Multiple life-stage inbreeding depression impacts demography and extinction risk in an extinct-in-the-wild species

J. G. Ewen,S. Newland,M. Laut,S. Canessa,L. Barnhart Duenas,J. Wang,G. M. Ferrie,A. Moehrenschlager,A. E. Trask

doi:10.1038/s41598-020-79979-4

Abstract

Inbreeding can depress individuals’ fitness traits and reduce population viability. However, studies that directly translate inbreeding depression on fitness traits into consequences for population viability, and further, into consequences for management choices, are lacking. Here, we estimated impacts of inbreeding depression (B, lethal equivalents) across life-history stages for an extinct-in-the-wild species, the sihek (Guam kingfisher, Todiramphus cinnamominus). We then projected population growth under different management alternatives with our B estimates incorporated, as well as without inbreeding depression (B = 0) or with a conventional default B. We found that inbreeding depression severely impacted multiple life-history stages, and directly translated into an effect on population viability under management alternatives. Simulations including our B estimates indicated rapid population decline, whereas projections without inbreeding depression or with default B suggested very gradual population decline. Further, our results demonstrate that incorporation of B across life-history stages can influence management decisions, as projections with our B estimates suggested a need to switch to increased breeding management to avoid species extinction and support wild releases. Our results demonstrate that magnitude of B across life-history stages can translate into demographic consequences, such that incorporation of multiple life-stage B into population models can be important for informed conservation management decision-making.

Highlights

Inbreeding can depress individuals’ fitness traits and reduce population viability
Our study provides a rare example of directly translating B into effects on population viability under management alternatives, and shows that incorporation of the appropriate B value can influence management decision-making
We found no significant effect of individual f on first-year survival (B = − 0.67, 95% CI − 1.34 to 2.70, p = 0.684) or second-year survival (B = − 6.77, 95%CI − 3.83 to 17.37, p = 0.209), suggesting no detectable inbreeding depression in these traits (Supplementary Appendix S2)

Summary

Introduction

Inbreeding can depress individuals’ fitness traits and reduce population viability. studies that directly translate inbreeding depression on fitness traits into consequences for population viability, and further, into consequences for management choices, are lacking. We projected population growth under different management alternatives with our B estimates incorporated, as well as without inbreeding depression (B = 0) or with a conventional default B. We found that inbreeding depression severely impacted multiple life-history stages, and directly translated into an effect on population viability under management alternatives. Whether detected effects of inbreeding depression on fitness traits directly translate into effects on population growth rate and viability remains controversial[5,6,7]. The magnitude of inbreeding depression expressed across life-history stages is rarely quantified and incorporated into population projections of management alternatives for threatened species, despite such lack of incorporation potentially risking poor management decisions[8,9]. For detected effects of inbreeding depression to impact population viability, magnitude of B on different fitness traits must translate into an impact on population growth rate[6]. Detected impacts of inbreeding depression across life-history stages may not necessarily directly translate into appreciable impacts on population viability (e.g.7)

Methods

Results

Conclusion