Physiological responses to climate change may help explain changes in distribution ranges of sympatric cactus from Southeastern Mexico

Background/Question/Methods

The objective of this study was to explain range shifts of two sympatric cacti from Yucatan, Mexico, due to climate change using physiological tools. I measured the responses of CO₂ uptake to temperature, water and light for Mammillaria gaumeri and Opuntia stricta and developed an environmental productivity index (EPI) to model their monthly and annual productivity. Additionally, I measured their tolerance to extreme high temperatures and drought. Using a maximum entropy method (Maxent), I modeled their current and predicted their distributions. 

Results/Conclusions

Mammillaria gaumeri will increase its distribution range. This is potentially explained by its physiological responses: it is more tolerant to extreme high temperatures and drought, and will increase its CO₂ uptake and productivity under climate change scenarios. In contrast, Opuntia stricta, a less tolerant species to extreme high temperatures and drought, will reduce its CO₂ uptake and productivity. Accordingly, its distribution range will decrease, increasing the probability of local extinction.