Genetic structure and host associations of the noctuid moth Callopistria exotica, a potential biological control agent for Lygodium microphyllum

Lygodium microphyllum is a damaging environmental weed that continues to spread rapidly across Florida. The natural enemies released so far have had some impact on L. microphyllum, but this weed continues to grow densely and spread, so new biological control agents are required. Native range surveys of L. microphyllum identified a noctuid moth, Callopistria exotica, commonly feeding on this fern. We collected C. exotica feeding on Lygodium in Australia, China, India, Indonesia, Japan, Malaysia, Singapore, and Thailand, and sequenced three genes (COI, 18S, 28S) to assess genetic structure across its geographic distribution. We identified a unique C. exotica genetic lineage in Japan, feeding on Lygodium japonicum. This lineage may represent a distinct species, and could potentially be well-suited to control L. japonicum, which has also developed into a damaging weed across Florida. Furthermore, we found genetic structuring within the moth samples collected from L. microphyllum, with three distinct mitochondrial lineages identified. We recommend treating these distinct C. exotica lineages independently from one another for the purposes of host range testing, and suggest further tests to clarify their species status relative to one another. Our study illustrates how the genetic screening of native range survey data can provide important preliminary information that helps develop hypotheses to direct additional surveys, agent selection, and host range testing.