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Magnolia stellata 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Magnoliopsida Magnoliales Magnoliaceae

Scientific Name: Magnolia stellata
Species Authority: (Siebold & Zucc.) Maxim.
Common Name(s):
English Star Magnolia
Synonym(s):
Magnolia kobus var. stellata (Siebold & Zucc.) Blackburn
Yulania stellata (Maxim.) N.H.Xia

Assessment Information [top]

Red List Category & Criteria: Endangered B1ab(iii,v) ver 3.1
Year Published: 2015
Date Assessed: 2015-01-07
Assessor(s): Wheeler, L. & Rivers, M.C.
Reviewer(s): Oldfield, S.
Contributor(s): Khela, S.
Justification:
Magnolia stellata is considered to be Endangered based on its restricted extent of occurrence and continuing decline in mature individuals and quality of habitat. It has an estimated extent of occurrence of 3,000 km2 and is known from less than five locations. This species is highly threatened because of urban development and local populations are small and fragmented. The species is listed as Vulnerable by the Environment Agency (2000) in Japan.

Geographic Range [top]

Range Description:Magnolia stellata is endemic to Japan where it is restricted to a narrow area in Central Honshu around Nagoya, limited to hilly areas below 600 m asl in Aichi, Gifu and Mie. The area, often called the Tokai Floristic Region is characterised by the occurrence of many local endemic or semi-endemic species such as Acer pycnanthum. The potential forest distribution is 1,854 km2 and the extent of occurrence (EOO) is estimated to be c. 3,000 km2.
Countries occurrence:
Native:
Japan (Honshu)
Additional data:
Number of Locations:1-5
Lower elevation limit (metres):30
Upper elevation limit (metres):550
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Only a few seedlings and saplings have been observed in natural stands although mature trees produce many seeds. It is possible there are constraints on seed germination. A study on the seed bank of Magnolia stellata (Kisanuki et al. 2008) showed that current-year seedlings were abundant in water channels, on moss, or under mature crowns, suggesting that the seeds may require wet soil conditions for germination. Magnolia stellata seeds show considerable germination below the crowns of mature trees in the year following masting, while some seeds remain dormant in the soil. Considering the soil seed bank and the current-year seedling bank of M. stellata, a frequent supply of seed is essential for the regeneration of this species. Thus, it is important to maintain mature trees in addition to promoting seed production.

Studies on interpopulation and inbreeding have been carried out (Tamaki et al. 2009). They found that existing M. stellata subpopulations that are small (and thus might be expected to have higher frequencies of inbreeding) and have large values of delta, may be in danger of declining, even if the subpopulations are located within the central region of the species' range. Factors influencing outcrossing rates at the individual level, such as differences in flowering phenology and early-stage inbreeding depression, appear to have important effects within these M. stellata subpopulations, but not among them (Tamaki et al. 2009).

Studies on pollination ecology using microsatellites concluded that seed production of M. stellata is strongly limited by both pollen shortage and self-pollination. Inefficient beetle-pollination and the automimicry system via asynchronous flowering might be responsible for the high level of pollen shortage and frequent geitonogamy. This is despite a large, showy floral display and the dichogamous system of the species (Hirayama et al. 2005).

It has also been found that fragmentation between certain subpopulations would reduce gene flow; subpopulations with high diversity have diverged from other subpopulations and the uniqueness of each subpopulation should be given the highest priority when planning genetic conservation measures for the species (Ueno et al. 2005).

The levels of pollen flow between fragmented subpopulations has also substantially decreased (Setsuko et al. 2007). In this study a total of 308 adults were surveyed surrounding the Yato river and the results suggest that the level of pollen flow among subpopulations has fallen recently, probably due to rapid reductions in population size, but more detailed research is required. It is known that there are 308 adult individuals in one subpopulation.
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Population severely fragmented:Unknown

Habitat and Ecology [top]

Habitat and Ecology:Magnolia stellata is a a self-compatible, insect-pollinated and protogynous small deciduous tree species growing in lowland hills, valleys, terraces, riverbeds or shallow gorges. It occurs primarily in sunny areas which are moist with continuous water flows.
Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Yes

Use and Trade [top]

Use and Trade: This species is very widely grown for ornamental purposes with many cultivars. Collecting from the wild has been noted as a threat.

Threats [top]

Major Threat(s): Subpopulations of Magnolia stellata are decreasing due to land development and illegal collecting by horticulturists. Recent human activities have damaged much of the Tokai hilly land ecosystem by construction of a golf course and housing. Natural evergreen broad leaved forests have changed in species composition as the trees were used for fuel wood for long time periods in the past but as the wood is no longer being used for fuel the evergreen broad-leaved trees are recovering by secondary succession (Setsuko et al. 2007).

Conservation Actions [top]

Conservation Actions: Magnolia stellata is threatened due to habitat loss and therefore a clear conservation strategy for this threatened species is urgently required. To conserve M. stellata, it is important to preserve the whole population by maintaining its metapopulation structure and the gene flow among its subpopulations. Gene flow is important in conservation contexts because when a species is confined to small subpopulations, its genetic characteristics are strongly influenced by genetic drift and inbreeding (Setsuko et al. 2007). In some cases, artificial treatment to maintain the gene flow among subpopulations may be necessary, e.g., thinning surrounding trees of other species may be beneficial if they are adversely affecting M. stellata habitats and thus reducing the frequency of gene flow among its subpopulations. The establishment of an in situ conservation programme is urgently needed. Magnolia stellata is a popular ornamental tree and many ex situ collections exist in botanic gardens and arboreta.

Citation: Wheeler, L. & Rivers, M.C. 2015. Magnolia stellata. The IUCN Red List of Threatened Species 2015: e.T194010A2294218. . Downloaded on 18 August 2017.
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