Boom-bust population dynamics drive rapid genetic change

Area of Science:

• Ecology
• Evolutionary Biology
• Genetics

Background:

• Environmental changes and extreme perturbations threaten species, leading to population declines and loss of genetic diversity.
• Australia's arid zone experiences severe population fluctuations, yet some species persist and maintain genetic diversity.

Purpose of the Study:

• Investigate the genetic consequences of repeated population fluctuations in two Australian arid zone small mammals.
• Understand how genetic diversity is maintained in highly variable environments.

Main Methods:

• Repeated population sampling over 13 years.
• Genotype-by-sequencing of 1903 individuals.
• Analysis of heterozygosity and population differentiation (FST).

Main Results:

• The sandy inland mouse (Pseudomys hermannsburgensis) showed decreased heterozygosity and increased FST during population busts, with rapid restoration during booms.
• The lesser hairy-footed dunnart (Sminthopsis youngsoni) maintained stable population sizes and showed no linear declines in heterozygosity.
• Two contrasting mechanisms of genetic diversity maintenance were identified.

Conclusions:

• Species in variable environments can maintain genetic diversity through stable population sizes or rapid genetic mixing during population recovery.
• Pseudomys hermannsburgensis conserves diversity through rapid genetic mixing, while Sminthopsis youngsoni does so by maintaining stable populations.