PARENT SESSION
Poster Session # 21: Biogeography, Biodiversity, Populations, and Genetics.
Thursday, August 7 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Establishment patterns in a metapopulation of the epiphyte Tillandsia recurvata in a Mexican desert shrubland.
Bernal, Rocio*,1, Hernández, Laura1, Valverde, Teresa1, 1 Departamento de Ecología y Recursos Naturales, México, D.F., México
ABSTRACT- Tillandsia recurvata (Bromeliaceae) is an epiphyte that colonizes the canopies of shrubs and trees in the semidesert areas of Central Mexico. Each colonized tree may be conceived as a local population within a metapopulation. Little is known regarding the factors that determine patch selection in plant metapopulations. Here we aimed to describe patch occupancy, as well as microhabitat preferences in this epiphyte as a preliminary step to understand its metapopulation dynamics. We surveyed a 1ha plot in the Tehuacan Valley and recorded the position, size and species identity of every tree and shrub (N=1159), as well as the number of Tillandsia recurvata plants established in its canopy. We also carried out germination experiments, and observations on seedling survival and growth in different microhabitats within the canopy of three tree species. The results show that T. recurvata occupy certain tree species with a higher frequency than expected by chance. These preferred host species were Prosopis laevigata, Acacia bilimekii and Cercidium praecox, which were colonized with a frequency of 65-73%. Additionally, large trees were colonized more frequently than relatively smaller ones, and colonized trees had colonized nearest neighbors with a higher frequency than expected by chance. Seed germination was equivalent in the three host species tested (Prosopis laevigata, Acacia bilimekii and Cercidium praecox). However, seeds germinated better when located in the upper canopy (5.15%) than at medium heights (2.26%). Seedling survivorship after one year was higher on Acacia bilimekii (80.6%), followed by Cercidium praecox (65.4%) and Prosopis laevigata (45.9%). Seedling growth rate was highest in the outer-upper canopy of A. bilimekii. This study has allowed us to identify the colonizable patches for Tillandsia recurvata within this metapopulation, which is a key issue for the understanding of metapopulation dynamics in many plant species.
Key words: epiphytes, metapopulations, Tillandsia recurvata, habitat selection