Molecular phylogeny of the Magnoliaceae: the biogeography of tropical and temperate disjunctions

Abstract

The boreotropical flora concept suggests that relictual tropical disjunctions between Asia and the Americas are a result of the expansion of the circumboreal tropical flora from the middle to the close of the Eocene. Subsequently, temperate species diverged at high latitudes and migrated to other continents. To test this concept, we conducted a molecular phylogenetic analysis (using cpDNA) of the Magnoliaceae, a former boreotropical element that currently contains both tropical and temperate disjuncts. Divergence times of the clades were estimated using sequences of matK and two intergenic regions consisting of psbA-trnH and atpB-rbcL. Results indicate the tropical American section Talauma branched first, followed by the tropical Asian clade and the West Indies clade. Within the remaining taxa, two temperate disjunctions were formed. Assuming the temperate disjunction of Magnolia acuminata and Asian relatives occurred 25 mya (late Oligocene; based on seed fossil records), section Talauma diverged 42 mya (mid-Eocene), and tropical Asian and the West Indies clades 36 mya (late Eocene). These events correlate with cooling temperatures during the middle to late Eocene and probably caused the tropical disjunctions.

Phylogenetic and biogeographic complexity of Magnoliaceae in the Northern Hemisphere inferred from three nuclear data sets

“…However, many clades were weakly supported and the relationships among these clades remained unclear. Other molecular studies produced similar results (e.g., Azuma et al, 2000Azuma et al, , 2001Azuma et al, , 2004Ueda et al, 2000).…”

“…Molecular phylogenetic studies on Magnoliaceae have been conducted using chloroplast data (e.g., Qiu et al, 1995a, b;Azuma et al, 1999Azuma et al, , 2001Azuma et al, , 2004Shi et al, 2000;Kim et al, 2001;Wang et al, 2006). One of the first important findings from molecular evidence was the polyphyly of Magnolia section Rhytidospermum, with the North American Magnolia tripetala closely related to the Asian counterparts, rather than to M. macrophylla, or M.…”

“…Except for the very distinct Liriodendroideae (including only Liriodendron with two species), taxonomists have long debated over the classification of Magnolioideae due to a paucity of phylogenetically useful characters (Dandy, 1927(Dandy, , 1978aLaw, 1984Law, , 1996Qiu et al, 1995a, b;Jobes, 1998;Nooteboom, 1985Nooteboom, , 1998Chen and Nooteboom, 1993;Azuma et al 1999Azuma et al , 2001Kim et al, 5 2001;Sun and Zhou, 2004;Xu and Rudall, 2006). Most recently, a new classification for Magnolioideae was proposed by Figlar and Nooteboom (2004) based on the chloroplast phylogenetic results and morphological re-examinations (also see Figlar, 2006).…”

Magnolia sulawesiana described, and a key to the species of Magnolia (Magnoliaceae) occurring in Sulawesi

“…Elmerrillia taxa to be embedded within the Michelia s.str. clade (Kim et al 2001, Nie et al 2008, Azuma et al 2001) rather than forming a separate subclade. Thus, the subsectional status for this group is now in doubt.…”

“…The family has been thoroughly studied in Malesia in comparison with many other tree families (Keng 1978, Nooteboom 1985, 1987, 1988, Kim et al 2001. Taxonomic and phylogenetic studies using both morphological (Keng 1978, Figlar 2000, Li & Conran 2003 and molecular data (Shi et al 2000, Azuma et al 2001, Kim et al 2001, Nie et al 2008) have challenged traditional generic concepts and relationships and modified the positions and circumscriptions of many taxa within the subfamily Magnolioideae. As a result, former segregate genera like Mang lietia, Michelia and Elmerrillia have been reduced to taxa at infrageneric level in a broadened Magnolia (Figlar & Nooteboom 2004) reflecting phylogenetic relationships.…”