Invasive arthropod herbivores comprise one of the greatest threats to cycad conservation both in situ and ex situ. The lepidopteran Chilades pandava (Plains Cupid Butterfly, Fig. 1B) is a specialist insect native to southern Asia that invaded Guam in recent years (Moore et al., 2005), and it is among the invasive species that are collectively threatening the endemic Cycas micronesica K.D. Hill (Marler and Lawrence, 2012). This insect depends on a sustained close relationship with native Cycas within its indigenous range. It causes extensive damage to Cycas populations within habitats in its invasive range like Guam. These factors engender a horticultural conflict between the need to protect Cycas species from damage within garden settings and within the butterfly’s invasive range and the arguable need to conserve its dependence on Cycas plants in situ.
An extensive ex situ germplasm collection of Guam’s C. micronesica was established at Nong Nooch Tropical Botanical Garden in Thailand as part of our efforts to conserve this endangered cycad. In this setting where the butterfly is native, herbivory is highly heterogeneous among comingled Cycas species. Some species like Cycas revoluta Thunb. (Fig. 1C) and C. micronesica (Fig. 1E) exhibit extensive, unsightly damage, whereas other species exhibit minimal damage (Figs. 1D and 1F). Management decisions for this situation would benefit from understanding how the butterfly relates to its native host Cycas species in natural habitats and how it relates as a pest to novel Cycas host species in horticultural settings.
Most of the 107 described Cycas species (Osborne et al., 2012) are being conserved in the ex situ cycad germplasm collections in Nong Nooch Tropical Botanical Garden. Pesticide protection of susceptible Cycas taxa resulting from this pest represents one of the greatest costs for success of these conservation efforts. We used this germplasm collection growing in a common garden setting to determine relative butterfly herbivory at the species level. Our objective was to then mine these data for linkages between resistance to damage and group traits that may reduce uncertainty in predictions of and expose mechanisms that explain disparity in butterfly damage.
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