Aim We evaluated whether patterns of species diversity (α, β and γ) of rocky shore assemblages followed latitudinal gradients (i.e. LDGs) along the South American coasts, and tested hypotheses related to potential processes sustaining or disrupting the expected LDG pattern at various spatial scales. Location Coasts of South America. Taxon Macroalgae and sessile/slow‐moving macrofauna on intertidal rocky shores. Methods We evaluated changes in species composition across 143 sites. The degree of replacement and loss of species at different spatial scales (i.e. coasts, regions and sites) were estimated to help distinguish among ecological, historical and evolutionary hypotheses for explaining LDGs. Furthermore, components of diversity and taxonomic distinctness were measured, and variability in these measures was decomposed using analysis of covariance. Finally, we examined relationships between diversity and a suite of environmental and anthropogenic variables to identify potential mechanisms that may be responsible for the reported spatial relationships. Results Species composition varied with latitude, and this variability was relatively consistent on both coasts. At all spatial scales, replacement of species was the dominant phenomenon (>95%), rather than loss in the total number of species (<5%). LDGs were strongly dependent on the diversity component and the spatial scale: generally, positive for regional β‐diversity, negative for α‐diversity and site β‐diversity. Sea surface temperature (SST) was the variable that best explained patterns of diversity along both coasts (14%–22%), but other regional and local environmental variables associated with river discharges, upwelling, confluence of currents, tides and anthropogenic pressures also accounted for an important portion of variation (5%–14% each). Main conclusions Species diversity of South American rocky shores followed, with interruptions, LDGs. The trend of those LDGs, however, depended on the scale and metric used to describe diversity. It is proposed that patterns of LDGs at various scales are not the result of a single overarching process but are strongly influenced by local and regional processes. Although the most evident environmental gradient was the decrease in SST towards the south, it was demonstrated that regional and local environmental variables were also important for understanding the increase in regional β‐diversity towards the tropics.

Two decapod species are reported for the first time in the Colombian Pacific: Trachycaris restricta A. Milne-Edwards, 1878 and Microprosthema emmiltum Goy, 1987 (both collected at 25 m depth). A third species, Glyptoxanthus labyrinthicus Stimpson, 1860 (collected at 5 m depth), previously reported for the continental Pacific coast of Colombia, represents a new record for the oceanic Island of Malpelo. These species were collected using hard artificial substrates deployed for three months. This sampling method is novel to Malpelo, where previous samplings using scuba diving were unable to report/collect these species. These findings then, highlight the usefulness of the sampling technique that besides being non-destructive, allows the collection of small sized cryptic fauna in marine habitats. Several factors can contribute to the unsuccessful record of biodiversity. In this case, the small sizes and cryptic behavior of these species, coupled with the scarcity of investigations aiming to know the sub-tidal rocky ecosystems invertebrate biodiversity in the area, could help to explain these new records.

The present study deals two new alpheid shrimp species from the transisthmian Salmoneus ortmanni (Rankin, 1898) complex. Salmoneus alvarezi sp. nov. is described based on materials collected in Bahía Málaga, Colombia, and Punta Morales, Costa Rica, and is closely related to the western Atlantic S. ortmanni and S. wehrtmanni Anker, 2011. Salmoneus malagensis sp. nov. is described based on specimens from Bahía Málaga, Colombia, and beyond any doubts represents the eastern Pacific sister species of the western Atlantic S. carvachoi Anker, 2007. The two new species can be easily distinguished from each other by a number of morphological characters and colouration, and in addition appear to be ecologically separated. All previous records of S. ortmanni from the eastern Pacific are reassigned, some tentatively, to S. alvarezi sp. nov. based on description, illustrations or ecological data.

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A new infaunal species of the rare alpheid genus Harperalpheus Felder & Anker, 2007 is described from Bahía Málaga,  Pacific coast of Colombia, based on single, incomplete holotype specimen. Harperalpheus leptodactylus sp. nov. may be easily separated from the western Atlantic type species and only other species of the genus, H. pequegnatae Felder & Anker, 2007, by several morphological characters on the first and fifth pereiopod, as well as on the antennular peduncle.