CANNON, CHARLES1,2* and PAUL MANOS1. 1Dept. of Biology, Duke University, Box 90339, Durham, NC 27708; 2IBEC, University of Malaysia, Sarawak, Kota Samarahan, Malaysia. - The use of morphometric shape descriptors in relation to an independent molecular phylogeny: the case of fruit type evolution in Bornean Lithocarpus (Fagaceae).
The Bornean assemblage of the genus Lithocarpus (Fagaceae) contains
several novel modifications of the classic oak-acorn fruit type, which
encompasses much of the generic level morphological variation. The
shape variation in fruit type was adequately captured by continuous
morphometric descriptors of radial outlines of fruit exocarp and
receptacle. Both a principal components analysis of elliptic Fourier
coefficients (EF-PCA) and eigenshape analysis (EGS) provided
informative descriptors of shape variation. A neutral evolutionary
model and restricted maximum likelihood was used to create a
morphometric transformation series. Several important taxonomic and
phylogenetic aspects were captured by these analyses. An independent
molecular phylogeny of the ITS regions of the nuclear ribosomal DNA
for the same exemplar species supported parallel derivations of a
specialized fruit type, not apparent in the morphometric
transformation series. This incongruence suggests convergent evolution
of a complex fruit morphology between independent lineages. Conversion
of morphometric series into matrix representations weighted by
standardized branch lengths allowed a combined phylogenetic analysis
with the molecular data which produced a single most parsimonious tree
and supported two independent derivations of the specialized fruit
type. The relative rates of change between morphology and molecules is
not correlated between well-supported nodes and do not consistently
deviate in one direction or the other. The molecular change from
outgroup to ingroup is much greater than the morphometric change while
transitions to the specialized fruit type involved large morphometric
changes with little corresponding molecular change. The use of
continuous morphometric shape descriptors significantly contributed to
our understanding of fruit evolution in a morphologically difficult
group.
Key words: comparative analysis, continuous morphometric characters, Eigenshape analysis, Fagaceae, Lithocarpus, matrix representation parsimony