Species concepts

Ziqtara, M.S. and Lumme, J. (2003) The crossroads of molecular, typological and biological species concepts two new species of Cyrodactylus Nordmann, 1832 (Monogenea Gyrodactylidae). Systematic Parasitology 55, 39-52. 

Hybridization has retained oaks a model taxon for species concepts that rely on ecological criteria rather than on reproductive isolation [65]. The high similarity in chemical constitution of different oak pollens, which is verified by a very similar biochemical fingerprint in our Raman experiments, can be interpreted as part of the very weak barriers to being pollinated by another (oak) species. 

Wood AM, Leatham T (1992) The species concept in phytoplankton ecology. J Phycol 28 723-729 Zingone A, Cretiennot-Dinet MJ, Lange M, Medlin LK (1999) Morphological and genetic characterisation of... 

A linear algebraic system of rate equations for the fast species results, which can be solved a priori. Hence a strongly reduced (in the number of species to be treated) system is obtained. This concept originates from astrophysical applications and from Laser physics. It is in some instances also referred to as collisional-radiative approximation , for the fast species, lumped species concept , bundle-n method or intrinsic low dimensional manifold (ILDM) method in the literature. We refer to [9,12,13] for further references on this. 

An interesting detail of the quasi-species concept was predicted more than twelve years ago [24] and has been observed recently with virus populations [25] and computer simulations [26] We assume two genotypes of high fitness, each one surrounded by a specific mutant doud (Fig. 2.5). Genotype Iml has higher fitness compared to Im2 but less efficient mutants in the sense of a mutant cloud with lower mean fitness. The quasi-species considered as a function of the mutation rate p may show a rearrangement reminiscent of a phase transition at some critical replication accuracy qa = 1 - pCT. At low mutation rates, p>pCI, the difference in fitness values determines selection and hence, the master sequence with higher fitness, fml, dominates. Above the critical mutation rate, p>pCI, however, mutational backflow to the master is decisive and then fm2 is selected. 

Germond, J-E, Lapierre, L., Delley, M., Mollet, B., Felis, G.E., Dell aglio, F. (2003). Evolution of the bacterial species lactobacillus delbmeckii a partial genomic study with reflections on prokaryotic species concept. Mol. Biol. Evol, 20, 93-104. 

A tremendous change in the deterministic concept of a Darwinian system is brought about by the quasi-species concept. Let us confront the current interpretation with the classical one. 

The units one has to work with, the taxa from low to high, may be fixed, about the contents of these concepts a number of questions can be asked. Partly these questions are philosophical (does a species, a genus really exist in nature or only in the human mind ), partly they are quite practical (to which criteria must species, genera etc. answer ). Especially about the species concept there has been a lot of discussion and opinions did and do differ. For many a species is a unit that has to be morphologically recognizable with preferentially two constant differences with other species, for others the species is more or leas identical with the hybridization com-munity. Genet.ical "identity" of the components of a species is an important criterium and may lead some to forbid different chromosome numbers within one species. The battle about "biological and "taxonomical or less clear event linnean)" species started in the forties when herbarium taxonomists were confronted with students of... 

This definition is known as the biological or genetical species concept, because of its emphasis on reproductive isolation,... 

The three schools mentioned in the previous introduction do not differ too much with respect to the species Concept. There are differences, but splitters and lumpers occur in all schools. 

P.C. SILVESTER-BRADLEY (ed.) 1956. The species concept in palaeontology. The systematic Association. London. 

We therefore advocate use of a phylogenetic species concept, but without the constraint of monophyly, to provide an inclusive framework for identifying species of sexual and asexual endophytes. The great advantage of this concept is that it requires an evolutionary basis, and thereby requires an elucidation of the very interesting and varied patterns of speciation among these symbionts. 

Cracraft J. Species concepts in systematics and conservation biology—an ornithological viewpoint. In Claridge MF, Dawah HA, Wilson MR, eds. Species The Units of Biodiversity. London Chapman Hall, 1997, pp 325-339. 

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