Plant evolution in fire-prone environments

My dissertation work examines fire as a selective force in plant evolution. My investigation of sprouter and nonsprouter growth rates (Chapter 2) examines intra-specific variation in the ability to resprout after fire. This work on closely related sprouters and nonsprouters attempts to shed light on the evolutionary implications of the loss of resprouting ability.; Chapters 3–5 examine the possible evolutionary role of plant flammability. Plants are not only shaped by the selective environment that fire creates, but, as fuel, plants can influence the nature of the fire they experience. In Chapter 3, I use phylogenetic comparative methods to test for an evolutionary correlation between fire response traits and flammability in pines. This work reveals a pattern of correlation evolution in which evolutionary increases in flammability have been associated with increases in fire-dependent recruitment.; Chapter 4 answers critics who have charged that flammability is not a trait upon which evolution can act. In this chapter, I test whether a potential flammability trait that varies in nature can have local effects on fire intensity. My experimental manipulation of shrub canopy architectures revealed that one candidate flammability trait, dead branch retention, can significantly increase fire temperatures. This work suggests that plants may indeed influence the nature of fire they experience.; Chapter 5 examines whether increased flammability can evolve under natural selection. In this simulation model, flammability evolves due to an association between an allele that promotes flammability and alleles at unlinked loci that give high fitness. Flammability behaves as a spatial modifier of generation time. My co-author, Ben Kerr, and I term this process “genetic niche-hiking.” More generally, “genetic niche-hiking,” can explain the evolution of altruistic traits in spatially-structured systems.; Ecologists have long viewed fire as a destructive force to which plants have responded through the evolution of life-history strategies that allow species to cope with this powerful force. My thesis work suggests that a more full view of fire and plant evolution should include the possibility that plants are authors of their own evolution. Plants may be shaping their environment, and in doing so, changing the nature of fire that they and their offspring experience.