Seed shielding, an undescribed process that prevents seed from overheating (and dying) in extreme weather conditions

Abstract

Sun exposure is a major threat to the survival of cacti seeds in desertic environments. During summer, fruits of the columnar cactus Pachycereus pringlei from San Esteban Island, northwestern Mexico, are eaten by herbivorous iguanas, and after digestion, seeds are deposited within their scats. We compared the germination percentage of wild seeds exposed to the sun while lying on the ground of the island, with that of seeds collected directly from the fruit, and seeds obtained from old and recently deposited iguana scats. Our results indicate that direct sun exposure causes drastic reduction in seed germination, and this negative effect is reduced in seeds shielded inside feces, although with a cost on germination. We discuss some of the possible implications of seed shielding in the population of P. pringlei.