Pyrrolizidine alkaloids in tiger moths: trends and knowledge gaps

Insects and plants have been part of an evolutionary arms race that has led plants to produce toxins as defense and insects to sequester these chemical compounds. Pyrrolizidine alkaloids (PAs) are secondary plant chemical metabolites, and some herbivorous insects have evolved biochemical mechanisms to tolerate, sequester, and use PAs against predators and parasitoids. Several tiger moth species (Erebidae: Arctiinae) have gone one step further by transferring PAs acquired during mating to their eggs or using them as precursors of sexual pheromones, thereby making PAs an essential element in sexual selection. Although tiger moths are well known to use PAs for defense, a comprehensive qualitative and quantitative systematic review of PA research on tiger moths has yet to be conducted. To identify areas of past research focus and future research potential, we analyzed 108 studies retrieved from an exhaustive search on the Web of Science. Through a scientometric analysis, we synthesized available literature, examining authors, journals, countries and keywords with the aim of providing researchers tools to navigate the current literature more effectively. Using a systematic review approach, we evaluated the frequency of moth species studied and host plant diet, along with their research topic, allowing us to identify major knowledge gaps. We show that the number of publications decreased after 2015, and most research has focused on a few moth species and research topics. Our results provide valuable insights that can help direct research efforts to further the development of knowledge about PAs in Arctiinae.