Biology subjects

Oduor, A. M. O.

Publications and source records attributed to Oduor, A. M. O..

6 recordsLinked to original sources

bioRxiv2025

Artificial light at night and an invasive snail synergistically enhance the invasion of a non-native macrophyte

Herbivory shapes plant invasion outcomes, yet its role in aquatic plant invasions under changing environmental conditions, such as artificial light at night (ALAN), remains poorly understood. We conducted three experiments using invasive macrophyte Myriophyllum aquaticum, a native macrophyte community (Vallisneria natans, Hydrilla verticillata, M. spicatum), invasive snail Pomacea canaliculata, and native snail Cipangopaludina chinensis to test the combined effects of ALAN and herbivory on non-native macrophyte invasions. ALAN increased M. aquaticum height and total biomass, but had no effect on native species growth. In feeding assays, P. canaliculata consumed all three native species but consistently avoided M. aquaticum under both light treatments. C. chinensis showed no feeding in no-choice assays, but in choice assays, consumed H. verticillata and M. spicatum under No-ALAN and only M. spicatum under ALAN. In community mesocosms, P. canaliculata reduced native macrophyte biomass by 48.0% under No-ALAN and 87.2% under ALAN without affecting M. aquaticum. This selective feeding increased M. aquaticums proportional biomass, with a stronger effect under ALAN than No-ALAN. These results suggest that ALAN can indirectly facilitate non-native macrophyte invasion by amplifying their relative biomass within native communities, particularly in the presence of invasive herbivores, and may promote invasional meltdown through altered feeding preferences.

ecology↗

bioRxiv2024

Diversity and productivity of a natural grassland decline with the number of global change factors

Grasslands are highly diverse ecosystems providing important ecosystem services, but they currently face a variety of anthropogenic stressors simultaneously. Quantifying grassland responses to global change factors (GCFs) is crucial for developing effective strategies to mitigate the negative impacts of global change on grassland communities and to promote their resilience in the face of future environmental challenges. We conducted a field experiment in the Songnen grassland, northeastern China, to test the combined effects of 0, 1, 2, 4, 6, and 8 GCFs, including fungicide, herbicide, insecticide, antibiotic stress, heavy metal pollution, light pollution, microplastic pollution, nitrogen deposition, tillage disturbance, and increased precipitation. We found that within one year, the increasing number of GCFs negatively impacts on both the productivity and diversity of grassland communities. In comparison to exposure to a single GCF, exposure to 8 GCFs led to a reduction in productivity and species richness by 42.8% and 42.9%, respectively. Furthermore, these negative effects seem to be linked to the reduction of dominant species and the concurrent increase in neonative species. The results of hierarchical diversity-interaction modeling suggested that the adverse impacts of an increasing number of GCFs on community productivity and diversity are attributable to both the specific identities of GCFs involved and their unique pairwise interactions. The results suggest that grasslands may quickly loose stability and degrade more rapidly in response to multiple co-occurring GCFs. Greater efforts should be made to conserve the functions and services of grassland ecosystems by reducing the impacts of human activities.

ecology↗

bioRxiv2024

Contrasting impacts of invasive Opuntia cacti on mammal habitat use

Biological invasions impact ecosystems worldwide, including through changing the behaviour of native species. Here, we used camera traps to investigate the effects of invasive Opuntia cacti on the habitat use of twelve mammal species in Laikipia County, Kenya, an internationally important region of mammalian biodiversity. We found that Opuntia impacted mammal occupancy and activity, but the strength and direction of the effects varied among species and between seasons, and depended on the spatial scale at which Opuntia was considered. Notably, we observed consistent positive effects for olive baboons and elephants, two major consumers of Opuntia fruit. We also observed seasonally varying effects on the occupancy of two key grazers: Grevys zebra and plains zebra. As well as having important implications for mammal conservation, ecosystem functioning, and the future spread of Opuntia, our findings highlight behavioural changes in large mammals as a potentially important pathway through which invasive species impact ecosystems.

ecology↗

bioRxiv2023

Live soil ameliorated the negative effects of biodegradable but not non-biodegradable microplastics on the growth of plant communities

O_LIPlastic pollution has become a global environmental problem. Alternative use of biodegradable plastics has been proposed to mitigate the pollution problem caused by the traditional non-biodegradable plastics but the relative impacts of both types of microplastics on plant community productivity and diversity remain unknown. Microplastics can affect growth of individual plants directly by altering plant physiological processes and indirectly by altering soil biota that in turn influence plant growth. However, it remains unknown whether soil biota can mediate impact of biodegradable and non-biodegradable microplastics on plant community productivity and diversity due to a lack of studies on the topic. C_LIO_LIHere, we performed a greenhouse experiment with six plant communities and five biodegradable and five non-biodegradable microplastics to test whether: 1) biodegradable microplastics have a less negative effect on plant community biomass production and diversity than non-biodegradable microplastics, and 2) soil microorganisms differentially mediate the effects of non-biodegradable and biodegradable microplastics on plant community biomass production and diversity. We employed a fully crossed factorial design to grow the six plant communities in the presence vs. absence of the 10 microplastics individually and in live soil vs. sterilized soil. C_LIO_LIResults show that live soil ameliorated the negative effects of biodegradable microplastics on shoot biomass of the plant communities, but microplastics suppressed plant community diversity more strongly in live soil than in sterilized soil regardless of microplastics types under averaged across all treatments. Furthermore, the specific microplastics polymers were the main drivers of these results. C_LIO_LISynthesis and applications: Overall, our findings indicate that even biodegradable microplastics, e.g. PBS, which are considered environmentally friendly, still pose significant ecological risks to the structure and productivity of plant communities with potential implications for functioning of terrestrial ecosystems. Future studies may identify the specific taxa of soil microorganisms that may have degraded the microplastics that we studied, their rates of biodegradation, and the effects thereof on plant community structure and productivity under more natural field conditions in contrasting climatic conditions. C_LI

ecology↗

bioRxiv2021

Increase in nutrient availability promotes success of invasive plants through increasing growth and decreasing anti-herbivory defenses

Invasive plant species often exhibit greater growth and lower anti-herbivory defense than native plant species. However, it remains unclear how nutrient enrichment of invaded habitats may interact with competition from resident native plants to affect growth and defense of invasive plants. In a greenhouse experiment, we grew five congeneric pairs of invasive and native plant species under two levels of nutrient availability (low vs. high) that were fully crossed with simulated herbivory (clipping vs. no-clipping) and competition (alone vs. competition). Invasive plants produced more gibberellic acid, and grew larger than native species. Nutrient enrichment caused a greater increase in total biomass of invasive plants than of native plants, especially in the absence of competition or without simulated herbivory treatment. Nutrient enrichment decreased leaf flavonoid contents of invasive plants under both simulated herbivory conditions, but increased flavonoid of native plants under simulated herbivory condition. Nutrient enrichment only decreased tannins production of invasive species under competition. For native species, it enhanced their tannins production under competition, but decreased the chemicals when growing alone. The results indicate that the higher biomass production and lower flavonoids production in response to nutrient addition may lead to competitive advantage of invasive species than native species.

ecology↗

bioRxiv2021

Opposite effects of nutrient enrichment and herbivory by an alien snail on growth of an invasive macrophyte and native macrophytes

Human-mediated introduction of plant and animal species into biogeographic ranges where they did not occur before has been so pervasive globally that many ecosystems are now co-invaded by multiple alien plant and animal species. Although empirical evidence of invaders modifying recipient ecosystems to the benefit of other aliens is accumulating, these interactions remain underexplored and underrepresented in heuristic models of invasion success. Many freshwater ecosystems are co-invaded by aquatic macrophytes and mollusks and at the same time experience nutrient enrichment from various sources. However, studies are lacking that test how nutrient enrichment and co-invasion by alien herbivores and plant species can interactively affect native plant communities in aquatic habitats. To test such effects, we performed a freshwater mesocosm experiment in which we grew a synthetic native macrophyte community of three species under two levels of nutrient enrichment (enrichment vs. no-enrichment) treatment and fully crossed with two levels of competition from an invasive macrophyte Myriophyllum aquaticum (competition vs. no-competition), and two levels of herbivory by an invasive snail Pomacea canaliculata (herbivory vs. no-herbivory) treatments. Results show that herbivory by the invasive snail enhanced above-ground biomass yield of the invasive macrophyte. Moreover, the invasive herbivore preferentially fed on biomass of the native macrophytes over that of the invasive macrophyte. However, nutrient enrichment reduced above-ground biomass yield of the invasive macrophyte. Our results suggest that eutrophication of aquatic habitats that are already invaded by M. aquaticum may slow down invasive spread of the invasive macrophyte. However, herbivory by the invasive snail P. canaliculata may enhance invasive spread of M. aquaticum in the same habitats. Broadly, our study underscores the significance of considering several factors and their interaction when assessing the impact of invasive species, especially considering that many habitats experience co-invasion by plants and herbivores and simultaneously undergo varous other disturbances including nutrient enrichment.

ecology↗