A range-wide model of contemporary, omnidirectional connectivity for the threatened Mojave desert tortoise

Miranda E. Gray, Brett G. Dickson, Kenneth E. Nussear, Todd C. Esque, Tony Chang

Research output: Contribution to journalArticle

Abstract

As habitat destruction leads to species extinctions globally, conservation planning that accounts for population-level connectivity and gene flow is an urgent priority. Models that only approximate habitat potential are incomplete because areas of high habitat potential may be isolated, whereas intermixed areas of lower habitat potential may still be critical for maintaining connectivity between and among populations. We developed a range-wide, omnidirectional (coreless) connectivity model and map for the threatened Mojave desert tortoise at a high spatial resolution (30 m), based on empirical movement data and a circuit-theoretic approach to estimating connectivity. Specifically, we first estimated habitat potential (i.e., quality) for tortoise movement (as distinct from habitat potential more generally) across its range using hypotheses based on the published literature, linear mixed models, multiple environmental factors derived from remotely sensed data, and recent solar and wind development footprints. The resultant raster output was used to represent landscape conductance in a circuit-theoretic model of connectivity, which relates the flow of electrical current through a circuit to the movement of tortoises through the landscape. We then modeled potential connectivity across the range of the tortoise using Circuitscape software and the Julia numerical programming language. Intermediate distances from minor roads, intermediate values of annual average maximum temperature, and increasing density of desert washes were among the strongest predictors of movement habitat quality. There was also strong evidence for increased habitat quality for movement with increasing amounts of vegetation cover. The resulting connectivity model and map was determined to accurately reflect important areas for tortoise movement, but we encourage others to do their own evaluation of the model within local areas of interest and as more data become available. Accordingly, the map can provide an important component to improve management decisions that have the potential to influence the conservation of connected desert tortoise populations throughout the range.

Original languageEnglish (US)
Article numbere02847
JournalEcosphere
Volume10
Issue number9
DOIs
StatePublished - Sep 1 2019

Fingerprint

Gopherus agassizii
Mojave Desert
connectivity
desert
tortoises
habitats
habitat
habitat quality
electric current
conservation planning
raster
tortoise
habitat destruction
vegetation cover
footprint
gene flow
roads
deserts
spatial resolution
environmental factor

Keywords

  • circuit theory
  • connectivity
  • conservation
  • Mojave desert tortoise

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology

Cite this

A range-wide model of contemporary, omnidirectional connectivity for the threatened Mojave desert tortoise. / Gray, Miranda E.; Dickson, Brett G.; Nussear, Kenneth E.; Esque, Todd C.; Chang, Tony.

In: Ecosphere, Vol. 10, No. 9, e02847, 01.09.2019.

Research output: Contribution to journalArticle

Gray, Miranda E. ; Dickson, Brett G. ; Nussear, Kenneth E. ; Esque, Todd C. ; Chang, Tony. / A range-wide model of contemporary, omnidirectional connectivity for the threatened Mojave desert tortoise. In: Ecosphere. 2019 ; Vol. 10, No. 9.
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