Part 6 Balsaminaceae - Basellaceae - Bataceae - Begoniaceae
Balsaminaceae are represented in the islands by two members of the very decorative genus Impatiens, one of which, I. walleriana, has become naturalized in moist settings, primarily stream sides, on all of the main islands. Here it is seen growing stream-side in a private garden in Hilo (see image). The name of the genus is taken from the Latin word for impatience, referring to the touchiness of ripe seed pods, which split open with some force (although not dangerously) when touched. This behavior is captured in the name of one of the species, namely Impatiens noli-tangere, literally, don't touch! A common name for this species is Western jewel weed. An escape from gardens in the author's home province, British Columbia, is another attractive species, Impatiens glandulifera, which enjoys moist, shady sites, such as the shadowy space between my house and my neighbor's.
This New World family is represented in the Hawaiian Islands by one species, Anredera cordifolia (see image), the Madeira vine, `uala hüpë in Hawaiian. This decorative vine has escaped from cultivation; it occurs on all of the islands except Kaho`olawe, Läna`i, and Ni`ihau. For readers unfamiliar with Basellaceae suffice it to say that DNA sequence data locate the family within a group that includes Portulacaceae, which we saw above, and the very familiar Cactaceae, which we will meet later in this series. See Soltis et al. (2005) for a summary of DNA data and how they affect family relationships.
Bataceae are a small family consisting of the single genus Batis with two species, B. argillicola from New Guinea and tropical Queensland, and B. maritima (see images), from the Americas and the Hawaiian Islands where it has become naturalized in coastal areas on all of the main islands. It is commonly called pickleweed. Salicornia (Amaranthaceae), a genus of perhaps two dozen salt-tolerant (halophyllic) species, is also called pickleweed; the two genera are unrelated except in the ecological niche they occupy. Salicornia is not known from the Hawaiian Islands.
Batis was first described in the islands in 1859 from specimens collected near Sand Island, in Honolulu Bay, but was subsequently found on other islands. It is not known when the plant first appeared on the islands. Although the plant sets seeds which can easily be transported locally on tidal flow or rain runoff, long distance dispersal across expanses of ocean seems unlikely, although not impossible. Since the species occurs naturally along the tropical and subtropical coasts of the Americas and the Galapagos Islands, movement via ocean going vessels is a possibility. Flushing and refilling ships' ballast tanks, a common practice, could account for transport over great distances.
Two plants, pickleweed which we have just seen, and red mangrove (Rhizophora mangle), combine in many instances on the islands to occupy significant stretches of coastal land. Botanists are generally agreed that before colonization by Polynesians, intertidal wetlands throughout the islands were populated primarily by algae and fungi with only scattered flowering plants. Ruppia maritima, ditchgrass or widgeon grass, occurred at the low end of the intertidal zone in some areas, with salt-tolerant species, e.g., Sesuvium portulacastrum (see Aizoaceae) at the top end of the zone. Problems associated with the mangrove will be discussed in the Rhamnaceae-Rhizophoraceae section of this series.
Begoniaceae, well known for the many cultivated varieties within Begonia, are a family of only two genera, Begonia, with well over a thousand species, and Hillebrandia, a Hawaiian endemic genus of a single species, H. sandwicensis (see image) known in Hawaiian as pua maka nui or, in Kaua`i, as aka`aka`awa. The evolutionary relationship between the two genera was studied by an international group of botanists led by Wendy L. Clement of the University of Minnesota using DNA sequence information (Clement et al. 2004). Results pointed to a residence time of Hillebrandia, or a very close relative, on the Hawaiian Islands for at least 51 million years, or as much as 65 million years. Since the oldest of the current islands, Kaua`i, is about five million years old, it is necessary to postulate that Hillebrandia was present on one of the islands now long disappeared, and that its present position on the archipelago can be explained by island hopping. Island hopping within the current island flora has been recognized as a significant process, so precedent for suggesting this in the history of Hillebrandia has been well established.
Begonia hirtella (see image), one of three species of naturalized members of the family on the islands, is commonly found growing in wet, shady locations. The specimen in the photograph was growing on one of the bridges along the Häna Road on Maui.
Clement, W. L., M. C. Tebbitt, L. L. Forrest, J. E. Blair, L. Brouillet, T. Eriksson and S. M. Swensen. 2004. Phylogenetic position and biogeography of Hillebrandia sandwicensis (Begoniaceae): a rare Hawaiian relict. American Journal of Botany 91: 905-917.
Soltis, D. E., P. S. Soltis, P. K. Endress, and M. W. Chase. 2005. Phylogeny and Evolution of Angiosperms. Sinauer Associates, Inc. Publishers, Sunderland, MA.
December 3, 2011