Abstract
Simple SummaryThe main issues of the report are focused on four items. (1) A combination of nDNA and mtDNA markers best suits the hybrid identification and estimates of genetic introgression between different biological species. (2) The available facts on nDNA and mtDNA diversity seemingly make obvious the introgression presence among many taxa, although, it is evident that introgression may be quite restricted or asymmetric, thus holding at least the “source” taxon (taxa) intact. (3) If we accept that sexually reproducing species in marine and terrestrial realms are introgressed, as it is still evident for many cases, then we should recognize that the biological species concept, in terms of complete lack of gene flow among species, is inadequate due to the fact, that many zoological species are not biological species yet. However, vast modern molecular data proved that with time they definitely become biological species. (4) The recent investigation of fish taxa divergence using central DNA barcoding database shows that most gene trees are, basically, appeared monophyletic and interspecies reticulations are rare.Application of molecular genetic markers appeared to be very fruitful in achieving many goals, including (i) proving the theoretic basements of general biology and (ii) assessment of worldwide biodiversity. Both are provided in the present meta-analysis and a review as the main signal. One of the basic current challenges in modern biology in the face of new demands in the 21st century is the validation of its paradigms such as the synthetic theory of evolution (STE) and biological species concept (BSC). Another of most valuable goals is the biodiversity assessment for a variety of social needs including free web-based information resources about any living being, renovation of museum collections, nature conservation that recognized as a global project, iBOL, as well as resolving global trading problems such as false labeling of species specimens used as food, drug components, entertainment, etc. The main issues of the review are focused on animals and combine four items. (1) A combination of nDNA and mtDNA markers best suits the identification of hybrids and estimation of genetic introgression. (2) The available facts on nDNA and mtDNA diversity seemingly make introgression among many taxa obvious, although it is evident, that introgression may be quite restricted or asymmetric, thus, leaving at least the “source” taxon (taxa) intact. (3) If we consider sexually reproducing species in marine and terrestrial realms introgressed, as it is still evident in many cases, then we should recognize that the BSC, in view of the complete lack of gene flow among species, is inadequate because many zoological species are not biological ones yet. However, vast modern molecular data have proven that sooner or later they definitely become biological species. (4) An investigation into the fish taxa divergence using the BOLD database shows that most gene trees are basically monophyletic and interspecies reticulations are quite rare.
Highlights
DNA barcoding as a common name of the worldwide initiative, iBOL has been used in biology since 2003 [1,2]
This review focuses mainly on four questions: (1) What methods of identification are most appropriate for the detection of hybrids and genetic introgression, or gene flow? (2) What the facts obtained based on markers of mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) do indicate? (3) Is there any evidence in the literature for the consistency of molecular variability in phyletic lines or taxa with biological species concept (BSC)/synthetic theory of evolution (STE)? (4) How often do reticulations and polytomies of gene trees occur, and what is the main information signal revealed by their topology?
The analysis presented here shows that roughly 2/3 cases identified as genetic introgression are, F1 hybrid occurrence and many are evidence for mtDNA spread across species border but for the nuclear genome an admixture did not notice at the sufficient extent
Summary
DNA barcoding as a common name of the worldwide initiative, iBOL has been used in biology since 2003 [1,2] (iBOL, the international barcode of life project; www.ibol.org, accessed on 7 August 2020). Quite a different approach is considered in this study: the species/specimens delimiting ability is explained mainly by the prevalence of the geographical model of speciation in nature This model assumes that organisms can accumulate stochastic mutations and unique nucleotide substitutions in DNA chains due to the formation of daughter populations (taxa) under gene flow break between them. One of the key objectives of this brief review is to answer the question of whether the available molecular genetic data allow generalizations on the wide presence of genetic introgression between biological species and on the frequent occurrence of reticulation in the studied gene trees, and, if the answer is negative, whether these shreds of evidence are consistent with BSC/STE. Most details of these tests are explained in publications cited in the review
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