The prediction that higher biodiversity leads to denser niche packing and thus higher community resistance to invasion has long been studied, with species richness as the predominant measure of diversity. However, few studies have explored how phylogenetic and functional diversity, which should represent niche space more faithfully than taxonomic diversity, influence community invasibility, especially across longer time frames and over larger spatial extents. We used a 15‐year, 150‐site grassland dataset to assess relationships between invasive plant abundance and phylogenetic, functional and taxonomic diversity of recipient native plant communities. We analysed the dataset both pooled across all surveys and longitudinally, leveraging time‐series data to compare observed patterns in invasion with those predicted by two community assembly processes: biotic resistance and competitive exclusion. We expected more phylogenetically and functionally diverse communities to exhibit greater resistance to invasion. With the pooled dataset, we found support for the long‐standing observation that communities with more native species have lower abundance of invasive species, and a more novel finding that more phylogenetically diverse communities had higher abundance of invasive species. We found no influence of aggregate (multivariate) functional diversity on invasion, but assemblages with taller plants, lower variability in plant height and lower seed mass were less invaded. Viewed longitudinally, the phylogenetic diversity relationship was reversed: the most phylogenetically diverse communities were most resistant to invasion. This apparent discrepancy suggests invasion dynamics are influenced by both site attributes and biotic resistance and emphasizes the value in studying invasion across time.
An important focus of community ecology, including invasion biology, is to investigate functional trait diversity patterns to disentangle the effects of environmental and biotic interactions. However, a notable limitation is that studies usually rely on a small and easy‐to‐measure set of functional traits, which might not immediately reflect ongoing ecological responses to changing abiotic or biotic conditions, including those that occur at a molecular or physiological level. We explored the potential of using the diversity of expressed genes—functional genomic diversity (FGD)—to understand ecological dynamics of a recent and ongoing alpine invasion. We quantified FGD based on transcriptomic data measured for 26 plant species occurring along adjacent invaded and pristine streambeds. We used an RNA‐seq approach to summarize the overall number of expressed transcripts and their annotations to functional categories, and contrasted this with functional trait diversity (FTD) measured from a suite of characters that have been traditionally considered in plant ecology. We found greater FGD and FTD in the invaded community, independent of differences in species richness. However, the magnitude of functional dispersion was greater from the perspective of FGD than from FTD. Comparing FGD between congeneric alien–native species pairs, we did not find many significant differences in the proportion of genes whose annotations matched functional categories. Still, native species with a greater relative abundance in the invaded community compared with the pristine tended to express a greater fraction of genes at significant levels in the invaded community, suggesting that changes in FGD may relate to shifts in community composition. Comparisons of diversity patterns from the community to the species level offer complementary insights into processes and mechanisms driving invasion dynamics. FGD has the potential to illuminate cryptic changes in ecological diversity, and we foresee promising avenues for future extensions across taxonomic levels and macro‐ecosystems.
more » « less- NSF-PAR ID:
- 10449477
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology and Evolution
- Volume:
- 11
- Issue:
- 17
- ISSN:
- 2045-7758
- Format(s):
- Medium: X Size: p. 12075-12091
- Size(s):
- ["p. 12075-12091"]
- Sponsoring Org:
- National Science Foundation
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Abstract Synthesis . Our results provide insight into the nuances of the diversity–invasibility relationship: invasion dynamics differed for different dimensions of diversity and depending on whether the relationship was evaluated longitudinally. Our findings highlight the limitations of using single time‐point ‘snapshots’ of community composition to infer invasion mechanisms. -
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Abstract Questions A recently introduced non‐native annual grass,
Ventenata dubia , is challenging previous conceptions of community resistance in forest mosaic communities in the Inland Northwest. However, little is known of the drivers and potential ecological impacts of this rapidly expanding species. Here we (1) identify abiotic and biotic habitat characteristics associated with theV .dubia invasion and examine how these differ betweenV .dubia and other problematic non‐native annual grasses,Bromus tectorum andTaeniatherum caput‐medusae ; and (2) determine how burning influences relationships betweenV .dubia and plant community composition and structure to address potential impacts on Inland Northwest forest mosaic communities.Location Blue Mountains of the Inland Northwest, USA.
Methods We measured environmental and plant community characteristics in 110 recently burned and nearby unburned plots. Plots were stratified to capture a range of
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Abstract Phylogenetic and functional diversity are theorised to increase invasion resistance. Experimentally testing whether plant communities higher in these components of diversity are less invasible is an important step for guiding restoration designs.
To investigate how phylogenetic and functional diversity of vegetation affect invasion resistance in a restoration setting, we used experimental prairie restoration plots. The experiment crossed three levels of phylogenetic diversity with two levels of functional diversity while species richness was held constant. We allowed invaders to colonise plots; these included native species from neighbouring plots and non‐native invasive species from a surrounding old field. We tested if invader biomass was influenced by phylogenetic and functional diversity, and phylogenetic and hierarchical trait distances between invaders and planted species. We binned each invader into three categories: native species from neighbouring experimental plots (
site‐specific invaders ), native species not part of the experimental species pool (native invaders ) or non‐native species (non‐native invaders ).Counter to expectation, both non‐native and native invaders became more abundant in more phylogenetically diverse plots. However, plots with higher abundance of planted Asteraceae, a dominant family of the tallgrass prairie, had lower invader biomass for both native and non‐native invaders.
We also found that hierarchical trait differences shaped invasion. The species that became most abundant were non‐native invaders that were taller, and native invaders with low specific leaf area relative to planted species. Site‐specific invaders were not influenced by any plot‐level diversity metrics tested.
Synthesis and application : Our results suggest that greater phylogenetic diversity may lower resistance to invasion. This effect may be due to more even but sparser niche packing in high‐diversity plots, associated with greater availability of unsaturated niche space for colonisation. However, trait composition fostered invasion resistance in two ways in our study. First, establishment of native species with strongly dominant traits may confer invasion resistance. Second, species mixes that optimise trait differences between planted vegetation and likely invaders may enhance invasion‐resistance. -
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