Search bioRxiv⌕ Search

Biology subjects

Naniwadekar, R.

Publications and source records attributed to Naniwadekar, R..

28 records · Page 2Linked to original sources
bioRxiv2024

Is the population of the Critically Endangered White-bellied Heron in Namdapha Tiger Reserve, India, declining?

The Critically Endangered White-bellied Heron Ardea insignis is a large-bodied, range-restricted, piscivorous bird found in the Himalayan mountains. With fewer than 60 individuals remaining globally, regular monitoring efforts are required to understand the conservation status of this rare species better. Here, we present the results of river surveys from 2017 and 2023-24 for the White-bellied Heron in an important protected area, the Namdapha Tiger Reserve, in Arunachal Pradesh. The encounter rate in 2017 was 0.55 herons per km, however; we did not detect the bird during intensive river sampling in the same stretches in 2023-24. This area within the reserve was once a stronghold for the species and they currently appear to be declining or locally extinct. Given the declines within this Protected Area, the drivers for the same need to be determined. While repeated monitoring of rivers has helped reveal this decline, locating and conserving stretches of river utilised by the remaining individuals away from the core zone is now critical. [Supplementary material for this article can be found at https://doi.org/xxx]

ecology↗
bioRxiv2024

Deciduous forests hold conservation value for birds within South Andaman Island, India

Greater diversity of habitats on islands is often correlated with higher species richness (including endemic and threatened taxa), implying the need to understand species-habitat associations. Such habitat associations would also point towards the role of abiotic filtering and competition in structuring species communities, necessitating the examination of the role of species traits and phylogenetic relationships in intra-island community organisation, an aspect poorly examined in literature. We investigated the composition and structuring of forest bird communities in closely co-occurring evergreen and deciduous forests within South Andaman Island (Indian Ocean), wherein the importance of deciduous forests for birds is undervalued. We sampled 27 transects over two years and compared bird species composition and diversity across the two habitats. We examined species-specific associations with habitat (forest) type, basal area, and distance from human settlements, and tested if these responses were explained by species functional traits and tested for phylogenetic niche conservatism after factoring the effects of environmental predictors. Bird species compositions were markedly distinct across the two habitat types, with deciduous forests having greater taxonomic, but not functional or phylogenetic, diversity of forest birds. The distribution of forest birds, including several endemic and threatened species within the island was largely explained by habitat type (with 39% of the bird species analysed showing higher occurrence probabilities in deciduous forests), followed by distance from human settlements and basal area. We did not find evidence of species traits or phylogenetic relationships mediating these habitat preferences, perhaps due to a relatively impoverished species pool, as is typical on islands. Nevertheless, our results underscore the value of deciduous forests in harbouring high islandic species diversity, and being the preferred habitat of several endemic and threatened bird species. Given the historic focus on evergreen forests and the increasing anthropogenic pressure on the forests of the Andamans, we highlight the critical need to include the rapidly diminishing deciduous forests in existing conservation plans.

ecology↗
bioRxiv2024

Chronic disturbance of moist tropical forests favours deciduous over evergreen tree communities across a climate gradient in the Western Ghats

It is well established that climatic factors such as water stress and chronic anthropogenic disturbances such as biomass extraction influence tropical forest tree community structure, richness and composition. However, while the standalone effects of these two drivers on plant communities are well-studied, their interactive effects are not. Moist tropical forests in Indias Western Ghats face a dual threat from increasingly erratic precipitation (and consequent water stress), and an intensifying anthropogenic footprint. Here, we sampled 120 tree plots (0.05 ha each) across forests with varying histories of biomass extraction and a gradient in climate water deficit (CWD, a proxy for water stress) within a 15,000 km2 landscape in the northern Western Ghats and examined whether and how disturbance history modulates relationships of tree community structure and composition with climate. As expected, tree species richness increased with decreasing water stress in less- and historically-disturbed forests but remained low in repeatedly-disturbed forests. The increase in evergreen species richness with decreasing water stress was far slower in repeatedly-disturbed forests than other categories, and the relative abundance of evergreens in the repeatedly-disturbed forests (25%) was half that in less-disturbed forests (50%) of comparable water stress in the driest parts. Overall, we show that disturbance can amplify threats from climate change to wet forest-associated evergreen tree species, many of which are threatened, while benefiting more widely distributed dry forest-associated deciduous species. In the northern Western Ghats, where much of the remaining forest cover is disturbed and dominated by deciduous tree species, the persistence of evergreen tree flora hinges on protecting existing evergreen forest patches from future disturbances and restoring locally appropriate evergreen species in secondary forests.

ecology↗
bioRxiv2023

Orchards and paddy differentially impact rock outcrop amphibians: Insights from community- and species-level responses

With agricultural demands increasing globally, determining the nature of impacts of different forms of agriculture on biodiversity, especially for threatened vertebrates and habitats, is critical to inform land management. We determined the impacts of converting rock outcrops (a habitat more threatened than rainforests) to orchards and paddy on anurans in the Western Ghats biodiversity hotspot. We sampled 50 belt transects four times across four sites during the rainy season and recorded information on amphibians and their microhabitats. We determined community-level responses using Hill numbers, beta-diversity measures, and non-metric multidimensional scaling, and species-level responses using joint species distribution modelling. Converting rock outcrops to paddy and orchards significantly altered microhabitat availability. Conversion to paddy mostly had community-level impacts, i.e., lowered species richness and more nested communities, whereas conversion to orchards mostly had species-level impacts, i.e., lowered species occurrence, highlighting the differential impacts of different forms of agriculture on amphibians and the need to determine impacts of land-use change on communities and species concurrently. We show that large rock pools are critical microhabitats for anurans as they serve as a refuge and protect anurans from desiccation during dry spells, which may be prolonged by climate change. Since rock outcrop habitats in low elevations are rapidly being converted to orchards, efforts are needed to conserve them in partnership with local communities, the custodians of these habitats. Our findings demonstrate that different forms of agriculture can have divergent impacts on biodiversity, and determining their impacts may require assessments at multiple scales, from species to communities.

ecology↗
bioRxiv2023

Conservation value of low-elevation forests for birds in agroforestry-dominated landscapes in a biodiversity hotspot

O_LIProtected areas (PAs) and multi-use landscapes beyond PAs play important and complementary roles in conserving global biodiversity. Across the tropical forest biome, remnant forests and agroforestry plantations in mixed-use landscapes often have high taxonomic diversity, but their ability to sustain functionally and phylogenetically diverse assemblages and retain conservation-priority species is unclear. Additionally, our understanding of impacts of land-use change across species, function and communities is poor. C_LIO_LIIn Indias Western Ghats (WG) biodiversity hotspot, like in many other tropical regions, PAs cover just 12% of the land and are concentrated in higher elevations. Here, in an approximately 15,000 km2 landscape in the northern WG, we compared bird communities across six land-use categories: state-owned high-elevation PAs and low-elevation Reserved Forests beyond PAs, and privately-owned periodically clear-felled low-elevation forests and three types of low-elevation agroforestry plantations (cashew, mango, and rubber). C_LIO_LIWe sampled 184 line transects totalling 137.5 km across habitats, compared taxonomic, functional, and phylogenetic diversity metrics and used joint species distribution models to test for species-trait-habitat associations. C_LIO_LIForests in general and lowland forests in particular had higher taxonomic, functional and phylogenetic diversity, and higher occurrence probabilities of evergreen forest-affiliated, conservation-priority, and frugivores than agroforestry plantations. The ranking of land-use types varied across indicators, with rubber ranking higher than cashew and mango for functional and phylogenetic diversity but lower in species occurrence probabilities. C_LIO_LISynthesis and Applications: Our findings underscore the irreplaceability of less-disturbed forests for birds in mixed-use landscapes, especially when considering multiple dimensions of biodiversity, habitat specialists, and conservation-priority species. We advocate the simultaneous examination at multiple levels (community, species and traits) to determine the impacts of land-use change as divergent information of conservation importance is gleaned from each level. Reserved and private forests of low elevations of the Northern Western Ghats are critical for avian conservation, given that they harbour significant diversity, and the absence of representative PAs in the region. Given the vulnerability of these low-elevation forests to conversion for non-forestry activities and overexploitation for fuelwood, there is a need to develop viable models of partnership with landowners in these multi-use landscapes for ecological restoration of degraded forests. C_LI

ecology↗
bioRxiv2023

Frugivory and seed predation of fishtail palm (Caryota mitis Lour.) on the remote oceanic island of Narcondam, India

Oceanic islands, due to their evolutionary history and isolation, hold a disproportionately high proportion of endemic species. However, their evolutionary history also makes them vulnerable to extinctions, with most known extinctions occurring on islands. Plant-animal interactions are particularly important on islands, as island systems generally have low redundancy and are more vulnerable to disruption either via extinction or by invasive species. Here, we examined the fruit removal and seed predation of a keystone palm, Caryota mitis, on the remote oceanic island of Narcondam. The island endemic Narcondam hornbill (Rhyticeros narcondami), was the sole seed disperser of the Caryota mitis (90 hours; N = 15 trees), indicating a lack of redundancy in seed dispersal of the palm on this island. While the invasive rodent, Rattus cf. tiomanicus was the sole predator of the Caryota mitis seeds in the forest (N = 15 individual fruiting palms, 416 trap nights). Overall, 17.1% of the seeds placed (N = 375 seeds) were removed. Seeds placed under and away from the canopy, and at different densities (2 plots with 10 seeds each; 1 plot with 5 seeds, respectively), showed similar removal rates. This is indicative of ambient seed predation and the lack of safe sites for the regeneration of Caryota mitis, with potential deleterious effects on the subsequent stages of the "seed dispersal cycle". Here, from a data deficient site, we provide baseline information on the plant-frugivore interaction of a keystone palm and the potential impacts by an invasive rodent.

ecology↗
bioRxiv2023

Between a rock and a hard place: Effects of land-use change on rock-dwelling animals of lateritic plateaus in the northern Western Ghats

Open natural ecosystems like lateritic plateaus, are undergoing rapid transformation with very poor understanding of these impacts on the threatened and endemic biodiversity. The unprotected, low-elevation lateritic plateaus of the northern Western Ghats are case to the point, as they have high endemicity but remain unprotected under Indian law. We aimed to understand the impact of the conversion of the natural lateritic plateaus to agroforestry and paddy cultivation on biodiversity. We compared the prevalence of two species of endemic herpetofauna of the northern Western Ghats (Gegeneophis seschachari and Hemidactylus albofasciatus) and a widespread snake (Echis carinatus) and the composition of other rock-dwelling animals across 12 undisturbed plateau sites and 10 sites each in agroforestry plantations and abandoned paddies on plateaus using time-constrained searches. We had 5738 encounters with 38 different animal species/groups. We found that the abundance of large rocks, which were the most-preferred size class of rocks by animals, was higher in abandoned paddy compared to plateaus and orchards. However, the prevalence of H. albofasciatus and E. carinatus was highest on undisturbed plateaus. Contrastingly, the prevalence of G. seshachari was significantly higher in abandoned paddy than undisturbed plateau or orchards. Non-metric multi-dimensional analysis showed that the assemblage of rock-dwelling fauna differed significantly across the three land-use types. Despite being adapted to persist in extremely variable climates on lateritic plateaus, we find that multiple species/groups are vulnerable to land-use change. However, G. seshachari and a few other taxa appear to benefit from certain kinds of land-use change, highlighting the context-specificity in species responses. While multiple studies have determined the impacts of forest conversion to other land-uses, this is one of the first studies to determine the impacts of the conversion of rocky outcrops, thereby highlighting the conservation value of habitats that are often classified as wastelands.

ecology↗
bioRxiv2020

Patterns of roost site use by Asian hornbills and implications for seed dispersal

Animals spend a significant amount of time roosting. Therefore, understanding roosting patterns and the processes that influence roosting behaviour and roost site choice is essential. Hornbills exhibit interesting roosting patterns with some species roosting communally in large flocks. They are important seed dispersers and patterns of roost site use can have a significant influence on seed dispersal distributions and thereby on plant recruitment. We documented roost site use by four Great Hornbills (Buceros bicornis) and one Wreathed Hornbill (Rhyticeros undulatus) at a site in north-east India using GPS telemetry. We examined the influence of riverine habitats, nests and foraging range on roost selection. We determined the proportion of seeds that hornbills disperse at roosts and the dispersal distances of seeds dispersed at roosts from the source trees. Through telemetry, we found that roosts of Great Hornbills were generally in forested habitats. Our telemetry data showed that Wreathed Hornbill roosts were close to the river. These results were corroborated by observational data from roost sites where we had regular detections of relatively large flocks of Wreathed Hornbills and occasionally Great Hornbills. The roost sites were not close to the nest sites and were generally within the 95% kernel density diurnal activity ranges. Hornbills dispersed a small proportion of seeds at roost sites. Seeds dispersed at roost sites had almost twice the dispersal distances compared to those dispersed at non-roost sites. This study highlights variation in roost site pattern across individual hornbills and its implications for seed dispersal.

ecology↗
bioRxiv2020

The critical ecological role of an endemic, large-bodied frugivore on a small tropical island

Endozoochory, a mutualistic interaction between plants and frugivores, is one of the key processes responsible for maintenance of tropical biodiversity. Islands, which have a smaller subset of plants and frugivores when compared with mainland communities, offer an interesting setting to understand the organization of plant-frugivore communities vis-a-vis the mainland sites. We examined the relative influence of functional traits and phylogenetic relationships on the plant-seed disperser interactions on an island and a mainland site. The island site allowed us to investigate the organization of the plant-seed disperser community in the natural absence of key frugivore groups (bulbuls and barbets) of Asian tropics. The endemic Narcondam Hornbill, was the most abundant frugivore on the island and played a central role in the community. Species strength, a measure of relevance of frugivores for plants, of frugivores was positively associated with their abundance. Among plants, figs had the highest species strength and played a central role in the community. Island-mainland comparison revealed that the island plant-seed disperser community was more asymmetric, connected and nested as compared to the mainland community. Neither phylogenetic relationships or functional traits (after controlling for phylogenetic relationships) were able to explain the patterns of interactions between plants and frugivores on the island or the mainland pointing towards the diffused nature of plant-frugivore interactions. The diffused nature is a likely consequence of plasticity in foraging behavior and trait convergence that contribute to governing the interactions between plants and frugivores.

ecology↗