An Essay on Species Concepts Developed during Revisionary Studies Author(s): Richard H. Zander Source: The Bryologist, Vol. 88, No. 3 (Autumn, 1985), pp. 215-220 Published by: American Bryological and Lichenological Society Stable URL: http://www.jstor.org/stable/3243031 Accessed: 09-06-2015 19:53 UTC Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://www.jstor.org/page/ info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. American Bryological and Lichenological Society is collaborating with JSTOR to digitize, preserve and extend access to The Bryologist. http://www.jstor.org This content downloaded from 192.104.39.2 on Tue, 09 Jun 2015 19:53:07 UTC All use subject to JSTOR Terms and Conditions The Bryologist 88(3), 1985, pp. 215-220 Copyright? 1985 by the AmericanBryological and LichenologicalSociety, Inc. An Essay on Species Concepts Developed During Revisionary Studies RICHARD H. ZANDER BuffaloMuseum of Science, Buffalo,NY 14211 The International Code of Botanical Nomencla- approach. Herbarium taxonomy contributes to an ture carefully avoids incorporation of a species con- understanding of the biology of a group through cept in the promulgated rules. We are given, instead, evaluations based on long familiarity (through ob- a structure of ranks with that of species as basal. A servation in the herbarium and in the field) with nomenclaturally correct name may have various de- morphological and phenological variation and their grees of biological substance, however, and only associated habitat and distribution. Thus, taxonom- rarely is such a name based on qualitative or quan- ic study itself reveals biological facts about organ- titative studies demonstrating that it represents a isms. But, because alpha-taxonomy is, for the most valid inference of the existence of a more or less part, simply well informed opinion, species con- clearly differentiated group of individuals in nature. cepts of taxonomists may differ according to differ- The period of exploratory botany of the last two ences between the taxonomists themselves: by how hundred years resulted in many geographic species well-informed they are, how much weight they give names with little species concept associated with new data, how inclined they might be to introduce them other than that their authors could not re- novelties, and various other tendencies and atti- member seeing anything quite like the representa- tudes. Given this situation, practical bryophyte tax- tive specimens before, at least from that area of the onomists generally do not espouse a "best" species world. The writers of floristics manuals and world concept, or even assume such exists, but show a revisions recognized that many species names from tolerance and acceptance of other workers' attempts the exploratory effort must be relegated to synon- to present their admittedly subjective studies as ymy because they are represented by specimens that contributions towards a useful taxonomic frame- intergrade on a morphological continuum that is work. called variability. This variation is generally sup- A species definition is a piece of guesswork-a posed to have a biological explanation. Neverthe- hypothesis that ties together observations and which less, acceptance that an intergrading spectrum of might be tested by future study with appropriate morphotypes requires synonymy of names is basi- controls. It is not a thing in nature that can be mea- cally a philosophical stance on the part of the tax- sured or studied. To demonstrate how species con- onomist. Seldom is there any experimental dem- cepts are important in representing the results of onstration of biological continuity between herbarium study at the alpha-taxonomic level, I will morphotypes. In fact some taxonomists are appar- review how my own concepts have developed over ently able to tell when the continuum is too broad 15 years of work with the Pottiaceae and then dis- and surely cannot represent only one species. Local cuss the various papers in the symposium with this floristic manuals may accept taxa that were not pre- experience in mind. It will be evident that my great- viously recognized in world revisions (e.g., Crum & est concern is with the way nomenclature deals or, Anderson 1981 versus Zander 1972 regarding syn- more often, avoids dealing with species concepts. onymy of Leptodontium excelsum Sull.). This may Presentation of nomenclatural novelties. New taxa be because certain taxa are more clearly distinguish- I have described have been conceptualized in con- able in some areas of the world than in others or texts of both splitting and lumping. Names in the are supposedly distinguishable if one looks close genera Fissidens (Zander 1969), Desmatodon (Zan- enough. Also, the descriptions and circumscriptions der & Crum 1977), Tortula (Zander & Steere 1978) of species and supraspecific taxa in regional treat- and Splachnobryum (Norris & Zander 1981) were ments may be different from those of the same taxa offered based on apparently unique combinations in world revisions in that the former are often based of character states but without evaluation of the solely on the local representation. These problems, value of such characters in general taxonomy of the and still others, are characteristic of the period of groups, which would be impossible in any case with- revisionary studies when synthetic species concepts out extensive revision. Names in Leptodontium begin to be established. (Zander 1972) and Trichostomum (Zander 1982c) One of the tenets of herbarium taxonomy is that were published for taxa that proved clearly distinc- much can be discovered about bryophyte biology tive in the context of regional revisions. New names, without recourse to a more lengthy experimental combinations and statuses were also given under 007-2745/85/215-220$0.75/0 This content downloaded from 192.104.39.2 on Tue, 09 Jun 2015 19:53:07 UTC All use subject to JSTOR Terms and Conditions 216 THEBRYOLOGIST [Volume 88 narrow, conservative species concepts in poorly formation, the taxa were distinguished at the understood genera: e.g., Didymodon (Zander 1978b), infraspecific level, a solution that better represents Tortella (Zander & Hoe 1979); and, in somewhat the perceived biological relationship. Sterile speci- better known or recently revised situations: Didy- mens can then be annotated "Leptodontium vitic- modon (Zander 1982b), Oxystegus (Zander 1982a, ulosoides sensu lato." A fact supporting this reso- 1983c), and Hyophila and Leptodontium (Zander lution is that a third variety, var. exasperatum (Card.) 1983b). The genus Pseudocrossidium was emended Zand., based on differences in laminal papillae mor- (Zander 1979a) to include species previously in Bar- phology, is represented by both anisosporous and bula and Tortula in order to recognize what was isosporous collections. This is an example ofa species hypothesized to be a monophyletic group evolving concept tailored in part to optimize the biological towards morphological modifications for photosyn- significance of its associated name. thesis. Clearly, the sophistication of the species def- The Code requires, through the principle of no- initions offered in the papers cited above depended menclatural priority, that taxa be discontinuous, at on the extent of knowledge of the group. least to the extent that the taxonomist must be able Morphological variation. Noguchi's (1956) paper to refer type specimens to the appropriate taxonom- offering extensive synonymy for species of Scope- ic group. For groups that appear to be nondiscon- lophila was the conceptual model at the species level tinuous, but very distinctive at the morphological for my treatment of this genus in the New World extremes, I at first (Zander 1978a, 1982d) used a (Zander 1967). The two species recognized (S. lig- taxonomically informal way of designating the ex- ulata (Spruce) Spruce, S. cataractae (Mitt.) Broth.) treme morphotypes (the species name sensu lato, are easily distinguished but are rather variable with followed by the term "facies" and the name of the respect to several characters. I pointed out two ex- earliest or the most familiar synonym, the type spec- tremes of morphological variation in S. ligulata: a imen of which approximated the extreme morpho- "hydric" form with loosely pulvinate habit and flac- type). This proved ungainly. Informal names for cid, spreading leaves with the upper leaf cells thin- bryophyte morphological variants, such as the walled and the enlarged basal cells often extending "Idealtypen" of Herzog (1907) or the "modificatio" more than halfway up the leaf, and a "montane" system of Buch (1922), have certainly never proved form with a densely pulvinate habit and narrow, popular. I then (Zander 1981, 1982b, 1983a; Zander firm, appressed leaves with the upper cells mostly & Eckel 1982) decided that non-discontinuous but thick-walled and the enlarged basal cells mostly con- distinctive infraspecific variants are better named fined to the lower third of the leaf. The existence of using standard nomenclature. I used a method that intra-specific intergradation between morphological assigned a particular varietal name to a distinctive