Hooftman Danny A P, van Kleunen Mark, Diemer Matthias
Institut für Umweltwissenschaften, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
Oecologia. 2003 Feb;134(3):350-9. doi: 10.1007/s00442-002-1096-0. Epub 2002 Dec 17.
Small habitat size and spatial isolation may cause plant populations to suffer from genetic drift and inbreeding, leading to a reduced fitness of individual plants. We examined the germination, establishment, growth, and reproductive capacity of two characteristic species of mown fen meadows, Carex davalliana, and Succisa pratensis, common in Switzerland. Plants were grown from seeds, which were collected in 18 habitat islands, differing in size and in degree of isolation. We used both common garden and reciprocal transplant experiments to assess effects of habitat fragmentation. In the common garden, plants of Carex originating from small habitat islands yielded 35% less biomass, 30% fewer tillers, and 45% fewer flowering tillers than plants from larger ones. In contrast, plants of Succisa originating from small habitat islands yielded 19% more biomass, 14% more flower heads and 35% more flowers per flower head than plants from larger ones. Moreover, plants of Succisa from small isolated habitats yielded 32% more rosettes than did plants from small connected islands. Reciprocally transplanted plants of Succisa originating from small habitat islands produced 7% more rosettes than plants from larger ones. There was no effect of small habitat size and isolation on germination and establishment of both species in the field. Our results document genetic differences in performance attributable to habitat fragmentation in both species. We suggest that fitness loss in Carex is caused by inbreeding depression, whereas in Succisa the differences in fitness are more likely caused by genetic differentiation. Our study implies that habitat fragmentation affects common habitat-specific species, such as Carex and Succisa, as well as rare ones.
栖息地面积小和空间隔离可能导致植物种群遭受遗传漂变和近亲繁殖，从而降低个体植物的适合度。我们研究了瑞士常见的两种割草沼泽草甸特征物种——日本苔草和草原山萝卜的萌发、定植、生长和繁殖能力。这些植物由种子培育而成，种子采集于18个栖息地岛屿，这些岛屿在大小和隔离程度上存在差异。我们采用了共同花园实验和 reciprocal 移植实验来评估栖息地破碎化的影响。在共同花园中，源自小栖息地岛屿的日本苔草植株的生物量比源自大栖息地岛屿的植株少35%，分蘖数少30%，开花分蘖数少45%。相比之下，源自小栖息地岛屿的草原山萝卜植株的生物量比源自大栖息地岛屿的植株多19%，花头多14%，每个花头的花朵多35%。此外，来自小隔离栖息地的草原山萝卜植株的莲座叶丛比来自小相连岛屿的植株多32%。源自小栖息地岛屿的草原山萝卜 reciprocal 移植植株的莲座叶丛比源自大栖息地岛屿的植株多7%。小栖息地大小和隔离对这两个物种在田间的萌发和定植没有影响。我们的结果证明了这两个物种中归因于栖息地破碎化的表现上的遗传差异。我们认为，日本苔草适合度的损失是由近亲繁殖衰退引起的，而草原山萝卜适合度的差异更可能是由遗传分化引起的。我们的研究表明，栖息地破碎化影响常见的栖息地特异性物种，如日本苔草和草原山萝卜，以及珍稀物种。
