Application of isoscapes to determine geographic origin of terrestrial wildlife for conservation and management

doi:10.1016/j.biocon.2018.10.019

Biological Conservation

Volume 228, December 2018, Pages 268-280

https://doi.org/10.1016/j.biocon.2018.10.019 Get rights and content

Highlights

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Isotope techniques to geolocate organisms can be applied in a conservation context.
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Common analytical approaches can be applied to a variety of study questions.
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Selecting thresholds to delineate of origin results in accuracy-precision tradeoffs.
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Case studies demonstrate that model sensitivity can differ with species.

Abstract

Accounting for migration and connectivity of mobile species across the annual cycle can present challenges for conservation and management efforts. The use of stable isotope approaches to examine the movements and ecology of wildlife has been widespread over the past two decades. Hydrogen stable isotope (δ²H) composition, in particular, has been frequently used to provide insight into the origin of migratory species, although isotopes of other elements are sometimes used. These intrinsic markers can yield valuable information about distributions of wildlife on a broad scale, with reduced labor and expense compared to tracking and telemetry. Many of the applications of isotopes to migratory species to date have addressed connectivity and origin, and studies in support of conservation biology are less common. In addition, there are few guides for how to best employ these methods for management. Therefore, we provide an overview for the wildlife conservation and management community on how stable isotope methods may be applied to conservation problems and a primer on the process for assigning geographic origins to terrestrial wildlife. We also discuss best practices for employing environmental isoscapes (isotopic distributions across landscapes), rescaling functions, and the assumptions required for assignment to origin while highlighting emerging issues in the modeling process. Finally, we provide example applications to illustrate these principles, and we explore strengths and limitations of this approach in a conservation context.

Section snippets

Introduction to using isoscapes to infer geographic origin

The most abundant elements in living organisms (hydrogen, carbon, nitrogen, and oxygen) have naturally occurring stable isotopes with additional neutrons (²H, ¹³C, ¹⁵N, ¹⁷O, ¹⁸O) that tend to accumulate in molecules and tissues differentially than forms with fewer neutrons (¹H, ¹²C, ¹⁴N, ¹⁶O). Naturally occurring variation in the stable isotope composition of these environmentally available biological building blocks can be characterized across space and time and used to model expected isotope

Example research questions

For the purposes of this review, we focus on how stable isotope data can be used to address conservation and management problems where knowledge of geographic origin is useful. Stable isotope data can also provide inferences about diets, which is informative for different types of conservation studies (Newsome et al., 2012, Newsome et al., 2007) beyond the scope of this review. We have divided geography-based management questions into three general categories, as below. For illustrative

Data sources

To date, the most commonly used stable isotope approach to infer terrestrial wildlife movements is based on geographic variation in δ²H and δ¹⁸O values of water. In particular, δ²H and δ¹⁸O values in precipitation vary considerably across continental scales (Fig. 1) due to preferential rainout of the isotopically heavier water molecules across continental and elevational gradients (Dansgaard, 1964). The local water isotope signal is assimilated into seasonally grown tissue via diet and drinking

Conducting geographic assignments with probability-based models

Assignment models for geographic inferences can be divided into two general types: nominal or continuous. These represent cases in which individuals are assigned either to a limited number of groups or to a continuous but defined geographic range, respectively (Wunder, 2012). Nominal assignment methods require a priori and isotopically distinct groupings that often are geographic in nature (Brennan et al., 2015; Miller et al., 2012; Vander Zanden et al., 2014a; Wunder and Norris, 2008). The

Case studies

Decisions made during the assignment modeling process have consequences relevant to wildlife conservation. In this section, we use datasets of known-origin individuals of two species to illustrate how to consider potential tradeoffs associated with analysis of stable isotope data to explore two common conservation questions. Both of these examples involve decisions made at the model application step (Section 4.5, Fig. 2). In our first example, we consider the consequences of incorporating

Conclusions

The use of isoscapes for studying geographic histories of migratory animals has considerable utility for the field of wildlife conservation and management. However, the utility of this approach depends on meeting associated assumptions and on the decisions regarding the analysis and interpretation of results. This overview illustrates a range of applications and provides guidance in the use of stable isotope-based models to study animal movement and ecology. The datasets of known origin birds

Acknowledgements

Funding for this work was provided by the California Energy Commission [grant EPC-14-061]. Golden eagle samples that were not previously published (Katzner et al., 2017; Nelson et al., 2015) were provided by SB Lewis, CL McIntyre, TL Booms, and KH Rogers. The capturing and handling of mountain plovers was accomplished under the regulatory authority of the U.S. Fish and Wildlife Service and in compliance with the Colorado State University Animal Care and Use Committee (protocol #00-049A-02).

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View full text

ReviewApplication of isoscapes to determine geographic origin of terrestrial wildlife for conservation and management

Highlights

Abstract

Section snippets

Introduction to using isoscapes to infer geographic origin

Example research questions

Data sources

Conducting geographic assignments with probability-based models

Case studies

Conclusions

Acknowledgements

Ecol. Indic.

Mamm. Biol.

J. Geochem. Explor.

Sci. Justice

Stable isotope analyses as a forensic tool to monitor illegally traded African grey parrots

Anim. Conserv.

Tracing origins of waterfowl using the Saskatchewan River Delta: incorporating stable isotope approaches in continent-wide waterfowl management and conservation

Condor

Origins and migratory patterns of bats killed by wind turbines in southern Alberta: evidence from stable isotopes

Ecosphere

Using stable-hydrogen isotopes to reveal immigration in an Arctic-breeding songbird population

Mov. Ecol.

Bird species distribution maps of the world. Version 6.0

Reporting stable-isotope ratios in ecology: recommended terminology, guidelines and best practices

Waterbirds

Hydrogen isotope variability in prairie wetland systems: implications for studies of migratory connectivity

Ecol. Appl.

Isoscapes: spatial pattern in isotopic biogeochemistry

Annu. Rev. Earth Planet. Sci.

Interpolating the isotopic composition of modern meteoric precipitation

Water Resour. Res.

Treatment methods for the determination of δ2H and δ18O of hair keratin by continuous-flow isotope-ratio mass spectrometry

Rapid Commun. Mass Spectrom.

Global application of stable hydrogen and oxygen isotopes to wildlife forensics

Oecologia

Isoscapes to address large-scale earth science challenges

EOS Trans. AGU

Geographic assignment with stable isotopes in IsoMAP

Methods Ecol. Evol.

IsoMAP: Isoscapes Modeling, Analysis and Prediction (version 1.0). [WWW Document]. The IsoMAP Project

Linking otolith microchemistry and dendritic isoscapes to map heterogeneous production of fish across river basins

Ecol. Appl.

Strontium isotopes delineate fine-scale natal origins and migration histories of Pacific salmon

Sci. Adv.

Advances in tracking small migratory birds: a technical review of light-level geolocation

J. Field Ornithol.

Using hydrogen isotopes to assign origins of bats in the eastern United States

J. Mammal.

The potential breeding range of slender-billed curlew Numenius tenuirostris identified from stable-isotope analysis

Bird Conserv. Int.

Breeding origin and spatial distribution of migrant and resident harriers in a Mediterranean wintering area: insights from isotopic analyses, ring recoveries and species distribution modelling

J. Ornithol.

Fall migration and breeding origins of Canada warblers moving through northern Colombia

J Field Ornithol.

Provenance does matter: links between winter trophic segregation and the migratory origins of European robins

Oecologia

Advances in linking wintering migrant birds to their breeding-ground origins using combined analyses of genetic and stable isotope markers

PLoS One

Using geologgers to investigate bimodal isotope patterns in painted buntings (Passerina ciris)

Auk

Temporal sources of deuterium (δD) variability in waterfowl feathers across a prairie-to-boreal gradient

Condor

Modelling isoscapes using mixed models

bioRxiv

Seasonal distribution of migratory tree bats (Lasiurus and Lasionycteris) in North America

J. Mammal.

Stable hydrogen isotope analysis of bat hair as evidence for seasonal molt and long-distance migration

J. Mammal.

Evidence of late-summer mating readiness and early sexual maturation in migratory tree-roosting bats found dead at wind turbines

PLoS One

Continental-scale, seasonal movements of a heterothermic migratory tree bat

Ecol. Appl.

Stable isotopes in precipitation

Tellus

An assessment of factors affecting population growth of the mountain plover

Avian Conserv. Ecol.

Stable isotope analyses—a method to distinguish intensively farmed from wild frogs

Ecol. Evol.

Tracking multi-generational colonization of the breeding grounds by monarch butterflies in eastern North America

Review
Application of isoscapes to determine geographic origin of terrestrial wildlife for conservation and management

Treatment methods for the determination of δ²H and δ¹⁸O of hair keratin by continuous-flow isotope-ratio mass spectrometry

A multi-isotope (δ²H, δ¹³C, δ¹⁵N) approach to establishing migratory connectivity of barn swallow (Hirundo rustica)

Assessing geographic origins of teal (Anas crecca) through stable-hydrogen (δ²H) isotope analyses of feathers and ring-recoveries

Assigning birds to geographic origin using feather hydrogen isotope ratios (δ²H): importance of year, age, and habitat