The umbrella-species concept, which suggests that conservation strategies designed for one species may benefit co-occurring species, has been promoted as a framework for conservation planning. Nevertheless, there has been considerable variation in the outcome of empirical tests of this concept that has led researchers to question its value, so we used data from 15 published studies in a meta-analysis to evaluate whether conservation of putative umbrella species also conserves co-occurring species. We tested the effectiveness of putative umbrella species categorized by taxonomic group, taxonomic similarity to co-occurring species, body size, generality of resource use, and trophic level to evaluate criteria proposed to guide the selection of umbrella species. We compared species richness and number of individuals (by species and higher taxonomic group) between sites with and without putative umbrella species to test whether more co-occurring species were present in greater abundances when the area or resource needs of umbrella species were met. Species richness and abundance of co-occurring species were consistently higher in sites where umbrella species were present than where they were not and for conservation schemes with avian than with mammalian umbrella species. There were no differences in species richness or species abundance with resource generalist or specialist umbrella species or based on taxonomic similarity of umbrella and co-occurring species. Taxonomic group abundance was higher in across-taxonomic umbrella species schemes than when umbrella species were of the same taxon as co-occurring species. Co-occurring species had similar, or higher, species richness with small-bodied umbrella species relative to larger-bodied umbrella species. The only significant difference among umbrella species categorized by trophic level was that species richness was higher with omnivorous than it was with carnivorous avian umbrella species. Our results suggest there is merit to the umbrella-species concept for conservation, but they do not support the use of the criteria we used to identify umbrella species.

Summary1. The umbrella species approach, where conservation actions targeted for one or a group of species should benefit the broader community, may provide an effective framework to guide habitat restoration. This requires congruence in the response of umbrella and co-occurring species to environmental stress and recovery, and the identification of potential mechanisms by which co-occurring species benefit from conservation of an umbrella species. 2. Past evaluations of this approach have considered only the presence/absence of umbrella species. In addition to the presence/absence, we quantified abundance and biomass of both umbrella and co-occurring species to support a more quantitative evaluation of species co-occurrence. Floodplain ponds are restored in British Columbia and the Pacific Northwest to benefit coho salmon Oncorhynchus kisutch, a presumptive umbrella species. To test its effectiveness as an umbrella species, we assessed the relationships between species richness, abundance and biomass of aquatic vertebrates, including vertebrates of conservation concern ('listed'), and benthic invertebrates and the abundance and biomass of juvenile coho. We used ordination to evaluate relationships between species' abundance and biomass and environmental attributes. 3. Positive relationships were identified between coho abundance and biomass and species richness, abundance and biomass of fish and listed species. These relationships were negative for benthic invertebrates. Listed species were located close to coho in ordinations, suggesting they respond to similar environmental features while benthic invertebrates clustered away from coho. 4. Synthesis and applications. We found that where our umbrella species coho is most productive, so are other listed species and fish in general, a relationship that would not have been evident had evaluated species richness alone. We also reported strong relationships between some environmental features manipulated in the habitat restoration and the presence and productivity of coho and co-occurring species. Our study demonstrates the umbrella species approach has potential to guide habitat restoration when there is congruence in the response of umbrella and co-occurring species to environmental attributes that can be manipulated in the restoration. Where this is possible, one can use restoration designed for one or several umbrella species and successfully restore habitats that are viable for other species, including listed species.

We conducted a two-year field study (2000-2001) in the Housatonic River, Massachusetts (USA) to determine if we could detect in situ population-level effects on largemouth bass (Micropterus salmoides) exposed to elevated levels of polychlorinated biphenyls (PCBs). Calculated whole-body PCB concentrations in adult bass in 2002 averaged 121 mg/kg (range = 34-556 mg/kg). Polychlorinated biphenyl concentrations in young-of-year (YOY) composites in 2000 and 2002 averaged 28 mg/kg (range = 21-41 mg/kg) and 19 mg/kg (range = 16-24 mg/kg), respectively. Laboratory studies of fish have reported PCB toxicity at exposure levels below and within the range of those found in the Housatonic River. We evaluated five field-derived metrics: reproductive activity, relative abundance of YOY, YOY growth rates, adult growth, and adult condition to determine whether we could detect effects of PCBs in the largemouth bass population. These computed metrics, when compared with data sets assembled for numerous largemouth bass populations in North America, provided no evidence of population-level impairment. Results of this study suggest that PCB tissue concentrations associated with effects in laboratory studies do not necessarily translate to detectable effects on largemouth bass populations in their natural environment.

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