Biodiversity cradles and museums segregating within hotspots of endemism

Idiosyncratic patterns of local species richness and turnover define global biodiversity hotspots

Tropical mountains are global biodiversity hotspots, owing to a combination of high local species richness and turnover in species composition. Typically, the highest local richness and turnover levels are implicitly assumed to converge in the same mountain regions, resulting in extraordinary species richness at regional to global scales. We investigated this untested assumption using high-resolution distribution data for all 9,788 bird species found in 134 mountain regions worldwide. Contrary to expectations, the mountain regions with the highest local richness differed from those with the highest species turnover. This finding reflects dissimilarities in the regions' climates and habitat compositions. Forest habitats and humid tropical climates characterize the mountain regions with the highest local richness. In contrast, mountain regions with the highest turnover are generally colder with drier climates and have mostly open habitat types. The highest local species richness and turnover levels globally converge in only a few mountain regions with the greatest climate volumes and topographic heterogeneity, resulting in the most prominent global hotspots for avian biodiversity. These results underline that species-richness hotspots in tropical mountains arise from idiosyncratic levels of local species richness and turnover, a pattern that traditional analyses of overall regional species richness do not detect.

On Psalmopoeus Pocock, 1895 (Araneae, Theraphosidae) species and tarantula conservation in Ecuador

Two novel species of Psalmopoeus Pocock, 1895 are described from the north-western and central-western slopes of the Cordillera Occidental of the Andes mountain range in Ecuador. The new species are easily differentiated from other congeners of Psalmopoeus by spermathecae and male palpal bulb morphology and a comparatively distant distribution to the type localities of the geographically nearest known congeners. The diagnosis of P.ecclesiasticus Pocock, 1093 is revised and updated, considering the novel species and observations on spermatheca of this species. Likewise, an evaluation is provided for the new species in terms of conservation due to the various threats impacting ecosystems and ecosystem services of their type localities. Finally, the importance of theraphosid spiders in Ecuador and South America and their possible conservation requirements are discussed and assessed.

Climate Change Habitat Model Forecasts for Eight Owl Species in the Southwestern US

The high-resolution forecasting of vegetation type shifts may prove essential in anticipating and mitigating the impacts of future climate change on bird populations. Here, we used the US Forest Service Ecological Response Unit (ERU) classification to develop and assess vegetation-based breeding habitat profiles for eight owl species occurring in the foothills and mountains of the Southwestern US. Shifts in mapped habitat were forecast using an ecosystem vulnerability model based on the pre-1990 climate envelopes of ERUs and the Intergovernmental Panel on Climate Change's (IPCC) A1B moderate-emission scenario for the future climate. For five of the eight owl species, the regional breeding habitat extent was projected to decline by at least 60% by 2090. Three species, the boreal owl (Aegolius funereus; at the trailing edge of its distribution), flammulated owl (Psiloscops flammeolus), and northern pygmy-owl (Glaucidium gnoma), were projected to experience the steepest habitat loss rates of 85%, 85%, and 76%, respectively. Projected vegetation shifts overlaid with well-documented flammulated owl breeding populations showed the complete or near complete loss of habitat by 2090 in areas of montane forest currently supporting dense aggregations of owl territories. Generalist or lower-elevation owl species were predicted to be less impacted, while, for the whiskered screech-owl (Megascops trichopsis), the contraction of the current habitat was nearly offset by a projected northward expansion. In general, the results of this study suggest high exposure to climate change impacts for the upper-elevation forest owls of semi-arid Southwestern North America. Long-distance migration and low natal philopatry may prove important to some montane owl populations in adapting to the regional loss of habitat.

Unveiling evolutionary cradles and museums of flowering plants in a neotropical biodiversity hotspot

Colombia, renowned as an important centre of global biodiversity, continues to harbour undiscovered evolutionary hotspots of flowering plants. The altitude-dependent hypothesis suggests that richness patterns are determined by altitude and probably influenced by climate variables. This study employs null models based on a species-level phylogeny of Colombia's flowering plants and their geographical distributions to identify evolutionary hotspots. We explore the potential correlation between elevation, climate variables such as temperature and rainfall, and the location and nature of these hotspots. The findings reveal that evolutionary cradles, which house young endemic species, are predominantly located in the mountainous regions of the Andes. Conversely, evolutionary museums, hosting older endemic species, are found in lowland regions spanning the Caribbean, Orinoco, Amazon and Pacific areas. These results demonstrate a clear elevational segregation of evolutionary hotspots, primarily influenced by temperature, thereby supporting the hypothesis under examination. Furthermore, this study identifies previously unrecognized evolutionary regions, highlighting the limited understanding of Colombia's biodiversity distribution and evolutionary history.

Up and down from North to South: Latitudinal Distribution of Flea Beetle Genera in Continental Africa (Coleoptera, Chrysomelidae, Galerucinae, Alticini)

The distribution of global biodiversity can be investigated based on comprehensive datasets and many methods to process them. The taxonomic diversity of phytophagous insects is typically linked to plant diversity, which increases from temperate to tropical latitudes. In this paper, we explored the latitudinal distribution of the flea beetle genera (Coleoptera, Chrysomelidae, Galerucinae, Alticini) on the African continent. We divided the area into latitudinal belts and looked for possible correlations with the number and types of vegetational divisions, the area of each belt, and the bioclimatic variables. The number of flea beetle genera is related to the number and types of vegetation divisions rather than the area of each belt. Some bioclimatic variables are highly related to the number of genera, which is higher within those belts where climate factors limit the oscillation of temperature over the year and favor high precipitations, especially in the warmest months. These biotic and abiotic factors lead to a two-peak trend in the taxonomic richness of flea beetle genera from north to south. Genera endemic to restricted areas are linked to the presence of high mountain systems and increase the taxonomic richness of the belt they belong to.

Climate Cycles, Habitat Stability, and Lineage Diversification in an African Biodiversity Hotspot

The Eastern Arc Mountains of Tanzania and Kenya, a montane archipelago of 13 uplifted fault blocks (sky islands) isolated by lowland arid savanna, are a center of exceptional biological endemism. Under the influence of humid winds from the Indian Ocean, forests and associated species may have persisted in this region since the final uplift of these blocks in the late Miocene. Today, these mountains are inhabited by a remarkable diversity of bird species. To better understand the evolutionary processes behind this diversity, we combined molecular phylogenetic studies of East African montane birds with paleoclimate modeling of its montane forests. Across its largest lowland barrier, the 125 km between the Usambara and Nguru/Nguu Mountains, 10 of the 14 bird lineages exhibited a phylogeographic break. Using Bayesian methods, we established that at least three periods of forest contraction and expansion affected the diversification of Eastern Arc birds. Habitat distribution models suggest that lower-elevation hills may have acted as stepping-stones connecting isolated highlands to allow for the dispersal of montane forest-dependent species across them. Periods of vicariance during paleoclimatic cycles extending back through the Last Glacial Maximum would have then isolated these populations within the highlands they had reached. The broad distribution of neoendemic species across the mountains of East Africa provides evidence of climate cycling as a driver of lineage diversification. The high incidence of narrow-range endemism of paleoendemic species on the Usambara, Uluguru, and Udzungwa Mountains of this region is harder to explain. Our paleoclimate models retrodicted the persistence of montane forest during climate cycles on several Eastern Arc sky islands but not on the Southern Tanzania Volcanic Highlands. Consistent with recent theoretical work, different rates of local extinction rather than increased rates of lineage diversification may explain the pattern of excessive narrow-range endemism on some sky islands over others. Thus, a regional filtering effect is generated, with paleoendemics maintaining populations through time only in areas where habitat persisted, providing a credible explanation for the dramatic variance in levels of endemism among different East African sky islands.

Biodiversity cradles and museums segregating within hotspots of endemism

The immense concentrations of vertebrate species in tropical mountains remain a prominent but unexplained pattern in biogeography. A long-standing hypothesis suggests that montane biodiversity hotspots result from endemic species aggregating within ecologically stable localities. Here, the persistence of ancient lineages coincides with frequent speciation events, making such areas both 'cradles' (where new species arise) and 'museums' (where old species survive). Although this hypothesis refers to processes operating at the scale of valleys, it remains supported primarily by patterns generated from coarse-scale distribution data. Using high-resolution occurrence and phylogenetic data on Andean hummingbirds, we find that old and young endemic species are not spatially aggregated. The young endemic species tend to have non-overlapping distributions scattered along the Andean treeline, a long and narrow habitat where populations easily become fragmented. By contrast, the old endemic species have more aggregated distributions, but mainly within pockets of cloud forests at lower elevations than the young endemic species. These findings contradict the premise that biogeographical cradles and museums should overlap in valley systems where pockets of stable climate persist through periods of climate change. Instead, Andean biodiversity hotspots may derive from large-scale fluctuating climate complexity in conjunction with local-scale variability in available area and habitat connectivity.