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The pink pigeon (Nesoenas mayeri) is an endemic species of Mauritius that has made a remarkable recovery after a severe population bottleneck in the 1970s to early 1990s. Prior to this bottleneck, an ex situ population was established from which captive-bred individuals were released into free-living subpopulations to increase population size and genetic variation. This conservation rescue led to rapid population recovery to 400-480 individuals, and the species was twice downlisted on the International Union for the Conservation of Nature (IUCN) Red List. We analyzed the impacts of the bottleneck and genetic rescue on neutral genetic variation during and after population recovery (1993-2008) with restriction site-associated sequencing, microsatellite analyses, and quantitative genetic analysis of studbook data of 1112 birds from zoos in Europe and the United States. We used computer simulations to study the predicted changes in genetic variation and population viability from the past into the future. Genetic variation declined rapidly, despite the population rebound, and the effective population size was approximately an order of magnitude smaller than census size. The species carried a high genetic load of circa 15 lethal equivalents for longevity. Our computer simulations predicted continued inbreeding will likely result in increased expression of deleterious mutations (i.e., a high realized load) and severe inbreeding depression. Without continued conservation actions, it is likely that the pink pigeon will go extinct in the wild within 100 years. Conservation rescue of the pink pigeon has been instrumental in the recovery of the free-living population. However, further genetic rescue with captive-bred birds from zoos is required to recover lost variation, reduce expression of harmful deleterious variation, and prevent extinction. The use of genomics and modeling data can inform IUCN assessments of the viability and extinction risk of species, and it helps in

How will organisms cope when forced into warmer-than-preferred thermal environments? This is a key question facing our ability to monitor and manage biota as average annual temperatures increase, and is of particular concern for range-limited terrestrial species unable to track their preferred climatic envelope. Being ectothermic, desiccation prone, and often spatially restricted, island-inhabiting tropical amphibians exemplify this scenario. Pre-Anthropocene case studies of how insular amphibian populations responded to the enforced occupation of warmer-than-ancestral habitats may add a valuable, but currently lacking, perspective. We studied a population of frogs from the Seychelles endemic family Sooglossidae which, due to historic sea-level rise, have been forced to occupy a significantly warmer island (Praslin) than their ancestors and close living relatives. Evidence from thermal activity patterns, bioacoustics, body size distributions, and ancestral state estimations suggest that this population shifted its thermal niche in response to restricted opportunities for elevational dispersal. Relative to conspecifics, Praslin sooglossids also have divergent nuclear genotypes and call characters, a finding consistent with adaptation causing speciation in a novel thermal environment. Using an evolutionary perspective, our study reveals that some tropical amphibians have survived episodes of historic warming without the aid of dispersal and therefore may have the capacity to adapt to the currently warming climate. However, two otherwise co-distributed sooglossid species are absent from Praslin, and the deep evolutionary divergence between the frogs on Praslin and their closest extant relatives (~8 million years) may have allowed for gradual thermal adaptation and speciation. Thus, local extinction is still a likely outcome for tropical frogs experiencing warming climates in the absence of dispersal corridors to thermal refugia.

Lagoonal mangrove ecosystems are vital for carbon capture, protection of coastlines and conservation of biodiversity. Yet, they are decreasing globally at a higher rate than other mangrove ecosystems. In addition to human drivers, local environmental factors influence the functioning of lagoonal mangrove ecosystems, but their importance and combined effects are relatively unknown. Here, we investigate the drivers of mangrove functioning, approximated by mangrove aboveground biomass (AGB), in a protected lagoonal mangrove ecosystem on Aldabra Atoll, Seychelles. Based on a survey of the mangrove forest structure in 54 plots, we estimated that the mean mangrove forest AGB was 82 ± 13 Mg ha−1. The total AGB of the mangrove area (1720 ha) was nearly 140,600 Mg, equivalent to about 66,100 Mg of carbon stored in the standing biomass on Aldabra. To assess the direct and indirect effects of soil nutrient content, water level variation and soil salinity on mangrove AGB, we used a structural equation model. Our structural equation model explained 82 % of the variation in mangrove AGB. The soil nutrient content (concentration of essential macronutrients in the soil column) had the greatest influence on mangrove AGB variation. Additionally, high variation in water level (change in water depth covering a location) increased mangrove AGB by increasing nutrient content levels. Our results highlight the important contribution of Aldabra's lagoonal ecosystem to Seychelles' carbon storage and the role of hydroperiod as a regulator controlling the availability of crucial nutrients needed for the functioning of mangroves within lagoonal systems. We suggest conservation managers worldwide focus on a holistic ecosystem-level perspective for successful mangrove conservation, including the protection and maintenance of nutrient cycling and hydrological processes.

Aldabrachelys gigantea (Aldabra giant tortoise) is one of only two giant tortoise species left in the world and survives as a single wild population of over 100,000 individuals on Aldabra Atoll, Seychelles. Despite this large current population size, the species faces an uncertain future because of its extremely restricted distribution range and high vulnerability to the projected consequences of climate change. Captive-bred A. gigantea are increasingly used in rewilding programs across the region, where they are introduced to replace extinct giant tortoises in an attempt to functionally resurrect degraded island ecosystems. However, there has been little consideration of the current levels of genetic variation and differentiation within and among the islands on Aldabra. As previous microsatellite studies were inconclusive, we combined low-coverage and double-digest restriction-associated DNA (ddRAD) sequencing to analyze samples from 33 tortoises (11 from each main island). Using 5426 variant sites within the tortoise genome, we detected patterns of within-island population structure, but no differentiation between the islands. These unexpected results highlight the importance of using genome-wide genetic markers to capture higher-resolution genetic structure to inform future management plans, even in a seemingly panmictic population. We show that low-coverage ddRAD sequencing provides an affordable alternative approach to conservation genomic projects of non-model species with large genomes.

Mangrove forests, vital for the conservation of biodiversity, protection of coastlines, and carbon capture, are decreasing globally at a rate higher than most other tropical forests. They are threatened by sea level rise, drought and storm surge, especially on low-lying islands where forests are directly exposed to the elements and have limited land area. We investigated changes in the spatial extent of mangroves on Aldabra Atoll, Seychelles – a protected area without direct human pressures, over 21 years using Landsat images. Over the 21-year study period, mean mangrove extent was 1283 ha with an overall net increase of 60 ha (0.23% year-1). The majority of extent changes were small (<2 ha) and contiguous to the existing mangrove extent. We then assessed the relation of mangrove cover change along the lagoon coastline with wave power (rate of energy transfer by waves), using fetch measures and local wind data. We found lower wave power values for stable mangrove areas than for areas that had gained or lost mangroves from 1997 to 2018. We identified wave power thresholds of 2.3 W m-1 for stable mangrove and 7.1 W m-1 for mangrove occurrence. These thresholds might be valuable for assessing threats and sites with the greatest potential for mangrove restoration across similar areas worldwide. Our results highlight the importance of quantifying mangrove extent changes at a local scale to assist with planning for the protection and restoration of this ecologically important habitat, given its vulnerability to the pressures associated with climate change.