Systematics, phylogeny, and evolution of the Chenopodiaceae

The family Chenopodiaceae (goosefoot family) comprises over 100 genera with about 1600 species, including cultivated plants such as sugar beet and spinach. Chenopodiaceae preferentially colonize steppes and semi-deserts as well as saline sites, fields and ruderal sites, where they are often dominant. A large fraction of the species are succulent and/or capable of C4 photosynthesis.

In collaboration with other research groups, especially G. Kadereit (Mainz, Munich), the phylogeny and systematics of the Chenopodiaceae are investigated with special emphasis on the evolution of the C4 photosynthetic syndrome. Using comparative sequencing of appropriate chloroplast and nuclear DNA segments, molecular phylogenetic trees were constructed to address the following questions: (1) the position of the Chenopodiaceae within the order Caryophyllales, (2) their differentiation from the closely related Amaranthaceae (foxtail family), in which they are now often included, (3) the main lineages within the Chenopodiaceae, and (4) the relationships within selected subfamilies and tribes. In parallel, a detailed anatomical analysis of the photosynthetic organs is performed. This allows us to elucidate the evolution of multiple parallel C4 structures against the background of molecular phylogenies and thus to analyze diversification patterns that are closely linked to the development of extreme habitats. Successfully completed to date are comprehensive molecular systematics and anatomical studies at the level of the overall family Chenopodiaceae, the subfamilies Suaedoideae, Camphorosmoideae, and Salicornioideae. A detailed study of the Salsoloideae with respect to its systematic organization and the evolution of C4 characters is in progress. In addition, specific taxonomic problems have been clarified.

Image: Helmut Freitag
1) Salsola kali L. (Saltweed), the type species of the genus, North Sea coast, foredune. 2) Semi-desert with 4 different shrubby Chenopodiaceae, Isleta de Lanzarote, Canary Islands). 3) Suaeda aralocaspica (Bunge) Freitag & Schütze, leaf cross section with only one chloroplast-bearing cell layer for C4 photosynthesis. 4) Suaeda rolandii Basset & Crompton, east coast of North America, decaploid, from offspring in Kassel, with H. Freitag.

Selected publications

Mosyakin SL, Esser HJ, Freitag H (2018): The holotype of Chenopodium baryosmon (Chenopodiaceae) rediscovered: just one of many type specimens from the private herbarium of Schultes, now in the Turczaninow herbarium at KW. Phytotaxa 334(1): 49-54.

Freitag H, Lomonosova M (2017): Restoration of Suaeda sect. Helicilla (Chenopodiaceae) and typification of related taxa. Phytotaxa 323: 51-60.

Ángeles Alonso M, Crespo MB, Freitag H (2017): Salicornia cuszcoensis (Amaranthaceae/ Chenopodiaceae), a new species from Peru (South America). Phytotaxa 319: 254-262.

Schüssler Ch, Freitag H, Kotoyeva N, Schmidt D, Edwards G, Voznesenskaya E, Kadereit G (2017): Molecular phylogeny and forms of photosynthesis in tribe Salsoleae (Chenopodiaceae). Journal of Experimental Botany 68/2: 207-222.

Mosyakin SL, Freitag H, Rilke S (2017): Kali versus Salsola: the instructive story of a questionable nomenclatural resurrection. Israel Journal of Plant Sciences 64, publ. online 27.3.2017.

Brandt R, Lomonosova M, Weising K, Wagner N, Freitag H (2015): Phylogeny and biogeography of Suaeda subg. Brezia (Chenopodiaceae / Amaranthaceae) in the Americas. Plant Systematics and Evolution 301: 2351-2375.

Freitag H, Kadereit G (2013): C3 and C4 leaf anatomy types in Camphorosmeae (Camphorosmoideae, Chenopodiaceae). Plant Systematics and. Evolution: 300: 665-687.

Kadereit G, Freitag H (2011): Molecular phylogeny of Camphorosmeae (Camphorosmoideae, Che-nopodiaceae): implications for biogeography, evolution of C4 photosynthesis and taxonomy. Taxon 60: 51-78.