SCHARASCHKIN, TANYA1*, JAMES A. DOYLE1, and LARS W. CHATROU2. 1Section of Evolution and Ecology, University of California, Davis, CA 95616; 2National Herbarium of the Netherlands, Utrecht University Branch, Heidelberglaan 2, 3592 CS, Utrecht, The Netherlands. - Implications of morphological and molecular phylogenetic analysis for the biogeographic history of Anaxagorea (Annonaceae).
The Annonaceae are a pantropical family, with ca. 130 genera and ca.
2500 species. Morphological and molecular phylogenetic analyses place
Annonaceae in the Magnoliales, with Eupomatiaceae as their sister
group. Within Annonaceae the genus Anaxagorea is sister to the
rest of the family. Anaxagorea, with 26 species, presents a
unique pattern of geographic disjunction for the family, with four
species in Asia and the rest in Central and South America. Most other
genera are either paleotropical or neotropical, except for
Xylopia, which is pantropical. Based on morphological
phylogenetic analyses, it has been suggested that Annonaceae arose in
the Early Cretaceous when taxa could disperse between Laurasia and
Northern Gondwana, and split into a Laurasian line, represented today
by Anaxagorea, and a Gondwanan line that gave rise to the rest
of the family, while Asian taxa other than Anaxagorea represent
later invasions of Laurasia from Africa. In the latest Cretaceous,
seeds and pollen of Annonaceae are reported from Northern Gondwana
(west Africa, Colombia), while seeds from the London Clay indicate the
presence of Annonaceae in Laurasia by the Eocene. This biogeographic
scenario can be tested phylogenetically by determining whether or not
the South American species are nested among Asian and Central American
species. For this purpose we have conducted a phylogenetic analysis of
Anaxagorea and selected outgroups based on morphological
characters and sequences of the chloroplast regions trnL-F and
trnK. Preliminary morphological results support the monophyly
of Asian taxa plus the Brazilian species A. silvatica, while
trnL-F supports nesting of the other South American species
within a Central American grade. This supports a Laurasian origin for
most South American taxa, but it also indicates the biogeographic
history of the family may be more complex, with two distinct origins
of the present disjunction.
Key words: Anaxagorea, Annonaceae, biogeography, trnK, trnL-F