title: Differentiation in the water-use strategies among oak species from central Mexico.
abstract: Oak species (Fagaceae: Quercus) differ in their distribution at the landscape scale, specializing to a certain portion of environmental gradients. This suggests that functional differentiation favors habitat partitioning among closely related species. To elucidate the mechanisms of species coexistence in oak forests, we explored patterns of interspecific variation in functional traits involved in water-use strategies. We tested the hypothesis that oak species segregate along key trade-offs between xylem hydraulic efficiency and safety, and between hydraulic safety and drought avoidance capacity, leading to species niche partitioning across a gradient of aridity. To do so, we quantified biophysical and physiological traits in four red and five white oak species (sections Lobatae and Quercus, respectively) across an aridity gradient in central Mexico. We also explored the trade-offs guiding species differentiation, particularly between the drought tolerance versus water acquisition capacity, and determined whether the water-use strategy was associated with the portion of the environmental gradient that the species occupy. In a trait-by-trait analysis, we detected differences between white and red oak species. However, a larger part of the variation was explained at the species rather than at the section level. We detected two primary axes of trait covariation. The first exhibited differences between species with dense tissues and species with soft tissues (the tissue construction cost axis); however, the oak sections did not constitute separate groups, while the second suggested a trade-off between xylem resistance to cavitation and tree deciduousness. As expected, the water-use strategies of the species were related to the environment; oak species from arid areas had more deciduousness and a higher instantaneous water-use efficiency. In contrast, their humid counterparts had less deciduousness and had a xylem that was more resistant to embolisms. Altogether, these results suggest that aridity filters closely related species, resulting in habitat partitioning and niche divergence.
authors.affiliation: Escuela Nacional de Estudios Superiores (ENES) Unidad Morelia, Universidad Nacional Autónoma de México (UNAM), Antigua Carretera a Pátzcuaro 8701, C.P. 58190, Morelia, Michoacán, México.|Laboratorio Nacional de Análisis y Síntesis Ecológica, (LANASE), ENES, Unidad Morelia, UNAM, Antigua Carretera a Pátzcuaro 8701, C.P. 58190, Morelia, Michoacán, México.
authors.forename: Rafael
authors.initials: R
authors.lastname: Aguilar-Romero
authors.affiliation: Escuela Nacional de Estudios Superiores (ENES) Unidad Morelia, Universidad Nacional Autónoma de México (UNAM), Antigua Carretera a Pátzcuaro 8701, C.P. 58190, Morelia, Michoacán, México.|Laboratorio Nacional de Análisis y Síntesis Ecológica, (LANASE), ENES, Unidad Morelia, UNAM, Antigua Carretera a Pátzcuaro 8701, C.P. 58190, Morelia, Michoacán, México.
authors.forename: Fernando
authors.initials: F
authors.lastname: Pineda-Garcia
authors.affiliation: Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Campus Morelia, Antigua Carretera a Pátzcuaro 8701, C.P. 58190, Morelia, Michoacán, México.
authors.forename: Horacio
authors.initials: H
authors.lastname: Paz
authors.affiliation: Laboratorio Nacional de Análisis y Síntesis Ecológica, (LANASE), ENES, Unidad Morelia, UNAM, Antigua Carretera a Pátzcuaro 8701, C.P. 58190, Morelia, Michoacán, México.|Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Campus Morelia, Antigua Carretera a Pátzcuaro 8701, C.P. 58190, Morelia, Michoacán, México.
authors.forename: Antonio
authors.initials: A
authors.lastname: González-Rodríguez
authors.affiliation: Escuela Nacional de Estudios Superiores (ENES) Unidad Morelia, Universidad Nacional Autónoma de México (UNAM), Antigua Carretera a Pátzcuaro 8701, C.P. 58190, Morelia, Michoacán, México.|Laboratorio Nacional de Análisis y Síntesis Ecológica, (LANASE), ENES, Unidad Morelia, UNAM, Antigua Carretera a Pátzcuaro 8701, C.P. 58190, Morelia, Michoacán, México.
authors.forename: Ken
authors.initials: K
authors.lastname: Oyama
mesh_terms: D055864:Droughts; D008800:Mexico; D029963:Quercus / Q000502:physiology*; D014197:Trees / Q000502:physiology; D014867:Water / Q000502:physiology*; D052584:Xylem / Q000502:physiology*
chemical_list: D014867:Water
keywords: Quercus; aridity gradients; biophysical traits; functional trade-offs; water-use strategy