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: sorang@kahaku.go.jp

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 (inLeptopteris and Todea), and Asian (in Osmunda subgenus Plenasium). Osmunda regalis is worldwide 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 Osmundastrum cinnamomeum and Osmunda claytoniana. The Southern Hemispheric pattern is shared by thesister genera Leptopteris and Todea, but it does not necessarily support a hypothesis for the Southern Hemispheric origin of the whole family.
Key words : Distribution, Osmundaceae, Leptopteris, Osmunda, Osmundastrum, Plenasium,
Todea.

Introduction
Osmundaceae are a family of monilophytesthat is intermediate between eusporangiate andleptosporangiate ferns, or basal in the leptosporangiate ferns, in having massive sporangia developed from one or two initials. The osmundaceous ferns appeared in the Permian or possiblyin the Carboniferous, and diversified and thrived
in the Mesozoic (Tidwell and Ash, 1994;
Collinson, 1996; Skog, 2001). Compared to theCretaceous or later origin of most of the higher
ferns or “polypods” s. l. following the diversification of angiosperms (Schneider et al., 2004), theprimitive Osmundaceae are estimated by a molecular analysis to have arisen 323 million years
ago (mya), as long ago as in the MississippianPennsylvanian of the Carboniferous (Pryer et al.,2004). Yatabe et al. (1999) estimated that thefamily’s deepest divergence time of Osmundastrum cinnamomeum from the rest was 294 myaor the Late Pennsylvanian, and the divergencetime of a clade of Leptopteris and Todea from
Osmunda including O. claytoniana (subgenus
Claytosmunda) was 210 or 206 mya, or the Late

Triassic (Yatabe et al., 1999; Pryer et al., 2004).
The estimated divergence time of Osmunda s. s.
and Plenasium (Osmunda subg. Plenasium) is
150 mya or the Late Jurassic (Yatabe et al.,1999). Therefore, the distributions of the generaand subgenera were probably strongly influenced
by the geological and climatic changes of thepast 300 million years.
The family is small, comprising three extant
genera (four according to recent analyses) and
15–38 species (Kramer in Kubitzki, 1990; 21
species in Hewitson, 1962). It is distributed
worldwide in all major continents except for
Antarctica. This paper examines its distribution
ranges and patterns by synthesizing data fromlocal floras and examining herbarium specimens.
The distribution ranges of the family or part of it
were illustrated by Polunin (1960) and Bovrov(1967). The distributional information will be
useful to understand the phylogeny, biogeography, and evolution of the Osmundaceae.
Materials
Distribution data were obtained from examina-

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Masahiko Katotion of specimens at National Museum of Natureand Science Herbarium (TNS) and University ofTokyo Herbarium (TI), and published data inlocal floras and fossil data (Miller, 1967, 1971,
1982; Collinson, 2001).
Distribution of Genera
Comparison of the distributions of the generaand subgenera of Osmundaceae and classifications deducible from recent molecular phylogenetic analyses, shows that they are divided into
four patterns, i. e., worldwide, eastern Asian–eastern North American, Southern Hemispheric,and Asian.
Worldwide pattern
The genus Osmunda has usually been treated
to comprise three subgenera (Hewitson, 1962;
Kramer in Kubitzki, 1990). However, Yatabe etal.’s (1999) molecular phylogenetic analysis revealed that the genus is paraphyletic because
Leptopteris and Todea are nested in the genus(Fig. 1). The subgenera have sometimes beenrecognized as genera (Tagawa, 1941, 1959;
Zhang, 2006). Neither subgenus- nor genus-rank
classification is congruent with the molecular evidence. Yatabe et al. (1999) showed that Osmunda subgenus Osmundastrum, which is tradition-

ally bispecific, is also paraphyletic. In conclusion, Osmunda is divided into four clades, Osmundastrum cinnamomeum, O. (subgenus Claytosmunda) claytoniana (which has been assigned
tosubgenus
Osmundastrum),subgenus
Osmunda, and subgenus Plenasium, in addition
to a clade of Leptopteris and Todea (Yatabe etal., 1999, 2005). The six clades may be classified
at the genus rank. The clades have characteristic
distribution patterns, among which the worldwide distribution pattern is seen in subgenus Osmunda.
Subgenus Osmunda comprises three or more
species. Osmunda regalis is distributed in Europe
east to Middle East (var. regalis), northern Africa(whole plants have been assigned as var.
plumieri), tropical and southern Africa, alongwith Madagascar and adjacent islands (var.
abyssinica, var. capensis, var. oblongifolia, var.
transvaalensis), southern Asia (O. huegeliana),
and North America (var. spectabilis) throughSouth America (var. palustris) (Fig. 2). It also
occurs in the Azores and Vermuda in the Atlantic, and in Laos, which is the most eastern in
Asia (Fig. 3A). Lao O. regalis was collected forthe first time by T. Tuyama (Tuyama L57063, TI;
but identified as O. japonica) in 1957, and recollected by M. Kato et al. in 2007. The species has
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 (Polunin, 1960; Bovrov, 1967). Osmunda japonica(Fig. 3B) is distributed in eastern Asia, ranging
west to the Himalayas and south to northern
Vietnam in southeastern Asia. It is generally allopatric to O. regalis, although the two are sympatric in the Himalayas and peripatric in thenorthern parts (N Vietnam and Laos) of southeastern Asia. Osmunda lancea, an ecologicallyand morphologically specialized rheophyte, isendemic to Japan (Fig. 3C) (Imaichi and Kato,
1992). It should be noted that Franchet and Savatier (1877) recorded O. regalis with citation ofa specimen (Savatier 1608, duplicate TI), besides

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Masahiko Kato

Fig. 3. Three species of Osmunda subgenus Osmunda. A. Osmunda regalis in Laos. B, C. O. japonica (B) andO. lancea (C) cultivated in Tsukuba Botanical Garden.

O. japonica (as variety), from around Yokosuka,
Japan in their Enumeratio Plantarum. It may be
O. regalis or subdimorphic O. japonica (seebelow). Further search is necessary to reveal theexact distribution ranges of the species.
Osmunda regalis and O. japonica have beentreated as a single species, but at the varietal
rank, or as separate species (e.g. Christensen,
1906; Polunin, 1960; Bovrov, 1978; Iwatsuki,1995). The two differ mainly in leaf dimorphism:
O. regalis has subdimorphic leaves with the fertile distal half and the sterile proximal half, andDistribution of Osmundaceae

O. japonica has completely dimorphic leaves
with separate fertile and sterile leaves. However,late-growing leaves of O. japonica are occasionally subdimorphic so that there is little stable distinction between the two. Osmunda regalis happens to show dimorphism. Available molecular
data, though insufficient, may show that the two
species are hardly different (Yatabe et al., 1999),
implying a recent separation. Their historical biogeography may differ from that of Osmundastrum and Osmunda subgenus Claytosmunda withpartly similar distribution patterns (see below).
Furthermore, the rheophilous O. lancea endemic
to Japan does not differ from O. japonica at themolecular level (Yatabe et al., 1999), suggesting
the recent ecological speciation of the rheophyte.
It might be likely that the ancestral species of Osmunda diversified into regional species or entities
such as O. japonica and O. regalis var. regalis.
Further analysis will unravel the evolution andspeciation of the O. regalis complex.
East Asian–eastern North American pattern
Osmundastrum and Osmunda subgenus Claytosmunda show the disjunct distribution pattern(Fig. 1). They are characterized by having bipinnatifid leaves with oblong, adnate pinnules, bywhich they have been recognized as a taxonomic
group (Hewitson, 1962). Both Osmundastrum
cinnamomeum and Osmunda (subgenus Claytosmunda) claytoniana prefer damp grounds andoccasionally grow sympatric. However, they are
distinct in leaf dimorphism: the leaves are subdimorphic with contracted fertile pinnae borne in
the middle in Osmunda claytoniana, while completely dimorphic with separate fertile and sterileleaves in Osmundastrum cinnamomeum. Osmunda claytoniana is distributed in eastern Asia andeastern North America (Fig. 4), typically representing the eastern Asian–eastern North American pattern of ferns (Li, 1954; Kato and Iwatsuki,1983). Osmundastrum cinnamomeum also showssuch a pattern, but it extends south to Central andSouth Americas (Fig. 5). It may be likely that theformerly continuous Northern Hemispheric distribution range was separated into the two distant85

ranges, associated with extinction in intervening
regions (e.g. western North America and farnortheastern Asia) due to climate change, particularly cooling (see also fossil data below and Fig.
6).
The eastern Asian–eastern North American
populations of each of the two species havesometimes been segregated at the infraspecificrank: Asian Osmundastrum cinnamomeum wasnamed as var. fokienensis or var. asiatica (Ching,
1959; Tagawa, 1959) and Asian Osmunda claytoniana was segregated as var. vestita (Wall.)Milde (Tagawa, 1941). Using molecular data,
Yatabe et al. (1999) estimated that the divergencetime is 35 mya (Eocene) and 25 mya (Oligocene)in Osmundastrum cinnamomeum and Osmunda
claytoniana, respectively. In these epochs, eastern Asia and North America were dominated bymore or less continuous, warm/cool andcool/cold temperate vegetations (Willis andMcElwain, 2002). As fossils of Osmundastrum
cinnamomeum are recorded from the upper Middle Miocene of Hokkaido and Miocene–Plioceneof Washington in northwestern USA (Miller,
1967; Yatabe et al., 1999), where extant plants do
not occur, it is likely that extinction during the
Neogene caused the disjunct distribution pattern
independently in the two species. Similar disjunct biogeographies are reviewed for a variety of
seed plants by Donoghue et al. (2001), Tiffney
and Manchester (2001), and Wen (2001).
Southern Hemispheric pattern
Leptopteris with ca. five species is distributed
in New Zealand, eastern Australia, the southern
Pacific, New Guinea, and the Moluccas (Seram
Island; Kato, 1989) (Fig. 5). This fern is characterized by the thin, finely dissected leaves withsuperficial sori. Todea of two species has thick,bipinnate, monomorphic leaves with similarly superficial sori. It is disjunct in Australasia andAfrica (Fig. 4). Todea barbara occurs in New
Zealand, eastern and southeastern Australia, anddisjunctly in southern Africa, while T. papuanaHennipm. occurs in Papua New Guinea. As suggested by comparative morphology (Hewitson,

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Masahiko Kato

Fig. 4. Distribution ranges of Osmunda (subgenus Claytosmunda) claytoniana (CL), Osmunda subgenus Plenasium (PL), and Todea (TO).

1962), the two genera form a monophyletic clade(Fig. 1; Yatabe et al., 1999). Pryer et al. (2004)
estimated the divergence time of Leptopteris andTodea to be 206 mya, based on fossil data of Osmundacaulis, which is suggested to be a memberof the osmundaceous crown group (Tidwell andAsh, 1994; Collinson, 1996; but see Yatabe et al.,1999). In the Late Triassic and Early Jurassic(206–180 mya), the Gondwana was a supercontinent before break and drift (Willis and McElwain, 2002). There are two possibilities of historical biogeographies for Leptopteris and Todea.
One is that, when the genera diverged, they occurred in continuous distribution ranges and retained the similar Southern Hemispheric distribution patterns even after land separation of Australia and New Zealand from Africa. The other isthat the distributional similarity is a convergenceafter different histories.
Fossil data suggested the origin of the family
in the Southern Hemisphere followed by migration to the Northern Hemisphere (Tidwell andAsh, 1994; Skog, 2001). However, it is inconsis-

tent with the phylogenetic relationship of the extant Leptopteris and Todea, which does not suggest that this pattern is an ancestral character
state (plesiomorphic).
Asian pattern
Osmunda subgenus Plenasium of several
species is monophyletic and characterized by thesimply pinnate leaves with linear-lanceolate pinnae and remarkably contracted fertile pinnae
under the middle of the leaves (Fig. 1; Hewitson,
1962; Yatabe et al., 1999). It is the only member
showing the tropical Asian distribution pattern
among the genera and subgenera of Osmundaceae. It is distributed from temperate Asia
(southern Japan) west to eastern Himalaya andsouth to middle and western Malesia (the Philippines, Malaysia and Indonesia), and also occurs
in southern India and Sri Lanka (Fig. 4). This
subgenus occupies southeastern Asia, where noother members are distributed. Thus, there is a
distributional segregation between the subgenus
Plenasium and all others, although the subgenus

Distribution of Osmundaceae

Fig. 5.

87

Distribution ranges of Osmundastrum cinnamomeum (CI) and Leptopteris (LE).

is phylogenetically close to subgenera Osmunda
and Claytosmunda (Yatabe et al., 1999, 2005).
Ancient distributions
The Late Triassic Osmunda claytoniites isrecorded from Victoria Land of Antarctica(Phipps et al., 1998). Extinct genera from theTriassic to Cretaceous of various localities
throughout the world including South America,
western Canada, southern Africa and India, e.g.
Osmundacaulis, formed distinct phylogenetic lineages in the family or had uncertain affinities
with the extant members (Boureau [ed.], 1970;
Tidwell and Ash, 1994). The distributions of permineralized stem and compressed leaf fossils assigned to Osmunda from a long range of the Tertiary and a few from the Cretaceous (Miller,
1967, 1971, 1982) are shown in Fig. 6. They are
distributed widely in the Northern Hemisphere.
Osmunda is characterized as a member of the Paleocene to Eocene circum-Arctic flora(Collinson, 2001; Wang et al., 2006). Many of
the Osmunda fossils are recorded outside the present range, e. g. in western and northwestern

North America, suggesting the wider distribution
range of the genus or related ferns in the Coenozoic (Collinson, 2001). In situ osmundaceous
spores were recorded since the Late Triassic (vanKonijnenburg-van Cittert, 2000), but because thespore morphology does not greatly vary among
the genera, it is not useful to determine the distribution of Osmunda or close relatives.
Conclusion and Perspective
The molecular phylogeny of extant species andfossil data imply that the four distribution patterns recognizable for the extant Osmundaceae
are the result of the distributional and evolutionary changes of the family that happened in a longrange of geological times from the Permian. It isnoted that Leptopteris and Todea of the sameclade show similar distribution patterns, possibly
due to common ancestry. However, available phylogenetic and geographic data of the extant members do not necessarily support the above paleobotanical hypothesis for the Southern Hemisphericorigin of the family. Osmunda regalis and O.
japonica, closely related to each other, are gener-

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Masahiko Kato

Fig. 6. Places (indicated by solid circles) where fossils assigned to Osmunda were collected, based on Miller(1967, 1971, 1982), Phipps et al. (1998), Collinson (2001), and Wang et al. (2006). Note that their strata arevarious. Places of fossils 2, 5, 7, 19, 24, and 26 are not exact. Solid lines indicate the distribution ranges ofextant Osmunda. Figures are in order of earlier to later fossils. Permineralized fossils are marked by asterisks
and compressed leaf fossils are unmarked. 1, O. claytoniites from Upper Triassic of Victoria Land, Antarctica; 2, O. petiolata from Lower Cretaceous of Greenland; 3, O. asuwensis from Upper Cretaceous of Japan; 4,
O. major from Upper Cretaceous of Colorado, USA; 5, O. delawarensis from Upper Cretaceous of eastern
USA; 6, O. montanensis from Upper Cretaceous of Montana, USA; 7, O. oebergiana from Upper Cretaceousof Greenland; 8, O. haldemiana from Cretaceous of Germany; 9, O. hollicki from Cretaceous of Colorado,
USA; 10, O. arnoldii* from Paleocene (65–54.8 mya) of North Dakota, USA; 11, O. plumosa* from Paleocene of North Dakota, USA; 12, O. precinnamomea* from Paleocene of North Dakota, USA; 13, O. macrophylla from Paleocene of Alberta, Canada; 14, O. dowkeri* from Eocene (54.8–33.7 mya) of United Kingdom; 15, O. oregonensis* from Eocene of Oregon, USA; 16, O. bromeliaefolia from Eocene of Japan; 17, O.
regalis from Eocene of Japan; 18, O. doroschkiana from Oligocene (33.7–23.8 mya) of Alaska, USA; 19, O.
occidentalis from Oligocene of western USA; 20, O. spetsbergensis from Upper Tertiary (Eocene?) of Spitsbergen; 21, O. cinnamomea* from Miocene (23.8–5.3 mya) of Washington, USA; 22, O. cf. claytoniana from
Miocene of Idaho, USA; 23, O. wehrii* from Miocene of Washington, USA; 24, O. affinis from Miocene ofwestern USA; 25, O. iliaensis* from Miocene–Pliocene of Hungary; 26, O. strozzii from Miocene–Plioceneof Europe; 27, O. schemnicensis from Miocene–Pliocene of Germany; 28, O. nathorsii* from Pliocene(5.3–1.8 mys) of Spitsbergen; 29, O. bilinica from Pliocene of Germany.

ally allopatric, although they are sympatric in the
Himalayas and peripatric in southeastern Asia.
The geographical history and speciation of thespecies remains uncertain.

Acknowledgments
I thank A. Ebihara and Y. Yatabe-Kakugawa
for useful comments to the manuscript, and director, the University of Tokyo Herbarium (TI)
for allowing me to examine specimens, and K.
Uemura and T. Yamada for providing copies ofreferences. This study was in part supported by aDistribution of Osmundaceae

Grant-in-Aid for Scientific Research from theJapan Society for the Promotion of Science.

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