Slow evolution of vertebrates with large genomes

TL;DR

This paper investigates how larger genome sizes in vertebrates are associated with slower rates of molecular evolution and reduced genetic diversity, shedding light on the evolutionary dynamics of 'living fossil' lineages.

Contribution

It demonstrates a correlation between increased genome size and decreased evolutionary rates and genetic diversity in vertebrates, highlighting genome size as a key factor in evolutionary processes.

Findings

Genetic diversity decreases with increasing genome size.

Average rates of molecular evolution decline as genome size increases.

Larger genomes are linked to slower evolutionary change.

Abstract

Darwin introduced the concept of the "living fossil" to describe species belonging to lineages that have experienced little evolutionary change, and suggested that species in more slowly evolving lineages are more prone to extinction (1). Recent studies revealed that some living fossils such as the lungfish are indeed evolving more slowly than other vertebrates (2, 3). The reason for the slower rate of evolution in these lineages remains unclear, but the same observations suggest a possible genome size effect on rates of evolution. Genome size (C-value) in vertebrates varies over 200 fold ranging from pufferfish (0.4 pg) to lungfish (132.8 pg) (4). Variation in genome size and architecture is a fundamental cellular adaptation that remains poorly understood (5). C-value is correlated with several allometric traits such as body size and developmental rates in many, but not all, organisms (6, 7). To date, no consensus exists concerning the mechanisms driving genome size evolution or the effect that genome size has on species traits such as evolutionary rates (8-12). In the following we show that: 1) within the same range of divergence times, genetic diversity decreases as genome size increases and 2) average rates of molecular evolution decline with increasing genome size in vertebrates. Together, these observations indicate that genome size is an important factor influencing rates of speciation and extinction.