Niche construction on environmental gradients: the formation of fitness valley and stratified genotypic distributions.

Xiaozhuo Han,Cang Hui

doi:10.1371/journal.pone.0099775

Xiaozhuo Han, Cang Hui

Open Access

https://doi.org/10.1371/journal.pone.0099775

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Abstract

The process of niche construction can alter the trajectory of natural selection through organism-environment feedback. As such, the mechanism and impact of niche construction can be better investigated along environmental gradients. Here we investigate how the process of niche construction affects the distribution of genotypes and fitness landscape along an environmental gradient under three selection regimes, namely heterozygote superiority, genetic loci which dictates niche construction ability being either selectively neutral or non-neutral. Using a spatially explicit cellular automaton, we show that niche construction can stratify genetic diversity by forming band-like distributions consisting of different genotypic compositions and promote reproduction isolation by forming a divide with reduced average fitness along the gradients, termed a fitness valley. The band structure and the presence of a fitness valley depend on heterogeneous environments, resource-dependent fitness and the selection acting on the gene loci affecting the niche-constructing ability. Our work adds to the growing body of evidence on criticizing species distribution models which assume that the environment alone can determine species distributions. Based on the results, we argue that conservation planning should target preserving or restoring environmental gradients.

Highlights

Organisms are not passively selected by their ambient environment but coevolve with their environment through either direct niche construction or indirect life-history activities [1,2,3,4,5,6]
With the increase of positive niche construction intensity (l2), this stepwise form further shifted towards the direction of lower resources (Fig.2A), and the genotypic distribution was transferred from a double-band to a triple-band pattern (Fig.2B)
When further examining the average fitness of the individuals on each row, we found that the fitness landscape along the environmental gradient formed a valley at the intermediate resource level where the transition of genetic composition occurred (Fig.3B & F)

Summary

Introduction

Organisms are not passively selected by their ambient environment but coevolve with their environment through either direct niche construction ( called ecosystem engineering; e.g. digging burrows and spreading webs) or indirect life-history activities (e.g. photosynthesis in plants that can fix atmospheric carbon into the soil and dramatically alter the soil profile) [1,2,3,4,5,6]. It is important to further assess how the process of niche construction affects the genetic structure and fitness landscape along environmental gradients.

Results

Conclusion