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Biodiversity studied by researching island species recovery and management.

Constraints on evolutionary adaptation and range shifts mean that phenotypic plasticity, which includes physiological, developmental or behavioural responses to environmental conditions, could be an important mode of adaptation to a changing climate for many species with small insular populations. While there is evidence to suggest adaptive plasticity to climate in some island populations, little is known about this capacity in species that have experienced a severe population bottleneck. In a changing climate, plasticity in the timing of life-history events, such as in breeding phenology, is adaptive if timing is optimised in seasonal environments, although these processes are poorly understood for tropical species. Here, we quantify the effects of climate on the breeding phenology and success of the Mauritius kestrel (Falco punctatus), a tropical raptor whose extinction has been averted by conservation management. We show that the timing of egg-laying is advancing in response to warming, at rates similar to temperate bird populations. Individual females show plasticity to temperature, although there is limited variation among individual responses. We show that advances in breeding phenology are likely to be adaptive, as they track changes in a seasonal climate window of favourable conditions, defined by late winter-early spring temperatures and the onset of the summer rainy season. Our results provide a rare example of a small and bottlenecked insular population that has adjusted to recent climate change through phenotypic plasticity. Furthermore, seasonal climate windows and their dynamics may be widespread mechanisms through which tropical species are impacted by and respond to climate change.

Given the pressing biodiversity crisis and the limited resources made available to support conservation, impact evaluation is crucial in understanding the effectiveness of conservation strategies. The use of experimental and quasi‐experimental methods of impact evaluation in conservation continues to grow, but they are not always compatible with conservation projects. The IUCN Green Status of Species (GSS) provides a qualitative, inferential approach to evaluate the past and potential future impacts of conservation. Using the GSS, we present the impact of conservation on 10 species endemic to Mauritius (six reptiles, three birds and one tree). Like many island ecosystems, Mauritius has experienced extensive habitat destruction and biodiversity loss in recent centuries, and has therefore been the site of decades of conservation conducted in collaboration between governmental and non‐governmental organizations, both local and international. Using inferential, qualitative approaches to generate counterfactual scenarios, we explored the impact to date of conservation in Mauritius on species extinctions and species' ongoing dependence on conservation. We found that conservation efforts have prevented extinction in all but one species assessed, with the counterfactual scenarios taking into account the effects of conservation actions including biosecurity measures, invasive species control, habitat restoration, and species reintroduction. The results quantifying the assessed species' dependence on continued conservation action were more varied, with the reptiles assessed in this study being more reliant on continued conservation than the other taxa assessed. The findings of this study demonstrate using a real‐world case study how the IUCN Green Status of Species and the associated counterfactual analysis can be used to understand and communicate conservation impact. We show the high impact of past conservation actions and the importance of their continuation. We attribute the successful outcomes we observed to long‐term investment in conservation programs and highlight this as an important consideration to deliver positive outcomes. The IUCN Green Status of Species uses a qualitative and inferential approach to evaluate the past and expected future impacts of conservation on species recovery. Using this approach, we demonstrate the impact of a long‐term, multi‐organization conservation program in Mauritius in preventing the extinction of nine species, and the importance of continued conservation. We demonstrate the value of long‐term commitment to conservation programs in driving species and ecosystem recovery.

Background In migratory species, the extent of within- and between-individual variation in migratory strategies can influence potential rates and directions of responses to environmental changes. Quantifying this variation requires tracking of many individuals on repeated migratory journeys. At temperate and higher latitudes, low levels of within-individual variation in migratory behaviours are common and may reflect repeated use of predictable resources in these seasonally-structured environments. However, variation in migratory behaviours in the tropics, where seasonal predictability of food resources can be weaker, remains largely unknown. Methods Round Island petrels ( Pterodroma sp.) are tropical, pelagic seabirds that breed all year round and perform long-distance migrations. Using multi-year geolocator tracking data from 62 individuals between 2009 and 2018, we quantify levels of within- and between-individual variation in non-breeding distributions and timings. Results We found striking levels of between-individual variation in at-sea movements and timings, with non-breeding migrations to different areas occurring across much of the Indian Ocean and throughout the whole year. Despite this, repeat-tracking of individual petrels revealed remarkably high levels of spatial and temporal consistency in within-individual migratory behaviour, particularly for petrels that departed at similar times in different years and for those departing in the austral summer. However, while the same areas were used by individuals in different years, they were not necessarily used at the same times during the non-breeding period. Conclusions Even in tropical systems with huge ranges of migratory routes and timings, our results suggest benefits of consistency in individual migratory behaviours. Identifying the factors that drive and maintain between-individual variation in migratory behaviour, and the consequences for breeding success and survival, will be key to understanding the consequences of environmental change across migratory ranges.

Plastic pollution is distributed patchily around the world’s oceans. Likewise, marine organisms that are vulnerable to plastic ingestion or entanglement have uneven distributions. Understanding where wildlife encounters plastic is crucial for targeting research and mitigation. Oceanic seabirds, particularly petrels, frequently ingest plastic, are highly threatened, and cover vast distances during foraging and migration. However, the spatial overlap between petrels and plastics is poorly understood. Here we combine marine plastic density estimates with individual movement data for 7137 birds of 77 petrel species to estimate relative exposure risk. We identify high exposure risk areas in the Mediterranean and Black seas, and the northeast Pacific, northwest Pacific, South Atlantic and southwest Indian oceans. Plastic exposure risk varies greatly among species and populations, and between breeding and non-breeding seasons. Exposure risk is disproportionately high for Threatened species. Outside the Mediterranean and Black seas, exposure risk is highest in the high seas and Exclusive Economic Zones (EEZs) of the USA, Japan, and the UK. Birds generally had higher plastic exposure risk outside the EEZ of the country where they breed. We identify conservation and research priorities, and highlight that international collaboration is key to addressing the impacts of marine plastic on wide-ranging species.

Ecological replacement involves the introduction of non-native species to habitats beyond their historical range, a factor identified as increasing the risk of failure for translocations. Yet the effectiveness and success of ecological replacement rely in part on the ability of translocatees to adapt, survive and potentially reproduce in a novel environment. We discuss the welfare aspects of translocating captive-reared non-native tortoises, Aldabrachelys gigantea and Astrochelys radiata, to two offshore Mauritian islands, and the costs and success of the projects to date. Because tortoises are long-lived, late-maturing reptiles, we assessed the progress of the translocation by monitoring the survival, health, growth, and breeding by the founders. Between 2000 and 2011, a total of 26 A. gigantea were introduced to Ile aux Aigrettes, and in 2007 twelve sexually immature A. gigantea and twelve male A. radiata were introduced to Round Island, Mauritius. Annual mortality rates were low, with most animals either maintaining or gaining weight. A minimum of 529 hatchlings were produced on Ile aux Aigrettes in 11 years; there was no potential for breeding on Round Island. Project costs were low. We attribute the success of these introductions to the tortoises' generalist diet, habitat requirements, and innate behaviour. Feasibility analyses for ecological replacement and assisted colonisation projects should consider the candidate species' welfare during translocation and in its recipient environment. Our study provides a useful model for how this should be done. In addition to serving as ecological replacements for extinct Mauritian tortoises, we found that releasing small numbers of captive-reared A. gigantea and A. radiata is cost-effective and successful in the short term. The ability to release small numbers of animals is a particularly important attribute for ecological replacement projects since it reduces the potential risk and controversy associated with introducing non-native species.

In this study, we investigate community structure in day geckos (genus Phelsuma) in the Indian Ocean. Much of what we know about communities of diurnal arboreal lizards comes from studies of Caribbean Anolis. Phelsuma in the Indian Ocean are ecologically similar to Anolis but not closely related. Using field observations and an experiment, we test three hypotheses for Phelsuma communities, all derived from work on Anolis: (1) Phelsuma species richness will be correlated with the diversity of available perches, (2) sympatric species will partition their habitat use, shifting their habitat use depending on which other species of Phelsuma are present, and (3) experimentally removing individuals of one species will lead to changes in the microhabitat use and/or abundance of sympatric congeners. We find support for all three hypotheses. We also describe some unique aspects of Phelsuma communities, such as partitioning of palm vs. non-palm trees. This study identifies some potentially general features of diurnal arboreal lizard communities, and suggests that some aspects of community assembly might be repeatable.

The classification of petrels (Pterodroma spp.) from Round Island, near Mauritius in the Indian Ocean, has confounded researchers since their discovery in 1948. In this study we investigate the relationships between Round Island petrels and their closest relatives using evidence from mitochondrial DNA sequence data and ectoparasites. Far from providing clear delimitation of species boundaries, our results reveal that hybridization among species on Round Island has led to genetic leakage between populations from different ocean basins. The most common species on the island, Pterodroma arminjoniana, appears to be hybridizing with two rarer species (P. heraldica and P. neglecta), subverting the reproductive isolation of all three and allowing gene flow. P. heraldica and P. neglecta breed sympatrically in the Pacific Ocean, where P. arminjoniana is absent, but no record of hybridization between these two exists and they remain phenotypically distinct. The breakdown of species boundaries in Round Island petrels followed environmental change (deforestation and changes in species composition due to hunting) within their overlapping ranges. Such multi-species interactions have implications not only for conservation, but also for our understanding of the processes of evolutionary diversification and speciation.

Aims To investigate effects of introduced honey bees, Apis mellifera L., on the nectar-feeding activity of two species of endemic nectarivorous birds, the Grey White-eye, Zosterops borbonicus mauritianus Gmelin, and the Olive White-eye, Z. chloronothos Viellot, on two endemic flowering trees, Sideroxylon cinereum Lam. and S. puberulum DC. (Sapotaceae), and to examine pollination efficiency of birds and honey bees. Location An upland heath area on the island of Mauritius, Indian Ocean. Methods We quantified visitation rates of endemic birds and introduced honey bees at two endemic species of flowering trees. Diurnal variation in nectar standing crop and nectar production was measured. Pollination efficiency of flower visitors was examined using bagging and caging experiments. Results White-eyes were only nectar-feeding at the two Sideroxylon species early in the morning, stopping when honey bee foraging activity rapidly lowered nectar standing crops. White-eyes continued nectar-feeding at other flowering plant species, exploited less by honey bees, throughout the day. Honey bees were less efficient pollinators of the two Sideroxylon species than white-eyes. Main conclusions Our results indicate that introduced honey bees could be interfering with endemic interactions between the two Sideroxylon species and the two white-eye species. However, because of lack of a neutral control site without honey bees, we cannot exclude other explanations. We do recommend, although, that honey bees need to be taken into consideration in the future conservation management of Mauritian ecosystems. We suggest that island ecosystems are especially vulnerable to introduced honey bees.