scholarly journals Discrete or indiscrete? Redefining the colour polymorphism of the land snail Cepaea nemoralis

2018 ◽  
Author(s):  
Angus Davison ◽  
Hannah J. Jackson ◽  
Ellis W. Murphy ◽  
Tom Reader
Keyword(s):  
Clustering Analysis ◽  
Large Scale ◽  
Major Axis ◽  
Land Snail ◽  
Colour Polymorphism ◽  
Ground Colour ◽  
Banding Patterns ◽  
Cepaea Nemoralis ◽  
Evolutionary Origins ◽  
Colour Classes

Biologists have long tried to describe and name the different phenotypes that make up the exuberant colour polymorphism of the land snail Cepaea nemoralis. Traditionally, the view is that the ground colour is one of a few major colour classes, either yellow, pink or brown, but in practise it is frequently difficult to distinguish the colours, and consistently define different shades of the same colour. To understand whether colour variation is continuous, and to investigate how the variation may be perceived by an avian predator, we applied psychophysical models of colour vision to shell reflectance measures. The main finding is that both achromatic and chromatic variation are indiscrete, being continuously distributed over many perceptual units, with the major axis of chromatic variation representing differences in saturation, or purity of colour. Nonetheless, clustering analysis based on the density of the distribution revealed three groups, roughly corresponding to human-perceived yellow, pink and brown shells. There is also large-scale geographic variation between these morphs across Europe, and some covariance between shell colour and banding patterns. Although further studies are necessary to understand the evolutionary origins and impact of natural selective upon this variation, the observation of continuous variation in colour is intriguing, given that the underlying supergene that determines colour should prevent phenotypes from “dissolving” into continuous trait distributions.

scholarly journals Discrete or indiscrete? Redefining the colour polymorphism of the land snail Cepaea nemoralis

Heredity ◽  
2019 ◽  
Vol 123 (2) ◽  
pp. 162-175 ◽  
Author(s):  
Angus Davison ◽  
Hannah J. Jackson ◽  
Ellis W. Murphy ◽  
Tom Reader
Keyword(s):  
Land Snail ◽  
Colour Polymorphism ◽  
Cepaea Nemoralis

scholarly journals Candidate genes for shell colour polymorphism in Cepaea nemoralis

2017 ◽  
Author(s):  
Jesse Kerkvliet ◽  
Tjalf de Boer ◽  
Menno Schilthuizen ◽  
Ken Kraaijeveld
Keyword(s):  
Candidate Genes ◽  
Differential Expression Analysis ◽  
The Body ◽  
Colour Polymorphism ◽  
Sequence Variant ◽  
Nacreous Layer ◽  
Ground Colour ◽  
Cepaea Nemoralis ◽  
Excellent Starting Point ◽  
Starting Point

The characteristic ground colour and banding patterns on shells of the land snail Cepaea nemoralis form a classic study system for genetics and adaptation. We use RNAseq analysis to identify candidate genes underlying this polymorphism. We sequenced cDNA from the body and the mantle (the shell-producing tissue) of four individuals of two phenotypes and produced a de novo transcriptome of 147,397 contigs. Differential expression analysis identified a set of 1,961 transcripts that were upregulated in mantle tissue. Sequence variant analysis resulted in a set of 2,592 transcripts with single nucleotide polymorphisms (SNPs) that differed consistently between the phenotypes. Combining these results yielded a set of 197 candidate transcripts, of which 38 were annotated. Four of these transcripts are involved in production of the shell’s nacreous layer. Comparison with morph-associated RAD-tags from a published study yielded seven transcripts that were annotated as metallothionein, a protein that is thought to inhibit the production of melanin in melanocytes. These results thus provide an excellent starting point for the elucidation of the genetic regulation of the Cepaea nemoralis shell colour polymorphism.

scholarly journals Introduced land snail Cepaea nemoralis (Gastropoda: Helicidae) in Eastern Europe: spreading history and the shell colouration variability

2021 ◽  
Vol 20 ◽  
pp. 75-91
Author(s):  
Nina Gural-Sverlova ◽  
Roman Egorov ◽  
Oksana Kruglova ◽  
Natalia Kovalevich ◽  
Roman Gural
Keyword(s):  
Eastern Europe ◽  
Global Climate ◽  
Land Snail ◽  
European Countries ◽  
Eastern European ◽  
Ground Colour ◽  
Cepaea Nemoralis ◽  
European Part Of Russia ◽  
Natural Range ◽  
Eastern European Countries

The available data on the present distribution of Cepaea nemoralis in Ukraine, Belarus and the European part of Russia, the history and possible ways of penetration of this species into various parts of Eastern Europe, as well as the colour and banding polymorphism of its shells are analyzed. It has been suggested that the process of rapid spreading of C. nemoralis in the three compared Eastern European countries began at approximately the same time (late 20th – early 21st centuries) and that it may be caused by active and practically uncontrolled importation of seedlings from other European countries, as well as by global climate change, which can contribute to better survival of snails outside their natural range. Despite the possible initial limitation of the phenotypic and genetic diversity associated with the accidental transfer of a limited number of individuals, in the Eastern European colonies, in general, a fairly large variety of the inherited traits of the shell colouration remains. This concerns, first of all, the polymorphism in the shell ground colour (yellow, pink, less often brown) and the main variants of the shell banding (unbanded, mid-banded, five-banded, less often three-banded).

scholarly journals Qualitative and quantitative methods show stability in patterns of Cepaea nemoralis shell polymorphism in the Pyrenees over five decades

2020 ◽  
Author(s):  
Angus Davison ◽  
Daniel Ramos Gonzalez
Keyword(s):  
Quantitative Methods ◽  
Land Snail ◽  
Ground Colour ◽  
Field Surveys ◽  
Cepaea Nemoralis ◽  
Qualitative And Quantitative Methods ◽  
Historical Collections ◽  
Potential Error ◽  
The 1960S ◽  
The Impact

One of the emerging strengths of working with the land snail genus Cepaea is that historical collections can be compared against modern day samples, for instance to understand the impact of changing climate and habitat upon shell morph frequencies. However, one potential limitation is that prior studies scored shell ground colour by eye, usually in the field, into three discrete colours yellow, pink or brown. This incurs both potential error and bias in comparative surveys. In this study, we therefore aimed to use a quantitative method to score shell colour, and evaluated it by comparing patterns of C. nemoralis shell colour polymorphism, using both methods on present day samples, and against historical data gathered in the 1960s using the traditional method. The Central Pyrenees were used as an exemplar, because previous intensive surveys sometimes showed sharp discontinuities of morph frequencies within and between valleys. Moreover, selective factors, such as climate or the human impact in the Pyrenees, have significantly changed since 1960s. The main finding was that while quantitative measures of shell colour reduced the possibility of error, and standardised the procedure, the same altitudinal trends were recovered, irrespective of the method. There was remarkable stability in the local shell patterns over five decades, with the exception of one valley that has been subject to increased human activity. Therefore, although subject to potential error, human-scoring of snail colour data remains valuable, especially if persons have appropriate training. In comparison, while there are benefits in taking quantitative measures of colour in the laboratory, there are also several practical disadvantages, mainly in terms of throughput and accessibility. In the future, we anticipate that both methods may be combined, for example, using automated measures of colour taken from photos generated by citizen scientists conducting field surveys.

scholarly journals Candidate genes for shell colour polymorphism in Cepaea nemoralis

2017 ◽  
Author(s):  
Jesse Kerkvliet ◽  
Tjalf de Boer ◽  
Menno Schilthuizen ◽  
Ken Kraaijeveld
Keyword(s):  
Candidate Genes ◽  
Differential Expression Analysis ◽  
The Body ◽  
Colour Polymorphism ◽  
Sequence Variant ◽  
Nacreous Layer ◽  
Ground Colour ◽  
Cepaea Nemoralis ◽  
Excellent Starting Point ◽  
Starting Point

The characteristic ground colour and banding patterns on shells of the land snail Cepaea nemoralis form a classic study system for genetics and adaptation. We use RNAseq analysis to identify candidate genes underlying this polymorphism. We sequenced cDNA from the body and the mantle (the shell-producing tissue) of four individuals of two phenotypes and produced a de novo transcriptome of 147,397 contigs. Differential expression analysis identified a set of 1,961 transcripts that were upregulated in mantle tissue. Sequence variant analysis resulted in a set of 2,592 transcripts with single nucleotide polymorphisms (SNPs) that differed consistently between the phenotypes. Combining these results yielded a set of 197 candidate transcripts, of which 38 were annotated. Four of these transcripts are involved in production of the shell’s nacreous layer. Comparison with morph-associated RAD-tags from a published study yielded seven transcripts that were annotated as metallothionein, a protein that is thought to inhibit the production of melanin in melanocytes. These results thus provide an excellent starting point for the elucidation of the genetic regulation of the Cepaea nemoralis shell colour polymorphism.

scholarly journals Candidate genes for shell colour polymorphism in Cepaea nemoralis

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3715 ◽  
Author(s):  
Jesse Kerkvliet ◽  
Tjalf de Boer ◽  
Menno Schilthuizen ◽  
Ken Kraaijeveld
Keyword(s):  
Differential Expression ◽  
Candidate Genes ◽  
Expression Analysis ◽  
Differential Expression Analysis ◽  
Colour Polymorphism ◽  
Snp Analysis ◽  
Nacreous Layer ◽  
Ground Colour ◽  
Cepaea Nemoralis ◽  
Excellent Starting Point

The characteristic ground colour and banding patterns on shells of the land snail Cepaea nemoralis form a classic study system for genetics and adaptation as it varies widely between individuals. We use RNAseq analysis to identify candidate genes underlying this polymorphism. We sequenced cDNA from the foot and the mantle (the shell-producing tissue) of four individuals of two phenotypes and produced a de novo transcriptome of 147,397 contigs. Differential expression analysis identified a set of 1,961 transcripts that were upregulated in mantle tissue. Sequence variant analysis resulted in a set of 2,592 transcripts with single nucleotide polymorphisms (SNPs) that differed consistently between the phenotypes. Inspection of the overlap between the differential expression analysis and SNP analysis yielded a set of 197 candidate transcripts, of which 38 were annotated. Four of these transcripts are thought to be involved in production of the shell’s nacreous layer. Comparison with morph-associated Restriction-site Associated DNA (RAD)-tags from a published study yielded eight transcripts that were annotated as metallothionein, a protein that is thought to inhibit the production of melanin in melanocytes. These results thus provide an excellent starting point for the elucidation of the genetic regulation of the Cepaea nemoralis shell colour polymorphism.

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