Compare taxonomic richness vs functional richness on degradation gradient detection power

Answer

The corpus does not contain a formal statistical-power comparison of taxonomic species richness against functional richness (FRic), so the question cannot be answered as a power ranking. What it does show is that FRic responds at least as strongly as species richness along land-use and degradation gradients in the studies that report both, and in some systems it responds where taxonomic metrics do not. In 112 French reservoirs, taxonomic diversity metrics did not respond to the tested anthropogenic stressors while all functional diversity metrics were affected by non-native species, though the regressions had low explanatory power 1dbeb5f9. In a global bird analysis, land-use diversity predicted both taxonomic and functional richness, and the functional link stayed strong after controlling for taxonomic richness 0ee8ec7a d1636cad. In a desert steppe, both Patrick species richness and FRic declined with degradation 1dbeb5f9.

Summary

FRic is the better-supported candidate for detecting contraction of functional space, and in several studies it adds information beyond species count. It is not shown to have greater statistical power at early degradation: no source gives matched effect sizes, confidence intervals or detection thresholds for the two metrics from one design. The desert-steppe study illustrates the limit: the Patrick-FRic association was strong (R² > 0.7) in non-degraded and lightly degraded sites but became non-significant (R² < 0.7) in moderately and heavily degraded sites, so the two metrics tracked each other early and diverged later 1dbeb5f9. The dung beetle record (Barragan 2011) asserts that FRic declined more sharply than species richness, but its record gives only a qualitative ranking ('moderate' against 'higher' sensitivity) with no effect size, so it is a directional claim rather than a measured comparison 9fb1308b. Related Lab Board material in the task hints is only a test post and carries no evidence.

Evidence

• Li et al. 2024 (desert steppe) - Patrick richness and FRic both declined with degradation; correlation R² > 0.7 in non-degraded and light stages, not significant with R² < 0.7 in moderate and heavy stages. The same record carries Sagouis 2017 (112 French reservoirs; taxonomic metrics unresponsive, functional metrics affected by non-native species; low explanatory power) and Chen 2019 (74 Chinese streams; a functional-taxonomic multimetric index with FRic had a steeper response to 0-10% urban and 0-20% agricultural land use than the taxonomic index; the index is not standalone FRic). 1dbeb5f9
• Martinez-Nunez et al. 2023 (global birds) - land-use diversity predicted both taxonomic and functional richness, the link was particularly consistent for functional richness; the record also cites Gomez-Hernandez 2021 (macromycetes), where both richness and FRic declined with urbanization. d1636cad
• Synthesis record of land-use studies - 15,780 bird grid cells across six realms, functional richness rising two- to three-fold across the land-use-diversity range in several realms; a Germany plant study with steep FRic loss and more moderate functional divergence loss after forest conversion. States explicitly that a universal power advantage is not established. 0ee8ec7a
• Barragan et al. 2011 (dung beetles) - FRic recorded as more sensitive than species richness; qualitative only. 9fb1308b

Methodology

All four verified facts are used. I separated studies that measure both metrics at the same sites from those that measure a combined index or a single metric, and I did not pool effect sizes across taxa because none were reported on a common scale. Qualitative winner labels in the records (for example 'FRic wins') were treated as the recorders' verdicts, not as measurements. The previous published version's verdict that FRic wins is softened to the conditional statement above, because two of the four records themselves say the power advantage is not established.

Limitations

• No source reports effect sizes, confidence intervals or detection thresholds for taxonomic richness against FRic from one design, so statistical power cannot be compared 0ee8ec7a.
• Taxa, scales and pressures differ (birds, fungi, beetles, plants, fish, macroinvertebrates), and the Chen result concerns a combined index 1dbeb5f9.
• The reservoir regressions had low explanatory power 1dbeb5f9.
• Barragan 2011 and the headline verdict in Martinez-Nunez's record are qualitative 9fb1308b d1636cad.