• Proposed
  • Under Assessment
  • 3Preliminary Assessed
  • 4Assessed
  • 5Published

Acarospora placodiiformis H. Magn.

Search for another Species...

Scientific name
Acarospora placodiiformis
H. Magn.
Common names
IUCN Specialist Group
Assessment status
Under Assessment
Proposed by
Sergio Perez-Ortega
Sergio Perez-Ortega, Seth Ratcliffe
Christoph Scheidegger, Violeta Atienza
Comments etc.
André Aptroot, Ibai Olariaga Ibarguren, Rebecca Yahr, Anders Dahlberg, Toby Spribille

Assessment Notes


Acarospora placodiiformis is a placoid terricolous lichen exclusively associated with gypsum soils and dry continental climates in the Mediterranean and Irano-Anatolian Biodiversity Hotspots.

Currently known to occur in Spain, Morocco, Italy, Greece, Turkey and Iran It has an extent of occurrence in excess of 4,000,000 km2, greatly exceeding the threatened threshold values under criteria B1. While widespread, it is extremely rare across its range, and outside of Spain which is suspected to house the majority of the global population, is restricted to 6 isolated localities which are also suspected to be distinct sub-populations. While large areas of un-surveyed gypsum occur across North Africa, given its low density across its currently known range, it is suspected that its area of occupancy is between 600-3,000 km2 and it has 10 threatened locations.
No numerical population data is available, and the global population size is unknown with no evidence of severe fragmentation or extreme fluctuations. However, given its rarity at known localities and restricted habitat, the global population is suspected to be small and inferred to be declining. This being driven by a continuing decline in area of occupancy, area, extent and quality of habitat, and numbers of mature individuals due to gypsum mining, agricultural and urban expansion and soil erosion due to grazing and sporting activities across the majority of its range.

While there is uncertainty regarding its distribution, population size and structure. Given its restricted habitat and ongoing continuing declines, pending further research, a precautionary approach is applied and it is assessed as VU B2ab(ii,iii,v)

Taxonomic notes

The species is rather distinct. Within the genus Acarospora is one of the few terricolous placoid species. Acarospora nodulosa may be closely related and occurs in similar habitat, however it is easily distinguished by the presence of rhizocarpic acid in A. placodiiformis giving thalli a yellowish tinge, especially observed in young specimens and wet specimens.

Why suggested for a Global Red List Assessment?

The species seems to be a Mediterranean endemic exclusively associated with gypsum soils and dry continental climates. It shows a scattered distribution with records from Spain, Morocco, Italy, Greece, Iran, Germany (doubtful) and Turkey (US records not reliable). Major threats are: a) habitat loss by agricultural uses, trampling, urban pressure, mining and off-road motorcycling, b) low connectivity among populations,
Criterion A. We assume for this species a generation time of 30 years, estimating the time for population reduction record -and application of criterion A- in c. 100 years. There is scarce information about trends or population sizes in most of its distribution, however it seems that it is restricted to single localities in most of the countries. In Spain, where the species was described from, there is a clear and documented trend in the loss of habitat during the last century (Mota et al. 2011). The causes of habitat loss (changes in land use due to a change from grazing steppes to crop fields, gypsum, glauberit and thenardite mining, urban pressure, expansion of the road network) have not stop during the past decades, instead pressure has increased (Mota et al. 2010). Further, repopulation with Pinus pinaster has been the cause of severe losses of natural gypsum steppes during the past decades. Thus, according to subcriteria A2, A3 and A4 (a: direct observation & c: decline in the area of occupancy) the species may be assessed as Vulnerable. Population size reduction is estimated in c. ≥ 30% as a conservative approximation. 

Criterion B. According to current knowledge it is estimated that total area of occupancy is

< 2000 km2. The species is known from single populations in most of its distribution range but Spain where it is known from several localities. According to Mota et al. (2011) area of occupancy in Spain is not larger than 600 km2. Thus, total area of occupancy is smaller than 2000 Km2 (B2). Total number of locations is c. 10 (German record is doubtful) (B2a). It is clear that the range of this species has declined, at least in Spain -where most of the known populations occur- during the last century (B2b). Thus, it is estimated and inferred that there has been a continuous decline of (ii) area of occupancy, (iii) quality of habitat, (iv) number of subpopulations and likely (v) number of individuals during the last century. Since major threats have not stop (Mota et al. 2011) or even have increased, we project this trend will continue in the near future.

Criterion C. This criterion does not apply as no information about number of individuals and population size is available.

Criterion D. D1 subcriterion does not apply as no information about number of individuals is available. For D2 subcriterion AOO is larger than 20 km2 and number of populations is >

5, therefore the species is LC under D2.

Criterion E. This criterion does not apply as no quantitative analyses have been carried on.

Acarospora placodiiformis has been assessed as VU according to A2ac+ A3ac+ A4ac; B2ab(i,ii,iii,iv) at the European level.

According to FAO soils bulletin:62 there exist large extensions of gypsum soils in the North of Africa which have not been prospected for the occurrence of this species. Thus, we think that until the status of the species in those large areas are evaluated the species is assessed as Data Defficient at the world level.

Geographic range

This species occurs across the Mediterranean and Irano-Anatolian Biodiversity Hotspots and is exclusively associated with gypsum substrates and dry continental climates. It has a scattered occurrence, with records from Spain, Morocco, Italy, Greece, Turkey and Iran with occurrences from the United States and Germany being highly doubtful. It has an estimated extent of occurrence in excess of 4,000,000 km2, however, despite its very large EOO, its association with gypsum substrates excludes it from large parts of its known range. Apart from in Spain, it’s country of description and where survey effort is inferred to have been highest, it is known from single localities across all other countries where it occurs. This is true even in countries which have had comparable survey effort as Spain, such as Italy, and as such it is considered to have 10 threatened locations. It has a known area of occupancy of 136 km2. This is likely an underestimate, with the area of suitable gypsum habitat in Spain along being estimated as 600 km2 and large areas of un-surveyed potential habitat known to occur in North Africa (FAO Soils bulletin: 62). Despite this, given its rarity outside of Spain the upper boundary to its AOO is inferred to be less than 3,000 km2. In Spain, which is suspected to house the majority of the global population, potential habitat has decreased drastically during recent years due to ongoing land use change and agricultural and mining activities. Given its currently known distribution this is inferred to be leading to an overall continuing decline in area of occupancy.

Population and Trends

Rare across Spain and extremely rare where it is known to occur in other countries, its overall population size, while unknown, is suspected to be small. All known populations outside of Spain are separated by over 500 km. Following recommendations in Dalhberg and Muller (2011), these populations are suspected to be separate subpopulations, with Spain housing the majority of the global population. However, further research is required to confirm this. It is not known to be severely fragmented or subject to extreme fluctuations. The overall population trend is inferred to be declining due to an inferred continuing decline in the number of mature individuals driven by an inferred continuing decline in habitat and area of occupancy.

Population Trend: Decreasing

Habitat and Ecology

A terricolous placoid lichen, A. placodiiformis occurs exclusively over gypsum forming biocrusts with other species associated with this specialist substrate. However, A. placodiiformis shows the smallest distribution range of this set of species.


With a scattered and disjunct distribution and highly restricted habitat type, the loss and degradation of habitat is the major threat to this species, the drivers of which are varied.

Within Spain, where the majority of this species’ global population is thought to occur, gypsum continental steppes have long been used as traditional grazing areas. In recent years, these habitats have been extensively converted to agriculture, with remaining habitat being restricted to steep slopes unsuitable to agriculture. These restricted areas are further threatened by heavy cattle grazing and the associated trampling of the soil crust, and by sport activities such as off-road motorcycling. Other major threats are the expansion of urban centres such as Madrid, and gypsum, glauberit and thernadite mining. While the latter has occurred for centuries, especially gypsum mining, it has increased its intensity during the last two decades.

The lack of studies outside of Spain hinder the identification of active threats, however, agricultural and urban areas are visible in satellite imagery within close proximity to all of this species known localities and with gypsum being a valuable mineral globally, the threats active in Spain are inferred to be occurring across its range.

Housing & urban areasAgro-industry farmingAgro-industry grazing, ranching or farmingMining & quarryingRecreational activities

Conservation Actions

No specific conservation measures are known to be in place for this species and it is only known to occur in one protected area, a small micro reserve near Valencia, Spain. The development of effective conservation measures are hindered by the poor understanding of its overall population size, sub-population sizes and dynamics, and its distribution outside of Spain.

Site/area protection

Research needed

Dedicated research at known localities is required to calculate its overall population size, and the size and dynamics of all suspected subpopulations. Furthermore, dedicated surveys in areas of potential habitat are required across its range, with a focus on North Africa where large areas of gypsum are known to occur. If further individuals or populations are found, they should be provided with site protection. If further research is conducted, this assessment should be immediately updated in line with the findings.

Population size, distribution & trends

Use and Trade


Atienza, V. & Segarra, J.G. (2000) Preliminary red list of the lichens of the Valencian Community (eastern Spain).  Forest, Snow and Landscape Research 75(3): 391-400.
Casares-Porcel, M. & Gutiérrez-Carretero, L. (1993) Síntesis de la vegetación liquénica gipsícola termo- y mesomediterránea de la Península Ibérica -Cryptogamie, Bryologie-Lichénologie 14(4): 361-388.
Casares-Porcel, M., Gonzalez-Tejero, M.R. & Bouchaalah, A. (1994) Contribución al conocimiento de la flora liquénica gipsícola de Marruecos.  Cryptogamie, Bryologie-Lichénologie 15(3): 239-244.
Crespo, A. (1973). Composición florística de la costra de líquenes del Herniario-Teucrietum pumili de la provincia de Madrid. In Anales del Instituto Botanico AJ Cavanilles (Vol. 30, pp. 57-68).
exsiccata. Schlechtendalia 14: 49–53.
John, V. & Türk, A. (2006) Species/area curves for lichen on gypsum in Turkey. Mycologia Balcanica 3: 55-60.
Magnusson, A.H. (1956) A second supplement to the monograph of Acarospora with keys.  Goteborgs Kungl. Vetensk.- & Vitterhets.-Samhalles Handl., sjatte foljden ser. B 6(17): 1-34.
Mota, J. F., Sánchez-Gómez, P., & Guirado, J. S. (2011). Diversidad vegetal de las yeseras ibéricas. El reto de los archipiélagos edáficos para la biología de la conservación. ADIF-Mediterráneo Asesores Consultores, Almería.
Nimis, P.L., Poelt, J. & Tretiach, M. (1996) Lichens from the Gypsum Park of the northern Apennines (N Italy). - Cryptogamie, Bryologie-Lichénologie 17(1): 23-38.
STORDEUR, R. 2006: Lichenes selecti exsiccati ex Herbario Universitatis Halensis – a new
Valadbeigi, T. & Sipman, H. J. (2010). New records of lichens and lichenicolous fungi from Iran and their biogeographical significance. Mycotaxon,113(1), 191-194.
Wirth, V., Hauck, M., von Brackel, W., Cezanne, R., de Bruyn, U., Dürhammer, O., Eichler, M., Gnüchtel, A., Litterski, B., Otte, V., Schiefelbein, U., Scholz, P., Schultz, M., Stordeur, R., Feuerer, T., Heinrich, D., John, V. (2010): Checklist of lichens and lichenicolous fungi in Germany. Version #2: 19 January 2011. Georg August University of Göttingen: http://www.gwdg.de/~mhauck, Göttingen, Germany.
FAO soils bulletin 62. 1990. Management of gypsiferous soils, Food and Agriculture Organization of the United Nations. Soil Resources, Management, and Conservation Service. 81 pp.

Country occurrence

Regional Population and Trends

Country Trend Redlisted