M Sc Dissertation(WII)

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Author: search.filters.author.Johnson, J.A.Subject: search.filters.subject.Habitat structure

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    The Effect of Land-use Changes on Odonate Assemblages in the Central Western Ghats
    (Wildlife Institute of India, Dehradun, 2024) Gowda, H.N. Rakshit; Gautam, Ritesh; Johnson, J.A.
    Odonata, the only apex insect predator in both terrestrial and aquatic life forms, are widely used as biological indicators of the health of aquatic ecosystems across the globe. The Riparian land uses such as commercial plantations negatively impact the Odonata assemblages, causing the homogenisation of habitats with generalist species and the extinction of specialist species. These land uses affect the riparian vegetation, habitat structure, and water quality parameters, which are crucial for Odonates to complete their life cycle. To understand the impact of commercial plantations on stream-associated Odonata assemblages at the sub-order level, three treatments comprising a combination of forest and areca plantations on either bank of streams were selected. The habitat variables, such as ambient temperature and canopy cover, along with stream parameters like flow and water quality parameters such as pH and water temperature, significantly influenced the Odonate assemblages. The sub-orders, Dragonflies and Damselflies, differed in their response to altered (Areca plantations and plantation-forest edge) and preserved sites (forested sites). These outcomes highlight the importance of the dependency of Odonata on particular sets of variables and the consideration of suborders of Odonata separately as indicator groups for the quality of aquatic ecosystems.
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    Effect of Habitat Structure on Odonate Species Richness in Streams of Kalakkand Mundanthurai Tiger Reserve in Tamil Nadu India
    (Wildlife Institute of India, Dehradun, 2013) Anilitty, A.S.; Uniyal, V.P.; Johnson, J.A.
    This study aimed at the responses of species richness of Odonates toward the habitat structure in Kalakkad Mundanthurai Tiger Reserve(KMTR) in Tamil Nadu, India. KMTR lies between latitudes 8° 25' to 8° 53' N and longitudes 77°10' to 77° 35' E with altitude ranging from 50 meters to 1868 meters. Intensive study areas were confined to three beats in Mundanthurai and Kalakkad ranges of KMTR namely Kodamadi, Kannikatti and Sengaltheri. We sampled vegetation and stream structural parameters along with altitude and time of sampling from three drainages, River Thamiraparni, River Servalar and River Kil Manimuthar. Only the second, third and fourth order streams were sampled. Thirty six belt transects were laid and each transect was walked trice. A total of thirty six species were found during the study period. Species richness was calculated using Software· Estimate S version 0.8 and used to do GLM(Generalized Linear Model) in Software R version 3.0.1. Altitude was found to be the most influencing factor on species richness. A second GLM was carried out for the altitude wise stratified data incorporating temporal replicates for each transect. Tree height and stream width were found to be the most influencing factors in this model with p values 0.00007 and 0.001 respectively.