Adaptive capacity in the foundation tree species Populus fremontii: implications for resilience to climate change and non-native species invasion in the American Southwest

Kevin R Hultine; Gerard J Allan; Davis Blasini; Helen M Bothwell; Abraham Cadmus; Hillary F Cooper; Chris E Doughty; Catherine A Gehring; Alicyn R Gitlin; Kevin C Grady; Julia B Hull; Arthur R Keith; Dan F Koepke; Lisa Markovchick; Jackie M Corbin Parker; Temuulen T Sankey; Thomas G Whitham

doi:10.1093/conphys/coaa061

Adaptive capacity in the foundation tree species Populus fremontii: implications for resilience to climate change and non-native species invasion in the American Southwest

Conserv Physiol. 2020 Jul 13;8(1):coaa061. doi: 10.1093/conphys/coaa061. eCollection 2020.

Authors

Kevin R Hultine¹, Gerard J Allan², Davis Blasini³, Helen M Bothwell⁴, Abraham Cadmus², Hillary F Cooper², Chris E Doughty⁵, Catherine A Gehring², Alicyn R Gitlin⁶, Kevin C Grady⁷, Julia B Hull², Arthur R Keith², Dan F Koepke¹, Lisa Markovchick², Jackie M Corbin Parker², Temuulen T Sankey⁵, Thomas G Whitham²

Affiliations

¹ Department of Research, Conservation and Collections, Desert Botanical Garden, 1201 North Galvin Parkway, Phoenix, AZ 85008, USA.
² Department of Biological Sciences and Merriam-Powell Center for Environmental Research, Northern Arizona University, 617 South Beaver Drive, Flagstaff, AZ 86011, USA.
³ School of Life Sciences, Arizona State University, 427 East Tyler Mall, Tempe, AZ 85281, USA.
⁴ Research School of Biology, Australian National University, 134 Linnaeus Way, Canberra ACT2601, Australia.
⁵ School of Informatics, Computing, and Cyber Systems, Northern Arizona University, 1295 South Knoles Drive, Flagstaff, AZ 86011, USA.
⁶ Sierra Club - Grand Canyon Chapter, 514 West Roosevelt Street, Phoenix, AZ 85003, USA.
⁷ School of Forestry, Northern Arizona University, East Pine Knoll Drive, Flagstaff, AZ 86011, USA.

Abstract

Populus fremontii (Fremont cottonwood) is recognized as one of the most important foundation tree species in the southwestern USA and northern Mexico because of its ability to structure communities across multiple trophic levels, drive ecosystem processes and influence biodiversity via genetic-based functional trait variation. However, the areal extent of P. fremontii cover has declined dramatically over the last century due to the effects of surface water diversions, non-native species invasions and more recently climate change. Consequently, P. fremontii gallery forests are considered amongst the most threatened forest types in North America. In this paper, we unify four conceptual areas of genes to ecosystems research related to P. fremontii's capacity to survive or even thrive under current and future environmental conditions: (i) hydraulic function related to canopy thermal regulation during heat waves; (ii) mycorrhizal mutualists in relation to resiliency to climate change and invasion by the non-native tree/shrub, Tamarix; (iii) phenotypic plasticity as a mechanism for coping with rapid changes in climate; and (iv) hybridization between P. fremontii and other closely related Populus species where enhanced vigour of hybrids may preserve the foundational capacity of Populus in the face of environmental change. We also discuss opportunities to scale these conceptual areas from genes to the ecosystem level via remote sensing. We anticipate that the exploration of these conceptual areas of research will facilitate solutions to climate change with a foundation species that is recognized as being critically important for biodiversity conservation and could serve as a model for adaptive management of arid regions in the southwestern USA and around the world.

Keywords: Canopy thermal regulation; hybridization; local adaptation; mycorrhizal mutualists; phenotypic plasticity; unmanned airborne remote sensing.