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Gautam, H.

Publications and source records attributed to Gautam, H..

9 recordsLinked to original sources
bioRxiv2026

Megaherbivore mortality risk from temperature extremes is buffered by vegetation productivity but amplified by rainfall

Demographic risks from climate change remain poorly understood for megaherbivore species which face unique challenges because their large food requirements impose strong bottom-up limitation while their small surface-area-to-volume ratio limits heat dissipation. Here, we test how megaherbivore mortality is shaped by the concurrent effects of temperature and rainfall along with vegetation productivity, a potentially critical modifier of climate effects. By analysing four decades of monthly mortality records from 4,457 semi-captive Asian elephants across Myanmar, we identify multiple environmental pathways regulating megaherbivore mortality. Elephant mortality increased at extreme hot and cold temperatures in regions with low annual vegetation productivity, whereas high vegetation productivity buffered against such U-shaped effects of temperature. Furthermore, high rainfall amplified the negative impacts of extreme heat, underlining risks arising from the joint effects of heat and humidity. Seasonal declines in vegetation productivity did not explain the elevated mortality at temperature extremes. Together, our findings show that megaherbivores face elevated risks from global warming, but such risks strongly depend on vegetation productivity and humidity, highlighting multiple pathways through which climate change can shape the dynamics of megaherbivore populations.

ecology↗
bioRxiv2025

Bottom-up effects of a megaherbivore alter plant growth and competition regimes, promoting vegetation heterogeneity

O_LIMegaherbivores are known to strongly influence multiple ecological processes, but their bottom-up impacts on vegetation via nutrient redistribution remain poorly understood, particularly in mesic ecosystems. Here, we investigated how woody plant communities are influenced by large nutrient inputs in the form of dung deposited by Asias largest herbivore, the Asian elephant (Elephas maximus), in the tropical forests of southern India. C_LIO_LIWe conducted field and mesocosm experiments on woody saplings to examine three mechanisms through which dung deposition by elephants can alter plant community assembly. Specifically, we tested if elephant dung input 1) creates hotspots of plant growth, and shapes plant communities by altering 2) the negative density-dependent effects of neighborhood competition, and 3) interference competition between plant functional types differing in nutrient limitation, namely nitrogen-fixers and non-nitrogen-fixers. C_LIO_LIOur findings show that dung deposition by elephants can generate fine-scale spatial differences in woody sapling communities by creating local growth hotspots and altering competitive interactions. We analyzed relative growth rate and final sapling size in the field experiment, and found that average-sized and large saplings receiving dung inputs were buffered against the negative density-dependent effects of neighborhood competition. In the mesocosm experiment, non-nitrogen-fixing species (which are nitrogen-limited) outcompeted nitrogen-fixers in accumulating biomass when supplied with elephant dung. These outcomes were associated with changes in their relative competitive strength which was stronger for non-nitrogen fixers under dung treatment and for nitrogen-fixers under control. Such bottom-up effects on plant growth and competition can be of substantially large magnitude, as we estimated that elephants in these forests create a total of 11000 such nutrient-rich sites /km2/year, with each elephant redistributing [~]130 kg Nitrogen/year through this pathway and each site receiving [~]20 g Nitrogen. C_LI SynthesisOur findings on the outcomes of sapling competition highlight the role of nutrient redistribution by megaherbivores as an underappreciated driver of species interactions that can alter plant communities at fine scales, effects that are widespread across megaherbivore habitats. Such bottom-up effects of megaherbivores, along with their top-down effects, have important conservation implications and can help in restoring species interactions and spatial heterogeneity in plant communities in defaunated habitats.

ecology↗
bioRxiv2025

Female Asian elephant clans have age-based order but weak dominance resolution

The variation in dominance relationships in group-living species is often interpreted through socioecological frameworks that link social structures to resource-risk distributions. However, in elephants, such inferences are hindered by a lack of comparable assessments of within-group dominance in different species. To advance our understanding of elephant socioecology, we present here, the first study on agonistic and dominance relationships within female Asian elephant clans (most inclusive social groups), and compare our results with those from African savannah elephants. By analysing agonistic interactions, and dominance and association networks based on over four years of observations of five clans, we show that Asian elephants have a resolved but weakly structured within-clan dominance order. Female dyads showed unidirectionality, but triad motif structures of dominance networks suggested resolved dominance only in some clans. Older females were more dominant although there were moderate levels of reversals against age-based order and age difference did not dampen dyadic conflict. Neither older age nor dominant status conferred more central status in the female association network. Weak dominance resolution and the effects of age contrast with the stronger dominance and age-based order found in African savannah elephants. We identify potential socioecological and demographic explanations of female dominance in elephants.

animal behavior and cognition↗
bioRxiv2024

Should elephants graze or browse? The nutritional and functional consequences of dietary variation in a mixed-feeding megaherbivore

Unlike specialist browsers and grazers, the diets of mixed-feeding megaherbivores like elephants are complex and broad, comprising numerous plant species of variable nutritional quality. Here, we revisit an unresolved debate on whether browse is more nutritious than grasses for elephants, as browse is thought to have greater crude protein content. We first analyzed carbon isotopes in 102 fecal samples of Asian elephants to quantify the contribution of browsing and grazing to their diet in Nagarahole National Park, southern India. We show that elephants are predominantly browsers in the grass-scarce Nagarahole forests, in contrast with predominant grazing reported in the nearby grass-abundant savannas of the Nilgiri Biosphere Reserve. We then compared the forage quality of high-browsing and high-grazing diets by analyzing these samples for two proxies of crude protein content (CP): nitrogen content (N%) and Carbon-to-Nitrogen ratio (C:N). Interestingly, high-browsing diets did not have higher N% or lower C:N (proxies for high CP) than low-browsing (high-grazing) diets. To explore the generality of this finding, we analyzed nutritional differences (i.e., CP and fibre content values) between browse and grass across 141 plant species consumed by Asian elephants. We show that woody browse and non-legume browse, which are major components of elephant browse, do not have appreciably higher CP than grasses. Our findings suggest that browsing and grazing broadly have similar nutritional value for such bulk-feeding mixed feeders. Finally, based on the observed habitat-wide variation in browsing, we provide a new framework for assessing how elephants shape woody vegetation across the forests and savannas of Asia, with important implications for conservation and carbon cycling.

ecology↗
bioRxiv2024

miR858a-encoded peptide, miPEP858a, interacts with miR858a promoter and requires C-terminus for the associated functions

MicroRNAs (miRNAs) play a crucial role in regulating gene expression as processed products of primary miRNAs (pri-miRNAs). Recent studies suggest that certain pri-miRNAs encode miRNA-encoded Peptides (miPEPs), influencing miRNA function. Despite this emerging insight, molecular mechanisms and the specific domain or essential amino acid residues required for the functionality of these miPEPs have yet to be explored. Here, we report that the pri-miR858a-encoded peptide, miPEP858a, interacts with the promoter region of the MIR858 gene and its C-terminal region consisting of 14 amino acid residues is indispensable for its functionality. DNA-protein interaction through Yeast-one-hybrid and ChIP-qPCR analysis revealed that miPEP858 interacts with specific region in the MIR858 promoter. An exogenous application of a truncated peptide, the C-terminal region, resulted in enhanced expression and related phenotypic effects, similar to complete miPEP858. Furthermore, C-terminal region of miPEP858a complemented mutant plants lacking miPEP858, highlighting their regulatory role in miR858a expression and associated target genes, impacting flavonoid biosynthesis and plant development. These findings suggest that full-length miPEP858a may not be essential for its functionality. Identifying functional domains of other peptides offers promise, potentially reducing synthesis costs for application in crop plants and avoiding laborious biotechnological approaches to enhance agronomic traits.

plant biology↗
bioRxiv2021

miPEP858/miR858-MYB3-PSK4 module regulates growth and development in Arabidopsis

Small molecules, peptides and miRNAs, are the crucial regulators of plant growth. Here, we show the importance of cross-talk between miPEP858a/miR858a and Phytosulfokine (PSK4) in regulating plant growth and development in Arabidopsis. Genome-wide expression analysis suggested modulated expression of PSK4 in miR858 mutant and overexpression, miR858OX, plants. The silencing of PSK4 in miR858OX plants compromised the growth, whereas over-expression of PSK4 in miR858 mutant rescued the developmental defects. The exogenous application of synthetic PSK4 further complemented the plant development in mutant plants. Exogenous treatment of synthetic miPEP858a in PSK4 mutant led to clathrin-mediated internalization of the peptide however did not enhance growth as in the case of wild-type plants. We also demonstrate that the MYB3 is an important molecular component participating in miPEP858a/miR858a-PSK4 module. Finally, our work highlights the signalling between miR858/miPEP858-MYB3-PSK4 in modulating the expression of key elements involved in auxin responses leading to the regulation of growth. One-sentence summarySignaling network between small molecules, miPEP858a/miR858a and phytosulfokine, regulates plant growth in Arabidopsis.

plant biology↗
bioRxiv2019

A test of the socioecological model in female Asian elephants: the effects of food abundance, food distribution, and competitor density on within-clan and between-clan contests

O_LISocioecological theory attributes variation in social organization of female-bonded species to differences in within- and between-group competition, shaped by food distribution. Strong between-group contests are expected over large, monopolisable resources, and are not generally expected in species that feed on low quality resources distributed across large, undefended home ranges. Within groups, frequent contests are expected over discrete feeding sites but not over low-quality, dispersed resources. C_LIO_LIWe report on the first tests of socioecological theory, largely unexplored in non-primate species, in female Asian elephants. Asian elephants show graminivory, overlapping home ranges, and high fission-fusion dynamics, traits that are thought to be associated with infrequent contests. C_LIO_LIWe studied agonistic interactions within and between female elephant clans with respect to food distribution, food abundance, and competitor density effects of group size and clan density, in a grassland habitat around the Kabini backwaters, southern India. C_LIO_LIWe found that the Kabini grassland had three times the grass biomass as adjacent forests, and between-clan encounters were considerably higher than that known from a neighbouring forest. Individual-level agonism was also more frequent between clans than within clans. Thus, the food-rich habitat patch probably enabled strong between-clan contest competition under graminivory. Moreover, the rate of between-clan encounters increased when more clans were present, and the duration of encounters was positively related to grass biomass at the contested sites. Despite fission-fusion dynamics, within-clan agonism was also somewhat frequent, but not influenced by food distribution, in contradiction to classic socioecological predictions, possibly because of intensified competition due to high density. Interestingly, within-clan agonism increased with female group size until intermediate group sizes, suggesting that the tension between within-group and between-group competition might govern group size, since larger groups are advantageous in this strong between-clan contest regime. C_LIO_LIOur findings refine the current understanding of female elephant socioecology. Despite predominant graminivory and fission-fusion dynamics, within-group agonism can be frequent, especially when large groups face ecological constraints at high density. Further, frequent between-group contests may arise despite graminivory and non-territoriality when food becomes patchy and density is high. These changes may be effected by anthropogenic alteration of habitats. C_LI

ecology↗
bioRxiv2018

Overwhelming presence of non-food vegetation undermines the reliability of NDVI as a surrogate of forage abundance for a large herbivore in a tropical forest habitat

The use of remotely-sensed vegetation indices has increased in wildlife studies but field-based support for their utility as a measure of forage availability largely comes from open-canopy habitats. In this paper, we assessed whether the popular vegetation index, NDVI, actually represents forage availability for Asian elephants in a southern Indian tropical forest. We found that the number of food species was a small percentage of all plant species, and the abundance of food species compared to total species abundance varied across different vegetation categories. NDVI was not a good measure of food abundance in any vegetation category partly because of a) small to moderate proportional abundances of food species relative to the total abundance of all species in that category (herb and shrub categories), b) abundant overstorey vegetation resulting in low correlations between NDVI and food abundance despite a high proportional abundance of food species and a concordance between total abundance and food species abundance (graminoid category), and c) the relevant variables measured and important as food at the ground level (count and GBH) not being related to primary productivity (trees and recruits). NDVI had a negative relationship with the total abundance of graminoids, which represent a bulk of elephant and other herbivore diet, because of the presence of other vegetation types and canopy cover that positively explained NDVI. We also found that spatially interpolated total graminoid abundance modelled from field data outperformed NDVI in predicting total graminoid abundance, although interpolation models of food graminoid species abundance were not satisfactory. Our results reject the utility of NDVI as a surrogate of elephant forage abundance in tropical forests with multistorey vegetation, a finding that has implications for studies of other herbivores in such habitats.

ecology↗