Search Results (3)

Cycads are being endangered by several anthropogenic threats, and invasions of non-native herbivores are among those threats. Various country invasions by the cycad blue butterfly Luthrodes pandava have threatened the local horticulture cycad trade and native cycad populations. Little is known about behaviors of the larval stage of this specialist herbivore, the life phase that causes damage to cycad leaf tissue. The objective here was to determine larval ability to discriminate among Cycas species that are known to exhibit contrasting susceptibility to L. pandava herbivory. Dual-choice cafeteria protocols were used whereby a single larvae was provisioned with one leaflet of minimally damaged species (low quality) and one leaflet of heavily damaged species (high quality). Consumption after an 8 h feeding cycle was measured as loss in leaflet area. Wild L. pandava populations derived from in situ Philippine and Thailand Cycas habitats preferentially fed on high quality leaflets. In contrast, invasive L. pandava populations from urban locations in Guam, Philippines, and Thailand exhibited no preferences in leaflet feeding choice. The findings indicated that larvae of this Lycaenidae specialist herbivore exhibit complex selection behaviors that depend on origin of the butterfly and feeding history. Discrimination capabilities of the in situ populations that evolved with a single native Cycas species demonstrated beneficial behaviors that appear to be lost over time by invasive populations that feed on numerous novel Cycas hosts within the invasive range. Full article

The natural distribution of Cycas micronesica includes three island groups. Damage to the widespread tree from the armored scale Aulacaspis yasumatsui was initiated with the 2003 invasion of Guam and the 2007 invasion of Rota. This herbivore has threatened the unique gymnosperm species with extinction. The number and identity of co-occurring consumers are dissimilar among disjunct insular subpopulations, and six of these habitats were used to assess tree mortality trends to confirm that A. yasumatsui stands alone as the greatest threat to species persistence. Following the initial infestation outbreak of this pest into each new subpopulation, the standing seedlings and saplings were the first to be culled, the juvenile plants were the next to be culled, and then the adult trees were killed more slowly thereafter. The timing of this plant population behavior did not differ among habitats with five other consumers, three other consumers, one other consumer, or no other consumers. We have shown that A. yasumatsui acting as the sole biotic threat in an isolated subpopulation can generate a decline in survival that is as rapid as when it is acting in conjunction with up to five other consequential consumers. This armored scale is the most acute threat to C. micronesica, and adding other specialist herbivores to the scale herbivory does not alter the speed and extent of initial plant mortality. Full article

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 Cycas micronesica 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 Aulacaspis yasumatsui Takagi armored scale, Erechthias sp. Meyrick leaf miner, and Luthrodes pandava Horsfield butterfly, which elicited unprecedented irruptions of the native Acalolepta marianarum Aurivillius stem borer and increased herbivory by feral pigs (Sus scrofa 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. Full article