Relationship between herbivory and leaf traits in mangroves on Iriomote Island, southern Japan

ABSTRACTLeaf herbivory potentially affects carbon (C) and nutrient cycling in forest ecosystems. It is especially critical to study the leaf herbivory rates in mangroves to understand the pattern of resource changes from the detrital pathway to the grazing pathway. However, determinants of leaf herbivory rates in mangroves are poorly understood. We examined the differences in leaf herbivory rates among leaf phenotypes (sun or shade leaves), leaf ages (young or old leaves), and season (summer or winter) and investigated the relationships between the leaf herbivory rates and 12 leaf traits (including chemical, physiological, and physical/mechanical traits) in each of six communities from the seaward fringe to the inland of subtropical mangroves on Iriomote Island, southern Japan. The herbivory rates decreased from seaward to landward mangrove species, excluding one species in the landward mangroves. The herbivory rates also decreased as the concentration of condensed tannins or the tannins:nitrogen ratio increased but did not correlate with the other leaf traits. Overall, season, leaf phenotype, and leaf age had no effect on the herbivory rate. However, in the two seaward and one rhizophoraceous species, the herbivory rates were higher in summer than in winter and were affected by the leaf phenotypes. The concentration of leaf condensed tannins moderately influenced leaf herbivory, fluctuating from seaward to landward; therefore, it was one of the factors driving the grazing pathway in mangroves. Understanding these mechanisms is critical for a comprehensive appreciation of the high productivity of and nutrient cycling in mangrove forest ecosystems.KEYWORDS: Leaf herbivoryleaf traitsmangrovecondensed tanninsplant–herbivore interaction AcknowledgementsWe thank the Ministry of the Environment, Japan, for permission to conduct the field survey on Iriomote Island (number OKINAWA 558); M. Iwao for the chemical analyses; K. Oshima and J. Yokoi for the leaf image analyses; S. Katagiri and M. Tamamoto for the field survey; K. Yabe for levelling; S. Watanabe for helpful discussions; and Y. Nemoto for statistical analyses.Disclosure statementNo potential conflict of interest was reported by the author(s).Data availability statementThe datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.Supplementary dataSupplemental data for this article can be accessed online at https://doi.org/10.1080/13416979.2023.2279003Additional informationFundingThis study was supported by JST SPRING under grant JPMJSP2122 to YH and by JSPS KAKENHI under grant 22H02390 to NI.