Data from: Reduced competition may allow generalist species to benefit from habitat homogenization

1. Complex environments support high biodiversity and diverse microhabitat
availability, which may reduce the intensity of competition among species.
Both natural and anthropogenic disturbances reduce the structural
complexity of habitats, leading to homogenization. High abundances of
common, generalist species in disturbed habitats may be driven by reduced
competition from specialists in similar habitats. 2. We quantified habitat
availability for and utilization of three co-occurring arboreal geckos
(Australian native house geckos [Gehyra dubia], northern velvet geckos
[Oedura castelnaui], and eastern spiny-tailed geckos [Strophurus
williamsi]) in four replicated grazing regimes in an experimental grazing
trial in northeast Queensland, Australia. 3. Native house geckos were most
abundant in heavily grazed habitats, whereas the two other species rarely
co-occurred (either with each other or with native house geckos). Geckos
displayed resource partitioning of habitat features, such as tree species
and structural characteristics. 4. We found evidence of interspecific
competition among gecko species, in which native house geckos shifted
their habitat selection in the presence of velvet geckos. In the absence
of other geckos, native house geckos preferred rough, peeling bark and
dead trees; yet in the presence of velvet geckos, native house geckos
shifted away from dead trees, and used more structurally complex trees,
probably due to high niche overlap with velvet geckos. 5. Native house
geckos were more resistant to the negative effects of livestock grazing
than either velvet or spiny-tailed geckos. In the absence of other
species, native house geckos used a wider range of microhabitats. 6.
Synthesis and applications. Species assemblages are often the result of
multiple or complex factors, such as predation pressure, habitat
availability, or competitive interactions. The homogenizing effects on
habitat structure caused by livestock grazing reduced diversity and
suitability for microhabitat specialists. Reduced competition, therefore,
apparently promoted the abundance of microhabitat generalist species (G.
dubia), suggesting that livestock grazing was a mechanism leading to
homogenization and simplification of habitat structure, which ultimately
led to changes in the species composition through reduced competition.
Understanding species responses to disturbance, and more broadly, habitat
complexity, is crucial for our ability to maintain or increase biological
diversity in anthropogenically modified landscapes.