General spatial spectral variation in rocky intertidal communities from three biogeographical regions

Aim: Understanding general spatial patterns of multiple species is a central aim of biogeography. Spatial analyses of coastal marine assemblages have shown an emergent pattern in that the variability in population abundances increases with increasing spatial scale of observation; i.e. a "red" spectrum of variation in population abundances. However, the generalization of these patterns to other ecological levels and across biogeographical regions remains unexplored. Here, we evaluate the consistency of a reddened relationship between the scale of observation and the variance in ecosystem properties in sessile intertidal rocky-shore assemblages across three biogeographical regions. Location: Replicate sites located in temperate (southern-central Chile), sub-Antarctic (Chilean South Patagonia) and Antarctic (West Antarctic Peninsula) regions. Methods: A total of 16,225 photo-quadrants were used to analyse local patterns of total community cover, bare substratum, total algal cover and total invertebrate cover. We used spectral analyses in which the spatial variance of each property was decomposed along a gradient of increasing distances between observations. Cross-semivariograms were used to analyse the spatial covariation of dominant taxa. Results: The analysed ecosystem properties showed a general reddened spectrum of variation that resembled patchy configurations of local communities. Additionally, cross-semivariance analyses indicated mainly negative relationships of covariation between the abundances dominant sessile species at each site, suggesting a general trend of spatial asynchrony between competing species. Main conclusions: To the best of our knowledge, this is the first study showing a general reddened pattern of spatial variation in relevant ecosystem-level properties across the Pacific shore of South America, southern Patagonia and West Antarctic Peninsula. These patterns reflect the result of multiple biotic and abiotic processes that interact across spatial scales. In particular, we suggest that processes that generate spatial asynchrony between competing species, such as compensatory dynamics, are relevant to maintain the spatial structure of rocky-shore communities.