ORCID Profile
0000-0001-5445-6589
Current Organisations
National University of Singapore
,
University of Adelaide
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Publisher: Wiley
Date: 03-06-2021
Abstract: The conversion of rainforests into agriculture resulted in massive changes in species ersity and community structure. Although the conservation of the remaining rainforests is of utmost importance, identifying and creating a bio ersity‐friendly agriculture landscape is vital for preserving bio ersity and their functions. Bio ersity studies in agriculture have often been conducted at low elevations. In this study, we compared the functional ersity (FD), phylogenetic ersity (PD) and community structure of birds along an interacting gradient of land use (protected rainforest, reserve buffer and agriculture) and elevation (low, middle and high) in Sri Lanka. Then, we measured the compositional change by identifying how ecological traits (dietary guild, vertical strata, body mass and dispersal ability) and conservation characteristics (forest dependence and threatened status) responded to land use types. Elevation and land use interacted with each other to shape bird FD. Depending on the elevation, FD in agriculture was either higher or similar to forest. However, PD was similar across all elevation and land use types. Bird community structure in forest was functionally and phylogenetically clustered in comparison to agriculture. Insectivorous birds declined from forest to agriculture, and so did understorey and middle‐storey birds. But frugivorous and canopy birds did not change across land use types, while nectarivores, granivores and carnivores proliferated in agriculture. Forests were dominated by birds with low dispersal abilities, but birds in agriculture had more evenly distributed dispersal abilities. About half of all the in iduals in agriculture were composed of forest species, several of which were threatened. Synthesis and applications . Most farmers in Sri Lanka practice agriculture on small farms ( c . 2 ha) and rely on services (e.g. pest control and pollination) provided by bio ersity for their livelihoods. Our results underline the important role of these heterogeneous agriculture landscapes in maintaining high functional ersity (FD) and harbouring several threatened species. While FD in agriculture was comparatively high, conservation decisions based on land use alone cannot be reliable, because land use effects were elevation dependent. Thus, priority setting exercises aimed at designing optimal agriculture landscapes should consider landscape features, in combination with elevation, to benefit both people and wildlife outside protected areas.
Publisher: Informa UK Limited
Date: 08-09-2017
Publisher: Public Library of Science (PLoS)
Date: 13-02-2013
Publisher: Wiley
Date: 22-12-2015
DOI: 10.1111/DDI.12292
Publisher: Public Library of Science (PLoS)
Date: 10-02-2015
Publisher: Public Library of Science (PLoS)
Date: 29-07-2013
Publisher: Wiley
Date: 20-08-2016
DOI: 10.1111/COBI.12785
Abstract: Although deforestation and forest degradation have long been considered the most significant threats to tropical bio ersity, across Southeast Asia (Northeast India, Indochina, Sundaland, Philippines) substantial areas of natural habitat have few wild animals (>1 kg), bar a few hunting-tolerant species. To document hunting impacts on vertebrate populations regionally, we conducted an extensive literature review, including papers in local journals and reports of governmental and nongovernmental agencies. Evidence from multiple sites indicated animal populations declined precipitously across the region since approximately 1980, and many species are now extirpated from substantial portions of their former ranges. Hunting is by far the greatest immediate threat to the survival of most of the region's endangered vertebrates. Causes of recent overhunting include improved access to forests and markets, improved hunting technology, and escalating demand for wild meat, wildlife-derived medicinal products, and wild animals as pets. Although hunters often take common species, such as pigs or rats, for their own consumption, they take rarer species opportunistically and sell surplus meat and commercially valuable products. There is also widespread targeted hunting of high-value species. Consequently, as currently practiced, hunting cannot be considered sustainable anywhere in the region, and in most places enforcement of protected-area and protected-species legislation is weak. The international community's focus on cross-border trade fails to address overexploitation of wildlife because hunting and the sale of wild meat is largely a local issue and most of the harvest is consumed in villages, rural towns, and nearby cities. In addition to improved enforcement, efforts to engage hunters and manage wildlife populations through sustainable hunting practices are urgently needed. Unless there is a step change in efforts to reduce wildlife exploitation to sustainable levels, the region will likely lose most of its iconic species, and many others besides, within the next few years.
Publisher: Wiley
Date: 05-11-2020
Abstract: A single adverse environment event can threaten the survival of small‐ranged species while random fluctuations in population size increase the extinction risk of less‐abundant species. The abundance–range‐size relationship (ARR) is usually positive, which means that smaller‐ranged species are often of low abundance and might face both problems simultaneously. The ARR has been reported to be negative on tropical islands, perhaps allowing endemic species in such environments to remain extant. But there is a need to understand how endemism and land‐use interact to shape ARR. Using 41 highly replicated transects along the full elevational gradient of Sri Lanka, we determined the following: (a) the direction of ARR, (b) if endemism affects ARR and (c) if land‐use (rainforest, buffer and agriculture) changes ARR differently for endemics and non‐endemics. Additionally, (d) we identified endemics that had both lower abundances and smaller range sizes, and ranked them from most threatened (specific to rainforests) to least threatened using a weighted‐interaction nestedness estimator. (a) We found a positive relationship between species abundances and range size. This positive ARR was maintained among endemic and non‐endemic species, across land‐use types and at local and regional scales. (b) The ARR interacted with endemicity and land‐use. Endemics with smaller range sizes had higher abundances than non‐endemics, and particularly higher in rainforests compared to agriculture. In contrast, species with larger range sizes had similar abundances across endemicity and land‐use categories. Many endemics with smaller range sizes are globally threatened therefore, higher abundances may buffer them from extinction risks. (c) Nine (29%) endemics had both below average abundance and elevational range size. The nestedness estimator ranked the endemics Sri Lanka Whistling Thrush Myophonus blighi , Red‐faced Malkoha Phaenicophaeus pyrrhocephalus , Sri Lanka Thrush Zoothera imbricata and White‐faced Starling Sturnornis albofrontus as the four most vulnerable species to local extinction risk, which corresponds to their global extinction risk. We demonstrate that ARR can be positive on tropical islands, but it is influenced by endemism and land‐use. Examining shifts in ARR is not only important to understand community dynamics but can also act as a tool to inform managers about species that require monitoring programmes.
Publisher: Springer Science and Business Media LLC
Date: 25-06-2015
DOI: 10.1038/SREP11569
Abstract: Understory avian insectivores are especially sensitive to deforestation, although regional differences in how these species respond to human disturbance may be linked to varying land-use histories. South Asia experienced widespread conversion of forest to agriculture in the nineteenth century, providing a comparison to tropical areas deforested more recently. In Sri Lanka and the Western Ghats of India, we compared understory insectivores to other guilds and to insectivores with different vertical strata preferences, both inside mixed-species flocks and for the whole bird community. Overall species richness did not change across the land-use gradient, although there was substantial turnover in species composition between land-use types. We found that the proportion of species represented by insectivores was ~1.14 times higher in forest compared to agriculture and the proportion of insectivores represented by understory species was ~1.32 times higher in forests. Mass-abundance relationships were very different when analyzed on mixed-species flocks compared to the total community, perhaps indicating reduced competition in these mutualisms. We show that South Asia fits the worldwide pattern of understory insectivores declining with increased land-use intensity and conclude that these species can be used globally as indicator and/or umbrella species for conservation across different disturbance time scales.
Publisher: Wiley
Date: 02-2023
DOI: 10.1002/ECE3.9835
Abstract: Birds constitute one of the most important seed dispersal agents globally, especially in the tropics. The feeding preferences of frugivorous birds are, therefore, potentially of great ecological importance. A number of laboratory‐based and observational studies have attempted to ascertain the preferences of certain bird species for certain fruit traits. However, little attention has been paid to community‐wide preferences of frugivorous birds and the impact this may have on fruit traits on a broader scale. Here, we used artificial fruits of different colors and sizes to investigate community‐wide fruit trait preferences of birds at three sites along an elevational gradient in Papua New Guinea. We recorded attack rates on artificial fruits as visible impressions made by a bird's beak during a feeding attempt. We also measured the colors and sizes of real fruits at each site, and the gape widths of frugivorous birds, allowing for comparisons between bird feeding preferences and bird and fruit traits. Regardless of elevation, red and purple fruits were universally preferred to green and attacked at similar rates to one another, despite strong elevational patterns in real fruit color. However, elevation had a significant effect on fruit size preferences. A weak, non‐significant preference for large fruits was recorded at 700 m, while medium fruits were strongly preferred at 1700 m and small fruits at 2700 m. These patterns mirror those of both real fruit size and frugivorous bird gape width along the gradient, suggesting the potential for selective pressure of birds on fruit size at different elevations.
Publisher: Wiley
Date: 29-10-2023
DOI: 10.1002/INC3.24
Publisher: Springer Science and Business Media LLC
Date: 23-02-2016
DOI: 10.1038/SREP21822
Abstract: Rising global demand for natural rubber is expanding monoculture rubber ( Hevea brasilensis ) at the expense of natural forests in the Old World tropics. Conversion of forests into rubber plantations has a devastating impact on bio ersity and we have yet to identify management strategies that can mitigate this. We determined the life-history traits that best predict bird species occurrence in rubber plantations in SW China and investigated the effects of surrounding forest cover and distance to roads on bird ersity. Mistletoes provide nectar and fruit resources in rubber so we examined mistletoe densities and the relationship with forest cover and rubber tree diameter. In rubber plantations, we recorded less than half of all bird species extant in the surrounding area. Birds with wider habitat breadths and low conservation value had a higher probability of occurrence. Species richness and ersity increased logarithmically with surrounding forest cover, but roads had little effect. Mistletoe density increased exponentially with rubber tree diameters, but was unrelated to forest cover. To maximize bird ersity in rubber-dominated landscapes it is therefore necessary to preserve as much forest as possible, construct roads through plantations and not forest and retain some large rubber trees with mistletoes during crop rotations.
Publisher: Elsevier BV
Date: 11-2017
Publisher: The Royal Society
Date: 09-2018
DOI: 10.1098/RSOS.181168
Abstract: The relationship between β- ersity and latitude still remains to be a core question in ecology because of the lack of consensus between studies. One hypothesis for the lack of consensus between studies is that spatial scale changes the relationship between latitude and β- ersity. Here, we test this hypothesis using tree data from 15 large-scale forest plots (greater than or equal to 15 ha, diameter at breast height ≥ 1 cm) across a latitudinal gradient (3–30 o ) in the Asia-Pacific region. We found that the observed β- ersity decreased with increasing latitude when s ling local tree communities at small spatial scale (grain size ≤0.1 ha), but the observed β- ersity did not change with latitude when s ling at large spatial scales (greater than or equal to 0.25 ha). Differences in latitudinal β- ersity gradients across spatial scales were caused by pooled species richness (γ- ersity), which influenced observed β- ersity values at small spatial scales, but not at large spatial scales. Therefore, spatial scale changes the relationship between β- ersity, γ- ersity and latitude, and improving s le representativeness avoids the γ-dependence of β- ersity.
Publisher: Wiley
Date: 17-04-2020
DOI: 10.1111/ACV.12588
Publisher: Springer Science and Business Media LLC
Date: 05-11-2013
DOI: 10.1007/S12038-013-9378-8
Abstract: Animals often evaluate the degree of risk posed by a predator and respond accordingly. Since many predators orient their eyes towards prey while attacking, predator gaze and directness of approach could serve as conspicuous indicators of risk to prey. The ability to perceive these cues and discriminate between high and low predation risk should benefit prey species through both higher survival and decreased energy expenditure. We experimentally examined whether Indian rock lizards (Psammophilus dorsalis) can perceive these two indicators of predation risk by measuring the variation in their fleeing behaviour in response to type of gaze and approach by a human predator. Overall, we found that the gaze and approach of the predator influenced flight initiation distance, which also varied with attributes of the prey (i.e. size/sex and tail-raise behaviour). Flight initiation distance (FID) was 43 percent longer during direct approaches with direct gaze compared with tangential approaches with averted gaze. In further, exploratory, analyses, we found that FID was 23 percent shorter for adult male lizards than for female or young male (FYM) lizards. In addition, FYM lizards that showed a tail-raise display during approach had a 71 percent longer FID than those that did not. Our results suggest that multiple factors influence the decision to flee in animals. Further studies are needed to test the generality of these factors and to investigate the proximate mechanisms underlying flight decisions.
Publisher: Elsevier BV
Date: 08-2014
Publisher: The Royal Society
Date: 05-2017
Abstract: Large tracts of tropical rainforests are being converted into intensive agricultural lands. Such anthropogenic disturbances are known to reduce species turnover across horizontal distances. But it is not known if they can also reduce species turnover across vertical distances (elevation), which have steeper climatic differences. We measured turnover in birds across horizontal and vertical s ling transects in three land-use types of Sri Lanka: protected forest, reserve buffer and intensive-agriculture, from 90 to 2100 m a.s.l. Bird turnover rates across horizontal distances were similar across all habitats, and much less than vertical turnover rates. Vertical turnover rates were not similar across habitats. Forest had higher turnover rates than the other two habitats for all bird species. Buffer and intensive-agriculture had similar turnover rates, even though buffer habitats were situated at the forest edge. Therefore, our results demonstrate the crucial importance of conserving primary forest across the full elevational range available.
Publisher: MDPI AG
Date: 26-10-2016
DOI: 10.3390/LAND5040035
Publisher: Wiley
Date: 04-09-2022
DOI: 10.1111/GCB.16404
Abstract: Large‐scale reforestation can potentially bring both benefits and risks to the water cycle, which needs to be better quantified under future climates to inform reforestation decisions. We identified 477 water‐insecure basins worldwide accounting for 44.6% (380.2 Mha) of the global reforestation potential. As many of these basins are in the Asia‐Pacific, we used regional coupled land‐climate modeling for the period 2041–2070 to reveal that reforestation increases evapotranspiration and precipitation for most water‐insecure regions over the Asia‐Pacific. This resulted in a statistically significant increase in water yield ( p .05) for the Loess Plateau–North China Plain, Yangtze Plain, Southeast China, and Irrawaddy regions. Precipitation feedback was influenced by the degree of initial moisture limitation affecting soil moisture response and thus evapotranspiration, as well as precipitation advection from other reforested regions and moisture transport away from the local region. Reforestation also reduces the probability of extremely dry months in most of the water‐insecure regions. However, some regions experience nonsignificant declines in net water yield due to heightened evapotranspiration outstripping increases in precipitation, or declines in soil moisture and advected precipitation.
Publisher: Acta Herpetologica
Date: 2016
Publisher: Cold Spring Harbor Laboratory
Date: 02-07-2022
DOI: 10.1101/2022.06.29.498005
Abstract: The trophic interactions between plants, insect herbivores and their predators are complex and prone to trophic cascades. Theory predicts that predators increase plant biomass by feeding on herbivores. However, it remains unclear whether different types of predators regulate herbivores to the same degree, and how intraguild predation impacts these trophic interactions. Specifically, we lack a more comprehensive look at the effects of various groups of predators on a global scale. Here we report a meta-analysis of 486 experiments gathered from 157 publications reporting the effect of insectivorous vertebrates (birds and bats) and ants on abundances of predatory (spiders, ants, others) and herbivorous (chewers and others) arthropods on arthropod richness and plant damage. Generally, the absence of vertebrate predators led to the increase of predatory arthropods by 18%, herbivorous arthropods by 75%, and plant damage by 47%. In contrast, after the removal of ants, the increase in the abundances of other predatory arthropods did not compensate for missing ants, herbivore arthropods increased their abundances by 53%, and plant damage increased by 146%. The effects of ant exclosures were stronger in communities at lower elevations and latitudes, while we did not detect any clear geographical patterns in the effect of vertebrate exclosures. Neither precipitation nor NDVI had a significant impact on most of the measured effects, and the effect of exclosures was robust for both plant growth forms and different habitat types. We found vertebrate insectivores to be the more dominant predators of arthropods, but we detected that the strength of their trophic cascades was weakened by intraguild predation. On the other hand, we found that although ants were relatively less dominant as predators, and their influence was detectable only in the most productive sites, the effect of trophic cascades on plants they caused was stronger than that of vertebrate insectivores.
Publisher: Elsevier BV
Date: 08-2018
Publisher: Springer Science and Business Media LLC
Date: 23-05-2020
Publisher: Wiley
Date: 21-07-2021
DOI: 10.1002/ECE3.7869
Abstract: When searching for food, great tits ( Parus major ) can use herbivore‐induced plant volatiles (HIPVs) as an indicator of arthropod presence. Their ability to detect HIPVs was shown to be learned, and not innate, yet the flexibility and generalization of learning remain unclear. We studied if, and if so how, naïve and trained great tits ( Parus major ) discriminate between herbivore‐induced and noninduced saplings of Scotch elm ( Ulmus glabra ) and cattley guava ( Psidium cattleyanum ). We chemically analyzed the used plants and showed that their HIPVs differed significantly and overlapped only in a few compounds. Birds trained to discriminate between herbivore‐induced and noninduced saplings preferred the herbivore‐induced saplings of the plant species they were trained to. Naïve birds did not show any preferences. Our results indicate that the attraction of great tits to herbivore‐induced plants is not innate, rather it is a skill that can be acquired through learning, one tree species at a time. We demonstrate that the ability to learn to associate HIPVs with food reward is flexible, expressed to both tested plant species, even if the plant species has not coevolved with the bird species (i.e., guava). Our results imply that the birds are not capable of generalizing HIPVs among tree species but suggest that they either learn to detect in idual compounds or associate whole bouquets with food rewards.
Publisher: Informa UK Limited
Date: 03-09-2016
No related grants have been discovered for Rachakonda Sreekar.