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.

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Published in Ecology and Evolution, v. 8, issue 16, p. 7865-7878.

© 2018 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Funded by NSF EAR‐1338694, NSF‐EAR1251678, NASA 15‐BIODIV15‐0013, and National Geographic #8672‐09 grants to SF. The Colombia diatom database collection was funded from NWO‐WOTRO grant WB 75368 to H. Hooghiemstra and MV, and Inter‐American Institute for Global Change (IAI grant No. CRN3038)‐NSF (grant GEO‐1128040) to MV. Lowland sampling in Brazil, Argentina and parts of Bolivia was funded by National Geographic #9797‐15 and NSF EAR 1541247 to MM. Ecuador sampling was supported by NSF Grants BSR‐8021539 and BSR‐8202658 to Paul Colinvaux and MSK.

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Additional supporting information may be found online in the Supporting Information section at the end of the article.

Diatom community data, water chemistry, and geo‐climatic variables of lakes are available at Dryad Digital Repository http://doi.org/doi:10.5061/dryad.6jk8h77.

ece34305-sup-0001-appendixs1-s6.docx (1582 kB)
Supporting Information