New contributions to allochthonous Ludwigia species (Onagraceae) on Catalonia

Abstract

Noves contribucions a les espècies aŀlòctones de Ludwigia (Onagraceae) a Catalunya

Butlletí de la Institució Catalana d’Història Natural

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New contributions to allochthonous Ludwigia species (Onagraceae) on Catalonia
Noves contribucions a les espècies aŀlòctones de Ludwigia (Onagraceae) a Catalunya
Jordi Bou Manobens*, Luis Portillo ** & Antoni Curcó i Masip***
* LAGP-Flora i Vegetació. Institut de Medi Ambient. Universitat de Girona. Campus Montilivi. 17003 Girona.
** UMR985 Écologie et Santé des Écosystèmes. Agrocampus Ouest. INRA. 35042 Rennes France Cedex.
*** Parc Natural del Delta de l’Ebre. Generalitat de Catalunya. Av. Generalitat, 46. 43870 Deltebre.
Autor per a la correspondència: Jordi Bou: A/e: jordi.bou.manobens@gmail.com
Rebut: 28.02.2019. Acceptat: 18.03.2019. Publicat: 31.03.2019
Butlletí de la Institució Catalana d’Història Natural, 83: 45-48. 2019 ISSN 2013-3987 (online edition): ISSN: 1133-6889 (print edition)
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DOI: 10.2436/20.1502.01.4
Ludwigia grandiora (Michaux) Greuter & Burdet subsp.
hexapetala (Hook. & Arn.) Nesom & Kartesz
Mo n t s i à : Amposta, al riu Ebre, CF0109, 0 m, 22-VII-
2018, J. Bou (HGI 23947).
Allochthonous species from the genus Ludwigia on the
Iberian Peninsula have often generated taxonomic confusion,
since although the various plant catalogues mention only
Ludwigia grandiora in this region (Nieto Feliner, 2000;
Bolòs et al., 1993), Verloove & Sánchez (2008) reported L.
peploides from the Llobregat River. In addition, in 2016, one
of us (J.B.) published a study on the allochthonous taxa of
Ludwigia in Catalonia, in which it was concluded that all the
samples analysed corresponded to L. peploides subsp. mon-
tevidensis (Bou Manobens & Font Garcia, 2016), a hydro-
phyte from the Americas that has invaded both rivers and still
waters throughout a large part of Europe (CABI, 2019).
In order to increase our knowledge of the dynamics and
situation of L. peploides in Catalonia, in 2018 a campaign
was launched to collect samples from the populations of sev-
eral Catalan basins. In the Ebre River, there was a popula-
tion (Fig. 1a), not recognised in our previous study, found
in the main course of the river, in an area bordering the Ebre
Delta Natural Park. An analysis of the morphology of vari-
ous specimens determined that it was Ludwigia grandiora
subsp. hexapetala (HGI 23947). This taxon naturalised in the
Lez River in Montpellier (France) in 1826 (Dandelot, 2004),
from where it has expanded its range substantially, becoming
one of the invasive aquatic plants with the greatest impact
(Ruaux et al., 2009), with similar biology and dynamics to
L. peploides subsp. montevidensis. The presence of L. gran-
diora subsp. hexapetala in Catalonia, and specically in
the area of the Ebre Delta, which is geographically more re-
mote from the populations found in France than other basins,
raises several doubts about its introduction in Catalonia, the
transport vector, and the population it originated from, as it
could have come from either European populations or have
originated from a native American population.
Figure 1. Herbaceous Ludwigia spp. plants in summer 2018: a) L. grandiora subsp. hexapetala, in the Ebre River, at Amposta; and b) L. peploides
subsp. montevidensis, in the Ter River, near Colomers.
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Ludwigia peploides (Kunth) P.H. Raven subsp. monteviden-
sis (Spreng.) P.H. Raven
Ba i x EM p o r d à : Torroella de Montgrí, al Ter, entre la resclosa
i el pont, EG0954, 4 m, 15-VII-2016, J. Bou (HGI 23251).
al t EM p o r d à : Palau-Saverdera, a la Bassa del Camí Ral,
EG1181, 7 m, 23-VII-2018, J. Bou (HGI 23944); Palau-Sav-
erdera, basses de les Garrigues, EG1181, 10 m, 23-VII-2018,
J. Bou (HGI 23945). Ba i x ll o B r E g a t : El Prat de Llobregat,
riba esquerra del Llobregat, DF2377, 3 m, 22-VII-2018, J.
Bou (HGI 23946). Ba i x EB r E : Deltebre, Secanella, bassa de
la Barraca d’en Salvador, CF0911, 0 m, 22-VII-2018, J. Bou
(HGI 23948).
According to Bou Manobens & Font Garcia (2016) L.
peploides subsp. montevidensis is naturalised and expanding
its range in Catalan rivers, which is very worrying due to the
high risk of invasion of river ecosystems (Rodríguez-Merino
et al., 2017). This taxon is known to have an enormous ca-
pacity for vegetative multiplication through small propagules
(Ruaux et al., 2009), something that has been demonstrated
by how easily it recovered after several attempts to mechani-
cally control its presence in two specic populations. In Alt
Empordà, in an endeavour to recover a pond in poor ecologi-
cal condition, the mechanical eradication of the population
was attempted (ACN, 2016), but new populations have ap-
peared (HGI 23944 and HGI 23945), probably due to prop-
agules or viable seeds that were not removed. The second
case involved a pond in Baix Ebre, linked to a house, where
heavy machinery was used to eliminate the population and
prevent its propagation. However, in this case, even though
part of the soil where it had rooted was removed (personal
observation), this was not sufcient and the population has
regrown (HGI 23948). Its enormous capacity for dispersion is
thus guaranteed both in terms of sexual reproduction and the
creation of propagules (Dandelot, 2004), as observed in the
Ter basin. Although our previous research (Bou Manobens
& Font Garcia, 2016) dealt with more or less fragmented
population centres throughout the basin, in the summer of
2018 it was observed that the populations had increased their
Figure 2. Detailed photograph of the stipules of a) L. grandiora subsp. hexapetala in the Ebre River from Amposta, and b) L. peploides subsp.
montevidensis from Girona. The presence of stipules and trichomes on the stem is a distinguishing character for this subspecies of L. peploides.
Figure 3. Flowers of a) L. grandiora subsp. hexapetala from Amposta, and b) L. peploides subsp. montevidensis from Girona.
J. BOU MANOBENS ET AL.
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continuity (Fig. 1b), from the lower part of the Onyar River,
around Quart, to the mouth of the Ter River, at Torroella de
Montgrí. The rapid expansion of this taxon in Catalonia, par-
ticularly in the Ter basin, and the various impacts evident in
other European countries (Dandelot, 2004; Dandelot et al.,
2005, 2008; Robert et al., 2013), highlight the need to clas-
sify this species as a major threat to Catalonia’s aquatic eco-
systems.
To identify the samples collected in this study, not only
have we studied morphological characters, which have some-
times led to confusion in our area (Bou Manobens & Font
Garcia, 2016), but we have also counted the number of chro-
mosomes to remove any doubt, as the two taxa are different
in this respect (Dandelot, 2004). L. grandiora subsp. hexa-
petala is decaploid, whereas L. peploides subsp. monteviden-
sis is diploid (Zardini et al., 1991a,b). All the studied popula-
tions were analysed using the “Plateforme de Cytogénétique
Moléculaire Végétale” (PCMV; Molecular Cytogenics Plat-
form) at the INRA, in Le Rheu (France). All the plants at-
tributed to L. peploides subsp. montevidensis have 16 chro-
mosomes, while L. grandiora subsp. hexapetala from the
Ebre River has 80 chromosomes. In order to clarify the dif-
ferences, the following identication key is proposed:
1 Elongated stipules (Fig. 2a). Sepals persistent on the fruit,
more than 18 mm long. Flowering stems and pedicels
with patent hairs 1-2 mm long. Leaves of the owering
stems lanceolate to almost obovate-lanceolate, dull, 4-12
cm long. Petals (12)15-23 mm long (Fig. 3a). Small sto-
mata 28±3 µm. Chromosomes 2n=80 (Fig. 4a) ................
......................................L. grandiora subsp. hexapetala
– Reniform stipules (Fig. 2b). Sepals persistent on the fruit,
more than 10 mm long. Flowering stems and pedicels with
patent hairs 0.5-1 mm long. Leaves of the owering stems
obovate-oblong to almost elliptical-oblong, shiny, 3-6 cm
long. Petals 10-18 mm long (Fig. 3b). Stomata 19±2 µm.
Chromosomes 2n=16 (Fig. 4b) .........................................
....................................L. peploides subsp. montevidensis
Over recent years, the dynamics of both species have been
representing a serious threat to the biodiversity of aquatic
ecosystems, demonstrating the need for new studies on these
invasive hydrophytes. In order to efciently manage and con-
trol them, we need to more precisely understand the popula-
tion dynamics and impacts of these invasive species, while
also focusing on their origins and population genetics.
Acknowledgments
We would like to thank Olivier Coriton, Virginie Huteau,
and Dominique Barloy from the INRA and Agrocampus Ou-
est Rennes for their assistance in obtaining karyotype photo-
graphs of the samples.
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NEW CONTRIBUTION TO ALLOCHTHONOUS LUDWIGIA SPECIES (ONAGRACEAE) ON CATALONIA
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