| BEN |
| BOTANICAL ELECTRONIC NEWS |
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| ISSN 1188-603X |
| No. 284 March 22, 2002 | aceska@freenet.victoria.tc.ca | Victoria, B.C. |
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Joint meeting of British Columbia and Washington botanists will take place at Selkirk College in Castlegar, B.C. from June 16 to June 19, 2002. More information and registration forms are available at
Interest will most likely exceed capacity, so if you are keen, please register early!
Until recently, botanists, ecologists, and wetland managers were debating whether an important invasive plant, Phragmites australis (Cav.) Trin. ex Steud., or common reed, was introduced or native to North America. Peat core analyses suggest that P. australis has been an uncommon member of mixed tidal wetland plant communities in North America for at least 3000 years (Niering et al. 1977, Orson et al. 1987). In the 19th but particularly in the late 20th century, P. australis began invading fresh and brackish wetlands in North America greatly expanding its range and abundance. Mixed wetland plant communities are replaced by near monocultures of P. australis, resulting in changed ecosystem processes and associated detrimental impacts on native wildlife (Marks et al. 1994, Meyerson et al. 2000). The population explosion of P. australis is often thought of being facilitated by changes in land use patterns and hydrologic regimes, increased disturbances, urbanization and eutrophication (Marks et al. 1994). However, the very same factors are thought to cause declines of P. australis in Europe (van der Putten 1997). Alternatively, it has been suggested that the invasiveness of P. australis is attributable to introduction of more aggressive European genotypes (Metzler and Rosza 1987, Tucker 1990, Besitka 1996) but until recently little information was available to support this hypothesis. Regardless of the status of P. australis as native or introduced, control attempts are widespread and the search for potential biological control agents has begun in North America and Europe (Tewksbury et al. 2002).
Research by Kristin Saltonstall at Yale University (Saltonstall 2002) has now confirmed the present-day existence of native North American haplotypes (lineages) and of introduced European haplotypes. A total of 27 haplotypes were identified of which 11 (A-H, S, Z, AA) are native to North America (Saltonstall 2002). Within the North American populations, a continuum of geographic substructuring exists for the native haplotypes. Types AA, F, Z and S are known historically from the Northeast; types E, G, and H are found throughout the Midwest; and types A-D are found in the South and Intermountain West only. Two haplotypes show worldwide distribution (I and M) with M as the most common type in North America, Europe and Asia. Type I is found along the Gulf Coast and also occurs in South America and Asia. (For more details see Saltonstall 2002.)
Comparing the genetic structuring of present-day populations with those available in herbarium specimens collected prior to 1910 reveals significant changes in haplotype frequencies in North America. While the herbarium samples show a widespread distribution of native haplotypes across North America, modern populations show a striking range expansion of the M haplotype (Saltonstall 2002). Type M has entirely replaced native types in New England and expanded to the southeast where no historic P. australis populations were known to occur. Type M (which is most closely related to other European types) has spread to the West and is also becoming prevalent in the Midwest. It is likely that the introduction of type M material has occurred sometimes in the early part of the 19th century, probably at several Atlantic coast ports. Over the last 150 years, among-population variation in North America has declined significantly and today the genetic structure of North American populations resembles that of Europe (Saltonstall 2002).
With the recent discovery of the presence of native and non-native populations of Phragmites in North America we also discovered easy to use morphological characters potentially distinguishing native and introduced genotypes. Preliminary observations of populations in New York, Wisconsin, Virginia, Arizona, and Louisiana as well as examination of numerous herbarium specimens indicate that such morphological differences may exist. Please note that these traits are based on examination of few native clones and need further confirmation. We also need to increase the sample size to assess whether the morphological differences between native and introduced genotypes are consistent across populations and lineages. More details and pictures are provided at: http://www.invasiveplants.net/.
In general, native populations appear to have a lower stem density, thinner more flexible stems, and produce a reddish-purple color on their stems and ligules in spring and summer that is not present in non-native populations. When checking for these differences note that the side of the stems exposed to the sun will show the brightest coloration. The reddish color fades somewhat into a chestnut brown in the fall but was still very obvious in October in Virginia; in the winter the red stems turn light brown and somewhat gray. The ligules of native genotypes are bright purple while ligules of introduced genotypes appear green or slightly yellow. Stems of native genotypes are smooth and shiny as if polished, particularly in the winter, while stems of introduced genotypes are tan and dull, rough and ribbed (ridges visible with the naked eye once the leaf sheath has been removed). These differences are easy to recognize by running your fingers up and down them stems. (Please note that a leaf sheath wraps around the stem almost entirely. It is important to remove the leaf sheath when checking for stem morphology or texture.) In instances where native and introduced clones grow in close vicinity of each other, differences in stem toughness become obvious on windy days. Introduced genotypes remain sturdy and erect and move little while native genotypes easily bend and swing in the wind. Stems of introduced genotypes are almost perfectly straight while stems of native genotypes often grow crooked. In the fall and winter, differences in the density of the inflorescence are also obvious; introduced genotypes appear to have a much denser and larger inflorescence. Observations in New York and Virginia also suggest that native genotypes senesce earlier than introduced genotypes (this is a common phenomenon in introduced species which often show extended growing periods). In addition, an unidentified fungus attacks native genotypes with dark spots often clustered around internodes while introduced genotypes do not show this attack. However, introduced genotypes are frequently attacked by a number of generalist fungi (Tewskbury et al. 2002). However this attack (visible as large, variable blackish areas) is restricted to leaf sheaths.
Our observations are based on few native clones and we need to confirm these morphological differences by examining different genotypes in the field and by growing them under standardized conditions in a common garden. We are currently developing a standardized data record sheet (available by the end of March at http://www.invasiveplants.net). We are unable to visit sites across North America ourselves and depend on your help to refine our ability to use easily visible field characteristics to identify native and introduced genotypes. We are particularly interested in:
We are currently developing standardized sampling protocols. These protocols will be posted on the web and we hope that many of you will be able to contribute to this important work. For immediate questions, to obtain instructions for collections or advice please contact bb22@cornell.edu .
The work outlined above is a collaboration of the Biological Control of Non-Indigenous Plant Species Program at Cornell University, Kristin Saltonstall at Yale University, and the University of Rhode Island. For further information or updates please visit: http://www.invasiveplants.net/
References:
An extraordinary conifer has been recently discovered in northern Vietnam, identified as new to science by Aljos Farjon, Kew's conifer specialist. The new species, a "missing link" between true cypresses (Cupressus) and the false cypresses (Chamaecyparis) was found in a remote area of northern Vietnam in ridge-top forest of extraordinary biodiversity. This is a remnant of a once-extensive forested region which covered much of eastern Asia and extended to North America. Only fragments of the forests now remain and the new conifer is one of the relict species left after the last Ice Age.
There are only about 630 living species of conifer but their use for timber makes them the most important tree species in the world.
The new conifer is a small tree with highly unusual foliage of two sorts on the mature trees; both needle and scale leaves. It was discovered by a team of scientists, which included Kew's orchid expert Dr Phillip Cribb and colleagues from the Vietnamese Institute of Terrestrial Ecology in Hanoi, the Komarov Institute in St. Petersburg and the Missouri Botanical Garden, on an expedition studying the orchid floras of the karst mountains of northern Vietnam.
Aljos Farjon has confirmed that the conifer is a new species in a new genus and has named it, with colleagues from Vietnam and Missouri Botanical Garden, Xanthocyparis vietnamensis, the Golden Vietnamese cypress. Apart from the extraordinary Wollemi pine (Wollemia nobilis), recently described from New South Wales, it is the first truly new conifer described since 1948.
Its closest ally, the Nootka cypress (Chamaecyparis nootkatensis), also now transferred to the genus Xanthocyparis, is found in North America. Gardeners will know it as one of the parents of the widely grown and much loathed Leyland's cypress (X Cupressocyparis leylandii). The consequence of the Vietnamese discovery is that the scientific name of Leyland's cypress will also have to change.
Sadly, the Golden Vietnamese cypress is already critically endangered in the wild. It is naturally rare, confined to limestone ridges in a small area not far from the Chinese border. It is also prized locally for its fragrant wood which is used for coffins and for making shrines. Only a few semi-mature and coppiced trees survive.
At a meeting of the World Conservation Union (IUCN) in Taiwan just before Christmas, the Vietnamese scientists, backed up by Kew and Missouri scientists, will propose that its mountain habitat should be established as a conservation area. The Missouri Botanical Garden is currently working on cultivation and propagation techniques aimed at the long-term survival of this new conifer.
Drawn by the spirit of amateurism and his own passion (a third-generation "fernie" in his family), Oliver Sacks joins the American Fern Society in a small expedition to Oaxaca in southern Mexico. This book is a slightly emended record of what Sacks (an inveterate journal-keeper) observed. Like all the best journals, it has a rich immediacy, a sense that we share the moment of the author's perceptions. Since Sacks is such a lovely writer, and he and his fellow travellers such fonts of knowledge about everything from Mexican history to Mayan culture to chocolate making to the workings of fern evolution, the book is a rare treat.
And ferns and other flora and fauna are what our traveller and his fellow pteridologists most enjoy. He loves ferns because they're ancient, evoking an all-green hothouse planet before the advent of showy, explicit flowers. ... Virtually a beginner's guide to botany, the book is peppered with Sack's own drawings of ferns.
At its core, Oaxaca Journal is a potent paean to amateurism. Sacks is almost worshipful in his admiration of those amateurs whose fieldwork has contributed mightily to the progress of science, from the Reverend William Gregor, who discovered titanium, to William Smith, the "father of geology" now immortalized in Simon Winchester's The Map That Changed the World. It makes you want to strap on your field glasses and catch the first flight south.
[From the dust jacket: "Oliver Sacks is a clinical professor of neurology at the Albert Einstein College of Medicine and an adjunct professor of neurology at the New York University School of Medicine. A fellow of the American Academy of Arts and Letters, he is the author of Wife for a Hat, An Anthropologist on Mars, and Uncle Tungsten: Memories of a Chemical Boyhood. He is a member of the American Fern Society, the British Pteridological Society, the New York Mineralogical Club, and the New York Stereoscopic Society." Another Sack's book full of botany: The Island of the Colorblind.]