Developmental evolution facilitates rapid adaptation

Hui Lin,Michael Travisano,Romas J Kazlauskas

doi:10.1038/s41598-017-16229-0

Hui Lin, Michael Travisano + Show 1 more

Open Access

https://doi.org/10.1038/s41598-017-16229-0

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Abstract

Developmental evolution has frequently been identified as a mode for rapid adaptation, but direct observations of the selective benefits and associated mechanisms of developmental evolution are necessarily challenging to obtain. Here we show rapid evolution of greatly increased rates of dispersal by developmental changes when populations experience stringent selection. Replicate populations of the filamentous fungus Trichoderma citrinoviride underwent 85 serial transfers, under conditions initially favoring growth but not dispersal. T. citrinoviride populations shifted away from multicellular growth toward increased dispersal by producing one thousand times more single-celled asexual conidial spores, three times sooner than the ancestral genotype. Conidia of selected lines also germinated fifty percent faster. Gene expression changed substantially between the ancestral and selected fungi, especially for spore production and growth, demonstrating rapid evolution of tight regulatory control for down-regulation of growth and up-regulation of conidia production between 18 and 24 hours of growth. These changes involved both developmentally fixed and plastic changes in gene expression, showing that complex developmental changes can serve as a mechanism for rapid adaptation.

Highlights

Developmental evolution has frequently been identified as a mode for rapid adaptation, but direct observations of the selective benefits and associated mechanisms of developmental evolution are necessarily challenging to obtain
Developmental evolution provides a potential mechanism for rapid adaptation, even for small populations
Even under the conditions that lack the filter paper and in which the ancestral genotype rapidly goes extinct, the risk of extinction was eliminated in six of ten derived populations (Fig. 1b). These results indicate that T. citrinoviride rapidly evolved and the derived populations could persist in previously unsuitable conditions

Summary

Introduction

Developmental evolution has frequently been identified as a mode for rapid adaptation, but direct observations of the selective benefits and associated mechanisms of developmental evolution are necessarily challenging to obtain. Understanding the interplay between developmental and evolutionary processes has proven challenging, at the microevolutionary scale To address these issues, we use selection on experimental populations of the filamentous fungus Trichoderma citrinoviride to determine the potential and basis for rapid adaptation. Its growth is dramatically altered in submerged liquid culture[10], in which asexual conidiation is suppressed and mycelia form large multicellular aggregates (Fig. 1a) We expected these minimal survival conditions to select for increased dispersal, and if there were evolutionary responses, that they would involve changes in growth form or spore production

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