Early naturalists suggested that predation intensity increases toward the tropics, affecting fundamental ecological and evolutionary processes by latitude, but empirical support is still limited. Several studies have measured consumption rates across latitude at large scales, with variable results. Moreover, how predation affects prey community composition at such geographic scales remains unknown. Using standardized experiments that spanned 115° of latitude, at 36 nearshore sites along both coasts of the Americas, we found that marine predators have both higher consumption rates and consistently stronger impacts on biomass and species composition of marine invertebrate communities in warmer tropical waters, likely owing to fish predators. Our results provide robust support for a temperature-dependent gradient in interaction strength and have potential implications for how marine ecosystems will respond to ocean warming.

Autonomous reef monitoring structures (ARMS) have been proposed as a standardized, passive, nondestructive sampling tool. This study assessed the ability of ARMS to capture the cryptic species diversity of two coral reefs by recording species richness and taxonomic representativeness using conventional taxonomy. The capacity of ARMS, as artificial substrates, to favor the establishment of nonindigenous species over native species was also evaluated. The use of ARMS allowed the detection of 370 species morphotypes from nine phyla, yielding 13 new records of geographic distribution expansion, one exotic species for the Gulf of México and the Caribbean Sea, and six newly described species. It was also possible to make spatial comparisons of species richness between both reefs. ARMS captured cryptic diversity exceptionally well, with the exception of echinoderms. Furthermore, these artificial structures did not hinder the colonization ability of native species; in fact, the colonization patterns on the structures themselves represented the spatial differences in the structure of benthic assemblages. This study represents the first effort to make a conventional taxonomic description of the cryptic fauna of the Yucatan Peninsula using ARMS. It is recommended to assess coral reef species diversity, but more taxonomists specialized in marine invertebrates are needed.

Compound styelid ascidians are distributed in all marine environments and usually exhibit high morphological plasticity and complexity. In particular, Botrylloides, Botryllus, and Symplegma species show high morphological variations leading to confusion in traditional taxonomy assignments and to ambiguity in species delineation. Fewer than 20 species in these genera are registered in the Atlantic region. Here we surveyed the coral reefs of the southern Gulf of Mexico and Mexican Caribbean Sea, barcoded a total of 110 samples collected in seven reefs in 24 sites using mitochondrial cytochrome c oxidase subunit I (or 1), as well as performed a detailed morphological study. Species delimitation analyses of barcoding sequencing revealed twelve botryllid species and three Symplegma species. Two of the botryllid species were identified as Botrylloides niger and Botryllus humilis; the latter is the first record for the Gulf of México. The remaining 10 botryllid species and the two Symplegma species are not currently described in the literature and have no close matches in GenBank. One of the Symplegma samples could not be identified as an existing species and current characters do not support the description of a new species. Here we describe twelve new species, seven in Botryllus: B. bonanzus sp. nov, B. camur sp. nov., B. hartensis sp. nov., B. lambertorum sp. nov., B. nortensis sp. nov., B. tunnelli sp. nov., and B. unamensis sp. nov., three in Botrylloides: B. alacranensis sp. nov., B. ampullarius sp. nov., B. catalitinae sp. nov., and two in Symplegma: S. papillata sp. nov., and S. sisalensis sp. nov. We also present a tabular identification key of Botryllus, Botrylloides and Symplegma Atlantic species.

This study is the first inventory of ascidians from shallow waters (0–25 m) of coastal and reef habitats in the southern Gulf of Mexico where ascidian diversity is poorly known. Sampled environments in 14 locations (38 sites) with 134 samples collected from 2015 to 2017 included coral reefs, coastal lagoons, mangroves, seagrass, ports, and artificial platforms. The 31 identified species comprise 19 genera and 13 families. Ten species are newly reported in the Gulf of Mexico:AscidiapanamensisBonnet & Rocha, 2011;Ecteinascidiastyeloides(Traustedt, 1882);CystodytesroseolusHartmeyer, 1912; Eudistomaaff.amanitum Paiva & Rocha, 2018;EudistomarecifenseMillar, 1977;EuherdmaniafasciculataMonniot, 1983; Euherdmaniaaff.vitrea Millar, 1961;Polycarpacartilaginea(Sluiter, 1885);Botrylloidesmagnicoecum(Hartmeyer, 1912) andDidemnumgranulatumTokioka, 1954. Two new species will be described separately (Clavelinasp. andPyurasp.). This study provides the first records for 26 species ascidians for the region as well as describes increased distributions of ten Atlantic species. Thus, our data provide a starting point for future ecological, experimental and taxonomic studies of ascidians of the Gulf of Mexico.

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