| Resumo: |
Leaf morphology was measured and aerodynamical attributes as well as transpiration rates were calculated for the mangrove Conocarpus erecta from sites naturally sheltered or sites exposed to oceanic winds at Socorro Island, Mexico, and compared with those of C. erecta, Laguncularia racemosa, and Rhizophora mangle at a mainland estuary near La Manzanilla, Jalisco, Mexico. Leaves of C. erecta, 5.98 cm in length and 2.03 cm in width, were the smallest and most streamlined of the mainland mangroves. Moreover, both leaf dimensions were 32 % smaller for trees from the exposed sites on Socorro Island than on the mainland. For a given wind velocity, Reynolds numbers were 10 to 33 % lower at Socorro Island than on the mainland for leaves of C. erecta, leading to a 17 to 45 % lower drag force exerted by wind on such leaves. Reynolds numbers characterize the degree of turbulence of a fluid moving adjacent to the surface of an object; here such a dimensionless number was used as a measure of fluttering for leaves. Transpiration rates for C. erecta were 25 % lower for plants growing at exposed sites on Socorro Island than on the sheltered sites, whose midday transpiration averaged 4 mmol m_2 s_1. Conocarpus erecta was better suited than the other mainland mangroves to windy environments owing to its smaller and more streamlined leaves. The population from Socorro Island underwent further morphological changes in response to wind at exposed sites, explaining, in part, the presence of this species and not of other mangroves on this oceanic Pacific island
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