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Evolution of Hawaiian Ferns and Fern Allies in Relation to Their Conservation Status

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Title: Evolution of Hawaiian Ferns and Fern Allies in Relation to Their Conservation Status
Authors: Wagner, Warren Herb Jr.
Issue Date: Jan 1995
Publisher: University of Hawaii Press
Citation: Wagner WH Jr. 1995. Evolution of Hawaiian ferns and fern allies in relation to their conservation status. Pac Sci 49(1): 31-41.
Abstract: Evolutionary and conservational differences between Hawaiian
pteridophytes and angiosperms involve differences in life histories (free-living
generations, fertilization, and spore dispersal). Very high base chromosome
numbers characterize the homosporous pteridophytes. Long-distance spore
dispersal took place mainly from Old World and pantropical ancestors, accounting
for some 80% of the taxa. The ratio of native pteridophyte to angiosperm
taxa in Hawai'i averages roughly 1: 6, much higher than in continental
floras with 1: 14. Two hundred twenty-four pteridophyte taxa, including hybrids
and naturalizations, are known in Hawai'i. The 170 native orthospecies
include endemics (highly variable taxa with polymorphies involving one or
more characters, monophyletic species swarms, and solitary endemics) as well
as nonendemics. Hybrid nothospecies compose an important additional component,
as do naturalized orthospecies. Most of the hybrids are sterile intermediates
that propagate by vegetative means; sexual hybrids are rare. The percentage
of naturalized species is only one-fourth that of angiosperms. Hawaiian
pteridophytes have evolved much more slowly than the angiosperms, as shown
by lower endemism (75% versus 91% overall and relatively fewer one- or two-island
endemics) and much smaller species swarms (average 1.5 versus 16.0 descendants
from each introduction in the 20 most species-rich genera, respectively). Anticipated listing of Hawaiian rare and endangered fern species
will probably comprise ca. 17% of the natives, including four believed to be
extinct. Naturalized species compose only one-fourth of the percentage in angiosperms,
and very few are pests. Habitat destruction by humans and feral
mammals is the major conservation problem. Although artificial spore banks
and whole-plant culture may help save some rare pteridophytes, the most
promising procedure is establishment of natural preserves.
ISSN: 0030-8870
Appears in Collections:Hawaii's Ferns and Fern Allies (Lycophytes) Collection
Pacific Science Volume 49, Number 1, 1995

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