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Following the footsteps of red deer in the past

Planet Earth has undergone numerous environmental changes associated with climate change. Fluctuations in temperature and precipitation have also affected the distribution of organisms on the planet. What microevolutionary process has one of Europe’s key mammals, the majestic red deer, undergone in the recent past? The results of an international study led by Karolina Doan from the University of Warsaw, which involved evolutionary analyses of a sample of red deer in Central Europe by molecular biologist and zoologist Pavel Hulva from the Department of Zoology, Faculty of Science, Charles University, has recently been published in the Zoological Journal of the Linnean Society.
The red deer (Cervus elaphus) is one of Europe's most widespread and ecologically important species. Its history is also long and rich.
Source: https://pixnio.com, author: Lewis Craig.

The scientists went back 50,000 years to identify the areas in which red deer – one of our most magnificent ungulate species – roamed. To ensure the results were as accurate as possible, the research team used genetic analysis to analyze 501 sequences of cytochrome b (a type of membrane-bound protein) of mitochondrial DNA (mtDNA). As the name suggests, mtDNA is found in the mitochondria and is thus part of the extranuclear genetic information. It is therefore genes that are not found in the nucleus on chromosomes. Genetic analysis is often used to analyze the evolution of populations, with mtDNA being carried exclusively in the maternal line, as opposed to Y-DNA, which is carried in the paternal line. In total, genetics experts newly analyzed 194 ancient and 75 contemporary samples combined with sequences from the gene bank. Some of the samples were also radiocarbon-dated.

Based on Bayesian phylogenetic tree partitioning, the complex including deer was divided into four mtDNA lineages representing four possible species: wapiti (Cervus canadensis), red deer (C. elaphus), Kashmiri deer (C. hanglu), and Sika deer (C. nippon). All ancient samples from this study belonged to wapiti (C. canadensis) and red deer (C. elaphus), with contemporary samples belonging exclusively to red deer (C. elaphus).

Within one species, the scientists identified several haplotypes (variants of mitochondrial DNA that differ in nucleotide sequence). They are also the first researchers to show that Kashmiri deer are sister species to both red deer and wapiti, contradicting earlier findings that this species was a sister species only to red deer. The new discovery was most likely confirmed due to the extensive data set used in this study, not only in terms of the number of samples but also the time scale.

The elk (Cervus canadensis), also known as the wapiti, is a relative of the red deer.
Source: https://flicker.com, author: Maxime Legare-Vezina.

The researchers also found that at some point in time, a divergence occurred between two closely related species, the red deer (Cervus elaphus) and the wapiti deer (Cervus canadensis). The times at which genetic lineages and haplogroups diverged corresponded to large environmental changes associated with stadials (shorter, colder, and drier climatic periods within a single glacial period) and interstadials of the Late Pleistocene. Climatic changes shifted in north-south and east-west directions. Some haplotypes evident before the Last Glacial Maximum periods have not currently been detected, probably indicating the extinction of the population. Based on the dating and localizationlocalization of the samples, the researchers confirmed the presence of red deer in south-eastern Europe and western Asia during the Last Glacial Maximum. Then, as it began to warm slightly, the range of red deer in Europe expanded northwards, while wapiti in Asia shifted more to the south and east. The changes in the range of each deer species were substantial, as the environmental conditions found on the two continents differed significantly over the last 50,000 years.

 Although red deers have been extensively and repeatedly translocated by humans in the past, their current distribution and phylogeographic structure in Eurasia appears to be largely the result of natural processes, the responses of species to Quaternary environmental changes, and the replacement of some mtDNA lineages by other expanding mtDNA lineages.

The study of megafauna, which includes Cervidae species, is of considerable importance to research on planetary ecosystems. The connectivity of large animals, not only with trees, has existed for hundreds of millions of years, and therefore most biotas are adapted to ecosystems where they are present. Thus, rapid changes in their numbers disrupt the ecological balance. Current research into the genetic characteristics of Cervidae species over time and space has taken us a step further in identifying and understanding the processes that have influenced their speciation and phylogeography.

Megafauna is essential for the entire ecosystem. Source: www.flickr.com, author: Mauro Gialdini.

Kateřina Fraindová

Doan, K., et al., 2022. Phylogenetics and phylogeography of red deer mtDNA lineages during the last 50 000 years in Eurasia, Zoological Journal of the Linnean Society, Volume 194, Issue 2, Pages 431–456. 

Published: Jun 23, 2022 06:05 PM

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