Community structure and diversity of marine ascomycetes from coastal beaches of the southern Gulf of Mexico

• We studied diversity of ascomycetes from sandy beaches in the southern Gulf of Mexico.
• Low species diversity values agree with human impacted areas.
• High species diversity values correspond to beaches with diverse nearshore ecosystems.
• The CCA showed that temperature has a marked effect on the distribution of these fungi.
• We found a significant relationship between temperature and diversity of ascomycetes.

Diversity of marine fungi in the Gulf of Mexico remains unknown for the most part, therefore the geographical distribution patterns of these microorganisms are mostly unknown too. Twelve sandy beaches located in this sea were sampled to evaluate the diversity of marine fungi, revealed by fruiting on natural substrata incubated in the laboratory for up to 12 months. Species richness and diversity differed between beaches, and corresponded with the presence of main and highly polluted river mouths, nearshore marine environments, and core industrial and port developments. Contaminants and local anthropogenic activities may be reducing the diversity of marine ascomycetes. Connections between beaches and different nearshore habitats explain the high diversity observed, since they represent a varied source of substrata for decomposition and heterogeneous environmental conditions. We recognized four main local species distribution patterns. Moreover, the constrained correspondence analysis showed that temperature is a major environmental variable affecting the distribution of these fungi. By a linear regression we showed a significant relationship between temperature and diversity.