Endopolyploidy as a potential driver of animal ecology and evolution

Abstract

Endopolyploidy - the existence of higher-ploidy cells within organisms that are otherwise of a lower ploidy level (generally diploid) - was discovered decades ago, but remains poorly studied relative to other genomic phenomena, especially in animals. Our synthetic review suggests that endopolyploidy is more common in animals than often recognized and probably influences a number of fitness-related and ecologically important traits. In particular, we argue that endopolyploidy is likely to play a central role in key traits such as gene expression, body and cell size, and growth rate, and in a variety of cell types, including those responsible for tissue regeneration, nutrient storage, and inducible anti-predator defences. We also summarize evidence for intraspecific genetic variation in endopolyploid levels and make the case that the existence of this variation suggests that endopolyploid levels are likely to be heritable and thus a potential target for natural selection. We then discuss why, in light of evident benefits of endopolyploidy, animals remain primarily diploid. We conclude by highlighting key areas for future research such as comprehensive evaluation of the heritability of endopolyploidy and the adaptive scope of endopolyploid-related traits, the extent to which endopolyploid induction incurs costs, and characterization of the relationships between environmental variability and endopolyploid levels.

Impacts of Nitrogen and Phosphorus: From Genomes to Natural Ecosystems and Agriculture

“…A definitive answer to the question of the extent to which larger genome sizes and higher ploidal levels translate into N and P costs will require characterization of organismlevel consequences. For example, the increased N and P demands could be offset by the lower number of cells that are sometimes, but not always, associated with larger genomes (Neiman et al, 2017). Demands may also be offset by more efficient allocation of cellular P to RNA.…”

Patterns of genome size variation in snapping shrimp

“…Gill tissue has previously been used in genome size studies in crustaceans, and is a diploid tissue whose nuclei show intermediate levels of compaction relative to muscle cells or haemolymph (Deiana et al 1999;Jeffery and Gregory 2014). This method allowed us to avoid measuring any nuclei from endopolyploid tissues, which are common in crustaceans (Neiman et al 2015). The resulting cell suspension was then flattened with a coverslip that was held onto the slide by three clothespins.…”

Genome size in arthropods; different roles of phylogeny, habitat and life history in insects and crustaceans

“…Gene duplication could be beneficial by increasing the expression of fitness‐promoting gene products, as has been suggested for endopolyploidy, that is increased ploidy levels of specific tissues (Neiman, Beaton, Hessen, Jeyasingh, & Weider, 2015), but may also be nonadaptive. Potential benefits of increased accumulation of non‐protein‐coding elements are even less evident, despite the fact that genomes of most eukaryotic organisms are dominated by such elements.…”