Neotropical Boraginaceae

Description

Herbs, subshrubs, shrubs, trees, rarely lianas; rarely obligate root parasites with chlorophyll absent in Lennoa Lex. Hairs usually present, occasionally containing cystoliths, simple or glandular. Leaves usually alternate, rarely subopposite (Tournefortia L.), sometimes basal (Plagiobothrys Fisch. & C.A.Mey.), simple, rarely compound (Phacelia Juss.), reduced to scales in Lennoa, exstipulate; lamina entire, usually rough to hispid, margins mostly entire, or crenate, or serrate, or dentate with venation pinnate; domatia occurring in Cordia L. and Ehretia P.Browne. Inflorescence terminal, axillary, or intermodal, cymose, the branches often scorpioid, helicoid, or reduced and capitate to glomerate (as Varronia P.Browne), rarely reduced to one solitary flower (some Heliotropium L.). Flowers actinomorphic, sometimes distylous (Varronia and Cordia), usually 5-merous, hermaphrodite or unisexual; calyx usually 5-lobed, distinct or connate. Corolla sympetalous, usually 5-lobed; stamens isomerous, alternate with corolla lobes; filaments adnate to corolla tube; anthers 2-locular, dehiscing longitudinally; ovary superior, 2-carpellate, but usually becoming falsely 4-locular, with axile placentation or often parietal with 2 placentae in Phacelia; ovules usually 4, anatropous to hemitropous; the style terminal or gynobasic, simple, or bifid (Ehretioideae, Phacelia), or twice 2-cleft (Cordia and Varronia); stigmas 1-4; nectar disk usually present around base of ovary. Fruits fleshy or dry drupaceous, or mericarps 2 (2-seeded) or 4 ( 4-seeded), or a capsule; seeds 4 per fruit, often less by abortion; endosperm present or absent; cotyledons entire of flat, or rarely plicate (Cordia and Varronia).  

Notes on delimitation

• The family is circumscribed broadly, including Hydrophyllaceae (except Hydrolea L.) and Lennoaceae.
• It is considered monophyletic on the basis of inflorescence type and DNA sequences data (Ferguson 1999; Gottschling et al. 2001).

Distinguishing characters (always present)

• Leaves usually alternate, exstipulate.
• Inflorescence cymose, the branches often scorpioid, helicoid, or reduced and capitate to glomerate.
• Corolla gamopetalous.
• Stamens isomerous inserted in the corolla tube.
• Ovary superior, 2-carpellate, but usually becoming falsely 4-locular.

Other important characters

• Cystoliths commonly present.

Number of genera

The Boraginaceae comprise approximately 205 genera and 2500 species worldwide, of which 23 genera and approximately 500 species are neotropical.

Neotropical genera:

• Amsinckia Lehm.
• Antiphytum DC. ex Meisn.
• Bourreria P.Browne
• Cordia (including Auxemma Miers, Patagonula L. and Saccellium Humb. & Bonpl.)
• Cryptantha Lehm. ex Fisch. & C.A.Mey.
• Ehretia
• Hackelia Opiz
• Heliotropium
• Lasiarrhenum I.M. Johnst.
• Lennoa
• Lepidocordia Ducke
• Lithospermum L.
• Macromeria D.Don
• Moritzia DC. ex Meisn.
• Nama L.
• Pectocarya DC. ex Meisn.
• Phacelia
• Plagiobothrys
• Rochefortia Sw.
• Tiquilia Pers.
• Tournefortia
• Wigandia Kunth
• Varronia P.Browne

Useful tips for generic identification

• Habit
• Inflorescence
• Style
• Fruit

Notable genera and distinguishing features

• Cordia is characterized by the habit (trees or shrubs); inflorescence cymose, the branches often scorpioid, helicoid; terminal style twice bifid forming four stigmatic lobes; fruit drupaceous. 
• Varronia is characterized by the habit (multi-stemmed shrubs or rarely several-stemmed treelets); inflorescence reduced, capitate, glomerate, spicate, or if cymose, these less than 4 cm broad; terminal style twice bifid forming four stigmatic lobes; fruit drupaceous. 
• Heliotropium is characterized by a terminal style and dry fruits, which divide into four or two mericarps.
• Tournefortia is characterized by a terminal style and drupaceous fruits, which never divide into mericarps.
• Ehretia is characterized by the habit (trees or shrubs), and bifid terminal style.

Status

• Many species have been introduced as ornamental plants or weeds, e.g. the genera Anchusa L., Borago L., Cynoglossum L., Echium L., Myosotis L. and Symphytum L..
• The genus Varronia is endemic.

Important literature

Candolle, A.P. de. 1845. Borragineae. Pp. 467-501. In De Candolle, A. (ed.), Prodromus Systematis Naturalis Regni Vegetabilis, 9. Treuttel & Würtz, Paris.

Diane, N., H. Förther & H.H. Hilger. 2002. 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.

Ferguson, D. M. 1999. Phylogenetic analysis and relationships in Hydrophyllaceae s. str. based on ndhF sequence data. Syst. Bot. 23: 253-268.

Gottschling, M. & J.S. Miller. 2006. Clarification of the taxonomic position of Auxemma, Patagonula, and Saccellium (Cordiaceae, Boraginales). Syst. Bot. 31(2): 361-367.

Gottschling, M., H.H. Hilger, M. Wolf & N. Diane. 2001. Secondary structure of the ITS1 transcript and its application in a reconstruction of the phylogeny of Boraginales. Plant Biology 3: 629-636.

Gottschling, M., M. Weigend & H.H. Hilger. 2005. Congruence of a phylogeny of Cordiaceae (Boraginales) inferred from ITS1 sequence data with morphology, ecology, and biogeography. Ann. Missouri Bot. Gard. 92: 425-437.

Miller, J.S. & M. Gottschling. 2007. Generic classification in the Cordiaceae (Boraginales): Resurrection of the genus Varronia P. Br. (Cordiaceae). Taxon 56(1): 163-169.

Yatskievych, G. and C.T. Mason. 1986. A revision of the Lennoaceae. Syst. Bot. 11: 531-548.

Smith, R.A., D.M. Ferguson, T.J. Barkman & C.W. Pamphilis. 2000. Molecular phylogenetic evidence for the origin of Lennoaceae: A case of adelphoparasitism in the angiosperms? Amer. J. Bot. [Suppl.] 87: 158.

Stapf, M.N.S. 2007.  Avaliação da classificação infragenérica de Cordia L. (Cordiaceae) e revisão taxonómica de Cordia sect. Pilicordia DC. Para o Brasil.  Tese Doutorado Botánica, Feira de Santana: Universidade Estadual de Feira, Brasil.

How to cite

Stapf, M.N.S. (2009). Neotropical Boraginaceae. In: Milliken, W., Klitgård, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://www.kew.org/science/tropamerica/neotropikey/families/Boraginaceae.htm.