A FULLY FERTILE INTERGENERIC HYBRID DERIVATIVE FROM ARGYROXIPHIUM-SANDWICENSE SSP MACROCEPHALUM X DUBAUTIA-MENZIESII (ASTERACEAE) AND ITS RELEVANCE TO PLANT EVOLUTION IN THE HAWAIIAN-ISLANDS
Gd. Carr, A FULLY FERTILE INTERGENERIC HYBRID DERIVATIVE FROM ARGYROXIPHIUM-SANDWICENSE SSP MACROCEPHALUM X DUBAUTIA-MENZIESII (ASTERACEAE) AND ITS RELEVANCE TO PLANT EVOLUTION IN THE HAWAIIAN-ISLANDS, American journal of botany, 82(12), 1995, pp. 1574-1581
Achenes collected from natural putative F-1 intergeneric hybrids invol
ving Argroxiphium sandwicense DC. ssp. macrocephalum (A. Gray) Meyrat
and Dubautia menziesii (A. Gray) Keck were germinated and grown in cul
tivation, One of these apparent B-1 hybrids that approached D. menzies
ii in morphology exhibited greatly increased fertility over the F-1 (7
9% vs. 9% pollen stainability), and was used as a female parent to gen
erate a B? progeny by backcrossing a second time to D. menziesii. The
B, was surprisingly uniform. One individual that flowered was fully fe
rtile (99% pollen stainability). Its floral and vegetative features we
re extremely similar to those of the recurrent parent, D. menziesii. O
bservations suggest that plants of similar origin may exist under natu
ral conditions and that the close relatives, D. platyphylla (A. Gray)
Keck and D. dolosa (Degener & Sherff) G. Carr, may have originated fro
m the same or a similar intergeneric hybrid combination. Because many
other analogous situations occur in the silversword alliance and elsew
here in the Hawaiian flora, it is concluded that hybridization is an e
volutionarily important phenomenon, especially in unstable geological
systems, Although the Hawaiian archipelago is a premier example of suc
h instability. continents are not immune to natural perturbations. The
refore, hybridization, as a mechanism that greatly extends the size: o
f gene pools available for recombination, should also be expected to p
lay an important evolutionary role in continental floras.