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Effect of habitat alteration on canopy bird and small mammal communities in the wet evergreen forests of the Western Ghats
Get PDFThe forest canopy, often referred to as the eighth continent has been looked upon in awe since the dawn of mankind. The tropical rainforest canopy is a highly variable environment that provides structural and functional niches for several living organisms. Much of the diversity in tropical forests is found in the canopies and many interactions between organisms also occur in the canopies. Canopies are one of the least studied of terrestrial habitats. In the South Asian region, canopy studies have been few and far between. Canopy science in India is in its infancy. Pioneering work in this field in India has been done by researchers from ATREE on pollination and frugivory at the Kalakad- Mundanthurai Tiger Reserve (KMTR). Apart from these studies, there is very little work on canopies that exists from this region. In KMTR, this thesis concentrates on the mid-elevation wet evergreen forests of Kakachi and Kodayar. The forest canopy here is considered structurally complex and an ecologically
critical system of the forest. These forests have a history of human exploitation, with the establishment of tea estates in 1928. Selective felling and clear felling for timber and cardamom plantations has also modified the habitat. This has created a variegated mosaic of natural and managed ecosystems.
This thesis aims to study the bird and small mammal communities across a habitat mosaic of unlogged, selection-felled and clear-felled forests. With secondary forests becoming dominant in tropical landscapes, it is important to ask questions such as, how forest communities are vertically stratified and its role in such modified habitats. More specifically, I explored the effects of disturbance and change in habitat structure on these communities by 1) identifying the lacunae that exists in community ecological studies related to forest
canopies, 2) By devising and testing effective sampling protocols for the two target taxa, 3) Evaluating the change in community structure and vertical stratification of bird community and small mammal communities across the habitat. The thesis has five chapters with the last
one being a synthesis of the findings.
The concept of ‘canopy’ birds and small mammals is examined and the state of the art in canopy research is discussed. I ask if canopies host unique communities of birds and small mammals. I explore the advantages and problems of studying arboreal organisms and possible solutions. The pros and cons of canopy sampling with the development of new techniques such as canopy cranes and potential solutions using examples from my work are illustrated. I then introduce the premise and the hypothesis that is the theoretical underpinning of the thesis along with the specific objectives.
Methods for studying canopy organisms are infrastructure intensive and are plagued with problems of replication. To circumvent these problems I have used canopy platforms and trapping in conjunction with traditional ground based methods to illustrate the importance of canopy sampling for a well-studied taxa- Aves as well as for a poorly studied taxa - Rodents.
My results indicate that canopy sampling is essential for these taxa in multi-layered habitats.
These methods have shown to maximize habitat coverage by repeated sampling of the understorey and canopy and are indispensable for the understanding of ecological processes.
I go on to explore variations in local bird community structure along a disturbance gradient, using traditional ground-based sampling in conjunction with canopy sampling. Results indicate a reduction in species richness and abundance in Clear-felled habitats. Guilds too are affected by the change in habitat structure. This is termed as “guild compression” and is attributed to the simplification of the habitat.
Patterns of vertical stratification and community composition of small mammals were analysed. Community composition and relative abundance of species across the habitat are similar; additionally there is a general reduction in the number of species, and in abundance
in the upper layers. Results indicate that structural change in habitat may alter the community composition of different forest layers but they do not seem to alter greatly specific patterns of vertical habitat utilization.
A synthesis of the findings is presented with a perspective on current canopy based research, and the autecology of the species is explored. I also highlight the shortcomings of the study and possible improvements are suggested. The conservation implications of such studies and canopy sampling in general are elucidated. The conservation of canopy vertebrate communities and importance of such studies in the South Asian context is also discussed
Patterns of Insect Abundance and Distribution in Urban Domestic Gardens in Bangalore, India
Get PDFDomestic gardens may play a vital role in supporting urban insect biodiversity, despite their small size. This paper assesses the abundance, diversity and distribution of insects in urban domestic gardens in the tropics, through a study in the rapidly expanding Indian city of Bangalore. Fifty domestic gardens were studied using a combination of light traps and pitfall traps. We recorded a large number of insects, 2,185 insects from 10 orders, of which ants, bugs, beetles and flies were the most common. We found 25 species of trees (from 160 individuals) and 117 species of herbs and shrubs in the 50 sampled domestic gardens. The number of insect orders encountered was significantly related to the number of tree and herb/shrub species. Garden management practices also influenced the abundance and richness of insect orders. Thus, greater numbers of insects were observed in gardens with a greater proportion of bare soil relative to grass area and with less intensive weeding practices. More insect orders were encountered in gardens with a composting pit. Insect numbers were significantly reduced in gardens subjected to pesticide application. Most residents avoided application of pesticides and herbicides, citing health concerns
Dissemination of Metarhizium anisopliae infection among the population of Odontotermes obesus (Isoptera: Termitidae) by augmenting the fungal conidia with attractants
No full textLong-term biocontrol strategies for termite management have limited success as the behavioral response exhibited by termites in the presence of entomopathogenic fungi was different. To minimize these responses, a study was conducted to attract the termites towards the treated area by augmenting fungal conidia with a mixture of attractants such as sugarcane bagasse, sawdust and cardboard powder. In laboratory experiments, mortality due to the horizontal transmission of Metarhizium anisopliae infection among Odontotermes obesus workers and soldiers was 50 to 98% and 16 to 78% for the five isolates tested. The foraging activity of workers and soldiers increased from 23 to 58% for IWST-Ma13 when conidia were mixed with attractants. In a field study, the weight loss of stakes treated with conidial attractant decreased to 10.9 g compared to dry conidial
treatments (19.3 g) for IWST-Ma13 after five months. Similarly, the width of mud galleries covering the tree
bark was reduced when treated with conidial baits and gunny bags containing conidial attractant. In treated
mounds, as the Acoustic emission signal voltage decreased from the threshold voltage level, the relative magnitude
signal (RMS) remains low after five months of treatments with that of the control. From this study it was observed that the mixing of conidia with attractants could augment the dissemination potential of fungal infection among the termites. By adapting attractant based Metarhizium baits and dusting of conidial attractant mixture inside mounds may augment the dissemination potential in epizootic transmission of fungal infection
The groundwater recharge response and hydrologic services of tropical humid forest ecosystems to use and reforestation: Support for the ‘‘infiltration-evapotranspiration trade-off hypothesis’’
No full textThe hydrologic effects of forest use and reforestation of degraded lands in the humid tropics has implications for local and regional hydrologic services but such issues have been relatively less studied when compared to the impacts of forest conversion. In particular, the “infiltration-evapotranspiration trade-off” hypothesis which predicts a net gain or loss to baseflow and dry-season flow under both, forest degradation or reforestation depending on conditions has not been tested adequately. In the Western Ghats of India, we examined the hydrologic responses and groundwater recharge and hydrologic services linked with three ecosystems, (1) remnant tropical evergreen forest (NF), (2) heavily-used former evergreen forest which now has been converted to tree savanna, known as degraded forest(DF), and (3) exotic Acacia plantations (AC, Acacia auriculiformis) on degraded former forest land. Instrumented catchments ranging from 7 to 23 ha representing these three land-covers (3 NF, 4 AC and 4 DF, in total 11 basins), were established and maintained between 2003 and 2005 at three sites in two geomorphological zones, Coastal and Up-Ghat (Malnaad). Four larger (1–2 km2) catchments downstream of the head-water catchments in the Malnaad with varying proportions of different land-cover and providing irrigation water for areca-nut and paddy rice were also measured for post-monsoon baseflow. Daily hydrological and climate data was available at all the sites. In addition, 36 min data was available at the Coastal site for 41 days as part of the opening phase of the summer monsoon, June–July 2005.Low potential and actual evapotranspiration rates during the monsoon that are similar across all land-cover ensures that the main control on the extent of groundwater recharge during the south-west monsoon is the proportion of rainfall that is converted into quick flow rather than differences in evapotranspiration between the different land cover types. The Flow duration curves demonstrated a higher frequency and longer duration of low flows under NF when compared to the other more disturbed land covers in both the Coastal and Malnaad basins. Groundwater recharge estimated using water balance during the wet-season in the Coastal basins under NF, AC and DF was estimated to be 50%, 46% and 35% respectively and in the Malnaad it was 61%, 55% and 36% respectively. Soil Water Infiltration and Movement (SWIM) based recharge estimates also support the pattern (46% in NF; 39% in AC and 14% in DF). Furey–Gupta filter based estimates associated with the Coastal basins also suggest similar groundwater recharge values and trends across the respective land-covers: 69% in NF, 49% in AC, and 42% in DF. Soil water potential profiles using zero flux plane methods suggest that during the dry-season, natural forests depend on deep soil moisture and groundwater. Catchments with higher proportion of forest cover upstream were observed to sustain flow longer into the dry-season. These hydrologic responses provide some support towards the “infiltration-evapotranspiration trade-off” hypothesis in which differences in infiltration between land-cover rather than evapotranspiration determines the differences in groundwater recharge, low flows and dry-season flow. Groundwater recharge is the most temporally stable under natural forest, although substantial recharge occurs under all three ecosystems, which helps to sustain dry-season flow downstream in higher order streams that sustain local communities and agro-ecosystems. In addition to spatial scale effects, greater attention also needs to be given to the role of hydrogeology within the context of the above hypothesis and its implications for hydrologic services
First detailed survey of waterbirds in Tirunelveli and Tuticorin districts, Tamil Nadu, India
Get PDFThe semi-arid districts of Tirunelveli and Tuticorin in the southern Indian state of Tamil Nadu consist of numerous wetlands in the form of irrigation tanks, interconnected by an ancient network of canals, and fed by the rivers originating from the Western Ghats. While these irrigation tanks have socio-economic and cultural significance, very little is known of their ecological importance. These tanks have the potential to harbor good populations of resident and wintering waterbirds but no studies have been done to confirm this. A survey was carried out in 230 irrigation tanks of various sizes in the two districts from November 2008 to January 2011. A total of 83 waterbird species were recorded. Indian Pond Heron Ardeola grayii occurred in most of the surveyed tanks. Large concentrations of wintering waterfowl such as Eurasian Wigeon Anas penelope, Northern Pintail Anas acuta, Garganey Anas querquedula were recorded in tanks closer to the coast. Based on our survey, six sites with large waterbird concentrations have been identified, one of which is Vagaikulam, an active heronry currently under threat from tree felling. These sites along with associated wetlands are important for the long term conservation of waterbirds in the region
New plant sources of the anti-cancer alkaloid, camptothecine from the Icacinaceae taxa, India
No full textIn this study, the production of camptothecine and its derivatives, in thirteen species of the family Icacinaceae, namely, Apodytes dimidiata, Codiocarpus andamanicus, Gomphandra comosa, Gomphandra coriacea, Gomphandra polymorpha, Gomphandra tetrandra, Iodes cirrhosa, Iodes hookeriana, Miquelia dentata, Miquelia kleinii, Natsiatum herpeticum, Pyrenacantha volubilis and Sarcostigma kleinii is reported. Seeds of M. dentata were found to produce the highest content of camptothecine (1.0–1.4% by dry weight of seeds). Full scan LC–MS and ESI-MS/MS analysis of M. dentata revealed, besides camptothecine, a number of other derivatives, namely, 10-hydroxycamptothecine, 9-methoxycamptothecine, 20-deoxycamptothecine. Crude extract preparations of the seeds of M. dentata were effective against a breast cancer cell line (IC50 = 3.82 g/ml for MDA MB273 cell lines) and two ovarian cancer cell lines (IC50 = 2.8 g/ml for NCI/ADR-RES and 4.5 g/ml for SKOV). These results are the first reports of camptothecine and its derivatives in these species and offer rich alternative plant sources for the anticancer compound, camptothecine
Top-dogs and under-dogs: competition between dogs and sympatric carnivores
No full textIn many natural and semi-natural systems worldwide, dogs ( Canis familiaris ) are an integral part of the carnivore community (Gompper, Chapter 1 ). Until recently, the role of dogs as mid-sized members of the carnivore guild, and how they shape the structure of native carnivore communities, has garnered little attention. Of late, however, a suite of studies across the world has highlighted several key aspects of the competitive dynamics that occur between dogs and sympatric members of the carnivore community ( Table 3.1 ). These studies have demonstrated that dogs often compete with native carnivores for food, and that smaller carnivores may react to dogs as they would to any other midsized predator: with increased vigilance, lowered
food intake, avoidance of dog-dominated habitat types, or complete spatial separation. These studies have also shown that the types and intensity of interactions
between dogs and subordinate predators are likely infl uenced by several factors, including, but not limited to
Moving to stay in place: behavioral mechanisms for coexistence of African large carnivores
No full textMost ecosystems have multiple predator species that not only compete for shared prey, but also pose direct threats to each other. These intraguild interactions are key drivers of carnivore community structure, with ecosystem-wide cascading effects. Yet, behavioral mechanisms for coexistence of multiple carnivore species remain poorly understood. The challenges of studying large, free-ranging carnivores have resulted in mainly
coarse-scale examination of behavioral strategies without information about all interacting competitors. We overcame some of these challenges by examining the concurrent fine-scale movement decisions of almost all individuals of four large mammalian carnivore species in a closed terrestrial system. We found that the intensity of intraguild interactions did not follow a simple hierarchical allometric pattern, because spatial and behavioral tactics of subordinate species changed with threat and resource levels across seasons. Lions (Panthera leo) were generally unrestricted and anchored themselves in areas rich in not only their principal prey, but also, during periods of resource limitation (dry season), rich in the main prey for other carnivores. Because of this, the greatest cost (potential intraguild predation) for subordinate carnivores was spatially coupled with the highest potential benefit of resource acquisition (prey-rich areas), especially in the dry season. Leopard (P. pardus) and cheetah (Acinonyx
jubatus) overlapped with the home range of lions but minimized their risk using fine-scaled avoidance behaviors and restricted resource acquisition tactics. The cost of intraguild competition was most apparent for cheetahs, especially during the wet season, as areas with
energetically rewarding large prey (wildebeest) were avoided when they overlapped highly with the activity areas of lions. Contrary to expectation, the smallest species (African wild dog, Lycaon pictus) did not avoid only lions, but also used multiple tactics to minimize
encountering all other competitors. Intraguild competition thus forced wild dogs into areas with the lowest resource availability year round. Coexistence of multiple carnivore species has typically been explained by dietary niche separation, but our multi-scaled movement results suggest that differences in resource acquisition may instead be a consequence of avoiding
intraguild competition. We generate a more realistic representation of hierarchical behavioral interactions that may ultimately drive spatially explicit trophic structures of multi-predator communities
Isolation of endophytic bacteria producing the anti-cancer alkaloid camptothecine from Miquelia dentata Bedd. (Icacinaceae)
No full textCamptothecine (CPT), a quinoline alkaloid, is a potent inhibitor of eukaryotic topoisomerase I. Because of
this activity, several semi-synthetic derivatives of CPT are in clinical use against ovarian and small lung
cancers. Together with its derivatives, CPT is the third largest anti-cancer drug in the world market. CPT
is produced by several plant species belonging to the Asterid clade. In the recent past, several studies
have reported the production of CPT by endophytic fungal associates of some of these plant species. In this paper, we report the production of CPT by endophytic bacteria isolated from Miquelia dentata Bedd. (Icacinaceae). Besides CPT, the bacteria also produced 9-methoxy CPT (9-MeO-CPT), in culture, independent of the host tissue. The chemical nature of CPT and 9-MeO-CPT was determined by LC–MS and ESI-MS/MS analysis, and was shown to be similar to that produced by the host tissue. One of the bacterial isolates examined, showed indications of attenuation of CPT production through sub-culture. This is the first report of production of CPT by endophytic bacteria. The identity of the bacteria was ascertained by Gram staining and 16s rRNA sequencing. We discuss the possible mechanisms that might be involved in the synthesis of CPT by endophytic bacteria