Geetha Ramaswami

Research Associate, Other Initiatives

Geetha 20ramaswami 20photo

PhD

I am a research associate at the Nature Conservation Foundation. I am interested in invasive plants, especially how they affect and get affected by the ecosystem they invade. I worked on an invasive plant – Lantana camara – for my PhD; trying to understand how the environment affects where and how this species spreads and also how indigenous species respond to the presence of this invasive plant. I later worked on a short project assessing the reasons by which the management of Lantana has largely failed in Indian forests. I currently work on understanding the impacts of  Lantana on native plant-disperser interactions. 

Projects

Publications

  • Journal Article
    2017
    Plant-disperser mutualisms in a semi-arid habitat invaded by Lantana camara L.
    Plant Ecology 218 (8): 935-946

    Dispersal is an important ecological process that affects plant population structure and community composition. Invasive plants with fleshy fruits rapidly form associations with native and invasive dispersers, and may affect existing native plant-disperser associations. We asked whether frugivore visitation rate and fruit removal was associated with plant characteristics in a community of fleshy-fruited plants and whether an invasive plant receives more visitation and greater fruit removal than native plants in a semi-arid habitat of Andhra Pradesh, India. Tree-watches were undertaken at individuals of nine native and one invasive shrub species to assess the identity, number and fruit removal by avian frugivores. Network analyses and generalised linear mixed-effects models were used to understand species and community-level patterns. All plants received most number of visits from abundant, generalist avian frugivores. Number of frugivore visits and time spent by frugivores at individual plants was positively associated with fruit crop size, while fruit removal was positively associated with number of frugivore visits and their mean foraging time at individual plants. The invasive shrub, Lantana camara L. (Lantana), had lower average frugivore visit rate than the community of fleshy-fruited plants and received similar average frugivore visits but greater average per-hour fruit removal than two other concurrently fruiting native species. Based on the results of our study, we infer that there is little evidence of competition between native plants and Lantana for the dispersal services of native frugivores and that more data are required to assess the nature of these interactions over the long term. We speculate that plant associations with generalist frugivores may increase the functional redundancy of this frugivory network, buffering it against loss of participating species.

  • Dataset
    2017
    Data from: Plant-disperser mutualisms in a semi-arid habitat invaded by Lantana camara L. Plant Ecology
    Data Dryad. http://dx.doi.org/10.5061/dryad.gc6dm
  • Popular Article
    2016
    Shekru sees a blazing issue
    The Hindu in School, 13 July
  • Popular Article
    2016
    An urban menagerie
    The Hindu in School, 20 January
  • Popular Article
    2015
    Little Green Flesh-eaters
    The Hindu in School, 21 January
  • Journal Article
    2014
    Addressing the management of a long-established invasive shrub: the case of Lantana camara in Indian forests
    Geetha Ramaswami, Soumya Prasad, David Westcott, S. P. Subuddhi, Raman Sukumar
    Indian Forester, 140 (2) : 129-136
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    PDF, 237 KB

    Since its introduction in India 200 years ago, Lantana camara (Lantana) has become established and naturalised across a wide range of habitats. In Indian protected areas, lantana has been predominately managed using a range of mechanical removal approaches, costing up to ` 6000 per hectare. However, managed sites are rapidly recolonized by lantana and management programmes rarely achieve their goal of lantana eradication. In present study, we quantified recolonisation of lantana at sites that were either managed only once or for two consecutive years in Rajaji National Park, Uttarakhand. Rapid recolonisation and recruitment is occuring from seed dispersal from surrounding lantana populations, soil seed banks and vegetative regeneration. To manage lantana effectively we need to consider these ecological processes. An alternate management programme is recommended for long-established invasive plants such as lantana, that focuses on (a) prioritizing critical habitats that require management of invasive species (b) long-term monitoring and management scaled to timeframes of ecological processes, i.e., lantana dispersal and soil seed banks,  and (c) phased enlargement of managed sites such that over time, high-priority habitats can be isolated from dispersal originating from surrounding lantana source populations. 

  • Popular Article
    2014
    A Hydra-headed plant
    The Hindu in School, 26 November
  • Journal Article
    2014
    Lantana camara L. (Verbenaceae) invasion along streamsin a heterogeneous landscape
    Geetha Ramaswami, Raman Sukumar
    Journal of Biosciences, 39(4), doi: 10.1007/s12038-014-9465-5

    Streams are periodically disturbed due to flooding, act as edges between habitats and also facilitate the dispersal of propagules, thus being potentially more vulnerable to invasions than adjoining regions. We used a landscape-wide transect-based sampling strategy and a mixed effects modelling approach to understand the effects of distance from stream, a rainfall gradient, light availability and fire history on the distribution of the invasive shrub Lantana camara L.(lantana) in the tropical dry forests of Mudumalai in southern India. The area occupied by lantana thickets and lantana stem abundance were both found to be highest closest to streams across this landscape with a rainfall gradient. There was no advantage in terms of increased abundance or area occupied by lantana when it grew closer to streams in drier areas as compared to moister areas. On an average, the area covered by lantana increased with increasing annual rainfall. Areas that experienced greater number of fires during 1989–2010 had lower lantana stem abundance irrespective of distance from streams. In this landscape, total light availability did not affect lantana abundance. Understanding the spatially variable environmental factors in a heterogeneous landscape influencing the distribution of lantana would aid in making informed management decisions at this scale.

  • Journal Article
    2013
    Long-Term Environmental Correlates of Invasion byLantana camara (Verbenaceae) in a Seasonally DryTropical Forest
    Geetha Ramaswami, Raman Sukumar
    PLoS ONE 8(10): e76995. doi:10.1371/journal.pone.0076995
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    PDF, 406 KB

    Invasive species, local plant communities and invaded ecosystems change over space and time. Quantifying this change may lead to a better understanding of the ecology and the effective management of invasive species. We used data on density of the highly invasive shrub Lantana camara (lantana) for the period 1990–2008 from a 50 ha permanent plot in a seasonally dry tropical forest of Mudumalai in southern India. We used a cumulative link mixed-effects regression approach to model the transition of lantana from one qualitative density state to another as a function of biotic factors such as indicators of competition from local species (lantana itself, perennial grasses, invasive Chromolaena odorata, the native shrub Helicteres isora and basal area of native trees) and abiotic factors such as fire frequency, inter-annual variability of rainfall and relative soil moisture. The density of lantana increased substantially during the study period. Lantana density was negatively associated with the density of H. isora, positively associated with basal area of native trees, but not affected by the presence of grasses or other invasive species. In the absence of fire, lantana density increased with increasing rainfall. When fires occurred, transitions to higher densities occurred at low rainfall values. In drier regions, lantana changed from low to high density as rainfall increased while in wetter regions of the plot, lantana persisted in the dense category irrespective of rainfall. Lantana seems to effectively utilize resources distributed in space and time to its advantage, thus outcompeting local species and maintaining a population that is not yet self-limiting. High-risk areas and years could potentially be identified based on inferences from this study for facilitating management of lantana in tropical dry forests.

  • Journal Article
    2013
    Performance of established native seedlings in relationto invasive Lantana camara, rainfall and species’ habitatpreferences in a seasonally dry tropical forest
    Geetha Ramaswami, Raman Sukumar
    Plant Ecology, 214(3): 397-408, doi:10.1007/s11258-013-0177-y
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    PDF, 884 KB

    Native species’ response to the presence of invasive species is context specific. This response cannot be studied in isolation from the prevailing environmental stresses in invaded habitats such as seasonal drought. We investigated the combined effects of an invasive shrub Lantana camara L. (lantana), seasonal rainfall and species’ microsite preferences on the growth and survival of 1105 naturally established seedlings of native trees and shrubs in a seasonally dry tropical forest. Individuals were followed from April 2008 to February 2010, and growth and survival measured in relation to lantana density, seasonality of rainfall and species characteristics in a 50 ha permanent forest plot located in Mudumalai, southern India. We used a mixed effects modelling approach to examine seedling growth and generalized linear models to examine seedling survival. The overall relative height growth rate of established seedlings was found to be very low irrespective of the presence or absence of dense lantana. 22- month growth rate of dry forest species was lower under dense lantana while moist forest species were not affected by the presence of lantana thickets. 4-month growth rates of all species increased with increasing inter-census rainfall. Community results may be influenced by responses of the most abundant species, Catunaregam spinosa, whose growth rates were always lower under dense lantana. Overall seedling survival was high, increased with increasing rainfall and was higher for species with dry forest preference than for species with moist forest preference. The high survival rates of naturally established seedlings combined with their basal sprouting ability in this forest could enable the persistence of woody species in the face of invasive species. 

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