n African Entomology - Modelling the spatial patterns and interspecific interactions between three chrysomelid beetles defoliating the multipurpose agroforestry tree in Africa

Volume 14, Issue 2
  • ISSN : 1021-3589



The population dynamics of single species can be understood only in the context of interactions within an ecological community. In this study we used theoretical and empirical models to describe the spatial pattern of the Afrotropical leaf beetles Stål, and spp. defoliating the agroforestry tree ( (L.) Merril). We used the Poisson, negative binomial distribution (NBD), Taylor's power law and Iwao's mean crowding models to determine (1) intraspecific spatial patterns and conspecific interactions within a population, (2) interspecific interaction between their populations, and (3) derive a common sampling plan for the three species. The spatial patterns of larvae and adult were adequately described by the negative binomial, while those of and fitted the Poisson distribution. Taylor's power law gave very good fit (r2 >0.80) except for in Zambia, while Iwao's mean crowding gave poor fit to the spatial pattern of larvae and . The slopes of the variance-mean relationships were significantly greater than unity for adults and larvae of , indicating aggregated distribution, while those for and were closer to unity, indicating spatial randomness. The three species showed random association with varying degrees of niche overlap. Therefore, the null hypothesis of spatial independence between the populations of and , and adult and was rejected. Hence, a common sampling plan was developed for estimation of the population densities of the three species at the same time.

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