Diversity of Marine and Brackish Macrophytes in the Port-Cros National Park (Provence, France, Mediterranean Sea): Taxa and Research Effort over Space and Time

: The terrestrial and marine Port-Cros National (PCNP) was established in 1963; it was then made up only of the Archipelago of Port-Cros. Since 2012, it has been extended to include a vast land and sea area, including not only islands but also part of the mainland, the new PCNP (N-PCNP); the marine core area and the adjacent marine area cover approximately 120,000 ha and extend over 63 km as the crow ﬂies, from east to west. Taxon richness is just one descriptor of biodiversity among others (e.g., functional and ecosystem diversity), and is far from being the most reliable one; however, it deserves to be taken into consideration, provided that certain prerequisites are met, because it constitutes a convenient measure of, e.g., the research effort and the diversity of habitats. The number of reported macrophyte taxa amounts to 502: 73 green algae, 316 red algae, 104 brown algae and 9 magnoliophyta and other taxa. Two new combinations are proposed: Ericaria brachycarpa var. claudiae and Gongolaria montagnei var. compressa . This gamma species diversity is far from being exceptionally high, but rather is within the norm for the Mediterranean, if we take into account the size of the area considered. The number of reported taxa per site is highly heterogeneous throughout the N-PCNP area; it is, as expected, correlated with the number of studies per site. The research effort peaked in the 1970–1980s, and then irregularly declined, which may seem surprising in this era of biodiversity launched at the 1992 Rio Summit. The exceptionally extensive database available, covering more than a century, provides the basis for a critical analysis of the concept of biodiversity, as proclaimed by the general public and the ‘greens’, which can be naive or biased, and of the concept of ‘heritage value species’, which the authors of this article consider to be a ‘toxic concept’, as opposed to ‘ordinary biodiversity’, which enables ecosystem functioning. However, this database, straddling both areas highly impacted by humans (coastal development, tourist resorts) and areas that are effectively protected, does not highlight obvious changes over time.


Introduction
A checklist of benthic macroalgae of the Gulf of Hyères and Hyères Islands (Porquerolles Island, Port-Cros Archipelago and Le Levant Island; Provence, France, Mediterranean Sea) was published by Belsher et al. [1]. Since then, considerable changes have taken place in the taxonomy of macroalgae, and numerous works have led to the discovery of hitherto unreported taxa.
We define macrophytes as multicellular photosynthetic organisms (MPOs). Here, we include within macrophytes non-cellular taxa, with millions of nuclei within a common cytoplasma, such as Caulerpa, and unicellular species forming large colonies, such as Palmophyllum and Chrysoreinhardia. Some protected areas in the Mediterranean, especially marine protected areas (MPAs), are no more than 'paper parks', i.e., fictitious protected areas, or 'mist parks', i.e., protected areas intended to fulfill the international commitments of states, often immense, having a real existence (director, premises, officials), but not implementing any real management measures involving, where necessary, constraints for some of the users [7][8][9][10][11][12]. In contrast with paper parks and mist parks, the PCNP, then the N-PNPC, are true protected Some protected areas in the Mediterranean, especially marine protected areas (MPAs), are no more than 'paper parks', i.e., fictitious protected areas, or 'mist parks', i.e., protected areas intended to fulfill the international commitments of states, often immense, having a real existence (director, premises, officials), but not implementing any real management measures involving, where necessary, constraints for some of the users [7][8][9][10][11][12]. In contrast with paper parks and mist parks, the PCNP, then the N-PNPC, are true protected areas [5,13]: in particular, since their creation, they have had a scientific council, a scientific strategy, a management plan, a strong scientific research effort based on the close collaboration between park staff and independent academic scientists, and of course the strict application of management measures which constitute constraints for some users whenever necessary [12][13][14][15][16].

Materials and Methods
We follow Boudouresque [2] for the taxonomy of higher taxa, Cormaci et al. [17] for Chlorobionta,  and Guiry and Guiry [21] for Rhodobionta and Cormaci et al. [22] for Phaeophyceae. In the few cases where we do not follow the treatment of these authors, we indicate it; we have also taken into account some subsequent articles (e.g., [23]). For each taxon, after the currently accepted name and the order (in parentheses), the names used by the cited authors, if different, are mentioned (in square brackets); such names are followed by correct authorities which could not correspond to those published by authors in the respective articles.
We have examined all of the literature dealing with marine macrophytes of the N-PCNP that we are aware of. This literature has been published in scientific journals (including the PCNP journal, Scientific Reports of Port-Cros National Park, 35 volumes of which have been published since its launch in 1975); it also includes unpublished reports (grey literature), kept at the PCNP headquarters (in Hyères-les-Palmiers) and in various libraries, including that of the Macrophyte platform of the MIO (Mediterranean Institute of Oceanography), at Aix-Marseille University [5,16]. Whenever publications clearly constitute duplicates (e.g., a report, a communication at a congress and the corresponding scientific article, or two articles strictly based on the same dataset), for example [24,25], or [26,27], we considered only one of them. Similarly, we did not consider checklists that simply repeat articles cited elsewhere (e.g., [28]). Of course, some duplicates may have escaped our attention, but their effect on the interpretation of the dataset is probably negligible.
The starting point of our literature research is 1900. Older records may exist. However, eastern Provence was little frequented by botanists in the 18th and 19th centuries. Moreover, when they exist, records were not accurately localized. In the case of Fucales (brown algae), Aurélie Blanfuné and Thierry Thibaut have explored (as far as N-PCNP is concerned) the literature and the herbaria prior to 1900 [33][34][35]: the rare records concern the zone outside the N-PNPC, with the exception of Ericaria crinita (Porquerolles Island). The oldest records are therefore those of Mouret in 1911 [36]. Marcellin Mouret (1881Mouret ( -1915 was a French soldier and botanist; he was posted to Martinique (French West Indies), Morocco and French Indochina and managed to assemble herbaria completed with notes and drawings, despite his military duties; during World War I, Lieutenant Mouret was wounded in August 1914, then was killed in March 1915 while launching an assault at the head of his company [37].

How Many Taxa?
In 1976, Belsher et al. [1] listed 335 taxa and stadia (life stages) of green, red and brown macroalgae for the Gulf of Hyères and Hyères islands, including the Port-Cros Archipelago, the latter then constituting the Port-Cros National Park (PCNP). The present updated checklist identifies 502 taxa, on a slightly different scale, that of the N-PCNP, from La Garde to Ramatuelle (eastern Provence) (Figure 1), and a slightly different taxonomic format, macrophytes (including seagrasses) instead of macroalgae. As far as the Port-Cros Archipelago is concerned, the number of recorded taxa was 285 in 1976 [1], 284 in 1981 [58], 353 in 1985 [28] and 441 (present study).
Such gamma species diversity (see [203] for the concept of diversity) is not low, but far from particularly high: it falls just within the norm for a size-diversity relationship in the Mediterranean (Table 1). In addition, the research effort in the AMA of the N-PCNP has been particularly strong (see Section 4.3), which would imply that exceptionally high numbers of taxa might be expected. This may disappoint those who, on the basis of an old conception of biodiversity (see e.g., [5] for criticism), believe that a national park necessarily harbours high gamma species diversity, and that only high species diversity deserves to be protected. For the tiny Isole dei Ciclopi (Sicily) and the Principality of Monaco (French Riviera), 380 and 365 taxa and stages have been reported, respectively (Table 1). Overall, the number of taxa reported from the N-PCNP represents 40 to 55% of the Mediterranean epsilon diversity (Table 2). Table 1. Epsilon taxon diversity of macrophytes in a number of Mediterranean areas. The maximum distance (as the crow flies) between the outer limits of the area was used as a proxy for its size. Note that the research effort differs between areas.   Cormaci et al. (2012Cormaci et al. ( , 2014Cormaci et al. ( , 2017Cormaci et al. ( , 2020Cormaci et al. ( , 2021, but sometimes other authors, such as Guiry and Guiry (2022), are followed: see text in Section 3 for details. A higher number of species was reported from Giens Peninsula, Porquerolles Island and the Port-Cros Archipelago than in other, less explored (see below) localities and sites. Some large species, easy to identify and therefore unlikely to be missed, have been only found at mainland localities and sites, but not at Porquerolles Island, Port-Cros Archipelago and Le Levant Island: Alsidium helminthochorton, Digenea simplex, Halopithys incurva and the gametogene of Asparagopsis armata; a lower mean sea surface temperature, at offshore islands than at mainland areas, may account for these observations. Other large species, some of them of cold affinities, such as Calliblepharis ciliata, C. jubata, Gymnogongrus crenulatus, Lomentaria articulata and Spatoglossum solieri, were only reported from offshore islands.

Area Size Number of Taxa Reference
The increase over time in the cumulative number of taxa presents two major phases: the foundational work of Mouret [36] in 1911 and the bulk of taxonomic and ecological studies of the 1970-1980s (e.g., [1,39,49,51]) ( Figure 2).
It is worth underlining that such a cumulative checklist, although useful and even essential for management purposes, must be handled with caution. For some civil servants of state agencies (e.g., in France the Ministry of the Environment and the Service Patrimoine of the Muséum National d'Histoire Naturelle), the production of these inventories sometimes constitutes in a way a goal in itself, and the paradigm of biodiversity, whereas it is rather a caricature of the concept of biodiversity, and the opposite of an ecosystembased approach to biodiversity. Biodiversity is a multidimensional concept, encompassing levels of complexity from within species to across ecosystems: evolutionary scale (from genes to species and kingdoms); functional scale; organizational scale (from patches to landscapes/seascapes); spatial scale; and heterogeneity scale [203,[217][218][219]. This naive approach to biodiversity, this race for the maximum number of species ('my list of species is longer than yours!') can have several perverse effects: (i) It can divert a disproportionate amount of human and financial resources for the production of lists of species whose value is more arithmetical than ecological, although they are obviously necessary. (ii) It helps to 'deify' the number of species, whereas it is just one descriptor of biodiversity among others, and this descriptor is far from being the most relevant, in contrast with functional diversity and ecosystem diversity. (iii) It contributes to the general public's belief that the greater the number of species in an area, the more this area deserves protection. (iv) It equates species that are important because of their rarity, or the role they play in ecosystems, or which are abundant, with species that occur incidentally, are sometimes observed only once, and are therefore without ecological and biogeographical significance. (v) It underestimates 'ordinary biodiversity', which might be seen as 'the biodiversity of the people', that ensures the functioning of ecosystems throughout the year, in favor of biodiversity that is in a way 'aristocratic', qualified as 'heritage value species'. The term 'heritage value species' is very vague and even fuzzy: it covers truly rare and/or threatened species, attractive and human-friendly species, species supported by taxonomic lobbies (e.g., bird, bat and sea mammal lobbies), and legitimately protected species together with not legitimately protected species, species that are just protected thanks to taxonomic lobbies. ago and Le Levant Island: Alsidium helminthochorton, Digenea simplex, Halopithys incurva and the gametogene of Asparagopsis armata; a lower mean sea surface temperature, at offshore islands than at mainland areas, may account for these observations. Other large species, some of them of cold affinities, such as Calliblepharis ciliata, C. jubata, Gymnogongrus crenulatus, Lomentaria articulata and Spatoglossum solieri, were only reported from offshore islands.
The increase over time in the cumulative number of taxa presents two major phases: the foundational work of Mouret [36] in 1911 and the bulk of taxonomic and ecological studies of the 1970-1980s (e.g., [1,39,49,51]) ( Figure 2). It is worth underlining that such a cumulative checklist, although useful and even essential for management purposes, must be handled with caution. For some civil servants of state agencies (e.g., in France the Ministry of the Environment and the Service Patrimoine of the Muséum National d'Histoire Naturelle), the production of these inventories sometimes constitutes in a way a goal in itself, and the paradigm of biodiversity, whereas it is rather a caricature of the concept of biodiversity, and the opposite of an ecosystembased approach to biodiversity. Biodiversity is a multidimensional concept, encompassing levels of complexity from within species to across ecosystems: evolutionary scale (from genes to species and kingdoms); functional scale; organizational scale (from patches to landscapes/seascapes); spatial scale; and heterogeneity scale [203,[217][218][219]. This naive approach to biodiversity, this race for the maximum number of species ('my list of species is longer than yours!') can have several perverse effects: (i) It can divert a disproportionate amount of human and financial resources for the production of lists of species whose value is more arithmetical than ecological, although they are obviously necessary. (ii) It helps to 'deify' the number of species, whereas it is just one descriptor of biodiversity among others, and this descriptor is far from being the most relevant, in contrast with functional diversity and ecosystem diversity. (iii) It contributes to the general public's be- Of course, the species gamma diversity may be underestimated in the framework of the present study. On the one hand, taxonomic expertise and research effort have declined over time (see below). On the other hand, partly following from the first point, species newly described elsewhere in the Mediterranean were not searched for in the N-PCNP. For example, Dictyopteris lucida M.A. Ribera Siguán, A. Gómez Garreta, Pérez Ruzafa, Barceló Martí et Rull Lluch, previously confused with D. polypodioides [220], Lithophyllum pseudoracemus Caragnano, Rodondi et Rindi, previously confused with L. racemus [221] and the cryptic species hitherto confused as Padina pavonica [222].
In the middle of the 20th century, Elton (ecological resistance theory-ERT) [229] claimed that low species diversity and disturbance favored biological invasions. As a matter of fact, ERT is today widely challenged. At least in the marine realm, species richness usually enhances biological invasions (ecological acceptance hypothesis-EAH) [230][231][232]. In fact, the probability of introduction does not depend upon species richness and disturbances, but on the presence of a vector, e.g., a harbour or aquaculture facilities; for this reason, the N-PCNP is less affected by introduced species than, e.g., the Calanques National Park (western Provence), adjacent to the port of Marseilles, and Thau Lagoon in Occitania, a major shellfish aquaculture area [40,204,233]. As already pointed out by a host of authors (e.g., [234][235][236][237][238]), invasive species do not respect the boundaries of marine protected areas (MPAs).

The Research Effort over Space and Time
The different parts of the adjacent marine area (AMA) of the N-PCNP have been studied very heterogeneously: from 3 to 94 documents per site (Figure 3). The fact that the size of the sites (surface area, length of coastline) is very heterogeneous does not in itself explain the differences in the number of taxa per site (from 2-La Garde to 441-Port-Cros Archipelago). As intuitively expected, there is a significant correlation (r = 0.69, p < 0.001) between the number of references (a clue for research effort) and the cumulative number of reported taxa (Figure 4).   The fact that the archipelago of Port-Cros (PCA) has been, by far, the site which benefited from the most important research effort, is unsurprising: it was the initial site of the Port-Cros National Park (PCNP) and, since 2012, is one of the two core areas of the N-PCNP. It is widely accepted that we only effectively protect what we know well [6,14,16,240]. Unfortunately, the other side of the coin is that 'ordinary biodiversity', as pointed out above, has been neglected. We are witnessing a kind of opposition between the biodiversity of most of the territory, poorly known and which would not interest scientists and managers (which of course is not really the case), and the biodiversity of the core area of the PCNP, supposedly more central and worthy of interest: plebeian versus aristocratic, deluxe, biodiversity?   The number of items (i.e., reporting of a taxon, at a given site, by a given reference) peaked in the 1970-1980s, then declined in the 1990s, before a partial recovery in the 2000s ( Figure 5). The extinction of taxonomists, in the age of biodiversity, is a recurring topic in the literature (e.g., [241,242]). This extinction of taxonomists constitutes a paradox, insofar as the general public believes that, since 1992 and the Rio summit, taxonomy has won acclaim and has expanded in a significant way. In fact, according to many authors, the biodiversity concept has been stolen by molecular biologists, by taxonomic lobbies, by 'green' activists with no real interest in scientific ecology and by often whimsical database manipulators [243][244][245]. The result is that there are fewer and fewer taxonomists able to put a name to a taxon, and more and more 'parasitic researchers', unable to distinguish a mouse from an elephant (in the absence of a genetic analysis; of course an exaggeration!), but experts in modelling, based upon doubtful databases and interpretations dating back to the prehistory of ecology [242]. In the study area, the decline in the taxonomic research effort, from the 1970-1980s, is obvious ( Figure 5).
The heterogeneity of scientific exploration also concerns habitats. Intertidal habitats have long been favored by scientists. Since the advent of scuba diving, the opposite has happened. The relative scarcity of reports of intertidal species, probably present everywhere, such as Pyropia elongata, Nemoderma tingitanum and Pseudoralfsia verrucosa, can be explained in this way.
The scientific strategy of the Port-Cros National Park [14] explicitly involved plans to explore the new territories of the N-PCNP, those of its vast AMA. For the moment, this is far from being achieved (Figure 3). In the 2000s, as part of the establishment of Natura 2000 areas programmed by the European 'Habitat Directive' of 1992, studies were carried out [47,68,72]. However, they were unfortunately based on minimalist lists of protected species, on the 'toxic' concept of heritage value species and on the doctrine of the French Ministry of the Environment [10,246,247]. manipulators [243][244][245]. The result is that there are fewer and fewer taxonomists able to put a name to a taxon, and more and more 'parasitic researchers', unable to distinguish a mouse from an elephant (in the absence of a genetic analysis; of course an exaggeration!), but experts in modelling, based upon doubtful databases and interpretations dating back to the prehistory of ecology [242]. In the study area, the decline in the taxonomic research effort, from the 1970-1980s, is obvious ( Figure 5). The heterogeneity of scientific exploration also concerns habitats. Intertidal habitats have long been favored by scientists. Since the advent of scuba diving, the opposite has

Are Some Taxa Locally Extinct?
The year of the last sighting of a taxon in the study area can date back from a few years to more than a century (Table 3). Overall, 50% of the taxa have not been reported for 30 years and almost 10% for more than 50 years (Table 3). Could we consider that the latter are locally extinct? In some cases, we can suspect errors of identification, e.g., Polysiphonia deusta and Phyllophora sicula, only reported by Mouret in 1911 [36], and Corallina officinalis, only reported by Fredj in 1964 [94], who was not known as a phycologist. However, this is not the case with, e.g., Alsidium helminthochorton, Gelidum spathulatum, Gymnogongrus griffithsiae, Hildenbrandia prototypus, Lithophyllum racemus, Pyropia elongata, Sphaerococcus rhizophylloides and Petalonia fascia, large and well-characterized species which are not prone to misidentification.
For a number of 'missing' species, the lack of recent investigations, perhaps also the decline in the taxonomic expertise, may account for the absence of sightings. This is not the case with some Fucales of the genera Cystoseira, Ericaria, Gongolaria and Sargassum, for which the identification expertise is fortunately not lost (e.g., [25,[33][34][35]189]).

Are There Clues to Climate Warming?
Species, on the basis of their presence or absence, and the spread of their range area, are the best biological indicators of the current warming [248][249][250][251]. This contrasts with inter-annual fluctuations of physical parameters, so sharply that contemporaries of the Late Bronze Age (LBA;~1000 BCE), the Dark Age Cold Period and the Fall of the Roman Empire (DACP;~500 CE) and the Little Ice Age (LIA;~1800 CE) never perceived that civilization was sinking into a climatic episode rather than into changes triggered by the decadence of morals or the errors of the politicians of the time [252][253][254][255]. A number of macrophyte species are regarded as thermophilous. As a result, they are expected to spread northwards in the Mediterranean Sea. In the N-PCNP area, the year of first report of thermophilous macrophytes is 1911 (Dasycladus vermicularis, Hypnea musciformis and Rytiphlaea tinctoria), 1953 (Caulerpa prolifera), 1971 (Spyridia filamentosa), 1976 (Anadyomene stellata and Lobophora variegata), 1977 (Cladophoropsis membranacea), 1987 (Taenioma nanum), 2009 (Hydrochlathrus clathratus), 2019 (Microdictyon umbilicatum) and 2022 (Lophocladia lallemandii).
Overall, the increase in the presence of thermophilous species is not obvious. The possible increase in their abundance would be of more significance, but no data are available. This reinforces the perception of a stronger impact of global warming on the human target than on the biodiversity target (see, e.g., [11,225]).
At the same time, have species of cold affinity disappeared? The only species which seems to offer an affirmative answer to this question is the brown alga Scytosiphon lomentaria, never sighted since the years 1960-1970.

Conclusions
The diversity of macrophytes within the new Port-Cros National Park (N-PCNP) is not exceptionally high. However, this observation must be put in the light of the very patchy knowledge of the territory: the research effort has mainly focused on the Port-Cros Archipelago, the original area of the Port-Cros National Park (PCNP), founded in 1963. This diversity is known through two highpoints of research effort: the early 20th century and the 1960-1970s. Since then, the research effort has declined: contrary to popular belief, in the midst of the current so-called era of biodiversity launched by the 1992 Rio Summit, knowledge of biodiversity has not increased and may even have declined.
It should also be stressed that species diversity (how many species?), often idolized by political ecologists (successors of the prehistory of ecology), taxonomic lobbies, the general public and managers, is a very poor indicator of biodiversity. The concept of biodiversity is actually very different from, and much broader than, species richness.
Heritage value species, sometimes regarded as the paradigm of biodiversity, constitute a vague and fuzzy concept, a kind of aristocratic concept as opposed to the ordinary diversity that keeps the ecosystems of the real world functioning.
However, although the inventory of species is a poor descriptor of biodiversity, it is an essential prerequisite for the study of human impact, global change and in particular the impact of climate change.
The database that we present here is unique because it concerns an area (i) in part strongly impacted by humans, mainland Provence, strongly urbanized and with worldfamous tourist resorts, and (ii) in part efficiently protected since the middle of the 20th century, the offshore islands bordering the Gulf of Hyères. However, it does not offer the means to highlight an obvious change in the flora over time, in relation with, e.g., urbanization, tourism and warming, either because it is not suited to a study of that kind, or because the change is (for the moment) more tenuous than is generally thought.

Data Availability Statement:
The data presented in this study are available on request from the corresponding author.