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 breast height of 78 male trees of the south-Andean dioecious conifer, Austrocedrus 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 two variables could not be evaluated, however, because of high colinearity between them. Tree reproductive effort and mean size of viable pollen grains, variables that could reflect resource availability and physiological stress, did not account for any significant part of the variation in the proportion of aborted pollen. Neither did these variables covary with tree age or size. To the extent that pollen abortion in this species is due to genetic causes, these results support a qualitative prediction of the ''genetic load-with-age accumulation model,'' which asserts that pollen viability should decrease with aging.