Abstract
Aquatic macroinvertebrates play a crucial role in freshwater ecosystems, but their diversity remains poorly known, particularly in the tropics. This “taxonomic void” limits our understanding of biodiversity patterns and processes in freshwater ecosystems, and the scale at which they operate. We used DNA barcoding to estimate lineage diversity (and the diversity of unique haplotypes) in 224 specimens of freshwater macroinvertebrates at a small spatial scale within the Panama Canal Watershed (PCW). In addition, we compiled available barcoding data to assess macroinvertebrate diversity at a broader spatial scale spanning the Isthmus of Panama. Consistently across two species delimitation algorithms (i.e., ABGD and GMYC), we found high lineage diversity within the PCW, with ~ 100–106 molecular operational taxonomic units (MOTUs) across 168 unique haplotypes. We also found a high lineage diversity along the Isthmus of Panama, but this diversity peaked within the PCW. However, our rarefaction/extrapolation approach showed that this diversity remains under-sampled. As expected, these results indicate that the diversity of Neotropical freshwater macroinvertebrates is higher than previously thought, with the possibility of high endemicity even at narrow spatial scales. Consistent with previous work on aquatic insects and other freshwater taxa in this region, geographic isolation is likely a main factor shaping these patterns of diversity. However, other factors such as habitat variability and perhaps local adaptation might be reshaping these patterns of diversity at a local scale. Although further research is needed to better understand the processes driving diversification in freshwater macroinvertebrates, we suggest that Neotropical streams hold a high proportion of hidden biodiversity. Understanding this diversity is crucial in the face of increasing human disturbance.
Highlights
Aquatic macroinvertebrates are a fundamental component of freshwater environments
We collected approximately 300 specimens across the four sites; our analysis focused on the 224 individuals that were successfully barcoded (Table 1 and S1 Table)
In Frijolito, the site sampled by the two studies, we found a total of 46 haplotypes, 45 of which were unique to our study
Summary
Aquatic macroinvertebrates are a fundamental component of freshwater environments. They mediate important processes such as food web dynamics, energy flow, and nutrient cycling, and play a central role in sustaining the biodiversity and functioning of freshwater ecosystems [1,2,3]. This is partially due to the complexity of these communities, which are often composed of multiple life-stages existing at the interface between the terrestrial and aquatic environment [15,16]. Another limitation is the low efficiency of traditional morphological methods, which are generally time-consuming, and highly variable in the quality of identification across taxa and experts
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