Several recent studies have shown associations of leaf functional traits with habitat specialization across a wide range of tropical tree species. In this study, we focused on a speciose genus, Inga (Fabaceae) in the wet tropical forest at La Selva Biological Station, Costa Rica. Inga species at La Selva show habitat preference to rich alluvial soil or infertile residual soil of volcanic origin, or are generalists found on both soil types. We quantified lamina area, leaf mass per area (LMA) for seedlings (7 spp.), saplings (7 spp.) and adults (9 spp.), and also lamina thickness and tissue density for saplings and adults. Leaves were collected from 5-10 individuals per species of saplings (1-3 m tall) and adults in situ and from shadehouse grown seedlings at standardized ontogenetic stage.

Results/Conclusions

In all species, LMA values increased through ontogeny, seedlings having the lowest values and adults the highest values. Leaf lamina thickness and density values also increased from saplings to adults for most species. Across species, trait values were correlated between adults and saplings, while seedling trait values were not correlated with those of later stages. For both adults and saplings, LMA differed in relation to soil-type specialization; the residual soil specialists had higher values than alluvial specialists and the generalist species fell in the middle. Leaf lamina thickness did not show association with soil types. The results indicate that leaf tissue density, rather than lamina thickness, is the aspect of LMA that changes in acclimation or adaptation to soil nutrient availability.