Leaf chemical variation of seven legumes from the hyper-diverse tropical semi-arid ecosystem of Zapotitlán-Salinas Valley

Background: It has been suggested that niche differentiation could explain species coexistence in hyper-diverse tropical plant communities. Questions: Can we identify a specific and differentiated leaf chemical variation of seven coexisting legume species within the hyper-diverse tropical semi-desert? Are these differences related to their phylogeny? Studied species: Vachellia constricta, Parkinsonia praecox, Mimosa luisana, Neltuma laevigata, Vachellia campechiana, Vachellia bilimekii, and Senna wislizeni. Study site and date: Zapotitlán Salinas Valley in Mexico (August 2020). Methods: For each species we assessed nine foliar elements (hydrogen, carbon, nitrogen, phosphorus, calcium, magnesium, potassium, iron, and zinc). We constructed a phylogenetic tree from sequences of the GenBank database selecting the marker trnL chloroplast intron. Differences were assessed performing ANOVA, Principal Component Analysis and Spearman’s multiple correlation analyses. Results: Leaf chemical variation exhibited greater differentiation in phosphorus (associated to nucleic acids, protein construction and rapid growth rate), calcium and potassium (associated to structure and photosynthesis), and iron and zinc (associated to enzymes). Leaf chemical variation of more ancestral species displayed elevated concentrations of calcium and potassium, whereas most derived species exhibited higher carbon and iron concentrations. Species of the same genus showed less differences compared to more distant species. Conclusions: The foliar elemental composition may be a fingerprint trait of the ecological and evolutionary history of these legumes, in relation to nutrient assimilation and acquisition, and probably constitute a mechanism of coexistence.