Variable coloration is associated with dampened population fluctuations in noctuid moths.

Anders Forsman,Markus Franzén,Per-Eric Betzholtz

doi:10.1098/rspb.2014.2922

Abstract

Theory and recent reviews state that greater genetic and phenotypic variation should be beneficial for population abundance and stability. Experimental evaluations of this prediction are rare, of short duration and conducted under controlled environmental settings. The question whether greater diversity in functionally important traits stabilizes populations under more complex ecological conditions in the wild has not been systematically evaluated. Moths are mainly nocturnal, with a large variation in colour patterns among species, and constitute an important food source for many types of organisms. Here, we report the results of a long-term (2003–2013) monitoring study of 115 100 noctuid moths from 246 species. Analysis of time-series data provide rare evidence that species with higher levels of inter-individual variation in colour pattern have higher average abundances and undergo smaller between-year fluctuations compared with species having less variable colour patterns. The signature of interspecific temporal synchronization of abundance fluctuations was weak, suggesting that the dynamics were driven by species-specific biotic interactions rather than by some common, density-independent factor(s). We conclude that individual variation in colour patterns dampens population abundance fluctuations, and suggest that this may partly reflect that colour pattern polymorphism provides protection from visually oriented predators and parasitoids.

Highlights

Exploring the causes and consequences of population dynamics of species in the wild is key to better understanding of evolution and maintenance of biodiversity
Do species with higher levels of among-individual diversity in functionally important traits—such as colour pattern— have higher average abundances and dampened population fluctuations compared with less diverse species, as predicted by theory [12,13,14,15,16]? Based on the analysis of 11-year timeseries data for 246 species of noctuid moths, we found that species with greater levels of inter-individual variation in colour pattern have higher average abundances and undergo smaller between-year abundance fluctuations compared with species having less variable or non-variable colour patterns
The association of abundance with colour pattern was evident after we statistically controlled for the potential effects that variation in niche width and adult flight period might have both on evolutionary modifications of variability (CV) in abundance (a) 1000 mean log abundance

Summary

Introduction

Exploring the causes and consequences of population dynamics of species in the wild is key to better understanding of evolution and maintenance of biodiversity. Identifying shared ecological characteristics that influence abundance fluctuations is crucial for a better understanding of local extinctions, recolonizations and range distribution shifts, and can aid the development of conservation management and pest control. We address the hypothesis that greater inter-individual genetic and phenotypic variability should shield against environmental change, enable faster growth, allow for higher densities and reduce fluctuations in population size [12,13,14,15,16,17]. Experimental investigations into the role of diversity for population fluctuations are rare, typically of short duration and conducted under controlled, relatively simple environmental conditions [18 –22]. The results of manipulation experiments can vary depending on ecological settings [23]; for instance, diversity has been found to exert stronger effects on population

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Discussion

Conclusion