| dc.description.abstract | Aim: Lakes in the Ecuadorean Andes span different altitudinal and climatic regions,
from inter Andean plateau to the high-elevation
páramo, which differ in their historical
evolution in the several centuries since the pioneering Humboldt expeditions.
Here, we evaluate temporal and spatial patterns of change in diatom assemblages
between historical (palaeolimnological) and modern times.
Location: Ecuadorean Andes
Methods: We compared historical (pre-1850)
and modern (2017) diatom assemblages
from 21 lakes and determined the relative role of environmental (water chemistry
and climate) and spatial factors (distance-based
Moran's eigenvectors maps) on both
assemblages using non-metric
multidimensional scaling (NMDS) with environmental
fitting. In addition, we used redundancy analysis (RDA) with variance partitioning to
estimate the historical (measured using downcore assemblage composition) effects
on modern diatom assemblages and identified diatom species that contributed most
to dissimilarity between the two times.
Results: Diatom changes between the two time points were limited across the group
of lakes, as indicated by the NMDS ordination. Variance partitioning indicated that
modern diatom assemblages were affected by environmental and spatial effects, but
with non-significant
effects of past diatom species composition. Ordination results
showed that variables related to elevation and water chemistry affected both modern
and historical diatom assemblages. Diatom species with the best fit on NMDS
axes (i.e. >70%) were influenced by elevation and climatic variables. The most distinctive
change between the two time periods was the higher relative abundance of
planktic diatom species in top-core
assemblages of some lakes, but in a highly variable
fashion across gradients of increased elevation and water depth.
Main conclusions: Landscape palaeolimnological analyses of varied Ecuadorean
Andean lakes demonstrate both environmental and spatial controls on diatom metacommunities.
The multi-faceted
ecological control of the altitudinal gradient on both
historic and contemporary diatom assemblages suggests species sorting and dispersal
constraints operating at centennial time-scale.
Although a few individual lakes
show substantive change between the 1850s and today, the majority of lakes do not,
and the analysis suggests the resilience of lakes at a regional scale. We emphasize the
potential of diatom palaeolimnological approaches in biogeography to test ecologically relevant hypotheses of the mechanisms driving recent limnological
change in high-elevation
tropical lakes. | |
