DataSheet_1_Patterns and consequences of invasion of tropical montane forests by Cestrum aurantiacum Lindl. in the Western Ghats.pdf

In the montane forest-grassland mosaics of the Western Ghats, land cover conversion to silviculture and agriculture over the last five decades has resulted in both loss of natural habitats and widespread invasion of remnant habitat patches. While invasion of the grassland habitats of the mosaic has been relatively well studied, there have been few attempts to understand the extent to which forest habitats (locally known as sholas) have been affected by the spread of exotic species. Here we examine the patterns and impacts of invasion of shola forest understoreys by Cestrum aurantiacum Lindl., an exotic shrub species. At the landscape scale, we demonstrate that the presence and abundance of this invasive in shola understories is negatively related to distance from tea plantations. Further, the intensity of invasion is higher in areas with greater seasonality of temperature and lower mean annual precipitation. At the patch scale, invasion is greatest at shola edges and away from stream courses. We find that C. aurantiacum abundance has negatively affected the regeneration of native shola tree species as well as the abundance of native shola understorey shrubs. Fifty three percent of invaded plots had no native shrubs present. In plots where both C. aurantiacum and native shrubs were present in large enough numbers, we found evidence of negative spatial dependence between stem locations of C. aurantiacum and native shrubs. Our findings have important implications for the management and conservation of these mosaics.</p

Study area map of Bandipur Tiger Reserve.

<p>Study area and survey design for Bandipur Tiger Reserve, India (2012) showing protected area boundary, forest road sign-survey routes and 13-km²-grid array. Inset: location of the study area and adjoining protected areas.</p

Dhole distribution patterns.

<p>Patterns of landscape-scale occupancy: dhole distribution in the Western Ghats of Karnataka, India (2006–2007). (a) Naïve estimate and (b) estimated probabilities of occupancy.</p

Patterns and Determinants of Habitat Occupancy by the Asian Elephant in the Western Ghats of Karnataka, India

<div><p>Understanding species distribution patterns has direct ramifications for the conservation of endangered species, such as the Asian elephant <i>Elephas maximus</i>. However, reliable assessment of elephant distribution is handicapped by factors such as the large spatial scales of field studies, survey expertise required, the paucity of analytical approaches that explicitly account for confounding observation processes such as imperfect and variable detectability, unequal sampling probability and spatial dependence among animal detections. We addressed these problems by carrying out ‘detection—non-detection’ surveys of elephant signs across a <i>c</i>. 38,000-km² landscape in the Western Ghats of Karnataka, India. We analyzed the resulting sign encounter data using a recently developed modeling approach that explicitly addresses variable detectability across space and spatially dependent non-closure of occupancy, across sampling replicates. We estimated overall occupancy, a parameter useful to monitoring elephant populations, and examined key ecological and anthropogenic drivers of elephant presence. Our results showed elephants occupied 13,483 km² (<i>SE</i> = 847 km²) corresponding to 64% of the available 21,167 km² of elephant habitat in the study landscape, a useful baseline to monitor future changes. Replicate-level detection probability ranged between 0.56 and 0.88, and ignoring it would have underestimated elephant distribution by 2116 km² or 16%. We found that anthropogenic factors predominated over natural habitat attributes in determining elephant occupancy, underscoring the conservation need to regulate them. Human disturbances affected elephant habitat occupancy as well as site-level detectability. Rainfall is not an important limiting factor in this relatively humid bioclimate. Finally, we discuss cost-effective monitoring of Asian elephant populations and the specific spatial scales at which different population parameters can be estimated. We emphasize the need to model the observation and sampling processes that often obscure the ecological process of interest, in this case relationship between elephants to their habitat.</p></div

Comparison between the standard occupancy model [28] and the model using spatial replicates with potential auto-correlation of sign detections among them [54] used to generate estimates of dhole habitat occupancy at landscape scale (Western Ghats, India, 2006–2007) and habitat-use at reserve scale (Bandipur Tiger Reserve, India, 2012).

<p>*K =  number of parameters.</p

Results of comparisons to select models for estimating probability of detecting dhole signs <i>p_t</i> on 1-km long spatial replicates used in the field survey conducted at landscape scale in the Western Ghats landscape, India (2006–2007), under the constant global model for dhole occurrence [<i>Ψ_L</i> (<i>chital+sambar+livestock)</i>].

<p>*K = number of parameters.</p

Estimates of β coefficient values for different individual habitat covariates hypothesized to influence dhole habitat-use Ψ<i>_s</i> at reserve scale (Bandipur Tiger Reserve, India, 2012).

<p>These include model-averaged β estimates with unconditional standard errors.</p

Model selection results: Covariate effects in determining detectability p^t on 1-km-long spatial replicates, based on the Hines et al.

<p>(2010) modeling approach. No. of sites = 205. Please see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133233#pone.0133233.t001" target="_blank">Table 1</a> for descriptions of covariates.</p

Model selection results: Covariate effects in determining probability of elephant occupancy in our study landscape, based on the Hines et al.

<p>(2010) modeling approach. No. of sites = 205. Please see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133233#pone.0133233.t001" target="_blank">Table 1</a> for descriptions of covariates.</p

Estimated <i>β</i> parameter estimates for covariates determining elephant occupancy in our study landscape, from the 4 models with ΔAIC < 10.

<p>Point estimates followed by standard error (SE) in parentheses. No. of sites = 205. Please see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133233#pone.0133233.t001" target="_blank">Table 1</a> for descriptions of covariates.</p