American Society of Naturalists

A membership society whose goal is to advance and to diffuse knowledge of organic evolution and other broad biological principles so as to enhance the conceptual unification of the biological sciences.

“Effects of clonal reproduction on evolutionary lag and evolutionary rescue”

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Maria E. Orive, Michael Barfield, Carlos Fernandez, and Robert D. Holt

Clonality and stage structure help or hinder evolutionary rescue depending on temporal texture of environmental change

First author Maria E. Orive.<br />(Credit: Mackenzie Johnson)
First author Maria E. Orive.
(Credit: Mackenzie Johnson)

In rapidly changing environments, organisms must constantly evolve in order to maintain the ability to survive and reproduce. Rapid change may take many forms, such as coevolving pathogens and diseases, other competing species, or changes in temperature or other climatic conditions. But evolution takes time, and a population experiencing a changing environment may not be able to evolve quickly enough to track that change.

The relative difference between the average value of a trait that affects the ability to survive and reproduce of a population, and the optimum for that trait is termed “evolutionary lag”. Many ecologically important organisms, such as reef-building corals and perennial grasses in prairies and savannahs, have life histories that include indeterminate growth and the existence of both asexual reproduction (via budding, fragmentation, or other types of clonal reproduction) and sexual reproduction (via the production of sperm and eggs). Yet how this type of life history structure and clonality interplay to govern a population’s rate of evolution and evolutionary lag is unknown.

Orive and her colleagues developed a general mathematical model to consider how traits evolve under both sexual and clonal reproduction. They found that the effect of clonal reproduction on the mean of a trait partitions into two portions: one that is dependent on the value of the trait itself (phenotype-dependent) and one that depends on the genetics underlying the trait (genotype-dependent). This partitioning is governed by the amount of “extra similarity” in the trait seen between parents and their clonal offspring, compared to that seen between parents and their sexual offspring.

Are clonally reproducing organisms at a disadvantage under changing environmental conditions? Not always. Clonality was seen to increase population persistence after a single, step-change in the environment, while it decreased population persistence under continuous, linear change requiring de novo variation. Thus, the impact of clonality on the probability of persistence for species in a changing world depends strongly on the temporal texture of the change they experience. Read the Article