Seed germination and population structure of two endangered tree species: Magnolia perezfarrerae and Magnolia sharpii

Abstract

<p><strong>Background: </strong>Due to habitat fragmentation many <em>Magnolia</em> species are at risk of extinction in Mexico.</p><p><strong>Question:</strong> What type of population structure is exhibited by <em>Magnolia</em> <em>perezfarrerae</em> and <em>M. sharpii,</em> endemic species of Chiapas, Mexico? Does the extreme reduction in the population of both <em>Magnolia </em>affect their reproductive capacity? What is the propagation potential in both species of <em>Magnolia</em>? Is it necessary to use pregerminative treatments for <em>Magnolia</em> species propagation?</p><p><strong>Studied species:</strong> <em>Magnolia perezfarrerae</em> A. Vázquez &amp; Gómez-Domínguez and <em>Magnolia sharpii </em>Miranda.</p><p><strong>Study sites and years of study: </strong>Highlands and Central Depression of Chiapas, Mexico, from 2015 to 2017.</p><p><strong>Methods:</strong> In this study, the density and distribution of diametric sizes of <em>M. perezfarrerae</em> and <em>M. sharpii</em> were assessed in natural populations. Their reproductive capacity and the <em>ex-situ</em> germination of both species was analyzed.</p><p><strong>Results:</strong> The population density in <em>M. perezfarrerae</em> was 40-53 ind. ha^-1, and 24-83 ind. ha^-1 in <em>M. sharpii</em>. 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 <em>M. sharpii</em> by 73 % and by 64 % for <em>M. perezfarrerae</em>.</p><strong>Conclusions:</strong>  The current condition of <em>Magnolia</em>species is critical and their persistence is compromised. Any viable conservation option would need to identify potential sites for the reintroduction of new populations.<p> </p>