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.

The internal transcribed spacers and the 5.8S coding region of nuclear ribosomal DNA were sequenced and analyzed to address questions of generic relationships in Winteraceae. The molecular data generated a single tree that is congruent with one based on morphological data. The sequences of ITS 1 in the family range from 235 to 252 bases in size and of ITS 2 from 213 to 226 bases. The size of the 5.8S coding region is 164 bases. The range of ITS 1 and ITS 2 sequence divergence between pairs of genera within Winteraceae is relatively low in comparison to other plant families. Two types of ITS 1 and ITS 2 sequences were observed in the same individual for some taxa. Sequence variations between the two arrays are 4.7%–6.3% for ITS 1 and 5.1%–7.0% for ITS 2. Both arrays of sequences, however, generate the same phylogenetic relationships. Rates of nucleotide substitutions for the internal transcribed spacers are 3.2–5.2 × 10‐10 substitution per site per year estimated in ITS 1 and 3.6–5.7 × 10‐10 in ITS 2.

The first three branches of the angiosperm phylogenetic tree consist of eight families with ∼201 species of plants (the ANITA grade). The oldest flower fossil for the group is dated to the Early Cretaceous (115-125 Mya) and identified to the Nymphaeales. The flowers of extant plants in the ANITA grade are small, and pollen is the edible reward (rarely nectar or starch bodies). Unlike many gymnosperms that secrete "pollination drops," ANITA-grade members examined thus far have a dry-type stigma. Copious secretions of stigmatic fluid are restricted to the Nymphaeales, but this is not nectar. Floral odors, floral thermogenesis (a resource), and colored tepals attract insects in deceit-based pollination syndromes throughout the first three branches of the phylogenetic tree. Self-incompatibility and an extragynoecial compitum occur in some species in the Austrobaileyales. Flies are primary pollinators in six families (10 genera). Beetles are pollinators in five families varying in importance as primary (exclusive) to secondary vectors of pollen. Bees are major pollinators only in the Nymphaeaceae. It is hypothesized that large flowers in Nymphaeaceae are the result of the interaction of heat, floral odors, and colored tepals to trap insects to increase fitness.