Cryptic indirect effects of exurban edges on a woodland community
Cryptic indirect effects of exurban edges on a woodland community
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远郊边缘对林地群落的隐秘间接影响
DOI：
10.1890/es15-00318.1
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发表时间：
2015
期刊：
影响因子：
2.7
通讯作者：
M. Bradford
中科院分区：
文献类型：
--
作者：
R. Warren;S. Pearson;S. Henry;K. Rossouw;J. Love;M. Olejniczak;K. Elliott;M. Bradford
郊区发展（例如，林地中的第二居所）将城市土地使用的影响扩展到郊区以外，但由于郊区开发往往保留了原始生态系统结构的许多组成部分，例如森林树冠而不是开阔的草坪，因此其生态影响可能被低估。种子传播蚂蚁行为的变化，如边缘回避，促使郊区的土地利用，可能会对林地植物（myrmecochores），他们分散的有害影响，因此郊区森林的植物多样性。我们研究了迁移对种子传播蚂蚁筑巢和觅食、种子检索、传播方向以及随后对蚁群的影响。我们使用了一个矩阵的森林和远郊化的栖息地，以测试是否（1）远郊边缘减少蚁巢殖民和种子觅食，（2）蚂蚁分散种子远离远郊边缘，（3）因此，有较低的蚂蚁分散的植物丰度接近远郊边缘。我们发现，远郊开发对基石种子传播蚂蚁的影响很小，因为它们在破碎的林地栖息地中觅食、定居和繁荣，就像在完整的森林中一样。然而，远郊边缘改变了蚂蚁的行为，因此它们通常会将种子移向森林内部，从而远离边缘。对应于这种行为的变化，我们发现，蚂蚁分散的植物下降与接近的边缘，而其他林地草本植物的传播模式比蚂蚁不受影响。迁移对传播种子的蚂蚁生存能力几乎没有威胁，但是，通过改变觅食模式（特别是限制传播的方向性），它间接威胁到它们传播的植物。边缘对生物区系的影响通常与通过非生物资源的级联相关，但我们显示了郊区边缘，梯形蚂蚁和草本植物之间的有害生物级联。物种介导的服务，如种子传播和授粉，是关键的资源，因此，要评估土地使用变化的全部后果，就必须评估对生物相互作用的影响。
Exurban development (e.g., second homes) in woodlands spreads urban land use impacts beyond suburbs, but because exurban developments often retain many components of original ecosystem structure—such as a forest canopy rather than open lawn—their ecological impacts may be underestimated. Changes in seed-dispersing ant behavior prompted by exurban land use, such as edge avoidance, may pose deleterious impacts on the woodland plants (myrmecochores) they disperse, and hence the floristic diversity of exurban forests. We examined the effects of exurbanization on seed- dispersing ant nesting and foraging, seed retrieval, dispersal direction and subsequent impact on myrmecochores. We used a matrix of forested and exurbanized habitats to test whether (1) exurban edges decrease ant nest colonization and seed foraging, (2) ants disperse seeds away from exurban edges, and (3) consequently, there is lower ant-dispersed plant abundance nearer exurban edges. We found that exurban development poses little impact on keystone seed-dispersing ants because they foraged, colonized and thrived in fragmented woodland habitats as well as they did in intact forests. Exurban edges changed ant behavior, however, so that they generally moved seeds toward forest interiors, and, hence, away from edges. Corresponding to this behavioral change, we found that ant-dispersed plants declined with proximity to edges, whereas other woodland herbs with dispersal modes other than ants were unaffected. Exurbanization poses little threat to seed-dispersing ant viability, but, by changing foraging patterns (specifically, limiting the directionality of dispersal), it indirectly threatens the plants they disperse. Edge effects on biota commonly are associated with cascades through abiotic resources, but we show a deleterious biotic cascade between exurban edge, keystone ants and herbaceous plants. Species-mediated services, such as seed dispersal and pollination, are key resources, and assessing the full consequences of land use change therefore necessitates evaluation of impacts on biotic interactions.