Habitat heterogeneity enables spatial and temporal coexistence of native and invasive macrophytes in shallow lake landscapes

Jorge Salgado, Carl D. Sayer, Nigel Willby, Ambroise G. Baker, Ben Goldsmith, Suzanne McGowan, Thomas A. Davidson, Patrik Bexell, Ian R. Patmore, Beth Okamura

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Abstract

Macrophyte invasive alien species (IAS) fitness is often hypothesised to be associated with beneficial environmental conditions (environmental matching) or species-poor communities. However, positive correlations between macrophyte IAS abundance and native plant richness can also arise, due to habitat heterogeneity (defined here as variation in abiotic and native biotic conditions over space and time). We analysed survey and palaeoecological data for macrophytes in satellite lakes along the Upper Lough Erne (ULE) system (Northern Ireland, UK), covering a gradient of eutrophication and connectivity to partition how environmental conditions, macrophyte diversity and habitat heterogeneity explained the abundance of Elodea canadensis, a widely distributed non-native macrophyte in Europe. E. canadensis abundance positively correlated with macrophyte richness at both the within- and between-lake scales indicating coexistence of native and invasive species over time. E. canadensis was also more prolific in highly connected and macrophyte-rich lakes, but sparser in the more eutrophic-isolated ones. Partial boosted regression trees revealed that in eutrophic-isolated lakes, E. canadensis abundances correlated with water clarity (negatively), plant diversity (positively), and plant cover (negatively) whereas in diverse-connected lakes, beta diversity (both positively and negatively) related to most greatly E. canadensis abundance. Dense macrophyte cover and unfavourable environmental conditions thus appear to confer invasibility resistance and sufficient habitat heterogeneity to mask any single effect of native biodiversity or environmental matching in controlling E. canadensis abundance. Therefore, in shallow lake landscapes, habitat heterogeneity variously enables the coexistence of native macrophytes and E. canadensis, reducing the often-described homogenisation effects of invasive macrophytes.

Original languageEnglish
JournalRiver Research and Applications
DOIs
Publication statusPublished - 15 Jul 2021

Bibliographical note

Funding Information:
We thank the Natural History Museum, London, for supporting fieldwork as part of J.S. PhD. Further support for fieldwork was provided by a Hugh Cary Gilson Memorial Award from the Freshwater Biological Association. We thank the University of Nottingham and the UKRI‐GCRF Living Deltas Hub for supporting J.S. as a postdoctoral researcher and Universidad Católica de Colombia for supporting J.S. research. We thank CIRCE under the AU ideas programme for supporting TD contribution. We thank the Lake BESS project (Natural Environment Research Council grant, NE/K015486/1) for funding sediment dating and paleoecological analysis of the Gole lake core and for supporting AB. We thank NIEA for provision of water chemistry data for the central lake (Upper Lough Erne), many landowners for site access and hospitality, Charlotte Hall, Stephen Brooks and Peter Hammond for fieldwork assistance and Laura Petetti for provision of data from the ULET2 core and for fieldwork assistance.

Funding Information:
Natural Environment Research Council, Grant/Award Number: NE/K015486/1; Universidad Católica de Colombia; UKRI‐GCRF Living Deltas Hub; University of Nottingham; Hugh Cary Gilson Memorial Award from the Freshwater Biological Association; Natural History Museum, London Funding information

Publisher Copyright:
© 2021 The Authors. River Research and Applications published by John Wiley & Sons Ltd.

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