Evaluating the efficacy of independent versus simultaneous management strategies to address ecological and genetic threats to population viability

Amanda Trask*, Sarah Fenn, Eric Bignal, DI McCracken, Pat Monaghan, Jane Reid

*Corresponding author for this work

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Abstract

Small, declining populations can face simultaneous, interacting ecological and genetic threats to viability. Conservation management strategies designed to tackle such threats independently may then prove ineffective. Population viability analyses that evaluate the efficacy of management strategies implemented independently versus simultaneously are then essential to the design of effective management plans, yet such quantitative evaluations are typically lacking.
We used stochastic individual‐based models, parameterised with high‐quality multi‐year demographic and genetic data, to evaluate the efficacy of independent or simultaneous ecological (supplementary feeding) and genetic (translocations to alleviate inbreeding) management strategies for a red‐billed chough (Pyrrhocorax pyrrhocorax) population of major conservation concern. This population is experiencing ecological threats from food limitation and genetic threats from escalating inbreeding. Conservation managers therefore face a dilemma: supplementary feeding may be ineffective if inbreeding is limiting stochastic population growth rate (λs), while translocations may be ineffective if food is limiting.
Model simulations suggested that the focal population will decline to extinction relatively rapidly with no conservation management (mean λs≈0.86) and with genetic management alone (λs≈0.90). Ecological management alone reduced but did not halt the population decline (λs≈0.93). However, simultaneous genetic and ecological management yielded population stability (λs≈1), with genetic rescue lasting ~25 years.
These outcomes arose because the capacity for translocations to alleviate inbreeding depression is limited by food availability, while supplementary feeding cannot achieve population viability in the presence of accumulating inbreeding. However, supplementary feeding improved environmental quality enough to allow expression of variance in fitness and thus inbreeding depression, meaning that reductions in inbreeding following translocations can increase λs.
Synthesis and applications. Our analyses suggest that simultaneous management of ecological and genetic threats will be critical to ensuring viability of Scotland's chough population; neither strategy independently is likely to achieve population persistence and may consequently waste conservation resources. Managers of other resource‐limited, inbred populations should consider that the efficacy of strategies designed to alleviate ecological and genetic threats may be interdependent, such that holistic management is essential to ensure population viability.
Original languageEnglish
Pages (from-to)2264-2273
Number of pages10
JournalJournal of Applied Ecology
Volume56
Issue number10
Early online date25 Jun 2019
DOIs
Publication statusPrint publication - Oct 2019

Fingerprint

viability
inbreeding
translocation
inbreeding depression
conservation management
population decline
food limitation
food availability
environmental quality
population growth
fitness
persistence
extinction
food
simulation

Keywords

  • Conservation management planning
  • Conservation intervention
  • Gene flow
  • Corvid
  • Extinction probability
  • Inbreeding-environment interactions
  • Population persistence
  • Population reinforcement

Cite this

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title = "Evaluating the efficacy of independent versus simultaneous management strategies to address ecological and genetic threats to population viability",
abstract = "Small, declining populations can face simultaneous, interacting ecological and genetic threats to viability. Conservation management strategies designed to tackle such threats independently may then prove ineffective. Population viability analyses that evaluate the efficacy of management strategies implemented independently versus simultaneously are then essential to the design of effective management plans, yet such quantitative evaluations are typically lacking.We used stochastic individual‐based models, parameterised with high‐quality multi‐year demographic and genetic data, to evaluate the efficacy of independent or simultaneous ecological (supplementary feeding) and genetic (translocations to alleviate inbreeding) management strategies for a red‐billed chough (Pyrrhocorax pyrrhocorax) population of major conservation concern. This population is experiencing ecological threats from food limitation and genetic threats from escalating inbreeding. Conservation managers therefore face a dilemma: supplementary feeding may be ineffective if inbreeding is limiting stochastic population growth rate (λs), while translocations may be ineffective if food is limiting.Model simulations suggested that the focal population will decline to extinction relatively rapidly with no conservation management (mean λs≈0.86) and with genetic management alone (λs≈0.90). Ecological management alone reduced but did not halt the population decline (λs≈0.93). However, simultaneous genetic and ecological management yielded population stability (λs≈1), with genetic rescue lasting ~25 years.These outcomes arose because the capacity for translocations to alleviate inbreeding depression is limited by food availability, while supplementary feeding cannot achieve population viability in the presence of accumulating inbreeding. However, supplementary feeding improved environmental quality enough to allow expression of variance in fitness and thus inbreeding depression, meaning that reductions in inbreeding following translocations can increase λs.Synthesis and applications. Our analyses suggest that simultaneous management of ecological and genetic threats will be critical to ensuring viability of Scotland's chough population; neither strategy independently is likely to achieve population persistence and may consequently waste conservation resources. Managers of other resource‐limited, inbred populations should consider that the efficacy of strategies designed to alleviate ecological and genetic threats may be interdependent, such that holistic management is essential to ensure population viability.",
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Evaluating the efficacy of independent versus simultaneous management strategies to address ecological and genetic threats to population viability. / Trask, Amanda; Fenn, Sarah; Bignal, Eric; McCracken, DI; Monaghan, Pat; Reid, Jane.

In: Journal of Applied Ecology, Vol. 56, No. 10, 10.2019, p. 2264-2273.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Evaluating the efficacy of independent versus simultaneous management strategies to address ecological and genetic threats to population viability

AU - Trask, Amanda

AU - Fenn, Sarah

AU - Bignal, Eric

AU - McCracken, DI

AU - Monaghan, Pat

AU - Reid, Jane

PY - 2019/10

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N2 - Small, declining populations can face simultaneous, interacting ecological and genetic threats to viability. Conservation management strategies designed to tackle such threats independently may then prove ineffective. Population viability analyses that evaluate the efficacy of management strategies implemented independently versus simultaneously are then essential to the design of effective management plans, yet such quantitative evaluations are typically lacking.We used stochastic individual‐based models, parameterised with high‐quality multi‐year demographic and genetic data, to evaluate the efficacy of independent or simultaneous ecological (supplementary feeding) and genetic (translocations to alleviate inbreeding) management strategies for a red‐billed chough (Pyrrhocorax pyrrhocorax) population of major conservation concern. This population is experiencing ecological threats from food limitation and genetic threats from escalating inbreeding. Conservation managers therefore face a dilemma: supplementary feeding may be ineffective if inbreeding is limiting stochastic population growth rate (λs), while translocations may be ineffective if food is limiting.Model simulations suggested that the focal population will decline to extinction relatively rapidly with no conservation management (mean λs≈0.86) and with genetic management alone (λs≈0.90). Ecological management alone reduced but did not halt the population decline (λs≈0.93). However, simultaneous genetic and ecological management yielded population stability (λs≈1), with genetic rescue lasting ~25 years.These outcomes arose because the capacity for translocations to alleviate inbreeding depression is limited by food availability, while supplementary feeding cannot achieve population viability in the presence of accumulating inbreeding. However, supplementary feeding improved environmental quality enough to allow expression of variance in fitness and thus inbreeding depression, meaning that reductions in inbreeding following translocations can increase λs.Synthesis and applications. Our analyses suggest that simultaneous management of ecological and genetic threats will be critical to ensuring viability of Scotland's chough population; neither strategy independently is likely to achieve population persistence and may consequently waste conservation resources. Managers of other resource‐limited, inbred populations should consider that the efficacy of strategies designed to alleviate ecological and genetic threats may be interdependent, such that holistic management is essential to ensure population viability.

AB - Small, declining populations can face simultaneous, interacting ecological and genetic threats to viability. Conservation management strategies designed to tackle such threats independently may then prove ineffective. Population viability analyses that evaluate the efficacy of management strategies implemented independently versus simultaneously are then essential to the design of effective management plans, yet such quantitative evaluations are typically lacking.We used stochastic individual‐based models, parameterised with high‐quality multi‐year demographic and genetic data, to evaluate the efficacy of independent or simultaneous ecological (supplementary feeding) and genetic (translocations to alleviate inbreeding) management strategies for a red‐billed chough (Pyrrhocorax pyrrhocorax) population of major conservation concern. This population is experiencing ecological threats from food limitation and genetic threats from escalating inbreeding. Conservation managers therefore face a dilemma: supplementary feeding may be ineffective if inbreeding is limiting stochastic population growth rate (λs), while translocations may be ineffective if food is limiting.Model simulations suggested that the focal population will decline to extinction relatively rapidly with no conservation management (mean λs≈0.86) and with genetic management alone (λs≈0.90). Ecological management alone reduced but did not halt the population decline (λs≈0.93). However, simultaneous genetic and ecological management yielded population stability (λs≈1), with genetic rescue lasting ~25 years.These outcomes arose because the capacity for translocations to alleviate inbreeding depression is limited by food availability, while supplementary feeding cannot achieve population viability in the presence of accumulating inbreeding. However, supplementary feeding improved environmental quality enough to allow expression of variance in fitness and thus inbreeding depression, meaning that reductions in inbreeding following translocations can increase λs.Synthesis and applications. Our analyses suggest that simultaneous management of ecological and genetic threats will be critical to ensuring viability of Scotland's chough population; neither strategy independently is likely to achieve population persistence and may consequently waste conservation resources. Managers of other resource‐limited, inbred populations should consider that the efficacy of strategies designed to alleviate ecological and genetic threats may be interdependent, such that holistic management is essential to ensure population viability.

KW - Conservation management planning

KW - Conservation intervention

KW - Gene flow

KW - Corvid

KW - Extinction probability

KW - Inbreeding-environment interactions

KW - Population persistence

KW - Population reinforcement

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DO - 10.1111/1365-2664.13464

M3 - Article

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EP - 2273

JO - Journal of Applied Ecology

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SN - 0021-8901

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