Lake regionalization and diatom metacommunity structuring in tropical South America

Lakes and their topological distribution across Earth’s surface impose ecological and evolutionary constraints on aquatic metacommunities. In this study, we group similar lake ecosystems as metacommunity units influencing diatom community structure. We assembled a database of 195 lakes from the tropical Andes and adjacent lowlands (8°N–30°S and 58–79°W) with associated environmental predictors to examine diatom metacommunity patterns at two different levels: taxon and functional (deconstructed species matrix by ecological guilds). We also derived spatial variables that inherently assessed the relative role of dispersal. Using complementary multivariate statistical techniques (principal component analysis, cluster analysis, nonmetric multidimensional scaling, Procrustes, variance partitioning), we examined diatom–environment relationships among different lake habitats (sediment surface, periphyton, and plankton) and partitioned community variation to evaluate the influence of niche-and dispersal-based assembly processes in diatom metacommunity structure across lake clusters. The results showed a significant association between geographic clusters of lakes based on gradients of climate and landscape configuration and diatom assemblages. Six lake clusters distributed along a latitudinal gradient were identified as functional metacommunity units for diatom communities. Variance partitioning revealed that dispersal mechanisms were a major contributor to diatom metacommunity structure, but in a highly context-dependent fashion across lake clusters. In the Andean Altiplano and adjacent lowlands of Bolivia, diatom metacommunities are niche assembled but constrained by either dispersal limitation or mass effects, resulting from area, environmental heterogeneity, and ecological guild relationships. Topographic heterogeneity played an important role in structuring planktic diatom metacommunities. We emphasize the value of a guild-based metacommunity model linked to dispersal for elucidating mechanisms underlying latitudinal gradients in distribution. Our findings reveal the importance of shifts in ecological drivers across climatic and physiographically distinct lake clusters, providing a basis for comparison of broad-scale community gradients in lake-rich regions elsewhere. This may help guide future research to explore evolutionary constraints on the rich Neotropical benthic diatom species pool

Lake Regionalization and Diatom Metacommunity Structuring in Tropical South America

Lakes and their topological distribution across Earth\u27s surface impose ecological and evolutionary constraints on aquatic metacommunities. In this study, we group similar lake ecosystems as metacommunity units influencing diatom community structure. We assembled a database of 195 lakes from the tropical Andes and adjacent lowlands (8°N–30°S and 58–79°W) with associated environmental predictors to examine diatom metacommunity patterns at two different levels: taxon and functional (deconstructed species matrix by ecological guilds). We also derived spatial variables that inherently assessed the relative role of dispersal. Using complementary multivariate statistical techniques (principal component analysis, cluster analysis, nonmetric multidimensional scaling, Procrustes, variance partitioning), we examined diatom–environment relationships among different lake habitats (sediment surface, periphyton, and plankton) and partitioned community variation to evaluate the influence of niche‐ and dispersal‐based assembly processes in diatom metacommunity structure across lake clusters. The results showed a significant association between geographic clusters of lakes based on gradients of climate and landscape configuration and diatom assemblages. Six lake clusters distributed along a latitudinal gradient were identified as functional metacommunity units for diatom communities. Variance partitioning revealed that dispersal mechanisms were a major contributor to diatom metacommunity structure, but in a highly context‐dependent fashion across lake clusters. In the Andean Altiplano and adjacent lowlands of Bolivia, diatom metacommunities are niche assembled but constrained by either dispersal limitation or mass effects, resulting from area, environmental heterogeneity, and ecological guild relationships. Topographic heterogeneity played an important role in structuring planktic diatom metacommunities. We emphasize the value of a guild‐based metacommunity model linked to dispersal for elucidating mechanisms underlying latitudinal gradients in distribution. Our findings reveal the importance of shifts in ecological drivers across climatic and physiographically distinct lake clusters, providing a basis for comparison of broad‐scale community gradients in lake‐rich regions elsewhere. This may help guide future research to explore evolutionary constraints on the rich Neotropical benthic diatom species pool

Occurrence of Keratella cochlearis (Gosse, 1851) (Rotifera, Monogononta) on San Cristóbal Island, Galápagos Archipelago, Ecuador

The presence of the rotifer Keratella cochlearis (Gosse, 1851) is reported in El Junco Lake, a freshwater crater lake in San Cristóbal Island, Galápagos Islands. This taxon is a known species aggregate containing both eurytopic cosmopolitans as well as local and regional endemics, but also some insufficiently documented cryptic species. This record is the first of a representative of the aggregate for the rotifer fauna of the Galápagos Islands. Considering that the animal is now being recorded from the lake while earlier surveys did not, and the high dispersal capacity of many rotifers, we hypothesize that the organism recorded is one of the more widespread members of the aggregate, which colonized El Junco Lake only recently

The fossil diatoms of lake Yambo, Ecuador. A possible records of El Niño events

Abstract Fossil diatoms from a sediment core of Lake Yambo, a lake in an endorheic, desert region of the Ecuadorian Andes, provide a record of precipitation events that can be linked to the ENSO phenomenon. Abnormally high precipitation in the region during the 1982-83 El Niño caused a substantial drop in the lake's conductivity. The diatom flora in the lake changed from a community dominated by the halophilic species Cratícula halophila Cratícula halophila to one dominated by a freshwater species Aulacoseira distans Aulacoseira distans. Similar shifts in dominance can be seen at various points throughout the core. There also appears to be an increase in sediment deposition at these points. This paper provides the first evidence that the use of fossil diatoms from lake cores can be a valuable tool in reconstructing histories of El Niño events.Les diatomées fossiles du lac "Yambo", Équateur. Un registre sur les phénomèmes "El Niño" Résumé Des études limnologiques effectuées tous les ans depuis 1975 sur le lac "Yambo", situé dans une zone aride de la région inter-andine équatorienne, ont montré que l'eau du lac est à haute teneur en sels dissouts et que la flore de diatomées est riche en Cratícula halophila une espèce caractéristique des lacs saumâtres. En 1982-1983, l'un des phénomènes "El Niño" des plus inattendus, des plus intenses et des plus catastrophiques a frappé la côte sud-américaine du Pacifique provoquant une augmentation considérable de la précipitation sur la région du lac. Par suite de cette augmentation, la conductivité de l'eau a diminué de 30%. La communauté de diatommees a réagi à ce changement dans la chimique de l'eau et nous avons constaté une augmentation du nombre des diatomées Aulacoseira italica ainsi qu'une diminution des Cratícula halophila. Des analyses sur des diatomées fossiles en provenance des sédiments du lac "Yambo" montrent les mêmes fluctuations des deux espèces. Etant donné la localisation du lac, sur une zone très aride, les changements dans la salinité de l’eau ne peuvent être que le résultat des changements dramatiques survenus dans les précipitations. Par conséquent, il est possible d'interpréter le registre des changements survenus dans la communauté de diatomées du lac "Yambo" comme l'histoire des phénomènes "El Niño" au cours des 2500 ans de vie du lac.Diatomeas fósiles de la laguna de Yambo, Ecuador. Un posible récord de fenónemo El Niño Resumen Estudios limnológicos se han realizado cada año desde 1975 en la laguna de Yambo, ubicada en una parte árida de la región interandina de Ecuador. Estos estudios indican que el agua de esta laguna tiene una alta concentración de sales disueltas y la flora de diatomeas rica en Cratícula halophila, una especie característica de lagunas salobres. En 1982-1983 uno de los fenómenos «El Niño» más inesperados, intensos y catastróficos, azotó la costa sudamericana del Pacífico y causó un aumento considerable de la precipitación en la región de la laguna. Este aumento hizo que la condutividad del agua sea reducida en un 30%. La comunidad de diatomeas respondió a este cambio en la química del agua, y observamos un aumento en la abundancia de la diatomea Aulacoseira itálica, y una reducción en la abundancia de Cratícula halophila. Análisis de diatomeas fósiles en sedimentos de la laguna de Yambo revelan las mismas fluctuaciones en estas dos especies. Como la laguna se encuentra en una región muy árida, cambios en la salinidad del agua pueden resultar solamente como consecuencia de cambios dramáticos en la precipitación. Por lo tanto es factible interpretar el récord de cambios en la comunidad de diatomeas de la Laguna de Yambo como la historia de los fenómenos de «El Niño» ocurridos durante los 2500 años de existencia de la laguna.Steinitz-Kannan Miriam, Nienaber Mark A., Riedinger Melanie A., Kannan Ramamurthi. The fossil diatoms of lake Yambo, Ecuador. A possible records of El Niño events. In: Bulletin de l'Institut Français d'Études Andines, tome 22, N°1, 1993. Enregistrements du phénomène El Niño et d’événements ENSO en Amérique du Sud. pp. 227-242

Long-term and regional perspectives on recent change in lacustrine diatom communities in the tropical Andes

Understanding and managing the responses of natural systems to climate change requires knowing whether recent changes in ecosystem structure and function are within the bounds of natural variation or whether the systems are entering new states that are unprecedented. Several recent studies of the fossil diatom record of the last ~ 150 years in Andean lakes have shown changes in diatom species composition that suggest changes in lake thermal structure in response to regional climate warming. Yet these paleolimnological records are only a few hundred years in length, so it is unclear whether the systems have entered new states, with potentially severe consequences for ecosystem structure and function, or whether current trends are within the natural variability of the systems. Here, we use a recently compiled diatom database from tropical South America to explore the regional distribution and ecological controls of selected planktic diatom taxa that are associated with warming and changes in the lake thermal structure. We also review published Andean stratigraphic records that span thousands of years to characterize the long-term dynamics of relevant planktic species in response to past climate change. The contemporary data show that many planktic taxa have broad latitudinal and elevational distributions. The distributions of several taxa are correlated with surface water temperature, but most also are correlated with pH and/or conductivity. A review of existing stratigraphic data from Andean lakes demonstrates that rapid changes in diatom abundance, including abrupt increases followed by decades to centuries of near extirpation, are a common mode of population variation for some planktic taxa. Yet the majority of these published paleolimnological investigations are of lakes that are larger and differ in nutrient status and conductivity from the small dilute systems where recent species shifts have been observed. We propose that assessing the resilience of contemporary diatom communities and, by inference, lake ecosystems is best done by generating new records from Andean lakes of varied size and chemistry that span a millennium or more and hence a broader spectrum of climate conditions, coupled with new ecological and biogeographic studies that build upon ongoing research programs in the tropical Andes

The fossil diatoms of Lake Yambo, Ecuador: A possible record of El Niño events.

Abstract Fossil diatoms from a sediment core of Lake Yambo, a lake in an endorheic, desert region of the Ecuadorian Andes, provide a record of precipitation events that can be linked to the ENSO phenomenon. Abnormally high precipitation in the region during the 1982-83 El Niño caused a substantial drop in the lake's conductivity. The diatom flora in the lake changed from a community dominated by the halophilic species Cratícula halophila Cratícula halophila to one dominated by a freshwater species Aulacoseira distans Aulacoseira distans. Similar shifts in dominance can be seen at various points throughout the core. There also appears to be an increase in sediment deposition at these points. This paper provides the first evidence that the use of fossil diatoms from lake cores can be a valuable tool in reconstructing histories of El Niño events.Les diatomées fossiles du lac "Yambo", Équateur. Un registre sur les phénomèmes "El Niño" Résumé Des études limnologiques effectuées tous les ans depuis 1975 sur le lac "Yambo", situé dans une zone aride de la région inter-andine équatorienne, ont montré que l'eau du lac est à haute teneur en sels dissouts et que la flore de diatomées est riche en Cratícula halophila une espèce caractéristique des lacs saumâtres. En 1982-1983, l'un des phénomènes "El Niño" des plus inattendus, des plus intenses et des plus catastrophiques a frappé la côte sud-américaine du Pacifique provoquant une augmentation considérable de la précipitation sur la région du lac. Par suite de cette augmentation, la conductivité de l'eau a diminué de 30%. La communauté de diatommees a réagi à ce changement dans la chimique de l'eau et nous avons constaté une augmentation du nombre des diatomées Aulacoseira italica ainsi qu'une diminution des Cratícula halophila. Des analyses sur des diatomées fossiles en provenance des sédiments du lac "Yambo" montrent les mêmes fluctuations des deux espèces. Etant donné la localisation du lac, sur une zone très aride, les changements dans la salinité de l’eau ne peuvent être que le résultat des changements dramatiques survenus dans les précipitations. Par conséquent, il est possible d'interpréter le registre des changements survenus dans la communauté de diatomées du lac "Yambo" comme l'histoire des phénomènes "El Niño" au cours des 2500 ans de vie du lac.Diatomeas fósiles de la laguna de Yambo, Ecuador. Un posible récord de fenónemo El Niño Resumen Estudios limnológicos se han realizado cada año desde 1975 en la laguna de Yambo, ubicada en una parte árida de la región interandina de Ecuador. Estos estudios indican que el agua de esta laguna tiene una alta concentración de sales disueltas y la flora de diatomeas rica en Cratícula halophila, una especie característica de lagunas salobres. En 1982-1983 uno de los fenómenos «El Niño» más inesperados, intensos y catastróficos, azotó la costa sudamericana del Pacífico y causó un aumento considerable de la precipitación en la región de la laguna. Este aumento hizo que la condutividad del agua sea reducida en un 30%. La comunidad de diatomeas respondió a este cambio en la química del agua, y observamos un aumento en la abundancia de la diatomea Aulacoseira itálica, y una reducción en la abundancia de Cratícula halophila. Análisis de diatomeas fósiles en sedimentos de la laguna de Yambo revelan las mismas fluctuaciones en estas dos especies. Como la laguna se encuentra en una región muy árida, cambios en la salinidad del agua pueden resultar solamente como consecuencia de cambios dramáticos en la precipitación. Por lo tanto es factible interpretar el récord de cambios en la comunidad de diatomeas de la Laguna de Yambo como la historia de los fenómenos de «El Niño» ocurridos durante los 2500 años de existencia de la laguna.Steinitz-Kannan Miriam, Nienaber Mark A., Riedinger Melanie A., Kannan Ramamurthi. The fossil diatoms of lake Yambo, Ecuador. A possible records of El Niño events. In: Bulletin de l'Institut Français d'Études Andines, tome 22, N°1, 1993. Enregistrements du phénomène El Niño et d’événements ENSO en Amérique du Sud. pp. 227-242

Lake regionalization and diatom metacommunity structuring in tropical South America

Lakes and their topological distribution across Earth’s surface impose ecological and evolutionary constraints on aquatic metacommunities. In this study, we group similar lake ecosystems as metacommunity units influencing diatom community structure. We assembled a database of 195 lakes from the tropical Andes and adjacent lowlands (8°N–30°S and 58–79°W) with associated environmental predictors to examine diatom metacommunity patterns at two different levels: taxon and functional (deconstructed species matrix by ecological guilds). We also derived spatial variables that inherently assessed the relative role of dispersal. Using complementary multivariate statistical techniques (principal component analysis, cluster analysis, nonmetric multidimensional scaling, Procrustes, variance partitioning), we examined diatom–environment relationships among different lake habitats (sediment surface, periphyton, and plankton) and partitioned community variation to evaluate the influence of niche-and dispersal-based assembly processes in diatom metacommunity structure across lake clusters. The results showed a significant association between geographic clusters of lakes based on gradients of climate and landscape configuration and diatom assemblages. Six lake clusters distributed along a latitudinal gradient were identified as functional metacommunity units for diatom communities. Variance partitioning revealed that dispersal mechanisms were a major contributor to diatom metacommunity structure, but in a highly context-dependent fashion across lake clusters. In the Andean Altiplano and adjacent lowlands of Bolivia, diatom metacommunities are niche assembled but constrained by either dispersal limitation or mass effects, resulting from area, environmental heterogeneity, and ecological guild relationships. Topographic heterogeneity played an important role in structuring planktic diatom metacommunities. We emphasize the value of a guild-based metacommunity model linked to dispersal for elucidating mechanisms underlying latitudinal gradients in distribution. Our findings reveal the importance of shifts in ecological drivers across climatic and physiographically distinct lake clusters, providing a basis for comparison of broad-scale community gradients in lake-rich regions elsewhere. This may help guide future research to explore evolutionary constraints on the rich Neotropical benthic diatom species pool