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2 resultados encontrados para: AUTOR: Gilbert, Jessica
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Species distribution models (SDMs) are statistical tools used to develop continuous predictions of species occurrence. ‘Integrated SDMs’ (ISDMs) are an elaboration of this approach with potential advantages that allow for the dual use of opportunistically collected presence-only data and site-occupancy data from planned surveys. These models also account for survey bias and imperfect detection through the use of a hierarchical modelling framework that separately estimates the species–environment response and detection process. This is particularly helpful for conservation applications and predictions for rare species, where data are often limited and prediction errors may have significant management consequences. Despite this potential importance, ISDMs remain largely untested under a variety of scenarios. We performed an exploration of key modelling decisions and assumptions on an ISDM using the endangered Baird’s tapir (Tapirus bairdii) as a test species. We found that site area had the strongest effect on the magnitude of population estimates and underlying intensity surface and was driven by estimates of model intercepts. Selecting a site area that accounted for the individual movements of the species within an average home range led to population estimates that coincided with expert estimates. ISDMs that do not account for the individual movements of species will likely lead to less accurate estimates of species intensity (number of individuals per unit area) and thus overall population estimates.

This bias could be severe and highly detrimental to conservation actions if uninformed ISDMs are used to estimate global populations of threatened and data-deficient species, particularly those that lack natural history and movement information. However, the ISDM was consistently the most accurate model compared to other approaches, which demonstrates the importance of this new modelling framework and the ability to combine opportunistic data with systematic survey data. Thus, we recommend researchers use ISDMs with conservative movement information when estimating population sizes of rare and data-deficient species. ISDMs could be improved by using a similar parameterization to spatial capture–recapture models that explicitly incorporate animal movement as a model parameter, which would further remove the need for spatial subsampling prior to implementation.


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Using a novel model approach to assess the distribution and conservation status of the endangered Baird’s tapir
Schank, Cody J. ; Cove, Michael V. (coaut.) ; Kelly, Marcella J. (coaut.) ; Mendoza Ramírez, Eduardo (coaut.) ; O´Farril Cruz, Elsa Georgina (coaut.) ; Reyna Hurtado, Rafael Ángel (coaut.) ; Meyer, Ninon France Victoire (coaut.) ; Jordan, Christopher A. (coaut.) ; González Maya, José F. (coaut.) ; Lizcano, Diego J. (coaut.) ; Moreno, Ricardo (coaut.) ; Dobbins, Michael T. (coaut.) ; Montalvo, Víctor (coaut.) ; Sáenz Bolaños, Carolina (coaut.) ; Carillo Jiménez, Eduardo (coaut.) ; Estrada, Nereyda (coaut.) ; Cruz Díaz, Juan Carlos (coaut.) ; Sáenz, Joel (coaut.) ; Spínola, Manuel (coaut.) ; Carver, Andrew (coaut.) ; Fort, Jessica (coaut.) ; Nielsen, Clayton K. (coaut.) ; Botello, Francisco (coaut.) ; Pozo Montuy, Gilberto (coaut.) ; Rivero Hernández, Crysia Marina (coaut.) ; De la Torre, José Antonio (coaut.) ; Brenes Mora, Esteban (coaut.) ; Godínez Gómez, Oscar (coaut.) ; Wood, Margot A. (coaut.) ; Gilbert, Jessica (coaut.) ; Miller, Jennifer A. (coaut.) ;
Contenido en: Diversity and Distributions Vol. 23, no. 12 (December 2017), p. 1459–1471 ISSN: 1809-127X
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Aim: We test a new species distribution modelling (SDM) framework, while comparing results to more common distribution modelling techniques. This framework allows for the combination of presence-only (PO) and presence-absence (PA) data and accounts for imperfect detection and spatial bias in presence data. The new framework tested here is based on a Poisson point process model, which allows for predictions of population size. We compared these estimates to those provided by experts on the species. Species and Location: Presence data on Baird’s tapir (Tapirus bairdii) throughout its range from southern México to northern Colombia were used in this research, primarily from the years 2000 to 2016. Methods: Four SDM frameworks are compared as follows: (1) Maxent, (2) a presence-only (PO) SDM based on a Poisson point process model (PPM), (3) a presence-absence (PA) SDM also based on a PPM and (4) an Integrated framework which combines the previous two models. Model averaging was used to produce a single set of coefficient estimates and predictive maps for each model framework. A hotspot analysis (Gi*) was used to identify habitat cores from the predicted intensity of the Integrated model framework. Results: Important variables to model the distribution of Baird’s tapir included land cover, human pressure and topography. Accounting for spatial bias in the presence data affected which variables were important in the model. Maxent and the Integrated model produced predictive maps with similar patterns and were considered to be more in agreement with expert knowledge compared to the PO and PA models.

Main conclusions: Total abundance as predicted by the model was higher than expert opinion on the species, but local density estimates from our model were similar to available independent assessments. We suggest that these results warrant further validation and testing through collection of independent test data, development of more precise predictor layers and improvements to the model framework.