Biotic Threats to Cycas micronesica Continue to Expand to Complicate Conservation Decisions

Abstract

Invasions of non-native species can threaten native biodiversity, and island ecosystems are ideal for studying these phenomena. In this article, first, we report on the invasive species that combine to threaten the island cycad <i>Cycas micronesica</i> by reviewing the history of previously reported invasions and providing an update of recent invasions. Then, we prioritize the threat status of each herbivore and the interactions among them. Plant damage was initiated in 2003─2005 by the non-native <i>Aulacaspis yasumatsui</i> Takagi armored scale, <i>Erechthias</i> sp. Meyrick leaf miner, and <i>Luthrodes pandava</i> Horsfield butterfly, which elicited unprecedented irruptions of the native <i>Acalolepta marianarum</i> Aurivillius stem borer and increased herbivory by feral pigs (<i>Sus scrofa</i> L.). The combined impact of these five consumers represents the greatest sustained threat to the cycad tree species. Mitigation of the damage caused by phytophagous non-native species is urgently needed to conserve this unique gymnosperm tree.