Imperial College London

Dr Samraat Pawar

Faculty of Natural SciencesDepartment of Life Sciences (Silwood Park)

Senior Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 2213s.pawar CV

 
 
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Location

 

2.4KennedySilwood Park

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Summary

 

Publications

Publication Type
Year
to

28 results found

Rizzuto M, Carbone C, Pawar S, 2017, Foraging constraints reverse the scaling of activity time in carnivores., Nat Ecol Evol

The proportion of time an animal spends actively foraging in a day determines its long-term fitness. Here, we derive a general mathematical model for the scaling of this activity time with body size in consumers. We show that this scaling can change from positive (increasing with size) to negative (decreasing with size) if the detectability and availability of preferred prey sizes is a limiting factor. These predictions are supported by a global dataset on 73 terrestrial carnivore species from 8 families spanning >3 orders of magnitude in size. Carnivores weighing ∼5 kg experience high foraging costs because their diets include significant proportions of relatively small (invertebrate) prey. As a result, they show an increase in activity time with size. This shifts to a negative scaling in larger carnivores as they shift to foraging on less costly vertebrate prey. Our model can be generalized to other classes of terrestrial and aquatic consumers and offers a general framework for mechanistically linking body size to population fitness and vulnerability in consumers.

JOURNAL ARTICLE

Schaum C-E, Barton S, Bestion E, Buckling A, Garcia-Carreras B, Lopez P, Lowe C, Pawar S, Smirnoff N, Trimmer M, Yvon-Durocher Get al., 2017, Adaptation of phytoplankton to a decade of experimental warming linked to increased photosynthesis., Nat Ecol Evol, Vol: 1

Phytoplankton photosynthesis is a critical flux in the carbon cycle, accounting for approximately 40% of the carbon dioxide fixed globally on an annual basis and fuelling the productivity of aquatic food webs. However, rapid evolutionary responses of phytoplankton to warming remain largely unexplored, particularly outside the laboratory, where multiple selection pressures can modify adaptation to environmental change. Here, we use a decade-long experiment in outdoor mesocosms to investigate mechanisms of adaptation to warming (+4 °C above ambient temperature) in the green alga Chlamydomonas reinhardtii, in naturally assembled communities. Isolates from warmed mesocosms had higher optimal growth temperatures than their counterparts from ambient treatments. Consequently, warm-adapted isolates were stronger competitors at elevated temperature and experienced a decline in competitive fitness in ambient conditions, indicating adaptation to local thermal regimes. Higher competitive fitness in the warmed isolates was linked to greater photosynthetic capacity and reduced susceptibility to photoinhibition. These findings suggest that adaptive responses to warming in phytoplankton could help to mitigate projected declines in aquatic net primary production by increasing rates of cellular net photosynthesis.

JOURNAL ARTICLE

Pawar S, Dell AI, Savage VM, Knies JLet al., 2016, Real versus Artificial Variation in the Thermal Sensitivity of Biological Traits, AMERICAN NATURALIST, Vol: 187, Pages: E41-E52, ISSN: 0003-0147

JOURNAL ARTICLE

Woodward G, Bonada N, Brown LE, Death RG, Durance I, Gray C, Hladyz S, Ledger ME, Milner AM, Ormerod SJ, Thompson RM, Pawar Set al., 2016, The effects of climatic fluctuations and extreme events on running water ecosystems, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, Vol: 371, ISSN: 0962-8436

JOURNAL ARTICLE

Gibert JP, Dell AI, DeLong JP, Pawar Set al., 2015, Scaling-up Trait Variation from Individuals to Ecosystems, Publisher: Elsevier, Pages: 1-17, ISBN: 9780124200029

Ecology has traditionally focused on species diversity as a way of characterizing the health of an ecosystem. In recent years, however, the focus has increasingly shifted towards trait diversity both within and across species. As we increasingly recognize that ecological and evolutionary timescales may not be all that different, understanding the ecological effects of trait variation becomes paramount. Trait variation is thus the keystone to our understanding of how evolutionary processes may affect ecological dynamics as they unfold, and how these may in turn alter evolutionary trajectories. However, a multi-level understanding of how trait variation scales up from individuals to whole communities or ecosystems is still a work in progress. The chapters in this volume explore how functional trait diversity affects ecological processes across levels of biological organization. This chapter aims at binding the messages of the different contributions and considers how they advance our understanding of how trait variation can be scaled up to understand the interplay between ecological and evolutionary dynamics from individuals to ecosystems.

BOOK CHAPTER

Johnson LR, Ben-Horin T, Lafferty KD, McNally A, Mordecai E, Paaijmans KP, Pawar S, Ryan SJet al., 2015, Understanding uncertainty in temperature effects on vector-borne disease: a Bayesian approach, ECOLOGY, Vol: 96, Pages: 203-213, ISSN: 0012-9658

JOURNAL ARTICLE

Pawar S, 2015, The Role of Body Size Variation in Community Assembly, Advances in Ecological Research, Vol: 52, Pages: 201-248

Body size determines key behavioral and life history traits across species, as well as interactions between individuals within and between species. Therefore, variation in sizes of immigrants, by exerting variation in trophic interaction strengths, may drive the trajectory and outcomes of community assembly. Here, I study the effects of size variation in the immigration pool on assembly dynamics and equilibrium distributions of sizes and consumer–resource size-ratios using a general mathematical model. I find that because small sizes both, improve the ability to invade and destabilize the community, invasibility and stability pull body size distributions in opposite directions, favoring an increase in both size and size-ratios during assembly, and ultimately yielding a right-skewed size and a symmetric size-ratio distribution. In many scenarios, the result at equilibrium is a systematic increase in body sizes and size-ratios with trophic level. Thus these patterns in size structure are ‘signatures’ of dynamically constrained, non-neutral community assembly. I also show that for empirically feasible distributions of body sizes in the immigration pool, immigration bias in body sizes cannot counteract dynamical constraints during assembly and thus signatures emerge consistently. I test the theoretical predictions using data from nine terrestrial and aquatic communities and find strong evidence that natural communities do indeed exhibit such signatures of dynamically constrained assembly. Overall, the results provide new measures to detect general, non-neutral patterns in community assembly dynamics, and show that in general, body size is dominant trait that strongly influences assembly and recovery of natural communities and ecosystems.

JOURNAL ARTICLE

Pawar S, 2015, The role of body size variation in community assembly, Adv. Ecol. Res., Vol: 52

JOURNAL ARTICLE

Pawar S, Dell AI, Savage VM, 2015, From metabolic constraints on individuals to the eco-evolutionary dynamics of ecosystems, Aquat. Funct. Biodivers. An Eco-Evolutionary Approach, Editors: Belgrano, Woodward, Jacob, Publisher: Elsevier, Pages: In Press-In Press

BOOK CHAPTER

Dell AI, Pawar S, Savage VM, 2014, Temperature dependence of trophic interactions are driven by asymmetry of species responses and foraging strategy, JOURNAL OF ANIMAL ECOLOGY, Vol: 83, Pages: 70-84, ISSN: 0021-8790

JOURNAL ARTICLE

Pawar S, 2014, Why are plant-pollinator networks nested?, SCIENCE, Vol: 345, Pages: 383-383, ISSN: 0036-8075

JOURNAL ARTICLE

Tang S, Pawar S, Allesina S, 2014, Correlation between interaction strengths drives stability in large ecological networks, ECOLOGY LETTERS, Vol: 17, Pages: 1094-1100, ISSN: 1461-023X

JOURNAL ARTICLE

Dell AI, Pawar S, Savage VM, 2013, The thermal dependence of biological traits, Ecology, Vol: 94, Pages: 1205-1206, ISSN: 0012-9658

JOURNAL ARTICLE

Johnson LR, Lafferty K, McNally A, Mordecai E, Paaijmans K, Pawar S, Ryan SJet al., 2013, Mapping the Distribution of Malaria: current methods and considerations, Infectious Disease Modelling, Hoboken, N.J., Publisher: Wiley-Interscience, Pages: In Press-In Press

BOOK CHAPTER

Mordecai EA, Paaijmans KP, Johnson LR, Balzer C, Ben-Horin T, Moor E, McNally A, Pawar S, Ryan SJ, Smith TC, Lafferty KDet al., 2013, Optimal temperature for malaria transmission is dramatically lower than previously predicted, ECOLOGY LETTERS, Vol: 16, Pages: 22-30, ISSN: 1461-023X

JOURNAL ARTICLE

Pawar S, Dell AI, Savage VM, 2013, Does consumption rate scale superlinearly? Reply, NATURE, Vol: 493, Pages: E2-E3, ISSN: 0028-0836

JOURNAL ARTICLE

Pawar S, Dell AI, Savage VM, 2012, Dimensionality of consumer search space drives trophic interaction strengths, NATURE, Vol: 486, Pages: 485-489, ISSN: 0028-0836

JOURNAL ARTICLE

Dell AI, Pawar S, Savage VM, 2011, Systematic variation in the temperature dependence of physiological and ecological traits, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 108, Pages: 10591-10596, ISSN: 0027-8424

JOURNAL ARTICLE

Pawar S, 2009, Community assembly, stability and signatures of dynamical constraints on food web structure, JOURNAL OF THEORETICAL BIOLOGY, Vol: 259, Pages: 601-612, ISSN: 0022-5193

JOURNAL ARTICLE

Pawar S, Koo MS, Kelley C, Ahmed MF, Chaudhuri S, Sarkay Set al., 2007, Conservation assessment and prioritization of areas in Northeast India: Priorities for amphibians and reptiles, BIOLOGICAL CONSERVATION, Vol: 136, Pages: 346-361, ISSN: 0006-3207

JOURNAL ARTICLE

Pawar SS, Birand AC, Ahmed MF, Sengupta S, Raman TRSet al., 2007, Conservation biogeography in North-east India: hierarchical analysis of cross-taxon distributional congruence, DIVERSITY AND DISTRIBUTIONS, Vol: 13, Pages: 53-65, ISSN: 1366-9516

JOURNAL ARTICLE

Biswas S, Pawar SS, 2006, Phylogenetic tests of distribution patterns in South Asia: towards an integrative approach, JOURNAL OF BIOSCIENCES, Vol: 31, Pages: 95-113, ISSN: 0250-5991

JOURNAL ARTICLE

Pawar SS, 2005, Geographical variation in the rate of evolution: Effect of available energy or fluctuating environment?, EVOLUTION, Vol: 59, Pages: 234-237, ISSN: 0014-3820

JOURNAL ARTICLE

Birand A, Pawar S, 2004, An ornithological survey in north-east India, Forktail, Vol: 20, Pages: 7-16

We conducted surveys between October 2000 and June 2001 at nine sites in north-east India with low- to mid-elevation tropical evergreen forest, with a particular focus on forest species. 261 bird species were recorded, including five globally threatened species (White-winged Duck Cairina scutulata, Rufous-necked Hornbill Aceros nipalensis, Pallas’s Fish Eagle Haliaeetus leucoryphus, Lesser Adjutant Leptoptilos javanicus, Beautiful Nuthatch Sitta formosa, four Near Threatened species (White-cheeked Partridge Arborophila atrogularis, Great Hornbill Buceros bicornis, Brown Hornbill Anorrhinus tickelli, Blyth’s Kingfisher Alcedo hercules), three restricted-range species, several poorly known species, and a number of new altitudinalrecords. In general, north-east India remains deficient in avifaunal data. Further surveys, especially in the poorly known interior montane tracts, are needed to assist the identification of conservation priorities in the region.

JOURNAL ARTICLE

Pawar SS, Rawat GS, Choudhury BC, 2004, Recovery of frog and lizard communities following primary habitat alteration in Mizoram, Northeast India., BMC Ecol, Vol: 4

BACKGROUND: Community recovery following primary habitat alteration can provide tests for various hypotheses in ecology and conservation biology. Prominent among these are questions related to the manner and rate of community assembly after habitat perturbation. Here we use space-for-time substitution to analyse frog and lizard community assembly along two gradients of habitat recovery following slash and burn agriculture (jhum) in Mizoram, Northeast India. One recovery gradient undergoes natural succession to mature tropical rainforest, while the other involves plantation of jhum fallows with teak Tectona grandis monoculture. RESULTS: Frog and lizard communities accumulated species steadily during natural succession, attaining characteristics similar to those from mature forest after 30 years of regeneration. Lizards showed higher turnover and lower augmentation of species relative to frogs. Niche based classification identified a number of guilds, some of which contained both frogs and lizards. Successional change in species richness was due to increase in the number of guilds as well as the number of species per guild. Phylogenetic structure increased with succession for some guilds. Communities along the teak plantation gradient on the other hand, did not show any sign of change with chronosere age. Factor analysis revealed sets of habitat variables that independently determined changes in community and guild composition during habitat recovery. CONCLUSIONS: The timescale of frog and lizard community recovery was comparable with that reported by previous studies on different faunal groups in other tropical regions. Both communities converged on primary habitat attributes during natural vegetation succession, the recovery being driven by deterministic, nonlinear changes in habitat characteristics. On the other hand, very little faunal recovery was seen even in relatively old teak plantation. In general, tree monocultures are unlikely to support recovery of natura

JOURNAL ARTICLE

Pawar S, 2003, Taxonomic chauvinism and the methodologically challenged, BIOSCIENCE, Vol: 53, Pages: 861-864, ISSN: 0006-3568

JOURNAL ARTICLE

Pawar SS, Choudhury BC, 2000, An inventory of Chelonians from Mizoram, North-east India: new records and some observations on threats, Hamadryad, Vol: 25, Pages: 144-158

We present observations on six species of chelonians documented during herpetological surveys in Ngengpui Wildlife Sanctuary and surrounding areas in south Mizoram, North-east India. All are first reports from the area. These records help fill in distribution gaps for four species, and extend the known distribution range of two (Kachuga sylhetensis and Amyda cartilaginea). Of the latter, A. cartilaginea is reported from the Indian subcontinent for the first time. These records emphasize the need for surveys to refine the distribution mapping of testudines in North-east India, particularly in the hill states. Vernacular names of all species recorded in the present survey are provided, along with notes on their status in the area. We also discuss threats to each species, with special emphasis on the effects of shifting cultivation and consumptive use

JOURNAL ARTICLE

Pawar SS, 1996, Book review: Biogeography of the reptiles of South Asia, Current Science, Vol: 75, Pages: 857-858, ISSN: 1715-5312

JOURNAL ARTICLE

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