Author(s): Victoria RicoGray, Monica PalaciosRios
In this study we demonstrate that there is a significant variation in mean leaf area of Rhizophora mangle L. along a latitudinal gradient (15⚬ N to 24⚬ N) in Mexico, and that this variation is significantly correlated with latitude and total annual precipitation per site. Mean leaf area of R. mangle and total annual precipitation increase significantly from north to south along the latitudinal gradient (χ2 = 56.57, n = 27, P<0.001; χ2 = 15989.96, n = 27, P<0.001, respectively). There is a significant negative association between latitude and mean leaf area, and between latitude and total annual precipitation (both, r2 = -0.5, n-27, P<0.001). Correlation between total annual precipitation and leaf area is not as strong (r2 = 0.3, n = 27, P<0.01). Our results show that mean leaf area of R. mangle increases significantly as latitude decreases and precipitation increases, but it seems improbable that it would increase continuously if we should continue the latitudinal gradient up to the equator. This is probably due to the combined effect of energy optimization and moisture maximization year-round, the nonlinear temperature gradient between the equator and the poles, and to geographical heterogeneity (e.g. proximity of mountain ranges, or warm or cold ocean currents).