Classification: Overview

Composition | Position | Division

Malvaceae Info (Home)

Composition

The Malvaceae sensu APG corresponds to the 4 traditional plant families Malvaceae, Bombacaceae, Sterculiaceae and Tiliaceae. There is no dispute that they form a natural grouping - the "core Malvales". Only the inclusion or otherwise of a few genera is questionable.

There is much less agreement on the placement of this group within the angiosperms, or on its subdivision. The traditional 4 family classification was not universally accepted, and with the addition of molecular data has become untenable. For discussion see below.

Position

The position of Malvaceae sensu APG within the higher levels of the classification of the terrestrial biota is not disputed. Members of the Malvaceae are successively

In all but the most recent classifications, the Malvaceae are classified as

In the classification of the Angiosperm Phylogeny Group (Uppsala System) dicotyledons (dicots) have been abandoned as a formal taxon, as the majority of studies find them to be paraphyletic with respect to monocots (lilies, grasses, arums, palms, orchids, gingers, etc). Instead the Malvaceae are placed in the following clades.

  1. Euangiosperms (clade Mesangiospermae), a clade containing nearly all angiosperms, including monocots, but excluding a few basal lineages.
  2. Eudicots or tricolpates, i.e. have pollen grains with 3 pores or furrows, or of a type derived from this.
  3. Rosids, a clade supported by rbcL and atpB chloroplast and 18s nuclear ribosomal DNA sequences, but without a clear morphological definition
  4. Eurosids II (also called Malvids), a clade including crucifers, maples, citrus, and less certainly, myrtles and fuchsias, as well as mallows.

The plants that compose the Malvaceae sensu APG have also been included within the order Malvales in most classifications. However the classification of Hutchinson (The Families of Flowering Plants (2nd ed.), 1959) split them into two orders - Tiliales and Malvales - the latter containing only the Malvaceae sensu strictu, and some related families being included in Tiliales.

The Cronquist System (1968, revised 1981 and 1988) has been influential, and is still used in some works. Within this the Malvaceae is placed within

In more recent classifications the sub-class Dilleniidae has been abandoned. In the Uppsala System its components are placed in the Rosids or Asterids. In other classifications dicots are divided into smaller units, classified as super-orders. (The Uppsala System doesn't use ranks for clades between the Magnoliophyta and the rank of order, but the Rosids roughly correspond to the sub-class Rosidae of other workers, and the Eurosids II to a super-order.)

In other recent classifications such as those of Thorne, Reveal and Takhtjan the Malvaceae are placed within

In the classification of Dahlgren the equivalent taxon is called Malviflorae. In the classification of Tikhomir (1986) and some earlier authors the equivalent taxon is called Columniferae or Malvalia, and is ranked as a cohort.

In all recent classifications the Malvaceae is placed with the order Malvales. The circumscription of the order however varies considerably between authors.

Within the classification of the Angiosperm Phylogeny Group, the Malvaceae is placed within a broadly circumscribed order Malvales consisting of the families Bixaceae (including Diegodendraceae), Cistaceae (sun and rock roses, etc), Cochlospermaceae, Dipterocarpaceae, Malvaceae, Muntingiaceae, Neuradaceae, Sarcolaenaceae, Sphaerosepalaceae and Thymelaeaceae (Daphne and allies). The Malvales is the sister group to the Sapindales (mostly tropical, but also including maples and horse chestnuts), and thence to the Brassicales (crucifers and allies). Kubitzki & Bayer [1] adds Tepuianthaceae (close to Thymelaeaceae) and retains Diegodendraceae as a separate family.

Within the classification of Cronquist the Malvaceae is made up of the 4 traditional families, plus the Elaeocarpacceae and Lecythidaceae. Other families considered to be closely related to Malvaceae by later workers are placed in the orders Theales and Violales.

In the Uppsala System the Elaeocarpaceae are transferred to the Oxalidales, in the Eurosid I subgroup of the Rosids, and the Lecythidaceae to the Ericales, in the Asterids.

Thorne (1992) has a broad understanding of the order Malvales, consisting of the families Bixaceae, Bombacaceae, Cistaceae, Cochlospermaceae, Diegodendraceae, Dipterocarpaceae, Gonystylaceae, Huaceae, Malvaceae, Monotaceae, Plagiopteraceae, Sarcolaenaceae, Sphaerosepalaceae, Sterculiaceae, Thymelaeaceae and Tiliaceae. In other classifications the Gonystylaceae are included within Thymelaeaceae, and Monotaceae in Dipterocarpaceae.

The classification of Takhtajan (1997) is similar, but separates off Bixaceae, Cistaceae and Cochlospermaceae as the order Cistales in the sub-class Malvanae, places Gonystylaceae and Thymelaeaceae in an order Thymelaeales in his sub-class Euphorbianae, and adds Dirachmaceae.

A later classification from Thorne (2000) divides the core Malvales into 3 families - an expanded Malvaceae (including Malvaceae sensu strictu), Bombacaceae, and parts of Tiliaceae and Sterculiaceae, a reduced Tiliaceae, and Byttneriaceae - which may be based on the rbcL/atpB phylogeny of Bayer et al (abstract). Subsequently he has revised his classification, reducing Tiliaceae to Malvaceae, and separating Grewiaceae from Byttneriaceae.

In the Dahlgren System the Malvales consists of the families Bixaceae, Bombacaceae, Cistaceae, Cochlospermaceae, Dipterocarpaceae, Huaceae, Malvaceae, Plagiopteraceae, Sterculiaceae, Sphaerosepalaceae, Sarcolaenaceae and Tiliaceae.

In the classification of Goldberg (1986) a narrowly drawn Malvales consists of Bombacaceae, Elaeocarpaceae, Malvaceae, Sterculiaceae and Tiliaceae.

Reveal (1997) splits the super-order Malvanae into 4 orders, Bixales, Cistales, Malvales and Thymelaeales, Malvales consisting of the Bombacaceae, Byttneriaceae, Dirachmaceae, Malvaceae, Sterculiaceae and Tiliaceae, i.e. corresponding to Malvaceae sensu APG plus Dirachmaceae. He assigns the Huaceae and Plagiopteraceae to Violales.

A wider variety of angiosperm classification systems, including some earlier ones, is summarised at Systems of flowering plants by different authors. Lindley's Vegetable Kingdom (1846) summarises a variety of 18th and early 19th century classifications: a fascimile is available online at Gallica.

Recent work raises the possibility two groups of parasitic plants (Cytinaceae and Apodanthaceae, previously placed, faute de mieux, in Rafflesiales) fall into Malvales. These are ancient parasitic lineages (possibly representing a single clade) whose relationships are obscured by the loss of vegetative traits, the accelerated molecular evolution typical of parasitic plants, and horizontal gene transfer. It is possible that these groups fall into Malvaceae.

Division

The Malvaceae sensu APG have been traditionally divided into 4 families - Malvaceae, Bombacaceae, Sterculiaceae and Tiliaceae - and thence into a large and disputed number of tribes. This has not been universally followed. One variation is to divide the Sterculiaceae into 2 families, the other half being the Byttneriaceae. Another is to subsume Bombacaceae within Malvaceae. There are a number of family synonyms, including (in addition to Bombacaceae, Sterculiaceae and Tiliiaceae) Hibiscaceae, Fugosiaceae, Philippodendraceae, Plagianthaceae, Cacaoaceae, Chiranthodendraceae, Dombeyaceae, Fremontiaceae, Helicteraceae, Berryaceae, Hermanniaceae, Lasiopetalaceae, Melochiaceae, Pentapetaceae, Grewiaceae, Sparmanniaceae, Theobromataceae. Triplobaceae and Triplochitonaceae, most of which names applied to segregated parts of one of the preceeding 4 families.

The traditional 4 family classification has been shown by molecular evidence (summary molecular cladogram) to be untenable. Apart from several genera being misplaced

  1. The putatively sterculiaceaeous tribe Fremontodendreae nests with Malvaceae and Bombacaceae, rather than with the remainder of Sterculiaceae.
  2. Bombacaceae is paraphyletric with respect to Malvaceae sensu strictu; there is an unresolved fivefold polytomy consisting of Malvaceae sensu strictu together with the putatively bombacaceous tribe Matisieae and the genera Pentaplaris and Uladendron, Fremontodendreae, the putatively bombacaceous tribes Adansonieae and Ochromeae, and the bombacaceous genus Septotheca.
  3. Sterculiaceae is polyphyletic, reflecting the proposed division into Sterculiaceae and Byttneriaceae, but with the tribe Dombeyae associated with the remnant "Sterculiaceae".
  4. Sterculiaceae may be paraphyletic with respect to Bombacaceae.
  5. The putatively bombacaceous tribe Durioneae (durians and allies) is nested within Sterculiaceae as the sister to Helictereae.
  6. The putatively tilieaceaeous tribes Brownlowieae and Tilieae (limes) are nested with "Sterculiacae", rather than within the remainder of traditional Tilieaceae. The Tilieae appear to be the sister group to the Dombeyeae.
  7. The tribes Grewieae and Sparrmannieae (from Tiliaceae) and Hermannieae, Lasiopetaleae, Theobromeae and Byttnerieae (from Sterculiaceae) are nested together to the exclusion of the remainder of Tiliaceae and Sterculiaceae.

The ndhF cladogram of Alverson et al [3] shows 9 groups, labelled as subfamilies Malvoideae, Bombacoideae, Sterculioideae, Dombeyoideae, Tilioideae, Brownlowioideae, Durionoideae, Grewioideae and Byttneroideae. The position of the bombacaceous genera Ochroma (balsa) and Patinoa is unclear. Several elements of the Malvaceae sensu APG are not represented within this data set and might not fall with any of these clades.

These 9 clades are adopted as a working classification in Malvaceae Info. The assignment of genera for which ndhF or other sequence data is either not available, or does not provide a clear assignment, follows that of Kubitski and Bayer [1], with the following exceptions

I have examined internally transcribed spacer (ITS) DNA sequences published in GenBank and EBI. This data set doesn't have sufficient coverage to confirm all the above points, but the status of Durioneae as the sister group to Helictereae is confirmed. It also indicates that Fremontodendreae is more closely related to the core malvoids than to the core bombacoids. Unpublished sequences provided by David Baum point to the association of Matisieae with the malvoids.

Additional work using the matK chloroplast gene by Baum et al [3] confirms the placement of Matisieae, Camptostemon, Lagunaria, Pentaplaris and Uladendron in Malvoideae. This study does not resolve the position of Fremontodendreae, or the position of Ochromeae and Septatheca.

There are several alternatives for a new classification of the "core Malvales".

1. The alternative adopted by the Angiosperm Phylogeny Group and other workers - to include the whole of the "core Malvales" in a single family.

2. Each of the 9 or more holophyletic clades can be made a separate family. There is the possibility of combining pairs of these clades (Tilioideae+Dombeyoideae, Grewioideae+Byttneroideae, Bombacoideae+Malvoideae), but the holophyly of the former first pair is less well supported, and the last pair is a large, diverse and unwieldy grouping. As mentioned above there may be other clades that may need to treated as separate families under this approach.

3. A two family classification consisting of the clades /Malvadendrina (first 7 subfamilies)and /Byttneriina (last 2 subfamilies) . The correct name for the former clade would be Malvaceae. I am uncertain which of the alternatives (Byttneriaceae, Sparmanniaceae, Grewiaceae) would be correct for the latter.

4. If paraphyletic groupings are accepted a 5 family classification similar to the traditional classification (with Byttneriaceae) is possible, with the transfer of some species and genera. Tilia is no longer within the family to which it gives its name, and therefore this family would have to be renamed, as Grewiaceae.

The contents of the subfamilies are as follows:

Malvoideae

The Malvoideae is defined cladistically as a stem group composed of those species closer to Malva sylvestris (Common Mallow, High Mallow) than to Bombax ceiba (Kapok).

It is composed of the several tribes that make up the Malvaceae sensu strictu, plus Matisiae and Fremontodendreae, and possibly also Ochromeae, Fremontodendreae and Septotheca. The division of the Malvaceae sensu strictu into tribes has been historically unstable, and there are sufficient hints to give rise to an expectation of further revisions on the basis of molecular evidence. The current division is into Malveae (mallows, abutilons, sidas and allies), Gossypieae (cottons and allies) and, Hibisceae (hibiscuses and allies, Pavonia and allies, Kydia and allies). The Matisieae are a group, formerly classified in Bombacaceae, with a Neotropical distribution. The Fremontodendreae are two genera from Guatemala, Mexico and California, which were formerly classified in Bombacaceae or Sterculiaceae. The genera Pentaplaris, UIadendron, Camptostemon, Lagunaria, Howittia, Alyogyne and Jumelleanthus fall into Malvoideae but are currently not assigned to any tribe.

Bombacoideae

The Bombacoideae is the remnant of the Bombacaceae, after the removal of the tribes Matisieae (to Malvoideae) and Durioneae (to Helicteroideae). This remnant is more or less coterminous with the tribe Adansonieae, including Adansonia (baobabs), Bombax (kapok), Chorisia (silk cotton), etc. The placement of the genera Ochroma and Patinoa (Ochromeae) and Septotheca remains uncertain.

Sterculioideae

The Sterculioideae contains the one tribe Sterculieae (Sterculia, Cola and allies).

Dombeyoideae

The Dombeyoideae contains the one tribe Dombeyeae.

Tilioideae

The Tilioideae is reduced to the tribe Tilieae, consisting of the genera Tilia, Craigia and Mortoniodendron, which is more closely related to members of the former Sterculiaceae than to the remainder of the former Tiliaceae.

Brownlowioideae

The Brownlowioideae contains elements of the former Tiliaceae, consisting of the tribes Berryeae and Brownlowieae.

Helicterioideae

The Helicterioideae consists of the Helictereae, formerly classified in the Sterculiaceae, and the Durioneae (durians and allies), formerly classified in the Bombacaceae.

Grewioideae

The Grewioideae consists of much of the former Tiliaceae, divided into the tribes Grewieae and Sparrmannieae. The latter tribe includes Corchorus (jute) and the formerly problematic New Caledonian endemic Oceanopapaver. It is possible that additional tribes should be introduced; in particular the genus Mollia is divergent from the remainder of Grewioideae.

Byttnerioideae

The Byttnerioideae contains the tribes Byttnerieae, Hermannieae, Lasiopetaleae and Theobromeae (cacao and allies). It is possible that Byttnerieae should be subdivided, in which case the tribe Kleinhovieae, at least, would be introduced.

Notes

  1. The clade name Plantae, and the vernacular term plant, can correspond to any of Archaeplastida, Viridiplantae and Embryophyta.

References

  1. Kubitzki, K. & Bayer, C., The Families and Genera of Vascular Plants Vol. 5: Malvales, Capparales and Non-betalain Caryophyllales (2003)
  2. Baum et al, Phylogenetic Relationships of Malvatheca (Bombacoideae and Malvoideae; Malvaceae sensu lato) as Inferred From Plastid DNA Sequences, American Journal of Botany 91(11): 1863–1871 (2004)
  3. Alverson et al, Phylogeny of the Core Malvales: Evidence from ndhF Sequence Data, American Journal of Botany 86(10): 1474–1486 (1999)
  4. Tate, Jennifer A., Andeimalva, a new genus of Malvaceae from Andean South America
  5. B. E. Pfeil and M. D. Crisp, What to do with Hibiscus? A proposed nomenclatural resolution for a large and well known genus of Malvaceae and comments on paraphyly, Australian Systematic Botany 18: 49-60 (2005)
  6. Whitlock, Karol & Alverson, Chloroplast DNA sequences confirm the placement of Oceanopapaver within the Grewioideae (Tiliaceae or Malvaceae s.l.) (abstract)
  7. Phuphathanaphong, L. S. Puangpen,and G. Nuvongsri, Thepparatia (Malvaceae), a new genus from Thailand, Thai For. Bull. (Bot.) 34: 195-200 (2006)

Feedback

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© 2002, 2003, 2004, 2005, 2006 Stewart Robert Hinsley