Small-scale spatiotemporal variability and distance–decay relationships in intertidal micro- and meiobenthic assemblagesстатья
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Аннотация:Compositional similarity generally decreases with increasing geographic distance betweensites (distance decay of similarity, DDS). Two non-exclusivemechanisms havebeen proposed to explain this pattern: increasing differences in environmental conditionsand pure spatial effects of dispersal limitation. On regional and global scales, environmentalselection is considered the major factor for microbial assemblages, whereaspure spatial effects are generally more profound for larger organisms with limited dispersalability. We investigated the DDS relationships at a small spatial scale (decimeters-tensof meters) for three groups of benthic organisms differing in body size: diatomsand flagellates (DF), ciliates (CL), and harpacticoids (HA). All groups demonstrated definiteDDS relationships. The pure spatial effects were strongest for the smallest-sizeprotists (DF), relatively weaker for CL and negligible for HA. In contrast, environmentalfactors (i.e., the differences in sediment properties) were more important for the HAand CL assemblages than for DF assemblages. In addition, we revealed a considerabletemporal component of DDS relationships. First, similarity decreased with the time intervalbetween sampling events (“temporal DDS”). Second, the average spatial similarityitself increased with time. These effects were significant for DF and CL only butwere weak or undetectable for HA. Thus, our results are opposite to those commonlyobserved at larger (regional or global) scales. We suppose that the DDS relationshipsobtained at different spatial scales, despite formal similarity, reflect different phenomenadriven by different mechanisms. At the geographical scale, species distribution patternsare mainly driven by long-distancedispersal processes operated at the populationlevel and dependent on their size-relatedtraits, which, taken in common, offer the advantageof small-sizedgroups. The local-scaledistribution is primarily determined byindividual motility and within-habitatenvironmental heterogeneity. Small protists arerelatively less motile, finely perceived and, therefore, have higher rates of spatial decay.