| BEN |
| BOTANICAL ELECTRONIC NEWS |
|---|
| ISSN 1188-603X |
| No. 176 November 11, 1997 | aceska@victoria.tc.ca Victoria, B.C. |
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When I first became interested in the western black-fruited hawthorns in the 70s, their taxonomy and biogeography seemed straightforward. Hitchcock et al. informed me that west of the Cascades grew 20-stamen C. douglasii var. suksdorfii; while east of the Cascades, and disjunctly in the Great Lakes region, was found 10-stamen C. douglasii var. douglasii. I worked then in the Willamette Valley of Oregon, where plants fit the Hitchcock description of var. suksdorfii. Now and then I visited the Wallowas where hawthorns fit the description of var. douglasii. The taxonomy seemed simple and I felt lucky to be working where the hawthorn story was straightforward, because I knew that in the eastern US, the Crataegus situation was complicated by hybridization, polyploidy, and apomixis. However, in the intervening years, as a number of workers have begun to look more closely at our western varieties, we find that the goblins which make Crataegus study so complicated and challenging in the east, are present to bedevil us here as well.
Historically, black-fruited hawthorns were collected in the Columbia River drainage by Lewis and Clark in 1806, by David Douglas and John Scouler in 1825, by Thomas Nuttall in 1834, and extensively by W. N. Suksdorf in the early 1900s. Meriwether Lewis' collection was misidentified by Frederick Pursh and did not influence later taxonomy. David Douglas' collection became the type for the species C. douglasii. Nuttall's collection, like Lewis' was confused with another group. Finally, it was the careful collecting of Suksdorf and his collaboration with C. S. Sargent of the Arnold Arboretum that led, in 1907, to the recognition of the 2 varieties noted above. Here the taxonomy stood until present-day botanists began to study the group more closely. Notably, ongoing work by J. B. Phipps, M. Muniyamma, T. A. Dickinson et al., R. C. Evans, S. J. Brunsfeld and F. D. Johnson is beginning to shed light on what is proving to be a much more complicated situation than formerly believed.
In terms of biogeography, it is now clear that 20-stamen, black-fruited entities are not found solely west of the Cascades, nor are 10-stamen forms found solely on the east side. Brunsfeld and Johnson of the University of Idaho have found a number of sites where var. suksdorfii and var. douglasii are sympatric in eastern Oregon, eastern Washington and Idaho, and I have noted both varieties in the San Juan Islands of Washington State. As for ecology, workers have noted that var. suksdorfii populations are usually associated with relatively mesic sites, while var. douglasii seems able to inhabit not only mesic but also relatively xeric habitats. Genetically, most 10-stamen (var. douglasii) individuals tested have proved to be tetraploids; however, while many 20-stamen (var. suksdorfii) individuals are diploid, various degrees of polyploidy have been found in this group by Dickinson and his colleagues. In terms of breeding system morphology, while 10-stamen individuals tested have, perhaps as expected, shown evidence of apomixis, some 20-stamen individuals also reveal unreduced gametophytes.
In 1965, E. P. Kruschke, suggested that the differences between var. suksdorfii and var. douglasii were important enough to raise the former to species level. Brunsfeld and Johnson also proposed raising var. suksdorfii to specific rank in 1990. Dickinson and his co-workers, of which I am one, have felt that the diploid var. suksdorfii may have given rise to the tetraploid var. douglasii through a switch to apomixis with concomitant loss of a whorl of stamens. This was an event which we believed may have happened and continues to happen spontaneously at various places and at various times in response to environmental stress. For this reason, we have come to agree with Kruschke and Brunsfeld and Johnson, that Crataegus suksdorfii, as the putative diploid parent, deserves to be raised to species rank. Consequently, in a paper in preparation, Dickinson and I will designate a lectotype of Crataegus suksdorfii from among sheets collected by W. N. Suksdorf in 1904-1905. I have incorporated this view in my treatment of Crataegus for the Oregon Checklist. (The Checklist is preliminary to the new Oregon Flora being produced at Oregon State University under the direction of Aaron Liston and Scott Sundberg.) The two black-fruited hawthorns thus become Crataegus douglasii Lindl., and Crataegus suksdorfii (Sarg.) Kruschke, species with 10 and 20 stamens, respectively.
This should be the end of the black-fruited hawthorn story, at least for the present, but it is not. Steve Brunsfeld has proposed a new and most intriguing hypothesis: that what we call Crataegus douglasii may actually have arisen through hybridization between Crataegus suksdorfii and what Hitchcock refers to as Crataegus columbiana. (The latter was designated C. piperi by J. Phipps in 1995. See his interesting paper on C. columbiana, the "phantom taxon," in Taxon 44: 405-408.) The hybridization hypothesis is presently being tested in Brunsfeld's lab and Crataegus workers eagerly await the results. Looking at a mixed population of both 20- and 10-stamen hawthorns in fruit near Mt. Adams this July, and noting some intriguing variations in fruit shape, size, and color, I could not help but think I might be observing genetic mixing. Here I shall leave this brief discussion of the western black-fruited hawthorns, having alerted BEN readers to the possibility of more startling revelations to come.
For further reading:
Ordering information: Verlag Eugen Ulmer, Postfach 700561, 70574 Stuttgart, Wollgrasweg 41, Germany. For e-mail try: info@ulmer.de
This book is over 800 pages of pure enjoyment! It describes the vegetation of an area "from Denmark to the Spitzbergen, and from Iceland to Karelia (Finland)". The main core of the area is in fact the Scandinavian Peninsula. (British Isles, Baltic states, and northern parts of Russia are not included).
The introductory chapters describe the geology and biogeography of the area, its postglacial history, and the history of land use. The treatment of vegetation is divided into chapters on forests, aquatic and riparian vegetation, vegetation of mires and peatbogs, and vegetation that has been slightly and strongly modified by human activities. The final chapter gives a detailed classification scheme of plant communities of the area. Each chapter deals with the floristic classification of the respective plant communities, and describes their ecology. The ecophysiology of major plant groups is described in each chapter in order to understand how the plant communities function.
The vegetation classification combines results of Scandinavian schools of vegetation science and Cajander's school of forest typology, and presents them in the framework of the Braun-Blanquet hierarchical classification. Prof. Dierssen published the overall classification of wetlands of NW Europe earlier in his 1982 monumental work "Die wichtigsten Pflanzengesellschaften der Moore NW-Europas," Jard. Bot. Geneve. This present classification scheme covers all plant communities and provides an excellent key to understanding the vegetation of Northern Europe. A special section of the classification deals with communities of bryophytes and lichens.
The book is richly illustrated with 96 colour photos, 488 black-and-white photos and drawings, and 112 tables. The format is reminiscent of Ellenberg's "Vegetation Mitteleuropas ..." (see BEN # 169). One feature that surprised me most was the language. The book is written in German; however, the German used in the book is simple, clear, and straightforward, and one can understand it even with a limited knowledge of the language. Nevertheless, I hope that the English edition will follow soon.
Ordering information:
Cambridge University Press
The first edition of this Flora appeared in 1991 (see BEN # 53). The author aimed for "exactly the same kind of Flora" he always wanted to have for his own use. Such Flora should be user-friendly, complete, selectively illustrated and not too expensive. The first edition had tried to fulfill these criteria.
The new edition includes 200 new species and subspecies and with the additional extra hybrids, the total number of treated taxa covered is about 4,600. A new treatment of Rubus, Euphrasia, Taraxacum and Hieracium has been provided. Another important addition is the inclusion of chromosome numbers for all taxa where known. The illustrations were expanded to include the additional taxa, and the typographical execution of the book is much better than in the first edition.
Both professional and amateur botanists can envy their colleagues in the British Isles for having this book. Its clear keys and numerous detailed illustrations (often scanning electron microphotographs of seeds, fruits, or floral parts) make the identification of plants easy. The Flora includes both native and alien species (well established introductions and the 'casuals'). Introduced species represent about 20 per cent of the flora of British Columbia and most of those species are well covered in this new edition. In addition we may have almost the same percentage of circumpolar species that are again well treated in the New Flora of the British Isles. This Flora is thus an important reference for identification of many species of the flora of the Pacific Northwest.
Submissions, subscriptions, etc.: aceska@victoria.tc.ca. BEN is archived on gopher at freenet.victoria.bc.ca. The URL is: gopher://vifa2.freenet.victoria.bc.ca/11/environment/Botany/ben. Also archived at http://www.ou.edu/cas/botany-micro/ben/