Genome streamlining and clonal erosion in nutrient-limited environments: a test using genome-size variable...

Area of Science:

• Evolutionary biology
• Genomics
• Ecology

Background:

• Selection-based theories suggest genome streamlining (smaller genomes) is advantageous in nutrient-limited environments, especially under phosphorus (P) limitation.
• Rotifers, a group of micro-animals, exhibit intraspecific variation in genome size and can reproduce asexually, making them suitable models for studying genome evolution.

Purpose of the Study:

• To experimentally test the hypothesis that genome streamlining is favored under nutrient-limited conditions.
• To investigate the role of genome size (GS) variation in clonal competition and adaptation during experimental evolution.

Main Methods:

• Experimental evolution trials were conducted on clonal populations of a facultatively asexual rotifer with existing genome size variation.
• Populations were subjected to conditions including phosphorus (P)-limitation.
• Common garden transplant experiments were used to assess adaptation of evolved populations.

Main Results:

• Clonal diversity rapidly declined in most trials, irrespective of P-limitation.
• Evolved populations showed improved adaptation to experimental conditions.
• Contrary to expectations, evolved populations did not favor smaller genomes; intermediate genomes were common, while very large genomes were rare.

Conclusions:

• Fitness in this rotifer system is primarily influenced by genotypic differences among clones, rather than genome size.
• Genome streamlining may not be a universal outcome of adaptation to nutrient-limited environments.
• Genotypic variation can potentially impede genome streamlining during early adaptation stages.