Invasive alien plants progress to dominate protected and best-preserved wet forests of an oceanic island

Foraging Strategies of Invasive Macaca fascicularis may Promote Plant Invasion in Mauritius

The effectiveness of seed dispersal by frugivorous primates may vary between seasons and plant species, depending on foraging strategies. We investigated how foraging strategies of an invasive frugivorous primate (the long-tailed macaque, Macaca fascicularis) affect seed dispersal effectiveness (SDE) between native and invasive plants in Mauritius’ native remnant forests. By collecting behavioural data on a group of partially habituated macaques via scan sampling from December 2019 until December 2020 (mean 19.2 ± SD 7.3 hours per month), we investigated seasonal patterns in diet, home range, and fruit availability to identify foraging strategies and determine fruit preference. We simultaneously assessed SDE for invasive vs native plants by quantifying native and invasive fruits consumed or dropped intact by macaques during feeding bouts (n = 114). Macaques fed increasingly on ripe invasive fruits and less on other food items as fruit availability increased, due to preference for invasive fruits and disproportionate availability of invasive vs native fruits. When fruit became scarcer, macaques had larger home ranges, increasingly fed on scarce unripe native and invasive fruits, and expanded their diet by eating orchard crops, indicating use of energy-maximizing strategies. Macaques consumed more native than invasive fruits when unripe and commonly destroyed seeds of native fruits, indicating higher SDE for invasive vs native plants. Higher discard rates of unripe compared to ripe fruits further reinforced these differences in SDE. Our results highlight potential facilitation of plant invasion by an invasive primate, due to foraging strategies shaped by the availability of invasive fruits.

Changes in Species and Functional Diversity of the Herb Layer of Riparian Forest despite Six Decades of Strict Protection

The herb layer of temperate forests contributes to long-term forest ecosystem functioning and provisioning of ecosystem services. Therefore, a thorough understanding of its dynamics in the face of environmental changes is essential. This paper focuses on the species and functional diversity of the herb layer of riparian forests to verify how these two community components changed over time and under strict protection. The understory vegetation was surveyed on 42 semi-permanent plots in three time periods between 1960 and 2020. The overall pattern in vegetation changes that related to species richness and diversity, functional structure, and habitat conditions was analyzed using ordination and permutation techniques. We found significant changes in species composition and the functional structure of herbaceous vegetation over the last six decades. Forests were enriched with nutrient-demanding and alien species. A significant increase in functional diversity and the proportion of species with high SLA and canopy height was also observed, whereas changes in habitat conditions were insignificant. The observed trends indicate that the strict protection of forest communities within small and isolated reserves does not fully protect their species composition. Forest reserves should be surrounded by unmanaged forests and spatially connected to allow species mobility.

Colonization During Colonialism: Developing a Framework to Assess the Rapid Ecological Transformation of Mauritius’s Pristine Ecosystem

The colonization of Mauritius exemplifies the role played by humans in altering the ecosystems of remote oceanic islands. This paper focuses on how we study those islands first colonized under the global mantle of colonialism. Here we aim to provide a theoretical framework for historical ecological investigations to disentangle the processes, impacts, and outcomes of colonization during colonialism, considering local, regional, and global drivers. The paper provides a review of existing literature, outlines a proposed research program encompassing paleoecology, paleoclimatology, archeology, and history, and offers details of potential research sites. We present “historical ecology” as a framework to aid future work, and argue that a refined understanding of the impact of human colonization can help create a nuanced chronology of environmental degradation that typifies Mauritius. Such detailed assessment is necessary to inform contemporary ecological conservation efforts. Finally, we argue that narratives of changing ecosystems and practice can help construct “usable pasts,” often missing from historical records, for the multicultural populace of the island.

Drifting away. Seawater survival and stochastic transport of the invasive Carpobrotus edulis

Coastal areas are vulnerable and fluctuating habitats that include highly valuable spaces for habitat and species conservation and, at the same time, they are among the most invaded ecosystems worldwide. Occupying large areas within Mediterranean-climate coastlines, the "ecosystem engineer" Carpobrotus edulis appears as a menace for coastal biodiversity and ecosystem services. By combining the observation, current distribution, glasshouse experiment, and dispersion modeling, we aim to achieve a better understanding of the successful invasion process and potential dispersion patterns of C. edulis. We analyzed the response of plant propagules (seeds and plant fragments) to seawater immersion during increasing periods of time (up to 144 h). After 2 months of growth, plant fragments showed a total survival rate (100%) indicating high tolerance to salinity. During this time, fragment length was increased (up to 60%) and root length was higher than control in all cases. Also, immersed fragments consistently accumulated more biomass than control fragments. After two months of growth, photosynthetic parameters (F_v'/F_m', Φ_NO, and Φ_II) remained stable compared to control fragments. Physiologically, osmolyte and pigment content did not evidence significant changes regardless of immersion time. Based on the capacity of propagules to survive seawater immersion, we modeled the potential transport of C. edulis by combining an oceanic model (ROMS-AGRIF) with a particle-tracking model. Results indicated that propagules may travel variable distances maintaining physiological viability. Our model suggested that short-scale circulation would be the dominant process, however, long-scale circulation of propagules may be successfully accomplished in <6 days. Furthermore, under optimal conditions (southerly winds dominance), propagules may even travel large distances (250 km alongshore). Modeling transport processes, in combination with the dynamics of introduction and expansion, will contribute to a better understanding of the invasive mechanisms of C. edulis and, consequently, to design preventive strategies to reduce the impact of plant invasion.