As discussed above, it is generally agreed that the greatest problems in taxonomic understanding of bryophytes remain in the tropics (Schultze-Motel, 1982; Touw, 1974). The need for cooperative, modern studies that cross national and disciplinary boundaries is paramount. Therefore, our first goal was to identify a bryophyte study group within the paleotropics that would allow us to achieve three goals: (1) Train students in the full breadth of systematic techniques; (2) Provide a useful monograph of an important moss group; (3) Address issues of theoretical and conceptual interest in biogeography and evolutionary diversification. The desired criteria for each of these goals are as follows:

Training potential. To provide a useful training vehicle for study, within a five-year time limit, of relationships at different taxonomic levels and using the full range of available techniques, it is necessary that the study group have certain characteristics: (1) be distinctive (and thus potentially monophyletic itself), yet have unresolved higher-level taxonomic problems of circumscription or relationships; (2) have several sub-groups of manageable size (i.e., not more than approximately 20 species after synonymy is taken into account) suitable for monographic study by individual students; (3) have base-line alpha-taxonomy worked out to some degree in the existing literature (to facilitate identification of variation patterns), yet have problems remaining at the species level; (4) have a relatively restricted geographic range to facilitate detailed geographic sampling; (5) be easily cloned and maintained in culture, so that biosystematic techniques can be applied; (6) DNA easily extractable and suitable for PCR and sequencing.

Need for monograph. A systematic monograph is the ultimate product of systematics. It summarizes all that is known about the relationships of a group of organisms and serves as the basis for reliable identification, and for further biological studies. In comparison with other land plants, few bryological world monographs or revisions have been produced and in particular, tropical bryophytes have received less attention than bryophytes of temperate latitudes (some important exceptions being: Crosby, 1969; Touw, 1971; Allen, 1987; Stark, 1987; Zomlefer, 1993; Vitt, 1995). In addition to suitability for training as described above, desired criteria for selecting a study group to monograph include: (1) occurrence in some abundance in poorly-known regions of the world, where correct taxonomies are needed for various purposes of local residents, conservationists, biogeographers, etc.; (2) being of considerable ecological and evolutionary importance (in the sense of ecosystem roles and variation in characters of phylogenetic and evolutionary interest), so that the monograph is of interest to general biologists.

Theoretical interest. The ideal project would provide not only a monograph of a group that is ripe for such study, but an example of a complete systematic and biological study of a group of mosses, thus allowing it to serve as a study system for the examination of some fundamental concerns in the theory of systematics and evolution. Conceptual issues of particular interest to us include concepts of species and the nature of constraints that control evolutionary diversification in lineages. Diversification is affected by such factors as gene flow, ecological specialization, and contraints imposed by developmental programs. For a group to be of maximal use as a study system for investigating these issues, desired criteria include: (1) relatively recent diversification leading to interpretable patterns of endemism and disjunctive patterns of distribution; (2) ecological diversity in terms of habitat preference so that the role of ecology in evolutionary divergence can potentially be studied; (3) the presence of both asexual and sexual modes of reproduction, with variation in frequency of occurrence among taxa (a diversity in reproductive modes provides direct comparisons bearing on the influences of gene flow on diversification). (4) be amenable to developmental studies (which the relatively simple morphogenesis of mosses allows; Mishler and De Luna, 1991).

Choice of focus group: the Calymperaceae. The predominantly tropical moss family Calymperaceae meets the criteria listed above very well indeed. It is a distinctive group, yet several problems of circumscription at the family and generic level remain. It is moderately well-known on an alpha-taxonomic basis (on a region-by-region basis, at least) yet has a number of putative lineages in need of world-wide taxonomic work. While there have been excellent regional revisions, there have been no world monographs of any groups within the family. It is a family of considerable ecological abundance and importance in the tropics, a major component of the epiphytic flora in lowland forests (Gradstein and Pócs, 1989), and widespread on other substrates as well. Thus, a better understanding of species circumscriptions and relationships would be widely useful to ecologists and other biologists.

While the family is too large to monograph in its entirety within a five-year period (as is true for two of the three genera, Calymperes and Syrrhopodon), several sub-groups within those genera, as well as the genus Mitthyridium are of manageable size.

A number of these subgroups would serve well to address the theoretical issues discussed above regarding diversification. As pointed out by Gradstein and Pócs (1989), many species of Calymperaceae are widespread in the tropics. On the other hand, some species and species complexes within the Calymperaceae in the Pacific basin show narrowly restricted distributions and are taxonomically difficult (i.e., with subtle and variable distinctions among populations) and thus thought to be undergoing relatively recent diversification. A comparison among groups showing these differing biogeographic patterns would be quite instructive as to potential differences in biology.

Island systems are natural laboratories for the study of biogeography and diversification of lineages; island biogeographic patterns may have simpler explanations than those on continents because of the relative youth and dateable ages of the land surfaces. Small, non-economically important plants (e.g. mosses) in particular may best reflect natural biogeographic patterns of dispersal and vicariance, since such plants are least likely to have been introduced by humans (on purpose at least). For these reasons, and for practical reasons involving logistical support (see below under field work), we will focus on lineages within the Calymperaceae that are predominantly found on islands in the Pacific basin and around its rim.

Modern knowledge of Pacific mosses began largely with the work of one pioneering bryologist, Edwin Bartram (e.g., 1931, 1933a-b; 1936; 1939; 1940; 1945; 1949; 1950; 1951; 1956; 1957a-b; 1960a-c; 1961). Several areas of the Pacific remain poorly known for bryophytes, however. Important recent contributions in the southern Pacific include Miller et al.(1963; 1978), Whittier (1976), Manuel (1981), Koponen and Norris (1983), and Eddy (1988, 1990).

One good prospect for focus within the Calymperaceae is Mitthyridium, which appears to be a currently diversifying lineage in the Pacific, and a relatively recent derivative of the more pantropical, paraphyletic group Syrrhopodon. Mitthyridium is taxonomically difficult at the traditional species level, and is relatively narrowly distributed as a genus, known exclusively from the paleotropics. As an example of the research to be done, this proposal focuses on this genus as the subject of one monograph in the proposed project. One or two additional lineages of about the same size in Syrrhopodon or Calymperes will be chosen for study after they are carefully defined in the initial phylogenetic survey (see below).

To Next Section: History of the Study of the Calymperaceae

Return to Mishler PEET Home Page

Return to Mishler Lab Home Page