SAUQUET, HERVE1*, ANNICK LE THOMAS1, JAMES A. DOYLE2, KHIDIR W. HILU3, THOMAS BORSCH4, and LARS W. CHATROU5. 1Laboratoire de Biologie et Evolution des Plantes vasculaires EPHE, Museum national d'Histoire naturelle, 16, rue Buffon, 75005 Paris, France; 2Section of Evolution and Ecology, University of California, Davis, CA 95616, USA; 3Department of Biology, Virginia Tech, Blacksburg, VA 24061, USA; 4Abteilung Systematik und Biodiversitaet, Botanisches Institut und Botanischer Garten, Friedrich-Wilhelms-Universitaet Bonn, Meckenheimer Allee 170, 53115 Bonn, Germany; 5National Herbarium of the Netherlands, Utrecht University branch, Heidelberglaan 2, 3584 CS Utrecht, The Netherlands. - Insights into the origin and evolution of Myristicaceae (Magnoliales), based on morphological and molecular data.
All recent molecular phylogenetic analyses restrict Magnoliales to a
monophyletic order of six families, whose closest relatives are
Laurales, Winterales, and Piperales. We present a morphological
cladistic study of all 20 genera of Myristicaceae and a broad sample
of outgroups, emphasizing the contribution of palynological
characters. This analysis placed the Malagasy genus Mauloutchia
at the base of Myristicaceae. However, a detailed species-level study
of Mauloutchia reveals unexpected intrageneric variation for
the most important characters in the family (including stamen fusion,
exine structure, and aril development), calling into question the
putative primitiveness of this enigmatic genus. In addition, we
generated sequences of the trnK intron (including matK),
the trnL intron, the trnL-trnF spacer, and the
ndhF gene from all families of Magnoliales (including 15 genera
of Myristicaceae) and major lineages of all three related orders.
Parsimony and maximum-likelihood analyses of these data sets strongly
support a basal position of Myristicaceae in Magnoliales and a
sister-group relationship between Eupomatia and Annonaceae, as
suggested in higher-level angiosperm analyses with less intensive
sampling in Magnoliales. Within Myristicaceae, these data support
several groups found in the morphological analyses, especially an
Asian clade including Myristica and Knema, but not the
basal position of Mauloutchia, which belongs instead to an
Afro-Malagasy clade. However, these usually fast-evolving sequences
provide much less informative variation than expected for this diverse
and widely distributed family. Annonaceae show at least three times as
much variation as Myristicaceae in the same genes. Whether these
results indicate an unexpectedly recent origin of Myristicaceae or
major changes in molecular rates during the history of Magnoliales
remains unclear. In either case, rooting of Myristicaceae using DNA
sequences turns out to be a difficult problem, due to the very long
stem branch leading to the extant family.
Key words: Magnoliales, morphology, Myristicaceae, ndhF, trnK intron, trnL