Chapter 18
The Biology of Thalassia: Paradigms and Recent
Advances in Research
Brigitta I. van Tussenbroek
∗
Unidad Acad ´
emica Puerto Morelos, Instituto de Ciencias del Mar y Limnolog´ ıa, Universidad
Nacional Aut ´
onoma de M ´
exico, Apdo. Postal 1152, Canc ´
un, Quintana Roo, Mexico
Jan A. Vonk and Johan Stapel
Department of Environmental Studies, Faculty of Science, Mathematics and Computing
Science, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands;
email: j.a.vonk@sci.kun.nl (J. A. Vonk) and johan.stapel@bureau.knaw.nl (J. Stapel)
Paul L. A. Erftemeijer
Marine and Coastal Management, WL/Delft Hydraulics, P.O. Box 177, 2600 MH Delft,
The Netherlands; email: paul.erftemeijer@wldelft.nl
Jack J. Middelburg
Netherlands Institute of Ecology (NIOO-KNAW), Korringaweg 7, 4401 NT Yerseke,
The Netherlands; email: j.middelburg@nioo.knaw.nl
Jay C. Zieman
Department of Environmental Sciences, University of Virginia, 291 McCormick Rd.,
P.O. Box 400123, Charlottesville, VA 22904-4123, USA; email: jcz@virginia.edu
I. Introduction
A. The Genus Thalassia
The two species belonging to the genus Thalassia (Family: Hydrocharitaceae), T. testudinum Banks
ex K¨ onig and T. hemprichii (Ehrenberg) Ascherson
are widely distributed in shallow coastal areas in
the tropics and subtropics of the Western Atlantic
and Indo-Pacific, respectively (den Hartog, 1970;
Phillips and Me˜ nez, 1988; Spalding et al., 2003), and
they are considered to be ‘twin species’. The current
hypothesis, based on paleographical data, is that they
∗ Author for correspondence, email: vantuss@icmyl.unam.mx
derived from a common ancestor in the Tethys Sea,
until continental drift separated the modern West
Pacific and West Atlantic (before the Miocene, >24
million years ago). Lumbert et al. (1984) reported
a fossil leaf of Thalassia in the Avon Park Formation, Florida from the late Middle Eocene, which was
identical to leaves of present-day Thalassia. Both
species are very similar morphologically, and on a
macro-scale, they can only be separated on the basis
of counts and dimensions of the styles and stamens of
the flowers (see section VI.B). However, genetically,
the two species show divergence, as was shown by
McMillan (1980) using allozymes, and very recently
by Waycott and Les (2000) using chloroplast ribosomal (trnL) DNA loci and nuclear ITS sequences.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp. 409–439.
c
2006 Springer. Printed in the Netherlands.
The Biology of Thalassia: Paradigms and Recent
Advances in Research
Brigitta I. van Tussenbroek
∗
Unidad Acad ´
emica Puerto Morelos, Instituto de Ciencias del Mar y Limnolog´ ıa, Universidad
Nacional Aut ´
onoma de M ´
exico, Apdo. Postal 1152, Canc ´
un, Quintana Roo, Mexico
Jan A. Vonk and Johan Stapel
Department of Environmental Studies, Faculty of Science, Mathematics and Computing
Science, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands;
email: j.a.vonk@sci.kun.nl (J. A. Vonk) and johan.stapel@bureau.knaw.nl (J. Stapel)
Paul L. A. Erftemeijer
Marine and Coastal Management, WL/Delft Hydraulics, P.O. Box 177, 2600 MH Delft,
The Netherlands; email: paul.erftemeijer@wldelft.nl
Jack J. Middelburg
Netherlands Institute of Ecology (NIOO-KNAW), Korringaweg 7, 4401 NT Yerseke,
The Netherlands; email: j.middelburg@nioo.knaw.nl
Jay C. Zieman
Department of Environmental Sciences, University of Virginia, 291 McCormick Rd.,
P.O. Box 400123, Charlottesville, VA 22904-4123, USA; email: jcz@virginia.edu
I. Introduction
A. The Genus Thalassia
The two species belonging to the genus Thalassia (Family: Hydrocharitaceae), T. testudinum Banks
ex K¨ onig and T. hemprichii (Ehrenberg) Ascherson
are widely distributed in shallow coastal areas in
the tropics and subtropics of the Western Atlantic
and Indo-Pacific, respectively (den Hartog, 1970;
Phillips and Me˜ nez, 1988; Spalding et al., 2003), and
they are considered to be ‘twin species’. The current
hypothesis, based on paleographical data, is that they
∗ Author for correspondence, email: vantuss@icmyl.unam.mx
derived from a common ancestor in the Tethys Sea,
until continental drift separated the modern West
Pacific and West Atlantic (before the Miocene, >24
million years ago). Lumbert et al. (1984) reported
a fossil leaf of Thalassia in the Avon Park Formation, Florida from the late Middle Eocene, which was
identical to leaves of present-day Thalassia. Both
species are very similar morphologically, and on a
macro-scale, they can only be separated on the basis
of counts and dimensions of the styles and stamens of
the flowers (see section VI.B). However, genetically,
the two species show divergence, as was shown by
McMillan (1980) using allozymes, and very recently
by Waycott and Les (2000) using chloroplast ribosomal (trnL) DNA loci and nuclear ITS sequences.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp. 409–439.
c
2006 Springer. Printed in the Netherlands.