title: Phenological mismatch and the effectiveness of assisted gene flow.
abstract: The persistence of narrowly adapted species under climate change will depend on their ability to migrate apace with their historical climatic envelope or to adapt in place to maintain fitness. This second path to persistence can only occur if there is sufficient genetic variance for response to new selection regimes. Inadequate levels of genetic variation can be remedied through assisted gene flow (AGF), that is the intentional introduction of individuals genetically adapted to localities with historic climates similar to the current or future climate experienced by the resident population. However, the timing of reproduction is frequently adapted to local conditions. Phenological mismatch between residents and migrants can reduce resident × migrant mating frequencies, slowing the introgression of migrant alleles into the resident genetic background and impeding evolutionary rescue efforts. Focusing on plants, we devised a method to estimate the frequency of resident × migrant matings based on flowering schedules and applied it in an experiment that mimicked the first generation of an AGF program with Chamaecrista fasciculata, a prairie annual, under current and expected future temperature regimes. Phenological mismatch reduced the potential for resident × migrant matings by 40-90%, regardless of thermal treatment. The most successful migrant sires were the most resident like in their flowering time, further biasing the genetic admixture between resident and migrant populations. Other loci contributing to local adaptation-heat-tolerance genes, for instance-may be in linkage disequilibrium with phenology when residents and migrants are combined into a single mating pool. Thus, introgression of potentially adaptive migrant alleles into the resident genetic background is slowed when selection acts against migrant phenology. Successful AGF programs may require sustained high immigration rates or preliminary breeding programs when phenologically matched migrant source populations are unavailable.
authors.affiliation: Department of Genetics, University of Georgia, 120 Green Street, Athens, GA, 30602-7223, U.S.A.
authors.forename: Susana M
authors.initials: SM
authors.lastname: Wadgymar
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, M5S 3B2, Canada.
authors.forename: Arthur E
authors.initials: AE
authors.lastname: Weis
mesh_terms: D005075:Biological Evolution; D057231:Climate Change; D003247:Conservation of Natural Resources; D051456:Gene Flow; D014644:Genetic Variation; D012621:Seasons
keywords: Chamaecrista fasciculata; assisted migration; assortative mating; cambio climático; climate change; emparejamiento selectivo; flowering time; flujo génico no-azaroso; genetic rescue; migración asistida; migration rate; nonrandom gene flow; rescate génico; tasa migratoria; tiempo de florecimiento