Reexamining the Minimum Viable Population Concept for Long-Lived Species

Authors

  • KEVIN T. SHOEMAKER,

    1. Department of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry, Syracuse, NY, U.S.A.
    Current affiliation:
    1. Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY 11794, U.S.A.
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  • ALVIN R. BREISCH,

    1. Endangered Species Unit, New York State Department of Environmental Conservation, Albany, NY 12207, U.S.A.
    Current affiliation:
    1. Altamont, NY 12009, U.S.A.
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  • JESSE W. JAYCOX,

    1. New York Natural Heritage Program, New York State Department of Environmental Conservation, Albany, NY 12207, U.S.A.
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  • JAMES P. GIBBS

    1. Department of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry, Syracuse, NY, U.S.A.
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Abstract

For decades conservation biologists have proposed general rules of thumb for minimum viable population size (MVP); typically, they range from hundreds to thousands of individuals. These rules have shifted conservation resources away from small and fragmented populations. We examined whether iteroparous, long-lived species might constitute an exception to general MVP guidelines. On the basis of results from a 10-year capture-recapture study in eastern New York (U.S.A.), we developed a comprehensive demographic model for the globally threatened bog turtle (Glyptemys muhlenbergii), which is designated as endangered by the IUCN in 2011. We assessed population viability across a wide range of initial abundances and carrying capacities. Not accounting for inbreeding, our results suggest that bog turtle colonies with as few as 15 breeding females have >90% probability of persisting for >100 years, provided vital rates and environmental variance remain at currently estimated levels. On the basis of our results, we suggest that MVP thresholds may be 1–2 orders of magnitude too high for many long-lived organisms. Consequently, protection of small and fragmented populations may constitute a viable conservation option for such species, especially in a regional or metapopulation context.

Reexaminando el Concepto de Población Mínima Viable para Especies Longevas Resumen

Resumen

Durante décadas, los biólogos de la conservación han propuesto reglas generales básicas para el tamaño poblacional mínimo viable (TMV); típicamente, fluctúan entre cientos y miles de individuos. Estas reglas han desplazado recursos para poblaciones pequeñas y fragmentadas. Examinamos si especies iteróparas, longevas pueden constituir una excepción a las reglas generales del TMV. Con base en los resultados de un estudio de captura-recaptura durante 10 años en el este de Nueva York (E.U.A.), desarrollamos un modelo demográfico integral para la tortuga Glyptemis muhlenbergii amenazada globalmente, considerada en peligro por la UICN (2011). Evaluamos la viabilidad poblacional de un amplio rango de abundancias iniciales y capacidades de carga. Sin considerar la endogamia, nuestros resultados sugieren que colonias de G. muhlenbergiicon tan solo 15 hembras reproductoras tiene >90% de probabilidad de persistir por >100 años, suponiendo que las tasas vitales y la variación ambiental permanecen en los niveles estimados actuales. Con base en nuestros resultados, sugerimos que los umbrales del TMV pueden ser 1–2 órdenes de magnitud más altos para muchos organismos longevos. Consecuentemente, la protección de poblaciones pequeñas y fragmentadas pueden constituir una opción de conservación para tales especies, especialmente en un contexto regional o metapoblacional.

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