@article{Wolf2021,
  author    = {Wolf, Matthias},
  title     = {How to teach about what is a species},
  series = {Biology},
  volume    = {10},
  journal   = {Biology},
  number    = {6},
  issn      = {2079-7737},
  doi       = {10.3390/biology10060523},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-241052},
  year      = {2021},
  abstract  = {To ask students what a species is always has something rhetorical about it. Too quickly comes the rote answer, often learned by heart without ever thinking about it: "A species is a reproductive community of populations (reproductively isolated from others), which occupies a specific niche in nature" (Mayr 1982). However, do two people look alike because they are twins or are they twins because they look alike? "Two organisms do not belong to the same species because they mate and reproduce, but they only are able to do so because they belong to the same species" (Mahner and Bunge 1997). Unfortunately, most biology (pre-university) teachers have no opinion on whether species are real or conceptual, simply because they have never been taught the question themselves, but rather one answer they still pass on to their students today, learned by heart without ever thinking about it. Species are either real or conceptual and, in my opinion, it is this "or" that we should teach about. Only then can we discuss those fundamental questions such as who or what is selected, who or what evolves and, finally, what is biodiversity and phylogenetics all about? Individuals related to each other by the tree of life.},
  language  = {en}
}
@article{RybalkaWolfAndersenetal.2013,
  author    = {Rybalka, Nataliya and Wolf, Matthias and Andersen, Robert and Friedl, Thomas},
  title     = {Congruence of chloroplast- and nuclear-encoded DNA sequence variations used to assess species boundaries in the soil microalga Heterococcus (Stramenopiles, Xanthophyceae)},
  series = {BMC Evolutionary Biology},
  volume    = {13},
  journal   = {BMC Evolutionary Biology},
  number    = {39},
  issn      = {1471-2148},
  doi       = {10.1186/1471-2148-13-39},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-121848},
  year      = {2013},
  abstract  = {Background: Heterococcus is a microalgal genus of Xanthophyceae (Stramenopiles) that is common and widespread in soils, especially from cold regions. Species are characterized by extensively branched filaments produced when grown on agarized culture medium. Despite the large number of species described exclusively using light microscopic morphology, the assessment of species diversity is hampered by extensive morphological plasticity. Results: Two independent types of molecular data, the chloroplast-encoded psbA/rbcL spacer complemented by rbcL gene and the internal transcribed spacer 2 of the nuclear rDNA cistron (ITS2), congruently recovered a robust phylogenetic structure. With ITS2 considerable sequence and secondary structure divergence existed among the eight species, but a combined sequence and secondary structure phylogenetic analysis confined to helix II of ITS2 corroborated relationships as inferred from the rbcL gene phylogeny. Intra-genomic divergence of ITS2 sequences was revealed in many strains. The 'monophyletic species concept', appropriate for microalgae without known sexual reproduction, revealed eight different species. Species boundaries established using the molecular-based monophyletic species concept were more conservative than the traditional morphological species concept. Within a species, almost identical chloroplast marker sequences (genotypes) were repeatedly recovered from strains of different origins. At least two species had widespread geographical distributions; however, within a given species, genotypes recovered from Antarctic strains were distinct from those in temperate habitats. Furthermore, the sequence diversity may correspond to adaptation to different types of habitats or climates. Conclusions: We established a method and a reference data base for the unambiguous identification of species of the common soil microalgal genus Heterococcus which uses DNA sequence variation in markers from plastid and nuclear genomes. The molecular data were more reliable and more conservative than morphological data.},
  language  = {en}
}