58露崎 史朗73Shiro TSUYUZAKIミズゴケ湿原の回復機構の解明と復元手法の開発 −地球環境保全を目指して−（2019採択）Clarification of revegetation mechanisms of bogs and development of the restoration techniques −toward global environmental conservation−(Project 2019)のみ塩分耐性の集団間分化が生じていることを示唆している．これらの結果は，非対称な遺伝子流動に起因する移住荷重が局所適応や新規環境への分布拡大を制限していることを示唆している．One of the most important questions in evolutionary biology is how the spatial distribution of species is limit-ed. Asymmetric gene flow from core populations is suggested to increase the number of poorly adapted immi-grants in the peripheral population at the range edge. Genetic load due to migration should prevent adaptation to the local habitat, leading to decreases in distribution range via local extinction or the limiting range expan-sion. However, relatively few experimental studies have examined the effects of immigration on fitness and natural selection within recipient populations. To investigate the influence of gene flow on distribution range, I performed field and laboratory observations and population transcriptomics for the common river snail, Semisulcospira reiniana. I found that river steepness was related to the lower distribution limit of S. reiniana, with a narrower distribution range in the steeper river. Population transcriptomic analysis showed that gene flow was heavily asymmetric between the upstream and downstream populations in the steep river, suggesting a greater migration load in the steep river. The number of genes putatively involved in adaptation to the local habitat was lower in the steep river than in the river with less steepness. Gene expression profiles suggested that individuals achieve better local adaptation in the gentle river. Laboratory experiments suggested that evo-lutionary differences in salinity tolerance among local populations was only found in the gentle river. My re-sults provided evidence that migration load owing to asymmetric gene flow disturbs local adaptation and re-stricts the distribution range of river snails.ミズゴケ湿原は，炭素吸収源としても，生物多様性保全上も高い価値を有すが，土地改変や泥炭採掘により大きく減少し，湿原の復元は喫緊の課題である．そこで，サロベツ湿原内の1972年泥炭採掘跡地において遷移系列に沿った4植生にミズゴケ移植を行い生態系復元の可能性を検証した．2017年秋に実験区を設置し，2020年秋まで，環境要因として水位，温度，光強度，土壌水分，pHを，ミズゴケ成長指標として被度，伸長成長，頭状体数，NDVIを測定した．毎年，秋にミズゴケ生存部分を採取し，バイオマスを測定した．これらの結果，移植ミズゴケは，ミズゴケの自然侵入から予測された通り，ヌマガヤ草地で良好な定着を示した．さらに，条件によってはミカヅキグサ草地でも定着成長が可能であり，成長もヌマガヤ草地を上回ることが明らかとなった．長期継続調査では非破壊的にバイオマス測定が行えることが必須だが，ミズゴケの伸長成長，被度，NDVI，頭状体数を組み合わせ，バイオマス推定式を作成することができた．これらの知見を活用することで，ミズゴケ移植により生態系復元を加速できる大きな展望を得た．Because bogs dominated by Sphagnum mosses are large carbon sink and high biodiversity but have been de-creased greatly because of landuse change and peat mining, the restoration of bogs is urgent task. To obtain the possibilities of the restoration, Sphagnum moss was transplanted to four vegetation along successional sere after peat mined in 1972 on Sarobetsu mire. Water table, peat moisture, temperature, light intensity and pH were measured as environmental factors from the autumns of 2017 to 2020 and cover, vertical growth, capit-ulum density and NDVI were measured as indicators for moss growth. The biomass was measured by the alive parts of moss harvested every autumn. The transplanted Sphagnum moss established and grew well in M. japonica grassland, as expected from the field observations. Furthermore, the transplanted moss grew larger in R. alba grassland under certain conditions than in M. japonica grassland. Because long-term monitoring re-quires non-destructive methods for biomass measurements, the estimation model was developed based on vertical growth, cover, NDVI and capitulum density of mosses. These findings show that ecosystem restora-tion is accelerated by the transplantation of Sphagnum moss.
元のページ ../index.html#62