The main aim of this paper is to address consequences of climate warming on loss of habitat and genetic diversity in the enigmatic tropical alpine giant rosette plants using the Ethiopian endemic Lobelia rhynchopetalum as a model. We modeled the habitat suitability of L. rhynchopetalum and assessed how its range is affected under two climate models and four emission scenarios. We used three statistical algorithms calibrated to represent two different complexity levels of the response. We analyzed genetic diversity using amplified fragment length polymorphisms and assessed the impact of the projected range loss. Under all model and scenario combinations and consistent across algorithms and complexity levels, this afro‐alpine flagship species faces massive range reduction. Only 3.4% of its habitat seems to remain suitable on average by 2,080, resulting in loss of 82% (CI 75%–87%) of its genetic diversity. The remaining suitable habitat is projected to be fragmented among and reduced to four mountain peaks, further deteriorating the probability of long‐term sustainability of viable populations. Because of the similar morphological and physiological traits developed through convergent evolution by tropical alpine giant rosette plants in response to diurnal freeze‐thaw cycles, they most likely respond to climate change in a similar way as our study species. We conclude that specialized high‐alpine giant rosette plants, such as L. rhynchopetalum, are likely to face very high risk of extinction following climate warming.

Human population expansion and associated degradation of the habitat of many wildlife species cause loss of biodiversity and species extinctions. The small Simen Mountains National Park in Ethiopia is one of the last strongholds for the preservation of a number of afro-alpine mammals, plants and birds, and it is home to the rare endemic Walia ibex, Capra walie. The narrow distribution range of this species as well as potential competition for resources with livestock, especially with domestic goat, Capra hircus, may compromise its future survival. Based on a curated afro-alpine taxonomic reference library constructed for plant taxon identification, we investigated the diet of the Walia ibex and addressed the dietary overlap with domestic goat using DNA metabarcoding of faecal samples. Faeces of both species were collected from different localities in the National Park. We show that both species are browsers, with forbs, shrubs and trees comprising the largest proportion of their diet, supplemented by grasses. There was a considerable overlap in dietary preferences. Several of the preferred diet items of the Walia ibex (Alchemilla sp., Hypericum revolutum, Erica arborea and Rumex sp.) were also among the most preferred diet items of the domestic goat. These results indicate that there is potential for competition between the two species, especially during the dry season, when resources are limited. Our findings, in combination with the expected increase in domestic herbivores, suggest that management plans should consider the potential threat posed by domestic goats to ensure future survival of the endangered Walia ibex.

The tropical alpine ecosystem in eastern Africa is highly fragmented among biological 'sky islands', where populations of frost-tolerant organisms are isolated from each other by a 'sea' of tropical lowlands. One-third of the species in the afroalpine flora are exclusively alpine, but the other species can to varying degrees extend into grasslands and open forests of lower vegetation belts. A long-debated question is whether colonization of the alpine zone of these mountains and subsequent intermountain gene flow entirely depend on long-distance dispersal across unsuitable habitats, or whether suitable habitats shifted far enough downslope under past colder climates to form bridges enabling gradual migration. Here we address this question using a classification tree model. We mapped the extent of the current alpine habitat and projected it to the last glacial maximum (LGM) climate to assess whether gradual migration was possible for exclusively alpine taxa during this glacial period, and thus potentially also during earlier Pleistocene glaciations. Next, we modelled landcover under current and LGM climates to assess whether grassland and open forests could have served as migration corridors for alpine taxa that today extend into lower vegetation belts. We estimated that the LGM treeline was about 1,000 m lower and the alpine habitat was about eight times larger than today. At the LGM, we found that most of the currently fragmented alpine habitat of the Ethiopian highlands was interconnected except across the Great Rift Valley, whereas the solitary mountains of East/Central Africa remained isolated for exclusively alpine species. However, for drought-tolerant alpine species that today extend below the treeline, gradual migration through habitat corridors may have been possible among mountains during the dry glacial periods, and possibly also under the current climate before agriculture transformed the low-lying landscapes.

The link between the successful establishment of alien species and propagule pressure is well‐documented. Less known is how humans influence the post‐introduction dynamics of invasive alien populations. The latter requires studying parallel invasions by the same species in habitats that are differently impacted by humans. We analysed microsatellite and genome size variation, and then compared the genetic diversity and structure of invasive Poa annua L. on two sub‐Antarctic islands: human‐occupied Marion Island and unoccupied Prince Edward Island. We also carried out niche modelling to map the potential distribution of the species on both islands. We found high levels of genetic diversity and evidence for extensive admixture between genetically distinct lineages of P. annua on Marion Island. By contrast, the Prince Edward Island populations showed low genetic diversity, no apparent admixture, and had smaller genomes. On both islands, high genetic diversity was apparent at human landing sites, and on Marion Island, also around human settlements, suggesting that these areas received multiple introductions and/or acted as initial introduction sites and secondary sources (bridgeheads) for invasive populations. More than 70 years of continuous human activity associated with a meteorological station on Marion Island led to a distribution of this species around human settlements and along footpaths, which facilitates ongoing gene flow among geographically separated populations. By contrast, this was not the case for Prince Edward Island, where P. annua populations showed high genetic structure. The high levels of genetic variation and admixture in P. annua facilitated by human activity, coupled with high habitat suitability on both islands, suggest that P. annua is likely to increase its distribution and abundance in the future.

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