The Pantepui “Lost World”: Towards a Biogeographical, Ecological and Evolutionary Synthesis of a Pristine Neotropical Sky-Island Archipelago

Alpine Extremophytes in Evolutionary Turmoil: Complex Diversification Patterns and Demographic Responses of a Halophilic Grass in a Central Asian Biodiversity Hotspot

Diversification and demographic responses are key processes shaping species evolutionary history. Yet we still lack a full understanding of ecological mechanisms that shape genetic diversity at different spatial scales upon rapid environmental changes. In this study, we examined genetic differentiation in an extremophilic grass Puccinellia pamirica and factors affecting its population dynamics among the occupied hypersaline alpine wetlands on the arid Pamir Plateau in Central Asia. Using genomic data, we found evidence of fine-scale population structure and gene flow among the localities established across the high-elevation plateau as well as fingerprints of historical demographic expansion. We showed that an increase in the effective population size could coincide with the Last Glacial Period, which was followed by the species demographic decline during the Holocene. Geographic distance plays a vital role in shaping the spatial genetic structure of P. pamirica alongside with isolation-by-environment and habitat fragmentation. Our results highlight a complex history of divergence and gene flow in this species-poor alpine region during the Late Quaternary. We demonstrate that regional climate specificity and a shortage of nonclimate data largely impede predictions of future range changes of the alpine extremophile using ecological niche modeling. This study emphasizes the importance of fine-scale environmental heterogeneity for population dynamics and species distribution shifts.

Areas of endemism of Pteridaceae (Polypodiopsida) in Brazil: a first approach

Areas of endemism (AoE) comprise regions host to two or more endemic taxa, whose distributional limits are congruent and not random. These areas are important for two reasons: they comprise the smallest geographic units for biogeographic analyses and they are priority targets for conservation actions. Ferns are a monophyletic group that despite having a wide geographic distribution, concentrates great species richness and endemism in some regions (centres). The southern and southeastern regions of Brazil comprise one of these centres for the Neotropics. This study aims to verify the AoE of Pteridaceae in Brazil and examine whether the results obtained here are congruent with areas already delimited for other groups and whether there is spatial correspondence between the AoE and Conservation Units. To this end, a database was created with collection records of the 205 Pteridaceae species occurring in Brazil based on a review of herbaria. We analysed 23 815 records for 205 Pteridaceae species using Endemicity Analysis (NDM-VNDM), selecting the fill and assumed parameters, and 1°, 2° and 3° grid-cells. The consensus of 158 AoE, using different grid sizes, was calculated, and subsequently, generalized AoE were established. The Guiana Shield, southern Brazil, southeastern Brazil, and southeastern Bahia were considered generalized AoE. These areas correspond to those found for animals and angiosperms, and in previous studies with ferns. Furthermore, two areas, Acre and Mato Grosso do Sul, were recovered only on grids with 2° and 3°. It will be essential to conduct more research to confirm the persistence of both AoE (Acre and Mato Grosso do Sul), especially after expanding sampling. Most endemic species distribution points occur outside protected areas, demonstrating an alarming situation regarding the conservation of these taxa. In addition, fern distribution data could (and should) be used in conservation practices, programmes and policies, given that they are good ecological indicators and that the distribution of ferns may not reflect that of angiosperms and animals.

Relicts in the mist: Two new frog families, genera and species highlight the role of Pantepui as a biodiversity museum throughout the Cenozoic

The iconic mountains of the Pantepui biogeographical region host many early-diverging endemic animal and plant lineages, concurring with Conan Doyle's novel about an ancient "Lost World". While this is the case of several frog lineages, others appear to have more recent origins, adding to the controversy around the diversification processes in this region. Due to its remoteness, Pantepui is challenging for biological surveys, and only a glimpse of its biodiversity has been described, which hampers comprehensive evolutionary studies in many groups. During a recent expedition to the Neblina massif on the Brazil-Venezuela border, we sampled two new frog species that could not be assigned to any known genus. Here, we perform phylogenetic analyses of mitogenomic and nuclear loci to infer the evolutionary relationships of the new taxa and support their description. We find that both species represent single lineages deeply nested within Brachycephaloidea, a major Neotropical clade of direct-developing frogs. Both species diverged >45 Ma from their closest relatives: the first is sister to all other Brachycephaloidea except for Ceuthomantis, another Pantepui endemic, and the second is sister to Brachycephalidae, endemic to the Brazilian Atlantic Forest. In addition to these considerable phylogenetic and biogeographic divergences, external morphology and osteological features support the proposition of two new family and genus-level taxa to accommodate these new branches of the amphibian tree of life. These findings add to other recently described ancient vertebrate lineages from the Neblina massif, providing a bewildering reminder that our perception of the Pantepui's biodiversity remains vastly incomplete. It also provides insights into how these mountains acted as "museums" during the diversification of Brachycephaloidea and of Neotropical biotas more broadly, in line with the influential "Plateau theory". Finally, these discoveries point at the yet unknown branches of the tree of life that may go extinct, due to global climate change and zoonotic diseases, before we even learn about their existence, amphibians living at higher elevations being particularly at risk.

A wide range of South American inselberg floras reveal cohesive biome patterns

Inselbergs are azonal formations found scattered in different biomes globally. The first floristic list focusing on an inselberg in the Brazilian Amazon is presented here. We aimed to investigate floristic and phylogenetic connections among Neotropical inselbergs and analyze whether environmental variables act as a filter of plant lineages. We used a database compiled from 50 sites spanning three main Neotropical biomes (Amazon, 11 sites, Atlantic Forest, 14 sites, and Caatinga, 25 sites) comprising 2270 Angiosperm species. Our data highlight the vastly different inselberg flora found in each biome. The inselberg floras of the Atlantic Forest and Caatinga show closer phylogenetic ties than those seen in the other biome pairs. The phylogenetic lineages found in all three biomes are also strongly divergent, even within plant families. The dissimilarity between biomes suggests that distinct biogeographical histories might have unfolded even under comparable environmental filtering. Our data suggest that the inselberg flora is more related to the biome where it is located than to other factors, even when the microclimatic conditions in the outcrops differ strongly from those of the surrounding matrix. Relative to the other biomes, the flora of the Caatinga inselbergs has the highest level of species turnover. There is a possibility that plants colonized these rather distant inselbergs even when they were found under very different climatic conditions than those in the Amazonian and Atlantic Forest biomes. It is worth noting that none of the studied inselbergs found in the Caatinga biome is protected. In view of the uniqueness and drought-resilient lineages present in each group of inselbergs, along with their vulnerability to destruction or disturbance and their strong connection with water availability, we stress the need to protect this ecosystem not only to conserve plants potentially useful for ecological restoration but also to preserve the balance of this ecosystem and its connections.

Exploring the relationship between soil and plant evolutionary diversity in the Roraima table mountain OCBIL, Guayana Highlands

OCBIL theory aims to develop hypotheses that explain the evolutionary ecology of biota on old, climatically buffered, infertile landscapes (OCBILs). The table mountain OCBILs of the Guayana Highlands are a major centre of Neotropical plant diversity; however, knowledge about the underlying mechanisms of plant community assembly at the mountaintops is still limited. We evaluated the effect of a fine-scale geoenvironmental gradient on the phylogenetic metrics of plant communities on the iconic, highly isolated Roraima table mountain of the Guayana Highlands. We selected three specific geoenvironments: Bonnetia-shrubby rupestrian grassland, peaty rupestrian grassland and sandy rupestrian grassland. We evaluated evolutionary history using species richness and phylogenetic metrics and analysed effects of the soil on phylogenetic metrics using linear models. Of the 55 species surveyed, 40% are endemic to the Guayana Highlands. Bonnetia-shrubby rupestrian grassland showed higher species richness (47) than peaty rupestrian grassland (30) and sandy rupestrian grassland (24). We observed significant differences in phylogenetic diversity and structure among geoenvironments. The highest phylogenetic diversity was found for Bonnetia-shrubby rupestrian grassland and sandy rupestrian grassland. Peaty rupestrian grassland had significantly lower mean pairwise phylogenetic distance and all standardized phylogenetic metrics. The values of standardized phylogenetic metrics were close to zero, suggesting random phylogenetic structure. The linear models revealed that soil texture explained most of the variation in phylogenetic metrics. Our results might be related to the long geological history of tepuis and the accumulation of lineages over tens of millions of years, which supports the OCBIL theory.

Biogeographical patterns of amphibians and reptiles in the northernmost coastal montane complex of South America

We examine, for the first time, biogeographic patterns in a series of tropical montane coastal systems in northern South America. We use amphibians and reptiles, which constitute the most critical communities based upon the prevalence of endemic taxa, to assess the region's biodiversity. The montane coastal system spans an east-west distance of 925 km. It includes peaks ranging from 549 m to 2765 m above sea level and encompasses the montane complexes of northern Venezuela (including Isla de Margarita), an outlier at Santa Marta (Colombia), and ranges on the islands Trinidad and Tobago. The area supports 14 family level amphibian clades and 23 family level reptile clades. Fieldwork, museum specimen surveys, and a literature review suggest that biodiversity decreases at higher elevations. Here we examine the biogeographic patterns in the region to assess the role of the montane systems as possible refugia. We also look at the possible island and sky island effects using data from altitudes >200 m. At lower elevations, we tabulated 294 species, comprising 112 amphibians and 182 reptiles. About 45% of these taxa are endemic or exclusive to different sub-regions. At mid-elevation montane cloud forests, we find a much-reduced biodiversity with a total of 125 species (66 amphibians and 59 reptiles) exclusive or restricted to the region, and few species shared between systems. We find that biogeographical patterns follow a natural topographic disposition above 200 m in elevations. At the lower elevation cut off, there are 118 species (26 amphibians and 92 reptiles) shared among two or more of the studied mountain systems, suggesting a common origin and dispersal events, despite what seem to be topographic barriers. Biogeographical relationships support a topographic disposition of the region with close associations between the islands of Trinidad and Tobago, the Paria Range and the Turimiquire Massif, and close associations between the Sierra Nevada de Santa Marta and the Sierra de San Luis. Overall, the biogeographic relationships between amphibians and reptiles are similar. Species diversity in the eastern Caribbean region is less rich than in the west. This study includes the first herpetological surveys at the two easternmost mountains (Cerro La Cerbatana and Campeare) belonging to the Paria Range biogeographic unit, and aims to contribute to a better understanding of the rich biodiversity of the region.

Species diversity and biogeography of an ancient frog clade from the Guiana Shield (Anura: Microhylidae: Adelastes, Otophryne, Synapturanus) exhibiting spectacular phenotypic diversification

The outstanding biodiversity of the Guiana Shield has raised many questions about its origins and evolution. Frogs of the genera Adelastes, Otophryne and Synapturanus form an ancient lineage distributed mostly across this region. These genera display strikingly disparate morphologies and life-history traits. Notably, Synapturanus is conspicuously adapted to fossoriality and is the only genus within this group to have dispersed further into Amazonia. Moreover, morphological differences among Synapturanus species suggest different degrees of fossoriality that might be linked to their biogeographical history. Through integrative analysis of genetic, morphometric and acoustic data, we delimited 25 species in this clade, representing a fourfold increase. We found that the entire clade started to diversify ~55 Mya and Synapturanus ~30 Mya. Members of this genus probably dispersed three times out of the Guiana Shield both before and after the Pebas system, a wetland ecosystem occupying most of Western Amazonia during the Miocene. Using a three-dimensional osteological dataset, we characterized a high morphological disparity across the three genera. Within Synapturanus, we further characterized distinct phenotypes that emerged concomitantly with dispersals during the Miocene and possibly represent adaptations to different habitats, such as soils with different physical properties.