Strasburgeriaceae is a small family of

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 ...

s in the order

Crossosomatales The Crossosomatales are an order, first recognized as such by APG II. They are flowering plants included within the Rosid eudicots. Description Species assigned to the Crossosomatales have in common flowers that are positioned solitarily, wi ...

, only found in

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

and

New Caledonia New Caledonia ( ; ) is a group of islands in the southwest Pacific Ocean, southwest of Vanuatu and east of Australia. Located from Metropolitan France, it forms a Overseas France#Sui generis collectivity, ''sui generis'' collectivity of t ...

. It contains two

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

, '' Strasburgeria'' and ''

Ixerba ''Ixerba brexioides'', the sole species in the genus ''Ixerba'', is a bushy tree with thick, narrow, serrated, dark green leaves and panicles of white flowers with a green heart. The fruit is a green capsule that splits open to reveal the black ...

''. Both genera have simple, evergreen, alternated leaves, often in worl-like clusters, with gland-tipped serrations,

hermaphroditic A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

, pentamerous flowers with persistent sepals, clawed petals, flat and long filaments that extend beyond the petals and a persistent style with a punctiform stigma. Fossil pollen named ''Bluffopollis scabratus'', found in deposits from the

Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...

to the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

, is almost identical to the pollen of ''Strasburgeria'', although only half its size. The fact that it was found in western and southern Australia and in New Zealand suggests that the

most recent common ancestor A most recent common ancestor (MRCA), also known as a last common ancestor (LCA), is the most recent individual from which all organisms of a set are inferred to have descended. The most recent common ancestor of a higher taxon is generally assu ...

of ''Strasburgeria'' and ''Ixerba'' had developed by the time of the break-up of East-

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

. Recent phylogenetic analysis resulted in the inclusion of the genus ''Ixerba'' (previously assigned to the monotypic family Ixerbaceae) in the Strasburgeriaceae. The following tree represents the most recent insights in the relationship between the Strasburgeriaceae and other families. While both ''Ixerba brexioides and'' ''Strasburgeria robusta'' share a base chromosome number of ''x'' = 25, ''I. brexioides'' is

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...

(2''n'' = 2''x'' = 50), while ''S. robusta'' is icosaploid (2''n'' = 20''x'' = 500). The massive

polyploid Polyploidy is a condition in which the biological cell, cells of an organism have more than two paired sets of (Homologous chromosome, homologous) chromosomes. Most species whose cells have Cell nucleus, nuclei (eukaryotes) are diploid, meaning ...

y in ''S. robusta'' may have furthered the adaptations that let it survive on the

ultramafic Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are usua ...

substrates found in the

montane forest Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures lapse rate, fall as elevation increases, causing the ecosystem to stratify. This stratification is ...

of New Caledonia.

Species

* '' Ixerba brexioides'' * ''

Strasburgeria robusta ''Strasburgeria robusta'' is an evergreen tree with large toothed leaves and large but rather inconspicuous, single, pendulant flowers in a gloomy colorscheme of yellowish with brown markings, with about ten sepals, five petals, ten stamens, a ve ...

References

External sources

Strasburgeriaceae L. Watson and M.J. Dallwitz (1992 onwards). The families of flowering plants

* ttp://www.gns.cri.nz/what/earthhist/fossils/spore_pollen/catalog/taxa/570.htm Photos of the pollen fossil ''Bluffopollis scabratus'' {{Taxonbar, from=Q132084 Crossosomatales Rosid families