Bull. Natl. Mus. Nat. Sci., Ser. B, 33(3·4), pp. 81–90, December 21, 2007 Distribution of Osmundaceae Masahiro Kato Department of Botany, National Museum of Nature and Science, Amakubo, Tsukuba 305–0005, Japan E-mail: [email protected] Abstract The distributions of Osmundaceae are synthesized based on phylogenetic relationships. The distribution patterns may reflect the long evolutionary and geographic history of the family. They are divided into worldwide (in Osmunda subgenus Osmunda), eastern Asian–eastern North American (in Osmundastrum and Osmunda subgenus Claytosmunda), Southern Hemispheric (in Leptopteris and Todea), and Asian (in Osmunda subgenus Plenasium). Osmunda regalis is world- wide while the closely related O. japonica is eastern Asian, and both occur in the Himalayas. The eastern Asian–eastern North American pattern is seen in each of the remotely related Osmundas- trum cinnamomeum and Osmunda claytoniana. The Southern Hemispheric pattern is shared by the sister genera Leptopteris and Todea, but it does not necessarily support a hypothesis for the South- ern Hemispheric origin of the whole family. Key words :Distribution, Osmundaceae, Leptopteris, Osmunda, Osmundastrum, Plenasium, Todea. Triassic (Yatabe et al., 1999; Pryer et al., 2004). Introduction The estimated divergence time of Osmunda s. s. Osmundaceae are a family of monilophytes and Plenasium (Osmunda subg. Plenasium) is that is intermediate between eusporangiate and 150 mya or the Late Jurassic (Yatabe et al., leptosporangiate ferns, or basal in the leptospo- 1999). Therefore, the distributions of the genera rangiate ferns, in having massive sporangia de- and subgenera were probably strongly influenced veloped from one or two initials. The osmunda- by the geological and climatic changes of the ceous ferns appeared in the Permian or possibly past 300 million years. in the Carboniferous, and diversified and thrived The family is small, comprising three extant in the Mesozoic (Tidwell and Ash, 1994; genera (four according to recent analyses) and Collinson, 1996; Skog, 2001). Compared to the 15–38 species (Kramer in Kubitzki, 1990; 21 Cretaceous or later origin of most of the higher species in Hewitson, 1962). It is distributed ferns or “polypods” s. l. following the diversifica- worldwide in all major continents except for tion of angiosperms (Schneider et al., 2004), the Antarctica. This paper examines its distribution primitive Osmundaceae are estimated by a mole- ranges and patterns by synthesizing data from cular analysis to have arisen ϳ323 million years local floras and examining herbarium specimens. ago (mya), as long ago as in the Mississippian- The distribution ranges of the family or part of it Pennsylvanian of the Carboniferous (Pryer et al., were illustrated by Polunin (1960) and Bovrov 2004). Yatabe et al. (1999) estimated that the (1967). The distributional information will be family’s deepest divergence time of Osmundas- useful to understand the phylogeny, biogeogra- trum cinnamomeum from the rest was 294 mya phy, and evolution of the Osmundaceae. or the Late Pennsylvanian, and the divergence time of a clade of Leptopteris and Todea from Materials Osmunda including O. claytoniana (subgenus Claytosmunda) was 210 or 206 mya, or the Late Distribution data were obtained from examina- 82 Masahiko Kato tion of specimens at National Museum of Nature ally bispecific, is also paraphyletic. In conclu- and Science Herbarium (TNS) and University of sion, Osmunda is divided into four clades, Os- Tokyo Herbarium (TI), and published data in mundastrum cinnamomeum, O. (subgenus Clay- local floras and fossil data (Miller, 1967, 1971, tosmunda) claytoniana (which has been assigned 1982; Collinson, 2001). to subgenus Osmundastrum), subgenus Osmunda, and subgenus Plenasium, in addition to a clade of Leptopteris and Todea (Yatabe et Distribution of Genera al., 1999, 2005). The six clades may be classified Comparison of the distributions of the genera at the genus rank. The clades have characteristic and subgenera of Osmundaceae and classifica- distribution patterns, among which the world- tions deducible from recent molecular phyloge- wide distribution pattern is seen in subgenus Os- netic analyses, shows that they are divided into munda. four patterns, i. e., worldwide, eastern Asian– Subgenus Osmunda comprises three or more eastern North American, Southern Hemispheric, species. Osmunda regalis is distributed in Europe and Asian. east to Middle East (var. regalis), northern Africa (whole plants have been assigned as var. Worldwide pattern plumieri), tropical and southern Africa, along The genus Osmunda has usually been treated with Madagascar and adjacent islands (var. to comprise three subgenera (Hewitson, 1962; abyssinica, var. capensis, var. oblongifolia, var. Kramer in Kubitzki, 1990). However, Yatabe et transvaalensis), southern Asia (O. huegeliana), al.’s (1999) molecular phylogenetic analysis re- and North America (var. spectabilis) through vealed that the genus is paraphyletic because South America (var. palustris) (Fig. 2). It also Leptopteris and Todea are nested in the genus occurs in the Azores and Vermuda in the At- (Fig. 1). The subgenera have sometimes been lantic, and in Laos, which is the most eastern in recognized as genera (Tagawa, 1941, 1959; Asia (Fig. 3A). Lao O. regalis was collected for Zhang, 2006). Neither subgenus- nor genus-rank the first time by T. Tuyama (Tuyama L57063, TI; classification is congruent with the molecular ev- but identified as O. japonica) in 1957, and recol- idence. Yatabe et al. (1999) showed that Osmun- lected by M. Kato et al. in 2007. The species has da subgenus Osmundastrum, which is tradition- been divided into several regional taxa, as shown Fig. 1. Phylogenetic tree of Osmundaceae, simplified from Yatabe et al. (1999). Osmundastrum and Osmunda subgenus Claytosmunda are monotypic while the other taxa are multispecific. Distribution of Osmundaceae 83 A B Fig. 2. Worldwide distribution ranges of Osmunda subgenus Osmunda. A. Arctic polar view. B. Equatorial view. J, O. japonica; L, O. lancea; R, O. regalis. above in parentheses following the regions (Pol- northern parts (N Vietnam and Laos) of south- unin, 1960; Bovrov, 1967). Osmunda japonica eastern Asia. Osmunda lancea, an ecologically (Fig. 3B) is distributed in eastern Asia, ranging and morphologically specialized rheophyte, is west to the Himalayas and south to northern endemic to Japan (Fig. 3C) (Imaichi and Kato, Vietnam in southeastern Asia. It is generally al- 1992). It should be noted that Franchet and Sa- lopatric to O. regalis, although the two are sym- vatier (1877) recorded O. regalis with citation of patric in the Himalayas and peripatric in the a specimen (Savatier 1608, duplicate TI), besides 84 Masahiko Kato Fig. 3. Three species of Osmunda subgenus Osmunda. A. Osmunda regalis in Laos. B, C. O. japonica (B) and O. lancea (C) cultivated in Tsukuba Botanical Garden. O. japonica (as variety), from around Yokosuka, treated as a single species, but at the varietal Japan in their Enumeratio Plantarum. It may be rank, or as separate species (e.g. Christensen, O. regalis or subdimorphic O. japonica (see 1906; Polunin, 1960; Bovrov, 1978; Iwatsuki, below). Further search is necessary to reveal the 1995). The two differ mainly in leaf dimorphism: exact distribution ranges of the species. O. regalis has subdimorphic leaves with the fer- Osmunda regalis and O. japonica have been tile distal half and the sterile proximal half, and Distribution of Osmundaceae 85 O. japonica has completely dimorphic leaves ranges, associated with extinction in intervening with separate fertile and sterile leaves. However, regions (e.g. western North America and far- late-growing leaves of O. japonica are occasion- northeastern Asia) due to climate change, partic- ally subdimorphic so that there is little stable dis- ularly cooling (see also fossil data below and Fig. tinction between the two. Osmunda regalis hap- 6). pens to show dimorphism. Available molecular The eastern Asian–eastern North American data, though insufficient, may show that the two populations of each of the two species have species are hardly different (Yatabe et al., 1999), sometimes been segregated at the infraspecific implying a recent separation. Their historical bio- rank: Asian Osmundastrum cinnamomeum was geography may differ from that of Osmundas- named as var. fokienensis or var. asiatica (Ching, trum and Osmunda subgenus Claytosmunda with 1959; Tagawa, 1959) and Asian Osmunda clayto- partly similar distribution patterns (see below). niana was segregated as var. vestita (Wall.) Furthermore, the rheophilous O. lancea endemic Milde (Tagawa, 1941). Using molecular data, to Japan does not differ from O. japonica at the Yatabe et al. (1999) estimated that the divergence molecular level (Yatabe et al., 1999), suggesting time is 35 mya (Eocene) and 25 mya (Oligocene) the recent ecological speciation of the rheophyte. in Osmundastrum cinnamomeum and Osmunda It might be likely that the ancestral species of Os- claytoniana, respectively. In these epochs, east- munda diversified into regional species or entities ern Asia and North America were dominated by such as O. japonica and O. regalis var. regalis. more or less continuous, warm/cool and Further analysis will unravel the evolution and cool/cold temperate vegetations (Willis and speciation of the O. regalis complex. McElwain, 2002). As fossils of Osmundastrum cinnamomeum are recorded from the upper Mid- East Asian–eastern North American pattern dle Miocene of