The Miseno Lake (Central-Western Mediterranean Sea): An Overlooked Reservoir of Non-Indigenous and Cryptogenic Ascidians in a Marine Reserve

Ascidians are the largest and most diverse class of subphylum Tunicata, important components marine benthic communities. They also renowned worldwide invaders, growing concern due to ease spread impacts on native biota. We hereby combined bathymetric habitat mapping, extensive transect photo-quadrat sampling, a morphological molecular study selected specimens evaluate taxonomic composition, cover, distribution pattern ascidians in reserve central-western Mediterranean Sea, Miseno Lake (Bacoli, Naples, Italy). Twenty-four taxa were found, which 9 non-indigenous species (NIS), 5 cryptogenic, 10 native, delineating as major hotspot NIS cryptogenic ascidians. DNA barcoding yielded 114 sequences, confirming identification for 22 but revealing single few mismatches per species. Taxonomic insights offered text Supplementary Material several taxa, including understudied Ascidia colleta malaca . The presence new clade was discovered Distaplia bermudensis complex. Didemnum pseudovexillum Polyclinum constellatum respectively first recorded Italy western Mediterranean, same holds true other whose accurate only possible through evidence. analysis photographic archives allowed backdating georeferencing records Aplidium accarense Botrylloides niger P. Mediterranean. Generalized Additive Models revealed that abundance increased with availability hard substrates (rocks or litter), decreased depth, highest channels connecting water bodies, followed by peripheral areas lake. No certain evidence competitive restriction found. Finally, introduction pathways, potential impacts, additional discussed NIS. present provides baseline shifts ascidian communities future, suggests constant monitoring programs constitute crucial steps achieve solid management, confirms reserves widely vulnerable biological invasions, especially when they coincide hotspots arrival spreading such semi-enclosed basins.