Departamento de Biología, Universidad de la Serena, Casilla, La Serena, Chile.
ONG Ecoterra, La Serena, Chile.
Ann Bot. 2021 Apr 17;127(5):669-680. doi: 10.1093/aob/mcaa206.
Aridity is increasing in many regions of the world, but microclimatic conditions may buffer plant communities from the direct effects of decreased precipitation, creating habitat islands. However, reduced precipitation can also impact these communities indirectly by decreasing the suitability of the surrounding habitat, thus limiting incoming propagules and increasing the chances of population decline and species loss. We test whether decreased precipitation results in loss of species and functional diversity within habitat islands, evaluating in particular whether declines in species diversity and abundance are less likely to result in loss of functional diversity if species/individual loss is stochastic (i.e. independent of species/individual traits) and communities/populations are functionally redundant.
Lomas communities are discrete plant communities embedded in the Atacama Desert, maintained by the microclimatic conditions created by fog. We recorded species and functional diversity in six Lomas communities along a 500 km long precipitation gradient in northern Chile. Functional traits were measured in 20 individuals per species, in those species that accounted for approx. 75 % of the abundance at each site. We calculated functional diversity and functional redundancy of the community, and intraspecific functional variation.
Decreased precipitation was associated with lower species diversity and lower species abundances. However, no traits or functional strategies increased or decreased consistently with precipitation, suggesting stochastic species/individual loss. Species with stress-tolerant strategies were predominant in all sites. Although species diversity decreased with decreasing precipitation, functional diversity remained unchanged. Lower functional redundancy in the drier sites suggests that mainly functionally redundant species were lost. Likewise, intraspecific functional variation was similar among communities, despite the lower species abundance in drier sites.
Decreased precipitation can impact habitat island communities indirectly by decreasing the suitability of the surrounding habitat. Our results support the idea that a stochastic loss of species/individuals from functionally redundant communities and populations does not result in loss of functional diversity.
世界上许多地区的干旱程度正在增加，但小气候条件可能使植物群落免受降水减少的直接影响，形成栖息地岛屿。然而，降水减少也会通过降低周围栖息地的适宜性间接影响这些群落，从而限制传入的繁殖体，并增加种群减少和物种丧失的可能性。我们检验降水减少是否导致栖息地岛屿内物种和功能多样性的丧失，特别评估如果物种/个体的损失是随机的（即与物种/个体特征无关），并且群落/种群在功能上是冗余的，那么物种多样性和丰度的下降是否不太可能导致功能多样性的丧失。
Lomas 群落是嵌入在阿塔卡马沙漠中的离散植物群落，由雾形成的小气候条件维持。我们在智利北部一条 500 公里长的降水梯度上的六个 Lomas 群落中记录了物种和功能多样性。在每个地点占丰度约 75%的物种中，我们测量了 20 个个体的功能特征。我们计算了群落的功能多样性和功能冗余，以及种内功能变异。
降水减少与物种多样性和物种丰度降低有关。然而，没有特征或功能策略随着降水的增加而增加或减少，这表明物种/个体的损失是随机的。在所有地点，具有耐受压力策略的物种都占优势。尽管物种多样性随着降水减少而降低，但功能多样性保持不变。在较干燥的地点，功能冗余较低，表明主要失去了功能上冗余的物种。同样，尽管在较干燥的地点物种丰度较低，但种内功能变异在群落之间相似。
降水减少会通过降低周围栖息地的适宜性间接影响栖息地岛屿群落。我们的结果支持这样一种观点，即功能上冗余的群落和种群中物种/个体的随机损失不会导致功能多样性的丧失。
