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Resource partitioning between ungulate populations in arid environments

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ABSTRACT

Herbivores are major drivers of ecosystem structure, diversity, and function. Resilient ecosystems therefore require viable herbivore populations in a sustainable balance with environmental resource availability. This balance is becoming harder to achieve, with increasingly threatened species reliant on small protected areas in increasingly harsh and unpredictable environments. Arid environments in North Africa exemplify this situation, featuring a biologically distinct species assemblage exposed to extreme and volatile conditions, including habitat loss and climate change‐associated threats. Here, we implement an integrated likelihood approach to relate scimitar‐horned oryx (Oryx dammah) and dorcas gazelle (Gazella dorcas) density, via dung distance sampling, to habitat, predator, and geographic correlates in Dghoumes National Park, Tunisia. We show how two threatened sympatric ungulates partition resources on the habitat axis, exhibiting nonuniform responses to the same vegetation gradient. Scimitar‐horned oryx were positively associated with plant species richness, selecting for vegetated ephemeral watercourses (wadis) dominated by herbaceous cover. Conversely, dorcas gazelle were negatively associated with vegetation density (herbaceous height, litter cover, and herbaceous cover), selecting instead for rocky plains with sparse vegetation. We suggest that adequate plant species richness should be a prerequisite for areas proposed for future ungulate reintroductions in arid and semi‐arid environments. This evidence will inform adaptive management of reintroduced ungulates in protected environments, helping managers and planners design sustainable ecosystems and effective conservation programs.

No MeSH data available.


Spatial distribution of scimitar‐horned oryx (A), dorcas gazelle (B), and both species combined (C; density of oryx minus gazelle, red representing oryx dominance, blue gazelle dominance and yellow shared habitats) per habitat patch (as defined by the a priori approach). White represents unsampled regions (no transect located within the patch) where density is unknown.
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ece32218-fig-0004: Spatial distribution of scimitar‐horned oryx (A), dorcas gazelle (B), and both species combined (C; density of oryx minus gazelle, red representing oryx dominance, blue gazelle dominance and yellow shared habitats) per habitat patch (as defined by the a priori approach). White represents unsampled regions (no transect located within the patch) where density is unknown.

Mentions: Both species demonstrated spatial and resource selection, resulting in nonrandom, but overlapping distributions (Fig. 4). Overall, oryx selected strongest for habitat D (selection ratio 0.54: key resource area), followed by habitats C and E (0.24 and 0.13 respectively), whereas gazelle selected habitat B (0.61: key resource area), followed by A (0.14). The diversity of habitat use was effectively equal for oryx (H' = 0.55) and gazelle (H' = 0.51). These patterns can be surmised by three subresponses (Fig. 3): oryx dominated dune and wadi habitats (habitats C, D and E); gazelle dominated rocky plains (A and B); and shared resource use of the intermediate habitat (F). Although habitats may appear homogenous such as rocky plains, they may function very differently for the focal species. Gazelle were four times as likely to select rocky plains with sparse vegetation (habitat B) than very sparse vegetation (habitat A).


Resource partitioning between ungulate populations in arid environments
Spatial distribution of scimitar‐horned oryx (A), dorcas gazelle (B), and both species combined (C; density of oryx minus gazelle, red representing oryx dominance, blue gazelle dominance and yellow shared habitats) per habitat patch (as defined by the a priori approach). White represents unsampled regions (no transect located within the patch) where density is unknown.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016655&req=5

ece32218-fig-0004: Spatial distribution of scimitar‐horned oryx (A), dorcas gazelle (B), and both species combined (C; density of oryx minus gazelle, red representing oryx dominance, blue gazelle dominance and yellow shared habitats) per habitat patch (as defined by the a priori approach). White represents unsampled regions (no transect located within the patch) where density is unknown.
Mentions: Both species demonstrated spatial and resource selection, resulting in nonrandom, but overlapping distributions (Fig. 4). Overall, oryx selected strongest for habitat D (selection ratio 0.54: key resource area), followed by habitats C and E (0.24 and 0.13 respectively), whereas gazelle selected habitat B (0.61: key resource area), followed by A (0.14). The diversity of habitat use was effectively equal for oryx (H' = 0.55) and gazelle (H' = 0.51). These patterns can be surmised by three subresponses (Fig. 3): oryx dominated dune and wadi habitats (habitats C, D and E); gazelle dominated rocky plains (A and B); and shared resource use of the intermediate habitat (F). Although habitats may appear homogenous such as rocky plains, they may function very differently for the focal species. Gazelle were four times as likely to select rocky plains with sparse vegetation (habitat B) than very sparse vegetation (habitat A).

View Article: PubMed Central - PubMed

ABSTRACT

Herbivores are major drivers of ecosystem structure, diversity, and function. Resilient ecosystems therefore require viable herbivore populations in a sustainable balance with environmental resource availability. This balance is becoming harder to achieve, with increasingly threatened species reliant on small protected areas in increasingly harsh and unpredictable environments. Arid environments in North Africa exemplify this situation, featuring a biologically distinct species assemblage exposed to extreme and volatile conditions, including habitat loss and climate change‐associated threats. Here, we implement an integrated likelihood approach to relate scimitar‐horned oryx (Oryx dammah) and dorcas gazelle (Gazella dorcas) density, via dung distance sampling, to habitat, predator, and geographic correlates in Dghoumes National Park, Tunisia. We show how two threatened sympatric ungulates partition resources on the habitat axis, exhibiting nonuniform responses to the same vegetation gradient. Scimitar‐horned oryx were positively associated with plant species richness, selecting for vegetated ephemeral watercourses (wadis) dominated by herbaceous cover. Conversely, dorcas gazelle were negatively associated with vegetation density (herbaceous height, litter cover, and herbaceous cover), selecting instead for rocky plains with sparse vegetation. We suggest that adequate plant species richness should be a prerequisite for areas proposed for future ungulate reintroductions in arid and semi‐arid environments. This evidence will inform adaptive management of reintroduced ungulates in protected environments, helping managers and planners design sustainable ecosystems and effective conservation programs.

No MeSH data available.