The guide of the perplexed: essential nomenclature and iconography of the mistletoes of the
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The study of the mistletoes of the New World has, over the last several decades, achieved a level of stability that allows the construction of a nomenclatural guide for the four families involved (Eremolepidaceae, Loranthaceae, Misodendraceae, and Viscaceae). The one genus in Central and North America that, in the opinion of the author, has not reached such a level of resolution is the genus Arceuthobium, which is exceptionally complex especially in Mexico. The monograph authored by Hawksworth & Wiens (1996) cannot be regarded as a satisfying formulation of this complexity, but I do not prejudge future studies of this intractable genus. Since that monograph, however, there has appeared a comprehensive molecular study of the genus (Nickrent et al. 2004) in which a more conservative number of species is accepted; and my listing below, though without prejudice, is based on the species covered in that paper, and in the later Nickrent (2012). In South America, the genus Struthanthus remains seriously unresolved; a segregate genus, Peristethium, has recently been recognized (Kuijt 2012). Struthanthus is greatly in need of monographic treatment and, consequently, my citations below may not always be helpful or accurate; they are most reliable north of Colombia. Finally, my recent work on Passovia and Phthirusa (Kuijt 2011b) has revealed an unsuspected diversity of floral structure in the former genus, so that its taxonomic future may not remain entirely undisturbed. In the other genera in the neotropics, only minimal future changes are anticipated, even though some taxonomically challenging taxa remain, such as Phoradendron bolleanum, P. brachystachyum, P. juniperinum, and P. leucarpum. Many species have undoubtedly remained undetected so far; this is certainly true for South America, as new species continue to emerge. Keeping in mind the above disclaimers, generic and species names that I currently accept are listed in bold type.
It goes without saying that my presentation in many instances includes my personal judgments, and is scarcely written in stone; the danger in presenting a listing such as this is that future students may think that it is. I have indicated with a ♦ the heterotypic synonyms based (at least also) on my own judgment, to differentiate them from homotypic ones. Subsequent students of mistletoes may make different taxonomic judgments and, as mentioned, species presently not yet recorded are certain to be added. This document should be seen as a summary of my present taxonomic perceptions, being both fallible and necessarily incomplete. The intent is to facilitate the work of herbarium curators as well as that of future students and workers preparing geographically limited treatments. No new names or combinations are here presented.
Accepted names in bold, except in Arceuthobium, Struthanthus, and Phthirusa; see explanations in those genera.
At many points in my past taxonomic work, I have been held back by the dearth of illustrations, and I have tried to do something about that where possible. The listings of accepted species below are followed by citations of published illustrations. This iconography is scarcely intended to be exhaustive; my purpose, rather, has been to refer to the most helpful and generally available illustrations. A few illustrations are listed that have special nomenclatural significance. In addition to the illustrations here cited, the reader is also referred to those in Tropicos, the Field Museum of type photographs, and the Phoradendron type photographs in Trelease (1916); all of these, however, need to be used critically. I might add that the originals of the majority of my own illustrations are preserved in the Hunt Institute for Botanical Documentation, Carnegie Mellon University, Pittsburgh.
The present study covers all of North and South America, including the Caribbean.
Note. A troubling feature in some citations which follow involves combinations of generic names and specific epithets which are not actually made by authors in the past even though there can be little or no doubt of their intentions. A good example is seen in Eichler's (1868) work where, on p. 134i, he lists under the heading of Phthirusa a number of specific epithets but does not actually combine them. No one can doubt that Eichler placed those species in his genus Phthirusa (now largely known as Passovia), but a narrow application of Art. 33 of the International Code of Botanical Nomenclature would prescribe abandonment of Eichler's authorship. Other genera in the same work provide further instances, as do Van Tieghhem's many publications. In actual fact, Art. 33 speaks of allowable exceptions that appear completely compatible with the above examples. I am therefore accepting such combinations where, in my opinion, there is no doubt as to what the author had in mind.
Estimated species numbers in neotropical genera
Total number of known genera: 26; number of speciesi: ca. 725.
Note. It has frequently been stated that Loranthaceae consists primarily of large-flowered, ornithophilous species. This is emphatically not true in the New World, where this group has about 132 species, the small-flowered assemblage nearly 170 species (both counts exclude Gaiadendron, Notanthera, and Tripodanthus).
The insights into taxonomic matters that form the body of the present contribution have resulted from work that has stretched over some sixty years. The roster of colleagues who have assisted me in biographical and taxonomic matters over that period would fill many pages, and I must resign myself to a general acknowledgement; I cannot imagine what I would have done without such generous sharing of information and facilities. Nevertheless, I would be amiss if I did not single out two people who, through their unstinting help, have made my professional life much richer and easier than it would have been without them. Christine Anderson, through her wise and efficient counsel, has been a constant source of essential information, having carried me through five complex generic monographs. The late Bill Anderson has steered me through innumerable turbulent nomenclatural waters. Many staff members at the Missouri Botanical Gardens, both in St. Louis and in the field, have also been very helpful over the years. Beyond the people with whom I have been in direct contact are the uncountable collectors whose gatherings, often made under trying and even dangerous conditions, ultimately have laid the basis for the insights that have come to me. To all who have assisted, knowingly or not, I owe an enormous debt of gratitude. Without the half-century of uninterrupted financial support from the Natural Sciences and Engineering Research Council of Canada, the work here summarized could not have been carried out.