Biology subjects

Halder, K.

Publications and source records attributed to Halder, K..

3 recordsLinked to original sources

bioRxiv2026

Spatial Trophic Dynamics Shape and are Shaped by Desertification Transitions

Drylands, which sustain billions of people, face desertification driven by climate change and grazing pressures. From the bottom up, desertification is affected by water availability, with vegetation often self-organising into spatial patterns that vary with aridity levels. How these patterns and ultimately, desertification transitions, are affected by the spatial dynamics of higher trophic levels remain, however, poorly understood. Here, we introduce a spatially explicit tri-trophic model that links vegetation pattern formation to consumer-resource interactions and foraging behaviour. We find that the nature of vegetation spatial distribution and desertification transition strongly influence consumer spatial organisation, movement, and synchrony. Vegetation organised regularly in space generates "boom--bust" synchronised metapopulations, whereas fractal vegetation organisation generates scale-free consumer clustering and low synchrony. Our results reveal a reciprocal coupling between spatial trophic dynamics and ecosystem resilience, underscoring the need to integrate trophic interactions and behaviour into predictions informing management strategies for dryland ecosystems.

ecology↗

bioRxiv2025

Vegetation clump size and number as indicators for alternative stable states in semi-arid ecosystems

Dryland ecosystems are vulnerable to desertification, a pressing issue in the face of global climate change. In these ecosystems, vegetation often grows in spatially periodic patterns that differ as aridity increases (gaps, labyrinths and clumps), which has been widely studied theoretically, aiming to assess the proximity of the system to desertification. While some theoretical models predict smooth desertification transitions, most typically predict an abrupt transition linked to the possibility of two alternative stable states (desert and vegetated states), predictions that are yet to be confirmed empirically. If this bistability of alternative stable states occurs, however, environmental fluctuations and the history of the ecosystem determine which state ultimately materializes. This uncertainty makes it harder to predict desertification, compounding the challenges posed by it. Here, we combine empirical data and theoretical methods to investigate the links between bistability and vegetation spatial organization, which can help identify the presence of alternative stable states. We found that, although the presence of vegetation clumps is not indicative of bistability, changes in clump morphology can provide reliable indicators of bistability and an impending desertification transition. Thus, our methodology indirectly identifies whether desertification will occur abruptly, and whether restoration efforts should consider a potential ecosystem history-dependence.

ecology↗

bioRxiv2022

Bacterial communities associated with the surfaces of the fresh fruits sold around Dhaka Medical College and Hospital and their anti-microbial profiles

BackgroundNow-a-days, fresh fruits are popular sources of healthy diets with low energy density. Since they are consumed raw, it may act as a source of foodborne disease and a reservoir for antibiotic resistant organisms. This study aimed to determine microbial prevalence among the fruits sold outside Dhaka Medical College Hospital (DMCH) along with their antimicrobial profiles and to detect antimicrobial resistance genes among the resistant organisms. MethodsThirty-five different types of fruits were bought from around DMCH and analyzed for the presence of bacteria. Antibiotic sensitivity was done and ESBL, AmpC {beta}-lactamase, and MBL positive strains were identified by standard methods followed by PCR to detect ESBL, AmpC {beta}-lactamase, and MBL genes. FindingsTwenty seven different organisms were isolated and identified which were-Klebsiella spp (33{middle dot}33%), Citrobacter spp (29{middle dot}64%), Enterobacter spp (22{middle dot}22%), Escherichia coli (11{middle dot}11%), and Staphylococcus aureus (3{middle dot}70%). Among them 48{middle dot}15% organisms were resistant to different antibiotics. Only one organism (Citrobacter spp) produced ESBL phenotypically (7{middle dot}69%). Two (15{middle dot}38%) were positive for AmpC {beta}-lactamase and one of these (Enterobacter spp) possessed both SHV and CTX-M15A genes by PCR. Imipenem resistance was 84{middle dot}62% of the antibiotic resistant organisms, and 10 (90{middle dot}91%) were phenotypically MBL positive by CD test, DDS test, and MHT. By PCR, one Enterobacter spp had MBL encoding gene OXA-48. InterpretationFresh fruits, contaminated with pathogens, might be a source of transmission of resistant organisms and attribute to public health issues. FundingThe office of Directorate General of Health Service, Ministry of Health and Family Welfare, Bangladesh. ImportanceFruits sold around Dhaka Medical College and Hospital (DMCH) are usually consumed by patients, patients attendant and Health care worker. This investigation emphasized not only on the extent of bacterial contamination but also attempted to measure the anti-microbial profile of these organisms isolated from the fruits commonly available and readily consumed in and around DMCH.

microbiology↗