Host plant phylogeny does not fully explain host choice and feeding preferences of Galerucella birmanica, a promising biological control herbivore of Trapa natans

The leaf-beetle Galerucella birmanica is a potential biocontrol herbivore for water chestnut, Trapa natans in North America. During our assessments of effectiveness and safety of G. birmanica in quarantine, we found a narrow fundamental host range with complete development only possible on all T. natans morphospecies present in North America and Brasenia schreberi. Phylogenetic relatedness did not fully explain feeding and oviposition preferences of G. birmanica in no-choice or multiple-choice trials. Instead, feeding and oviposition on non-target plants appears better explained by host-associations of congeneric Galerucella species, underscoring the impor-tance of including additional factors in selecting host-specificity test plant species. To further gauge potential risk to B. schreberi, we used a comparative performance metric proposed by Paynter et al. (2015) and found G. birmanica scored low, further indicating low risk to B. schreberi. Our findings suggest that widespread and safe biocontrol of T. natans in North America appears promising if G. birmanica is granted release approval by reg-ulatory agencies.

Automated summary

This study found that the leaf-beetle Galerucella birmanica only undergoes complete development on Trapa natans and Brasenia schreberi in North America. The feeding and oviposition preferences of G. birmanica cannot be fully explained by phylogenetic relatedness. Based on the low risk score of G. birmanica to Brasenia schreberi, widespread and safe biocontrol of T. natans in North America seems promising if approved by regulatory agencies.