Host suitability for germination differs from that of later stages of development in a rare epiphytic orchidAbstract
We explore phorophyte suitability for germination and establishment of the epiphytic orchid, Psychilis kraenzlinii. We found that the orchid grows on a subset of the available tree species and shows preference for the endemic Machaonia portoricensis (Rubiaceae). The orchid preferred trees with smoother bark, high water holding capacity and low water retention capacity. Microclimatic conditions under which embryos began pre-germination stages mirrored that of the adult orchid, but germination did not, suggesting that suitable germination sites are not necessarily the best sites for later stages of development.
Keywords: community dynamics; epiphytes; germination; phorophytes; population dynamics; Orchidaceae
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B. Average number of P. kraenzlinii growing on the most common phorophyte species (Plus sign (+) marks a positive and significant association, whereas minus sign (-) marks a negative significant association.Associations based on residuals from Fisher Exact Test with Monte Carlo Simulation (p < 0.05, simulations = 2000).
B. Box plots of the fissuring index of the bark of trees with and without Psychilis kraenzlinii among phorophyte species.Randia aculeata and Swietenia mahagoni not shown because data of trees with a P. kraenzlinii was not available.Red brackets with asterisks mark significant differences where: * = p ≤ 0.05; **= p ≤ 0.01; ***= p ≤ 0.001.
Where Stage 1 refers to seeds with swollen embryos, Stage 2 are seeds whose embryo have swelled to the point of breaking the testa, Stage 3 the testa is gone and the protocorm is formed, and Stage 4 the protocorm has elongated.For Ouratea littoralis, no seeds developed near an established P. kraenzlinii, whereas in the case of Coccoloba microstachya and Randia aculeata, no packets were placed near and established orchid.Red lines indicate significant differences according to Conover-Iman Pairwise Comparisons (p<0.05).
Photos by N. González-Orellana.A. Pictures of the bark surface of Coccoloba microstachya taken with a camera coupled to a dissecting microscope and a ring light. B. Pictures of the bark surface of Phyllanthus cuneifolius taken with a camera coupled to a dissecting microscope and a ring light. C. Photos converted to black and white (binary) images of C. microstachya. D. Photos converted to black and white (binary) images of P. cuneifolius. Enclosed in red is the area where roughness interpretation could be affected by bark pigmentation.