''Argyroderma'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

consisting of a dozen species of

succulent In botany, succulent plants, also known as succulents, are plants with parts that are thickened, fleshy, and engorged, usually to retain water in arid climates or soil conditions. The word ''succulent'' comes from the Latin word ''sucus'', meani ...

s in the iceplant family from

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

Description

These distinctive plants are among those known as "living stones", because their highly succulent, usually stemless, blue-green leaves occur at ground level and can resemble small stones. They form small clumps of a few or many paired, usually cylindrical to egg-shaped leaves that are cleft in the center. Each stem bears just 2 leaves per season but may produce offsets over the years. In some species the old leaves persist and form a short column on which new leaves develop. Solitary daisy-like flowers, usually white, yellow, or purple, appear in the cleft.

Distribution

The entire genus is naturally confined to a relatively small region in the far west of

, known locally as the "

Knersvlakte The Knersvlakte is a region of hilly terrain covered with quartz gravel in Namaqualand in the north-west corner of the Western Cape Province of South Africa. The name, literally "gnashing plain" in Afrikaans,quartzite Quartzite is a hard, non- foliated metamorphic rock that was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tecton ...

sands.

Cultivation

Like most succulents, they require extremely well-drained soil, and are damaged by repeated frosts. Their preferred mode of cultivation is a bright and sunny position with gritty free-draining soil. They may be propagated from seed, or careful division of established clumps.

Diversification and evolution

The

Cape Floristic Region The Cape Floral Region is a floristic region located near the southern tip of South Africa. It is the only floristic region of the Cape Floristic Kingdom, and includes only one floristic province, known as the Cape Floristic Province. The Cap ...

in South Africa is home to a diverse range of plant life, believed to have evolved through widespread

evolutionary radiation An evolutionary radiation is an increase in taxonomic diversity that is caused by elevated rates of speciation, that may or may not be associated with an increase in morphological disparity. A significantly large and diverse radiation within ...

. Within the family

Aizoaceae The Aizoaceae (), or fig-marigold family, is a large family of dicotyledonous flowering plants containing 135 genera and about 1,800 species. Several genera are commonly known as 'ice plants' or 'carpet weeds'. The Aizoaceae are also referred to a ...

, the genus ''Argyroderma'' shows evidence of diversification due to spatially isolated populations experiencing

phenotypic In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...

divergence from different

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

conditions, leading to genetic differentiation and varying flowering times. This pattern suggests

adaptive radiation In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic int ...

in separate populations played a key role in the evolution of the ice-plant family in the diverse landscapes of the southern African winter rainfall deserts.

Species

, the

Catalogue of Life The Catalogue of Life (CoL) is an online database that provides an index of known species of animals, plants, fungi, and microorganisms. It was created in 2001 as a partnership between the global Species 2000 and the American Integrated Taxono ...

includes 12 species of ''Argyroderma'':

References

{{Taxonbar, from=Q137914 Aizoaceae Aizoaceae genera Taxa named by N. E. Brown