Sphaeropteris

Abstract: Aim Scaly tree ferns, Cyatheaceae, are a well-supported group of mostly treeforming ferns found throughout the tropics, the subtropics and the south-temperate zone. Fossil evidence shows that the lineage originated in the Late Jurassic period. We reconstructed large-scale historical biogeographical patterns of Cyatheaceae and tested the hypothesis that some of the observed distribution patterns are in fact compatible, in time and space, with a vicariance scenario related to the break-up of Gondwana. Location Tropics, subtropics and south-temperate areas of the world. Methods The historical biogeography of Cyatheaceae was analysed in a maximum likelihood framework using Lagrange. The 78 ingroup taxa are representative of the geographical distribution of the entire family. The phylogenies that served as a basis for the analyses were obtained by Bayesian inference analyses of mainly previously published DNA sequence data using MrBayes. Lineage divergence dates were estimated in a Bayesian Markov chain Monte Carlo framework using beast. Results Cyatheaceae originated in the Late Jurassic in either South America or Australasia. Following a range expansion, the ancestral distribution of the marginate-scaled clade included both these areas, whereas Sphaeropteris is reconstructed as having its origin only in Australasia. Within the marginate-scaled clade, reconstructions of early divergences are hampered by the unresolved relationships among the Alsophila, Cyathea and Gymnosphaera lineages. Nevertheless, it is clear that the occurrence of the Cyathea and Sphaeropteris lineages in South America may be related to vicariance, whereas transoceanic dispersal needs to be inferred for the range shifts seen in Alsophila and Gymnosphaera. Main conclusions The evolutionary history of Cyatheaceae involves both Gondwanan vicariance scenarios as well as long-distance dispersal events. The number of transoceanic dispersals reconstructed for the family is rather few when compared with other fern lineages. We suggest that a causal relationship between reproductive mode (outcrossing) and dispersal limitations is the most plausible explanation for the pattern observed.

Abstract: Nearly 103 species of Sphaeropteris are distributed in tropical area, of which three species are indigenous to China. Our previous molecular study of the genus in China showed that there is an undescribed species from Guangxi province which could be originated from natural hybridization. In this study, we carried out further morphological studies on the species of Sphaeropteris in China, and assessed the status of the new species. Here, we described and illustrated the new species as S. guangxiensis Y.F. Gu & Y.H. Yan.

Abstract: The delimitation of genera and families has been a persistent problem in fern taxonomy, and the Cyatheaceae sensu stricto is no exception. Christensen (190506) adopted clearly artificial genera (Cyathea, Hemitelia, and Alsophila) based on complete (totally surrounding the sorus), partial, and absent indusia. He included Lophosoria and Metaxya in Alsophila. The latter two satellite genera are only distantly related to the major genera of the family, and nowadays are often placed in one or two families of their own. Holttum (1963) proposed a single genus Cyathea for the Flora Malesiana region with two very distinct subgenera, Sphaeropteris and Cyathea. Holttum has maintained (1981, p. 466) that the "only subdivision of the genus clearly definable is that between subgenus Sphaeropteris and the rest." This indicates that Alsophila and Cnemidaria are less distinct from Cyathea than all three are from Sphaeropteris, which is confirmed by the lack of hybrids with Sphaeropteris. In studying the species of the Flora Malesiana region, Holttum came to the fundamental conclusion, among many, that indusium type is not an important generic character, for within a few species it varies widely. Tryon (1970) divided the Cyatheaceae sensu stricto on the basis of scale characters, indusium presence or absence, and venation. He adopted the genera Sphaeropteris (scales conform), Alsophila and Nephelea (scales non-conform and setate), Trichopteris (scales non-conform and non-setate, laminae free-veined, and sori exindusiate), Cyathea (scales non-conform and non-setate, laminae freeveined, and sori indusiate), and Cnemidaria (scales non-conform and non-setate and laminae net-veined. According to Holttum and Edwards (1983, p. 179), this classification has assorted closely related species into Cyathea, Sphaeropteris, and Trichopteris. It is apparent that genera based on these characters are not natural. Working from Tryon's (1970) generic concepts, I have found it possible to define readily recognizable and coherent genera in the Cyatheaceae sensu stricto by including in Cyathea the genus Trichopteris and the New World species considered to be Sphaeropteris, except for the S. horrida group. I accept the genera Sphaeropteris, Alsophila (including Nephelea), Cyathea (including Trichopteris), and Cnemidaria. Occasional hybrids occur within Alsophila and Cyathea and between Cnemidaria and Gyathea. This is evidence of a greater degree of relationship than with Sphaeropteris, but in my opinion should not alone be the basis for adopting an inclusive Cyathea (either excluding or even including Sphaeropteris), for the characteristics of Alsophila and Cnemidaria are sufficiently different from those of Cyathea to distinguish the genera readily, and intergeneric hybrids in ferns