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Population bottleneck triggering millennial-scale morphospace shifts in endemic thermal-spring melanopsids.

Neubauer TA, Harzhauser M, Georgopoulou E, Wrozyna C - Palaeogeogr Palaeoclimatol Palaeoecol (2014)

Bottom Line: The formation of a small, highly eutrophic swamp with increased input of organic matter marginalized the melanopsids and reduced population size.The presented data make natural selection as the dominating force unlikely but rather indicates genetic drift following a bottleneck effect induced by the environmental changes.This claim contrasts the "obvious trend" and shows that great morphological variability has to be carefully and objectively evaluated in order to allow sound interpretations of the underlying mechanisms.

View Article: PubMed Central - PubMed

Affiliation: Geological-Paleontological Department, Natural History Museum Vienna, Burgring 7, 1010 Vienna, Austria.

ABSTRACT

For more than hundred years the thermal spring-fed Lake Pețea near Oradea, Romania, was studied for its highly endemic subfossil and recent fauna and flora. One point of focus was the species lineage of the melanopsid gastropod Microcolpia parreyssii, which exhibited a tremendous diversity of shapes during the earlier Holocene. As a consequence many new species, subspecies, and variety-names have been introduced over time, trying to categorize this overwhelming variability. In contrast to the varied subfossil assemblage, only a single phenotype is present today. We critically review the apparent "speciation event" implied by the taxonomy, based on the presently available information and new data from morphometric analyses of shell outlines and oxygen and carbon isotope data. This synthesis shows that one turning point in morphological evolution coincides with high accumulation of peaty deposits during a short time interval of maximally a few thousand years. The formation of a small, highly eutrophic swamp with increased input of organic matter marginalized the melanopsids and reduced population size. The presented data make natural selection as the dominating force unlikely but rather indicates genetic drift following a bottleneck effect induced by the environmental changes. This claim contrasts the "obvious trend" and shows that great morphological variability has to be carefully and objectively evaluated in order to allow sound interpretations of the underlying mechanisms.

No MeSH data available.


Related in: MedlinePlus

Geographic overview of the studied locality and section. The morphological succession and the phenotype names were adopted from Kormos (1905b). For a revised taxonomic concept see Chapter 5.6. and the Appendix. The dating as well as the paleoecological interpretation to the right of the section is correlated following the data of Sümegi et al. (2012b).
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f0005: Geographic overview of the studied locality and section. The morphological succession and the phenotype names were adopted from Kormos (1905b). For a revised taxonomic concept see Chapter 5.6. and the Appendix. The dating as well as the paleoecological interpretation to the right of the section is correlated following the data of Sümegi et al. (2012b).

Mentions: Microcolpia parreyssii (Philippi, 1847) is a thermophilic melanopsid species presently restricted to a single locality, the small thermal spring-fed Lake Pețea (Rom. Băile 1 Mai, Băile Episcopale; Hung. Püspökfürdő; Germ. Bischofsbad; Fig. 1), situated about 9 km SE of Oradea in W Romania. It is a morphologically well-defined taxon comprising distinctly stepped and ribbed shells. The morphological history of this species, however, draws a completely different picture. Shells from late Pleistocene to Holocene deposits of the thermal spring exhibit an extreme variability and a distinctly wider range of morphologies as present in the lake today. This range includes smooth, slender, and elongate shapes, stepped and non-ribbed forms, slender and keeled phenotypes, as well as subfossil representatives of typical M. parreyssii (Brusina, 1903; Kormos, 1903, 1904, 1905a,b; Paucă, 1937; Sümegi et al., 2012a,b; Fig. 2). This led to the introduction of a large number of names, trying to categorize this vast variability (Brusina, 1903; Kormos, 1905b). In total, 43 species-, subspecies-, variation- and forma-names have been introduced since then. Still, the taxonomic concepts applied by Brusina (1903) and Kormos (1905b) are unfortunately not clear from their descriptions — and illustrations are available only for a few phenotypes. Moreover, the taxon delimitations of both authors diverge considerably. Brusina (1903) himself recognized the strong over-splitting and suggested alternatively a series of synonymizations. The fluent morphological transitions, however, make splittings as well as synonymizations highly subjective anyway.


Population bottleneck triggering millennial-scale morphospace shifts in endemic thermal-spring melanopsids.

Neubauer TA, Harzhauser M, Georgopoulou E, Wrozyna C - Palaeogeogr Palaeoclimatol Palaeoecol (2014)

Geographic overview of the studied locality and section. The morphological succession and the phenotype names were adopted from Kormos (1905b). For a revised taxonomic concept see Chapter 5.6. and the Appendix. The dating as well as the paleoecological interpretation to the right of the section is correlated following the data of Sümegi et al. (2012b).
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4375792&req=5

f0005: Geographic overview of the studied locality and section. The morphological succession and the phenotype names were adopted from Kormos (1905b). For a revised taxonomic concept see Chapter 5.6. and the Appendix. The dating as well as the paleoecological interpretation to the right of the section is correlated following the data of Sümegi et al. (2012b).
Mentions: Microcolpia parreyssii (Philippi, 1847) is a thermophilic melanopsid species presently restricted to a single locality, the small thermal spring-fed Lake Pețea (Rom. Băile 1 Mai, Băile Episcopale; Hung. Püspökfürdő; Germ. Bischofsbad; Fig. 1), situated about 9 km SE of Oradea in W Romania. It is a morphologically well-defined taxon comprising distinctly stepped and ribbed shells. The morphological history of this species, however, draws a completely different picture. Shells from late Pleistocene to Holocene deposits of the thermal spring exhibit an extreme variability and a distinctly wider range of morphologies as present in the lake today. This range includes smooth, slender, and elongate shapes, stepped and non-ribbed forms, slender and keeled phenotypes, as well as subfossil representatives of typical M. parreyssii (Brusina, 1903; Kormos, 1903, 1904, 1905a,b; Paucă, 1937; Sümegi et al., 2012a,b; Fig. 2). This led to the introduction of a large number of names, trying to categorize this vast variability (Brusina, 1903; Kormos, 1905b). In total, 43 species-, subspecies-, variation- and forma-names have been introduced since then. Still, the taxonomic concepts applied by Brusina (1903) and Kormos (1905b) are unfortunately not clear from their descriptions — and illustrations are available only for a few phenotypes. Moreover, the taxon delimitations of both authors diverge considerably. Brusina (1903) himself recognized the strong over-splitting and suggested alternatively a series of synonymizations. The fluent morphological transitions, however, make splittings as well as synonymizations highly subjective anyway.

Bottom Line: The formation of a small, highly eutrophic swamp with increased input of organic matter marginalized the melanopsids and reduced population size.The presented data make natural selection as the dominating force unlikely but rather indicates genetic drift following a bottleneck effect induced by the environmental changes.This claim contrasts the "obvious trend" and shows that great morphological variability has to be carefully and objectively evaluated in order to allow sound interpretations of the underlying mechanisms.

View Article: PubMed Central - PubMed

Affiliation: Geological-Paleontological Department, Natural History Museum Vienna, Burgring 7, 1010 Vienna, Austria.

ABSTRACT

For more than hundred years the thermal spring-fed Lake Pețea near Oradea, Romania, was studied for its highly endemic subfossil and recent fauna and flora. One point of focus was the species lineage of the melanopsid gastropod Microcolpia parreyssii, which exhibited a tremendous diversity of shapes during the earlier Holocene. As a consequence many new species, subspecies, and variety-names have been introduced over time, trying to categorize this overwhelming variability. In contrast to the varied subfossil assemblage, only a single phenotype is present today. We critically review the apparent "speciation event" implied by the taxonomy, based on the presently available information and new data from morphometric analyses of shell outlines and oxygen and carbon isotope data. This synthesis shows that one turning point in morphological evolution coincides with high accumulation of peaty deposits during a short time interval of maximally a few thousand years. The formation of a small, highly eutrophic swamp with increased input of organic matter marginalized the melanopsids and reduced population size. The presented data make natural selection as the dominating force unlikely but rather indicates genetic drift following a bottleneck effect induced by the environmental changes. This claim contrasts the "obvious trend" and shows that great morphological variability has to be carefully and objectively evaluated in order to allow sound interpretations of the underlying mechanisms.

No MeSH data available.


Related in: MedlinePlus