Intraspecific variation in the status of ant symbiosis on a myrmecophyte,Macaranga bancana,between primary and secondary forests in Borneo

Abstract

AbstractA tree species,Macaranga bancana, distributed in South East Asian tropics has a mutualistic relationship with specific symbiotic ant species, which defend the plant from herbivores. To examine the intraspecific variation in the status of the ant‐plant symbiosis among microhabitats of different light conditions, we investigated the species composition of nesting ants and the herbivory damage onM. bancanasaplings by field observations and sampling in primary and secondary forests in Sarawak. In addition, the effectiveness of non‐ant (physical and chemical) defenses were estimated by feeding the larvae of a polyphagous lepidopteran withM. bancanaleaves from saplings in the two types of forests. All saplings in the primary forest were colonized by twoCrematogasterant species that had been known to be the obligate symbionts ofM. bancana,while in the secondary forest, about half of the saplings were occupied by several ant species that were not obligate symbionts. There was little herbivory damage on saplings colonized by the twoCrematogastersymbiont ants in both forest types, while the saplings colonized by the other ant species suffered a 10–60% loss of leaf area. Larval mortality of the polyphagous lepidopteranSpodoptera liturawas significantly higher when larvae fed on leaves ofM. bancanasaplings in the secondary forest than when fed on leaves ofM. bancanasaplings in the primary forest. These results suggest that the symbiosis between ants andM. bancanais looser and the non‐ant‐defenses are stronger in secondary forests, where light is more intense, than in primary forests.