Heliotropiaceae are a cosmopolitan family of flowering plants with approximately 450 species worldwide, though it is concentrated especially in the tropics and subtropics.[1]
The following are the four genera in the family:
- Heliotropium (incl. Tournefortia L.)
- Euploca Nutt.
- Ixorhea Fenzl
- Myriopus Small
Ixorhea is sister to Euploca and Myriopus.[2] Together they form a clade sister to Heliotropium, which comprises four major clades: Heliotropium sect. Heliothamnus I.M.Johnst., Old World Heliotropium, Heliotropium sect. Cochranea (Miers) Post & Kuntze, and the Tournefortia-clade, the latter comprising Tournefortia sect. Tournefortia and all remaining New World species of Heliotropium.[3][4]
History
editPrior to a 2016 revision, Heliotropiaceae were considered a subfamily of the Boraginaceae: Heliotropioideae.[1] Even before that, however, there was already some indication in the field that Heliotropiaceae deserved to be recognized as an independent family. Anatomically, the presence of anatropous ovules in Heliotropiaceae as well as the presence of long suspensors and endosperm haustoria in Boraginaceae drove the earliest divide between the two families in the literature. Later, molecular data collected from a variety of families in the Boraginales collectively indicated that the Hydrophyllaceae were sister to the Heliotropiaceae, something that rendered the Boraginaceae paraphyletic.[5]
Morphology
editIn broad terms, members of the Heliotropiaceae are quite diverse in that they can be small trees, lianas, shrubs, sub-shrubs, or even perennial or annual herbs. However they all have 5-merous, tetracyclic flowers and actinomorphic corollas. These plants are also characterized by their terminal styles and
highly modified stigmatic heads (basal stigma, infertile apex) as well as by their fruits (one or two-seeded mericarpids or drupes).[5] Their conical stigmatic heads are unique and are thus a recognizable synapomorphy for this family. Heliotropiaceae mostly have distinctly scorpioid cymose inflorescences.[1]
References
edit- ^ a b c Luebert, Federico; Cecchi, Lorenzo; Frohlich, Michael W.; Gottschling, Marc; Guilliams, C. Matt; Hasenstab-Lehman, Kristen E.; Hilger, Hartmut H.; Miller, James S.; Mittelbach, Moritz; Nazaire, Mare; Nepi, Massimo (2016-06-24). "Familial classification of the Boraginales". Taxon. 65 (3): 502–522. doi:10.12705/653.5. hdl:11365/993946. ISSN 0040-0262.
- ^ Weigend, Maximilian; Luebert, Federico; Gottschling, Marc; Couvreur, Thomas L.P.; Hilger, Hartmut H.; Miller, James S. (October 2014). "From capsules to nutlets-phylogenetic relationships in the Boraginales". Cladistics. 30 (5): 508–518. doi:10.1111/cla.12061. PMID 34794245. S2CID 11954615.
- ^ Hilger, Hartmut H.; Diane, Nadja (2003-12-17). "A systematic analysis of Heliotropiaceae (Boraginales) based on trnL and ITS1 sequence data". Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie. 125 (1): 19–51. doi:10.1127/0006-8152/2003/0125-0019. ISSN 0006-8152.
- ^ Luebert, Federico; Brokamp, Grischa; Wen, Jun; Weigend, Maximilian; Hilger, Hartmut H. (June 2011). "Phylogenetic relationships and morphological diversity in Neotropical Heliotropium (Heliotropiaceae)". Taxon. 60 (3): 663–680. doi:10.1002/tax.603004.
- ^ a b Diane, N.; Forther, H.; Hilger, H. H. (2002-02-01). "A systematic analysis of Heliotropium, Tournefortia, and allied taxa of the Heliotropiaceae (Boraginales) based on ITS1 sequences and morphological data". American Journal of Botany. 89 (2): 287–295. doi:10.3732/ajb.89.2.287. ISSN 0002-9122. PMID 21669738.