Background Hyptis suaveolens(L.)Poit.,native to the American tropics,is a pantropical annual plant and a major invasive species throughout India.It was anticipated that the availability of sunlight,coupled with its su...Background Hyptis suaveolens(L.)Poit.,native to the American tropics,is a pantropical annual plant and a major invasive species throughout India.It was anticipated that the availability of sunlight,coupled with its superior reproductive potential,persistent propagule bank,and dispersal ability,could lead to an increase in the growth and spread of this invader,thus potentially impeding herbaceous growth and diversity in non-native areas.Clarifying its ecological fitness and competitive performance will be useful to manage the spread of H.suaveolens in natural ecosystems that are facing a wide range of anthropogenic pressures.Methods The present study is a three-tier experiment.In the first tier,a field study was conducted to assess the patterns of H.suaveolens abundance and herbaceous species diversity in response to light availability(sun,842-1072μmol m^(-2)s^(-1)and shade 253-341μmol m^(-2)s^(-1))in the tropical dry deciduous ecosystems in the Vindhyan highlands,India.Furthermore,the impact of H.suaveolens abundance on the resident native and non-native species abundance and diversity was also studied.In the second tier,a randomized common garden experiment was conducted to understand the trait fitness of H.suaveolens in sun(940μmol m^(-2)s^(-1))and shade(300μmol m^(-2)s^(-1))conditions.In the third tier,a plant growth chamber experiment with high-light(940μmol m^(-2)s^(-1))and low-light(300μmol m^(-2)s^(-1))treatments was done to learn how H.suaveolens partitions its biomass between aboveground and belowground plant parts.Results The field study indicated that the sunlit areas had a higher abundance of H.suaveolens and a lower diversity of resident herbaceous species than the shaded areas.The common garden experiment showed that sun-dwelling H.suaveolens individuals performed better in germinative,vegetative,eco-physiological,and reproductive traits than the shade-dwelling individuals.The growth chamber experiment exhibited that plants grown in high-light environment had greater seed germination,seedling recruitment,and aboveground biomass than those grown in low-light environment,whereas plants grown in low-light environment exhibited a higher root mass ratio than the high-light individuals.These results suggest that H.suaveolens individuals mask the understory vegetation owing to higher seedling recruitment,relative growth rate,photosynthetic performance,resource acquisition-allocation,and reproductive output in response to high-light conditions.Conclusions The study concludes that light significantly controls the invasive population dynamics of H.suaveolens in dry deciduous forests.In high-light areas,H.suaveolens populations dominate the forest understory with suboptimal shade tolerance.In shade environment,H.suaveolens maintains a persistent soil seed bank along with‘Oskarindividuals'that become active in response to high-light availability.The modus operandi is a'sit and wait'strategy.The current study provides insights on prioritizing areas for H.suaveolens management that will potentially reduce the risk of biological invasions on the native species diversity of tropical regions.展开更多
基金the Science and Engineering Research Board,Department of Science and Technology,India(File No.SERB-EEQ/2021/000356)IOE,Institute of Science,Banaras Hindu University
文摘Background Hyptis suaveolens(L.)Poit.,native to the American tropics,is a pantropical annual plant and a major invasive species throughout India.It was anticipated that the availability of sunlight,coupled with its superior reproductive potential,persistent propagule bank,and dispersal ability,could lead to an increase in the growth and spread of this invader,thus potentially impeding herbaceous growth and diversity in non-native areas.Clarifying its ecological fitness and competitive performance will be useful to manage the spread of H.suaveolens in natural ecosystems that are facing a wide range of anthropogenic pressures.Methods The present study is a three-tier experiment.In the first tier,a field study was conducted to assess the patterns of H.suaveolens abundance and herbaceous species diversity in response to light availability(sun,842-1072μmol m^(-2)s^(-1)and shade 253-341μmol m^(-2)s^(-1))in the tropical dry deciduous ecosystems in the Vindhyan highlands,India.Furthermore,the impact of H.suaveolens abundance on the resident native and non-native species abundance and diversity was also studied.In the second tier,a randomized common garden experiment was conducted to understand the trait fitness of H.suaveolens in sun(940μmol m^(-2)s^(-1))and shade(300μmol m^(-2)s^(-1))conditions.In the third tier,a plant growth chamber experiment with high-light(940μmol m^(-2)s^(-1))and low-light(300μmol m^(-2)s^(-1))treatments was done to learn how H.suaveolens partitions its biomass between aboveground and belowground plant parts.Results The field study indicated that the sunlit areas had a higher abundance of H.suaveolens and a lower diversity of resident herbaceous species than the shaded areas.The common garden experiment showed that sun-dwelling H.suaveolens individuals performed better in germinative,vegetative,eco-physiological,and reproductive traits than the shade-dwelling individuals.The growth chamber experiment exhibited that plants grown in high-light environment had greater seed germination,seedling recruitment,and aboveground biomass than those grown in low-light environment,whereas plants grown in low-light environment exhibited a higher root mass ratio than the high-light individuals.These results suggest that H.suaveolens individuals mask the understory vegetation owing to higher seedling recruitment,relative growth rate,photosynthetic performance,resource acquisition-allocation,and reproductive output in response to high-light conditions.Conclusions The study concludes that light significantly controls the invasive population dynamics of H.suaveolens in dry deciduous forests.In high-light areas,H.suaveolens populations dominate the forest understory with suboptimal shade tolerance.In shade environment,H.suaveolens maintains a persistent soil seed bank along with‘Oskarindividuals'that become active in response to high-light availability.The modus operandi is a'sit and wait'strategy.The current study provides insights on prioritizing areas for H.suaveolens management that will potentially reduce the risk of biological invasions on the native species diversity of tropical regions.
