Climate refugia have been presented as possible mechanism allowing species to survive rapid climate shifts (e.g. Keppel et al. 2012, 2015; Franklin et al. 2014; Barrows and Fisher 2014; Barrows et al. 2016). Modeling where climate refugia might occur is straightforward; zones of overlap between current distribution models and climate-shifted models could be such refugia. My question relates to both validating such models, and more to the point what are the population metrics that might characterize a population residing in a climate refugia? Here in California we have (possibly) emerged from a 5-year drought that may have been a window into how populations behave in response to climate change-like conditions. We are tracking communities/populations of lizards across a broad elevation gradient. None went extinct; all declined during the worst of the drought but then behaved differently along this gradient as the drought became less severe.
1. some have remained at drought-level densities even after near-average rainfall returned.
2. some population densities increased linearly and others exponentially with increasing rainfall.
3. Some maintained at least moderate to expected levels of reproductive recruitment even during the worst dry years, while others showed little or no recruitment until the near-average rains returned.
Conceptually, how should a population behave during severe climate change-like conditions, and can we use those responses to identify and/or validate the location of climate refugia?
There will likely be a range of responses connected to changing biotic relationships to drought. We are publishing results from Organ Pipe lizards showing that a presumably predation-sensitive species increased during a drought era, whereas arboreal species fluctuated by did not decline overall, probably due to the buffering effects of long-lived, realtively drought-resistaent trees they live in or around. Yet ultimately we expect climate change to eliminate this resource entirely, making these perhaps among the most threatened lizards.
Although all species we studied responded positively to ppt, the effect was not strong and tended to be reversed during longer runs of high ppt.
From this, I suggest that species least limited by dominant interacting species may respond most directly as expected to ppt. Yet these may be species that do fine, existing in some relatively uncomplicated proportion to the limiting resource.
None of the species we studied were likely strong competitors with each other, as we didn't analyize the full set that includes congeners separating by habitat. I think such species pairs present special cases, as with the Sceloporus in Mexico.
My take is that revealing mechanisms is the way toward viable prediction of climate sensitivity, and then testing those predictions.
As in the referred Californean cases, the current extreme climatic events are within the range found over the Holocene in the attached case study. We found that size of the available refugia may be relevant as predicted by the Island Theory.
Article Fine resolution distribution modelling of endemics in Majell...
I think in Costa Rica there are some examples with bats in Monteverde.
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