The Eocene North Atlantic land bridge:its importance in Tertiary and modern phytogeography of the Northern Hemisphere

A well-sampled phylogenetic analysis of the polystichoid ferns (Dryopteridaceae) suggests a complex biogeographical history involving both boreotropical migrations and recent transoceanic dispersals

“…The current biogeographical disjunctions between the Old and the New World may be better explained by a boreotropical scenario. Indeed, the Eocene-Oligocene divergence is consistent with the expansion (50-33 Ma) and then reduction (33-26 Ma) of boreotropical forest belt (Morley, 2003;Tiffney, 1985aTiffney, , 1985bWolfe, 1975). Ancestors of Phanerophlebia, Clade B and Clade C from the Old World, may have used different land bridges available in late Eocene-early Oligocene to colonize the New World (i.e., BLB and/or NALB; Manchester, 1999;Tiffney, 1985a;Tiffney and Manchester, 2001) (Table 4).…”

“…Indeed, the Eocene-Oligocene divergence is consistent with the expansion (50-33 Ma) and then reduction (33-26 Ma) of boreotropical forest belt (Morley, 2003;Tiffney, 1985aTiffney, , 1985bWolfe, 1975). Ancestors of Phanerophlebia, Clade B and Clade C from the Old World, may have used different land bridges available in late Eocene-early Oligocene to colonize the New World (i.e., BLB and/or NALB; Manchester, 1999;Tiffney, 1985a;Tiffney and Manchester, 2001) (Table 4). This hypothesis is also congruent with the biogeographical history of Central American and Andean Polystichum proposed by Driscoll and Barrington (2007) as well as McHenry and Barrington (2014), who suggested that the Neotropical clade has a northern origin, and that the Andean Polystichum lineage originated from a boreotropical Mexican ancestor.…”

“…An alternative hypothesis to the LDD scenario is linked to the history of the boreotropical regions that covered a large part of the Northern Hemisphere from the early Paleogene until the early Oligocene (Morley, 2003;Tiffney, 1985aTiffney, , 1985bWolfe, 1975). A warm climate, and existing land bridge connections (Bering Land Bridge [BLB] and North America Land Bridge [NALB]) generated a paratropical forest that spanned Eurasia and North America (Morley, 2003;Tiffney and Manchester, 2001;Tiffney, 1985aTiffney, , 1985bWolfe, 1975;Zachos et al, 2001).…”

“…A warm climate, and existing land bridge connections (Bering Land Bridge [BLB] and North America Land Bridge [NALB]) generated a paratropical forest that spanned Eurasia and North America (Morley, 2003;Tiffney and Manchester, 2001;Tiffney, 1985aTiffney, , 1985bWolfe, 1975;Zachos et al, 2001). Cooling of the climate and tectonic movements during the early Oligocene led to the fragmentation of the boreotropical belt, and the migration of paratropical elements southward to tropical refuges, such as southwest China, Southeast Asia, Central America, and Mexico (Morley, 2003;Zachos et al, 2001).…”

Diversification of the cold-adapted butterfly genus Oeneis related to Holarctic biogeography and climatic niche shifts

“…The mountains of Central Asia were free of ice since the Miocene (Kamelin, 1998;Sanmartin et al, 2001) and represented general long term refugia of temperate biota (Tiffney 1985;Chytry et al, 2012;Condamine et al, 2012). The oldest Oeneis lineages (members of the subgenus Protoeneis) and two-thirds of Oeneis diversity (19 species, Table S1) occur in the mountains of Central Asia (region B).…”