HOME

TheInfoList



OR:

Haloragaceae (the watermilfoil
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
) is a eudicot
flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...
family in the order
Saxifragales Saxifragales is an order (biology), order of flowering plants in the Superrosids, superrosid clade of the eudicots. It contains 15 Families (biology), families and around 100 genera, with nearly 2,500 species. Well-known and economically import ...
, based on the
phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
APG system. In the Cronquist system, it was included in the order Haloragales.


Description

The Haloragaceae (alternate spelling Halorrhagidaceae) are very diverse in habit, including both small trees and submerged aquatics. Most members of the Haloragaceae are herbaceous, and most of those in turn are
perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...
s, though some species are annuals. In contrast however, members of the genus ''Haloragodendron'' are woody. Most species of ''Myriophyllum'' are monoecious while most other taxa have hermaphrodite flowers. The flowers are usually small and inconspicuous, but some genera can have more "showy" conspicuous flowers (''Haloragodendron'', ''Glischrocaryon''). Flowers are usually radially symmetrical, and unusual for core eudicots, merosity is (2-3)-4 parted. Petals are usually keeled or hooded when present. In ''Myriophyllum'', female flowers usually lack a perianth. They have (2-)4-8 stamens and an inferior ovary of (2-)4 carpels. In ''Myriophyllum'', the fruit is a schizocarp of 1-seeded 'nutlets'. Other genera can have nuts or drupes that can be winged or inflated. The genus '' Gunnera'', formerly included here, are now in the separate family Gunneraceae.


Taxonomy


Phylogeny

Molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
studies, in particular, the APG system, placed the Haloragaceae within the core eudicot order,
Saxifragales Saxifragales is an order (biology), order of flowering plants in the Superrosids, superrosid clade of the eudicots. It contains 15 Families (biology), families and around 100 genera, with nearly 2,500 species. Well-known and economically import ...
. Earlier versions of the APG had allowed either the broader circumscription (Haloragaceae '' s.l.'') or a narrower Haloragaceae ''s.s.''.


Subdivision


History

Historically, the Haloragaceae included many disparate genera, since segregated. A major circumscription was carried out by Schindler in 1905, dividing the "Halorrhagaceae" into two subfamilies (Halorrhagoideae and Gunneroideae) and the former into two tribes (Halorrhageae and Myriophylleae), with a total of seven genera. He removed some of the disparate genera and merged ''Gonocarpus'' and ''Meionectes'' into ''Haloragis''. This classification long remained the standard till Shaw (1966) removed '' Gunnera'' (into its own family Gunneraceae, within the order Gunnerales), the sole genus in Gunneroideae, leaving six genera. This situation remained until the monograph of Orchard (1975). Orchard restored ''Gonocarpus'' and split ''Haloragodendron'' from ''Haloragis'', leaving 8 genera.
List of genera, habitat, ''distribution'' (Number of species) * Terrestrial ** '' Glischrocaryon'' Endl. ''Australia'' (4) ** '' Gonocarpus'' Thunb. ''Australia, New Zealand, S. E. Asia'' (36) ** '' Haloragis'' J.R.Forst. & G.Forst. ''Australia, New Zealand, S. Pacific'' (26) ** ''Haloragodendron'' Orchard ''Australia'' (5) * Semiaquatic ** '' Laurembergia'' P.J.Bergius ''Pantropical'' (4) * Aquatic ** '' Meziella'' Schindl. ''S. W. Australia'' (1) ** '' Myriophyllum'' L. ''Cosmopolitan'' (60) ** '' Proserpinaca'' L. ''New World'' (3)


Molecular era

A molecular study resolved the infrafamilial relationships among the genera, resulting in some taxonomic revision, including redistribution of species. In addition, ''Meionectes'' was reinstated, separating two species from ''Haloragis'' and creating a new monotypic genus, ''Trihaloragis'' by segregating ''Gonocarpus hexandrus''. Consequently, the number of genera is increased to ten, with the addition of: * ''Meionectes'' R.Br. (2) * ''Trihaloragis'' Moody & Les (1) ''Glischrocaryon''-''Haloragodendron'' is resolved as the basal node,
sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...
to the remaining family. While monophyly of this group is well supported, monophyly of the two separate genera is less well supported, and suggests some
paraphyly Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
. Thus the generic limits remain unresolved. A subsequent, more detailed study of ''Myriophyllum'' demonstrated that the
monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...
genus ''Meziella'' was embedded within it, leading to its submersion within the former as ''Myriophyllum'' subgenus ''Meziella'', thereby reducing the number of genera within the family to 9.


Species

As of 2014, the family has 138 species, distributed among the nine genera as follows: * ''Glischrocaryon'' (4) * ''Gonocarpus'' (36) * ''Haloragis'' (24) * ''Haloragodendron'' (6) * ''Laurembergia'' (4) * ''Myriophyllum'' (60) * ''Proserpinaca'' (2) * ''Meionectes'' (2) * ''Trihaloragis'' (1)


Distribution and habitat

The distribution of the family is nearly worldwide. The center of species diversity is in
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
where all genera are found excepting ''Proserpinaca'' and ''Laurembergia''. Habitats vary from arid desert regions to freshwater lakes. The terrestrial genera (''Glischrocaryon'', ''Gonocarpus'', ''Haloragis'', ''Haloragodendron'', ''Trihaloragis'') are primarily limited to the southern hemisphere. ''Meionectes'', ''Meziella'', ''Myriophyllum'' and ''Proserpinaca'' are aquatic, while ''Laurembergia'' are semiaquatic. ''Glischrocaryon'', ''Haloragodendron'', ''Meionectes'' and ''Trihaloragis'' are Australian
endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
s, where about 70% of all species are found. For detailed maps of the distribution of each genus, see ''Figure 1''.


References


Bibliography


Books and theses

* * * ** , in * * * * *


Articles

* * * * *
Supplement
* * * * *


Websites

* * * * * * (''see also'' Angiosperm Phylogeny Website) * , in Flora of China online vol. 13


External links

* * {{Authority control Saxifragales families