SEED GERMINATION AND POPULATION STRUCTURE OF TWO ENDANGERED TREE SPECIES: MAGNOLIA PEREZFARRERAE AND MAGNOLIA SHARPII

Background: Due to habitat fragmentation many Magnolia species are at risk of extinction in Mexico. Question: What type of population structure is exhibited by Magnolia perezfarrerae and M. sharpii, endemic species of Chiapas, Mexico? Does the extreme reduction in the population of both Magnolia affect their reproductive capacity? What is the propagation potential in both species of Magnolia? Is it necessary to use pregerminative treatments for Magnolia species propagation? Studied species: Magnolia perezfarrerae A. Vazquez & Gomez-Dominguez and Magnolia sharpii Miranda. Study sites and years of study: Highlands and Central Depression of Chiapas, Mexico, from 2015 to 2017. Methods: In this study, the density and distribution of diametric sizes of M. perezfarrerae and M. sharpii were assessed in natural populations. Their reproductive capacity and the ex-situ germination of both species was analyzed. Results: The population density in M. perezfarrerae was 40-53 ind. ha(-1), and 24-83 ind. ha(-1) in M. sharpii. Size structure varied between populations of each species: one apparently without problems of regeneration, and another with discontinuous distribution in several size categories. The seeds presented physical, chemical and mechanical dormancy. The pre-germination treatments applied proved mostly effective for M. sharpii by 73 % and by 64 % for M. perezfarrerae. Conclusions: The current condition of Magnolia species is critical and their persistence is compromised. Any viable conservation option would need to identify potential sites for the reintroduction of new populations.