HAMRICK, J. L.* AND PRESTON R. ALDRICH. University of Georgia, Athens, Georgia, Smithsonian Institute, Washington, D.C.. - Temporal variation in the breeding structure of fragmented Enterolobium cyclocarpum populations.
Seeds within fruits of many
mimosoid legumes are usually the progeny of a single pollen donor
(i.e. full sibs). Multilocus allozyme analyses of such full-sib
progeny arrays allow the identification of the pollen donor's
multilocus genotype. The analysis of several pods per tree provides a
means of estimating the number of pollen donors contributing to the
fruit crop of each maternal individual. Fragment populations of
Enterolobium cyclocarpum located in SW Costa Rica were analyzed for
13 polymorphic allozyme loci to determine the number of pollen donors
per tree, rates of gene flow into the fragments, and spatial areas
from which pollen was contributed to each fragment. Fruit collections
made over a three year period (1994-1996) allowed comparisons to be
made of the breeding structure and gene flow rates among years. Trees
within fragments separated by a few kilometers had different pools of
pollen donors but some pollen donors were shared. Significant
heterogeneity in pollen donor pools were also observed among trees
within fragments and among years. Trees producing substantial seed
crops in generally poor fruiting years had fewer pollen donors than
the same trees had in good fruiting years.
Key words: allozyme, breeding structure, Enterolobium cyclocarpum (Mimosoideae), fragmented populations, gene flow, paternity analysis