Seed dispersal and seed fate in Joshua tree (Yucca brevifolia)

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• 作者：B.A. Waitman^a ; ¹ ; ^{bawaitma@ucdavis.edu} ; S.B. Vander Wall^b ; ^sv@unr.edu ; T.C. Esque^c
• 关键词：Joshua tree ; Scatter-hoarding ; Seed dispersal ; White-tailed antelope ground squirrel ; Yucca brevifolia
• 刊名：Journal of Arid Environments
• 出版年：2012
• 期刊代码：93_01401963
• 类别：ear
• 出版时间：June, 2012
• 卷：81
• 期：Complete
• 页码：1-8
• 文件大小：262 K

摘要

Joshua tree (Yucca brevifolia) is a charismatic symbol of the Mojave Desert. Despite its familiarity, we know little about the reproduction of this species, including mechanisms of seed dispersal. Here we examine mechanisms of seed dispersal and resulting seed fate. We experimentally tracked fruit and seed removal and followed the fates of Joshua tree seeds using radioactive tracers. The majority of Joshua tree fruits monitored were taken directly from the tree canopy by white-tailed antelope squirrels, and seeds and fruits on the soil surface were quickly removed by animals. Rodents given seeds labeled with scandium-46 cached them between 0.1 cm and 4.1 cm deep. Seedling emergence was most common for seeds planted 1 cm deep, whereas seeds placed on the soil surface seldom germinated. Wind dispersal is unlikely because fruits and seeds lack adaptations for wind dispersal; wind speeds required to move Joshua tree seeds and fruits across the soil surface were higher than those typically found in the Mojave Desert. Further, rodents removed most seeds before abiotic burial was possible. We conclude that most Joshua tree seeds are dispersed by scatter hoarding by rodents, and that caches made by rodents are suitable sites for seedling emergence.