9. Creeping Fruitless Falls
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variable among isolated mother plants having no opposite morph flower in the
neighborhood within 5 m than for the mothers having potential mating partners in
their neighborhoods. However, there was no significant difference in survival and
relative growth rate of the established seedlings between the mother groups differing in degree of isolation. Moreover, the level of allozyme heterozygosity of the
progeny surviving to this stage did not significantly differ between the isolated and
less isolated mothers. Therefore, it is suggested that strong inbreeding depression
manifests in the early life stages of the progeny, and purges less fit homozygotes by
the stage of seedling establishment. It is suggested that isolated mothers can leave
much fewer fit progeny than expected from the quantity of seeds produced.
4 Complete Reproductive Failure in the Highly
Endangered Species Primu/a kisoana
We can find another remarkable example of reproductive failure due to solitude in
Primula kisoana that is a rare local endemic with an extremely narrow geographic
range in the northern part of Kanto district. The species is also distylous and closely
associated with deciduous forest habitats on steep mountainous slopes. Phylogenetically, P. kisoana is very close to P. sieboldii and shares may floral traits, though
its clonal growth mode with long underground stolons is much dissimilar to that of
P. sieboldii with stunted rhizomes.
In recent decades, the habitats of this species have been greatly reduced and
highly fragmented due to expanding cedar plantations. In addition, the original
rareness tends to incur excessive exploitation of the species for commercial horticultural use. Therefore, the population has been continuously dwindling, and also
might repeatedly experience strong population bottlenecks. Recent invasion of remaining habitats by wild boars, which have originated from those artificially released for sport shooting, are also deadly threats to the species through trampling
and digging of the roots.
Each remaining patch of the species we can find today consists of a single genet
of either long- or short-styled morph, and as a matter of course, no seeds are set
despite occasional visitation of the flowers by long-tongued bumblebee queens.
In the flowering seasons of 1996-1997, we performed artificial legitimate pollination by using the pollen transported from the opposite morph flowers through
several kilometers of trekking. The seeds set by the hand pollinated flowers, however, were less vigorous and could not germinate even after laboratory treatments
which are known to be favorable for the germination of many herbs including P.
sieboldii, i.e., moist chilling and temperature alternation (Washitani and Kabaya
1988; Washitani 1987; Washitani and Masuda 1990). After some trial-and-error,
we could obtain seedlings through dormancy breaking with Giberellic acid. Planting the carefully raised seedlings in apparent safe-sites (in sensu Harper 1977) in
the historical range of the species, we are attempting to restore local self-sustainable populations including both long- and short-styled morphs.
137
variable among isolated mother plants having no opposite morph flower in the
neighborhood within 5 m than for the mothers having potential mating partners in
their neighborhoods. However, there was no significant difference in survival and
relative growth rate of the established seedlings between the mother groups differing in degree of isolation. Moreover, the level of allozyme heterozygosity of the
progeny surviving to this stage did not significantly differ between the isolated and
less isolated mothers. Therefore, it is suggested that strong inbreeding depression
manifests in the early life stages of the progeny, and purges less fit homozygotes by
the stage of seedling establishment. It is suggested that isolated mothers can leave
much fewer fit progeny than expected from the quantity of seeds produced.
4 Complete Reproductive Failure in the Highly
Endangered Species Primu/a kisoana
We can find another remarkable example of reproductive failure due to solitude in
Primula kisoana that is a rare local endemic with an extremely narrow geographic
range in the northern part of Kanto district. The species is also distylous and closely
associated with deciduous forest habitats on steep mountainous slopes. Phylogenetically, P. kisoana is very close to P. sieboldii and shares may floral traits, though
its clonal growth mode with long underground stolons is much dissimilar to that of
P. sieboldii with stunted rhizomes.
In recent decades, the habitats of this species have been greatly reduced and
highly fragmented due to expanding cedar plantations. In addition, the original
rareness tends to incur excessive exploitation of the species for commercial horticultural use. Therefore, the population has been continuously dwindling, and also
might repeatedly experience strong population bottlenecks. Recent invasion of remaining habitats by wild boars, which have originated from those artificially released for sport shooting, are also deadly threats to the species through trampling
and digging of the roots.
Each remaining patch of the species we can find today consists of a single genet
of either long- or short-styled morph, and as a matter of course, no seeds are set
despite occasional visitation of the flowers by long-tongued bumblebee queens.
In the flowering seasons of 1996-1997, we performed artificial legitimate pollination by using the pollen transported from the opposite morph flowers through
several kilometers of trekking. The seeds set by the hand pollinated flowers, however, were less vigorous and could not germinate even after laboratory treatments
which are known to be favorable for the germination of many herbs including P.
sieboldii, i.e., moist chilling and temperature alternation (Washitani and Kabaya
1988; Washitani 1987; Washitani and Masuda 1990). After some trial-and-error,
we could obtain seedlings through dormancy breaking with Giberellic acid. Planting the carefully raised seedlings in apparent safe-sites (in sensu Harper 1977) in
the historical range of the species, we are attempting to restore local self-sustainable populations including both long- and short-styled morphs.