UC Irvine

Climate change will affect populations differentially through space and time. These impacts will also vary depending on species’ life history strategies and the nativity of the species in question. Long-lived perennial plant species may be resilient to short-term or even within season drought stress and may only respond to long-term climate change given their generation times. At the same time, annual plant populations may respond rapidly to change given their short generation times and relatively direct selection pressures. However, which climate drivers and how they will impact populations through space and time remain poorly understood. Thus, this dissertation aims to fill in these gaps by examining: (i) the influence of drought on populations of the long-lived, protected saguaro cactus (Chapter 1), (ii) the ability of a dwarf bamboo to alter its growth strategies in response to changes in soil hydrology, thereby enabling its invasion into new habitats (Chapter 2), (iii) the genetic structure of the rapidly invading Sahara mustard in the southwestern US (Chapter 3), and (iv) Sahara mustard’s capacity to adapt to variable water limitation across its invaded range (Chapter 4). Overall, this dissertation examines the influence of climate change on plant species at multiple scales and biological and conservation categories. In doing so, this dissertation tackles questions in evolutionary and population biology and provides advice for land managers working to conserve protected species and control invasive species.