# Calcicole

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{{Short description|Guild of plants}}
[[File:KAR Saupurzel 220506 03 Sonnenröschen.jpg|thumb|right|[Common rock-rose](/source/Common_rock-rose) forming low mats on shell limestone and sandy soil of the Saupurzel, a limestone hill in [Bavaria](/source/Bavaria)]]
Calcicoles—literally "[lime](/source/Lime_(material))‑dwellers"—are organisms, most commonly [vascular plant](/source/vascular_plant)s but also including [bryophyte](/source/bryophyte)s, [lichen](/source/lichen)s and other [taxa](/source/taxon), that grow preferentially on [calcium](/source/calcium)-rich, often [alkaline](/source/alkaline), [substrates](/source/substrate_(biology)). Because they grow only on specific lime-rich soils, calcicoles give ecologists a clear, real-world example of how [soil chemistry](/source/soil_chemistry) determines where organisms can live. Their distribution on [chalk](/source/chalk), [limestone](/source/limestone) and other [calcareous rock](/source/calcareous_rock)s reflects a suite of physiological adaptations that enable them to regulate cytosolic Ca<sup>2+</sup>, acquire otherwise insoluble [iron](/source/iron) and [phosphorus](/source/phosphorus), and withstand high [soil pH](/source/soil_pH). In contrast, calcifuges ("lime‑avoiders") dominate on acidic, [aluminium](/source/aluminium)‑rich soils. Modern research has linked the calcicole habit to indicators such as [Heinz Ellenberg](/source/Heinz_Ellenberg)'s soil‑reaction values and the Index of calcifugy, while [pharmacognostic](/source/Pharmacognosy) studies have uncovered an array of [bioactive compound](/source/bioactive_compound)s in many limestone specialists.<ref name="Parmar et al. 2024"/>

==Terminology and historical use==

The term calcicole entered the English botanical [lexicon](/source/lexicon) in 1895,<ref name="Parmar et al. 2024"/> when the Irish naturalist [Nathaniel Colgan](/source/Nathaniel_Colgan) applied it to the pyramidal orchid (''[Anacamptis pyramidalis](/source/Anacamptis_pyramidalis)'') growing on the lime‑rich soils of [County Dublin](/source/County_Dublin).<ref name="Colgan 1895"/> Earlier continental authors had used [cognate](/source/cognate) expressions such as ''calciphile'' and ''calciphyte'', but British and Irish field botanists adopted Colgan's wording almost immediately. Although alternative labels—acidofuge, lime lover—appear in the literature, calcicole remains dominant, in part because it highlights habitat rather than chemistry or physiology.<ref name="Parmar et al. 2024"/>

During the twentieth century, ecologists refined the concept by contrasting calcicoles with calcifuges and by recognising "strict" versus "non‑strict" calcicoles, depending on whether a species is confined to [calcareous soil](/source/calcareous_soil)s or merely favours them. Subsequent classifications divided the group further into obligate and facultative calcicoles on the basis of leaf Ca<sup>2+</sup>:Mg<sup>2+</sup> ratios, or into "extreme" and "moderate" calcicoles according to whether they require [pH](/source/pH) above 7 or tolerate pH 5–7.<ref name="Lee 1998"/><ref name="Parmar et al. 2024"/>

==Soil ecology and distribution==
[[File:Fern.1854.jpg|thumb|right|Holly fern rooted in alpine scree near the [tree line](/source/tree_line) in [Grindelwald](/source/Grindelwald), Switzerland]]
Calcicoles are conspicuous components of chalk [grassland](/source/grassland)s, [karst](/source/karst) shrublands and Mediterranean [garrigue](/source/garrigue), but they also occur on [serpentine](/source/Serpentine_soil) outcrops, metalliferous [spoil](/source/spoil_tip) and [anthropogenic](/source/Human_impact_on_the_environment) rubble where [calcium carbonate](/source/calcium_carbonate) buffers soil acidity. Families with many limestone specialists include [Asteraceae](/source/Asteraceae), [Caryophyllaceae](/source/Caryophyllaceae), [Poaceae](/source/Poaceae) and saxicolous (rock-dwelling) ferns such as ''[Asplenium](/source/Asplenium)'' and ''[Polystichum](/source/Polystichum)''. Mosses (such as ''[Tortula](/source/Tortula)'', ''[Grimmia](/source/Grimmia)'') and lichens (e.g. ''[Cladonia rangiformis](/source/Cladonia_rangiformis)'') likewise display calcicole–calcifuge pairs that partition the [microhabitat](/source/microhabitat).<ref name="Parmar et al. 2024"/> A 2024 global survey of "limestone ferns" estimates that calcicole species make up 8–13% of regional fern [flora](/source/flora)s (rising to more than 50% in some genera such as ''Asplenium'' and ''[Adiantum](/source/Adiantum)''), underlining the breadth of edaphic specialisation within the group.<ref name="Flores-Galván et al. 2024"/>

The geographic range of individual species may be narrow—''[Grevillea thelemanniana](/source/Grevillea_thelemanniana)'' is [endemic](/source/endemic) to a single limestone ridge in Western Australia—or continental, as with the grass ''[Sesleria caerulea](/source/Sesleria_caerulea)'', which extends from Ireland to the [Balkans](/source/Balkans). At landscape scale, patchy exposures of [marl](/source/marl) or [dolomite](/source/Dolomite_(mineral)) create [edaphic](/source/edaphic) islands that shape [genetic divergence](/source/genetic_divergence); population studies on ''[Ranunculus alpestris](/source/Ranunculus_alpestris)'' and other [alpine](/source/alpine_climate) calcicoles show historical isolation despite contemporary [gene flow](/source/gene_flow).<ref name="Parmar et al. 2024"/>

==Physiological adaptations==

Calcicoles avoid calcium toxicity through a combination of low root‑membrane affinity for Ca<sup>2+</sup>, sequestration of soluble Ca<sup>c+</sup> in [vacuole](/source/vacuole)s, and [precipitation](/source/precipitation) as [calcium oxalate](/source/calcium_oxalate) or [calcium phosphate](/source/calcium_phosphate)—often visible as crystals in [trichome](/source/trichome) tip cells and epidermal bladders. Such compartmentation doubles as an [osmotic](/source/osmosis) adjustment mechanism in drought‑prone limestone habitats.<ref name="Parmar et al. 2024"/>
[[File:Sesleria caerulea (s. str.) sl5.jpg|thumb|right|Blue moor-grass tussock (''[Sesleria caerulea](/source/Sesleria_caerulea)'') growing amongst hard carbonate rocks in [Mödling](/source/M%C3%B6dling), [Lower Austria](/source/Lower_Austria)]]
High pH reduces Fe<sup>3+</sup> and {{chem2|PO4(3-)}} [solubility](/source/solubility), yet calcicoles maintain [micronutrient](/source/micronutrient) supply by releasing [phytosiderophores](/source/phytosiderophores) and [carboxylate](/source/carboxylate)s ([citric](/source/citric_acid) and [oxalic acid](/source/oxalic_acid)s) that [chelate](/source/chelation) iron and mobilise phosphorus.<ref name="Zohlen & Tyler 2000"/> [Symbioses](/source/symbiosis) with [ecto](/source/ectomycorrhiza)‑ and [ericoid mycorrhiza](/source/ericoid_mycorrhiza)l fungi further enhance uptake: fungal [hypha](/source/hypha)e precipitate excess Ca<sup>2+</sup> externally while transporting Fe and P to the host. The IRONMAN (IMA) [peptide](/source/peptide) family fine-tunes these responses by adjusting root‑level Fe‑uptake genes in relation to [rhizosphere](/source/rhizosphere) pH.<ref name="Parmar et al. 2024"/>

Nitrogen nutrition also diverges between strategies. Calcicoles grow best on [nitrate](/source/nitrate)-derived nitrogen, whereas calcifuges tolerate [ammonium](/source/ammonium)-derived nitrogen; this difference, together with aluminium sensitivity in calcicoles, reinforces the edaphic split between the two guilds. Collectively, these traits illustrate how a single element—calcium—can dictate a complex ecological syndrome.<ref name="Parmar et al. 2024"/>

==Indicator values and assessment tools==

Quantitative indices permit rapid assignment of species to the calcicole–calcifuge spectrum. Etherington's Index of calcifugy expresses the proportion of a species' occurrences on soils with pH below 5.5 relative to all records; values near 0 identify strict calcicoles. Ellenberg's soil‑reaction (R) scale places most European calcicoles at R&nbsp;=&nbsp;7–9, whereas [Elias Landolt](/source/Elias_Landolt)'s Swiss system designates RL&nbsp;=&nbsp;5 (above pH 6.5) as a "strict calcicole" score. These [ordinal](/source/Ordinal_data) approaches, though region‑specific, have proved transferable after recalibration and now underpin vegetation monitoring across Europe and the Caucasus.<ref name="Parmar et al. 2024"/>

==Phytochemistry and pharmacological research==

Many calcicoles synthesise [secondary metabolite](/source/secondary_metabolite)s of medicinal interest. Beet (''[Beta vulgaris](/source/Beta_vulgaris)'') roots yield [betalain](/source/betalain)s with [anti-inflammatory](/source/anti-inflammatory) and nephroprotective effects, while ''[Leontodon hispidus](/source/Leontodon_hispidus)'' produces [hypocretenolide](/source/hypocretenolide)s active in topical [inflammation](/source/inflammation) models. [Polyphenol](/source/Polyphenol)‑rich extracts of ''[Anthyllis vulneraria](/source/Anthyllis_vulneraria)'', ''[Veronica spicata](/source/Veronica_spicata)'' and wheat (''[Triticum aestivum](/source/Triticum_aestivum)'') show [antioxidant](/source/antioxidant) capacity, and [saponin](/source/saponin)s from ''[Medicago sativa](/source/Medicago_sativa)'' inhibit ''[Candida albicans](/source/Candida_albicans)''. Antibacterial synergy between ''[Artemisia rupestris](/source/Artemisia_rupestris)'' [flavonoid](/source/flavonoid)s and [fluoroquinolone](/source/fluoroquinolone)s demonstrates the pharmaceutical potential of limestone floras, hitherto overlooked in [ethnobotanical](/source/ethnobotany) surveys.<ref name="Parmar et al. 2024"/>

==References==
{{Reflist|refs=

<ref name="Colgan 1895">{{cite journal |last=Colgan |first=Nathaniel |year=1895 |title=The orchids of Country Dublin |journal=The Irish Naturalist |volume=4 |issue=8 |pages=193–198 |jstor=25520847}}</ref>

<ref name="Flores-Galván et al. 2024">{{cite journal |last1=Flores-Galván |first1=Catalina |last2=Márquez-Guzmán |first2=Judith |last3=Mata-Rosas |first3=Martín |last4=Watkins |first4=James E. |last5=Mehltreter |first5=Klaus |title=Limestone ferns: a review of the substrate characteristics and species diversity in selected geographic regions and genera |journal=New Zealand Journal of Botany |year=2024 |doi=10.1080/0028825X.2024.2393294 |pages=1–18}}</ref>

<ref name="Lee 1998">{{cite journal |last=Lee |first=J.A. |year=1998 |title=The calcicole–calcifuge problem revisited |journal=Advances in Botanical Research |volume=29 |pages=1–30 |doi=10.1016/S0065-2296(08)60306-7}}</ref>

<ref name="Parmar et al. 2024">{{cite journal |last1=Parmar |first1=Ranjeet Kaur |last2=Arya |first2=Vikrant |last3=Gill |first3=Amandeep Kaur |last4=Thakur |first4=Vinay |title=Reclaiming calcicoles: new insights into lime lovers |journal=Journal of Pharmacology and Pharmacotherapeutics |year=2024 |volume=16 |pages=25–37 |doi=10.1177/0976500X241283120}}</ref>

<ref name="Zohlen & Tyler 2000">{{cite journal |last1=Zohlen |first1=Angelika |last2=Tyler |first2=Germund |year=2000 |title=Immobilization of tissue iron on calcareous soil: differences between calcicole and calcifuge plants |journal=Oikos |volume=89 |pages=95–106 |doi=10.1034/j.1600-0706.2000.890110.x}}</ref>

}}
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Category:Plant physiology

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Adapted from the Wikipedia article [Calcicole](https://en.wikipedia.org/wiki/Calcicole) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Calcicole?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.