Molluscan and plant biostratigraphy of some Late Devensian and Flandrian deposits in Kent

Kerney, M.P.; Preece, Richard C.; Turner, Charles

doi:10.1098/rstb.1980.0126

Cited by 92 publications

(54 citation statements)

References 21 publications

(15 reference statements)

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“…They were absent during the Late-Glacial, from 13 0001 0 000 yr BP, but were certainly present by 9000 yr BP, while Arianta had established itself by about 11500 yr BP (Kerney et al 1980). They were abundant at the time of the climatic optimum (Currey & Cain 1968;Cain 1971) about 6000 yr BP.…”

Section: (D) Time-scalementioning

confidence: 89%

A two–stage model for Cepaea polymorphism

Cook

1998

Phil. Trans. R. Soc. Lond. B

123

134

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The history of the study of snails in the genus Cepaea is brie£y outlined. Cepaea nemoralis and C. hortensis are polymorphic for genetically controlled shell colour and banding, which has been the main interest of the work covered. Random drift, selective predation and climatic selection, both at a macro-and microscale, all a¡ect gene frequency. The usual approach to understanding maintenance of the polymorphism, has been to look for centripetal e¡ects on frequency. Possible processes include balance of mutation pressure and drift, heterozygote advantage, relational balance heterosis, frequency-dependent predation, multi-niche selective balance, or some combination of these.Mutational balance is overlaid by more substantial forces. There is some evidence for heterosis. Predation by birds may protect the polymorphism, and act apostatically to favour distinct morphs. Although not substantiated for Cepaea, many studies show that predators behave in the appropriate manner, while shell colour polymorphisms in molluscs occur most commonly in species exposed to visually searching predators. It is not known whether di¡erent thermal properties of the shells help to generate equilibria.Migration between colonies is probably greater than originally thought. The present geographical range has been occupied for less than 5000 generations. Climatic and human modi¢cation alter snail habitats relatively rapidly, which in turn changes selection pressures. A simple simulation shows that migration coupled with selection which £uctuates but is not centripetal, may retain polymorphism for su¤ciently long to account for the patterns we see today. There may therefore be a two-stage basis to the polymorphism, comprising long-term but weak balancing forces coupled with £uctuating selection which does not necessarily balance but results in very slow elimination. Persistence of genetic variants in this way may provide the conditions for evolution of a balanced genome.

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Section: (D) Time-scalementioning

confidence: 89%

A two–stage model for Cepaea polymorphism

Cook

1998

Phil. Trans. R. Soc. Lond. B

123

134

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“…C. nemoralis arrived in Britain in the late Holocene, ca. 10 000 years before the present (Kerney et al 1980) so that there is a limited time in which the area e¡ects could have arisen. Endler (1977) made some computer simulations of migration and drift in a two-dimensional`stepping stone' model, and observed that they produced area e¡ects in fewer than 1000 generations (for C. nemoralis roughly 3000 years), although they were neither as extensive nor as di¡erent from each other as those on the Marlborough Downs.…”

Section: Discussionmentioning

confidence: 99%

History or current selection? A molecular analysis of ‘area effects’ in the land snailCepaea nemoralis

Davison

Clarke

2000

Proc. R. Soc. Lond. B

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We have used molecular variation in microsatellite and mitochondrial DNA to throw light on the origins of enigmatic geographical patterns, known as`area e¡ects', in the shell polymorphisms of the land snail Cepaea nemoralis. Our aim was to assess the relative importance of recent selection and historical events in the formation of these patterns. On the Marlborough Downs in Wiltshire, England, the`type locality' for area e¡ects, the frequencies of microsatellites are signi¢cantly associated with the frequencies of alleles for shell banding. A less clear association is found between microsatellites and shell colour. Mitochondrial haplotypes show no signi¢cant relationships. Although the correlated geographical patterns could be the results of random genetic drift from an initially uniform array of populations, the magnitudes of the patterns, and of the correlations between them, seem too strong to have arisen by drift since the last glaciation. Our results suggest that invasions from refugia have been the most important factors in forming area e¡ects.

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“…However, in this latter profile, the Pontian Pomatias rivulare is substituted by its Atlanto-Mediterranean vicariant counterpart: Pomatias elegans. The radiocarbon-dated appearance of these latter taxa in the Ócsa profile is the oldest recorded one in Europe several thousand years before the first Atlantic distribution records of the taxon [98,99]. On the basis of this record, the assumption that the Atlantic and Central European distribution of this taxon is connected to the Middle Holocene [100] must be refuted.…”

Section: Ice Age Refugia At the Interface Of Windblown Sand Dunes Andmentioning

confidence: 99%

Ice Age Terrestrial and Freshwater Gastropod Refugia in the Carpathian Basin, Central Europe

Sümegi¹,

Gulyás²,

Molnár³

et al. 2018

Biological Resources of Water

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Thanks to its unique microclimatic, geomorphological , hydrological conditions forming a mosaic-like environment present at all scales, numerous Late Tertiary and Pleistocene warmth-loving gastropod taxa managed to find refugee within the Carpathian Basin during the major-minor cold spells of the Ice Age. This complex system of refugia have been continuously functioning and evolving since the Late Tertiary through the entire Pleistocene and the Holocene. To understand the spatial and temporal evolution of refugia, detailed paleoecological investigations have been implemented, results of which are summed here. The high-grade fractal-like complexity of the environment led to the emergence of a so-called dual refugia, which is a unique feature of the Carpathian Basin. This temporally parallel but spatially differing presence of habitats for taxa of contrasting ecological needs was noted for paleotemperature gradients and temperate woodland and steppe habitat types as well. Furthermore, detailed geological and paleoecological analysis of a small Pleistocene hot-spring fed pond revealed information about the evolution of endemic thermophylous freshwater gastropod taxa within this microrefugia. This chapter is aimed to give an overview of the nature, evolution of temperate terrestrial and freshwater gastropod refugia present in the Carpathian Basin during the Ice Age.

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Molluscan and plant biostratigraphy of some Late Devensian and Flandrian deposits in Kent

Cited by 92 publications

References 21 publications

A two–stage model for Cepaea polymorphism

A two–stage model for Cepaea polymorphism

History or current selection? A molecular analysis of ‘area effects’ in the land snailCepaea nemoralis

Ice Age Terrestrial and Freshwater Gastropod Refugia in the Carpathian Basin, Central Europe

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