Tropical Diatoms of Costa Rica
Biodiversity

Biodiversity

The Neotropics are known as a biodiversity "hot spot" with high levels of endemism. Efforts are underway to inventory organismal diversity in countries such as Costa Rica (INBio). Naturally, higher organisms such as mammals and reptiles are better understood compared to less-known organisms like arthropods (ALAS), fungi, and algae. In general, algae in tropical regions are poorly studied (Mann and Droop 1996) and this may be especially true for stream algae that are light-limited in shaded streams but may play a large role in light gaps of streams. Our work in lowland, Costa Rican streams has, in part, focused on biogeographic patterns of periphyton. Neotropical diatoms have been poorly studied and have been identified using cosmopolitan, primarily temperate species names. Our work suggests that, contrary to the cosmopolitan paradigm, many diatom taxa in these streams are endemic to the tropics and possibly even to Costa Rican lowlands. We are currently estimating that 20% of the diatoms found at in the streams at La Selva re new to science. For example, in high-solute streams, we are currently describing a new freshwater diatom species in the genus Seminavis, which previously only contained marine representatives; additional investigation has shown that this taxon has a wider Neotropical distribution, including the Caribbean. We have also observed an unusually high diversity within the genus Surirella. This high level of diversity in this genus is typically associated collections from ancient lake systems (i.e., Lake Baikal, Siberia) where organisms have speciated over a long time period.