Biology subjects

Riano, G.

Publications and source records attributed to Riano, G..

4 recordsLinked to original sources

bioRxiv2023

The origin of a mountain biota: hyper-aridity shaped reptile diversity in an Arabian biodiversity hotspot

Advances in genomics have greatly enhanced our understanding of mountain biodiversity, providing new insights into the complex and dynamic mechanisms that drive the formation of mountain biotas. These include from broad biogeographic patterns, to population dynamics and adaptations to these environments. However, significant challenges remain in integrating these large-scale and fine-scale findings to develop a comprehensive understanding of mountain biodiversity. One significant challenge is the lack of genomic data, particularly in historically understudied arid regions where reptiles are a particularly diverse vertebrate group. We generated de novo genome-wide SNP data for more than 600 specimens and integrated state-of-the-art biogeographic analyses at the community, species and population level. We, thus, provide for the first time, a holistic integration of how a whole endemic reptile community has originated, diversified and dispersed through a mountain range. Our results show that reptiles independently colonized the Hajar Mountains of eastern Arabia 11 times. After colonization, species delimitation methods suggest high levels of within-mountain diversification, supporting up to 49 putative species. This diversity is strongly structured following local topography, with the highest peaks acting as a broad barrier to gene flow among the entire community. Surprisingly, orogenic events do not seem to rise as key drivers of the biogeographic history of reptiles in this system. However, paleoclimate seems to have had a major role in this community assemblage. We observe an increase of vicariant events from Late Pliocene onwards, coinciding with an unstable climatic period of rapid shifts between hyper-arid to semiarid conditions that led to the ongoing desertification of Arabia. We conclude that paleoclimate, and particularly extreme aridification, acted as a main driver of diversification in arid mountain systems which is tangled with the generation of highly adapted endemicity. Our study provides a valuable contribution to understanding the evolution of mountain biodiversity and the role of environmental factors in shaping the distribution and diversity of reptiles in arid regions.

evolutionary biology↗

bioRxiv2022

Species boundaries to the limit: validating species delimitation methods is critical to avoid taxonomic inflation in the genomic era

With the advent of molecular phylogenetics, the number of taxonomic studies unveiling and describing cryptic diversity has greatly increased. However, speciation between cryptic lineages is often defined without evaluating population structure or gene flow, which can lead to false claims of species status and, subsequently, taxonomic inflation. In the present study we focus on the intriguing case of the Arabian gecko Trachydactylus hajarensis (Squamata: Gekkonidae), a species for which cryptic diversity has been previously reported. We generated mitochondrial data (12S rDNA) and genome-wide SNP data (ddRADseq) for 52 specimens to determine phylogenomic relationships, population structure and gene flow within this species. Then, we applied species delimitation methods (SDMs) to evaluate several competing species hypotheses through the Multispecies Coalescent model. Results show that T. hajarensis is comprised by three well-defined lineages, two of them in the Hajar Mountains of eastern Arabia, and one in Masirah Island, in the southeastern coast of Oman. Even though high levels of past introgression and strong mitonuclear discordances were found, current gene flow is scarce with clear boundaries between populations and shallow levels of admixture in the contact zone between lineages. Surprisingly, species tree topology differed between methods and when different individuals were used in downsampled datasets. Conventional SDMs supported up to three putative new species within the group. However, after species validation with the genealogical divergence index (gdi), none of the putative species held. Overall, this study highlights the importance of sample choice, integrative analyses, and validation methods to not incur into taxonomic inflation, providing a set of already available tools to assess and validate population structure, gene flow, and SDMs before describing new species.

evolutionary biology↗

bioRxiv2022

Evolution along allometric lines of least resistance: Morphological differentiation in Pristurus geckos

Species living in distinct habitats often experience unique ecological selective pressures, which can drive phenotypic divergence. However, how ecophenotypic patterns are affected by allometric trends and trait integration levels is less well understood. Here we evaluate the role of allometry in shaping body size and shape diversity in Pristurus geckos utilizing differing habitats. We found that patterns of body shape allometry and integration were distinct in species with different habitat preferences, with ground-dwelling Pristurus displaying the most divergent allometric trend and the strongest integration. There was also strong concordance between static allometry across individuals and evolutionary allometry among species, revealing that body shape differences among individuals were predictive of evolutionary changes across the phylogeny at macroevolutionary scales. This suggested that phenotypic evolution occurred along allometric lines of least resistance, with allometric trajectories imposing a strong influence on the magnitude and direction of size and shape changes across the phylogeny. When viewed in phylomorphospace, the largest rock-dwelling species were most similar in body shape to the smallest ground-dwelling species, and vice versa. Thus, in Pristurus, phenotypic evolution along the differing habitat-based allometric trajectories resulted in similar body shapes at differing body sizes in distinct ecological habitats.

evolutionary biology↗

bioRxiv2022

Genomics reveals introgression and purging of deleterious mutations in the Arabian leopard (Panthera pardus nimr)

Low genetic variation and high levels of inbreeding are usually a consequence of recent population declines in endangered species. From a conservation point of view, it is essential to genetically screen endangered populations to help assess their vulnerability to extinction and to properly create informed management actions towards their conservation efforts. The leopard, Panthera pardus, is a highly generalist predator with currently eight different subspecies inhabiting a wide range of habitats. Yet, genomic data is still lacking for the Critically Endangered Arabian leopard (P. p. nimr). Here, we sequenced the whole genome of two specimens of Arabian leopard and assembled the most complete genomic dataset for leopards to date, including genomic data for all current subspecies. Our phylogenomic analyses show that leopards are divided into two deeply divergent clades, one including the only African subspecies and a second one including all seven subspecies of Asian leopards. Interestingly, the Arabian leopard represents a well-differentiated lineage sister to the rest of Asian subspecies. The demographic history, genomic diversity, Runs of Homozygosity (RoHs), and mutational load in the Arabian leopard indicate a prolonged population decline, which has led to an increase in inbreeding and RoHs, with consequent purging of deleterious mutations. Our study represents the first attempt to genetically inform captive breeding programs for this Critically Endangered subspecies. Still, more genomes, particularly from wild individuals, are needed to fully characterise the genetic makeup of this singular and iconic subspecies.

genomics↗