Ascidian distribution provides new insights to help define the biogeographic provinces in the South American Region

Abstract

The validity and size of the biogeographic Magellan Province of marine organisms have been the focus of discussion of many authors. The distribution of fish and other organisms has revealed a lack of homogeneity in the area, which has also been interpreted as comprising four different Provinces: Southern Chile (SCH), Tierra del Fuego (TDF), Southern Argentina (SAR), and the Malvinas/Falkland Islands (MAI). For the first time, we assess the ascidian fauna of this region to determine if the distribution of benthic sessile filter feeders corresponds to these biogeographic provinces. Ascidian species richness and percentages of endemism for these four areas were estimated using data from the literature and new sampling. Biogeographic affinities among SCH, TDF, SAR, and MAI were also calculated. The species Pyura pilosa, Molgula malvinensis, and Molgula manhattensis, the latter frequently considered as invasive, were found for the first time on the TDF shelf. The highest ascidian species richness was found in TDF (70 species), while the percentages of endemism greater than 10% (the minimum to qualify an area as a province) were found in TDF (15.7%) and SCH (11.1%). SAR and MAI showed the lowest percentages of endemism and the strongest affinity. Based on percentages of endemism, faunal affinities, and differences among the four provinces, we propose a separation of the South American Region into three Provinces: SCH, TDF, and SAR/MAI. Continued sampling of ascidians is considered to be particularly important, given the potential spread of invasive species throughout this region.

Ascidiacea (Chordata, Tunicata) from Uruguay (SW Atlantic): checklist and zoogeographic considerations

“…Ascidian diversity studies in this region have been mainly performed in the Patagonian shelf, South Argentina (e.g. Van Name 1945;Diehl 1977;Lagger & Tatián 2013;Taverna et al 2018), and Brazil (e.g. Rocha & Costa 2005;Bonnet & Rocha 2011;Moreno et al 2014).…”

Benthic communities in the Southwest Atlantic Ocean: Conservation value of animal forests at the Burdwood Bank slope

“…Nonetheless, the benthic communities found on the Burdwood Bank slope are similar to those described for northern sectors on the Argentinean slope (see Portela et al, , ; Schejter et al, ), which evidences a continuous habitat in which the Malvinas (Falkland) Current flows. Some important results obtained from the study of the samples taken during the Argentinean research cruises between 2013 and 2018 are the inventories of ascidians (Taverna et al, ), Asteroidea (Fraysse, Calcagno, & Pérez, ), brachiopods (Gordillo, Bayer, de Aranzamendi, Taverna, & Morán, ), molluscs (Di Luca & Zelaya, ), and polychaetes (Bremec et al, ), and the distribution and reproduction of some fishes have been also reported by García Alonso, Brown, Martín, Pájaro, and Capitanio (). Several new species have also been discovered in this area (Schejter, Bertolino, & Calcinai, ; Güller & Zelaya, ; Urcola & Zelaya, ; López Gappa, Liuzzi, & Zelaya, ), and many more are undergoing the description process.…”

Biodiversity of Isopoda and Cumacea (Peracarida, Crustacea) from the Marine Protected Area Namuncurá-Burdwood Bank, South-West Atlantic

“…In addition, exhaustive species inventories, descriptions of new species, new records of distribution, and studies on reproductive biology and biogeography have been recently published on the fauna from Burdwood Bank (Güller and Zelaya 2017; Penchaszadeh et al 2017Penchaszadeh et al , 2019Schejter et al 2017a;Fraysse et al 2018Fraysse et al , 2020García Alonso et al 2018;López Gappa et al 2018;Taverna et al 2018;Urcola and Zelaya 2018;Bremec et al 2019;Di Luca and Zelaya 2019;Gordillo et al 2019;Teso and Penchaszadeh 2019;Pérez-Barros et al 2020;Roccatagliata 2020;among others).…”