title: Pupal melanization is associated with higher fitness in Spodoptera exigua.
abstract: Melanism has long been thought to be a habitat adaptation with a fitness cost. Here we reported a homozygous melanic strain (SEM) of Spodoptera exigua (Hübner) (Insecta: Lepidoptera: Noctuidae) established with black pupae spontaneously occurring within a typical laboratory population (SEW). The melanization is expressed globally, and only in the pupal stage. After pupation, the melanic SEM pupae gradually accumulate melanin to become completely black within 6 hours, whereas the wild-type SEW pupae gradually turn yellow-brown. The melanic SEM strain exhibits faster development in all life stages, heavier pupa weight, more mating time, higher fecundity, and accordingly, higher net reproductive rate and population trend index. While no reproductive isolation was observed between the SEM and SEW strains, the mating times per female of the reciprocal crosses and the SEM intracrosses were significantly higher than those of the SEW intracrosses. This represents a rare case of melanization that has fitness gains, rather than costs. Analysis of the life-history traits of this case and 14 previously reported cases of insect melanism indicate that none of melanization origin, stage, space and variation type determining whether melanism will cause fitness gain or cost.
authors.affiliation: 1] Department of Pesticide Science, College of Plant Science &Technology, Huazhong Agricultural University, Wuhan 430070, China [2] Department of Entomology and BIO5 Institute, University of Arizona, Tucson, Arizona [3] Hubei Insect Resources Utilization and Sustainable Pest Management Key Laboratory, Institute of Insect Resources, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Sisi
authors.initials: S
authors.lastname: Liu
authors.affiliation: 1] Department of Pesticide Science, College of Plant Science &Technology, Huazhong Agricultural University, Wuhan 430070, China [2] Hubei Insect Resources Utilization and Sustainable Pest Management Key Laboratory, Institute of Insect Resources, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Mo
authors.initials: M
authors.lastname: Wang
authors.affiliation: 1] Department of Entomology and BIO5 Institute, University of Arizona, Tucson, Arizona [2] State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Xianchun
authors.initials: X
authors.lastname: Li
mesh_terms: D000818:Animals; D056084:Genetic Fitness; D008018:Life Cycle Stages; D010858:Pigmentation; D011679:Pupa; D012098:Reproduction; D018411:Spodoptera / Q000502:physiology*