Zoology

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Browsing Zoology by Advisor "Dr. Daya Ram Bhusal"

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    Species Composition and Floral Association of Bumblebees (Bombus spp.) in Chitwan Annapurna Landscape, Nepal
    (Institute of Science and Technology, T. U., 2024-06) Chandra Ghimire, Kishor Chandra; Dr. Daya Ram Bhusal
    Bumblebees (Bombus spp.) are important pollinators especially in high altitude flowering plants either natural or cultivated types, yet these bee communities are rapidly declining globally. Understanding abundance, species composition, distribution patterns, foraging plant species and responses to environmental factors is highly needed to understand the long term conservation of these vital pollinators in Nepal. This research work was aimed to investigate the species composition of Bombus species and their foraging association with flowering plants present along the Chitwan Annapuna Landscape (CHAL). The field survey was carried out in the most flowering seasons of (April to November) of 2018 and 2019. Three walking accessible transects (600 to 3500 m asl.) along the Kaligandaki (Mustang site), Marshyandi (Manang site), and Budhigandaki (Gorkha site) river basins were followed for the collection of bumblebees. The transects passed through different types habitat such as agricultural, home gardens, grasslands, and forests. For the sample collection, researcher moved at a slow pace along the transect, 20 meters right and left. The entire walking process included three times up and three times down from April to November for two consecutive years. The total field collection was performed 108 days (April-May, July-August, October –November). Whenever a bumblebee was encountered, stopped at that point and spent 30 minutes for extensive searching around the point. All possible foraging workers of Bombus species were captured before continuing the walking along the transect. The specimens were collected by entomological sweeping net for hovering bumblebees and directly picked by hand-vials method for those bumblebee which are foraged inside the flower. For the plant-bumblebee network analysis, six plots (plot size: 40m x 40m) were established along the three transects (2 plots in each transect). The upper point was established at the 2800 m where flowering plants were highly clustered during the survey time. Similarly, lower point was also selected on this basis of availability of flowering plants. The lower point was established at 1700 m asl. All possible foraging workers that visited to the flowers were collected within 60 minutes. During the collection, the number of bumblebee visitation in each flower was noted. A single plot was observed for 12 times(hrs) during study period. If bumblebees were in contact with the reproductive structure of a particular flower, it was considered as valid individual for the visitation count. The bumblebees and flowering plant categories (e.g. native type, non-native cultivated type, non-native naturalized type, and invasive type) was analysed by using bipartite network analysis where upper level of network was represented by 16 Bombus spp. and lower level was represented by categories of plants. In this study, a total of 16 Bombus spp. were identified during the whole study period. The relative abundance of Bombus species vary with altitude, habitat, transect sites and foraging plant types. The relative abundance of B. haemorrhoidalis was highest (n= 134, 20.29%), followed by B. festivus (n=129, 19.57%) and B. eximius (n=124, 18.84%). But, species like B. branickii, B. miniatus, B. novus, and B. pressus were the least abundant species with 1% relative abundance of each. The effects of elevation on bumblebee richness was found significant (R= 0.2876 p=0.0007) and the highest richness was recorded at the mid-elevation (2000-3000 m asl.), likely attributed to the increased availability of pollinator-dependent flowering plants within this range. The highest species diversity was recorded in forest habitat of Gorkha site (Shannon index H′= 2.18), followed by grassland habitat of Mustang site (Shannon index H′= 2.10). In overall, species diversity was comparatively higher in the habitats of Gorkha transect site than Manang and Mustang sites. This indicates that the distribution, diversity, and species composition of bumblebees in CHAL primarily influenced by the habitat mosaic, elevation gradient and categories of host plants. The climatic variation that created alteration in vegetation dynamics among the three study river basins from eastern to western sites associated to the community composition and richness of Bombus species in CHAL. On other hand, drier sites in western rather than eastern sites of Himalayan landscapes probably associated with rich vegetation dynamics that alinked with the higher diversity in Gorkha site (Budhigandki basins) rather than western sites of this study. Overall result attributed to the higher mean precipitation in eastern parts of Nepal that followed by higher richness of flowering plants creating more opportunity for growing wider species of pollinator-friendly flowering plants in eastern sites of this study. Furthermore, the site specificity of some Bombus species would associated to the presence of specific flowering plant in that sites. This study examined the foraging relation of Bombus species by performing linear mix effective model, cluster analysis and corresponding analysis(CA) of plant families, flower colours and categories (invasive and non-invasive) of plants. This study that the plant families and colour of flower were important biotic factors for the forging choice of particular Bombus species in this landscape. There was a significant variation in the foraging intensity of identified bumblebee species with native versus non-native categories of plants and it is distinct with lower and upper elevation points. While in the plant-bumblebee interactions network analysis, the highest interaction was indicated in the native flora rather than invasive types of plant categories. This attributes the plant specific foraging behavior of certain bumblebee (specialist) species (eg: B. asiaticus, B. novus) where as some species are more generalist (e.g: B. festivus, B. tunicatus, B. haemorrhoidalis). This suggests that some Bombus species have a broader dietary range and are capable of pollinating various types of plants, including both native and non-native species. In contrast, other Bombus species are more selective in their foraging habits, focusing their interactions on a single category of plants. These findings provide insights into the ecological roles and foraging behavior of different bee species in the different elevational gradients. Certain Bombus species are referred to as generalists, demonstrating the ability to engage with a diverse range of plant types and ecological settings, while others function as specialists, concentrating their interactions on a specific category of plants within a particular landform. These differences in foraging behavior can have implications for pollination dynamics and the ecological roles of these bee species in the Chitwan Annapurna landscape. भमरा विशेषत उच्च भेगमा पाइने प्राकृतिक र कृषि प्रजातिका वनस्पतिहका महत्वपूर्ण परागसेचक हुन् । यिनीहरूको संख्या विश्वबाट कम हुँदै गईरहेकोले, नेपालमा यिनीहरूको दीर्घकालिन संरक्षणको लागि प्रजाति प्रचुरता, विचरण गर्ने वनस्पति र वातावरणीय असरबारे अध्ययन आवश्यक छ । यो अध्ययनले चितवन अन्नपूर्ण परिदृश्यमा पाईने भमरा प्रजातिको संरचना, र फूल फुल्ने विरुवासँग तिनीहरूको सम्बन्धको बारेमा अनुसन्धान गरेको थियो । यसको लागि २०१८ र २०१९ को धेरै फूल फुल्ने समयमा समुन्द्र सतहबाट ६००–३५०० मी. को उचाइसम्म कालीगण्डकी (मुस्ताङ तर्फ), मरस्याङदी (मनाङ तर्फ) र बुढीगण्डकी (गोरखा तर्फ) का पहुचवाला वाटाहरू प्रयोग गरिएको थियो । ती वाटाहरू थरिथरिका वासस्थानको किसिम (कृषि क्षेत्र, घाँसे मैदान, जंगल र करेसाबारी) हुँदै गुज्रन्थ्यो । भमराहरू जम्मा गर्नको लागि अनुसन्धान कर्ता ती वाटाहरूमा विस्तारै हिडे त्यस अवधिमा जुन प्वाइन्टमा भमरा देखिन्छ त्यहाँ रोकिएर २० मी. दायाँ र २० मी. बायाँ गर्दै ३० मीनेट बिताएका थिए र भेटिएका भमराहरूलाई इन्टोमोलोजिकल जाली र हातको सहायताबाट छोपेर जम्मा गरिएको थियो । सम्पूर्ण हिड्ने प्रकृया ३ पटक माथि जाने र ३ पटक तल झर्ने गरी तय गरियो । वनस्पति र भमरा संजालको अध्ययनको लागि ३ वटा ट्रान्जेक्टमा २/२ वटाका दरले समुन्द्र सतहबाट १७०० मी. र २८०० मी. उचाइमा ४० मी.x ४० मी. का ६ वटा प्लटहरू तयार गरिएको थियो र अध्ययन अवधिमा प्रत्येक प्लटमा १२ पटक भ्रमण गरियो । एक भ्रमणमा प्रत्यक प्लटमा ६० मीनेट विताइयो । त्यस अवधिमा जुन भमराले प्रजनन अंगलाई छुन्छ, त्यसलाई आधिकारीक भ्रमण मानी गणना गरियो । भमराहरू र फुलफुल्ने वनस्पतिका वर्गहरूलाई नेटवर्क प्रकृया द्वारा विश्लेषण गरियो जसमा उच्च तहमा १६ वटा भमरा प्रजातिहरू र तल्लो तहमा विरुवाका वर्गहरू (स्वदेशि र आयतित)ले प्रतिनिधित्व गरेको थियो । यस अध्ययन अवधि भर १६ वटा भमरा प्रजातिहरू पहिचान गरिएको थियो । यस्तै भमराहरूको सापेक्षित समृद्धि उचाइ, वासस्थान र खाद्यन वनस्पतीको प्रकार अनुसार फरक पाइयो । वी. हेमोरोइडालीस को सापेक्षित समृद्धि सबैभन्दा बढी n= १३४,२0.२९% त्यस्तै दोस्रो र तेस्रोमा वी. फेस्टिभस n= १२९,१९.५७% र वी. एग्जीमस n= १२४,१८.८४% थियो तर वी. व्रानिस्को, वी. नोभस र वी. प्रेसस जस्ता प्रजातिको सापेक्षित समृद्धि n= ५% थियो । भमराहरूको समृद्धिमा उचाइले पारेको असर (R=0.२८७६, p=0.000७) महत्वपूर्ण थियो । सबैभन्दा धेरै प्रजातिको विविधता मध्य उचाई (२००० मीं देखी ३००० मी. सम्म रेकर्ड गरिएको थियो । यसको कारण त्यस क्षेत्रमा फूलहरूको उपलब्धता अत्याधिक रहनु हो । त्यस्तै, गोरखा क्षेत्रको जंगली आवासमा (H=२.१८) प्रजाति विविधता उच्च थियो त्यसपछि मुस्ताङको घॉसे मैदानमा (H=२.१०) रेकर्ड गरियो । समग्रमा मनाङ र मुस्ताङमा भन्दा गोरखा ट्रान्जेक्टमा प्रजातिहरूको विविधता उच्च थियो । चितवन अन्नपूर्ण परिदृश्यमा भमराहरूको वितरण, विविधता र प्रजाति संरचना मुख्यत, आवास मोजेक, अल्टीच्युडनल ग्रयाडिन्ट र होस्ट वनस्पतिको श्रेणीले प्रभाव पार्दछ । अध्ययन गरिएका तीन नदीहरूका वेसीनमा पूर्व देखि पश्चिम सम्मको वातावरणीय परिवर्तनले वनस्पतिका विविधतामा फरकपन ल्याएको छ यसले चितवन अन्नपूर्ण परिदृश्यमा पाइने भमरा प्रजातिको समुदाय संरचनामा महत्वपूर्ण सम्बन्ध राखेको छ । अर्को तर्फ पूर्वी भागमा बढी वर्षा हुने तर पश्चिमी भागमा कम वर्षा हुने भएकोले पश्चिमी भाग सुख्खा छ । त्यसकारण विभिन्न किसिमका परागसेचन मैत्रिक फूलहरूका प्रजातिहरू पूर्व क्षेत्र (बुढी गण्डकी क्षेत्रमा) बढी पाइन्छ त्यसकारण भमराका प्रजातिहरू पनि यो क्षेत्रमा बढी पाइयो । यो अध्ययनले भमरा प्रजातिहरूको फुलमा विचरण गर्ने सम्बन्धलाई करेस्पोन्डीङ एनलाइसीस लिनियर मीक्स मोडल र कल्सटर एनलाइसीस मार्फत वनस्पतीको फ्यामिली, फूलको रंग र वनस्पतिका वर्ग (स्वदेशी र आयतित) द्वारा मापन गरिएको थियो । यो अध्ययनले वनस्पतिका फ्यामिली र फूलको रंग निस्चित भमराहरूले फूलहरू रोज्ने महत्वपूर्ण जैविक कारण हुन् भन्ने देखाएको छ । भमरा जातिहरूको विचरण तिव्रता तल्लो र माथिल्लो उचाइका विन्दुहरूमा स्थानिय र आयतित वर्गका वनस्पतिहरूमा महत्वपूर्ण र निश्चित थियो । भमरा र वनस्पतिका वर्णहरूको संजालको विश्लेषण गर्दा स्थानिय वनस्पतिका वर्गहरूमा आयतित वनस्पतिका वर्गहरूमा भन्दा बढी भमराहरूको प्रतिक्रिया रहयो । यसले निश्चित भमरा प्रजातिहरू (जस्तै, वि. एसियाटिकस, वि. हेमोरोइडालिस, वि. टुनिक्याटस, वि. एग्जीमस), का भमराहरू अधिक सामान्य हुन्छन् यस्ता जातिहरूको विसाल पोषणीय क्षेत्र हुन्छ र यिनीहरू विभिन्न थरीका वनस्पति हरू स्थानिय, आयतित दुवै विचरण गर्न सक्छन् । यो खोजले विभिन्न इलेभेसन ग्रयाडिन्टमा माहुरी प्रजातिहरूको पारिस्थीतीक भूमिका र विचरण प्रणाली माथि प्रकाश पारेको छ । यसले केही भमरा जातिहरू सामान्यपूर्ण हुने र विभिन्न प्रकारका वनस्पति र पारिस्थीतीक वनावटमा घुलमील गर्न सक्छन् । केही भमरा प्रजातिहरू विशेषज्ञ हुन्छन् र आफ्नो अन्तरकृयालाई विशेष भू–संरचना र विशिष्ट प्रकारका वनस्पतिका वर्गहरूमा केन्द्रित गरेको हुन्छन् । भमरा प्रजातिहरूको फूलको विचरणको फरक पनाले परागसेचन गर्ने बानीमा प्रभाव पार्दछ त्यसकारण चितवन अन्नपूर्ण परिदृश्यको पर्यावरणमा यिनीहरूको योगदान महत्वपूर्ण रहेको छ ।