Arbuscular mycorrhizal association in Conocarpus erectus (Combretaceae) in mangroves from Yucatán, México

Abstract

Background: Soil flooding and salinity can be limiting for arbuscular mycorrhizal fungi (AMF), yet they are found in mangrove ecosystems. Arbuscular mycorrhizal association could influence the functioning of mangrove ecosystems, but little is known about its roll and balance in these dynamic systems. Question: What is the status of the arbuscular mycorrhizal association in C. erectus under natural conditions? Species study: Conocarpus erectus is a tree or shrub species that establishes in mangrove ecosystems and is tolerant to elevated levels of salinity and flooding. Study site and dates: Three zones representing a range of conditions of salinity were selected in the Ría Lagartos Biosphere Reserve in Mexico, as well as two contrasting collecting seasons in 2009 and 2010: northwind season and drought season.  Methods: Roots were sampled from C. erectus plants in each zone to evaluate the percentage of arbuscular mycorrhizal colonization and rhizospheric soil samples were taken to evaluate AMF spore density and species richness.  Results: The highest percentage of root colonization was recorded in the site of highest salinity during the northwind season, with this value decreasing in the drought season. The same seasonal pattern was observed in spore density. The highest richness was recorded in the site of lowest salinity in both seasons. A total of 16 AMF species were identified.  Conclusions: The results suggest that seasonality, in its relation with soil salinity and soil water availability, can influence the development and symbiotic association of the AMF in mangrove associated communities dominated by C. erectus.