Functional morphology of a sarcocaulescent desert scrub in the bay of La Paz, Baja California Sur, Mexico

A functional morphology study of a sarcocaulescent scrub in the Baja California peninsula was performed with the goal of identifying plant functional types. We sampled 11 quadrats in three distinct physiographic units within the sarcocaulescent scrub ecoregion: the open scrub, the clustered scrub, and the closed scrub. We found 41 perennial species, which we characterized using 122 morphology-functional characteristics, corresponding to vegetative parts (stem and leaf), reproductive parts (flower and fruit), and functional phases (phenology, pollination, and dispersion). We used principal components analysis PCA to analyse the relationship between morphological attributes and species, between species and sites, and between morphological attributes and sites. Stem morphology was highly associated with groups of plant species and also with specific communities, forming recognizable stem-morphology syndromes. We also found that flower and fruit attributes are highly correlated with stem morphology. Our analysis allowed the clear identification of four morphological groups in our study area: (a) crassicaulescent plants, or succulent cacti, (b) sarcocaulescent species, (c) woody trees, and (d) woody shrubs. Cacti and sarcocaulescent plants dominate in the open scrub, woody shrubs dominate in the mounds of the clustered scrub, and woody trees, together with all the previous life-forms, form the more mesic closed scrub. Our results indicate that Forrest Shreve's classification of desert communities based on the external morphology of the plants is statistically robust and reflects a significant underlying pattern.