Santiago Ramírez-BarahonaUniversidad Nacional Autónoma de México | UNAM · Department of Botany
Santiago Ramírez-Barahona
PhD
Associate Professor
About
41
Publications
32,256
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Introduction
I am specially interested in the ecological, geographical and historical factors that influence species and gene diversities at different spatial scales. For this, I'm studying different aspects of plant evolution, from genetic structure within and among populations to species diversification among lineages, community composition and distribution patterns.
ramirezbarahona.com
Additional affiliations
September 2018 - present
Position
- Research Associate
Description
- Molecular Systematics of ferns
September 2016 - August 2018
Position
- PostDoc Position
Description
- Origins and diversification of flowering-plant families.
January 2015 - January 2016
Position
- PostDoc Position
Description
- Evolutionary history, genetic structure and history host-parasite relationships in the hemiparasitic mistletoes Psittacanthus (Loranthaceae).
Publications
Publications (41)
The development of spatial genetic structure (SGS) in seed plants has been linked to several biological attributes of species, such as breeding system and life form. However, little is known about SGS in ferns, which together with lycopods are unique among land plants in having two free-living life stages. We combined spatial aggregation statistics...
Variation in rates of molecular evolution (heterotachy) is a common phenomenon among plants. Although multiple theoretical models have been proposed, fundamental questions remain regarding the combined effects of ecological and morphological traits on rate heterogeneity. Here, we used tree ferns to explore the correlation between rates of molecular...
Climate change is one of the most important threats to biodiversity and crop sustainability. The impact of climate change is often evaluated on the basis of expected changes in species' geographical distributions. Genomic diversity, local adaptation, and migration are seldom integrated into future species projections. Here, we examine how climate c...
The Early Cretaceous (145–100 million years ago (Ma)) witnessed the rise of flowering plants (angiosperms), which ultimately lead to profound changes in terrestrial plant communities. However, palaeobotanical evidence shows that the transition to widespread angiosperm-dominated biomes was delayed until the Palaeocene (66–56 Ma). Important aspects o...
Climate change is a threat to biodiversity. One way that this threat manifests is through pronounced shifts in the geographical range of species over time. To predict these shifts, researchers have primarily used species distribution models. However, these models are based on assumptions of niche conservatism and do not consider evolutionary proces...
We evaluated the microbial diversity and metabolome profile of an uncommon hypersaline elastic microbial mat from Cuatro Ciénegas Basin (CCB) in the Chihuahuan Desert of Coahuila, México. We collected ten samples on a small scale transect (1.5-m) and described its microbial diversity through NGS-based ITS and 16S rDNA gene sequencing. A very low nu...
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The mistletoe Psittacanthus schiedeanus, a keystone species in interaction networks between plants, pollinators, and seed dispersers, infects a wide range of native and non-native tree species of commercial interest. Here, using RNA-seq methodology we assembled the whole circularized quadripartite structure of P. schiedeanus chloroplast genome and...
The origin of flowering plants (angiosperms) was one of the most transformative events in the history of our planet. Despite considerable interest from multiple research fields, numerous questions remain, including the age of the group as a whole. Recent studies have reported a perplexing range of estimates for the crown-group age of angiosperms, f...
Fossil flowers are essential to infer past angiosperm evolutionary processes. The assignment of fossil flowers to extant clades has traditionally relied on morphological similarity and on apomorphies shared with extant taxa. The use of explicit phylogenetic analyses to establish their affinity has so far remained limited. In this study, we built a...
Existing global regionalisation schemes for plants consider the compositional affinities among biotas, but these have not explicitly considered phylogenetic information. Here, we present for the first time, a phytogeographical delineation of the global vascular flora based on species-level evolutionary relationships.
We analysed 8,738,520 geographi...
Global climate change and habitat loss are displacing tropical montane forests along mountain slopes 1–4 . Cloud forests are one of the most diverse and fragile of these montane ecosystems 5–8 , yet little is known about the historical and ongoing impacts of anthropogenic disturbances on these forests. Here we assess historical (1901–2016) changes...
The origin of flowering plants (angiosperms) was one of the most transformative events in the history of our planet. Despite considerable interest from multiple research fields, numerous questions remain, including the age of the group as a whole. Recent studies have reported a perplexing range of estimates for the crown-group age of angiosperms, f...
Anthropogenic greenhouse gas emissions have led to sustained global warming over the last decades ¹ . This is already reshaping the distribution of biodiversity across the world and can lead to the occurrence of large-scale singular events, such as the melting of polar ice sheets 2,3 . The potential impacts of such a melting event on species persis...
The gut microbiota is critical for host function. Among mammals, host phylogenetic relatedness and diet are strong drivers of gut microbiota structure, but one factor may be more influential than the other. Here, we used 16S rRNA gene sequencing to determine the relative contributions of host phylogeny and host diet in structuring the gut microbiot...
Existing global regionalisation schemes for plants consider the compositional affinities among biotas, but these have not considered phylogenetic information explicitly. Incorporating phylogenetic information may substantially advance our understanding of the relationships among regions and the synopsis of biogeographical schemes, because phylogeny...
We evaluated the microbial diversity and metabolomic signatures of a hypersaline elastic microbial mat from Cuatro Cienegas Basin (CCB) in the Chihuahuan Desert of Coahuila, Mexico. We collected ten samples within a small scale (1.5-meters transect) and found a high microbial diversity through NGS-based ITS and 16S rRNA gene sequencing. A very low...
The gut microbiota is critical for host function. Among mammals, host phylogenetic relatedness and diet are strong drivers of gut microbiota structure, but one factor may be more influential than the other. Here, we used 16S rRNA gene sequencing to determine the relative contributions of host phylogeny and host dietary guild in structuring the gut...
The Tehuacán-Cuicatlán Valley, located at the southeast of the state of Puebla and the northeast of the state of Oaxaca in Central Mexico, south of the Trans-Mexican Volcanic Belt (TMVB), is of particular interest for understanding the evolutionary dynamics of arid and semi-arid environments, being one of the main reservoirs of biological diversity...
Variation in leaf morphology is correlated with environmental variables, such as precipitation, temperature and soil composition. Several studies have pointed out that individual plasticity can largely explain the foliar phenotypic differences observed in populations due to climatic change and have suggested that the environment plays an important...
Pleistocene glacial periods have had a major influence on the geographical patterns of genetic structure of species in tropical montane regions. However, their effect on morphological differentiation among populations of cloud forest plants remains virtually unexplored. Here, we address this question by testing whether geographical patterns of morp...
Host specialization after host shifting is traditionally viewed as the pathway to speciation in parasitic plants. However, geographical and environmental changes can also influence parasite speciation, through hybridization processes. Here we investigated the impact of past climatic fluctuations, environment, and host shifts on the genetic structur...
Aim
The formation of the Trans‐Mexican Volcanic Belt (TMVB) played an important role in driving inter‐ and intraspecific diversification at high elevations. However, Pleistocene climate changes and ecological factors might also contribute to plant genetic structuring along the volcanic belt. Here, we analysed phylogeographical patterns of the parro...
Summary
The prevalent view about genetic structuring in parasitic plants is that host-race formation is due to varying degrees of host specificity. However, the relative importance of ecological niche divergence and host specificity to population differentiation remains poorly understood.
We evaluated factors associated with population differentiat...
Background. Cloud forests, characterized by a persistent, frequent or seasonal low- level cloud cover and fragmented distribution, are one of the most threatened habitats, especially in the Neotropics. Tree ferns are among the most conspicuous elements in these forests, and ferns are restricted to regions in which minimum temperatures rarely drop b...
GenBank
Species names and GenBank accession numbers for the specimens included in this study.
Climate comparisons
Variation in species richness across regions and between different groups of organisms is a major feature of evolution. Several factors have been proposed to explain these differences, including heterogeneity in the rates of species diversification and the age of clades. It has been frequently assumed that rapid rates of diversification are coupled...
List last updated January 2016.
Nomenclatural issues are still unresolved for the majority of species. Many names were kept from the original species description and therefore do not reflect generic delimitations.
Background: Ecological adaptation to host taxa is thought to result in mistletoe speciation via race formation. However, historical and ecological factors could also contribute to explain genetic structuring particularly when mistletoe host races are distributed allopatrically. Using sequence data from nuclear (ITS) and chloroplast (trnL-F) DNA, we...
The patterns of geographic differentiation in fern species have been linked to climatic differences across regions and the distribution of available habitat. In this paper, the association between some climatic features and patterns of geographic differentiation in American tree ferns was evaluated. For this, the occurrence ranges of 190 species we...
Aim. We investigated changes in distribution of cloud forests during the last 130 kyr, and tested whether these changes explain the spatial patterns of genetic diversity of the tree fern Alsophila firma (Cyatheaceae), a species restricted to this habitat.
Location. Mexican cloud forests.
Methods. We sampled 204 individuals from 16 localities. Genet...
Recent years have witnessed the advent and rapid development of massive sequencing technology, commonly known as Next Generation Sequencing (NGS). This technology allows for rapid, massive and inexpensive sequencing of genome regions or entire genomes, making possible genomic studies of non-model organisms and has seen great progress in metagenomic...
In this study we describe a prokaryotic community from a seawater sample obtained in the Yucatan Channel, using for this purpose three molecular methods: 1) T-RFLPs. 2) Sequencing of amplicons (clone libraries). 3) Metagenome shotgun sequencing; the three are useful for the determination of microbial diversity. We also present a comparison of the s...
The increasing aridity during the Last Glacial Maximum (LGM) has been proposed as a major factor affecting Neotropical species. The character and intensity of this change, however, remains the subject of ongoing debate. This review proposes an approach to test contrasting paleoecological hypotheses by way of their expected demographic and genetic e...
Analyses of richness and endemism of Cyatheales (tree ferns) in tropical America were performed and evidence of a diversity
gradient is presented. For this, the occurrence ranges of 239 species were plotted into a 5° × 5° grid-cell map and then analyzed
using species richness and endemism indices. Here we show that species richness and endemism are...
Based on known data sets and maximum entropy distribution data of fern and lycopod species registered in the Yucatán Peninsula, track and parsimony analyses were undertaken to evaluate the contribution of these groups to the establishment of biogeographical relationships of the peninsula with other areas. The resulting generalized tracks clearly ag...
Projects
Projects (4)
En este proyecto proponemos obtener el genoma del muérdago Psittacanthus auriculatus (Loranthaceae), especie endémica a Oaxaca. Nuestra propuesta transformará el entendimiento del genoma de plantas parásitas y de sistemas no-modelo. El objetivo principal es examinar la historia evolutiva del hemiparasitismo en Psittacanthus, iniciando con la obtención del genoma de P. auriculatus, y luego mediante secuenciación adicional a menor cobertura, conocer la variación genómica entre individuos en distintos hospederos y comparar dicha variación genómica entre varias especies de Psittacanthus con énfasis en los genes candidatos asociados a la formación del haustorio, y a las respuestas a ambientes áridos y cambios de hospedero. El estudio también permitirá evaluar la evolución de la pérdida estacional de hojas en ambientes áridos y evolución de la suculencia, cambios en el haustorio asociados al cambio de hospedero, sistemas reproductivos y polinización. Esperamos observar una fuerte señal de selección en el genoma donde familias génicas estarán asociadas a cambios de hospedero a nivel inter-específico que impliquen retos adaptativos como la formación del haustorio de una especie de Bursera a una especie de Pinus o la colonización de un desierto a partir de un ambiente más húmedo. Al adaptarse de manera local a ciertos hospederos, a partir de un incremento en la especificidad de hospedero y eventual formación de razas, la señal de selección en las familias génicas relacionadas con la formación del haustorio será más fuerte en las especies de Psittacanthus que han cambiado de familia de hospedero o de ambiente a lo largo de su evolución.
To understand the effects of past and future climate change on the geographical distribution of species and its impact on community composition, population divergence (morphological and ecological) and local adaptation.
The main goal is to describe the patterns of species diversity and study the factors and mechanisms associated with species diversification in tree ferns. For this, we are studying geographical patterns of ecological, morphological and genetic variation at different spatial scales. We are also exploring the factors associated with heterogeneity in the rates of molecular evolution and species diversification in the group.
