Harmonious Coexistence of Hispine Beetles on Heliconia In Experimental and Natural Communities

Hispine beetles that live as adults in the rolled leaves of Heliconia plants are prime suspects for interference competition among species, based upon theory developed by vertebrate ecologists. These beetles are tropical, long—lived, and very closely related, eat the same food, and use the same habitat. However, hispines do not conform to this theory: 1) Rolled—leaf hispines are not aggressive intra— or interspecifically, and are not displaced or intimidated by encounters between individuals. 2) Adults are not segregated by species into different leaf subsets of host populations. Species mingle together in patterns that do not suggest interspecific competition. 3) Number of species does not affect interspecific association. 4) Pairwise correlations indicate that only one beetle (Cephaloleia) of the 13 species studied is even weakly segregated from others. It prefers leaves on younger plants than those preferred by other species, and its segregation is a result of subtle habitat differences rather than competition. 5) Interspecific segregation among hispanies does not increase with density in leaves. 6) No higher order interactions were detected in species associations. 7) Experiments showed that habitat heterogeneity does not measurably influence interspecific association in hispine communities as delimited by a single host species. Experimental communities in nature were constructed with minimal habitat heterogeneity, and no mor segregation or aggregation between hispine species occurred in experimental than in natural communities. Additional observations suggest that levels of food and habitat are commonly not limiting to hispine populations, which suffer heavy parasitism and predation. I infer that community structure of hispines on Heliconia is affected greatly by natural enemines. Heliconia is not chemically noxious to hispines, and experiments show that hispines grow at maximum rates on the relatively low nitrogen content of Heliconia. Theories of community structure based upon interspecific competition, and those based upon allelochemical protection of host plants against adapted insects, are not suitable for hispine communities on Heliconia. My conclusions largely agree with those of Hairston et al. 1960. Additional work with parasitism, predation and other factors that may affect hispine populations, such as the weather, migration, and spacing of host plants, is necessary to establish key and regulatory factors for these tropical insects.