WorldClim, elevation and distribution data for all palms from: The ecology of palm genomes: Repeat-associated genome size expansion is constrained by aridity

Genome size varies 2,400-fold across plants, influencing their evolution
through changes in cell size and cell division rates which impact plants’
environmental stress tolerance. Repetitive element expansion explains much
genome size diversity, and the processes structuring repeat ‘communities’
are analogous to those structuring ecological communities. However, which
environmental stressors influence repeat community dynamics has not yet
been examined from an ecological perspective. We measured genome size and
leveraged climatic data for 91% of genera within the ecologically diverse
palm family (Arecaceae). We then generated genomic repeat profiles for 141
palm species, and analysed repeats using phylogenetically-informed linear
models to explore relationships between repeat dynamics and environmental
factors. We show that palm genome size and repeat ‘community’ composition
are best explained by aridity. Specifically, Ty3-gypsy and TIR elements
were more abundant in palm species from wetter environments, which
generally had larger genomes, suggesting amplification. In contrast,
Ty1-copia and LINE elements were more abundant in drier environments. Our
results suggest that water stress inhibits repeat expansion through
selection on upper genome size limits. However, elements which may
associate with stress-response genes (e.g., Ty1-copia) have amplified in
arid-adapted palm species. Overall, we provide novel evidence of climate
influencing the assembly of repeat ‘communities’.