Diversity and temporal succession of early-colonizing fungi in wood baits from an estuarine environment, with description of Penicillium alavariense sp. nov.

Lignicolous marine fungi thrive in marine environments by colonizing wood, where they play a vital role in the degradation and recycling of complex molecules. However, lignicolous marine fungi remain under-described, with significant gaps in knowledge concerning their species diversity. To assess the diversity and temporal succession of lignicolous marine fungi, we submerged wood blocks of Pinus pinaster and Fagus sylvatica at the Ria de Aveiro estuary, Portugal and collected samples every two months, over six months. Twenty-nine fungal genera were identified from 251 isolates, with Penicillium being the most common genus after two months of block submersion. Wood type seems to have modulated fungal diversity, with several genera including Lulworthia spp. prefering beech wood, and Paralulworthia colonized pine. We showed that marine fungal genera from the family Lulworthiaceae are predominant and consistent colonizers of wood substrates in estuarine environments, occupying an intermediate role in colonization. In contrast, the genus Penicillium, the pioneer colonizer, decreases over time, likely due to competition with other marine genera. Based on multilocus phylogeny, using sequences of internal transcribed spacer region of the nuclear RNA gene cluster (ITS), and partial sequences of tubulin (tub2), calmodulin (cal) and RNA polymerase II (rpb2) coding genes' sequences, and morphological data, we propose Penicillium alavariense sp. nov., as a novel species in the series Simplicissima. These findings provide new insights into fungal succession on wood substrates, highlighting the role of wood type in shaping fungal communities and advancing our understanding of nutrient cycling in estuarine ecosystems.