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Abiotic factors similarly shape the distribution of fruit, seed and leaf traits in tropical fleshy-fruited tree communities

Abstract:

The distribution of plant traits is related to abiotic and biotic factors, but it is unknown whether different types of plant traits respond similarly to these factors. We simultaneously studied seed, fruit and leaf traits and their associations with abiotic and biotic factors for tree communities in the tropical mountains of southern Ecuador. We measured seed, fruit, and leaf traits on 18–33 fleshy-fruited plant species and recorded the abundance for these species on nine 1-ha forest plots located at 1000, 2000, and 3000 m a.s.l. On the same plots, we recorded abiotic (soil C/N ratio, mean temperature, and annual rainfall) and biotic factors (avian fruit removal and foliar herbivory) potentially relevant for the measured traits. We conducted principal component and RLQ analyses to test for trait-environment covariation, controlling for phylogenetic relatedness and spatial autocorrelation. We identified a trade-off between (i) seed number and seed size and between (ii) the production of few costly (nitrogen-rich) vs. many cheap (carbon-rich) fruits. Likewise, leaf trait variation was primarily associated with (i) the leaf economics spectrum and (ii) leaf size. Controlling for phylogenetic and spatial covariation, seed, fruit and leaf traits were associated with abiotic and, to a lesser extent, with biotic factors. Fruit and leaf traits linked to production costs were mainly related to soil C/N ratios, whereas traits associated with the size of seeds, fruits, and leaves were related to rainfall. Our study suggests that associations between seed, fruit and leaf traits and the abiotic environment follow similar principles in tropical tree communities.