Journal of Asia-Pacifc Entomology 25 (2022) 101865 Available online 8 January 2022 1226-8615/© 2022 Korean Society of Applied Entomology. Published by Elsevier B.V. All rights reserved. Melanization plasticity of Drosophila kikkawai, Drosophila leontia and reciprocal hybrids under different temperatures Divya Singh a , Seema Ramniwas a, * , Pankaj Kumar Tyagi c, * , Girish Kumar b , Deepak Gola d a University Center for Research and Development, Chandigarh University, Gharuan, Mohali 140413, India b University of Central Florida, Genomics and Bioinformatics Cluster, Department of Biology, 4110 Libra Drive, Orlando, FL 32816, USA c Department of Biotechnology, Noida Institute of Engineering & Technology, Greater Noida, U.P., India d IILM College of Engineering &amp Technology, IILM Academy of Higher Learning, Greater Noida, U.P., India A R T I C L E INFO Keywords: Fruit fy Hybrid Introgressive hybridization Abdominal melanization Phenotypic plasticity ABSTRACT Drosophila (Sophophora) kikkawai, Burla, 1954 and Drosophila (Sophophora) leontia, Tsacas & David 1978 are closely related sibling species, the former being cosmopolitan and the latter is restricted to tropical localities. We investigated the infuence of introgressive hybridization on phenotypic diversity of the two sibling species in the present study. How hybridization supports the relative abundance of pure species according to latitudinal cline is the aim of this study because hybrids show a tendency to acquire geographical location of their parent species in equal or greater abundance. How hybridization supports the plasticity for melanization of hybrids is not explored yet. The two species can cross and generate hybrids. For this, we crossed true breeding strains of both species to obtain the hybrids i.e. dark female (♀) of D. kikkawai (D. k) with males (♂) of D. leontia (D. l) in cross I and light ♀ of D. k with ♂ of D. l in cross II along with their reciprocal crosses. Finally, we studied the plasticity of both species and their hybrids at 6 growth temperatures (14, 17, 21, 25, 28 and 31 ◦ C). We found that there is no plasticity for melanization in true breeding darker and lighter strain of D. kikkawai as well as D. leontia whereas hybrids of both species showed high phenotypic plasticity. Signifcant differences in slope values across tem- peratures in parental and hybrid lines suggest plastic effects. Phenotypic variation in abdominal melanization in hybrids can be interpreted as a result of gene introgression with D. kikkawai. We conclude that introgressive hybridization might be an important, although underestimated, mechanism shaping species distribution and adaptation. Introduction Genetic variation is the presence of more than one allele at a particular locus. If an allele is advantageous, it may enable some in- dividuals to adapt to the environment and increases ftness. Mutation can be a source to acquire genetic variation even with a rate of ~ 10 -5 to 10 -6 per loci per generation in humans ( Piraino et al., 2018). Hybridi- zation is a source of revolutionary alleles which could be advantageous or detrimental because by natural selection hybridization allows intro- gression of combinations of alleles. The outcome of hybridization is extreme phenotypes which is never seen in parents and hence show evolutionary novelty. The adaptations which are novel will not appear faster within a breeding population when characterized by random mating (Barton, 2013). Incorporation of alleles from one species into gene pool of another primarily via hybridization and backcrossing is known as introgression (Harrison and Larson, 2014). It provides an effcient way for species to adapt in either way the ftness (benefcial or detrimental) of genetic variation of a closely related species. For example, in a laboratory experiment, (Lewontin and Birch, 1966) used phenotypic classes constructed through hybridizing species to assess distribution of color variants in Dacus fruit fies. In another example, Tigriopus californicus, The F 1 hybrids show increase in ftness while F 2 hybrids show decrease in ftness interpreting these patterns as the benefcial and the detrimental effects (Edmands, 1999). Results showed increase in environmental tolerance and range of D.tryoni due to intro- gressed genes from D.neohumeralis. Thus, introgressive hybridization has the potential to generate the diversity for evolution, rapid enough to allow response to sudden environmental shifts (Baskett and Gomulkie- wicz, 2011). When two different species of same genus crosses then interspecifc * Corresponding authors. E-mail addresses: seema.ramniwas@gmail.com (S. Ramniwas), pankaj.tyagi@niet.co.in (P.K. Tyagi). Contents lists available at ScienceDirect Journal of Asia-Pacifc Entomology journal homepage: www.elsevier.com/locate/jape https://doi.org/10.1016/j.aspen.2021.101865 Received 12 September 2021; Received in revised form 4 December 2021; Accepted 29 December 2021