Cytogenetics and Hybridization of Portulaca in Hawaii

Artificial hybridization in the Hawaiian endemic genus Labordia (Loganiaceae)

“…of Bidens (Gillett and Lim, 1970;Ganders and Nagata, 1984), Tetramolopium (Lowrey and Crawford, 1985), Lipochaeta (Gardner, 1979;Rabakonandrianina, 1980), Dubautia, Argyroxiphium, and Wilkesia Kyhos, 1981, 1986;Carr, 1985;Crins, Bohm, and Carr, 1988) support this hypothesis. The same condition has been reported for Wikstroemia (Thymelaeaceae; Mayer, 1991) and intrasectional species of Portulaca (Portulacaceae; Kim and Carr, 1990). Natural hybridization has only been documented with cytotaxonomic studies of the silversword alliance and Portulaca and with randomly amplified polymorphic DNA analysis of the genus Cyrtandra (Smith, Burke, and Wagner, 1996), although Gillett (1972), Carlquist (1974), and Wagner, Herbst, and Sohmer (1990) have suggested the occurrence of natural hybrids in many additional Hawaiian genera based upon morphological intermediacy among populations.…”

“…Labordia species, at the level examined (F 1 ), are similar to many other Hawaiian plant lineages (Rabakonandrianina, 1980;Ganders and Nagata, 1984;Lowrey and Crawford, 1985;Carr and Kyhos, 1986;Kim and Carr, 1990;Mayer, 1991) in that they appear to lack genetic barriers that prevent hybridization. Many plant lineages previously investigated included fast-growing species (many from a single family, Asteraceae) that were cultivated under greenhouse conditions.…”

Adaptive radiation of shrubby tarweeds (Deinandra) in the California Islands parallels diversification of the Hawaiian silversword alliance (Compositae–Madiinae)

“…2), shrubby tarweeds on GI and other shrubby taxa of Deinandra are nested within a wellsupported grade of annual, mainland species and represent at least one example of woodiness derived from an ancestrally herbaceous condition, as resolved for the silversword alliance and as commonly associated with plant evolution on oceanic islands (Carlquist, 1974(Carlquist, , 1995Givnish, 1998;Panero et al, 1999). Lack of sterility barriers associated with diversification and occurrence of natural hybridization apparently limited by ecological differences between parental taxa are other features that the shrubby tarweeds of GI share with the silversword alliance Friar et al, 2006) and various other examples of plant insular diversification (e.g., Ganders and Nagata, 1984;Lowrey and Crawford, 1985;Kim and Carr, 1990;Mayer, 1991;Smith et al, 1996;Motley and Carr, 1998), and with recently diverged woody plants in general (Grant, 1981;Ellstrand et al, 1996). In both the GI and Hawaiian-silversword-alliance lineages, at least partial interfertility between even the most morphologically and ecologically disparate species contrasts with intersterility between closely related, herbaceous species on the North American mainland (Clausen, 1951;Kyhos et al, 1990).…”

Interspecific compatibility among 15 Leucaena species (Leguminosae: Mimosoideae) via artificial hybridizations

“…These species were qualitatively 100% intercompatible among all six tested two-way combinations (vs. 74% for 65 diploid and 77% for 47 triploid matings) and highly intercompatible quantitatively (with a CI of 73%, vs. 32% for diploid matings and 12% for triploid matings). Although exceptions exist (e.g., the semiwoody legume Crotolaria: Mangotra and Koul, 1991, and Trifolium;Quiros and Bauchan, 1988), interspecific matings among polyploid plant species are usually more successful than those among diploids (Harlan and de Wet, 1975;Kim and Carr, 1990). Harlan and de Wet's (1975) explanation for the general ease of polyploid plant species to successfully hybridize was that polyploidy (genetic redundancy) buffers the shock of alien germplasm in wide hybrids.…”