DOYLE, JAMES A.1*, HERVÉ SAUQUET2, TANYA SCHARASCHKIN1, and ANNICK LE THOMAS2. 1Evolution and Ecology, University of California, Davis, CA 95616; 2Muséum National d’Histoire Naturelle, 16 rue Buffon, 75005 Paris, France. - Phylogeny, molecular and fossil dating, and biogeographic history of Magnoliales – contrasts between Annonaceae and Myristicaceae.
Magnoliales consist of the clearly Laurasian family Magnoliaceae,
which is known back to the Cenomanian; three small groups with
apparent Southern Gondwanan distributions (Eupomatia,
Galbulimima, Degeneria); and two larger pantropical
families, Annonaceae and Myristicaceae. Phylogenetic analyses based on
morphology identified the Asian-Neotropical genus Anaxagorea as
sister to all other Annonaceae, in which basal lines are African and
South American and Asian taxa are more deeply nested. This suggested
that Annonaceae underwent an Early Cretaceous split into a Laurasian
line (Anaxagorea) and a Gondwanan line, which radiated in
Africa and South America during the Late Cretaceous and dispersed into
Laurasia in the Tertiary. This scenario is consistent with the
occurrence of distinctive annonaceous seeds in the latest Cretaceous
of West Africa and the Eocene of England. However, molecular analyses,
while confirming the basal position of Anaxagorea, strongly
associate the Asian genus Cananga with the near-basal ambavioid
clade, which is mainly Gondwanan, suggesting at least one other early
Laurasian-Gondwanan disjunction. Based on distribution of putatively
primitive taxa in Madagascar and derived taxa in Asia, it might be
suggested that Myristicaceae have a similar age and history. Our
phylogenetic analyses of Myristicaceae, using morphology and several
chloroplast regions, confirm that Asian taxa are derived, but they
nest the Malagasy genera within an Afro-Malagasy clade, which may or
may not be basal. Myristicaceae as a whole show strikingly lower
divergence in three chloroplast regions than Annonaceae, suggesting
either a much younger age or a marked slowdown in molecular evolution.
Some Cretaceous and Tertiary fossils have been identified as
Myristicaceae, but these have few if any diagnostic characters. These
data could mean that Myristicaceae are much younger than Annonaceae,
but this poses a problem in requiring transoceanic dispersal of large
seeds.
Key words: Annonaceae, biogeography, Magnoliales, Myristicaceae, paleobotany, phylogeny