Corresponding author: Carmelo Maria Musarella (
Academic editor: D. Geltman
Our understanding of the richness and uniqueness of the flora growing on gypsum substrates in Italy has grown significantly since the 19th century and, even today, new plant species are still being discovered. However, the plants and plant communities, growing on gypsum substrates in Italy, are still a relatively unknown subject.
The main aim of this paper was to elaborate a checklist of the Italian gypsophilous flora, to increase knowledge about this peculiar flora and for which conservation efforts need to be addressed.
Through a structured group communication process of experts (application of the Delphi technique), a remarkable number of experienced Italian botanists have joined together to select focal plant species linked to gypsum substrates. From the results obtained, 31 plant species behave as absolute or preferent taxa (gypsophytes and gypsoclines) and form the ‘core’ Italian gypsophilous flora. The most abundant life forms were chamaephytes and hemicryptophytes, belonging to
Musarella CM, Mendoza-Fernández AJ, Mota JF, Alessandrini A, Bacchetta G, Brullo S, Caldarella O, Ciaschetti G, Conti F, Martino L, Falci A, Gianguzzi L, Guarino R, Manzi A, Minissale P, Montanari S, Pasta S, Peruzzi L, Podda l, Sciandrello S, Scuderi L, Troia A, Spampinato G (2018) Checklist of gypsophilous vascular flora in Italy. PhytoKeys 103: 61–82.
The relationship between local bedrock types and vegetation cover has long been highlighted. Andrea Cesalpino, in
There is an abundance of accurate information concerning gypsophilous plant communities in Spain (
Therefore, the aims of this research were (i) to elaborate a checklist of Italian gypsophilous vascular flora through a structured group communication process of experts; (ii) to expand the knowledge of this flora type to which conservation efforts need to be addressed; (iii) to examine the spectrum of taxonomical groups, life forms and chorotypes of this flora. Through this approach, the comparison between the gypsophilous flora of Italy and that of other countries was carried out in order to detect common phylogenetic, functional and biogeographic patterns that allow a better understanding of the gypsophily phenomenon at European and global levels.
Several approaches have been proposed to elucidate which plant species can be considered as best linked to gypsum substrates (
The Delphi technique is a structured, anonymous and iterative survey undertaken by a panel of ‘experts’, which enables a group of individuals to collectively address a complex problem through a structured group communication process. This method has been applied in ecology to fill in data gaps (
Our scheme comprised two rounds of semi-structured questionnaires, each followed by an aggregation of responses and anonymous feedback from the experts. The number of rounds was limited and adapted according to the time available. An increased number of rounds would make the process more time-consuming.
A semi-structured survey, drawing from evidence based on published literature, was designed. The initial listing of taxa included species issuing from bibliographical references, which recorded the presence of these taxa on gypsum substrates (See Appendix 1: Methodology References for detailed information).
Participants from a great diversity of backgrounds were included (e.g. teachers, scientists, conservationists, non-governmental organisations, policy-makers, environmental managers and technicians) in order to obtain a wide range of perspectives and minimise bias arising from self-interest or information preferences. The participants included the co-authors of this article, i.e. experts situated in the Italian peninsula and Sardinia – hereinafter Italy (9) – and in Sicily (11). The reason why the number of Sicilian botanists involved is greater than those from mainland Italy is due to the considerable extension and importance that gypsum outcrops have in Sicily (Fig.
Italian gypsum outcrop presences in 10×10 km UTM grids.
Once the preliminary plant catalogue was elaborated, the complete list was submitted to the group of experts (
Likert scale ranking for the gypsophilous character of the taxa.
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Strictly gypsophile species; that is, species that do not live outside gypsum substrates (except accidentally). |
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Species with great preference for gypsum and which are found very rarely outside this substrate. |
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Species that live on gypsum, but which can also live on other substrates. If they live on many other different types of soil, they will not fit into this category. For example, if they live on limestone, marls and gypsum they could fall into this category. At least, it is as abundant (or almost) on gypsum as it is on other types of substrates. |
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Species that may be abundant on gypsum, although they could be even more frequent on other types of substrates. |
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Very rare species on gypsum or absent on this type of soil. |
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The collated responses from the first round were used to prepare a second questionnaire. The experts were requested to add new taxa candidates to be subsequently evaluated by the panel (
Information about plant species included in the checklist was collected: (i) taxonomic rank (
Considering that the plant species assessment was made with a quantitative but discontinuous scale, median values could be useful criteria for selecting the gypsophilous species (
Several statistical t-student and ANOVA tests were performed (SPSS ver. 22.0.0.0. IBM SPSS Statistics). Only taxa with gypsophily median values ≥2 were assessed in order to exclude ‘casual occurring taxa’. This analysis examined statistical differences between gypsum affinity (gypsophily), functional groups (narrow gypsophile, wide gypsophile and gypsovag) and distribution (Endemic, Mediterranean s.l., European, Eurasiatic/Widespread).
The first round of the questionnaire comprised 115 plant taxa. However, experts included more than 69% of other taxa growing on Italian gypsum substrates. This fact implied that, during the second round questionnaire, the panel of experts made assessments of 380 taxa (Suppl. material
The species in this catalogue belong to 59 different families. As far as the taxonomic spectrum of the 380 taxa is concerned, the most represented families were
The consensus, established amongst the responses of the panel of experts, produced the first checklist of Italian gypsophilous flora. A tiny group of 31 species out of the 380 preliminary taxa (8.16%) obtained median values over 3 from the experts’ assessments, so that they can be considered as gypsophiles or gypsoclines (Table
Checklist of Italian gypsophilous flora. Species are listed in decreasing order of Median. Life-form: Therophyte (T), Chamaephyte (Ch), Hemicryptophyte (H), Nanophanerophyte (NP), Geophyte (G). Distribution: Endemic (Endem.), Mediterranean (Medit.), Sub-Mediterranean (S-Medit.), European (Europ.), Widespread (Wide.). IUCN category: Endangered (EN), Least Concern (LC) species. Number of assessment (NA). Median (Median) and average (Mean) values of experts’ assessments. Standard deviation (SD). Median values from mainland Italy and Sicilian experts separately (Mainland Med/Sicily Med).
Species | Synonym | Family | Life form | Chorology | IUCN | NA | Score | Median | Mean | SD | Mainland Median | Sicily Median |
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T | S-Medit. | - | 11 | 55 | 5.00 | 5.00 | 0.00 | - | 5.00 | ||
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T | Medit. | - | 1 | 5 | 5.00 | 5.00 | - | - | 5.00 | ||
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Ch | Medit. | - | 11 | 51 | 5.00 | 4.64 | 0.67 | - | 5.00 | ||
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Ch | Endem. | - | 9 | 38 | 5.00 | 4.22 | 1.30 | - | 5.00 | ||
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H | Medit. | EN | 5 | 21 | 5.00 | 4.20 | 1.10 | 5.00 | 3.00 | ||
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Ch | Europ. | - | 2 | 9 | 4.50 | 4.50 | 0.71 | 5.00 | 4.00 | ||
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H | Endem. | LC | 5 | 21 | 4.00 | 4.20 | 0.84 | 4.50 | 4.00 | ||
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Ch | S-Medit. | - | 11 | 45 | 4.00 | 4.09 | 0.94 | - | 4.00 | ||
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Ch | Endem. | - | 11 | 43 | 4.00 | 3.91 | 1.30 | - | 4.00 | ||
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H | Endem. | - | 11 | 40 | 4.00 | 3.64 | 0.92 | - | 4.00 | ||
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H | Endem. | - | 5 | 18 | 4.00 | 3.60 | 1.67 | - | 4.00 | ||
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H | Endem. | - | 5 | 18 | 4.00 | 3.60 | 1.67 | - | 4.00 | ||
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NP | S-Medit. | - | 4 | 13 | 4.00 | 3.25 | 1.50 | - | 4.00 | ||
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Ch | Endem. | - | 11 | 36 | 3.00 | 3.27 | 0.90 | - | 3.00 | |
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Ch | Endem. | - | 1 | 3 | 3.00 | 3.00 | - | - | 3.00 | ||
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G | Europ. | - | 1 | 3 | 3.00 | 3.00 | - | 3.00 | - | ||
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G | Europ. | - | 1 | 3 | 3.00 | 3.00 | - | - | 3.00 | |
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H | Medit. | - | 4 | 11 | 3.00 | 2.75 | 0.50 | - | 3.00 | ||
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Ch | Europ. | - | 11 | 30 | 3.00 | 2.73 | 0.90 | 2.00 | 3.00 | |
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T | Endem. | - | 5 | 13 | 3.00 | 2.60 | 0.89 | - | 3.00 | ||
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H | Medit. | - | 7 | 18 | 3.00 | 2.57 | 0.79 | - | 3.00 | |
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T | Medit. | - | 9 | 23 | 3.00 | 2.56 | 0.53 | - | 3.00 | ||
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Ch | Medit. | - | 9 | 23 | 3.00 | 2.56 | 0.88 | 3.00 | 2.50 | ||
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H | Endem. | - | 11 | 28 | 3.00 | 2.55 | 1.13 | - | 3.00 | ||
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NP | Medit. | - | 11 | 28 | 3.00 | 2.55 | 0.82 | 1.00 | 3.00 | ||
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Ch | Medit. | - | 7 | 16 | 3.00 | 2.29 | 0.95 | - | 3.00 | ||
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H | S-Medit. | - | 9 | 20 | 3.00 | 2.22 | 0.97 | 3.00 | 2.50 | ||
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H | Medit. | - | 5 | 11 | 3.00 | 2.20 | 1.10 | - | 3.00 | ||
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T | Medit. | - | 5 | 11 | 3.00 | 2.20 | 1.10 | 1.00 | 3.00 | ||
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NP | Wide. | - | 5 | 11 | 3.00 | 2.20 | 1.10 | 1.00 | 3.00 | ||
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T | Medit. | - | 7 | 15 | 3.00 | 2.14 | 1.07 | 1.00 | 3.00 |
The 31 Italian gypsophilous taxa, on average, received 11 evaluations by experts (i.e. more than 55% of specialists evaluated this group): a result which increased the average number of assessments that the 380 taxa considered as the preliminary list received by more than 10%. Specifically, only the 9 species group composed of
Within the evaluation of the Italian Checklist of gypsophilous flora, 8 taxa obtained arithmetic-mean values higher than 4, whilst 8 taxa values were greater than or equal to 3. In the case of the median calculation, 5 species showed values equal to 5, 8 taxa reached values equal to or greater than 4 and 18 were equal to or above the median value 3.
The plant species on the Italian Checklist are present in 16 families (Figure
Percentage of gypsophile taxa grouping by taxonomic families and a comparison between Italian and Spanish Checklists (
Family | Italian Checklist | Spanish Checklist |
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3.23 | 1.41 |
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9.68 | 1.41 |
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6.45 | 14.08 |
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16.13 | 12.68 |
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– | 1.41 |
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3.23 | – |
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3.23 | 8.45 |
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3.23 | – |
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– | 4.23 |
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6.45 | 1.41 |
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– | 1.41 |
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3.23 | 9.86 |
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– | 1.41 |
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– | 1.41 |
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3.23 | 11.27 |
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3.23 | – |
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– | 1.41 |
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3.23 | 5.63 |
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6.45 | 12.68 |
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22.58 | 4.23 |
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– | 1.41 |
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3.23 | – |
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– | 4.23 |
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3.23 | – |
Percentage of taxa grouping by taxonomic families, life-forms and distribution and comparison between gypsophilous flora and preliminary data.
When the evaluations of the Sicilian experts are compared with those of experts from the peninsula (Table
Finally, in the case of Sardinia, where few gypsum outcrops are located in the northwest and in southeast of the island, local experts have highlighted the presence of three taxa (
Statistical tests (t-student) showed significant differences between the groups of Italian endemic plants versus species with a wider distribution; the Italian endemics obtained a higher average value of gypsophily (Table
In addition, when considering the clustering performed by distribution, the ANOVA analysis showed the existence of significant differences in gypsophily values between the Italian endemics and those showing both Mediterranean and European distribution. This is not so for species with a wider distribution range, such as Eurasian and widespread taxa. However, this result could be an artefact due to the small size of this sample, since its average gypsophily value is the one that most differed from the endemic species group (Table
Finally, according to the grouping variables narrow gypsophile, wide gypsophile and gypsovag, the species considered as narrow gypsophile, showed on average the highest gypsophily values and reached maximum values. Both species regarded as narrow gypsophile and wide gypsophile showed statistically significant results with higher gypsophily values than those considered as gypsovags. Nevertheless, there were no significant differences between the groups of narrow gypsophile and wide gypsophile, so that this separation was not supported (Table
For further information about the statistical analyses performed see Suppl. material
N | AV | SD | SE | 95% confidence interval | |||
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Min | Max | ||||||
Endemism | 46 | 2.4000 | 0.7731 | 0.1153 |
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2.1680 | 2.6320 |
Rest | 293 | 2.1460 | 0.4744 | 0.0285 | 2.0900 | 2.2020 | |
Total | 339 | 2.1810 | 0.5321 | 0.0296 | 2.1230 | 2.2390 |
* p-value < 0.05
ANOVA analysis by gypsophily level. Average (AV). Standard deviation (SD). 5a) Grouping by distribution: Italian endemic, Mediterranean, European and Wide distribution. 5b) Grouping by functional group: narrow gypsophile, wide gypsophile and gypsovag.
a) Chorotype | AV | SD | 95% confidence interval | |||
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Min | Max | |||||
Endemic | Mediterranean |
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0.0868 |
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0.0120 | 0.4600 |
European |
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0.1038 |
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0.0240 | 0.5600 | |
Eurasiat/Widespread | 0.3412 | 0.1498 | 0.1060 | -0.0460 | 0.7280 | |
Mediterranean | Endemic | - |
0.0868 |
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-0.4600 | -0.0120 |
European | 0.0558 | 0.0774 | 0.8890 | -0.1440 | 0.2560 | |
Eurasiat/Widespread | 0.1054 | 0.1329 | 0.8580 | -0.2380 | 0.4490 | |
European | Endemic | - |
0.1038 |
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-0.5600 | -0.0240 |
Mediterranean | -0.0558 | 0.0774 | 0.8890 | -0.2560 | 0.1440 | |
Eurasiat/Widespread | 0.0495 | 0.1446 | 0.9860 | -0.3240 | 0.4230 | |
Eurasiat/Widespread | Endemic | -0.3412 | 0.1498 | 0.1060 | -0.7280 | 0.0460 |
Mediterranean | -0.1054 | 0.1329 | 0.8580 | -0.4490 | 0.2380 | |
European | -0.0495 | 0.1446 | 0.9860 | -0.4230 | 0.3240 | |
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Narrow gypsophile | Wide gypsophile | 0.1524 | 0.1014 | 0.2910 | -0.0860 | 0.3910 |
Gypsovag |
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0.0848 |
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1.4690 | 1.8690 | |
Wide gypsophile | Narrow gypsophile | -0.1524 | 0.1014 | 0.2910 | -0.3910 | 0.0860 |
Gypsovag |
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0.0596 |
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1.3760 | 1.6570 | |
Gypsovag | Narrow gypsophile | - |
0.0848 |
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-1.8690 | -1.4690 |
Wide gypsophile | - |
0.0596 |
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-1.6570 | -1.3760 |
* p-value < 0.05
This work provides the first Checklist of Italian gypsophytes, including 31 taxa showing a great affinity for this substrate, 12 of which can be unequivocally considered as strictly gypsophytes. In addition, a number of further species often found on these substrates is detailed. As mentioned before, although the studies on gypsophilous flora in Italy date as far back as the 19th century (
This research reinforces the idea that, provided there is no definitive criterion for establishing whether a species is a gypsophyte or not, the inductive approach based on ‘expert criterion’ is not only plausible, but perhaps the only one possible to establish the groundwork for future research on gypsophily. To further complicate this scenario, the same species may have different affinity levels for gypsum substrates in isolated territories: e.g.
Both the taxonomical and life form spectra concerning the 31 gypsophytes on the Italian Checklist are largely in agreement with the data recorded in other areas of the Mediterranean Basin for this type of substrates (
Although there were variations in the abundance percentages, the most common families with the greatest match with the grouping occurred for the Spanish gypsophilous flora (
Plant formations linked to gypsum substrates are usually dominated by small plant species such as chamaephytes or hemicryptophytes, similarly to those which occur in other Mediterranean areas, although there are exceptions of woody plant formations growing on gypsum (
Efforts to ensure the conservation of Mediterranean gypsophilous vegetation, considered as a Priority Habitat, should be focused on endangered, rare or endemic species, according to the premises established by the EU. All these efforts cannot be easily undertaken unless it is previously determined which species, out of many hundreds, are to be given top priority. The approach adopted in this work may help both to focus on certain species and to detect research and conservation priorities. The high proportion of Italian endemic species and the geographic rarity component of the flora associated with Italian gypsum outcrops is an aspect that makes these outcrops very interesting habitats. However, the degree of threat to the gypsophilous flora in Italy could have been insufficiently assessed. This fact is confirmed since less than 7% of the gypsophytes of the Italian Checklist have been evaluated under IUCN protocol. As there has been a prior effort to establish a network of sites for the conservation of nature (Natura 2000 Network), it would be worthwhile to extend this initiative to areas supporting Italian gypsum outcrops that have biodiversity values worthy of consideration. In order to achieve this purpose, an in-depth review of the conservation status for both the gypsophilous flora and the natural areas where these substrata occur in Italy is crucial. Data generated by experts in conservation, for which threat categories of red-listed species are based, should be incorporated into nature protection Acts (
There are numerous SCI and SCZ including gypsum outcrops and their associated flora. The question that remains to be clarified is whether they are sufficient to ensure the conservation of this flora as well as the vegetation linked to this peculiar substrate. In this examination of gaps in conservation, fauna and other plant groups, such as lichens and bryophytes, should be integrated (
At this moment, the existence of endemic and rare flora with remarkable eco-morphological adaptations and the description of new taxa growing on gypsum outcrops fully justifies the conservation of these outcrops (
Data provided in this paper denote an important advance in this sense, because only five plant species in Italy have been recognised as characteristic taxa for this habitat on the European Red List of Habitats (
The study results from the international collaboration between the “Mediterranea” University of Reggio Calabria (Italy) and the University of Almeria (Spain). The authors Antonio Jesús Mendoza-Fernández and Carmelo Maria Musarella were sponsored by the University of Almeria through the Programme ‘Plan Propio de Investigación y Transferencia’, with a postdoctoral grant (Contrato Puente 2015) and financial assistance for their stay abroad (Estancias en otros Centros de Investigación 2016); and with support for guest teachers (Programa de Profesores Invitados 2017).
This study was carried out under the GYPWORLD Project, funded by the European Commission under the European Union’s Horizon 2020 Programme/MSCA-RISE-2017 Grant Agreement n. 777803.
We thank Beatrice Antolin and Edward Parker for reviewing the English version of the text.
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These authors contributed equally to the writing of this paper, the project and the first list of plants, coordinating the group, elaborating the data and editing the text. The other authors contributed by completing and evaluating the plant list.
Plant species data
ANOVA analysis by gypsophily level