Adlafia neoniana (naviculaceae), a new diatom species from forest streams in Puerto Rico

Background and aims – The samples on which this study is based were collected in two streams in Puerto Rico as part of a long-term monitoring program conducted by the National Ecological Observatory Network (NEON). Detailed study of the diatom assemblages revealed the occurrence of a new diatom species belonging to the genus Adlafia. Methods – The study considered 82 samples of epilithic diatoms from two streams in Puerto Rico (Rio Cupeyes and Rio Guilarte) subjected to different degrees of anthropogenic impacts. The new species description is based on high-quality Nomarski (DIC) LM micrographs which document the full spectrum of shape variability along the size diminution series (including girdle views), and SEM images documenting valve ultrastructure (including detailed internal views). In addition we provide information about ecological preferences with respect to trophic state / nutrients, habitat within the stream channel / microhabitat (riffle, run, pool), and season of maximum occurrence. Key results – The new species is described as Adlafia neoniana Cantonati sp. nov. It resembles A. drouetiana but has lanceolate (instead of triundulate) outline, slightly-subcapitate to subrostrate ends (instead of subcapitate to capitate), and higher stria density. It is also similar to A. muscora but differs by ellipticlanceolate (instead of linear-lanceolate) outline, broader valves, and higher stria density. Moreover, the new species was most abundant in an undisturbed, oligotrophic, shaded forest stream whilst A. drouetiana is known from Brazil to be tolerant to organic pollution and eutrophication. Conclusions – Adlafia neoniana can be differentiated from other similar species in the light microscope by recognizable characters or character combinations. Its discovery and characterization is a contribution to the knowledge of the still understudied biodiversity of microorganisms in tropical streams.