ING PAN's video: Part 2 Species as the basic units in evolution and biodiversity by Prof Johann Hohenegger

Biological species as the basic units in biodiversity and evolution unify organisms that are similar in structure, development and ecological demands. This has led to numerous species concepts, where many concepts are based on criteria that can be used only for recognizing species (operational criteria), not defining the ‘being’ or make-up of the species (explanatory criteria). In this lecture, advantages and disadvantages of the main running species concepts are explained. Species can be described as pools of contemporarily interconnected genotypes possessing their own history leading to evolutionary lines. Interconnection in genotypes is expressed by homogeneous phenotypes, but not in a one to one relation. The proof of interconnection by phenotypic homogeneity must be based on the four criteria ‘shape homogeneity’, ‘ontogenetic connection’, ‘homogeneous ecological niches’ and ‘evolutionary continuity’. While in all eukaryonts homogeneities in shape, ecological niches, and the ontogenetic connection can be checked both in living individuals and fossil forms, the detection of birth (speciation), lifetime and death (ending) of a species determining an evolutionary line is only possible in organisms with a fossil record. Speciation can be grouped in split-off and split-up processes. Split-off processes where a daughter species derives from a mother species are easier to recognize than split-up processes where several species originate more or less contemporaneously within a geological time interval. Therefore, it is difficult to delimitate species when they are in a reticulate speciation process where hybridization between subspecies is a common feature. Nevertheless, the four above mentioned criteria enable recognition of species without molecular-genetic investigations. Only the combination of these criteria makes identification of species in the fossil record possible. TO LEARN MORE ON SPECIES CONCEPT PLEASE FOLLOW: - "Part 1" of the same lecture on ING PAN Movie Channel and this paper - Hohenegger, J., 2012. Transferability of genomes to the next generation: the fundamental criterion for the biological species. Zootaxa, 3572, 11-17: http://www.mapress.com/zootaxa/2012/f/z03572p017f.pdf