Phylogenetic and species‐based taxonomic descriptions of community structure may provide complementary information about the mechanisms driving community assembly across different environments. Environmental filtering may have similar effects on taxonomic and phylogenetic diversity under the assumption of niche conservatism, whereas competitive exclusion could produce contrasting patterns in these diversity metrics. In grassland restorations, these diversity patterns might then reveal potential assembly mechanisms underlying the impacts of restoration and management conditions on community structure. We compared plant community structure (alpha diversity, composition, and within‐site beta diversity) from both phylogenetic and taxonomic perspectives. Using surveys from 120 tallgrass prairie restorations in four regions of the Midwestern United States, we examined the effects of four potential drivers or environmental gradients: precipitation in the first year of restoration, seed mix richness, time since last prescribed fire, and restoration age, and included soil conditions as a covariate. First‐year precipitation influenced taxonomic community structure, but had weak effects on phylogenetic diversity and composition. Similarly, greater seed mix richness increased taxonomic diversity but did not influence phylogenetic diversity. Taxonomic, but not phylogenetic, diversity generally was lower in older restorations and those with a longer time since the last prescribed fire. These drivers consistently explained more variation in taxonomic than phylogenetic diversity and composition, perhaps in part because species turnover was largely among related species, producing weak impacts on phylogenetic community measures. An impact of precipitation on taxonomic but not phylogenetic diversity suggests that there may not be large differences in drought tolerance among clades that would cause phylogenetic patterns to arise from this environmental filter. Declining taxonomic diversity but not phylogenetic diversity is consistent with competitive exclusion as an assembly mechanism when competition is strongest between related species.
Land degradation is a leading cause of biodiversity loss, and understanding its consequences on freshwater ecosystems remains a priority for improving the effectiveness of restoration practices and ecosystem assessments. Freshwater monitoring programs use macroinvertebrates to assess the biotic effects of degradation and management actions, often using the ratio of observed to expected taxa at a site—O/E—for this purpose. Despite the power of the O/E approach, large amounts of data are required to generate an expectation and it can be difficult to define a threshold value for degraded sites. An alternative assessment tool is phylogenetic diversity, which is widely used in academic biology but rarely applied in management despite empirical correlations between phylogenetic diversity and management targets such as ecosystem structure and function. Here, we use macroinvertebrate data from 1400 watersheds, collected since 1998, to evaluate the potential for phylogenetic metrics to inform evaluations of management practices. These watersheds were chosen because their low disturbance levels and high habitat heterogeneity have made them problematic to assess with O/E. Phylogenetic diversity detected degradation of assemblages and was sensitive enough to parse impacts to inform management actions. This is particularly notable given the phylogenetic metrics, unlike O/E, did not require additional “baseline” data. Site disturbance and broader environmental drivers strongly predicted site phylogenetic structure, providing management objectives to increase site quality. We call on others to consider using phylogenetic diversity to complement existing O/E schemes, particularly in systems where O/E is insufficient to prioritize management objectives.
more » « less- NSF-PAR ID:
- 10452721
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecosphere
- Volume:
- 12
- Issue:
- 3
- ISSN:
- 2150-8925
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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