UNIVERSITY of CALIFORNIA OTANICAL B ARDEN G NEWSLETTER Vol. 28, No. 4/Vol. 29, No.1 Published by the UNIVERSITY OF CALIFORNIA BOTANICAL GARDEN at Berkeley Fall 2003/Winter 2004 Horsetails and Whisk Ferns Re-examined When a “fern ally” is really a fern t is an exciting time to be botanists have tried to under- Ian evolutionary biologist, stand the relationships because we now have the tools J.Photo by Williams among these four major and techniques to be able to groups of plants. In the past, piece together the tree-of-life. pteridophytes have often Not only has the human been considered a transitional genome been sequenced, but evolutionary grade leading to the genomes of many organ- the so-called “higher” plants, isms, representing different those producing flowers and branches in the evolutionary seeds, or naked seeds. A con- tree, have now been deter- sequence of this traditional mined and compared. This view is that many aspects of avenue of research will even- seed plants are commonly tually lead to improved regarded as having been understanding of develop- derived from fern ancestors. mental patterns in plants and Recent work reported by my how traditional morphological colleagues and me shows that characters have evolved, re- the familiar plant organs and evolved, and sometimes disap- development we normally peared. In addition, these evo- associate with seed plants can lutionary trees, although only Horsetails (Equisetum telmateia var. braunii) is prolific in the Garden, not be derived from ferns. a best estimate (hypothesis) of especially near Strawberry Creek and the Conference Center. This should ultimately lead actual evolutionary events, to a re-interpretation of the will help us to interpret better the sometimes meager fossil evi- development of structures like leaves and branching patterns dence, and then to produce a time line for estimating when in the two groups. certain lineages arose or went extinct. Until recently, Equisetum, the genus of the horsetails, and Most of the 450-million year history of plants on land Psilotum, the genus of whisk ferns, were considered separate belongs to the bryophytes (mosses, liverworts, and horn- and isolated lineages of plants, dating back into the Paleozoic worts), pteridophytes (ferns and fern allies), and gym- era. This made intuitive sense because both genera appear to nosperms (conifers). The flowering plants (angiosperms) are be very different from other vascular plants (tracheophytes), relative newcomers on the scene and came into ecological (continued on page 2) dominance about 90 million years ago. For over a century 2 University of California Botanical Garden at Berkeley FERNS (continued from page 1) chosen for study because of their slowly evolving nature and their function in key biosynthetic and developmental “simple” in construction and growth and lacking true leaves. processes. For example, one of the chloroplast genes chosen, Horsetails and whisk ferns were considered “fern-allies,” a gene called rbcL, codes for a protein that helps plants use primitive vascular land plants having well-differentiated spe- carbon dioxide to make sugar during photosynthesis. In cial tissues (xylem and phloem) for transporting water and addition, we scored 136 characters from traditional mor- food. Together, the ferns and so-called fern-allies were con- phology, characters that relate to all parts of the plant body sidered to be “pteridophytes”—organisms having vascular tis- and all stages of the life cycle. Because the mode of inheri- sue that reproduce by spores and tance of most of these morphological characters is believed to having somewhat independent be complex and the characters life-cycle phases, a very small and character states themselves gametophytic phase and a gener- are controlled by many genes, it Photo by J.Photo by Williams ally much larger sporophytic was hoped that data based on phase. Pteridophytes were morphology might augment the thought to be among the “lower” results obtained from the DNA branches of the genealogical tree, sequence data. This approach of just above the bryophytic lin- integrating both morphological eages (mosses, liverworts, and and molecular data to hypothe- hornworts) in the land plant size relationships was first tree-of-life. But the exact inter- attempted in ferns by my col- relationships of these early leagues and me in 1995. In that branches have remained enig- study, the combining of indepen- matic, until very recently. dently derived data sets resulted There is new evidence that in evolutionary trees that were the horsetails (Equisetum) have more robust (having greater sta- closer affinities to ferns. The evi- tistical support) than trees pro- dence suggests that Equisetum duced using single data sets. and ferns are also sister groups, We continue our efforts to lineages that diverged from each understand the relationships of other early in their history, Whisk fern (Psilotum nudum) makes a show in the Tropical House. all spore-bearing vascular plants. probably about 350 million We are attempting to unravel the years ago. Moreover, these two lineages together form the sis- relationships of living horsetails (Equisetum), a genus inhab- ter group to all seed plants, both flowering plants and gym- iting north-temperate regions. In addition to being morpho- nosperms (conifers, cycads, and relatives). Ferns and horse- logically fascinating, horsetails have an extensive fossil record. tails make up one genetically related group, which evolved in A comparison of nucleotide sequences from all 15 species parallel to all seed-producing plants. Ninety-nine percent of has produced a tree that supports the traditional separation vascular plants living on the earth today fall into these two into two main subgenera, Equisetum and Hippochaete. This major lineages, having separate evolutionary histories dating same tree also shows, somewhat surprisingly, that the basal- back nearly 400 million years. A third lineage of tracheo- most member of the tree is one of the few tropical species in phytes, the remaining 1%, is the lycophytes — Lycopodium, the genus, the Andean Equisetum bogotense; this result con- Selaginella, and Isoëtes — and this group is now known to be flicts with trees based on morphological analysis. the sister group to both the ferns (including Equisetum and Researchers are now producing trees for many families of Psilotum) and seed plants. ferns, including the polypody family (Polypodiaceae), whose Our most recent research on the relationships of land members include the familiar staghorn (Platycerium), licorice plants is based on a combination of morphological characters (Polypodium), and rabbit’s foot (Phlebodium) ferns. When and DNA sequence data from 35 carefully chosen species, these are done, we shall have a much better idea of the clos- representing all of the main groups of land plants— est relatives of living genera and families of ferns, why some bryophytes, pteridophytes, and seed plants. In this study, lineages became dominant while others disappeared, and DNA sequences, involving a total of over 5000 nucleotide why certain morphological forms have evolved repeatedly. base pairs (the units making up genes and, ultimately, DNA —Alan Smith strands) were obtained from all 35 species. Four genes were Fall 2003/Winter 2004 3 THE DOCTOR SAYS It recently has been shown that fresh watermelons are a Orange juice formerly came as freshly squeezed or canned good source of lycopene, an antioxidant that has a number juice. In 1948, USDA and Florida researchers perfected a of health benefits. Commonly reported in tomatoes, gram method to produce frozen concentrate. Today US consump- for gram, watermelon has about 4 times as much as toma- tion from frozen concentrate comes to more than 1.97 bil- toes. However, processed tomatoes as ketchup, lion gallons a year. Agricultural Research (USDA-ARS) spaghetti sauce and tomato juice contain 5 50(12): 5. grams per ounce as contrasted with one gram per ounce in watermelon. In a Central American rain forest, a cinnamon Canned tomatoes, tomato soup, tree was found that was unharmed by any of the tomato sauce, and vegetable juice many organisms that might attack it. Isolations contain 3 grams per ounce. The from the plant resulted in finding a fungus, California Tomato Grower 46(2):3. Muscodor albus, which lives in the plant and produces volatile materials that control fungi and bacteria. It also Recent warnings from the EPA have been has been shown in a Montana laboratory that the materials released about the use of vermiculite. Any that is control nematodes and some insects. It is hoped that this more than a decade old may be laced with asbestos. This is material may be a replacement for methyl bromide. A com- because prior to 1990, vermiculite came from a site near mercial company is working to get it cleared and into pro- Libby, Montana, where a deposit of asbestos ran through the duction. Western Fruit Grower 122(2): 14B mine tainting much of the vermiculite. Science News — Robert Raabe 163(22):350. While this report had to do with the use of vermiculite as an insulation material, it should be noted that some gardeners use vermiculite in the preparation of potting Spring Bulb Bonanza mixes, seed beds, and other gardening functions. Though not a good material for such uses, this new information adds March 15 – April 15, 2004 a very good reason for not using it. The Garden will offer a special large collection of potted bulbs from around In Florida, a researcher has developed a diet pill for mos- quitoes that alters their digestion, making it impossible for the world either blooming or ready to them to feed, lay eggs or survive. It is environmentally safe. bloom this year, all at incredibly low Citrus and Vegetable Magazine 62(6):54, 56. prices, including multiple species or varieties of Allium, Babiana, Brodiaea, Two new strains of trailing snapdragons soon will be avail- able.