Myrtales Explained

The Myrtales are an order of flowering plants (angiosperms) placed as a sister to the eurosids II clade as of the publishing of the Eucalyptus grandis genome in June 2014.^[1]

The APG III system of classification for angiosperms still places it within the eurosids; this is corroborated by the placement of the Myrtales in the Malvid clade by the One Thousand Plant Transcriptomes Initiative.^[2] The following families are included as of APGIII:

• Alzateaceae S. A. Graham
• Combretaceae R. Br. (leadwood family)
• Crypteroniaceae A. DC.
• Lythraceae J. St.-Hil. (loosestrife and pomegranate family)
• Melastomataceae Juss. (including Memecylaceae DC.)
• Myrtaceae Juss. (myrtle family; including Heteropyxidaceae Engl. & Gilg, Psiloxylaceae Croizat)
• Onagraceae Juss. (evening primrose and Fuchsia family)
• Penaeaceae Sweet ex Guill. (including Oliniaceae Arn., Rhynchocalycaceae L. A. S. Johnson & B. G. Briggs)
• Vochysiaceae A. St.-Hil.

The Cronquist system gives essentially the same composition, except the Vochysiaceae are removed to the order Polygalales, and the Thymelaeaceae are included. The families Sonneratiaceae, Trapaceae, and Punicaceae are removed from the Lythraceae. In the classification system of Dahlgren the Myrtales were in the superorder Myrtiflorae (also called Myrtanae). The APGIII system agrees with the older Cronquist circumscriptions of treating Psiloxylaceae and Heteropyxidaceae within Myrtaceae, and Memecyclaceae within Melastomataceae.

Ellagitannins are reported in dicotyledoneous angiosperms, and notably in species in the order Myrtales.^[3]

Origins

Myrtales is dated to around 89–99 million years ago (mya) in Australasia; however, there is some contention as to that date, which was obtained using nuclear DNA. When looking at chloroplast DNA, the myrtales' ancestor is, instead, considered to have evolved during the mid-Cretaceous period (100mya) in Southeast Africa, rather than in Australasia.^[4] Although the APG system classifies myrtales as within the eurosids, the recently published genome of Eucalyptus grandis places the order myrtales as a sister to the eurosids rather than inside them. The discrepancy is thought to have arisen due to the difference between using numerous taxa versus using various genes for constructing a phylogeny.^[1]

Further reading

• Conti E, Eriksson T, Schönenberger J, Sytsma KJ, Baum DA . Early Tertiary out-of-India dispersal of Crypteroniaceae: evidence from phylogeny and molecular dating . Evolution; International Journal of Organic Evolution . 56 . 10 . 1931–42 . October 2002 . 12449480 . 10.1111/j.0014-3820.2002.tb00119.x . free .
• Schönenberger J, Conti E . Molecular phylogeny and floral evolution of Penaeaceae, Oliniaceae, Rhynchocalycaceae, and Alzateaceae (Myrtales) . American Journal of Botany . 90 . 2 . 293–309 . February 2003 . 21659121 . 10.3732/ajb.90.2.293 .

Notes and References

1. Myburg AA, Grattapaglia D, Tuskan GA, Hellsten U, Hayes RD, Grimwood J, Jenkins J, Lindquist E, Tice H, Bauer D, Goodstein DM, Dubchak I, Poliakov A, Mizrachi E, Kullan AR, Hussey SG, Pinard D, van der Merwe K, Singh P, van Jaarsveld I, Silva-Junior OB, Togawa RC, Pappas MR, Faria DA, Sansaloni CP, Petroli CD, Yang X, Ranjan P, Tschaplinski TJ, Ye CY, Li T, Sterck L, Vanneste K, Murat F, Soler M, Clemente HS, Saidi N, Cassan-Wang H, Dunand C, Hefer CA, Bornberg-Bauer E, Kersting AR, Vining K, Amarasinghe V, Ranik M, Naithani S, Elser J, Boyd AE, Liston A, Spatafora JW, Dharmwardhana P, Raja R, Sullivan C, Romanel E, Alves-Ferreira M, Külheim C, Foley W, Carocha V, Paiva J, Kudrna D, Brommonschenkel SH, Pasquali G, Byrne M, Rigault P, Tibbits J, Spokevicius A, Jones RC, Steane DA, Vaillancourt RE, Potts BM, Joubert F, Barry K, Pappas GJ, Strauss SH, Jaiswal P, Grima-Pettenati J, Salse J, Van de Peer Y, Rokhsar DS, Schmutz J . 6 . The genome of Eucalyptus grandis . Nature . 510 . 7505 . 356–62 . June 2014 . 24919147 . 10.1038/nature13308 . 2014Natur.510..356M . 4392576 . free .
2. Leebens-Mack JH, Barker MS, Carpenter EJ, Deyholos MK, Gitzendanner MA, Graham SW, etal . One Thousand Plant Transcriptomes Initiative . One thousand plant transcriptomes and the phylogenomics of green plants . Nature . 574 . 7780 . 679–685 . October 2019 . 31645766 . 6872490 . 10.1038/s41586-019-1693-2.
3. Yoshida T, Amakura Y, Yoshimura M . Structural features and biological properties of ellagitannins in some plant families of the order Myrtales . International Journal of Molecular Sciences . 11 . 1 . 79–106 . January 2010 . 20162003 . 2820991 . 10.3390/ijms11010079 . free .
4. Grattapaglia D, Vaillancourt RE, Shepherd M, Thumma BR, Foley W, Külheim C, Potts BM, Myburg AA . Progress in Myrtaceae genetics and genomics: Eucalyptus as the pivotal genus. . Tree Genetics & Genomes . June 2012 . 8 . 3 . 463–508 . 10.1007/s11295-012-0491-x . free . 2263/58495 . free .