Kandyan home gardens: Repositories for insects and their interactions in Sri Lanka

Kandyan Home Gardens (KHGs) symbolize a prominent, traditional and sustainable perennial cropping system practiced for several centuries in Sri Lanka. This study was conducted to compare the insect interactions associated with plants and terrestrial vertebrates in three KHGs which were located in Kandy and Gampola from May to December 2009.  A total of 57 insect species in 15 families representing 25 butterflies, 11 dragonflies, nine bees, two wasps were collectively recorded from three KHGs. Further, mutualism, commensalism, carnivory and herbivory were the observed insect interactions which interacted with 89 plant species and 24 terrestrial vertebrates.  According to the beta diversity similarity indices, insect and vegetation assemblages were similar in the two KHGs in Gampola. Commensalism was the most recurrently recorded relationship and herbivory was the rarely recorded insect interaction in all three KHGs. According to the Pearson's correlation coefficient analysis, there was a positive relationship between species richness of insects and plant species (r= +0.978) in each KHG. Furthermore, there were positive relationships between plant species richness and insect species richness (r= +0.978), mutualism (r= +0.944), herbivory (r= +0.999) and negative with commensalism (r= -0.571). Moreover, there were positive relationships between insect species richness and mutualism (r= +0.950), herbivory (r= +0.985) and negative with commensalism (r= -0.655) and carnivory (r= -0.919). Overall, insect interactions were important in relationships between plants and terrestrial vertebrates studied in three KHGs. Therefore, this study shows that Kandyan home garden system as an important strategy for conserving insect diversity outside the agricultural and protected areas.