Biodiversity and distribution of the Scolecida (Annelida: Polychaeta) on the continental shelf of the Gulf of California, Mexican Pacific

The latitudinal and bathymetric distribution of the Scolecida (Polychaeta) clade species from the continental shelf of the Gulf of California are herein analysed. Eight families and 109 species were collected and identified in 53 localities from its northern, central and southern regions. The most diverse families were Capitellidae (32 species, 17 genera) and Orbiniidae (24 species, 4 genera). The localities with the highest biodiversity (> 12 species) are scattered along the Gulf. The classical north-south increasing biodiversity gradient was not observed since the number of species is similar in all three regions of the Gulf (78 to 83 species/region). Bathymetrically, a parabolic trend emerged, biased towards shallow depths. The highest number of species was found at 40 m depth (52 species), the lowest on the outer shelf, with a strong reduction in diversity from 140 m down (<5 species). The updated and comprehensive list of species presented here includes the results of our research in the area complemented by all the literature records with their known distribution. This in particular constitutes an important tool for future taxonomical surveys, as well as ecological or biogeographical studies.