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.

alkanes to be dominant. Quantitatively, the chromatograms varied significantly among populations. Multivariate analyses showed that arid zone populations from mediterranean Chile and the Patagonian steppe were different from one another and were distinct from mesic populations close to the Valdivian rainforest vegetation zone. Mediterranean Chilean populations were characterized by higher concentrations of the longer carbon-chain alkanes, but retained equal amounts of shorter-chain homologues as the mesic populations. A greater variation in chain lengths and higher concentrations of longer carbon chains in the mediterranean populations is consistent with a model for the adaptation to reduced cuticular permeability. Partial Mantel matrix tests revealed significant climatic and inter-population distance effects with taxonomic distances based on multivariate and univariate hydrocarbon data. Annual rainfall was overall the most significant factor, particularly in regressions with the shorter-chain hydrocarbons. Annual mean temperature was most significant for the longer-chain hydrocarbons. This suggests, on the one hand, ecogenic adaptation to both temperature and precipitation of cuticular hydrocarbon composition, and, on the other hand, a weaker, but important effect of gene flow in determining hydrocarbon composition in this species. The northernmost populations at San Felipe and San Gabriel were the most distinctive. This could result from the effects of random changes in allele frequencies and\or to founder effects in isolated and small populations. These populations show some East-Andean affinities presumably due to historic migration patterns.

No abstract

No abstract