Les articles d'Antoine Gazaix

Vegetation trajectories over 150 years of temporary ponds created in the Camargue delta (Southern France)

Wed, 18 Mar 2026 15:40:14

de Hugo Fontes, Patrick Grillas, Thierry Dutoit, Antoine Gazaix, Elie Gaget, François Mesléard
In Restoration Ecology, (en ligne) (March, 2026), e70372
En ligne : onlinelibrary.wiley.com[...]

Temporary ponds in the Mediterranean climate have a high conservation value, but many have been severely destroyed or degraded. Pond restoration and new pond creation have been engaged widely. Evaluations of the success of such operations are generally carried out over 10–15 years and show divergent results over this timeframe. In the Camargue (Rhône delta, South of France), several temporary ponds were created with various objectives since the second half of the 19th century.
Study the long-term trajectory of plant communities in created temporary ponds and compare them with those of reference temporary ponds.
We carried out vegetation surveys and measured environmental parameters in 25 ponds created in the 19th, 20th, and 21st centuries, as well as in 27 natural reference ponds (space-for-time substitution approach).
Submerged macrophyte communities (composition, abundance, and species-richness) converged toward the reference communities after one or several decades. Emergent plant communities (terrestrial plants and helophytes) converged more slowly toward the reference communities (composition and abundance). Even after 150 years, the emergent plant communities with the highest conservation interest (in particular Natura 2000 habitat) were not found in created ponds.
The creation of temporary ponds in the Camargue is of conservation interest but cannot compensate for the loss of natural temporary ponds.

Global and regional conservation status of vascular wetland plants in Mediterranean islands: a collaborative network to improve knowledge and awareness

Fri, 21 Nov 2025 15:10:24

de Mauro Fois, Carles Burguera, Necmi Aksoy, Gianluigi Bacchetta, Simonetta Bagella, Giulio Barone, Ioannis Bazos, Imtinen Ben Haj Jilani, Leanne Camilleri, Miquel Capó, et al.
In Biological Conservation, 313 (January, 2026), 111595
En ligne : www.sciencedirect.com[...]

Mediterranean wetlands are highly sensitive ecosystems, particularly vulnerable to human pressure and shifts in precipitation and temperature regimes. Wetland plants can be particularly threatened in Mediterranean insular contexts, where such habitats are naturally smaller and more fragmented than in their continental counterparts. This study investigated 275 species of vascular wetland plants that were considered to be at least regionally threatened across 2217 islands and islets in the Mediterranean. We provided both global and local IUCN conservation assessments (summarized in a ‘conservation concern’ index) and ‘assessment completion’ (i.e. knowledge level) for each taxon as well as a geographic distribution among islands, wetland types, and life forms. Most of wetland plants were threatened at the regional level, although assessment completion was generally low, except for endemics. Inland and endemic wetland plants were more threatened than the rest. A phylogenetic signal was detected, highlighting that Orchidaceae and Apiaceae were of particularly high conservation concern, while other families, especially Amaranthaceae, exhibited low levels of assessment completion. No geographical patterns were found in terms of conservation concern and assessment completion. Our findings provide critical insights into biodiversity patterns, identify conservation gaps and priorities and contribute to the development of targeted strategies for the protection of wetland plants, which are crucial indicators of the entire natural capital of Mediterranean island ecosystems.

Occupancy changes over the summer of the rare fen raft spider Dolomedes plantarius in a drained fen strongly depend on vegetation structure

Tue, 16 Dec 2025 11:18:56

de Antoine Gazaix, Charlie Rendell, Adrien Berquer, Nicolas Caron, Aurélien Besnard, Thibaut Couturier
In Insect Conservation and Diversity, (en ligne) (December, 2025), icad.70048
En ligne : resjournals.onlinelibrary.wiley.com[...]

Fens are among the most diverse ecosystems in Europe. They are also highly threatened, mostly by drainage and climate change. Understanding how drought can affect biodiversity in these ecosystems is thus crucial to recommend effective management actions, in particular for species with limited dispersal capacity.
This study investigated the presence of the threatened spider Dolomedes plantarius using a dynamic occupancy approach during spring to summer, a period of high adult activity.
From May to July 2022, we censused adult presence–absence during six visits of 103 transects located in various fen habitats of the Sacy wetlands in northern France.
Species detection probability was low (mean p = 0.21) and maximal at temperatures from 18 to 19°C.
Initial occupancy probability (mean psi = 0.53) was high, positively influenced by water and Cyperaceae cover and negatively by vegetation height.
As the season progressed, the probability of colonization of new transects was low (gamma = 0.09), whereas the probability of extinction in previously occupied transects was high (epsilon = 0.42). This epsilon decreased with maximum litter thickness and sedge tussock cover: these two factors probably protect individuals from heat and drought.
Thus, while hydrological restoration actions of this threatened ecosystem should focus on maintaining high water levels, we also recommend targeting Cyperaceae species, including areas with low vegetation height and maintaining litter and sedge tussocks by extensive grazing or rotational mowing to mitigate drought effects on Dolomedes plantarius.

Ecological niche differentiation among six annual Lythrum species in Mediterranean temporary pools (2021)

Wed, 3 Nov 2021 10:19:06

de Antoine Gazaix, Patrick Grillas, Guillaume Papuga, Hugo Fontes, Florent Sabatier, Virginie Pons, Perrine Gauthier, John D. Thompson
2021, 13
En ligne : link.springer.com[...]

The ecological niche defines the favourable range of a species in a multidimensional space of ecological factors that determine the presence and function of individuals. This fundamental concept in ecology is widely used to understand plant species coexistence and segregation. In this study, we test for ecological differentiation among six annual Lythrum species that are characteristic of temporary pools in the South of France, where they either coexist or occur separately. We first analysed the co-occurrence of species at two different geographical scales: cluster analyses of species presence in 10 km grid cells and coexistence in 0.25 m2 quadrats within populations of each species. Second, for three to nine populations of each species, we quantified a range of biotic and abiotic parameters using point contacts and soil measurements in five 0.25 m2 quadrats per population. We performed PCA on all variables and analysed each variable separately to compare the ecological niche features of the six species. A phenological index was assessed for the plant community of each site. We detected highly localized niche differentiation in terms of soil pH (all species) and for a range of variables among pairs of species. The six species also showed marked differences in the flowering period relative to the mean and variability of flowering time in their local community. These fine-scaled niche differences are associated with phylogenetic distances among species and may contribute to species’ coexistence. These results are integrated in a conservation management plan for the habitat of the rarest species in this group.

A history of discoveries and disappearances of the rare annual plant Lythrum thesioides M.Bieb.: new insights into its ecology and biology

Mon, 20 Apr 2020 19:02:13

de Antoine Gazaix, Mario Klesczewski, Michel-Ange Bouchet, Manuel Cartereau, James Molina, Henri Michaud, Serge D. Muller, Lionel Pirsoul, Perrine Gauthier, Patrick Grillas, et al.
In Botany Letters, 167(2) (April, 2020), 201-211
En ligne : doi.org[...]

Mediterranean temporary pools are threatened ecosystems that host a unique plant community, mostly composed of annual species with large and long-lived seed banks. The longevity of their seed bank, the scarcity of their habitat, the small size of their populations and the low frequency of above-ground vegetation result in a low probability of detection of these species. The discovery of new populations of such rare species are thus important for our understanding of the ecology of the temporary pool ecosystem. Lythrum thesioides M.Bieb., 1808 is a very rare annual species of temporary pools and river banks which was thought to be extinct in the South of France until 1998. Here, we review the distribution of the species and report the recent discovery of a population during a targeted search combining historical data on wetland occurrence on a particular geological substrate. We present new information on its autecology, pollen morphology and the karyotype. Only three populations are currently known worldwide for Lythrum thesioides, and only one of these has favorable management conditions. Thus, we outline new conservation perspectives in the context of a targeted search project and the conservation management of one population.

Lythrum netofa (Lythraceae) a new species from a temporary flooded plain of Israel

Mon, 23 Mar 2020 11:43:08

de Antoine Gazaix, Shmuel Mazar, Shir Vered
In Phytotaxa, 437(1) (March 2020), 47-50
En ligne : www.biotaxa.org[...]

Species of the genus Lythrum Linnaeus (1753: 446) (Lythraceae) occur in temporary pools and wetlands (Morris, 2007) with about 35 species around the world (Graham, 2007). In the Mediterranean area, there are more than 10 species that mostly occur in temporary pools (Castroviejo Bolibar et al., 1997; Tison et al. 2014). Most of the species are also present in East and Central Asia (Webb, 1968). However, some species are limited to Europe, mostly Western Europe, e.g. L. flexuosum Lagasca (1816: 16) and L. baeticum González-Albo (1936: 141) (Castroviejo Bolibar et al., 1997), some are limited to West Asia, e.g. L. silenoides Boissier & Noë (in Boissier 1856: 55) (Ghazanfar, 2016), while Lythrum salicaria Linnaeus (1753: 446), the loosestrife, is widely distributed in Asia, Europe, Africa, Oceania and introduced in North America.

Ecologie des Lythrum annuels des mares temporaires méditerranéennes (2019-12-13)

Tue, 21 Jan 2020 14:53:45

de Antoine Gazaix
2019-12-13, 263
En ligne : hal.archives-ouvertes.fr[...]

Les communautés de plantes des mares temporaires méditerranéennes sont caractérisées par la dominance des espèces annuelles, avec une banque de graines persistante, dont la germination est associée aux alternances d'inondation et d'assèchement. Bien que de petites tailles et irrégulièrement distribuées dans les paysages, elles possèdent une flore riche. Elles ont cependant été particulièrement détruites et dégradés, et de nombreuses espèces inféodées à cet habitat sont aujourd'hui rares et menacées. Parmi elles, six espèces annuelles du genre Lythrum sont présentes dans le sud de la France, dont Lythrum thesioides. Cette espèce supposée éteinte en Europe au milieu du XX° siècle, a été redécouverte successivement à partir de 1998 dans 3 mares temporaires méditerranéennes de France. Les objectifs de cette thèse sont (1) de caractériser les niches écologiques de ces six espèces et (2) d'utiliser cette connaissance pour proposer des actions de gestion pertinentes pour leur conservation, notamment pour L. thesioides. La première étape a été de clarifier la distribution de ces 6 espèces annuelles dans la région méditerranéenne et particulièrement celle de Lythrum thesioides. Ce travail s'est accompagné d'une étude phylogénétique des relations entre les six espèces et 13 autres du genre Lythrum. La comparaison des niches de régénération a ensuite illustré l'importance de plusieurs variables environnementales pour la germination, et principalement la température optimale de germination qui était différente entre les espèces et particulièrement élevée pour L. thesioides. L'étude des micro-niches des plantes adultes a enfin démontré une différentiation franche entre les espèces en termes de propriété du sol, et dans une moindre mesure, de présence et phénologie de la communauté végétale compagne. La combinaison des résultats de ce travail, caractérisant une niche écologique originale pour L. thesioides, a enfin été utilisée pour alimenter des propositions de gestion, composée de plusieurs scénarios pour la conservation de L. thesioides dans sa principale population dans le sud de la France.

Heterogeneous forest structures favor persistence of the grassland Mediterranean geophyte Gagea lacaitae

Fri, 15 Nov 2019 15:48:04

de Hugo Fontes, Antoine Gazaix, Guillaume Papuga
In Botany Letters, 166(4) (October, 2019), 487-498
En ligne : www.tandfonline.com[...]

Land use changes in the northern Mediterranean basin threaten our ability to conserve its habitats and species. Reduced grazing has led to local declines in grassland species and colonization by forest species leading to conservation actions aimed at restoring open habitats. Recently, populations of Gagea lacaitae, a bulbous species typical of Mediterranean open xeric grasslands, have been discovered in forest clearings, an unexpected habitat for this species. Here, we surveyed 48 plots to characterize and compare the ecological niche of G. lacaitae growing in both open xeric and forest clearing habitats. We recorded ﬂoristic composition and plant cover and collected soil samples to measure water retention capacity, pH, organic matters and conductivity. Open xeric grasslands and forest clearings diﬀer in plant cover, community composition, and microhabitat structure but not in plant diversity, mean soil conditions, or G. lacaitae cover. Key similarities in conditions allow this species to persist in woodlands that heterogenous enough to include clearings. Such habitats have value for conserving this species and should be sustained.