In the new classification system, the milkweed family, Asclepiadaceae, will be placed in the dogbane family, Apocynaceae. The prostrate milkweed ( Asclepias solanoana) from Sonoma County is shown here. Photograph by J. Game. UPCOMING CHANGES IN FLOWERING PLANT FAMILY NAMES: THOSE PESKY TAXONOMISTS ARE AT IT AGAIN! by Ellen Dean e had a sense that be- low herb) and relatives. The name If one examines the name loved plant names were Epilo bium canum was used for Cali- change section of The Jepson Manual Wat risk when the scien- fornia fuchsia in The Jepson Manual (Appendix III), one finds hundreds tific name of one of our favorite of Higher Plants of Californ, iwahich of name changes that were incor- species, Zauschneria californic(aC ali- was published in 1993, and that name porated in the 1993 publication. fornia fuchsia), became Epilo bium change had plenty of company. For (See Skinner and Ertter, 1993, for a canum. That change was suggested example, the generic names of many discussion of this topic with regard more than 25 years ago in the mid- of the species of Orthocarpu s(owl’s to rare plants.) Nearly 10 years af- 1970s when Peter Raven, the cur- clover) morphed into Castilleja or ter the arrival of The Jepson Manual, rent director of the Missouri Bo- Triphysaria, while all of our Stipa some of us are still reeling from the tanical Garden, reexamined the species (needle grass) took on other loss of Matric aria matric ario idesthe, relationships among Epilo bium (wil- generic names, such as Nassella. old name for pineapple weed. (What VOLUME 30:2, APRIL 2002 FREMONTIA 3 a wonderful name; somehow Chamomilla suaveolen swill never CLADISTICS, CLASSIFICATION, AND NAME quite do.) I imagine there are Cali- fornia botanists who don’t want to CHANGES OR TREES THAT HAVE PLANT see more name changes any time NAMES AT THE ENDS OF THEIR BRANCHES soon, am I right? Unfortunately, when it comes lassification is a basic hu- When put together, these two to plant taxonomy and classification, Cman endeavor; people clas- words are called the species name more changes are imminent, and sify tools, food, and telephone (ex. Quercus alb)a. For convenience, these are far reaching, often affect- numbers. Our classifications are Linnaeus placed the species he de- ing the families we have all known often hierarchical, that is, they scribed into classes based on sta- and loved for centuries. In a paper are nested subsets which may men type, arrangement, and num- titled “An ordinal classification for be visualized as venn diagrams ber, which meant that his classes the families of flowering plants,” (Figure 1) or written out as a often consisted of unrelated genera which was published in the fall of hierarchical list (Table 1). Plant and species. His revolutionary in- 1998 by the Angiosperm (flowering classifications using common novation was that he provided a ru- plant) Phylogeny Group (APG), a names are mainly made up of dimentary identification key to the group of 28 authors proposed a new folk genera such as “oak” or correct class—a huge help in orga- classification system for flowering “maple,” and folk species such nizing the increasing number of plants. The APG system is now be- as “coast live oak” or “big leaf plants that were being collected ing taught in college taxonomy maple,” although other catego- around the world. courses, thanks to the publication ries like “live oak,” “shrub,” or Linnaeus’s classification system of Plant Systematics: A Phylogenetic “tree,” may also be used. was replaced by plant classifications Approach, an excellent new plant sys- By the 16th century, Euro- that were based on presumed rela- tematics textbook by Walter Judd peans had begun the task of clas- tionships between species. At first et al. (2002). This text incorporates sifying every plant and animal in these classifications—which were much of the classification put forth the world by giving them a based on as many characteristics of in the APG paper, although it has a unique Latin description. In his the species as possible—were at- few surprises of its own. 18th century works, Carolus tempts to understand the order of For those of us who learned Linnaeus was the first to popu- nature or the plan of a creator. How- the flowering plant classifications larize a Latin description con- ever, by the end of the 19th cen- of Arthur Cronquist, Armand sisting of only two words, which tury, scientists began to incorpo- Takhtajan, or Robert Thorne when have become known as the ge- rate the notion of evolution into we took plant taxonomy in the 1970s nus name (e.g., Quercu,s the Latin classification systems. or 1980s, this new classification sys- common name for oaks) and its The term “phylogeny” was tem may come as a bit of a shock. modifier, the specific epithet coined to mean “evolutionary his- Most articles and books published (e.g., alba, Latin for white). tory,” and a “phylogenetic classifi- in this country over the past 20 years (including The Jepson Manua)l have followed Cronquist’s familial TABLE 1. SIMPLIFIED CLASSIFICATION classification. As with most flower- OF SIX SPECIES OF CALIFORNIA ing plant classification systems CONIFERS VIEWED AS A HIERARCHICAL produced during the 20th century, LIST Cronquist divided the flowering plants into a nested hierarchy of Pines Foothill pine (Pinus sabiniana) groups arranged to reflect an Sugar pine (Pinus lambertiana) approximation of evolutionary re- lationships. (See sidebar on pages Firs Silver fir (Abies amabilis) 4–7 for a more in-depth explana- Red fir (Abies magnific)a tion of classification.) He proposed two classes: the Spruces Sitka spruce (Picea sitchens)is monocotyledo ns(grasses, lilies, and Brewer spruce (Picea brewerian)a their allies, all of which have one seedling leaf or cotyledon), and the dicotyledon (fslowering plants with two 4 FREMONTIA VOLUME 30:2, APRIL 2002 did not become popular until the 1980s. Late in the same decade, the use of molecular data to de- termine relationships between species became commonplace. Scientists now sequence genes to look at the pattern of bases in DNA strands. Patterns between species are compared and ana- lyzed using computerized cladis- tic analyses or other methods of phylogenetic reconstruction. Well-studied morphological fea- tures can also be added to the analyses, and the resulting phy- logenetic trees are studied to de- termine relationships among species, genera, and families. Figure 1. Simplified classification of six species of California conifers viewed as a Venn Current classifications based diagram. on cladistic analyses only recog- nize monophyletic groups of or- cation” became one that placed spe- ing point (a putative ancestor) and ganisms (genera, families, or- cies, genera, or families together all the descendants above that ders). For example, recent clas- based on presumed evolutionary branching point is termed a “mono- sification systems recognize the relatedness. By the early 20th cen- phyletic group.” One example is the flowering plants (angiosperms) tury, some classifications included Fagaceae family, which are shown and monocotyledons, because drawings of evolutionary trees il- in Figure 2, although not all genera they form strong monophyletic lustrating the author’s hypothesis in the family are shown. groups in cladistic analyses (Fig- of ancestor descendant relationships The use of cladistics in taxonomy ure 3). These groups are not only among the flowering plants. These were called “phylogenetic recon- structions” or “phylogenetic trees.” In the 1950s, Willi Hennig, a German entomologist, began a school of phylogenetic reconstruc- tion called cladistics. The output of a cladistic analysis is a cladogram, a type of phylogenetic tree. The ma- jor contribution of cladistics is the explicit understanding that related species should be grouped based on shared features that are “derived” or different from those possessed by an ancestral population. These shared derived features are termed “synapomorphies.” For example, the scaly cupule (acorn cap) found in all members of the oak family (Fagaceae) is a mor- Figure 2. Hypothetical simplified phylogenetic tree of two California plant families phological synapomorphy for that in the order Fagales (not all families and genera are shown). Unifying synapomorphies family (Figure 2). A cluster on a that group members of the Fagales and members of the Fagaceae are indicated on cladogram that includes a branch- the branches. VOLUME 30:2, APRIL 2002 FREMONTIA 5 Figure 3. Simplifed phylogenetic tree of seed plants with key synapomorphies indicated on the branches. The innovation of one cotyledon unites all monocotyledons into a monophyletic group. As can be seen from this tree, most seed plants have two cotyledons, therefore the presence of this feature in dicotyledons is an ancestral (not a derived) feature. The dicotyledons, therefore, are not a monophyletic group. supported by molecular data, elimination of these groups is one branches. The most parsimoni- but they are defined by impor- reason for the current reshuffling ous tree, however, is not neces- tant morphological synapomor- of genera and families. sarily the true evolutionary tree. phies—the ovary in the case of Cladistic analysis and other Therefore, as more information the angiosperms, and one coty- types of phylogenetic reconstruc- is obtained over the next few ledon in the case of the mono- tion are not perfect, however, be- decades and new and better cotyledons (Figure 3). cause different genes or other char- forms of analyses are employed, In contrast, current classifi- acteristics may provide apparent the classification of flowering cations do not recognize the di- conflicting synapomorphies, pro- plants will continue to change. cotyledons (flowering plants with ducing different phylogenetic trees. Unfortunately for all of us, two cotyledons, the members of In these cases, it is assumed that when classifications change, which are outlined in Figure 3), some such features evolved more sometimes plant names change.