Saxifragaceae

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Saxifragaceae
Tiarella
(Foamflower)
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Order: Saxifragales
Family: Saxifragaceae
Juss.
Type genus
Saxifraga
Clades

See text

The range of Saxifragaceae
Flowers of Saxifraga granulata
Saxifraga granulata
Astilbe rivularis
Astilbe rivularis

Saxifragaceae is a family of

genera. About half of these consist of a single species, but about 400 of the species are in the type genus Saxifraga
. The family is predominantly distributed in the northern hemisphere, but also in the Andes in South America.

Description

Species are

perennials (rarely annual or biennial), sometimes succulent or xerophytic, often with perennating rhizomes. The leaves are usually basally aggregated in alternate rosettes, sometimes on inflorescence stems. They are usually simple, rarely pinnately or palmately compound. Their margins may be entire, deeply lobed, cleft, crenate or dentate and petiolate with stipules.[1][2]

The inflorescences are bracteate racemes or cymes. The flowers are hermaphroditic (bisexual), rarely unisexual (androdioecious), actinomorphic (rarely zygomorphic). The perianth is placed on a hypanthium that may be free or may be partly fused with the ovary (which is then semi-inferior). There are usually five sepals, but there may be three to ten, fused with the hypanthium, occasionally petaloid. The petals are clawed, sometimes cleft at the tip or finely dissected. Flowers have five to ten stamens, free and opposite the petals, with the anthers usually basifixed and opening by lengthwise slits. The ovary is inferior to semi-inferior with two (sometimes three) carpels usually fused at the base, sometimes free, each topped with stylodium and capitate stigma. The ovules are few to many, with axile or parietal placentation and two to three styles. The fruit is usually a septicidal capsule or follicle, with numerous small seeds.[1][2]

Taxonomy

Saxifragaceae has long been considered in a pivotal position in the evolution of angiosperm lineage, located in an ancestral "Saxifragalean stock". Historically the Saxifragaceae have included many very

sensu lato (s.l.). Within those subfamilies, the large majority of genera (30) were located within subfamily Saxifragoideae, the core group, with all but two of the remainder only having 1-3 genera.[4][5]

The circumscription of the family has changed considerably in recent years, in large part due to

polyphyletic, and probably represents the most extreme example, with at least 10 evolutionary lines. Consequently the circumscription has been considerably reduced, with many of the subfamilies being either elevated to separate families, or placed as components of other families, often quite distant. For instance subfamily Parnassioideae was raised to the level of family Parnassiaceae, and eventually a subfamily of Celastraceae (order Celastrales). Similarly the Hydrangoideae is now the family Hydrangeaceae (order Cornales).[4][6]

The reduced Saxifragaceae is distinguished by being referred to as Saxifragaceae sensu stricto (s.s.), corresponding to the Saxifragoideae a natural monophyletic group.

asterid clades.[8][4][6]

Cladogram I: Saxifragales families[9][10][6]
Saxifragales

Peridiscaceae (4)

 97 

Paeonia (Paeoniaceae)

 woody clade 

Liquidambar (Altingiaceae)

 69 
 98 

Hamamelidaceae (27)

 95 

Cercidiphyllum (Cercidiphyllaceae)

Daphniphyllum (Daphniphyllaceae)

 core Saxifragales 

Crassulaceae (34)

 Haloragaceae s.l.

Aphanopetalum (Aphanopetalaceae)

Tetracarpaea (Tetracarpaeaceae)

Penthorum (Penthoraceae)

Haloragaceae s.s. (8)

 Saxifragaceae alliance 

Iteaceae (including Pterostemonaceae) (2)

Ribes (Grossulariaceae)

Saxifragaceae s.s. (33)

100%
maximum likelihood bootstrap support except where labeled with bootstrap percentage
Monogeneric families are represented by genus names, otherwise the number of genera is in (parentheses)
Cynomorium
(Cynomoriaceae) remains unplaced within this tree

Subdivision

Flower stalk of Heuchera americana
Heuchera americana
Flowers of Rodgersia podophylla
Rodgersia podophylla
Flowers of Micranthes merkii
Micranthes merkii

Numerous attempts have been made to subdivide Saxifragoideae (Saxifragaceae s.s.). These have included dividing the family by the placentation of the ovules, as either parietal (e.g. Heuchera) or axile (e.g. Saxifraga). None of these has been supported by molecular data.[1][7]

clades, with two main lineages, saxifragoids and heucheroids and further subdivision of heucheroids into nine subclades or groups:[7][8][1]

Clades (Genera (Species))

The clades and subclades are related as shown in the cladogram:[8]

Cladogram II: Infrafamilial structure of Saxifragaceae
Saxifragaceae
Saxifragoids

Saxifraga

30
Heucheroids

Leptarrhena

8

Saniculiphyllum

Boykinia

11
16
18

Astilbe

14
20

Heuchera

7

Cascadia

19

Darmera

10

Peltoboykinia

23

Micranthes

15
27
29
31
38
Diversification time in Mya underneath group names

Genera

Main article: List of Saxifragaceae genera

Saxifragaceae s.s. has about 33–35 genera and about 640 species. About half of the genera (18 of 33) are

monotypic, but Saxifraga has about 400 species, and has generally been divided into sections.[7][11][2][8]

Evolution and biogeography

The

Bering Land Bridge facilitating plant migration. [8]

Etymology

The family and type genus name are derived from the two Latin words saxum (rock), and frango (to break), but the exact origin is unknown, although surmised to refer to either growing in crevices in rocks or medicinal use for

kidney stones.[2]

Distribution and habitat

Primarily Northern hemisphere temperate and arctic regions, and also tropical montane, including the Americas, Europe, North Africa (including montane Ethiopia) and temperate and subtropical Asia to

disjunct distributions between E Asia and N America, while other taxa have separate narrow distributions in southern S America. Some species are found in wet woodlands, swamplike conditions and wet cliff edges.[2][8][1]

References

  1. ^ a b c d e Byng 2014.
  2. ^ a b c d e Christenhusz et al 2017.
  3. ^ a b Schulze-Menz 1964.
  4. ^ a b c Morgan & Soltis 1993.
  5. ^ Soltis & Soltis 1997.
  6. ^ a b c APG IV 2016.
  7. ^ a b c d Soltis et al 1993.
  8. ^ a b c d e f Deng et al 2015.
  9. ^ Jian et al 2008.
  10. ^ Stevens 2019.
  11. ^ Christenhusz & Byng 2016.

Bibliography

Books

  • ISBN 978-0-9929993-1-5
    .
  • ISBN 978-0-226-52292-0
    .
  • ISBN 978-3-540-32219-1
    .
  • Schulze-Menz, G K (1964). "Saxifragaceae". In
    Gebrüder Borntraeger Verlag. pp. 201–206. (see also Syllabus der Pflanzenfamilien
    )

Articles

Websites

External links

Wikispecies has information related to Saxifragaceae .
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