Life-history variation across the range of California poppy influences population-level responses to experimental climate manipulations

Background/Question/Methods

Species often display genetic and phenotypic variation among populations, especially widespread species whose ranges span broad climatic gradients. Clinal variation (e.g. continuous ecotypic variation) in traits can reveal how climate has influenced the history of past selection, and provides a window into the potential for species to adapt to modern climate change. Life-history strategy can also vary across species ranges, complicating predictions regarding species responses to climate change. California poppy (Eschscholzia californica) is a widespread species that has both annual and perennial populations. Here, we investigated the response to experimental climate manipulation of 20 populations found across a fourfold gradient in annual precipitation. In a field common garden, plants received precipitation treatments approximating the wettest and driest sites, crossed with the presence and absence of a 1.5°C warming treatment.

Results/Conclusions

We documented clinal variation across populations; plants from southern populations (arid sites) were more likely to survive to flower, have an annual life history, have higher seed set, higher population growth rates and higher elasticities to fecundity, than northern, mesic, populations. Plants had higher growth rates, seed set and rates of survival to flowering under warmer and wetter conditions, with the greatest increases in fitness in response to warming for the populations collected from more arid sites. Our findings suggest that populations with an annual life history are best poised to benefit from future warming associated with climate change, and that restoration success might be improved from sourcing seeds from this portion of the species range.