UC Riverside

Understanding species responses to climate change is a topic of increasing concern given climate change projections. Niche models evaluate species vulnerabilities to climate change using current locations to project future habitat suitability under climate scenarios. However, these models are simplified and ignore other factors such as life history traits, catastrophes, or variability of vital rates. Therefore, in these three studies, I have used spatially explicit metapopulation models to evaluate species responses to global changes and variability in vital rates. The first study linked metapopulation models including stochastic fire events with niche models to evaluate the response of an obligate fire seeding shrub to simultaneous altered fire frequencies and shifting habitat due to climate change. For this species, altered fire regimes greatly reduced expected minimum abundances (EMAs). Climate change, on the other hand, only negatively affected the species under extreme scenarios. Therefore, altered fire regimes were the bigger threat to the species. The second study integrated fecundity and survival information from a translocation experiment into metapopulation models incorporating habitat suitability changes from a niche model. While the niche model projected overall increases in habitat for the species, the metapopulation model projected declining abundances within currently occupied patches due to declines in habitat suitability. Increased fecundity and survival rates sometimes mitigated the impact of these declines. The third study was an extensive sensitivity analyses of metapopulation models for two species, one obligate fire seeding shrub and one resprouter. Changes in the variability and means of vital rates, as well as changes in fire regime, dispersal, and variability of carrying capacity were integrated in separate scenarios. The obligate seeder was more vulnerable to altered fire regimes while the resprouter was more vulnerable to changes in vital rates. Both species were sensitive to increased variation of carrying capacity. Overall, all of the three studies indicate increasing the complexity of models can change the direction of results, and that different factors are influential for different species. Species were vulnerable to altered fire regimes and vital rates in particular, while habitat suitability changes caused by climate change sometimes affected minimum abundances.