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Life-cycle associations involving pairs of holococcolithophorid species: intraspecific variation or cryptic speciation?

Published online by Cambridge University Press:  18 December 2002

MARKUS GEISEN
Affiliation:
Palaeontology Department, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
CHANTAL BILLARD
Affiliation:
Laboratoire de Biologie et Biotechnologies Marines, Université de Caen, Esplanade de la Paix, 14032 Caen, France
ALEXANDRA T.C. BROERSE
Affiliation:
Faculty of Earth Sciences, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
LLUISA CROS
Affiliation:
Institut de Ciències del Mar (CSIC), Passeig Joan de Borbó s/n, 08039 Barcelona, Spain
IAN PROBERT
Affiliation:
Laboratoire de Biologie et Biotechnologies Marines, Université de Caen, Esplanade de la Paix, 14032 Caen, France
JEREMY R. YOUNG
Affiliation:
Palaeontology Department, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
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Abstract

New holococcolith–heterococcolith life-cycle associations are documented based on observations of combination coccospheres. Daktylethra pirus is shown to be a life-cycle phase of Syracosphaera pulchra and Syracolithus quadriperforatus a life-cycle phase of Calcidiscus leptoporus. In addition, new observations from cultures confirm the life-cycle associations of Crystallolithus braarudii with Coccolithus pelagicus and of Zygosphaera hellenica with Coronosphaera mediterranea. In all four cases previous work has shown that the heterococcolithophorid species is associated with another holococcolithophorid. Two other examples of a heterococcolithophorid being associated with two holococcolithophorids have previously been identified, so this seems to be a common phenomenon. The six examples are reviewed to determine whether a single underlying mechanism is likely to be responsible for all cases. It is concluded that there is no single mechanism but rather that the six examples fall into three categories: (a) in two cases the holococcolith types are probably simply ecophenotypic morphotypes; (b) in two other cases the holococcolith types are discrete and are paralleled by morphometric differences in the heterococcolith types; (c) in the final two cases the holococcolith types are discrete but are not paralleled by any obvious morphological variation in the heterococcolith morphology. We infer that cryptic speciation may be widespread in heterococcolithophorid phases and that study of holococcolithophorid phases can provide key data to elucidate this phenomenon.

Type
Research Article
Copyright
© 2002 British Phycological Society

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