PhD Theses (WII)
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Item Ecology of major Invasive Alien plant species (IAPs) across various habitats in Pakke Tiger Reserve, Arunachal Pradesh(Wildlife Institute of India, Dehradun, 2026) Singh, Huidrom Bablin; Adhikari, B.S.Proliferation of invasive alien plant species poses a significant threat to the structure and function of ecosystems, making this a critical area of focus within the scientific communities. These species cause extensive damage to the biodiversity, as they are capable of altering the ecosystems and outcompete the native biodiversity. Globally, their abundance has increased dramatically in forested and other natural areas due to rapid economic growths and anthropogenic activities. To counter this alarming situation, understanding the distribution pattern, climatic influences on phenophases and ecological impact on soil by invasive alien plant species is a priority. In northeast India, studies on invasive alien plant species diversity and their impacts are very limited, especially in Arunachal Pradesh. Therefore, the present study aims to determine the patterns of distribution, phenophases and physiochemical impacts by the dominant invasive alien plant species in five forest types (Assam Alluvial Plain Semi Evergreen Forest-AAPSEF, East Himalayan Mixed Coniferous Forest-EHMCF, East Himalayan Subtropical Wet Hill Forest-EHSTWH, Non-Forest-NF and Riverine Forest-RF) of Pakke Tiger Reserve, Arunachal Pradesh. The altitudinal range of Pakke Tiger Reserve is 150- 2050 m above the sea level (490 to 6725 feet), with an average annual rainfall of 2500 mm. The current study reveals a total of 43 invasive alien plant species in the study area. However, their species richness in five forest types was in declined trend with the increase of elevation. Across the forest types, AAPSEF (30%) display the maximum level of invasion and least incursion in EHSTWHF (16%) in the current study. Among the nine species selected for the study, Chromolaena odorata (L.) R.M.King & H.Rob. was found dominant and distributed extensively in all forest types, with highest relative density (51%) in EHSTWHF and relative abundance (10%) in NF. The entire selected species shows contagious distribution pattern (<0.5) in all forest types except for Urena lobata in NF displaying random distribution (0.025 - 0.5) in study area. Ageratum conyzoides L., Chromolaena odorata (L.) R.M.King & H.Rob. and Urena lobata L. are the species with extensive distribution in all forest types in comparison to other selected species showing their dominance over the native vegetation. Moreover, maximum area cover percentage was exhibit by Chromolaena odorata (L.) R.M.King & H.Rob. followed by Ageratum conyzoides L., Mikania micrantha Kunth and Urena lobata L. across the forest types in Pakke Tiger Reserve. Forest types such as AAPSEF, NF and RF display high level of disturbances while the EHMCF and EHSTWHF have fewer incursions by invasive alien plant species in the study area. Phenological pattern on the selected species shows that Bidens pilosa L. has the longest flowering phenophases while Chromolaena odorata (L.) R.M.King & H.Rob. has the maximum fruiting duration in EHSTWHF. For leaf fall and initiation, Urena lobata L. display the longest duration in RF. Moreover, coefficient of variation shows that most of the species display asynchronous phenophases across the forest types of Pakke Tiger Reserve. Repeated measures of ANOVA also display that Ageratum conyzoides L. display difference in flowering in NF and EHSTWHF while Chromolaena odorata (L.) R.M.King & H.Rob. leaf initiation show difference in EHMCF. Correlation and linear regression display influences of climatic parameters i.e., precipitation, relative humidity, minimum and maximum temperature to the selected species in the study area. CCA also indicates that precipitation, minimum and maximum temperatures directly influence the phenophases of the selected species. However, relative humidity influences the phenophases of the selected species when in cohesion with other climatic parameters. Ecological impact on native species by invasive alien plant species was determined by collecting the soil sample of the most dominant species i.e., Chromolaena odorata (L.) R.M.King & H.Rob. across the forest types in Pakke Tiger Reserve. The result shows that clay and copper contents were high in all invaded sites while soil pH, sand, boron and water holding capacity were significantly lower in invaded plots. Out of 16 soil variables, T-test reveals that AAPSEF and NF have variation in 13 variables while EHMCF, EHSTWHF and RF have difference in 12 variables. ANOVA between the invaded and uninvaded sites also indicates significant differences in Boron, iron, copper, nitrogen, water holding capacity, clay, silt and sand. Moreover, correlation shows eight of the variables display relation between them. Furthermore, PCA indicates that INNF soil properties were different from the remaining sites. The results indicate that Chromolaena odorata (L.) R.M.King & H.Rob. alter the soil properties of invaded areas by improving the fertility, making it ideal for the proliferation process in future scenarios.Item Species diversity and molecular study of bees (Bombus and Xylocopa) in Dehradun District, Uttarakhand, India(wildlife Institute of India, Dehradun, 2025) Abha PurohitPollinators are fundamental to the functioning of terrestrial ecosystems, as they facilitate the reproduction of a vast majority of flowering plants and thereby sustain biodiversity and ecological stability. Globally, an estimated 87.5% of flowering plants depend onanimal pollinators for successful reproduction (Ollerton et.al. 2011). In addition to their ecological role, pollinators, particularly bees, are indispensable for global agriculture. Approximately 75% of the world’s leading food crops rely on pollination to enhance both yield and quality (Klein et.al. 2007). Agricultural commodities such as fruits, vegetables, nuts, oilseeds, and spices are especially dependent on bee-mediated pollination. Beyond agricultural productivity, pollinators provide critical services that directly influence human nutrition. By increasing the diversity, availability, and quality of nutrient-rich foods, they indirectly contribute to balanced diets enriched with vitamins, antioxidants, and essential micronutrients (Eilers et.al.2011). Thus, pollinators not only underpin biodiversity but also strengthen food security and human well-being, highlighting their ecological, agricultural, and nutritional significance. 2. Research objectives The study aims to conduct a systematic survey of Bombus (bumblebees) and Xylocopa (carpenter bees) in the Dehradun district, focusing on their taxonomy, ecology, and seasonal distribution in different habitat zones. It also seeks for identification and characterization of their habitats, with emphasis on the availability of food plants that sustain high species diversity. Molecular tools, including DNA barcoding, was applied for accurate identification of collected specimens. Additionally, the research evaluated the impact of anthropogenic pressures and other environmental threats on the survival and diversity of these pollinator groups in the study area.Item Ecology of Seagrass Habitats and its associated macrobenthic invertebrates in Andaman islands, India(Wildlife Institute of India, Dehradun, 2024) Gole, Swapnali; Sivakumar, K.; Johnson, J.A.; Das, HimansuThe diversity, composition, and growth of species in plant communities are shaped mainly by their complex interactions with local environmental settings. Owing to the unprecedented global decline of seagrasses, it is crucial to understand in-situ ecological interactions for informing mitigation measures. However, several ecological aspects of seagrass ecosystems are under-studied in the tropical Indian waters, which fall in the highly productive Indo-Pacific seagrass distribution bioregion, offering many socio-ecological services. In this context, my study aimed to address the ecological gaps in India's unique seagrass biodiversity hotspot, the insular archipelago called the Andaman and Nicobar Islands (ANI). Objectives of the study were 1) To assess the spatial distribution patterns of seagrass habitats and associated macrobenthic invertebrates in the Andaman Islands, 2) To understand the seasonal variation in seagrass meadows and associated macrobenthic invertebrates, 3) To understand the structural diversity of seagrass meadows and its influence on associated macrobenthic invertebrates, and 4) To document the Traditional Ecological Knowledge on seagrass habitats. The field study was carried out between 2018 and 2022, with a significant sampling period between January and May, as it is the best feasible season for fieldwork in ANI. The spatial diversity, distribution, and growth of seagrasses in the present study were primarily governed by the water depth, habitat heterogeneity, substrate types, and availability. The study suggests that any alterations in the benthic habitat profile of these meadows are likely to affect the species distribution patterns and overall ecological services offeredItem Movement and space use pattern of Tigers in the Eastern Vidarbha landscape, Maharashtra, India(Wildlife Institute of India, Dehradun, 2024) Hussain, Zehidul; Habib, BilalMovement is a crucial ecological process that influences the survival, population dynamics, and evolution of animals. Animal movement patterns are diverse and are influenced by life stages, sex, age, and habitat requirements. The relationship between animal movement and conservation is complex, particularly due to human-induced environmental changes This study emphasises that various factors influence animal movement, including individual characteristics and external factors such as resource availability, distribution, competition, and predation. Animals adjust their space use based on seasonal changes in resource availability. Additionally, movement patterns and space use can be influenced by habitat disruption, forcing individuals to displace and establish new home ranges. Landscape features play a significant role in animal home ranges, with resource distribution determining the extent of the required area. Fragmentation of habitats and human activities can affect landscape connectivity, leading to isolation, reduced gene flow, and potential genetic bottlenecks or local extinctions. Thus, maintaining habitat connectivity is crucial for long-term survival of highly mobile species. The study highlights the need for comprehensive datasets and technological advancements, such as GPS tracking, to study animal movement and behaviour. It also emphasises the importance of studying dispersal patterns, as dispersed individuals often encounter humandominated landscapes and face increased vulnerability to anthropogenic effects. This study focused on quantifying movement patterns and space use across three life stages: predispersal, dispersal, and post-dispersal phases. The results revealed differences in space use within and outside protected areas, with individuals outside protected areas requiring larger territories. The study also identified seasonal variations in space use and movement patterns, with dispersed tigers exhibiting the highest space use. Land-use composition, landscape configuration, and anthropogenic disturbances influence the use of tiger space. These findings provide insights into the factors influencing tiger movement and space use in a human-dominated landscape. They highlighted the importance of maintaining habitat connectivity, reducing anthropogenic disturbances, and restoring suitable habitats outside protected areas to facilitate dispersal and ensure the long-term survival of tigers.