DOES POLLEN VIABILITY DECREASE WITH AGING - A CROSS-POPULATION EXAMINATION IN AUSTROCEDRUS-CHILENSIS (CUPRESSACEAE)

We scored the proportion of aborted pollen, age, and diameter at breas t height of 78 male trees of the south-Andean dioecious conifer, Austr ocedrus chilensis. Although the proportion of aborted pollen was low ( range = 0.5%-7.8%), it increased significantly with tree age and size (r = .459 and .467, respectively). The independent effects of these tw o variables could not be evaluated, however, because of high colineari ty between them. Tree reproductive effort and mean size of viable poll en grains, variables that could reflect resource availability and phys iological stress, did not account for any significant part of the vari ation in the proportion of aborted pollen. Neither did these variables covary with tree age or size. To the extent that pollen abortion in t his species is due to genetic causes, these results support a qualitat ive prediction of the ''genetic load-with-age accumulation model,'' wh ich asserts that pollen viability should decrease with aging.