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Resource partitioning between ungulate populations in arid environments

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.


A posteriori habitat types with resource partitioning ratio (size) and combined density index (color) for scimitar‐horned oryx and dorcas gazelle. Point size is proportional to the ratio between oryx and gazelle density (small size indicates a shared habitat, and large size indicates a partitioned habitat), and color represents the density of oryx minus gazelle (red representing oryx dominance and blue gazelle dominance). A posteriori habitats are based on cluster analysis (Appendix S5), the difference in oryx and gazelle density, and the key predictor variables: rock cover and plant species richness.
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ece32218-fig-0003: A posteriori habitat types with resource partitioning ratio (size) and combined density index (color) for scimitar‐horned oryx and dorcas gazelle. Point size is proportional to the ratio between oryx and gazelle density (small size indicates a shared habitat, and large size indicates a partitioned habitat), and color represents the density of oryx minus gazelle (red representing oryx dominance and blue gazelle dominance). A posteriori habitats are based on cluster analysis (Appendix S5), the difference in oryx and gazelle density, and the key predictor variables: rock cover and plant species richness.

Mentions: The cluster analysis indicated that six habitats were distinguishable (Appendix S5) and showed separation on the axes of plant species richness and rock cover (Fig. 3). The habitats were defined as follows: (A) rocky plains with very sparse vegetation (plant cover <1.5%); (B) rocky plains with sparse vegetation (<3%); (C) sand dunes with intermediate vegetation (<20%); (D) densely vegetated (>50%) dune wadis, dominated by herbaceous cover of Stipagrostis spp.; and (E) densely vegetated (>40%) wadis characterized by Retama raetam. The final group (F) is a complex conglomerate of wadi and plain habitat with intermediate vegetation density (<20%). These habitats summarize the landscape from an ungulate's perspective and reveal the patterns of resource partitioning between gazelle and oryx in finer resolution (Fig. 3).


Resource partitioning between ungulate populations in arid environments
A posteriori habitat types with resource partitioning ratio (size) and combined density index (color) for scimitar‐horned oryx and dorcas gazelle. Point size is proportional to the ratio between oryx and gazelle density (small size indicates a shared habitat, and large size indicates a partitioned habitat), and color represents the density of oryx minus gazelle (red representing oryx dominance and blue gazelle dominance). A posteriori habitats are based on cluster analysis (Appendix S5), the difference in oryx and gazelle density, and the key predictor variables: rock cover and plant species richness.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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

ece32218-fig-0003: A posteriori habitat types with resource partitioning ratio (size) and combined density index (color) for scimitar‐horned oryx and dorcas gazelle. Point size is proportional to the ratio between oryx and gazelle density (small size indicates a shared habitat, and large size indicates a partitioned habitat), and color represents the density of oryx minus gazelle (red representing oryx dominance and blue gazelle dominance). A posteriori habitats are based on cluster analysis (Appendix S5), the difference in oryx and gazelle density, and the key predictor variables: rock cover and plant species richness.
Mentions: The cluster analysis indicated that six habitats were distinguishable (Appendix S5) and showed separation on the axes of plant species richness and rock cover (Fig. 3). The habitats were defined as follows: (A) rocky plains with very sparse vegetation (plant cover <1.5%); (B) rocky plains with sparse vegetation (<3%); (C) sand dunes with intermediate vegetation (<20%); (D) densely vegetated (>50%) dune wadis, dominated by herbaceous cover of Stipagrostis spp.; and (E) densely vegetated (>40%) wadis characterized by Retama raetam. The final group (F) is a complex conglomerate of wadi and plain habitat with intermediate vegetation density (<20%). These habitats summarize the landscape from an ungulate's perspective and reveal the patterns of resource partitioning between gazelle and oryx in finer resolution (Fig. 3).

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&#8208;associated threats. Here, we implement an integrated likelihood approach to relate scimitar&#8208;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&#8208;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&#8208;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.