Sodium as a catalyst for herbivore performance: A geographical perspective

Herbivores are candidates for sodium limitation as they maintain sodium tissue concentrations of 100-1000 times that of plants. We sampled across 54 US grasslands to examine how the geography of sodium affects arthropod abundance and conducted sodium addition experiments. Herbivore abundance increased by 50% with sodium addition. Environmental sodium levels did not predict herbivore abundance. However, arthropod attraction to sodium addition decreased with increasing plant sodium levels, indicating sodium satiation. Our results demonstrate that insect herbivores are often sodium limited and increases in sodium availability have the potential to increase arthropod abundance and herbivory.