Abstract
Lignicolous marine ascomycetes can be divided into two major taxonomic groups: the Halosphaeriales in oceanic and coastal waters, both intertidal and submerged, and the Dothideomycetes that occur primarily in mangroves. While some genera of marine Dothideomycetes are well circumscribed (e.g., Leptosphaeria, Phaeosphaeria), others cannot be assigned, based on their morphology, to an appropriate order with certainty (e.g., Aigialus, Paraliomyces). Recently, a number of studies on the molecular phylogeny of the Halosphaeriales have been undertaken, while limited systematic investigation on marine Dothideomycetes is available. In the current study, small subunit ribosomal DNA of Aigialus grandis, A. parvus, Helicascus nypae, Julella avicenniae and Paraliomyces lentiferus was sequenced and subjected to phylogenetic analysis to determine their ordinal affinity. These taxa grouped consistently within the Pleosporales with good statistical support. Relationships of these species with other taxa in the Pleosporales remain unresolved. The monophyly of Aigialus species and Helicascus species implies that they represent good genera in the order, with significant morphological delimitation from other genera.