AsianScientist (Mar. 12, 2018) – Scientists in Japan have integrated population genetics and landscape ecology to examine how recent landscape changes such as habitat fragmentation have affected the genetic diversity of the endangered maple tree. They published their findings in Biological Conservation.
The conservation of river floodplain ecosystems is one of the greatest challenges of the 21st century. Forests on the banks of rivers or along streams often support a rich and unique array of plant and animal life, due, in part, to the high soil moisture. These areas are important in maintaining water quality, preventing erosion and provide important habitat for wildlife. Unfortunately, many of these forests have been fragmented, affecting the ability of plants and animals to move freely, also affecting other ecological processes, such as nutrient and gene flow.
Ensuring that these forests remain connected with each other through the establishment of ‘corridors’, areas of habitat connecting otherwise fragmented habitats, is vital in conserving these ecologically important sites. However, information on how to implement a network of these corridors to allow maximum effectiveness is limited, especially for river floodplain ecosystems.
In this study, a research group led by Dr. Ikuyo Saeki of the University of Tsukuba, Japan, examined gene flow in the endangered maple, Acer miyabei, using landscape genetics, a powerful and increasingly popular tool in conservation projects.
A. miyabei only inhabits rare and undisturbed lowland floodplains in northern Japan. Its population is declining due to habitat loss and fragmentation. Over the past 50 years, most of the flat lowlands and natural forests have been largely converted to urban and agricultural uses. A. miyabei is pollinated by insects and its seeds dispersed by wind and water. Its long lifespan allows comparison between genetic variation in young (small) and mature (large) individuals.
The researchers categorized trees as young or mature by measuring the diameter of the largest stem at breast height (DBH). Young trees had a smaller DBH than older trees. Leaf tissues for DNA extraction were collected from 290 trees at 13 sites covering seven river basins. A DNA genotype was then obtained for each tree and compared between the 13 populations, as well as between small and large trees within each population using advanced landscape genetic techniques.
Overall, the small tree groups had a higher level of genetic differentiation than the large tree groups. This suggests that younger trees are exposed to greater genetic isolation than older trees owing to recent forest fragmentation. Because the gene flow between younger populations of trees is reduced, they share fewer variant forms of a gene. This effect may be explained by the tree’s method of reproduction—pollination by flies—which reproduce in leaf litter.
Thus, the loss of forests likely reduces gene flow via pollination. The study also found that surrounding forests, as well as forests along rivers, are important for maintaining gene flow in A. miyabei.
The researchers concluded that remnant populations of A. miyabei are important as reservoirs of genetic diversity and their habitats should be conserved. To promote connectivity, they recommend preserving forests along rivers as well as the forests surrounding them. Areas around genetically isolated populations should also be given priority.
The article can be found at: Saeki et al. (2018) Landscape Genetics of a Threatened Maple, Acer miyabei: Implications for Restoring Riparian Forest Connectivity.
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Source: University of Tsukuba.
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