Publications

The second edition of The Jepson Manual thoroughly updates this acclaimed work, the single most comprehensive resource on California's amazingly diverse flora and integrates the latest science with the results of intensive fieldwork, institutional collaboration, and efforts of hundreds of contributing authors into an essential reference on California's native and naturalized vascular plants. Includes treatments of many newly described or discovered taxa and recently introduced plants, and reflects major improvements to plant taxonomy from phylogenetic studies. Nearly two-thirds of the 7,600 species, subspecies, and varieties the volume describes are now illustrated with diagnostic drawings. Geographic distributions, elevation ranges, flowering times, nomenclature, and the status of non-natives and native taxa of special concern have all been updated throughout. This edition also allows for identification of 240 alien taxa that are not fully naturalized but sometimes encountered. A new chapter on geologic, climatic, and vegetation history of California is also featured.

Mentzelia hualapaiensis, a new species of Mentzelia sect. Bartonia, is described from the Grand Canyon region of Arizona. The new species is closely related to M. puberula, which is found west of M. hualapaiensis along the Colorado River, and to M. oreophila, M. polita, and M. tiehmii. It shares with these species a suffrutescent shoot system characterized by a subterranean, branching caudex, multiple annual branches, and similar leaves that have shallowly lobed or toothed to entire laminas. The flowers of M. hualapaiensis differ from those of its closest relatives in having cream- white, linear to narrowly spatulate petals and staminodes, characteristics that are convergent with those of the flowers of the Chihuahuan Desert species M. humilis.

Ecological opportunity - through entry into a new environment, the origin of a key innovation or extinction of antagonists - is widely thought to link ecological population dynamics to evolutionary diversification. The population-level processes arising from ecological opportunity are well documented under the concept of ecological release. However, there is little consensus as to how these processes promote phenotypic diversification, rapid speciation and adaptive radiation. We propose that ecological opportunity could promote adaptive radiation by generating specific changes to the selective regimes acting on natural populations, both by relaxing effective stabilizing selection and by creating conditions that ultimately generate diversifying selection. We assess theoretical and empirical evidence for these effects of ecological opportunity and review emerging phylogenetic approaches that attempt to detect the signature of ecological opportunity across geological time. Finally, we evaluate the evidence for the evolutionary effects of ecological opportunity in the diversification of Caribbean Anolis lizards. Some of the processes that could link ecological opportunity to adaptive radiation are well documented, but others remain unsupported. We suggest that more study is required to characterize the form of natural selection acting on natural populations and to better describe the relationship between ecological opportunity and speciation rates.

Results from molecular phylogenetic analyses indicate that three varieties of Mentzelia multicaulis (Osterhout) J. Darlington (Loasaceae) are more closely related to other species of Mentzelia sect. Bartonia Torrey & A. Gray than to M. multicaulis var. multicaulis. We elevate three varieties of M. multicaulis, originally described from Utah, to specific rank, recognizing them as M. librina (K. H. Thorne & F. J. Smith) J. J. Schenk & L. Hufford, M. flumensevera (N. H. Holmgren & P. K. Holmgren) J. J. Schenk & L. Hufford, and M. uintahensis (N. H. Holmgren & P. K. Holmgren) J. J. Schenk & L. Hufford. Both stamen and leaf shape characters support evolutionary relationships of these species with their closest relatives among the mentzelias found in the Intermountain West of the United States.

Ledermanniella prasina, J. Schenk & D. W. Thomas in the family Podostemaceae, sub-genus Ledermanniella, is proposed as a new species. It is known only from its type, collected at a single waterfall in Cameroon. The ecology, morphology, and variation among individuals are discussed. The new species is compared to the morphologically similar L. bifurcata, L. bowlingii, L. guineensis, L. jaegeri, L. minutissima, and L. monandra. Illustrations and a key to the monostaminate species in the sub-genus are provided.