The Bryoflora of Tabasco, Mexico

Mexico has a rich bryophyte flora; however, some areas still need botanic exploration. Located in southern Mexico, the state of Tabasco is one of the entities with little information about its bryophyte diversity (Delgadillo 1992, 1996). This data is scattered and limited to some specimens deposited in national herbaria and reports in some publications (e.g. Delgadillo y Zamudio, 1988; Sharp et al, 1994).

The main objective of this project is to document the bryophyte diversity of Tabasco. Several studies have been started, and preliminary results are published as a chapter in a synthesis of Tabasco biodiversity by the “Comisión Nacional para el Conocimiento y Uso de la Biodiversidad - CONABIO” (Tabasco biodiversity) .

This research presents the generalities of bryophytes (Chapter - Briofitas) and a checklist of the species recorded for Tabasco (Table S6) .

Figure. Examples of mosses in Tabasco

It is expected to continue with the floristic studies to accurately estimate the bryophyte diversity in Tabasco. This project is mainly led by M.Sc. Ma. Guadalupe Rivas Acuña of the Universidad Juárez Autónoma de Tabasco.

Bryophyte Handbook

The Bryophyte Handbook, also known as "Manual de Briofitas" in Spanish, serves as a comprehensive guide for individuals interested in learning about this group of plants. It provides information to a diverse audience, including biology undergraduates, nature enthusiasts, and anyone seeking to expand their knowledge on bryophytes.

The third edition of this popular publication results from the collaborative efforts of Dr. Claudio Delgadillo Moya and several other Mexican bryologists.

My contribution to this work focused on the genomic research chapter and the generalities of Anthocerotophyta, including a key for identifying the genera found in Mexico.

For those spanish speakers interested in this fascinating group of plants, the "Manual de Briofitas" is freely downloadable at the following link: Manual de Briofitas

Asexual reproduction in epiphytic mosses

Bryophytes can reproduce by spores and asexually by specialized structures (e.g., gemmae, tubers, bulbils) or clonal growth (a division of a genetic individual into new clones). For some bryophyte populations, asexual reproduction is the primary means of environmental persistence.

As part of my Master's research at the National Autonomous University of Mexico (UNAM in spanish), I studied the asexual reproduction of the mosses Calymperes afzelii and Syrrhopodon incompletus in Tabasco, Mexico. My research thesis was elaborated under the supervision of Dr. Claudio Delgadillo Moya. We investigated how variables such as the rain and colony features (shoot density, presence of sexual structures) influence the production of specialized asexual gemmae in mosses of the tropical family Calymperaceae.

Figure. Foliar gemmae of two moss species of the Calymperaceae family.

For detailed information of this research, check the Botanical Science journal. Escolástico & Delgadillo, 2023. Rainfall and gemmiferous shoots influence asexual reproduction in two tropical mosses. Botanical Sciences 101(3):713-724

Phylogeography of Racomitrium lanuginosum

As part of my doctoral dissertation, I studied the evolutionary history and ecology of the northern moss Racomitrium lanuginosum. This study was conducted in collaboration of Lars Hedenäs, Dietmar Quandt, Dörte Harpke, Juan Larraín and Michael Stech

In the first chapter, I tested the following hypotheses : i) this moss consisted of different molecular lineages considered cryptic species by previous studies and ii) the past climatic oscillations of the quaternary affected the genetic diversity of populations.

To test these research hypotheses, I used an integrative approach with Sanger-based markers, genotyping-by-sequencing and species distribution models.

Figure. Phylogenetic network of Racomitrium lanuginosum based on uncorrected P-distances of 4620 concatenated loci shared by at least 20% of 126 samples including R. pruinosum as the outgroup.

The results of this research indicate that the moss Racomitrium lanuginosum has a complex phylogeographic history shaped by cryptic speciation, post-glacial expansion and long-distance dispersal. These patterns contribute to understanding the evolution of arctic and subarctic plants.

The complete research can be found in the Botanical Journal of the Linnean Society. Escolástico et al., 2023. Cryptic speciation shapes the biogeographic history of a northern distributed moss. Botanical Journal of the Linnean Society 201(1):114-134

Decoupling genetic variation in the tundra

Plant genetic variation can be structured in complex patterns where several processes intervene, like cryptic speciation, masking the real diversity across habitats. The consequences of neglecting cryptic species in genetic studies may result in inflation of genetic diversity or a seemingly homogeneous diversity among environments.

This study examines the population genetics and clonality of Racomitrium lanuginosum in the two types of tundra to prove the importance of decoupling genetic variation for an accurate biodiversity assessment in cold environments.

Figure. Racomitrium lanuginosum habitat and growth form. a Whitish mats of R. lanuginosum in the tundra at Umiujaq, Canada. b Close-up of the moss gametophyte. c Details of the shoot (branches) displaying the long hyaline awns. Photos by Catherine Boudreault (a) and Kim Damboise (b,c).

Using genotyping-by-sequencing, we tested for differences in genetic diversity estimates using different clustering scenarios: one species or two cryptic lineages. In addition, we explored the clonal structure of the populations. The correct characterization of cryptic lineages in R. lanuginosum revealed genetic diversity differences between habitats and proved the inflation of genetic estimates when treating differentiated cryptic lineages as a single species.

The results of this project will be released soon.

Moss microbiome and N2-fixation

Bryophytes maintain symbiosis with bacteria, influencing the local nutrient budget. Moss bacterial communities are composed of a core microbiome and bacteria recruited from environmental sources. Notably, symbiotic N₂-fixing bacteria contribute to the N budget in northern ecosystems through biological nitrogen fixation. This process may be affected by the abundance of diazotrophs and moss nutrient content.

To investigate the bacterial and diazotrophic communities associated with the abundant moss Racomitrium lanuginosum, we used amplicon sequencing of the bacterial 16S rRNA and nifH genes and tested whether the moss core microbiome has recruitment from the soil bacteria community in two tundra in Northern Quebec, Canada. We also performed acetylene reduction assays to estimate N₂-fixation and to test for differences between tundra habitats.

Figure. Sampling sites of Racomitrium lanuginosum included in this study. The inset map indicates the location of the two sampling sites in the Quebec province, Eastern Canada, including forest tundra in Kuujjuarapik and shrub tundra in Umiujaq. Photos of each habitat are presented on the left side.

Our results indicate that moss microbial communities between tundra types hosted similar bacterial diversity but differentially abundant groups and characteristic microbial interaction patterns. The relative abundances of dominant diazotrophs are significantly correlated with acetylene reduction rates. The proteobacterial genera Azorhizobium and Rhodomicrobium represent newly reported bacteria associated with N₂-fixation rates in the tundra.

The detailed results are published in the Symbiosis Journal by accessing the article: Escolástico-Ortiz,et al. 2023. Differentially abundant bacteria drive the N₂-fixation of a widespread moss in the forest-tundra transition zone. Symbiosis 90(2):193-211.

Ecogenomics of mining areas for a sustainable Canadian North (GENOSCAN)

Investigating the impacts of mining activities on the soil-plant microbiomes within Arctic and Sub-arctic ecosystems, particularly within the context of climate change, is a crucial endeavor.

As a part of the project Ecogenomics of mining areas for sustainable Canadian North (GENOSCAN), led by Professor Damase Khasa , I conducted genomic analyses on two populations of black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenburg) in Northern Quebec. This work aimed to elucidate the effects of mining activities on plant genetic variation in northern ecosystems.

Microbial ecology in a restoration context

Mining activities affect the environment, particularly soil health, plant communities, and their ecological roles. A sustainable soil reclamation process should consider the stability of plant communities and their microbial interactions. Microbial communities are key for the environment because they can affect the establishment and survival of plants and soil in the face of harsh conditions, such as ecosystems under mining activity influence.

In my postdoctoral research, I will study microbial communities of soils, rhizosphere, plant roots, and tailings to determine the impact of mining activities on soil health. I will particularly focus on the interactions between plants and microorganisms in a restoration context.

This research is supervised by Christine Martineau at the Laurentian Forestry Centre, Natural Resources Canada.