Inferring temporal shifts in a restored grassland from taxonomic, phylogenetic and functional diversity patterns

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Zhe Ren, David J. Gibson and Laurel R. Wilson, School of Biological Sciences, Southern Illinois University Carbondale, Carbondale, IL, Sara Baer, Kansas Biological Survey and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, Loretta Johnson, Division of Biology, Kansas State University, Manhattan, KS

Background/Question/Methods
Grasslands are vital to landscape recreation and nature protection. Nowadays, areas of native grassland have decreased and become fragmented particularly in industrial countries. As a result, grassland restoration is broadly applied to preserve biodiversity and improve ecosystem services. Although the ecotypes of dominant species in grassland have been studied, it is still unclear: 1. if a temporal shift of grassland taxonomic, phylogenetic, and functional diversity occurs during restoration; and 2. if ecotypic variation among the dominant species affects grassland taxonomic, phylogenetic, and functional diversity. We established a reciprocal common garden to study the long-term effect of different ecotypes of the dominant grasses on restoration at Carbondale, Illinois, in 2009. Species composition was measured in two 1 m2 quadrats per plot in 2012, 2014, 2018, and 2019, retaining the maximum percentage canopy cover obtained by each species from each survey for analyses. Linear mixed models were applied to analyze the effect of ecotypes and year on taxonomic, phylogenetic, and functional diversity.
Results/Conclusions
Taxonomic richness decreased 59% from 2012 (18.2±3.8 per m2) to 2019 (7.5±3.1 per m2), whereas phylogenetic diversity (phylogenetic sesMPD), and functional diversity (functional sesMPD) indicated gradual shifts from over-dispersed communities in 2012 to clustered patterns in 2019. The generalized linear mixed model showed significant differences in taxonomic richness in an interaction between year and ecotype (Wald’s-χ2=15.44, P=0.02). Meanwhile, the linear mixed model found significant effects on both phylogenetic and functional diversity in interactions between year and ecotype (F6,63=2.43, P=0.04; F6,63=2.33, P=0.04, respectively). For instance, non-local ecotypes CKS or EKS in 2012 presented highly over-dispersed (positive sesMPD) phylogenetic and functional patterns among all sampling units. In contrast, the phylogenetic and functional patterns of local ecotype SIL became highly clustered (negative sesMPD) in 2019. Our results support a hypothesis that ecotypic differentiation among the dominant species may affect temporal shifts in biodiversity during grassland restoration, influencing species presence and noticeably changing the phylogenetic and functional community structure. Based on our research, when appropriate grass sources are available, restoration with transfer can be an efficient and valuable ecosystem restoration technique.