Change in biomass of symbiotic ants throughout the ontogeny of a myrmecophyte, Macaranga beccariana (Euphorbiaceae).
Macaranga myrmecophytes (ant-plants) provide their partner symbiotic ants (plant-ants) with food bodies as their main food, and they are protected by the plant-ants from herbivores. The amount of resource allocated to food bodies determines the plant-ant colony size and consequently determines the intensity of ant defense (anti-herbivore defense by plant-ants). As constraints in resource allocation change as plants grow, the plant-ant colony size is hypothesized to change with the ontogenesis of Macaranga myrmecophyte. To determine the ontogenetic change in the relative size of the plant-ant colony, we measured the dry weights of the whole plant-ant colony and all of the aboveground parts of trees at various ontogenetic stages for a myrmecophytic species (Macaranga beccariana) in a Bornean lowland tropical rain forest. Ant biomass increased as plant biomass increased. However, the rate of increase gradually declined, and the ant biomass appeared to reach a ceiling once trees began to branch. The ant/plant biomass ratio consistently decreased as plant biomass increased, with the rate of decrease gradually accelerating. We infer that the ontogenetic reduction in ant/plant biomass ratio is caused by an ontogenetic change in resource allocation to food rewards for ants related to the physiological changes accompanying the beginning of branching.
Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu, Sakyo-ku, Kyoto 606-8501, Japan. c.h.chihiro@gmail.com
Chihiro
C
Handa
Tadahiro
T
Okubo
Aogu
A
Yoneyama
Masashi
M
Nakamura
Mari
M
Sakaguchi
Narumi
N
Takahashi
Mayumi
M
Okamoto
Ayumi
A
Tanaka-Oda
Tanaka
T
Kenzo
Tomoaki
T
Ichie
Takao
T
Itioka
D000818:Animals; D001000:Ants / Q000502:physiology*; D018533:Biomass; D001893:Borneo; D017753:Ecosystem; D019665:Euphorbiaceae / Q000502:physiology*; D013045:Species Specificity; D013559:Symbiosis / Q000502:physiology*; D014197:Trees; D014329:Tropical Climate