Intertidal mussel beds from the South- western Atlantic show simple structure and uniform appearance: does environmental harshness explain the community?

ORENSANZ JOSÉ MARÍA (LOBO); TABLADO ALEJANDRO; ORENSANZ JOSÉ MARÍA (LOBO); TABLADO ALEJANDRO; CALCAGNO JAVIER; ADAMI MARIANA L.; CALCAGNO JAVIER; ADAMI MARIANA L.; LABRAGA JUAN CARLOS; SCHWINDT EVANGELINA; LABRAGA JUAN CARLOS; SCHWINDT EVANGELINA

MARINE BIOLOGY RESEARCH

TAYLOR & FRANCIS AS

Lugar: Londres; Año: 2017 p. 1 - 17

1745-1000

Communities of the rocky mid-intertidal zone of the South-western Atlantic are uniform inappearance, dominated by dense monocultures of small-size mussels (Brachidontesrodriguezii and Perumytilus purpuratus). To explain this, two hypotheses have been advanced in the literature: environmental harshness due to high potential evaporation and historical contingency after the Last Glacial Maximum. In this study of Uruguayan and Argentine shores, we address the implications and predictions of these two hypotheses from a biogeographic perspective by studying the regional distribution and composition of midintertidal mussels. We conducted an extensive latitudinal sampling survey (21 locations, 34°-54°S), along with a compilation of available information on mussel bed composition and mussel predators present along the coastline. Then we constructed latitudinal profiles ofecologically significant environmental variables with specific emphasis on potentialevaporation, a proxy for desiccation stress. The results show that mussel beds are composedof two species of small mussels, which coexist over a biogeographic transition zone (40°- 42°S) related to sea surface water temperature. The distribution of mussels along the coastline studied is not consistent with the environmental harshness hypothesis. In addition, in the Central Patagonian zone (44?50°S), two invertebrate predators also inhabit the intertidal rocky shores. However, these localities showed higher environmental harshness (potential evaporation rate) than non-Patagonian localities. We suggest that further attention should be given to historical contingency in order to advance towards a hypothesis consistent with current knowledge on the post-glacial biogeographic history of the South-western Atlantic.