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

Abstract

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

Taxonomic identity of Distaplia stylifera (Tunicata, Ascidiacea), a new arrival to the eastern Pacific displaying invasive behavior in the Gulf of California, Mexico

“…COI data for the single well-represented species of Distaplia in these databases, D. bermudensis Van Name, 1902, revealed divergences ~ 14-20% for different morphotypes and distribution areas. This indicates either high intraspecific variability or the existence of multiple species under D. bermudensis binomen, as suggested by some authors (Evans et al 2021;Virgili et al 2022). The high variability found in the congener D. bermudensis suggests that shedding light on the relationships of D. stylifera will require extensive sampling of the main areas where the species has been recorded to settle whether it is a single polymorphic biological species with circumtropical biogeographic distribution or a group of related species with distinct (perhaps overlapping) biogeographic distribution patterns.…”

Chemical and Pharmacological Prospection of the Ascidian Cystodytes dellechiajei

“…The samples were deposited in the collection of the Laboratory of Benthos (SZN_B_2518ASC32F, SZN_B_2519ASC32G). To assess the genetic lineage of the Ischia population, the total genomic DNA was extracted from the zooids using the DNeasy Blood and Tissue kit (QIAGEN, Valencia, CA, USA), as described in [43]. A partial region of the cytochrome c oxidase subunit I (COI) mitochondrial gene was amplified via PCR using the primers and conditions described in [43].…”

Effects of color variation and physiological state on ascidian microbiomes

“…The colonial ascidian Polyclinum constellatum (Savigny 1816) was first described from the Bermudas and is commonly observed in the Caribbean Sea (Aydin‐Onen, 2018 ; Lambert, 2019 ; Rocha & Costa, 2005 ; Rocha et al, 2010 ; Streit et al, 2021 ). P. constellatum has also been observed in the Pacific, West Indian, and Atlantic oceans (from Canada to Brazil), South Africa, and the Mediterranean Sea (reviewed in Aydin‐Onen, 2018 , Virgili et al, 2022 ) and appears to be spreading rapidly, likely through anthropogenic vectors. Although a few barcode sequences of the cytochrome oxidase I gene (COI) are now available in GenBank (Montesanto et al, 2022 ; Streit et al, 2021 , Virgili et al, 2022 ), the species has been widely misidentified in the past (Montesanto et al, 2022 ), presumably due to multiple color morphs occurring in sympatry (Lambert, 2019 ; Montesanto et al, 2022 ; Rocha et al, 2010 ; Streit et al, 2021 , Virgili et al, 2022 ).…”

“…Although a few barcode sequences of the cytochrome oxidase I gene (COI) are now available in GenBank (Montesanto et al, 2022;Streit et al, 2021, Virgili et al, 2022, the species has been widely misidentified in the past (Montesanto et al, 2022), presumably due to multiple color morphs occurring in sympatry (Lambert, 2019;Montesanto et al, 2022;Rocha et al, 2010;Streit et al, 2021, Virgili et al, 2022.…”

“…The colonial ascidian Polyclinum constellatum (Savigny 1816) was first described from the Bermudas and is commonly observed in the Caribbean Sea (Aydin-Onen, 2018;Lambert, 2019;Rocha & Costa, 2005;Rocha et al, 2010;Streit et al, 2021). P. constellatum has also been observed in the Pacific, West Indian, and Atlantic oceans (from Canada to Brazil), South Africa, and the Mediterranean Sea (reviewed in Aydin-Onen, 2018, Virgili et al, 2022 and appears to be spreading rapidly, likely through anthropogenic vectors.…”