Seven Forms Of Rarity And Their Frequency In The Flora Of The British Isles Pdf

seven forms of rarity and their frequency in the flora of the british isles pdf

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Deborah Rabinowitz September 9, — August 18, was an ecologist who coined the seven meanings of rarity in the field of plant ecology ,. She attended public schools and later received her undergraduate degree in biology from New College of Florida in Sarasota.

Seven forms of rarity and their frequency in the flora of the British Isles

Minerals that conform to criterion 1, 2, or 3 are inherently rare, whereas those matching criterion 4 may be much more common than represented by reported occurrences. Many rare minerals have unique crystal structures or reveal the crystal chemical plasticity of well-known structures, as dramatically illustrated by the minerals of boron. The distribution of rare minerals may thus be a robust biosignature, while these phases individually and collectively exemplify the co-evolution of the geosphere and biosphere.

Finally, mineralogical rarities, as with novelty in other natural domains, are inherently fascinating. By contrast, most minerals are volumetrically insignificant and scarce.

Rock-forming minerals understandably attract the greatest attention in the mineralogical literature, whereas the discovery of new minerals, which are usually extremely rare, no longer represents the central pursuit of many mineralogists. To what extent, therefore, are rare minerals important in understanding Earth?

This topic is informed by investigations of rare biological species, which have been examined in the context of ecosystem diversity and stability Rabinowitz ; Rabinowitz et al. Concerns about loss of diversity through extinction of rare species have provided a special focus Lyons et al. Recent results suggest that rare species may contribute unique ecological functions, including resistance to climate change, drought, or fire, and thus their loss may disproportionately affect the robustness of an ecosystem Jain et al.

In a classic contribution, Deborah Rabinowitz proposed a taxonomy of biological rarity. She recognized that three factors—abundance, geographic range, and habitat restrictions—collectively contribute to rarity, as illustrated schematically in a dissected cube Fig. Subsequent studies have expanded on this foundation by examining factors that may influence sampling efficiency; for example, biases resulting from inadequate sampling time Zhang et al.

The Rabinowitz scheme, which has been applied to a range of ecosystems e. Other octants of this dissected cube delineate seven types of biological rarity. Note, however, that all three axes correspond to continuous parameters; therefore, divisions between wide vs. This visualization, furthermore, does not include effects of sampling biases on perceptions of species rarity.

It is therefore useful to consider the nature of rarity in mineralogy. In this essay we follow the lead of ecologists, cataloging the varied causes of rarity in the mineral kingdom and considering the scientific significance of these uncommon phases. However, diamond, ruby, emerald, and other precious gems are found at numerous localities and are sold in commercial quantities, and thus are not rare in the sense used in this contribution.

Note that alternative definitions of rarity, for example based on total crustal volume or mass of each mineral, might be proposed. However, a metric based on numbers of localities has the advantage of reproducibility through the open access data resource mindat. We find that minerals known from 5 or fewer localities are rare for four different reasons. Every rare mineral conforms to one or more of these four distinct categories Fig. Taxonomy of mineralogical rarity: Commoner species, represented by the upper left-hand shaded octant, must incorporate common chemical elements, have a large volume of phase stability in P-T-X space, and be stable.

The other seven octants represent different types of rarer species. As with Figure 1 , the three axes of this figure correspond to continous scales, for example from smaller to larger volume of stability in P-T-X space. Thus, any partitioning of mineral species into octants is inherently arbitrary. Note also that this visualization does not include the effects of sampling bias on perceptions of species rarity.

Restricted phase stability in P-T-X space: The first category of mineral rarities arises because different phases have different ranges of stability in multi-dimensional pressure-temperature-composition P-T-X space where composition typically refers to numerous coexisting elements. On the one hand, the commonest rock-forming minerals display wide ranges of P-T-X stability.

By contrast, some rare phases, even though formed from relatively common elements, display extremely limited P-T-X stability fields and thus form only under idiosyncratic conditions Table 1. For example, harmunite CaFe2O4; Galuskina et al. Similarly, hatrurite Ca3SiO5; Gross is listed on mindat. We also suggest that the extreme rarity of several zeolites recorded at only one or two localities in mindat. Zeolites display modular framework crystal structures with interconnected 4-, 6-, and 8-member tetrahedral rings that form a rich variety of channels and cavities, so small changes in the ratios of cations, as well as in the P-T conditions of formation, can lead to many new phases Bish and Ming ; Bellussi et al.

Selected rare minerals defined as occurring at five or fewer localities on mindat. Special cases of restricted mineral stabilities arise from extremes of eH and pH. The exceptionally acidic conditions of some hot springs and weathered sulfide environments with reported pH as low as —3. The great contrasts among stability ranges of minerals point to as yet unexplored aspects of the topological distribution of phases in P-T-X space.

IMA approved minerals incorporate 72 different chemical elements that are reported as essential in one or more minerals. Furthermore, the numbers of species containing each of these elements is, to a significant degree, correlated with the crustal abundance of the element Christy ; Hazen et al. Two caveats are required. In spite of these issues, it seems likely that the number of different mineral species to be found on a terrestrial planet or moon will be a direct consequence of phase topology in combination with the extent of mineral evolution on the body.

Mineral diversity, including the presence of rare minerals, will reflect the total P-T-X range available on that planetary body, coupled with the statistical distribution of phase topologies. Investigations of the relationship between mineral diversity and phase space may thus prove to be of interest, both in characterizing the variety of rocky planets and in developing a deeper understanding of phase topology. Many additional rare minerals, as well as thousands of potential minerals that are known as synthetic phases but have not yet been discovered naturally, require the incorporation of two or more elements that seldom occur together and thus are far rarer than would be expected from their crustal abundances.

A few minerals incorporate nine or more chemical elements in combinations that point to rare, if not unique, geochemical environments Table 1.

Unlike the first category of rarities that arise from limited stability in P-T-X space, many of the scarce minerals in category 2 have extensive P-T-X stability ranges. Rarity emerges from the nature of cosmochemistry and the idiosyncrasies of unusual geochemical environments on Earth, as opposed to restrictions imposed by phase topology. Also, as with phase space, there exists no obvious metric of rarity for combinations of elements. It might be tempting to employ crustal abundances of elements to quantify the compositional axis e.

For example, hafnium with a crustal abundance of 5. Thus, no simple measure yet exists for compositional rarity, which must for the present remain a qualitative characteristic of minerals. A third category of mineral rarities includes numerous phases that form under varied non-ambient conditions but degrade quickly at ambient conditions.

Minerals can be ephemeral for several reasons. Phases that melt or evaporate at ambient conditions are rarely represented in mineral collections.

Similarly, the crystalline form of CO 2 , which is only stable below — Other phases that melt or evaporate under most surface conditions include acetamide, hydrohalite, and meridianiite Table 1. Hygroscopic phases that rapidly hydrate Table 1 may also be more common than is reflected in mineral collections.

Magnesium sulfate MgSO 4 , though well known as a synthetic compound, has not yet been found in nature. Lime CaO , similarly, is recorded from fewer than 10 localities, in contrast to the common hydrated daughter mineral, portlandite [Ca OH 2 ].

By contrast, several uncommon minerals are unstable in part because they readily dehydrate upon exposure to air Table 1. Water-soluble minerals may also be under-reported, and thus appear to be rare. More than evaporite mineral species, including halides, borates, and nitrates, can persist in dry evaporite environments for many years, only to be washed away during rare rain events. Similarly, water-soluble phases that form in volcanic fumeroles may form intermittently and then dissolve with each subsequent rainstorm.

Other water-soluble phases that may be under-reported occur in a wide variety of environments, including oxidized zones of ore bodies, carbonatite lavas, alkaline massifs, coal mine waste dumps, bat guano, fossilized wood, mine fires, and high-temperature metamorphic assemblages Table 1.

Among the least stable minerals are rare species that are deliquescent—both adsorbing moisture from the air and then dissolving in it. Finally, a few rare minerals, including edoylerite, metasideronatrite, and sideronatrite, are photosensitive and gradually decompose when exposed to sunlight.

The phases enumerated in Table 1 and many more may degrade in less than a day. However, many unstable or metastable minerals transform more slowly. Many Hg minerals, for example, are known to evaporate gradually; thus, more than half of IMA approved mercury minerals are known only from deposits younger than 50 million years Hazen et al.

Similarly, borates, nitrates, and halides that are stable for thousands of years in evaporite deposits may, nevertheless, be ephemeral over time scales of millions of years.

Grew et al. Thus, gradual loss of some Hg and B minerals may contribute to their relative rarity. A significant number of rare minerals may be poorly documented because they are either difficult to recognize based on their appearance, occur only at the micro- or nano-scale, or are found in under-sampled lithological contexts.

Thus, some minerals are rare because they are exceptionally problematic to recognize in hand specimen; notably a pale color and lack of distinctive crystal morphology leads to difficulty in identification.

For example, Hazen et al. Rare sodium minerals, thus, may be significantly under-reported, while a significant fraction of sodium minerals remains undiscovered. At the extremes of scale, several new minerals have been discovered only as micro- or nano-phases.

These microscopic minerals, and many others yet to be discovered, are likely to be more common than implied by numbers of known localities. For example, several rare tellurium minerals known only from Otto Mountain, California, have been discovered through intensive application of microscopy and electron microprobe analysis of specimens from that deposit Housely et al.

These minerals are intrinsically uncommon, but their rarity may be exaggerated because of the technical difficulties in finding and characterizing such microscopic phases. The application of transmission electron microscopy to the discovery of new minerals, thus far applied primarily to meteorite phases, has led to descriptions of species such as hutcheonite and allendeite, which may remain rare by virtue of the difficulty and expense of the analytical technique Table 1 ; Ma and Krot ; Ma et al.

These extraterrestrial phases, and many others awaiting discovery on Earth, are certainly volumetrically insignificant, but they may occur much more commonly than is implied by a list of their known localities. We suspect that numerous other nano-minerals await discovery, and all will be rare by virtue of their miniscule grain size. Minerals from Antarctica, deep-ocean minerals notably those formed at sub-surface volcanic vents , and phases that grow in aqueous environments at extremes of temperature or pH, crustal environments at elevated pressures, or in volcanic fumaroles, are all from mineral-forming environments to which access is challenging and thus may be under-represented in mineral collections.

It should be noted that positive sampling biases also likely affect our perceptions of mineral rarity. Intensive searches for deposits of rare elements such as Au, Cd, Co, Ge, U, and the rare earths have undoubtedly led to the discovery of species containing these elements at more localities than comparably rare minerals of less economic interest Hazen et al. The preceding taxonomy of mineralogical rarity differs in significant respects from that for biological species compare Figs.

An additional important difference between biological and mineralogical rarity is that biological species, once extinct, will not re-emerge naturally. Rare minerals, on the other hand, may disappear from Earth for a time, only to reappear when the necessary physical and chemical conditions arise again.

Even more fundamental a difference between biological and mineralogical species lies in what John N. Minerals do not evolve in this way, though an intriguing and as yet little explored aspect of mineralogy is how trace and minor elements and isotopes in common mineral species have varied through Earth history in response to changing near-surface conditions Hazen et al. Important similarities in the perceptions of biological and mineralogical rarity are the influences of sampling bias.

In both domains, species that are difficult to discover by virtue of their bland appearances, small sizes, or inaccessible environments category 4 may be much more common than are represented by reported occurrences Zhang et al. Like biological rarities, rare minerals often display two or more of the categories of rarity, as illustrated by the various octants in Figure 2.

For example, several rare copper vanadate minerals, including fingerite, mcbirneyite, stoiberite, and ziesite Table 1 , are known from the summit crater fumeroles of Izalco volcano, El Salvador, and at most one other locality Hughes and Hadidiacos These minerals: category 1 have extremely restricted stabilities in P-T-X space Brisi and Molinari ; category 2 they feature two elements, Cu and V, that are seldom found in combination; category 3 they may be unstable under prolonged exposure to the atmosphere; and category 4 they form in an extremely dangerous volcanic environment.

Improving prediction of rare species’ distribution from community data

Springer Professional. Back to the search result list. Table of Contents. Issue archive. Hint Swipe to navigate through the articles of this issue Close hint. Important notes. Communicated by Raphael K.

Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. Rabinowitz and S. Cairns and T. Rabinowitz , S. Cairns , T. Dillon Published Geography.

Since , papers have cited a rarity matrix organized along three axes: geographic range GR large vs. In the wider ecology literature, research on the association between plant species distributions and life history traits has mainly focused on a single axis such as GR. However, the internal structure of species ranges is widely recognized as important. In order to determine if identifying different types of rarity leads to alternative conclusions regarding the causes and consequences of rarity, we created a dataset linking the seven types of rarity matrix and to reproductive ecology traits. We found associations between the axes and these traits in a dataset of rare plant species culled from 27 papers. Significant traits included mating system and seed dispersal mechanism. Species with small GR are more likely to have ballistic or wind dispersal than biotically-mediated dispersal abiotic:biotic ratio


of rarity and their frequency in the flora of the British Isles. Conservation biology, the science of scarcity and diversity (ed. by M. E. Soule), pp.


Deborah Rabinowitz

We investigated the conservation concern of Azorean forest fragments and the entire Terceira Island surface using arthropod species vulnerability as defined by the Kattan index, which is based on species rarity. Species rarity was evaluated according to geographical distribution endemic vs. Measures of species vulnerability were combined into two indices of conservation concern for each forest fragment: 1 the Biodiversity Conservation Concern index, BCC, which reflects the average rarity score of the species present in a site, and 2 one proposed here and termed Biodiversity Conservation Weight, BCW, which reflects the sum of rarity scores of the same species assemblage. BCW was preferable to prioritise the areas with highest number of vulnerable species, whereas BCC helped the identification of areas with few, but highly threatened species due to a combination of different types of rarity.

The value of structuring rarity: the seven types and links to reproductive ecology

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Springer Professional. Back to the search result list. Table of Contents. Issue archive. Hint Swipe to navigate through the articles of this issue Close hint. Important notes.

Use of Arthropod Rarity for Area Prioritisation: Insights from the Azorean Islands

D Corresponding author. Email: jennifer. Lack of basic data to assess plant species against IUCN Red List criteria is a major impediment to assigning accurate conservation status throughout large areas of the world.

The Biology of Rarity pp Cite as. The rare hold a curious fascination. A bizarre variety of objects considered to be rare are avidly sought and collected, studied and catalogued, bought and sold.

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Henriette D.

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Minerals that conform to criterion 1, 2, or 3 are inherently rare, whereas those matching criterion 4 may be much more common than represented by reported occurrences.

Carpo M.

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CГ©cile S.

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There are many ways in which a species can become rare and this path has Seven forms of rarity are discussed with examples from the North. American flora. in particular that of the narrow endemic. los Scop. in Britain (Chapter 25).

Melissa B.

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