Acacia trees are keystone species in many arid environments, supporting high levels of plant and animal diversity. In Israel, the populations of Vachellia (formerly Acacia) tortilis (Forssk.) and V. raddiana (Savi) are declining at an alarming rate. Severe infestations by bruchid beetles (Coleoptera, Chrysomelidae) are among the major causes of seed mortality, but additional environmental stressors can reduce the defence level of the seeds, exacerbating their susceptibility to predators. In a hyper-arid desert ecosystem affected by two major oil spills (in 1975 and 2014), we quantified seed predation rates caused by insect granivores before and after the pods dropped to the ground. We recorded predation rates of up to 84% for both tree species, and higher predation rates at the ground level than in the canopy, suggesting that repeated infestations occur. These results reinforce the call to protect the populations of large ungulates such as gazelles, which kill the bruchids by feeding upon the pods, and promote seed germination and dispersion. We found no clear evidence of a negative effect of the oil spill on seed predation, indicating that oil pollution did not increase the vulnerability of the seeds to granivores even in trees affected by the recent oil spill.

中文翻译：

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高干旱沙漠生态系统中油污染和未污染的Vachellia（Acacia）树的种子捕食

相思树是许多干旱环境中的关键物种，支持高水平的动植物多样性。在以色列，瓦切里亚（以前为Acacia）tortilis（Forssk。）和V. raddiana的人口（Savi）的下降速度惊人。布鲁氏甲虫（鞘翅目，菊科）的严重侵袭是造成种子死亡的主要原因，但是额外的环境胁迫因素会降低种子的防御水平，加剧其对天敌的敏感性。在受到两次主要溢油影响的高干旱沙漠生态系统中（分别于1975年和2014年），我们对豆荚掉落到地面之前和之后由昆虫食肉动物引起的种子捕食率进行了量化。我们记录到两种树种的捕食率均高达84％，并且在地面上的捕食率比树冠更高，表明发生了多次侵扰。这些结果加强了人们对保护大型有蹄类动物（如瞪羚）的呼吁，这些羚羊通过觅食荚果杀死了串足类动物，并促进了种子发芽和扩散。