THE ASTERACEAE OF WISCONSIN
Assembled and edited by
Robert R. Kowal
2007 February 11
KEYS TO THE ASTERACEAE OF WISCONSIN
Tribe 1. Cardueae (Cynareae) - thistle tribe
Tribe 2. Cichorieae (Lactuceae) - lettuce tribe
Tribe 3. Vernonieae - ironweed tribe
Tribe 4. Inuleae - elecampane tribe
Tribe 5. Gnaphalieae - pussy's-toes tribe
Tribe 6. Astereae - aster tribe
Tribe 7. Anthemideae - camomile tribe
Tribe 8. Senecioneae - groundsel tribe
Tribe 9. Helenieae - sneezeweed tribe
Tribe 10. Heliantheae (s.l.) - sunflower tribe
Tribe 10a. Heliantheae subtribe Ambrosiinae - ragweed subtribe
Tribe 10b. Heliantheae subtribe Eupatoriinae - boneset subtribe
A. Illustrations from Wood (1974)
B. Phylogenetic trees
C. Checklist of species of Asteraceae in Wisconsin arranged by tribe and genus
D. Classifications of subfamilies and tribes of Asteraceae
E. Descriptions of tribes of Asteraceae
G. Alphabetical index of Asteraceae in Wisconsin
INTRODUCTION & ACKNOWLEDGMENTS
KEYS TO THE ASTERACEAE OF WISCONSIN is largely a compilation of other taxonomists' work, both published and unpublished. Most of the keys come from the PRELIMINARY REPORTS ON THE FLORA OF WISCONSIN, the work of Professor Hugh H. Iltis and his students, except for my treatments of the tribes Senecioneae and Astereae, which were never covered (except for Solidago and Aster). I give the intellectual sources after each tribe's and genus's (if different from the tribe's sources) heading (see "References"). Wetter, Cochrane, Black, Iltis, and Berry's CHECKLIST OF THE VASCULAR PLANTS OF WISCONSIN (2001) allowed updating the list of taxa [taxon, -a: a taxonomic group of any rank] occurring in Wisconsin and is the most important source for common names. The publication of the treatments of the Asteraceae in the Flora of North America (FNA, 2006: vols. 19-21), in addition to providing information for improving keys and for including or excluding taxa in the flora, provides (with minor exceptions) the taxonomy and nomenclature used herein, an improvement which is especially important because of the many changes in the circumscriptions of genera as a result of recent cladistic studies.
I have excluded hybrids, to keep the keys as simple as possible; they are usually only rarely encountered and usually require an expert to identify anyway.
Although virtually all information in the keys comes from others' work, I have edited all the keys more or less severely. In particular, the terminology used for the morphological structures characteristic of the Asteraceae is now more consistent among treatments (see "Terminology"). And, splitting of genera has necessitated completely rewriting some keys.
My thanks to the continuing line of plant taxonomists for their undervalued work. In particular, I express my gratitude to the Wisconsin State Herbarium at the University of Wisconsin-Madison, to all the many people who have contributed to it, and to the people responsible for its existence and maintenance, most recently, Prof. Hugh H. Iltis (Director Emeritus), Prof. Paul E. Berry, Director [until January 2006], Theodore Cochrane (Curator) and Mark Wetter (Curator). Ted and Mark are especially to be thanked for always being available to answer questions of content and style.
Dr. James A. Reinartz (Manager - Resident Biologist, Field Station of the University of Wisconsin-Milwaukee) provided the impetus for assembling these keys (which were initially largely xeroxes of published material), when he invited me to give workshops on the taxonomy and evolution of the Asteraceae in 1984, 1988, 1991, 1997, 2000, 2003, and 2005.
Stricter enforcement of copyright laws concerning xeroxing of published materials provided the impetus in 1997 for typing the keys, thereby creating an "original document". So, my sincere thanks to Ms. Barbara Schaack (Technical Typist III, Department of Botany), who accurately and intelligently retyped the source materials, creating the WordPerfect files that I have used for my revisions.
Further improvements are intended: giving pronunciations for Latin names, including more data on distributions and habitats, indicating which taxa are introduced vs. native, and adding a glossary. A start in this direction are the new sections on "Chromosome Numbers", "Terminology", and "Taxonomy, Nomenclature & Pronunciation". I hope that the keys eventually become available on the Wisconsin State Herbarium's website (http://www.botany.wisc.edu/herbarium/), along with pictures.
Note that the keys are explicitly for the taxa occurring in the State of Wisconsin and will not necessarily work elsewhere.
A hard-copy of Keys to The Asteraceae of Wisconsin is available in PDF format (500K). Note that due to potential copyright violations the illustrations of composite morphology (Appendix A) and the phylogenies (Appendix B) are excluded from this PDF file, as they are from this web-site. Having the document bound into a booklet with a spiral binding and goldenrod yellow covers (ca. $2.35 at a local copy shop) makes it much easier to use.
Any suggestions for improvements will be most gratefully received.
Robert R. Kowal
2007 February 11
ARRANGEMENT OF KEYS
The initial key is to tribes within the family, plus two well-marked subtribes within the Heliantheae (Ambrosiinae & Eupatoriinae). Although the emphasis on tribes may appear too academic and esoteric, in fact it is quite practical. The tribes and two subtribes are well-marked, and even a key that ignored tribal groups would strongly resemble this one. For some, learning to recognize tribes will make future identifications more efficient, as many species can then be taken directly to their tribe.
Tribes are arranged, insofar as possible, phylogenetically (Appendix B: 4), from those evolving earlier to those evolving later, and, correlated to some extent with this ordering, with those tending to be characterized by more primitive characters (ones that are thought to have appeared earlier during the course of the evolution of the family) preceding those tending to be characterized by more advanced characters (ones that are thought to have appeared later). The ordering and its interpretation as "primitive" to "advanced" is approximate and intellectually controversial. Some tribes appear simultaneously (as far as the estimated tree shows), times of origin of clades and characters are only roughly known at best, and each tribe has its particular advanced characters as well. However, the ordering provides enough accurate evolutionary information to make it preferable to an arbitrary arrangement. Tribes are numbered from 1 to 10, and the page numbers (in the upper right-hand corner of each page) include this number after the name of the tribe. Each tribe and subtribe has a key to its genera, followed by keys to each genus, arranged alphabetically.
Insofar as possible, I have given chromosome numbers of the genera and species. Virtually all are from the FNA (2006); those for Packera are from my own work. Note that the numbers given are for the species as a whole and do not necessarily occur in Wisconsin.
All land plants have an alternation of generations, with one individual producing gametes (by mitosis [sic]) and the other producing meiospores (by meiosis): the gametophyte alternating with the sporophyte. In flowering plants the pollen grain is a highly reduced male gametophyte, and the embryo sac is a highly reduced and modified female gametophyte. Both develop from meiospores produced by the dominant generation, the sporophyte. Usually the two generations are haploid and diploid, respectively, resulting in the traditional convention for referring to their chromosome numbers as n = 9 and 2n = 18 (using the commonest chromosome number in the Asteraceae as an example). However, this is not always the case. The gametophyte and the sporophyte can have the same number (e.g., in some ferns). Also, referring to the sporophyte's number as "2n" implies an even number of chromosomes, which is true for normal, sexually reproducing individuals, but is not true in general. Sporophytes frequently have odd numbers of sets of chromosomes due to the functioning of unreduced gametes; triploids with three sets are frequent and pentaploids (five sets), septaploids (seven sets), etc. occur. In addition, some sporophytes have one or more chromosomes missing from a complete set - or in addition to a complete set. Many other complications exist. A more accurate symbolism is to use "g" and "s" (e.g., g = 9 and s = 18) for the gametophytic ("gametic") and sporophytic ("somatic") numbers, respectively.
The "base number", "x", is the gametophytic or haploid number that is thought to have occurred in the unique ancestral species of a group. For example, our best guesses are that x = 9 for the family Asteraceae, x = 10 for the tribe Senecioneae, and x = 17 for the genus Helianthus. The basis for such a guess traditionally has been the most common low haploid number in a group. As phylogenetic trees become available, the haploid number of the basal branches are considered to give more trustworthy evidence. The genus Achillea provides an example of the use of the concept of base number. It has a base number of x = 9. The species A. Millefolium, the common yarrow, has s = 2x, 3x, 4x, 5x, 6x, 7x, 8x. Therefore, some individuals and/or populations have diploid, triploid, tetraploid, pentaploid, hexaploid, septaploid, and octoploid sporophytic numbers, or s = 18, 27, 36, 45, 54, 63, and 72.
Note that base numbers are relative: they evolve during the course of evolution. For example, the tribe Senecioneae's base number is probably x = 10. However, a group of genera within the tribe, including Petasites (sweet-coltsfoot) and Tussilago (coltsfoot), have a base number of x = 30. Presumably the common ancestor of the entire group (as well as each genus) was a hexaploid with s = 6x = 60 and g = 30, derived from a species with g = 10.
Chromosome numbers commonly provide support for the many new generic circumscriptions reflected, most importantly, in FNA (2006). The common white snakeroot, long called Eupatorium rugosum is now Ageratina altissima; it has g = 17, whereas Eupatorium's base number is x = 10. "Senecio congestus", the northern swamp groundsel, with g = 24, is now in Tephroseris (as T. palustris), where x = 24; Senecio (s.s.) has x = 10. Packera's x = 22 & 23, provide evidence supporting its segregation from Senecio (x = 10).
The Asteraceae are characterized by highly modified inflorescences and flowers. This necessitates a set of terms to refer to the corresponding structures. The terminology has evolved and proliferated, and taxonomists in the past and now differ in their usage. Some terms are synonyms; sometimes the same term is used for different structures; some are misleading. The terminology used in these keys is importantly derived from Arthur Cronquist (e.g., Gleason & Cronquist, 1991) and attempts to eliminate synonyms, to eliminate ambiguity, and to be simple and accurate.
The family is characterized by having its flowers condensed into a HEAD (Appendix A: 1a) [syn.: capitulum]. This inflorescence is not unique to the family, but it occurs in all the family's species. It is responsible for the traditional name for the family, the COMPOSITAE: what looks like a flower in the family (e.g., a sunflower or daisy "flower") is a "composite" structure of many small, true flowers packed together. Because the flowers are relatively small compared to those in other families, they are traditionally referred to as FLORETS (Appendix A: 1b).
Each head consists of outer bracts enclosing tightly packed florets (Appendix A: 1a). The outer bracts collectively form the INVOLUCRE with each bract called a PHYLLARY [syn.: involucral bract]. The enclosed florets sit on a flat (rarely hemispheric or conical) surface, the RECEPTACLE. Each floret may be subtended by a highly modified bract, collectively called CHAFF. A receptacle having chaff is called CHAFFY; a receptacle lacking chaff is said to be NAKED. Independently, the surface of the receptacle may bear hairs or be pitted (e.g., "alveolate").
There are different kinds of florets. The most common is the DISK FLORET (Appendix A: 1b), so called because they often cover most of the center of the receptacle, the DISK. A disk floret has the basic structure of the presumptive ancestral composite flower: an inferior ovary containing a single ovule (Appendix A: 3f), a 5-merous sympetalous corolla with five epipetalous stamens, a style terminating in two stigmatic branches. The fruit is an ACHENE (Appendix A: 3k, 4k, 6j). [In technical literature, "cypsela", an achene derived from an inferior ovary, is commonly used.] The floret shows a number of characters peculiar to the Asteraceae. On top of the ovary and fruit, outside the corolla, instead of a normal calyx, is usually a modified structure, a PAPPUS, consisting of scales (Appendix A: 3h, 6k), awns, bristles, or hairs (Appendix A: 1b), commonly functioning to aid dispersal. The stamens are "syngenesious" (Appendix A: 1g, 6f), with their anthers united laterally to form a cylinder into which their pollen is deposited; the pollen is pushed upwards out of the floret by the elongating style.
The ancestral composite corolla may well have been bilabiate, with an upper (inner) two-toothed lip and a lower (outer) three-toothed lip, as in snapdragons and lobelias, and such corollas occur in many Barnedisieae and Mutisieae (e.g., Gerbera, the commonly cultivated African daisy), along with other bilaterally symmetrical variants. However, in Wisconsin only three basic kinds of corollas and florets occur. A DISK FLORET (Appendix A: 1b) is radially symmetrical, with a five lobed corolla. It is usually BISEXUAL, producing pollen and, if pollinated, a fruit. In some genera it can be STAMINATE (Appendix A: 1f) [syn.: "sterile", "functionally staminate"], producing only pollen; usually an aborted ovary persists, as well as a modified style that pushes the pollen upwards. A RAY FLORET (Appendix A: 1c, 3c) has a kind of bilaterally symmetrical corolla that is elongated on the outer side into a RAY [syn.: "ligule"] terminating in usually three reduced lobes or "teeth". It never has stamens and is either PISTILLATE (Appendix A: 1c) [syn.: "fertile"], with a normal style and a functional ovary capable of forming a fruit, or NEUTER (Appendix A: 3c), without a style and with an aborted ovary. A LIGULATE FLORET (Appendix A: 6e) has a kind of bilaterally symmetrical corolla that is elongated on the outer side into a LIGULE terminating in five reduced lobes or "teeth". It is always BISEXUAL, with both functional stamens and ovary.
Heads differ in the kinds of florets that they contain. A DISCOID HEAD (Appendix A: "4b") contains only disk florets. An infrequent variant of a discoid head is a RADIANT HEAD, with marginal florets (bisexual, pistillate or neuter) having enlarged corollas, which are often splayed outward. A RADIATE HEAD contains disk florets in the center, surrounded by outer ray florets. A DISCIFORM HEAD (Appendix A: 4b) resembles a discoid head but has rayless pistillate florets marginally; these pistillate florets probably represent ray florets that have lost their rays during the course of evolution. A LIGULATE HEAD (Appendix A: 6d) contains only ligulate florets.
Composite heads, which often mimic flowers, are borne on a plant comparably to flowers in an inflorescence. Such a group of heads is technically a "capitulescence"; in the Flora of North America (FNA, 2006: vols. 19-21) "array" is used. However, I retain the traditionally used INFLORESCENCE; this word is part of the working vocabulary of even beginning taxonomists and allows the use, by analogy, of the terms used for the many kinds of true inflorescences.
TAXONOMY, NOMENCLATURE & PRONUNCIATION
In the Linnaean taxonomic system of classification (which was initiated by Carl Linnaeus (for plants) in his 1753 work, Species Plantarum), the most "natural" grouping of individuals is the species (sing. "species", pl. "species"). Its name is a binomial, the name of its genus plus a specific epithet, e.g., Quercus alba, for the white oak. The binomial is a Latin name, and, as with other words and phrases from a foreign language used in an English text, it appears in italic type in print (and is underlined in written text). The generic name MUST ALWAYS be capitalized, and the species epithet MAY ALWAYS be lower case. This latter rule is "recommended" by the International Code of Botanical Nomenclature (2000) (ICBN), and virtually all people follow this practice. As an older professional taxonomist, I do not follow this practice, because it results in the loss of information. Such information is interesting in its own right, but, its loss, more importantly, can result in error.
The traditional rule is to capitalize a specific epithet when it is not a simple descriptive adjective, i.e., when it is one of the following: 1) Derived from a person's name, e.g., either as a noun in the genitive case (Berberis Thunbergii, Japanese barberry) or as an adjective formed from a person's name (Pinus Banksiana, jack pine); 2) A generic name used in apposition [in "G.W. Bush, the president", the noun "president" is used like an adjective to modify another noun], e.g., Diervilla Lonicera, bush-honeysuckle, where the epithet is the generic name for honeysuckles; 3) A vernacular (aboriginal) name, e.g., Erythroxylum Coca, coca, where "Coca" is the American Indian name for the species. An advantage of the traditional rule is that it provides the reader with interesting information, i.e., that the epithet honors a person or is a generic name or a name used by indigenous people. More importantly, the information can prevent error. Latin adjectives are declined to agree in gender with the nouns they modify [See the discussion following]. If "Coca" is not capitalized one might be tempted to "correct" Erythroxylum coca to Erythroxylum cocum. More problematical are generic names that look like adjectives when not capitalized. Sedum [n.] Rosea, even when written Sedum [n.] rosea must not be "corrected" to Sedum roseum. Senecio [m.] Millefolium may be written Senecio millefolium, and must not be "corrected" to "Senecio millefolius"; transferring the species to Packera [f.], results in Packera Millefolium or Packera millefolium, not Packera millefolia. Both errors involving Millefolium have been made. In Andromeda Polifolia, the generic name when not capitalized looks like the adjective "poliifolius, -a, -um" [with leaves like "Polium", where the second "-i-" is a "connecting vowel"]; if the epithet were this adjective, the ICBN requires its correction to A. poliifolia. However, such a "correction" would be an error: A. polifolia is correct. The recommendation in the ICBN to decapitalize all specific epithets is an example of a "simplification" resulting in unintended complications. A more reasonable recommendation would be to allow this simplification in general, but to maintain the traditional rule in taxonomic and nomenclatural publications.
A species epithet should never be used alone, e.g. "Quercus alba" may be abbreviated to "Q. alba" but not to "alba".
As alluded to above, endings of species epithets may vary - or not (Stearn, 1966). The most common case is adjectives used as specific epithets, whose endings change depending on the generic name that they modify. Nouns in Latin have gender (masculine = m., feminine = f., or neuter = n.), and an adjective's ending "agrees" with its noun in gender. Different groups of adjectives differ in the sets of m., f., and n. endings that are used, for example:
-us, -a, -um
m. - Amaranthus albus
f. - Betula alba
n. - Chenopodium album
-er, -ra, -rum
m. - Helleborus niger
f. - Betula nigra
n. - Acer nigrum
-is, -is, -e
m. - Tragopogon pratensis
f. - Poa pratensis
n. - Trifolium pratense
Participles and some adjectives don't change, e.g.
m. - Ranunculus repens
f. - Ludwigia repens
n. - Trifolium repens
A common specific epithet is a noun, often a Latinized person's name, in the genitive (possessive) case, as in the phrase, Lacrimae Christi, "the tears of Christ", where "Christi" is the genitive of "Christus". The genitive suffixes of masculine and feminine singular nouns are usually "-i" and "-ae", respectively:
Berberis Thunbergii, for the collector Per Thunberg, Latinized "Thunbergius",
Cornus Priceae, for its discoverer, Sara F. Price, Latinized "Pricea",
Cypripedium reginae, "lady-slipper of the queen (regina)",
Cooksonia pertoni, "... of Perton Lane", for the street near the discovery site.
Note that if "Perton" had been the name of a person, it would be Latinized as "Pertonius", and the ICBN would require the binomial to be corrected to "Cooksonia Pertonii". The only easy way to avoid this error is to note that the epithet is not capitalized, indicating that it does not refer to a person.
Just as generic and aboriginal names are used as species epithets, other nouns in apposition are used, and these also remain in the nominative case:
Tyrannosaurus rex, "... the king",
Caryota gigas, "... the giant".
Of course, mostly we copy binomials from an authoritative source, like a flora. However, it is useful when writing and speaking to at least guess the gender of a generic name so that we are more likely to use the correct ending for a species epithet. The following rules will help. First, generic names of plants occur in the following order of frequency: feminine > neuter > masculine. Secondly, a generic name ending in ‑us, ‑a, or ‑um, is usually masculine, feminine, or neuter, respectively: Ranunculus (m.), Poa (f.), Chenopodium (n.). The commonest exception to this rule is that most woody genera are feminine, e.g., Pinus, Quercus, Cornus, Corylus, and Fraxinus; however, an exception to this rule is Acer, which is neuter.
Species often consist of races, which are sometimes discrete (like diploid and tetraploid races) but which usually intergrade (like eastern and central North American races). These are named as subspecies or varieties; sometimes a species is treated as having more pronounced races, subspecies, within which are less pronounced races, varieties. As with human races, such infraspecific differences are genetically real and ecologically significant at the populational and geographic levels, but their treatment in a system that misleadingly implies discrete taxa necessitates a certain degree of subjectivity and arbitrariness. Traditionally, very conspicuous mutants, like a white-flowered mutant within a pink-flowered species or a sessile-leaved mutant within a perfoliate species, were named as forms, e.g., Eupatorium perfoliatum forma truncatum; however, this practice (which I find useful) is passing from use.
Cultivated plants include sexual strains and clones artificially selected and maintained by agriculturalists and horticulturists, sometimes from stock derived by hybridizing different species. These are given non-Latin, "fancy" names that are not regulated by the ICBN. Such groups are "cultivated varieties" or "cultivars", e.g., Helianthus annus 'Russian Mammoth', a strain (i.e., a sexually reproducing race) with a single, huge head, and Rudbeckia nitida × laciniata 'Autumn Sun' ('Herbstsonne'), an asexually reproduced clone that is vigorous and floriferous. In general, cultivars are not included in floras, except in the rare cases when they escape from cultivation and persist in the wild.
The Linnaean classification groups species into successively larger taxa, representing the "supraspecific ranks". The genus (pl. "genera") is the most commonly encountered such group, being the first part of a species name and being a grouping that is often recognized, at least approximately, by non-taxonomists: pines (Pinus), oaks (Quercus), maples (Acer), goldenrods (Solidago), pussy's-toes (Antennaria), sunflowers (Helianthus). Successively larger groupings above the rank of genus have names based on the stem of a generic name to which a rank-specific ending (suffix) is added:
|Family||Aster + -aceae||Asteraceae|
|Order||Aster + -ales||Asterales|
|Subclass||Aster + -idae||Asteridae|
|Class||Magnoli(-a) + -opsida||Magnoliopsida|
|Phylum (Division)||Magnoli(-a) + -(o)phyta||Magnoliophyta|
Within families, especially larger ones, other, less well-known groupings may be recognized, as needed. Successively smaller groupings of genera within a family are named using the root of an included genus terminated by a rank-specific ending: Subfamily, -oideae; Tribe, -eae; Subtribe, -inae. In this work I largely use the subfamilial system of Panero & Funk (2002; Appendices B4, D3-4); the following of their taxa have representatives in our flora:
Tribe Cardueae (Cynareae)
Tribe Cichorieae (Lactuceae)
Subtribe Eupatoriinae ("Tribe Eupatorieae")
Note that there are other subtribes in the tribe Heliantheae (and other tribes) in our flora. Only the two listed above, representing morphologically well-marked taxa, are explicitly used in the keys.
Panero and Funk's (2002; Appendices B4, D3-4) recent treatment is based on DNA evidence and recognizes only monophyletic taxa. A consequence of the latter restriction is many more subfamilies (11) and tribes (35) than older, traditional systems, e.g., Bremer's (1994; Appendices B2, D2). However, none of the new subfamilies (all but one representing basal branches) occur in our flora, except for their Carduoideae, which includes our most basal tribe (the Cardueae), and most of the new tribes also are not in Wisconsin. The one exception is the Heliantheae, s.l., which they split into 11 tribes, 5 of which occur in Wisconsin. Only the traditionally recognized Heliantheae, s.l., is used here; the "tribe Eupatorieae" is phylogenetically embedded in this taxon and, therefore, is treated here as subtribe Eupatoriinae. Panero and Funk's ordering of tribes is largely the same as Bremer's (1994).
Panero & Funk's (2002) rationale for splitting up the traditional tribe Heliantheae is that, if tribe Eupatorieae is to be maintained as a tribe (the rank at which the taxon has been treated for about two hundred years), then, to avoid a paraphyletic tribe Heliantheae, that taxon would have to be split into separate tribes (ten of their eleven tribes). [A "paraphyletic" taxon is one that does not include all the descendents of its unique common ancestor; in cladistic taxonomy, only monophyletic taxa are recognized. N.B.: This is a contentious issue among taxonomists.] They recognize, but reject as too disruptive, an alternative solution, i.e., reducing tribe Eupatorieae to a subtribe within tribe Heliantheae. This latter solution is least disruptive of traditional usage, in my opinion.
Pronunciation of Latin names varies among taxonomists. Most follow the rule that "anything goes" if you can get away with it. Classical Latin pronunciation (Stearn, 1966) tends to prevail in continental Europe and is the system I initially learned. Largely I continue to use that system for determining which syllable to accent and whether a vowel is long or short; however, I generally pronounce vowels and consonants as they are in English. An excellent and convenient authority for pronunciation for the flora of northeastern North America is Fernald (1950), where, in addition, meanings of generic names and epithets are given, all the work of Arthur Stanley Pease, a professor of Latin at Harvard.
Some general rules are as follows. All syllables are pronounced, including a terminal "e" (e.g., Aloë, Leucanthemum vulga-re, Cirsium arven-se) and all double vowels (e.g., Cichor-i-e-ae, Ambros-i-i-nae, Erechtites hierac-i-i-folius). Note that diphthongs (most commonly "ae", as in "Aster-a-ce-ae") represent single vowel sounds (and used to be written as single symbols, e.g. "æ").
In general the antepenultimate (third from the end) syllable is accented: Xanthoxylum Clava-Herculus. When the penultimate (second form the end) syllable is long, it is accented: Anemone (a pronunciation not used by most Americans, myself included), Xanthoxylum americanum. The penultimate syllable is long if it ends in two (or more) consonants: Symphyotrichum macrophyllum. [The "ch" of the latter genus is the Latin transcription of the single Greek letter "chi" ("τριχoς") and apparently is considered equivalent to a single consonant, and so Symphyo'-trichum is accented on the antepenultimate syllable.] An authority like Fernald (1950) or a Latin dictionary must be consulted for many names.
W.T. Stearn's BOTANICAL LATIN (1966) provides an authoritative comparison of Latin vs. English pronunciation of vowels and consonants. For example, in Latin "Caesar" ("Cæsar") is pronounced like "Kaiser" in German, with the "c" hard (like "k") and with the diphthong "ae" sounding like the "ai" in "aisle". Try pronouncing "Aceraceae" (A-cer-a-ce-æ) with these pronunciations and the a's as in "father". Note that diphthongs are pairs of vowels (or a vowel and a "semivowel") elided together to form a vowel sound, e.g., "ai" in "aisle" and "oy" in "boy". In Latin and previously in English, the two symbols were joined; the modern practice of not doing so accounts for such superficially unpronounceable strings of vowels as in tribe "Spiraeeae", which is manageable when viewed as Spi-ræ-e-æ. Like the decapitalization of all species epithets, this is another example of "simplification" resulting in problems due to loss of information. Latin pronunciation of vowels and consonants often results in very different soundings for the names of common taxa. Try pronouncing "Viola" and "Violaceae" in Latin, with the "V" pronounced as "W" and the "i" as in "machine". And then one has a sociological problem with "Pinus", which in Latin (and in German!) unfortunately sounds like "penis" - exposing the whimsy in even the most hardened male undergraduate as he pairs the generic name with various, otherwise innocent epithets. One of the only places where Latin pronunciation is retained in English is for "Thuja", where the "j" is always pronounced like "y".
Rules of botanical nomenclature
The International Code of Botanical Nomenclature (2000) (ICBN) provides the rules governing how taxa are named. It provides a system that is used by taxonomists worldwide, and, the goal is stability, i.e., to reduce name changes to a minimum. It basically has no biological content, simply assuming that taxonomists recognize species and the various infraspecific and supraspecific ranks. Most name changes result from new biological information that requires new circumscriptions of taxa and changes of rank. Basic to the rules is "priority": the first name given to a taxon, starting with Linnaeus's Species Plantarum (1753), must be used - unless certain complications prevent its use.
In particular, the first epithet used for a species has priority, regardless under which genus it is was first used. For example, the first published Latin name of the golden ragwort is "Senecio aureus L.", where "L." represents the "author citation", the name of the author of the binomial (as well as the specific epithet), in this case Linnnaeus. For biological reasons the species has now been transferred to the genus Packera, so its correct name is now "Packera aurea (L.) Löve & Löve", where the author citation is now "(L.)" (the author of the specific epithet) and "Löve & Löve" (the authors of the binomial). Note that the species epithet (the Latin adjective for "golden") has its ending changed when transferred from Senecio (m.) to Packera (f.) so that it agrees in gender with the noun it modifies: "Senecio aureus" to "Packera aurea".
Although in sophisticated taxonomic and nomenclatural publications author citations are given to clarify the origin of a name, in most publications they should not be used, as they serve little purpose (ICBN, 2002: xii). In this practical book of keys, author citations would simply clutter the text.
The correct Latin names for the thistle and lettuce tribes
Reveal (1997) has found earlier places of publication of numerous suprageneric taxa in the Asteraceae. In particular, for the thistle and lettuce tribes, traditionally known under Cassini's (1815) names Cardueae and Lactuceae, respectively, Lamarck and DeCandolle published earlier (1806) the tribal names "Cynarocephalae" and "Cichoraceae". As the latter is based on the generic name Cichorium (though with an incorrect tribal termination), "Cichorieae" is accepted as the earliest name for the lettuce or chicory tribe. However, the former is not based simply on the generic name "Cynara", and so "Cardueae" remains the earliest name for the thistle tribe. The use of Cynareae in FNA (2006) is incorrect.
The fragmentation of the traditional genus Aster
The largest disruption of traditional nomenclature in the composite flora of North America involves the species traditionally included in the genus Aster: The Wisconsin species have been transferred to four new genera. Molecular phylogenies of the Astereae (simplifying only slightly) indicate that the genus Aster, s.str., is imbedded within an Old-World clade containing other Old-World genera and that the North American species of the tribe form a monophyletic clade with groups of species traditionally treated in the genus Aster forming separate branches, each more closely related to other New-World genera (e.g., Solidago, Gymnosperma, Guttierezia, Euthamia, Townsendia, Chrysopsis, Heterotheca, Grindelia, Erigeron, Boltonia, etc.) than to one another (Noyes and Riesberg, 1999, Appendix B5; Semple et al., 2002, Appendix B6). Therefore, these branches must be put into a number of small, monophyletic genera. In North America there is now only one native taxon of Aster, s.str. (an arctic-alpine subspecies of the Eurasian A. alpinus), and the remaining species are now split into 8 or 9 new genera, each more closely related to other genera than to one another.
The traditional binomials can be reconstructed from information in the keys. When the specific epithet under Aster differs from that in the new genus, the binomial is explicitly given. For most species, the specific epithet remains the same, and, to form the binomial under "Aster", simply give the adjectives masculine endings, so that they agree in gender with the masculine noun Aster, that they modify: from feminine (‑a under Doellingeria, Eurybia & Ionactis) or neuter (‑um or ‑e under Symphyotrichum) to masculine (‑is for "boreale" & "fragile" or ‑us for the remainder). Adjectives ending in ‑es, ‑ens & ‑ior and nouns in the genitive (‑ii, ‑iae, & the -is of "ontarionis" remain unchanged.
The genus Packera (Senecioneae)
The key to Packera (Senecioneae), a segregate from Senecio, incorporates the research of Alison M. Mahoney (Mahoney, 2000; Mahoney and Kowal, 2007 [?]) on the P. paupercula complex, including her more recent findings, and, more generally, my own research on the genus. Included are three diploid varieties of P. paupercula (vars. paupercula, savannarum, and pseudotomentosa), a group of tetraploid populations related to P. paupercula in northern Wisconsin (the "Northern tetraploid complex"), and a hexaploid population along the Mississippi River that is intermediate between P. paupercula var. savannarum and P. plattensis (P. paupercula var. savannarum + P. plattensis?). The latter two cytologically different taxa do not belong to any currently described species and complicate identifications, but users of the key must be aware of their existence.
Unfortunately, the key to the P. paupercula/P. plattensis complex is preliminary and not very useful in practice: measurements and pictures need to be added, and growing the plants and counting their chromosomes, though impractical, would be helpful (in some cases, even necessary) for accurate identifications. However, these taxa exist and are importantly responsible for the complex's being so confusing, especially when one only has information on gross morphology, especially from often inadequately collected and documented dried specimens.
The midwestern taxon originally described as "Senecio semicordatus" has been treated as a variety of both Packera aurea (Fernald, 1950) of eastern North America and P. pseudaurea (Gleason & Cronquist, 1950; FNA, 2006) of the Pacific Northwest. However, morphologically, ecologically, and cytologically, it is not closely related to either species. In particular, both P. aurea and P. pseudaurea have chromosome numbers based on x = 22, whereas the midwestern taxon has its based on x = 23. The taxon represents a species in its own right, probably best treated as conspecific with "Senecio flavulus" of the southern Rocky Mountains, itself also currently treated as a variety (var. flavula) of P. pseudaurea (FNA, 2006). However, the new combinations have not been made, so here the name Packera pseudaurea var. semicordata is used.
Plants of Wisconsin
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