Pyroloideae

Abstract: Cladistic analyses of selected taxa of Ericaceae (and potential relatives) suggest that the family, as traditionally circumscribed, is paraphyletic. The traditionally recognized groups, Monotropaceae, Pyrolaceae, Epacridaceae, and Empetraceae, are nested within the cladistic structure of Ericaceae, and it seems reasonable to expand the circumscription of the latter. Preliminary analyses suggest thatActinidia (Actinidiaceae) likely is cladistically basal within Ericales, withCyrilla (Cyrillaceae) andClethra (Clethraceae) positioned, respectively, as second and first outgroups to Ericaceae. Generic relationships within Ericaceae are highly unresolved due to extensive homoplasy, butEnkianthus appears to be the sister group of the remaining ericad genera. The current division of the family into five subfamilies, i.e., Rhododendroideae, Ericoideae, Vaccinioideae, Pyroloideae, and Monotropoideae, very likely is not in accordance with phylogenetic relationships.

Abstract: Mycotrophism occurs in two ericaceous subfamilies, the Monotropoideae and the Pyroloideae. However, three aspects of the evolution of these subfamilies remain equivocal; 1) morphological, biochemical, and molecular analyses have failed to establish that the Monotropoideae is monophylectic; 2) the relationships among members of the Monotropoideae remain unresolved; 3) it is unclear whether the Pyroloideae should be included as a subfamily within the Ericaceae or treated as a separate family. To address these topics a phylogeny was constructed using a portion of the 28s ribosomal RNA gene from 22 members of the Ericaceae. Results indicate that the present Monotropoideae is polyphyletic; one species, Monotropsis ordata, is more closely related to members of the Vaccinioideae than to the rest of the Monotropoideae. This arrangement is supported by consideration of mycorrhizal type, consequently multiple origins of mycotrophic parasitism must be assumed. The relationships depicted within the Monotropoideae are nearly congruent with those depicted in Copeland’s (1941) phylogeny, and morphological or biochemical characters are identified which support the relationships depicted by the molecular tree which do not agree with the morphological tree. In addition, the data indicate, although not strongly, that the Pyroloideae should be included within the Ericaceae.

Abstract: The small subfamily Pyroloideae, comprising four genera, is unusual in Ericaceae because of its nearly herbaceous habit, largely free petals, and tendencies toward leaflessness. A surprising number of hypotheses exist with respect to the relationships among these genera. Parsimony analysis of 23 morpholog- ical characters gave a pattern that is largely congruent with that obtained from analysis of ITS sequences. Two sister clades of monophyletic/monospecific genera are resolved-Chimaphila + Moneses and Orthilia + Pyrola. Relationships among three species of Chimaphila are not clearly resolved. Some structure is present within Pyrola, with two strongly supported clades (P picta + PR aphylla + PR chlorantha and P elliptica + P minor). The placement of P minor is unsuspected; most past classifications have segregated it from other Pyrola due to its short, straight style (as opposed to a longer, curved style). Developmental study reveals that the style terminates elongation early, so that in fact it is not clear which style orientation is present. The overall bud-like nature of the flower in P minor further suggests a juvenile morphology relative to other Pyrola. The developmental information, in combination with its position on the cladogram, indicates a pae- domorphic origin for the floral morphology of P minor.

Abstract: The morphological and vascular characteristics of the nectaries of the species of the Monotropoideae (Ericaceae) reflect the morphology and declination of the flowers. These, in turn, are related to the pollination systems of the species. The nectaries of members of the Monotropoideae exhibit a range in form from slender, elongate projections, to short, stout ones, or to low ridges between the staminal bases. ANATOMICAL FEATURES may be expected to reflect particular aspects of the functional morphology of a flower. The necessity of functional interpretations of features of floral morphology has been pointed out by Carlquist (1969). Previous studies of floral nectaries have included few, if any, correlations with functional morphology. Knuth (1906-1909) discussed the floral nectaries of several plant groups in relation to their pollination mechanisms. Elias, Rozich, and Newcombe (1975) have related the functional relationships of the foliar and floral nectaries of Turnera ulmifolia (Turneraceae). Floral nectaries have been classified according to their location in the flower, (Fahn, 1953; Bonnier, 1879), their mode of secretion, (Behrens, 1879), and their vasculature, (Frei, 1955). Brown (1938) noted that nectaries seem to have arisen independently in several plant groups and have undergone modifications in those groups. Brown also pointed out that some families, like the Ericaceae, had various types of nectaries while others were fairly uniform in the type of nectary they possessed. Brown's illustrations of the nectaries depict sectional views of the flowers, but his descriptions do not relate to the pollination systems of the species under consideration. Correlations among production of nectar, stigmatic secretions, and the development of reproductive organs have been reported (Shuel, 1961). Puri (1951) has reviewed the literature concerning the many definitions and descriptions of nectaries. For the purposes of this study the term nectary denotes the floral nectary since no extrafloral nectaries have been found among members of the Monotropoideae. These nectaries are those structures or areas of the flowers involved in the production and secretion of nectar. 1Received for publication 3 May 1976. Research supported, in part, by National Science Foundation Grant GB 31648. Thanks are extended to Dr. R. Snelling, L.A. County Museum of Natural History for his identifications of insects. The loan of photographic equipment from Dr. S. Carlquist and his reading of the manuscript are appreciated. Since the nectar-producing areas of these species are not contiguous, each separate site of localized nectar secretion will be considered a nectary. Size and spatial arrangement of the nectaries is intimately related to the morphology of the corolla and reproductive organs of the flowers, so descriptions of these floral features will be included where pertinent. Nectar is almost exclusively a phloem exudate according to Frey-Wyssling (1955). He noted the preponderance of phloem in the vascular traces which supply the nectaries. Esau (1969) mentions a close positive relationship between the sugar concentration of a nectary and the amount of phloem present in the vascular supply to the nectary. The Ericaceae is a large, widely distributed family of angiosperms. It is composed of five subfamilies (Ericoideae, Monotropoideae, Pyroloideae, Rhododendroideae, and Vaccinioideae) whose interrelationships have been discussed elsewhere (Wallace, 1975a). The taxonomy and distribution of the members of the Montropoideae have also been covered (Wallace, 1 975b). Twelve achlorophyllous, mycoparasitic species comprise the Monotropoideae. Annual floral axes, the only aboveground portions of these species, arise from the perennial root masses. Populations of these species are never very dense; usually only a few floral axes are found in a given area. The axes are often inconspicuous, in spite of the fact that they may be brightly colored. The floral axes range in height from 2 cm, though usually taller, (e.g., Hemitomes, Pleuricospora, Pityopus), to 50 cm (e.g., Allotropa, Sarcodes) , to the tallest species, Pterospora, whose floral axes may be as high as 1.5 m. The number of flowers per inflorescence ranges from one (e.g., Monotropa uniflora, Monotropastrum humile, and irregularly in other species), to several (e.g., Hemitomes, Pityopus, usually), to many (e.g., Sarcodes, Pterospora). Members of the Ericaceae are usually considered to possess nectaries, although Henderson (1919) did not find nectaries in Pterospora,