New Host Races of Aphis gossypii (Insecta: Hemiptera: Aphididae) from Northeast India

Insect herbivores show dynamic interaction with their food plants in space and time. Intra-species variations in response to new environments, both biotic and abiotic, though well-known in allopatric and sympatric populations, were very little documented on closely related hosts. Two new host races of Aphis gossypii, a polyphagous aphid species of agriculture and horticulture importance, are reported from Tripura, northeast India. Natural populations of this aphid from two congeneric hosts, wild taro (Colocasia esculenta esculenta) and cultivated taro (Colocasia esculenta antiquorum), showed significant differences in life history traits. Aphids from wild taro clones were bigger in size, showed higher mean relative growth rate and intrinsic rate of increase, and produced more offspring per generation than those from cultivated taro clones which were smaller in size and took longer development and generation time. Reciprocal transfer of aphids between the two host plant subspecies significantly dwindled their colonization success rate in successive three generations on the transferred hosts. Results suggest that asexual lineages of aphids show adaptation to human-imposed selection pressure in the host environment.