Evolution of the eastern Asian–North American biogeographic disjunctions in ferns and lycophytes

Abstract

This paper reviews 31 groups in ferns and lycophytes hypothesized to show eastern Asian-North American disjunctions. Fourteen lineages have been supported by recent phylogenetic evidence: Lycopodium nikoense and Lycopodium sitchense; Isoëtes asiatica and the clade of the North American species complex closely allied to I. maritima; Osmundastrum cinnamomeum; Osmunda claytoniana; the Adiantum pedatum complex; the Cryptogramma acrostichoides complex; Diplaziopsidaceae; Cystopteris chinensis and the Cystopteris bulbifera clade; Asplenium rhizophyllum and Asplenium ruprechtii; diploid Phegopteris; Onoclea sensibilis; the Polypodium appalachianum clade; and the Polypodium glycyrrhiza clade. Phylogenetic and/or cytological evidence did not support the biogeographic disjunctions in six cases: (1) Isoëtes asiatica and I. truncata; (2) Botrychium ternatum; (3) Thelypteris beddomei and T. nipponica-Thelypteris noveboracensis and T. nevadensis; (4) Thelypteris glanduligera and Thelypteris. japonica-T. simulata; (5) Woodwardia japonica and W. virginica; and (6) Woodwardia orientalis and Woodwardia fimbriata. Both vicariance and dispersal have been suggested to be the mechanisms for the formation of the disjunct pattern; and the Beringian region has been an active pathway for the migration of ferns and lycophytes between Asia and North America. Disjunctions of ferns and lycophytes reviewed here have been dated in the Tertiary, and are similar to the ages of eastern Asian-North American disjunctions in seed plants, supporting the close biogeographic co-diversification of ferns and seed plants. Future studies are needed to estimate divergence times and reconstruct biogeographic events in a broad phylogenetic framework, and to test the morphological stasis hypothesis in disjunct ferns and lycophytes.

Intercontinental disjunctions between eastern Asia and western North America in vascular plants highlight the biogeographic importance of the Bering land bridge from late Cretaceous to Neogene

“…The eastern Asian–western North American disjunct pattern seems heterogeneous with several subpatterns, such as (1) relicts of the Tertiary boreotropical flora; (2) relicts of the Madrean‐Tethyan elements; and (3) some more recent disjuncts formed since the late Neogene. Northeastern Asian–Northwestern North American connections seem to be common in flowering plants and ferns with the pattern (also see Xiang et al, ). Coniferous disjunctions may have involved the Qinghai‐Tibetan Plateau of eastern Asia, where coniferous forests are well preserved (Wen et al, ).…”

“…The migration and dispersal events have resulted in complex biogeographic relationships and there is a high level of similarity of the modern Beringian flora with several shrubby and herbaceous species occurring on both sides of the Bering Strait. The pattern is shared by several fern taxa (Xiang et al, ). The relationships between Betula ermanii Cham.…”

“…The eastern Asian–North American disjunct examples in ferns and lycophytes have been recently reviewed by Xiang et al (). Although the earliest fossil record of several families can be recognized well back into the Mesozoic (Skog & Hill, ), the ages of divergence between eastern Asia and North America were dated primarily to be in the Neogene and some in the Paleogene similar to many reported ages for seed plants (Wen et al, ; Xiang et al, ).…”

Phylogenetic relationships of Neotropical lady ferns (Athyriaceae), with a description of Ephemeropteris, gen. nov.

“…Mackinnoniana are thought to have migrated to the New World much more recently. Testo & Sundue () estimated the age of the clade as late Tertiary (6.5 Ma), which is compatible with a Beringian‐origin hypothesis (Xiang & al., ; Wen & al., ). A migration during this time would require some degree of cold tolerance (Tiffney & Manchester, ).…”

Fern and lycopod spores rain in a cloud forest of Hidalgo, Mexico

“…Fern spores in the air have been previously reported at 15 m (Njokuocha 2006), at 18 m (Haratym et al 2014), and at 21 m height (Caulton et al 2000). The presence of spores at these heights above soil may illustrate the high dispersal potential of ferns and may explain some disjunct distribution patterns in these groups (Xiang et al(2015). Despite the absence of sporophytes, some allochthonous taxa had high daily spore densities (154 spores m -2 in Alsophila firma (Baker) D.S.…”