CIOFANI, KRISTEN, LYDIA MIRAMONTES, and RICHARD JENSEN.* Department of Biology, Saint Mary's College, Notre Dame, IN 46556. - Morphometric analyses of red maple (Acer rubrum L.), silver maple (Acer saccharinum L.), and their hybrid (Acer X freemanii E. Murray).
The phenomenon of morphological intermediacy often can be used to
identify individuals of hybrid origin. However, morphological
intermediacy is not always apparent in individual characters. Our
experience is that multivariate analyses are very likely to reveal
hybridity because the combinations of characters in the hybrids
disrupt the patterns of covariance that allow recognition of the
parental taxa. For this study, we sampled six trees (two each from
three accessions) of Acer X freemanii from the Morton
Arboretum, along with 40 trees from northern Indiana field identified
as either A. rubrum or A. saccharinum.
Leaves were pressed and dried and leaf blade outline and landmark data
were captured using MorphoSys. A data set of linear and angular
characters was used for input to cluster analysis and principal
components analysis. The same multivariate tools were used to analyze
elliptic Fourier coefficients derived from leaf outlines and
thin-plate spline weights derived from landmark configurations. All
three approaches provide views in which some or all of the hybrids are
intermediate between the parental taxa and in which some
field-collected trees also appear to be of hybrid origin. But, there
are differences with respect to which trees may be of hybrid origin.
These differences reflect the different aspects of leaf blade shape
derived from each set of data.
Key words: Acer, hybrids, morphometrics, multivariate analyses