Host plant defense produces species-specific alterations to flight muscle protein structure and flight-related fitness traits of two armyworms.

Insects manifest phenotypic plasticity in their development and behavior in response to plant defenses, via molecular mechanisms that produce tissue-specific changes. Phenotypic changes might vary between species that differ in their preferred hosts and these effects could extend beyond larval stages. To test this, we manipulated the diet of southern armyworm (SAW; ) and fall armyworm (FAW; ) using a tomato mutant for jasmonic acid plant defense pathway (), and wild-type plants, and then quantified gene expression of Troponin t () and flight muscle metabolism of the adult insects. Differences in spliceform ratios in insect flight muscles correlate with changes to flight muscle metabolism and flight muscle output. We found that SAW adults reared on induced plants had a higher relative abundance (RA) of the isoform of Troponin t () in their flight muscles; in contrast, FAW adults reared on induced plants had a lower RA of in their flight muscles compared with adults reared on and controls. Although mass-adjusted flight metabolic rate showed no independent host plant effects in either species, higher flight metabolic rates in SAW correlated with increased RA of Flight muscle metabolism also showed an interaction of host plants with in both species, suggesting that host plants might be influencing flight muscle metabolic output by altering This study illustrates how insects respond to variation in host plant chemical defense by phenotypic modifications to their flight muscle proteins, with possible implications for dispersal.