Self and non-self recognition affects clonal reproduction and competition in the pea aphid.

Yang Li,Shin-Ichi Akimoto

doi:10.1098/rspb.2021.0787

Abstract

The spatial interaction of clonal organisms is an unsolved but crucial topic in evolutionary biology. We evaluated the interactions between aphid clones using a colour mutant (yellow) and an original (green) clone. Colonies founded by two aphids of the same clone and mixed colonies, founded by a green aphid and a yellow aphid, were set up to observe population growth for 15 days. We confirmed positive competition effects, with mixed colonies increasing in size more rapidly than clonal colonies. In mixed colonies where reproduction started simultaneously, green aphids overwhelmed yellow aphids in number, and yellow aphids restrained reproduction. However, when yellow aphids started to reproduce earlier, they outnumbered the green aphids. To test whether aphids have the ability to control reproduction according to the densities of self and non-self clones, one yellow aphid or one antennae-excised yellow aphid was transferred into a highly dense green clone colony. Intact yellow aphids produced fewer nymphs in crowded green colonies, whereas the fecundity of antennae-excised aphids did not change. Thus, we conclude that aphid clones can discriminate between self and non-self clones, and can regulate their reproduction, depending on whether they are superior or inferior in number to their competitors.

Highlights

Clonal reproduction is the major mode of propagation for some plants, parasites, marine benthic animals and aphids
Colonies founded by a single green aphid (1G) increased more rapidly 3 in number than those founded by a single yellow aphid (1Y)
Colonies founded by two green aphids (2G) increased more quickly than those founded by two yellow aphids (2Y), but no significant difference was detected in final colony size between the two clones (ANOVA, d.f. = 1,18, F = 0.21, p = 0.65)

Summary

Introduction

Clonal reproduction is the major mode of propagation for some plants, parasites, marine benthic animals and aphids. Synthesizing the results from these experiments, we will, for the first time, indicate that aphids can discriminate self and non-self clones and regulate their reproduction depending on whether they are surrounded by their own clonal members or by members of a distinct clone. In the mixed clone treatment, we prepared experiments where a yellow aphid reproduced 2 or 3 days earlier than a green aphid to test whether the timing of reproduction affects the outcome of competition.

Results

Conclusion