CHEMICAL DEFENCE IN CENTRAL AMERICAN NON-ANT-ACACIAS

Abstract

On the basis of their association with ants, neotropical species of the genus Acacia may be grouped into two broad categories. 'Ant-acacias', comprising less than 10% of the species in Central America depend in varying degree on a mutualistic association with ants of the genus Pseudomyrmex. The plants provide their ants with shelter in swollen stipular spines and with nourishment from foliar nectaries and nutritive structures (Beltian bodies) at the leaf tips. The ants in turn provide for the plants' protection against mammalian and insect herbivores and against neighbouring plant competitors (Belt 1874; Brown 1960; Janzen 1966, 1967). Janzen (1967) has demonstrated that Acacia cornigera (L.) Willd. plants cannot survive after experimental removal of their associated ant colonies. The remaining species of Acacia in Central America comprise the second group, the 'non-ant-acacias'. These plants do not harbour mutualistic ant colonies, nor do they possess the various morphological features of acacias with such colonies. Survival of non-ant-acacias is presumably dependent, therefore, on other means of defence against herbivores.