Biosystematic Studies in the Genus Thelypteris Section Cyclosorus
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BICSYSTEMTIC STUDIES IK THE GENUS THELYPTERI3 SECTION CYCLC3CHUS ^y Alan Re id Smith A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY Major Subject: Fiant Taxonomy Approved : Signature was redacted for privacy. In Charge of Major Work Signature was redacted for privacy. Head of Major Department Signature was redacted for privacy. of Graduate College Iowa State University Ames, Iowa 1969 70-7739 SMITH, Alan Reid, 1943- BIOSYSTEMATIC STUDIES IN THE GENUS THELYPTERIS SECTION CYCLOSORUS. lowa State University, Ph.D., 1969 Botany University Microfilms, Inc., Ann Arbor, Michigan THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED iii Thelypter is cretacea Thelypteris dentata 1^0 Thelypteris extensa 157 Thelypteris invisa var. invisa l6l Thelypteris invisa var. aeauatorialis Thelypteris invisa var. peropopon 169 Thelypteris invisa var. Icunzeana 173 Thelypteris invisa var. pallescens 1/6 Thelypteris normalis 177 Thelypteris ovata var. ovata 184 Thelypteris ovata var. lindheimeri l89 Thelypteris parasitica 193 Thelypteris patens var. patens 19^ Thelypteris patens var. lanosa 201 Thelypteris patens var. scabriuscula 202 Thelypteris puberula var. puberula 206 Thelypteris puberula var. sonorensis 211 Thelypteris quadrannularis var, auadrar;r-u1 aris 214 Thelypteris quadrangular is var. incoiistans 221 Thelypteris quadrangularis var. versicolor 224 Thelypteris serra 228 Thelypteris totta var. totta 233 Thelypteris totta var. hirsuta 238 Thelypteris tuerckheiaii 240 Hybrids 244 Thelypteris au^escens X norinalis 244 Thelypteris aurescens X ova ta 245 Thelypteris cretacea X normal is 245 Thelypteris invisa -var. geroposcon X n-jcerv-lr> 245 Thelypteris invisa X serra 246 Thelypteris nornaiis X ovata 246 Thelypteris normal is X quadranprular is 246 Thelypteris normal is X serra 247 SUMMARY 248 LITERATURE CITED 250 ACKNOWLEDGMENTS ?60 APPENDIX A: TAXA EXCLUDED FROM TREATMENT 262 APPENDIX B: TAXA OF UNCERTAIN STATUS 267 APPENDIX C: SELECTED SPECIMENS EXAMINED 278 1 INTRODUCTION The genus Thelypteris sensu lato is composed of nearly 1000 species in all tropical and subtropical regions of the earth. Aside from the many nomenclatural problems in this genus, there are taxonomic difficulties in the various sub groups. Such a subgroup is the section Cyclosorus of Morton (1963). Thelypteris section Cyclosorus is one of the larger groups within the genus and numbers perhaps 300 species according to Copeland (19^7). Within the section, the New World species comprise a group of fewer than 20 species. It was conceded to be a very natural group by Christensen (1913) in his monograph of Dryopterls, under which Thelypteris was formerly submerged. Christensen's treatment is basically a good one, but the problems he found prompted him to state that "The subgenus [Cyclosorus] is as a whole the most difficult to deal with." As Christensen recognized, the chief problems encountered in this group are the extreme variability in the species and the large number of forms which are seemingly intermediate between species. Since Christensen's monumental work, several new species have been named and hybrids have been suggested by several authors to account for some of the intermediates. Robert and Edward St. John, avid collectors of Florida ferns during the 1930's, described numerous new species. Although not solving 3 METHODS AND MATERIALS Herbaria; Many of the observations presented here are based on the study of nearly 4,000 specimens on loan from various herbaria. I am grateful to those curators who so kindly made these specimens, as well as types and photographs, available for examination. Since most of the species under consideration are very common and have been widely collected, it was considered sufficient for the purpose of this study to examine material from only a few of the larger herbaria in the United States. Listed below, using the standard abbreviations of Lanjouw and Stafleu ilSGk) , are the herbaria from which specimens were borrowed. The University of Mississippi, which did not have an entry, is indicated by the abbreviation MISS. ISC - Iowa State University, Ames, Iowa MICH - University of Michigan, Ann Arbor, Michigan MISS - University of Mississippi, University. Mississippi MO - Missouri Botanical Garden, St. Louis, Missouri NY - New York Botanical Garden, New York, New York US - United States National Museum, Washington, D.C. Field collections; During the fall of 1966, I made a collecting trip to northern and central Florida to procure pressed specimens, living plants and preserved material for cytological examination. Pieces of fertile pinnae were fixed in either Newcomer's solution (Newcomer, 1953) or in 3:1 4 absolute alcohol:acetic acid, but material preserved in the field resulted in rather poor cytological preparations, possibly because of a lack of refrigeration. A return trip was made to southern Florida in November, 1967. Both pressed specimens and living rhizomes were again collected and brought back for study. Additional collections were made in Costa Rica while I was participating in a course on the biology of tropical pterldophytes (Nickel, 1967). Greenhouse culture: Brief mention should be made of the adaptability of these plants to greenhouse conditions. The living rhizomes brought back established themselves quickly in a 3:1 mixture of soil and sand. In a few instances small amounts of peat or ground limestone rock were added to the potting mixture, without visible effects on the growth of the plants. Although they are able to grow quic^ well under nearly full insolation, most plants responded with even more luxurious growth when the light intensity was reduced with fine mesh screening and whitewashing of the greenhouse panels. Many of the plants collected in the field were sterile; under greenhouse conditions, however, nearly all material soon became fertile. This is possibly a reaction to the increased light intensity, since decreased fertility was noted in many greenhouse plants during the winter. This photoperiodic response does not seem to apply to the more weedy species. Unlike most ferns, the species of sect. Cyclosorus do exceptionally well under alkaline conditions. This was 5 fortunate because the hardness of the water furnishing the greenhouses Is approximately 38^ ppm (including 98 ppm Ca and 35 ppm Mg) with a pH of 8.1. This rather high alkalinity makes it nearly impossible to culture many other ferns. Most of the species can tolerate low humidity and high temperatures for at least short periods of time. However, young croziers and pinnae are damaged after several hours under such conditions. Mature fronds can withstand much longer periods of desiccation. Anatomical preparations: Leaf segments were cleared in 5^ aqueous sodium hydroxide for several days, with final clear ing in a 20^ solution of Clorox followed by chloral hydrate. Specimens were stained using the tannic acid-ferric chloride method of Foster (193^) and mounted in either piccolyte or diaphane. Spores were mounted in 85^ lactic acid which pro duced partial clearing when heated. Cytology: All of the cytological observations presented in this paper were made from plants established in the green house. Pinnae were fixed in either 3-1 absolute alcohol: acetic acid or in the fixative suggested by Newcomer (1953)• Preparations were stained with aceto-carmine according to the process described by Kanton (1950) ^nd squashed as flat as possible. With the exception of a single count made from a somatic cell (probably a tapetal nucleus), all chromosome counts were made from sporogenous cells undergoing me lotie division. 6 After drawing the best figures, all slides were made permanent. Initially the carbon dioxide freezing technique of Bowen (195^) was used but many good meiotic figures were lost. The method which ultimately gave the best results involved rinsing underneath the ccverslip with ^5^ acetic acid until excess stain was removed, then displacing the acetic acid-water solution with either absolute ethyl alcohol or 3:1. The slide was then ringed with diaphane and allowed to dry. Measurements: A Bausch and Lomb dissecting microscope equipped w5th a micrometer disk graduated to 0.1 mm was used to measure selected morphological characters of the various species. Many of the measurements are in the form of ranges of variation with the extremes indicated in parentheses, as in "pinnae (4) 5-9 (11) cm long." This means that the majority of specimens had pinnae from 5-9 cm long, with a minimum of 4 cm and a maximum of 11 cm. Measurements requiring greater magnllication were made using a Leitz compound microscope and an ocular micrometer. Drawings: Drawings of cytological figures, epidermis, spores, and sporangia were made with the aid of a Zeiss drawing apparatus. Those of gametophytes were made using a Leitz drawing apparatus. Scales were drawn with the aid of a Bausch and Lomb microprojector. Photographs: Cytological preparations were photographed using a Leitz Orthomat microscope and camera. Photographs of species habit were made with a Pentax-SV camera. Those of the 7 upper and lower surfaces of individual pinnae were made with a Leica M2 camera and Leitz Macro-dia apparatus. With the cytological preparations, Dupont Cronar film was exposed for 105-120 seconds and developed in Kod.ak D-19 for approximately three minutes. All other photography was done using Panatomic-X film and standard photographic techniques. Distribution: The distributions of the various species and varieties given in the taxonomic revision are probably incomplete, as only a limited number of herbaria were sampled. I have not relied on locality records from the literature, since the frequency of misidentification in this group is rather high. Localities were located with the help of the "National Geographic Atlas of the World" (C-rosvenor, 1966) and also the "Index to ?Iap of Hispanic America" (Hanson, 19^5) with its accompanying maps. In a few instances, local boundaries have been changed relatively recently, e.g., the provinces in the Dominican Republic. In these instances I have followed the boundaries as Indicated in the references above.