Altitudinal variation in herbivory resistance and genetic diversity in the naturalized cyanogenic legume

Mountain landscapes are characterized by rich biodiversity shaped by variations in topography and climate. Elucidating the interplay between elevation, genetic variability, cyanogenesis, and herbivory in these ecosystems is critical for understanding ecological and evolutionary dynamics. The production of hydrogen cyanide acts as a defense against herbivory, but is limited by self-toxicity, which restricts cyanogenic individuals at high elevations. Here, we investigated a population of Trifolium repens within the Itatiaia National Park, Brazil for understanding the evolutionary strategy of this species across an elevational gradient (1,700 – 2,400 m a.s.l). Genetic analysis by inter-simple sequence repeat (ISSR) markers revealed high genetic diversity (H_T = 0.3387) but significant differentiation among elevations (G_ST = 0.1848), thus suggesting an influence of elevation on the population genetic structure. The frequency of cyanogenic individuals was inversely proportional to elevation, as expected based on potential environmental pressures. Herbivore damage, however, exhibited a positive correlation with elevation, but not significantly associated with cyanogenesis, emphasizing the role of elevation in shaping plant–herbivore interactions. Our findings underscore the critical involvement elevation gradients in shaping plant–herbivore dynamics and evolutionary strategies within mountain ecosystems.