Biology subjects

Lele, A.

Publications and source records attributed to Lele, A..

7 recordsLinked to original sources

bioRxiv2026

Foraging behavior, not prey identity, facilitates niche packing in a tropical montane avifauna

Understanding the mechanisms of key ecological and evolutionary patterns and the restructuring of biodiversity in the Anthropocene is contingent on filling knowledge gaps about resource consumption across trophic levels and how resource use is limited by factors intrinsic to organisms and extrinsic aspects of the environment across deep and shallow timespans. We quantified diet composition and foraging behavior across a community of invertivorous birds in the Ecuadorian Andes to explore how resource use facilitates the packing and expansion of niche space across an elevational gradient, contributing the tropical Andes status as the most species-rich region on earth. We found evidence that niche packing of morphologically similar species may be offset by greater behavioral plasticity in foraging behavior at species-rich lower elevations where competition is likely more intense and invertebrate prey more diverse. We also tested the extent to which the breadth and similarity of birds foraging and dietary niches are shaped by the environmental and competitive gradient across elevation versus species identity and phylogenetic similarity. The specific behaviors and substrates that birds used were far more strongly associated with species identity than elevation, particularly for behaviors requiring specialized morphology that is phylogenetically conserved. In contrast, species identity had little effect on prey selection, which was more strongly associated with elevation. Our findings suggest that elevational range dynamics and niche packing of tropical montane birds are more strongly shaped by phylogenetic constraints on foraging behavior than by specializing on specific prey taxa, highlighting the importance of maintaining structural integrity in tropical forests for preserving functional diversity.

ecology↗

bioRxiv2025

Changes in habitat connectivity for range-restricted birds reflect patterns of woodland invasion

Habitat fragmentation and landscape change are common causes of concern for species persistence, especially for habitat specialists. The composition of the matrix surrounding habitat fragments influences connectivity between them, which affects gene flow across the landscape. This can further impact populations in various ways. The Shola Sky Island landscapes naturally comprise a biphasic, forest-grassland mosaic ecosystem unique to the high-altitude regions of the Western Ghats of India. Earlier, this mosaic consisted of patches of native cloud forests embedded in a large grassland matrix. Over the last few decades, however, extensive invasion (up to 60%) of timber species into native grasslands has inverted this mosaic, i.e., small patches of grasslands are nested in a woodland matrix. We attempt to study the effects of these modifications on functional habitat connectivity in this region by modelling species movement using a circuit theory-based algorithm. We do this for seven Shola endemic, range-restricted bird species; six forest-specialist and one grassland-specialist species, based on a decade of field data. We consider a range of species-environment relationships and dispersal capacities for a past, relatively uninvaded landscape and a present, highly modified landscape. We used bird occupancy data (presence/absence from a total of 720 grid cells from targeted occupancy surveys for forest species and 744 presence locations for grassland species from occupancy surveys combined with opportunistic records) along with remotely sensed landscape, vegetation, climatic and topographic variables. We find that connectivity has increased overall for forest specialists, but has reduced for the grassland species. This pattern is concordant with regions where woodland cover from invasive timber species has expanded over approximately two decades. We also identify species-specific areas of low and high connectivity, which may have implications for gene flow within the landscape. This would help focus conservation efforts and predict how future landscape change might affect species persistence.

ecology↗

bioRxiv2025

Invasion blurs the biphasic mosaic, amplifies the 'wicked problem' through impacts on avian distributions in montane habitats.

Globally, managing invasive plants and habitat transformation often constitutes a wicked problem due to highly variable impacts on threatened biodiversity. In naturally patchy habitats, invasion can blur edges, pushing species beyond natural habitats. In biphasic habitats like forest-grassland mosaics, complementary sets of specialist species offer a unique configuration to examine such impacts from both directions. In the Shola Sky Islands, extensive woody invasive stands and agriculture/production landscapes have created a set of transformed closed and open habitats structurally similar to their natural counterparts. We expect the species usage of such novel habitats to reflect their dietary and habitat specialisation. We conducted 4,519 surveys across 1,204 randomly selected grid cells for the avian community, covering the global distribution of five species. For a select set of specialist and generalist species, we estimated patch occupancy and abundance using hierarchical models. We used acoustics to assess species persistence across invasion stages with automated recorders deployed across a year. We used community occurrence data to examine functional traits that correspond to habitat colonisation. Forest species occur year-round in transformed woody habitats across all invasion stages, and habitat overstory determines avian functional diversity. Forest specialists decline in transformed habitats across high-contrast edges, while generalists increase across both high- and low-contrast edges, indicating a supertramp strategy. Grassland specialist, however, decline strongly beyond all edges, creating a duality of losses and gains across the biphasic matrix. We highlight the diversity of threatened species responses to invasion and habitat transformation, underscoring the importance of nuanced approaches to habitat restoration, particularly in biphasic habitats.

ecology↗

bioRxiv2024

Mastering the Manu - How humans create large splashes

Manu jumping, a popular water diving style amongst M[a]ori people in New Zealand, focuses on creating large splashes. Divers perform aerial maneuvers such as the "utkatasana" pose, entering the water in a V-shape, and executing underwater maneuvers to maximize the splash size. Our study explores the underlying fluid dynamics of Manu jumping and demonstrates how two key parameters, the V-angle and the timing of body opening, can maximize the Worthington jet formation. To accurately replicate human manu jumping, we studied water entry of both passive solid objects with varying V angles and an active body opening robot (Manubot). The analysis revealed that a 45-degree V angle is optimal for maximizing Worthington jet formation, consistent with human diving data. This angle balances a large cavity size and a deep pinch-off depth. The body opening within a timing window of [Formula] synchronizes the robots potential energies to be timely transferred to the cavity formation, producing the strongest and most vertical, i.e., ideal, Worthington jets. Based on our experimental findings, we propose optimal parameters for generating the largest Manu splashes. These insights offer engineering perspectives on how to modulate underwater cavity dynamics using both passive and active body formations.

biophysics↗

bioRxiv2024

Inward transport of organelles drives outward migration of the spindle during C. elegans meiosis

Cortical positioning of the meiotic spindle within an oocyte is required to expel chromosomes into polar bodies to generate a zygote with the correct number of chromosomes. In C. elegans, yolk granules and mitochondria are packed inward, away from the cortex while the spindle moves outward, both in a kinesin-dependent manner. The kinesin-dependent inward packing of yolk granules suggests the existence of microtubules with minus ends at the cortex and plus ends extending inward, making it unclear how kinesin moves the spindle outward. We hypothesized that inward packing of organelles might indirectly force the spindle outward by volume exclusion. To test this hypothesis, we generated a strain in which the only kinesin consists of motor domains with no cargo-binding tail optogenetically attached to mitochondria. This mitochondria-only kinesin packed mitochondria into a tight ball and efficiently moved the meiotic spindle to the cortex, supporting the volume exclusion hypothesis.

cell biology↗

bioRxiv2024

Pathogenic diversification of the gut commensal Providencia alcalifaciens via acquisition of a second type III secretion system

Providencia alcalifaciens is a Gram-negative bacterium found in a wide variety of water and land environments and organisms. It has been isolated as part of the gut microbiome of animals and insects, as well as from stool samples of patients with diarrhea. Specific P. alcalifaciens strains encode gene homologs of virulence factors found in other pathogenic members of the same Enterobacterales order, such as Salmonella enterica serovar Typhimurium and Shigella flexneri. Whether these genes are also pathogenic determinants in P. alcalifaciens is not known. Here we have used P. alcalifaciens 205/92, a clinical isolate, with in vitro and in vivo infection models to investigate P. alcalifaciens-host interactions at the cellular level. Our particular focus was the role of two type III secretion systems (T3SS) belonging to the Inv-Mxi/Spa family. T3SS1b is widespread in Providencia spp. and encoded on the chromosome. T3SS1a is encoded on a large plasmid that is present in a subset of P. alcalifaciens strains, which are primarily isolates from diarrheal patients. Using a combination of electron and fluorescence microscopy and gentamicin protection assays we show that P. alcalifaciens 205/92 is internalized into eukaryotic cells, rapidly lyses its internalization vacuole and proliferates in the cytosol. This triggers caspase-4 dependent inflammasome responses in gut epithelial cells. The requirement for the T3SS1a in entry, vacuole lysis and cytosolic proliferation is host-cell type specific, playing a more prominent role in human intestinal epithelial cells as compared to macrophages. In a bovine ligated intestinal loop model, P. alcalifaciens colonizes the intestinal mucosa, inducing mild epithelial damage with negligible fluid accumulation. No overt role for T3SS1a or T3SS1b was seen in the calf infection model. However, T3SS1b was required for the rapid killing of Drosophila melanogaster. We propose that the acquisition of two T3SS by horizontal gene transfer has allowed P. alcalifaciens to diversify its host range, from a highly virulent pathogen of insects to an opportunistic gastrointestinal pathogen of animals.

microbiology↗

bioRxiv2019

Local extinction of a montane, endemic grassland bird driven by landscape change across its global distribution

ContextTropical montane habitats support high biodiversity, and are hotspots of endemism, with grasslands being integral components of many such landscapes. The montane grasslands of the Western Ghats have seen extensive land-use change over anthropogenic timescales. The factors influencing the ability of grassland-dependent species to persist in habitats experiencing loss and fragmentation, particularly in montane grasslands, are poorly known.\n\nObjectivesWe studied the relationship between the Nilgiri pipit Anthus nilghiriensis, a threatened endemic bird that typifies these montane grasslands, and its habitat, across most of its global distribution. We examined what habitat features make remnants viable habitat, which is necessary for effective management.\n\nMethodsWe conducted 663 surveys in 170 sites and used both single-season occupancy modelling and N-mixture modelling to account for processes influencing detection, presence, and abundance.\n\nResultsElevation had a positive influence on species presence, patch size had a moderate positive influence and patch isolation a moderate negative influence. Species abundance was positively influenced by elevation and characteristics related to habitat structure, and negatively influenced by the presence of invasive woody vegetation.\n\nConclusionsThe strong effect of elevation on the highly range-restricted Nilgiri pipit makes it vulnerable to, and an indicator of, climate change. This highly range-restricted species is locally extinct at several locations and persists at low densities in remnants of recent fragmentation, suggesting an extinction debt. Our findings indicate a need to control and reverse the spread of exotic woody invasives to preserve the grasslands themselves and the specialist species dependent upon them.

ecology↗