The geographic variation in precipitation, temperature and soil salinity has shown to determine turnover in dominant salt marsh halophytic plants along the Chilean coast. In general, marshes at lower latitudes are dominated by Sarcocornia fructicosa, whereas marshes at higher latitudes by Spartina densiflora.
Vegetation is of primary importance in structuring faunal communities. As a consequence, variation of vegetation species composition and their arquitecture [e.g., low vegetation (Sarcocornia) vs. high vegetation (Spartina)] may have important consequences on the associated biota, as the habitat complexity can affect their ecological interactions and community dynamics.
The purpose of this study was to examine the latitudinal patterns of salt marsh arthropod communities along the Chilean cost and to explore whether local factors influence community patterns at larger scale. We sampled a total of 9 salt marshes across five bioclimatic zones of the Chilean coast. These correspond to the hyperarid, arid, semiarid, humid and hyperhumid zones from north to south, respectively. Arthropods were collected during spring and autumn 2016 using pit fall traps deployed for 72 hours within the high marsh zone. During each visit, we quantified vegetation height and biomass. We also collected soil samples for laboratory analyses of water content salinity and organic matter.
Salt marshes differed in their arthropod community composition across bioclimatic zones (PERMANOVA; “ADONIS”; R2 = 0.33, P = 0.001) and between vegetation types (ADONIS; R2 = 0.08, P = 0.01). SIMPER analysis showed that saltmarshes dominated by Sarcocornia in arid zone were more similar to saltmarshes dominated by Spartina in semiarid zone (45% of dissimilarity) than to saltmarshes dominated by Spartinain hyperumid zone (89%).
SIMPER revealed that Talitridae (Crustacea, Amphipoda) and Philoscidae(Crustacea, Isopoda) were the taxa that contributed most to differences between bioclimatic zones and vegetation types.
There were significant differences in soil and vegetation characteristics between Spartina and Sarcocornia (ADONIS; R2 = 0.45, P = 0.02). The greater wet biomass of Sarcocornia was prominent in explaining the cumulative dissimilarity (ca. 45%) existing between vegetation types (SIMPER analysis). However, other variables, such as soil salinity and precipitation and their effects on arthropod assemblages should be disentangled with further analyses.