Effects of Color Morph on Aggregation Formation for Hibernation in an Extremely Color Polymorphic Ladybug, Harmonia Axyridis (Pallas) (Coleoptera: Coccinellidae)

Eisuke Hasegawa,Yuuka Murakami,Saori Watanabe

doi:10.35248/2161-0983.19.8.219

Abstract

Understanding of mechanism for genetic polymorphisms within and among species is an important issue in ecology and evolutionary biology. A ladybug, Harmonia axyridis (PALLAS), shows extreme elytral color polymorphism, in which more than 100 types have been recognized. This polymorphism has been explained with the inheritance of 12 hypothetical alleles at a single autosomal locus. However, why such extreme polymorphism is maintained has not been clarified. Here, we show that several morphs enlarge their aggregation size during grouping before hibernation. Our results showed that the excess (or fewerness) of either one of the four color morphs from the expected values showed each a significantly positive effect on the aggregation size. A larger aggregation size resulted in better survival of all the aggregating members. These results suggest that it is beneficial for survival to aggregate with these morphs. This survival benefit during hibernation explains partly the extreme color polymorphism in this species.

Highlights

Understanding of evolution and maintenance of biodiversity in nature is one of the most important issues in ecology and evolutionary biology [1,2,3]
We examined the effects of the 12 morphs collected just before hibernation on the size of aggregation under experimental conditions and discuss the possibility that the polymorphism in H. axyridis is maintained in part via the above mechanism
As the estimated effect of B was significant, we constructed a generalized linear mixed model (GLMM) model with B as a random effect. Using this GLMM, we examined the effect of excess or fewness from the expected number of morph on the size of the aggregation by controlling for the effect of block

Summary

Introduction

Understanding of evolution and maintenance of biodiversity in nature is one of the most important issues in ecology and evolutionary biology [1,2,3]. Some morphs show different preferences for foods (aphid species) or mate's morph [6,7]. Why this extreme polymorphism is maintained remains unclear. If different morphs have different types of the pheromone, and some morphs are more attractive to other individuals, the aggregation would become large where the attractive morphs are present. In this case, a more polymorphic population may be more advantageous for survival during hibernation than a less diverse population

Methods

Results

Discussion

Conclusion