Amazon floodplain fish diversity at different scales: do time and place really matter?

Amazonian floodplain lakes, which are of different types based on their proximity to the main river channels, are subjected to a strong seasonal hydrologic cycle and have different habitat types within them. We hypothesized that these two spatial scales (lake type, and habitat type within lakes), and the temporal scale associated with hydrological seasons help explain the high fish diversity of the Amazon basin. We sampled three lake types categorized by proximity and connectivity with the Solimões River (island, coastal, and mainland) in 2011 during both high and low water seasons. Within these lakes, we sampled three habitat types (open water, flooded forest, and macrophyte banks). Although comparisons of diversity indices revealed few differences with respect to overall species numbers, actual species composition, which is not included in calculation of diversity indices, differed markedly at all three scales. Although many species (86) were common to all three types of lakes, each type also had many unique species (11–20), as did within-lake habitat type (10–15) and hydrologic season (26 each). Thus, these temporal and spatial scales are important to the detection and understanding of fish species diversity in this region, and will be important to keep in mind when designing preserves.