In recent years, biologists have developed a deeper understanding and concern about how the relationship between genetic diversity can influence the population structure of a species. They have understood how geographic and ecological variations often divide species into subspecies or other distinct populations of individuals that are closely related to each other and not to outsiders. Now, with the help of better tools and techniques for studying genes from wild creatures, researchers are discovering how genetic dynamics within and among those populations can affect their resilience and how they can adapt to changing conditions over time. Some populations can act as refuges or reservoirs of rare genes and become the salvation of a species if new threats appear. But others may become too isolated, may become extinct, and cause fragments of a species’ genetic diversity to disappear forever. For those reasons, it is important to have a good insight into how species can adapt and evolve naturally to help conservation practitioners make better decisions about how to protect and save them.
The biologist Flor de María Morales explains more in her thesis “Diversidad genética de poblaciones de Bolitoglossa helmrichi (Caudata: Plethondotidae) en Alta Verapaz y Baja Verapaz, Guatemala” (Genetic diversity of populations of Bolitoglossa helmrichi (Caudata: Plethodontidae) in Alta Verapaz and Baja Verapaz, Guatemala)
Autora: Licenciada Flor De María Morales Arroyo (2022)
Why study amphibians’ genetic diversity?
Amphibians are good models for investigating genetics of wild populations because they are widely distributed in most ecosystems, easy to sample, often philopatric to breeding sites, generating high levels of population genetic structure, and are a major conservation concern. Particularly in the past decade, genetics have been instrumental in the conservation biology of these cryptic vertebrates, enabling work ranging from the identification of populations subject to identification of cryptic lineages harboring critical genetic variation, to the analysis of genes controlling key life history traits. Mitochondrial DNA has been used to infer evolutionary history of species populations and to track divergence in very closely related data and even within species.
Cobán Climbing Salamander
Bolitoglossa helmrichi (Coban Climbing Salamander) is an endemic species of Guatemala that lives only in the cloud forest of the mountainous area in the southeast of the country. It is commonly found at heights between 1,000 – 2,290 meters above the sea level. This species belongs to the rostrata group that includes other species such as B. cuchumatana, B. engelhardti, and B. rostrata. B. helmrichi was believed to have a restricted distribution at the southwestern of Alta Verapaz and Baja Verapaz. Recent studies have found that it is also found in Sierra de las Minas and some records exist from Zacapa and El Progreso. This species has been considered a complex of species with high levels of morphological similarities and without clear diagnostic characteristics that differentiate the populations. Few studies have been carried out on the genetics of their populations and their status. The last relevant study was carried out in 2010 where a new species called B. zacapensis was described.
Diagram 1. Coloration and morphology in salamanders are characteristics that distinguish between species. In the diagram you can see some of the differences between the populations of Alta Verapaz and Baja Verapaz.
How was the research conducted?
Tissue samples were collected from 40 salamanders in two locations, in the Pamac II Natural Reserve in San Cristóbal Verapaz, Alta Verapaz; and in Ranchitos del Quetzal Natural Reserve, Purulhá, Baja Verapaz. Also included were 6 salamanders preserved from the Herpetology Collection at Arlington University, Texas, which were collected in Chicamán, Quiché. The study was authorized, endorsed, and reviewed by the Ethics Committee of the Universidad del Valle de Guatemala. DNA was extracted from all the collected samples and the sequences of the 16S, and cytochrome B genes were amplified. With the sequences, haplotype network constructions, phylogenetic reconstructions, and genetic differentiation indices were generated. In addition, ecological niche modeling was generated based on historical climate variables using the location of the collected samples and the known distribution of the species.
Diagram 2. Representation of how salamander tissue was sampled. This procedure was approved by the Ethics Committee of the Universidad del Valle de Guatemala.
What was found, suggested, and recommended?
The result of the genetic diversity analyzes established high differentiation between the sampled populations, with the population of Alta Verapaz being the most diverse. The most different population was Baja Verapaz, which establishes that there is less connectivity and gene flow with other populations. In the phylogenetic reconstructions, a separation of the Alta Verapaz and Quiché populations from the rest of the analyzed sequences was evident. This represents the possibility of two new species and therefore it is necessary to expand both the sampling locations and the number of salamanders sampled to corroborate this discovery. Likewise, it is important to complement data based on mitochondrial genes with nuclear markers and microsatellites to generate more robust conclusions. This will allow the new possible species related to Bolitoglossa helmrichi and the rostrata group to be correctly described. Finally, the ecological niche analysis established that the maximum temperatures of the warmest month and the warmest quarter, the stationary precipitation, and the precipitation of the driest month are the most important bioclimatic variables that determine and limit the distribution of the populations of this species. Therefore, it is important to take these variables into account to understand future isolation patterns and colonization routes used in this group of salamanders and to establish appropriate conservation plans for their populations.
Figura 1. Specimens observed in the field. Examples of differences in coloration and other morphological characteristics.
Acknowledgements by Flor Morales Arroyo
I mainly thank my parents for supporting me throughout the entire process of my degree and for supporting me in this huge project. To my main advisor, Alejandra Zamora, who has always shown interest, time, and advice from the conception of the project to its development. She has been the one who has taught me what I like most about research in this science. To Zabdi López, for his advice about biogeography and the analysis made. To Marcelo Serrano and his family for opening the doors to me to carry out sampling at the Reserva Pamac II. To Edna Álvarez and the workers of Reserva Natural Ranchitos del Quetzal for joining this project and their support during the sampling. To my classmates and friends from the university who also joined in to carry out field sampling, especially Hellen Dahinten who was on each of the trips made. To the Universidad del Valle de Guatemala (UVG) and the Department of Biology for allowing me to develop the project in the laboratories and for being my home for professional training.
Finally, I feel very grateful to FLAAR Mesoamerica for opening its platforms to share this work of research and disclose science to all types of audiences. I hope this continues to be achieved for many years and that the population interested in nature and conservation continues to grow.
Figure 2. Field trip team and sampling of salamanders in the cloud forest of the Pamac II Natural Reserve, San Cristóbal Verapaz, Alta Verapaz.
Written by Flor Morales Arroyo.
Find out more about this research, click on the following link to get access to the thesis:
Notes and concepts
DNA (Deoxyribonucleic Acid) is the molecule that carries genetic information for the development and functioning of an organism.
Ecological Niche is the match of a species to a specific environmental condition and it’ defined by the resources that it requires to survive.
Gene is the unit of heredity which is transferred from a parent to offspring and is held to determine some characteristics of the offspring.
Gene flow is the introduction of genetic material from one population of a species to another, thereby changing the composition of the gene pool of the receiving population.
Genetic differentiation occurs when there is restricted gene flow between populations caused by geographic or ecological factors that restrict gene dispersal.
Haplotype network construction is a widely used approach for analyzing and visualizing the relationships among DNA sequences within a population or species.
Phylogeny is the history of the evolution of a species group, especially about lines of descent and relationships among broad groups of organisms.
Population is a group of organisms of one species that interbreed and live in the same place at the same time.