Abstract
Interactions between species are widely understood to have promoted the diversification of life on Earth, but how interactions spur the the formation of new species remains unclear. Interacting species often become locally adapted to each other, but they may also be subject to shared dispersal limitations and environmental conditions. Moreover, theory predicts that different kinds of interactions have different effects on diversification. To better understand how species interactions promote diversification, we compiled population genetic studies of host plants and intimately associated herbivores, parasites, and mutualists. We used Bayesian multiple regressions and the BEDASSLE modeling framework to test whether host and associate population structures were correlated over and above the potentially confounding effects of geography and shared environmental variation. We found that associates’ populations structure often paralleled that of their hosts, and that this effect is robust to accounting for geographic distance and climate. Associate genetic structure was significantly explained by plant genetic structure somewhat more often in antagonistic interactions than in mutualistic ones. This aligns with a key prediction of co-evolutionary theory, that antagonistic interactions promote diversity through local adaptation of antagonists to hosts, while mutualistic interactions more often promote diversity via the effect of hosts’ geographic distribution on mutualists’ dispersal.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
- Revised handling of genetic data for species pairs with original genotype data available - Added formal test for publication bias - Added analysis in the BEDASSLE framework - Revised Introduction and Discussion text