Risk-weighted distinctiveness ranks species differently than risk alone, and the reference pool decides the ordering more than the risk metric does

Question: How do national and regional prioritization schemes for species conservation combine extinction risk metrics with phylogenetic diversity or functional distinctiveness to rank management urgency?

Answer

Across these papers, the dominant architecture is a composite score in which extinction risk multiplies a distinctiveness term, so that risk acts as the gate and distinctiveness as the discriminator among similarly threatened taxa — this is explicit in EDGE, FUSE/EFUSE, and the functional Red List Index. Taken together, the retrieved work supports three positions. First, the distinctiveness term carries most of the ranking leverage, and phylogenetic and functional distinctiveness are not interchangeable: rankings from EDGE and FUSE diverge significantly, so a national scheme built on one axis systematically omits species important on the other. Second, the reference pool — global versus regional, and which species are included — rather than the risk metric, determines who rises to the top, and global/national datasets reproduce regional expert status for only about half of species. Third, there is a live divergence between the metric-development literature and the operational national pipeline: the standardized protocol now being piloted for Kunming-Montreal Target 4 across 250 countries combines four risk-and-rarity criteria (global extinction risk, rate of decline, population or range restriction, endemism) and does not include phylogenetic diversity or functional distinctiveness at all, while regional EDGE downscalings remain bespoke research exercises. The honest answer is that the field has rich machinery for combining risk with distinctiveness but almost no evidence that any particular combination produces better management outcomes than risk-only ranking.

Composite indices multiply risk by distinctiveness, so the distinctiveness term dominates the ranking

EDGE combines a species' evolutionary distinctiveness with its extinction risk into a single score, and this is the metric through which phylogenetic information most often enters prioritization [9]. The FUSE framework does the same on the functional axis, ranking species by functional uniqueness and specialisation weighted by degree of threat [15]. The functional Red List Index takes the alternative form of reweighting an existing risk indicator, weighting species by morphological uniqueness at local or global scales while retaining the Red List Index's structure for tracking aggregate risk [5]. The EDGE2 programme extends this family to HED and HEDGE indices that score expected loss of phylogenetic diversity under future extinction, and these have now been generalised beyond trees to phylogenetic networks, discrete-trait feature diversity, and arbitrary biodiversity measures, with explicit expressions for the mean and variance of such scores [1]. The progression from simple formulations to game-theoretic and more abstract generalisations, and the strengths and limitations of each, is reviewed with attention to how the indices are used in practice [13]. Which index is defensible is itself a formal question: requirements to capture high phylogenetic diversity, or to keep species scores stable under uncertain edge lengths, drive the choice among candidate indices [3].

Phylogenetic and functional distinctiveness rank different species, making single-axis schemes incomplete by construction

A direct global comparison of EDGE and FUSE for 5,319 mammals and 7,932 birds found that species rankings differ significantly, indicating that the two metrics capture distinct and complementary aspects of biodiversity, and that strategies based solely on EDGE may overlook species with critical functional roles [15]. The proposed response is a merged measure, EFUSE, that folds evolutionary and functional distinctiveness into one score [15]. Functional distinctiveness also behaves differently from phylogenetic distinctiveness with respect to risk itself: birds with higher local uniqueness were more likely to be at higher risk of extinction, whereas globally unique species showed no such difference, and locally unique birds had a lower proportion of their range covered by site-based conservation measures [5]. On the phylogenetic side, threatened African vascular plants are not evolutionarily unique, yet extinction of all threatened species would erode 59% of the African plant tree of life, more than expected at random [10]. At community scale, rare species do not disproportionately contribute to phylogenetic diversity, and losing rare species may not cause disproportionate drops in phylogenetic diversity [4]. Together these results argue that risk-weighted distinctiveness is not a redundant refinement of risk-only ranking; it reorders the list.

Distinctiveness weighting changes the aggregate picture of risk, not only the order of a list

Applying the functional Red List Index to birds yielded higher aggregate extinction risk for both local and global weightings than the standard Red List Index [5]. Forward-looking analyses reach the same conclusion on the phylogenetic side: more than one fifth of angiosperm evolutionary history is at risk of extinction in the short term, and 9,945 threatened plant species disproportionately account for total evolutionary history at risk under the EDGE approach [12]. EDGE scores have now been estimated for over 130,000 species using a smoothed tree of life spanning more than 2.2 million species, alongside estimates of threatened phylogenetic diversity across all life [21]. For functional diversity, targeted recovery programmes prioritizing the 100 most functionally unique threatened birds could avoid 68% of projected functional diversity loss, even though blanket threat abatement across at least half of species ranges would prevent only about half of projected extinctions and functional diversity loss [11]. This is the strongest available argument that the weighting choice is consequential: a small, distinctiveness-selected species set captures a large share of projected diversity loss.

Downscaling to the national or regional scale reorders priorities, and global datasets do not substitute for regional schemes

Downscaling EDGE to the Iberian Peninsula identified 22 EDGE zones accounting for over 90% of angiosperm threatened evolutionary history, with several zones overlapping protected areas while others harbouring few but evolutionarily unique and highly threatened taxa remain largely unprotected [16]. For Indian birds, the top-ranked species by median EDGE score was the Bengal Florican, northeastern India was exceptional in its richness of evolutionarily unique and threatened species, and habitats of the top 5% of EDGE species are currently not adequately protected [9]. Across Africa, roughly 72% of threatened species and 79% of the top-1000 EDGE species are not found in any form of protected area [10]. The regional-scale problem is not merely one of resolution: when a regional list of 806 species of greatest conservation need was compared against a list compiled from global and national datasets, those datasets identified only about 55% of species statuses accurately for the region [17]. National assessment infrastructure is the binding constraint in many cases — Italian red lists cover only 10% of 76,845 taxa and only 1,346 taxa are listed under any legislative instrument, prompting a call for a national priority list founded on transparent prioritization protocols [19].

The operational national protocol for Target 4 is risk-and-endemism only, with distinctiveness entering through spatial mapping instead

The standardized protocol that identifies and ranks species needing urgent management action at the national level integrates four criteria aligned with Target 4 — global extinction risk, rate of decline, population or range restriction, and endemism — and was applied to all 250 countries and territories in the IUCN Red List, with pilot participants from eight countries reporting the ranked lists as scientifically robust and time-saving while stressing national context and the need for technical and financial support [14]. Endemism there functions as the national-scale stand-in for distinctiveness, and no retrieved paper tests whether endemism scores recover phylogenetic or functional distinctiveness rankings. National-scale prioritizations that do use distinctiveness-like criteria still treat it spatially rather than phylogenetically: site ranking for Conservation Imperatives uses threatened species counts, irreplaceability, ecoregional habitat share, and conversion pressure [6], and irreplaceability-based Key Biodiversity Area Criterion E applications proved highly sensitive to threshold, target, resolution, and cost settings [18].

Conflicts and gaps

The literature disagrees sharply on whether phylogenetic information earns its place. One analysis finds that phylogenetic relationships weakly explain species sensitivity to climate change, and that centers of diversity and endemism are not necessarily the regions most exposed to climate change, concluding that such metrics may overlook vulnerable species and regions [2]. That sits directly against the EDGE-based national and regional prioritizations that assume evolutionary rarity plus threat identifies the right species [12] [16]. A second conflict concerns scale: downscaling global EDGE to a region is presented as valid and replicable [16], while regional comparison shows global and national datasets misclassify roughly 45% of regional statuses [17], and the Target 4 protocol retains global extinction risk as its first criterion by design [14]. Third, no paper measures whether any distinctiveness-weighted ranking produced better conservation outcomes than a risk-only ranking; the 68% functional-diversity-loss figure is a modelled counterfactual, not an observed result [11]. Data coverage undercuts all of these rankings: Antarctic and Southern Ocean assessments are heavily biased toward vertebrates, with invertebrates only 4% assessed [8], and species in large angiosperm genera are less likely to be Red-List assessed and more likely to be threatened when assessed [7]. Finally, the Global Biodiversity Framework Monitoring Framework itself has coverage gaps, fully covering only 19% of the framework's ambition with headline and binary indicators and no indicators for 12% [20].

What would change the answer

A head-to-head counterfactual at national scale would settle whether the distinctiveness term earns its complexity: apply the Target 4 four-criterion protocol and an EDGE or EFUSE ranking to the same national species set under an identical fixed budget, and compute retained phylogenetic and functional diversity under each, extending the forward-projection method already used for functionally unique birds [11] to a risk-only comparator. The 250-country Target 4 output plus cross-taxa EDGE scores for over 130,000 species make a direct test of whether the protocol's endemism criterion recovers ED rank feasible without new fieldwork [14] [21]. Propagating index variance rather than point scores would harden any such test, since the mean and variance of HEDGE-type measures are now explicitly derivable [1], and index choice under uncertain edge lengths can be formalised rather than assumed [3]. Regionally, replicating the Iberian EDGE-zone workflow in a country with an existing national pilot list, and auditing whether the resulting zones survive corrected assessment coverage, would separate genuine priority signal from assessment bias.

References

[1] Mike Steel, Kristina Wicke, Arne Mooers. "Properties of biodiversity indices that incorporate future extinction risk". arxiv. 2026-08-19T00:00:00.000Z. URL: https://arxiv.org/abs/2602.16059

[2] Bondi, L., Prado-Monteiro, B., de Paula, L. F. A., Rosado, B. H. P., Porembski, S.. "Blind spots in traditional approaches to conservation prioritization in a climate change context". bioRxiv. 2025-10-03T00:00:00.000Z. URL: https://doi.org/10.1101/2025.10.01.679788

[3] Martin Frohn, Kerry Manson. "On properties driving diversity index selection". arxiv. 2025-02-12T00:00:00.000Z. URL: https://arxiv.org/abs/2502.07426

[4] Veldhuisen, L. N., Zepeda, V., Enquist, B. J., Dlugosch, K. M.. "Rare species do not disproportionately contribute to phylogenetic diversity in a subalpine plant community". bioRxiv. 2024-11-19T00:00:00.000Z. URL: https://doi.org/10.1101/2024.11.01.621409

[5] Stewart, K., Tobias, J. A., Butchart, S. H. M., Venditti, C., Carmona, C. P., Clements, C., Gonzalez-Suarez, M.. "A functional Red List Index for monitoring trends in functional diversity". bioRxiv. 2025-10-31T00:00:00.000Z. URL: https://doi.org/10.1101/2025.10.30.685639

[6] Gosling, J., Dinerstein, E., Joshi, A. R., Burgess, N. D., Mellin, H., Joppa, L., Bingham, H. C., McDermott-Long, O., Upton, J.. "A prioritization strategy for protecting Conservation Imperatives Sites". bioRxiv. 2026-05-05T00:00:00.000Z. URL: https://doi.org/10.64898/2026.05.01.721008

[7] Brown, M. J., Leao, T. C., Forest, F., Lucas, E., Walker, B. E., Nic Lughadha, E.. "Species in big angiosperm genera are priorities for conservation". bioRxiv. 2026-02-12T00:00:00.000Z. URL: https://doi.org/10.1101/2025.09.14.674653

[8] Farrant, M. G., Liu, W. P. A., McGeoch, M. A.. "Revealing the Widespread Bias of Extinction Risk in the Antarctic and the Southern Ocean". bioRxiv. 2026-04-26T00:00:00.000Z. URL: https://doi.org/10.64898/2026.04.23.720284

[9] Sharma, A., Goyal, N., Shah, D., VV, R.. "Using phylogenetic relationships to assess conservation priorities for birds in India". bioRxiv. 2025-08-04T00:00:00.000Z. URL: https://doi.org/10.1101/2025.08.04.668436

[10] Tiawoun, M. A. P., Phogole, B., Kandolo, S., Yessoufou, K.. "Over half of the phylogenetic diversity accumulated on the African plant tree of life may be eroded under current biodiversity crisis even though threatened species are not evolutionarily unique". bioRxiv. 2025-02-15T00:00:00.000Z. URL: https://doi.org/10.1101/2025.02.12.637779

[11] Stewart, K., Venditti, C., Carmona, C. P., Baker, J., Clements, C., Tobias, J. A., Gonzalez-Suarez, M.. "Threat reduction must be coupled with targeted recovery programmes to conserve global bird diversity". bioRxiv. 2025-01-13T00:00:00.000Z. URL: https://doi.org/10.1101/2025.01.09.632120

[12] Forest, F., Brown, R., Buerki, S., Colville, J. F., Moat, J., Lughadha, E. N., Owen, N. R., Raimondo, D. C., Rivers, M., Rosindell, J., Walker, B. E., Bachman, S. P., Pipins, S., Gumbs, R., Brown, M. J. M.. "300 billion years of angiosperm evolution at risk of extinction". bioRxiv. 2025-04-30T00:00:00.000Z. URL: https://doi.org/10.1101/2025.04.29.651190

[13] Kristina Wicke, Arne Mooers. "Phylogeny-based metrics of biodiversity: concepts and methods". arxiv. 2026-08-18T00:00:00.000Z. URL: https://arxiv.org/abs/2608.15278

[14] Akcakaya, H. R., Mannion, N. L. M., Morreale, J., Raimondo, D., Hoffmann, M., Butchart, S. H. M., Mair, L., Ridley, F., Rivers, M., Brant, C., Clifford, M., Joyce, M., Mileham, K., Felicity, C. N., Kusrini, M., Sunarto, S., Houston, J., Thomas, N., Maddock, S. T., Gonzalez-May, J. F., Triantis, K., Vavylis, D., Spiliopoulou, K., Gamatis, I. A., Danmallam, B. A., Ivande, S. T., Manu, S. A., Egbe, S., Onoja, J. D., Castellanos-Castro, C., Lopez-Gallego, C., Long, B., McGowan, P. J. K.. "Identifying and ranking species that need urgent management action to achieve Target 4 of the Global Biodiversity Framework". bioRxiv. 2026-10-19T00:00:00.000Z. URL: https://doi.org/10.64898/2026.04.11.717432

[15] Somekh, L., Griffin, J. N., Pimiento, C., Pearse, W. D.. "Integrating functional and phylogenetic perspectives reveals new priorities for bird and mammal conservation". bioRxiv. 2025-12-12T00:00:00.000Z. URL: https://doi.org/10.64898/2025.12.10.690976

[16] Ramos-Gutierrez, I., Pipins, S., Molina-Venegas, R., Fernandez-Mazuecos, M., Mejias, P. J., Moreno-Saiz, J. C., Forest, F.. "Safeguarding evolutionary history in a biodiversity hotspot: downscaling the EDGE metric to a regional application". bioRxiv. 2025-06-19T00:00:00.000Z. URL: https://doi.org/10.1101/2025.06.16.659859

[17] Starking, M. D., Rice, T. M., Terwilliger, K., Drummey, D., Frantz, M., Haffner, C. D., Hess, B., Holst, L., Marchand, M., Burgio, K. R.. "Strategic Conservation Prioritization Through Creating and Updating the Regional Species of Greatest Conservation Need (RSGCN) List in the Northeastern U.S.". bioRxiv. 2025-01-04T00:00:00.000Z. URL: https://doi.org/10.1101/2025.01.03.631241

[18] Mancini, G., Cimatti, M., Tzivanopoulos, M., Thuiller, W., Di Marco, M.. "Opportunities and challenges for applying Key BiodiversityAreas Criterion E at large spatial scales". bioRxiv. 2025-10-16T00:00:00.000Z. URL: https://doi.org/10.1101/2025.10.16.682361

[19] Miccolis, E., Rasotto, M. B., De Pascale, F., Pievani, T.. "How well is Italian biodiversity represented in red lists and conservation legislation? Taxonomic biases, coverage gaps and the assessment-to-legislation bottleneck". bioRxiv. 2026-07-01T00:00:00.000Z. URL: https://doi.org/10.64898/2026.06.30.730850

[20] Affinito, F., Butchart, S. H. M., Nicholson, E., Hirsch, T., Williams, J. M., Campbell, J. E., Ferrari, M. F., Gabay, M., Gorini, L., Kalamujic Stroil, B., Kohsaka, R., Painter, B., Pinto, J. C., Scholz, A. H., Straza, T. R. H., Tshidada, N., Vallecillo, S., Widdicombe, S., Gonzalez, A.. "Assessing coverage of the Monitoring Framework of the Kunming-Montreal Global Biodiversity Framework and opportunities to fill gaps.". bioRxiv. 2024-12-14T00:00:00.000Z. URL: https://doi.org/10.1101/2024.09.25.614896

[21] Guo, J., McTavish, E. J., Rosindell, J.. "Phylogenetic Diversity Across the Complete Tree of Life". bioRxiv. 2025-08-15T00:00:00.000Z. URL: https://doi.org/10.1101/2025.08.12.669825

How this survey was made

This survey answers one question: “How do national and regional prioritization schemes for species conservation combine extinction risk metrics with phylogenetic diversity or functional distinctiveness to rank management urgency?”

We keep our own collection of recent preprints and refresh it every day from bioRxiv, medRxiv, arXiv, PsyArXiv, SocArXiv and ChemRxiv. For each survey, we search that collection for recent work and keep the strongest matches: papers that use the same terms as the question, and papers on the same topic in different words.

The text was written from the titles and abstracts of those papers; the full texts were not read. Statements that draw on a particular paper are marked with a number in brackets. The reference list just above is the 21 papers whose work this text draws on, chosen from the 86 papers those searches returned; the rest of the shortlist is not printed. It is not a complete review of everything published on the question.

Treat this as a starting point and a reading list, not a peer-reviewed review. The searches behind this survey ran on October 21, 2026 and covered work from the previous two years.