leaves of Menispermaceae were previously described from the Paleocene of Colombia. Because of strong homoplasy of leaf characters, the fossils could not be placed more specifically within recognized clades, and additional data were needed to specify intrafamilial and paleogeographic relationships during the Paleocene. METHODS: Fossil endocarps of Menispermaceae were collected from the Cerrejón Formation, the recently discovered Bogotá flora, and Wyoming (∼60 Ma). We surveyed the endocarp morphology of almost all extant genera, conducted character optimization, a molecular scaffold analysis, and critically reviewed the related fossil genera. KEY RESULTS: Parallel syndromes of fruit characters have appeared in unrelated clades of the family according to current phylogenetic reconstructions. However, mapping selected endocarp characters across those clades that contain horseshoe-shaped endocarps facilitates identification and phylogenetic assessment of the fossils. Three fossil species are recognized. One of them belongs to the extant genus Stephania, which today grows only in Africa and Australasia. Palaeoluna gen. nov. is placed within the pantropical clade composed of extant Stephania, Cissampelos, and Cyclea; this morphogenus is also recognized from the Paleocene of Wyoming. Menispina gen. nov. shows similarity with several unrelated clades. CONCLUSIONS: The new fossils from Colombia reveal a complex paleobiogeographic history of the recognized clades within Menispermaceae, suggesting a more active exchange among neotropical, paleotropical, North American, and European paleoforests than previously recognized. In addition, the new fossils indicate that neotropical forests were an important biome for the radiation and dispersal of derived lineages in Menispermaceae after the Cretaceous-Paleogene boundary.

Genus-wide microsatellite primers for the goldenrods (Solidago; Asteraceae).

PREMISE OF THE STUDY: Microsatellite primers were developed for studies of polyploid evolution, ecological genetics, conservation genetics, and species delimitation in the genus Solidago. • METHODS AND RESULTS: Illumina sequencing of a shotgun library from S. gigantea identified ca. 1900 putative single-copy loci. Fourteen loci were subsequently shown to be amplifiable, single-copy, and variable in a broad range of Solidago species. • CONCLUSIONS: The utility of these markers both across the genus and in herbarium specimens of a wide age range will facilitate numerous inter- and intraspecific studies in the ca. 120 Solidago species.

Valinomycin biosynthetic gene cluster in Streptomyces: conservation, ecology and evolution.

Many Streptomyces strains are known to produce valinomycin (VLM) antibiotic and the VLM biosynthetic gene cluster (vlm) has been characterized in two independent isolates. Here we report the phylogenetic relationships of these strains using both parsimony and likelihood methods, and discuss whether the vlm gene cluster shows evidence of horizontal transmission common in natural product biosynthetic genes. Eight Streptomyces strains from around the world were obtained and sequenced for three regions of the two large nonribosomal peptide synthetase genes (vlm1 and vlm2) involved in VLM biosynthesis. The DNA sequences representing the vlm gene cluster are highly conserved among all eight environmental strains. The geographic distribution pattern of these strains and the strict congruence between the trees of the two vlm genes and the housekeeping genes, 16S rDNA and trpB, suggest vertical transmission of the vlm gene cluster in Streptomyces with no evidence of horizontal gene transfer. We also explored the relationship of the sequence of vlm genes to that of the cereulide biosynthetic genes (ces) found in Bacillus cereus and found them highly divergent from each other at DNA level (genetic distance values >or= 95.6%). It is possible that the vlm gene cluster and the ces gene cluster may share a relatively distant common ancestor but these two gene clusters have since evolved independently.

Phylogeny and biogeography of Caltha (Ranunculaceae) based on chloroplast and nuclear DNA sequences.

The genus Caltha (Ranunculaceae) consists of 10 species of low-growing, perennial herbs distributed throughout the moist temperate and cold regions of both the Northern and Southern Hemispheres. Traditionally, the species have been divided into two sections: section Psychrophila in the Southern Hemisphere with diplophyllous leaves and section Caltha in the Northern Hemisphere with leaves lacking inflexed appendages. This study uses chloroplast and nuclear DNA sequences to determine the relationships among the 10 species, test the monophyly of sections Psychrophila and Caltha, trace the evolutionary history of diplophylly, and explore biogeographical hypotheses for the genus. Analysis of these data resulted in a well-resolved and well-supported phylogeny. Section Psychrophila (C. sagittata, C. appendiculata, C. dionaeifolia, C. obtusa, C. introloba, and C. novae-zelandiae) was resolved as monophyletic, indicating a single origin of diplophylly. The species of section Caltha (C. natans, C. scaposa, C. palustris, and C. leptosepala) formed a paraphyletic grade. The resulting phylogeny strongly supports a Northern Hemisphere origin for Caltha, followed by dispersal to the Southern Hemisphere (Gondwanaland). A vicariance model is invoked to explain present-day distributions in South America, Australia, and New Zealand.

Revealing unknown or extinct lineages within Isoetes (Isoetaceae) using DNA sequencesfrom hybrids.

Isoëtes, a heterosporous lycopod with a fossil record dating back to the Paleozoic, has numerous putative allopolyploids (resulting from hybridization events coupled with doubling of chromosome number). By using the highly variable nucleotide sequences from the second intron of a LFY homologue in Isoëtes, species could be delimited and hybrid origins determined. The data suggest that reticulate evolution is both common and complex within a more derived species complex of Isoëtes. Sequences of identifiable parentage and sequences that are unlike any diploid species known were recovered, leading to the conclusion that one or both of the putative parents have not yet been discovered or are extinct. A range of observations concerning allopolyploid speciation were categorized as follows: (1) verification of previous hypotheses regarding parentage (e.g., I. riparia, I. appalachiana), (2) determination that two morphologically distinct allotetraploid species can share the same parentage (I. azorica and I. acadiensis), (3) recognition of a cryptic allotetraploid species, indicated by the presence of different parental genomes (I. "appalachiana" from Florida), and (4) identification of allotetraploid species with one or two unknown parents (e.g., I. tuckermanii, I. acadiensis, I. azorica, and I. hyemalis). Some sequences from diploid species are remarkably uniform among populations (e.g., I. echinospora from various locations in North America, Iceland, and Wales), while others are variable at the subspecies level (e.g., northern and southern populations within I. engelmannii).