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Generic delimitations within the cosmopolitan Carduus-Cirsium group (i.e., "thistles") have a long history of taxonomic confusion and debate. We present the most comprehensive molecular phylogeny of the group to date to test generic limits, reconstruct the evolution of pappus type, and elucidate the role of chromosomal evolution. We offer two solut...
Cirsium (i.e., “thistles”) are one of the most taxonomically challenging groups of Compositae in North America. This study represents the first attempt to infer a broadly sampled phylogeny of Cirsium in North America. The two main objectives are to: (1) test whether currently hypothesized species variety complexes (C. arizonicum, C. clavatum, C. ea...
Several taxonomic observations on the genus Abronia in Colorado and New Mexico are presented First, Abroma argillosa Welsh & Goodrich is a synonym of A glabnfoha Standi Second, Abroma carletonii Coult & Fisher is a synonym of A. fragrans Nutt ex Hook., and specimens of A. carletonu from New Mexico and Texas should be called A. nealleyi Standi. Thir...
Hedera L., the ivy genus, comprises approximately 16 taxa distributed throughout Europe, North Africa, Macaronesia, and Asia. Phylogenetic relationships within Hedera were examined using chloroplast DNA restriction site variation and noncoding sequence data. The cpDNA data were compared with the published nuclear ribosomal internal transcribed spac...
This study examines patterns of morphological similarity within Hedera (the ivy genus, Araliaceae). Both cluster and principal components analyses reveal two major groupings corresponding to species of Hedera with stellate and scale-like trichomes. Characters traditionally used to delimit members of the genus were evaluated. Morphometric analyses f...
Trichomes of Hedera L. taxa have long been used as an important character in delimiting species. Hedera exhibits two distinct trichome types: scale-like and stellate. This study examined the trichome variation in sixteen currently recognized Hedera taxa using scanning electron microscopy. Measurements of trichome morphology were taken, and variatio...
This study aims to first clarify phylogenetic relationships within the North American thistle clade to determine the monophyletic groups and select one for an evolutionary focus using phylogenomics. Second, to estimate lineage diversification rates and the location of diversification rate shifts to show evidence for radiation(s). Third, to quantify the effects of abiotic and biotic factors influencing diversification using birth-death diversification models incorporating geology, habitat, and trait evolution. Ultimately, this study will build upon our understanding of the abiotic and biotic factors contributing to diversification within the largest family of flowering plants.