Evolutionary genetics of mangroves: continental drift to recent climate change

Abstract.

Recent advances in our knowledge of the genetic architecture of mangrove species are reviewed and the consequences of this genetic architecture for species response to environmental change are inferred. The origins of mangrove taxa have been discussed many times, particularly in the context of centers of origin and continental drift. While global patterns of mangrove species diversity have been interpreted in the context of tectonic events and opening and closing of seawater passages, species evolution on a finer scale depends on more recent processes of population extinction and advances in response to spatio-temporal climatic and environmental flux. Understanding the likely effects of global climate change on mangrove distributions requires a focus on these more recent intraspecific evolutionary processes. Many mangrove taxa have wide geographic ranges that have been attributed to efficient propagule dispersal. Such gene flow should provide a genetic cohesiveness among populations. However, as with many wide-ranging marine organisms, we are finding important population genetic structure in widespread mangrove species, suggesting that gene flow is less effective than previously thought. Are these widespread taxa more recent and undergoing speciation? Spatial patterns in genetically adaptive traits indicate that some populations may survive more successfully under changing environmental conditions. However, is the present-day genetic architecture best poised to respond to predictions of climate change? These questions are addressed in the light of our increasing knowledge of genetic diversity in mangrove species.