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Research Article

Biological correlates of extinction and persistence of primates in small forest fragments: a global analysis [ 388-403 ]

Matthew A. Gibbons and Alexander H. Harcourt

Abstract
Habitat loss and fragmentation are two of the main threats facing wildlife. The species at risk in small fragments are not a random subset of the original community. Understanding the biology behind the distinction between species at risk and more persistent species should help inform conservation efforts. We attempted to identify risky traits in a well-known taxon, the primates, by asking which traits distinguished taxa that differed in the size of the smallest fragment in which they were recorded. We assumed that taxa that could persist in smaller fragments were at less risk of extinction than those that needed larger fragments. The traits investigated are indicative of amount of habitat needed, reproductive rate, and specialization. We obtained from the literature information on the presence-absence of 68 primate species of 36 genera in forest fragments of less than 100 km2. Association between size of smallest fragment and biology was tested with regressions, Spearman correlations, two-sample t tests, and non-parametric Wilcoxon tests. We found no significant relationships between area of smallest fragment in which species or genera persisted and any of the biological parameters. We suggest that the most likely explanation for this unexpected finding is that the smallest fragments in which primates are currently studied are usually so small that all primate species in them are doomed in the long-term and therefore, no biological traits distinguish taxa at risk. The finding implies that conservation research and efforts should be directed at assessing the efficacy of forest fragments and small biological preserves in conserving primate species.


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General interest summaries (when available)
    English: In this study, the authors attempt to understand the biological basis of extinction risk in primates in small forest fragments. This was accomplished by asking which traits distinguished primate species that are at risk of extinction from those species that are more persistent in forest fragments. The traits investigated all related to various aspects of primate biology, including: the amount of habitat needed, reproductive rate, and types of specialization. They found no significant relationship between extinction risk and any of the biological parameters. The authors’ most likely explanation for this unexpected finding is that the forest fragments in which primates are currently studied are usually so small that all primate species in them are doomed in the long-term and therefore, no biological traits can distinguish at-risk species. The finding implies that conservation research and efforts should be directed at assessing the efficacy of forest fragments and small biological preserves in conserving primate species in the long-term.

    Español: Teniendo como concepto subyacente de que la perdida de hábitat y la fragmentación de este son dos de las amenazas principales para persistencia de la fauna Silvestre, Gibbons and Harcort señalan en su trabajo que los conservacionistas han conocido por mucho tiempo que las especies bajo riesgo en fragmentos pequeños, muy a menudo no son un segmento al azar de la comunidad original y que un entendimiento de la biología de la extinción puede refinar los esfuerzos de conservación de estas. Así, los autores investigaron rasgos de riesgo de extinción en primates, uno de los taxones mejor conocidos entre los mamíferos tropicales. Ellos encontraron la ausencia de una relación significativa entre el área de los fragmentos mas pequeños en que las especies o géneros persisten y cualquiera de los parámetros biológicos examinados. En vista de esto los autores sugieren que la explicación mas probable para este patrón es que los fragmentos más pequeños en los que se estudian a los primates, son tan pequeños que todas las especies que ahí se encuentran están destinadas a la extinción, ya que no encontraron un solo rasgo biológico que distinga a cada una del riesgo de extinción. También notan que muchos estudios de primates en fragmentos han sido, por lo general, llevados a cabo en fragmentos tan pequeños (mediana global = 1 km2) que son insuficientemente grandes para asegurar la persistencia, a largo plazo, de cualquier primate y que esto impide que resalten diferencias en la probabilidad de extinción entre especies. Los autores concluyen que la investigación y esfuerzos de conservación deben estar dirigidos más bien a evaluar la eficiencia de fragmentos de selva en combinación con reservas biológicas amplias como mecanismo para conservar la fauna de primates.

    Français: Dans leur article, Gibbons et Harcourt partent du postulat que le dépérissement et la fragmentation de l’habitat sont deux des principales menaces pour la vie sauvage. Ils notent que les conservationnistes savent depuis longtemps que les espèces menacées dans les petits fragments forestiers ne sont généralement pas des sous-groupes aléatoires de la communauté d’origine. Cette appréhension des phénomènes biologiques de l’extinction pourrait aider à optimiser les efforts menés en vue de la conservation. En examinant les caractéristiques du risque chez les primates, un taxon exceptionnellement bien connu des mammifères des forêts tropicales, les auteurs ont montré qu’il n’y avait pas de relations significatives entre la superficie de la plus petite parcelle où les espèces (ou le genre) s’étaient maintenues et les paramètres biologiques qu’ils avaient examinés. L’explication la plus probable de ces résultats inattendus repose, selon eux, sur le fait que les minuscules parcelles sur lesquelles on étudie actuellement les primates sont en général si petites que tous les primates qui y vivent sont condamnés à long terme, il n’existe par conséquent aucune caractéristique biologique différenciant les taxons menacés. Ils suggèrent également que de nombreuses études menées sur les primates vivant sur des parcelles l’ont été sur des parcelles trop petites pour le maintien à long terme de n’importe quel primate (médiane globale d’1 km2) et donc trop petites pour générer une différence entre les espèces, pour ce qui concerne la probabilité d’extinction. En conclusion, les auteurs estiment qu’il faudrait axer les efforts de la recherche en conservation sur l’évaluation de l’efficacité des fragments forestiers et des petites réserves biologiques mises en œuvre pour protéger les primates.

    Português: No seu artigo, Gibbons e Harcourt seguem a premissa de que a perda de habitat e fragmentação são duas das principais ameaças à vida silvestre. Eles apontam que os conservacionistas sabem há muito tempo que espécies em risco nos pequenos fragmentos são sempre um subconjunto não aleatório da comunidade original e esse entendimento da biologia de extinção pode ajudar a refinar os esforços conservacionistas. Investigando as ameaças de riscos entre primatas, um incomum bem conhecido taxon de mamíferos das florestas tropicais, os autores não encontraram nenhuma relação significativa entre a área dos pequenos fragmentos nos quais espécies ou gêneros persistem em nenhum dos parâmetros biológicos que eles examinaram. Eles sugerem que a melhor explicação para esse resultado inesperado é que os menores fragmentos nos quais os primatas são atualmente estudados são geralmente tão pequenos que todas as espécies de primatas neles são fadados a longo prazo e, portanto, nenhuma ameaça biológica distingue os taxa em risco. Eles sugerem também que muitos estudos de primatas em fragmentos estão sendo conduzidos em fragmentos muito pequenos para a persistência em longo prazo de qualquer primata (média global de 1 km2) e, portanto, muito pequeno para produzir uma diferença na probabilidade de extinção entre as espécies. Os autores concluíram que as pesquisas e esforços em conservação devem ser direcionados em estimar a eficiência de preservação dos pequenos fragmentos florestais biológicos na conservação de espécies de primatas.


    Translation to French by Clément Lermyte, Spanish by Alejandro Estrada, Portuguese by Marina Lapenta

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   Tropical Conservation Science is an open-access e-journal that publishes research relating to conservation of tropical forests and other tropical ecosystems.

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