Kalarus Konrad, Nowicki Piotr
Institute of Environmental Sciences, Jagiellonian University, Kraków, Poland.
PLoS One. 2015 Sep 16;10(9):e0138557. doi: 10.1371/journal.pone.0138557. eCollection 2015.
Most studies dealing with species distribution patterns on fragmented landscapes focus on the characteristics of habitat patches that influence local occurrence and abundance, but they tend to neglect the question of what drives colonization of previously unoccupied patches. In a study of the dryad butterfly, we combined classical approaches derived from metapopulation theory and landscape ecology to investigate the factors driving colonization from a recent refugium. In three consecutive transect surveys, we recorded the presence and numbers of imagos in 27 patches of xerothermic grassland and 26 patches of wet meadow. Among the predictors affecting the occurrence and abundance of the dryad, we considered environmental variables reflecting (i) habitat patch quality (e.g., goldenrod cover, shrub density, vegetation height); (ii) factors associated with habitat spatial structure (patch size, patch isolation and fragmentation); and (iii) features of patch surroundings (100-m buffers around patches) that potentially pose barriers or provide corridors. Patch colonization by the dryad was strongly limited by the distance from the species refugium in the region; there was a slight positive effect of shrub density in this respect. Butterfly abundance increased in smaller and more fragmented habitat patches; it was negatively impacted by invasive goldenrod cover, and positively influenced by the density of watercourses in patch surroundings. Nectar plant availability was positively related to species abundance in xerothermic grassland, while in wet meadow the effect was the reverse. We conclude that dryad colonization of our study area is very recent, since the most important factor limiting colonization was distance from the refugium, while the habitat quality of target patches had less relevance. In order to preserve the species, conservation managers should focus on enhancing the quality of large patches and should also direct their efforts on smaller and more fragmented ones, including those with relatively low resource availability, because such habitat fragments have an important role to play for specialist species.
大多数关于破碎化景观中物种分布模式的研究都聚焦于影响局部出现和丰度的栖息地斑块特征,但往往忽略了是什么驱动了对先前未被占据斑块的定殖这一问题。在一项关于森林女神蝶的研究中,我们结合了源自集合种群理论和景观生态学的经典方法,来探究从最近的避难所驱动定殖的因素。在连续三次样带调查中,我们记录了27个干热草原斑块和26个湿草甸斑块中成虫的存在情况和数量。在影响森林女神蝶出现和丰度的预测因子中,我们考虑了反映以下方面的环境变量:(i) 栖息地斑块质量(如一枝黄花覆盖率、灌木密度、植被高度);(ii) 与栖息地空间结构相关的因素(斑块大小、斑块隔离度和破碎化程度);以及(iii) 斑块周围环境(斑块周围100米缓冲带)的特征,这些特征可能构成障碍或提供廊道。森林女神蝶对斑块的定殖受到该区域与物种避难所距离的强烈限制;在这方面,灌木密度有轻微的积极影响。蝴蝶丰度在较小且更破碎的栖息地斑块中增加;它受到入侵的一枝黄花覆盖率的负面影响,并受到斑块周围水道密度的积极影响。花蜜植物的可利用性与干热草原中的物种丰度呈正相关,而在湿草甸中效果则相反。我们得出结论,我们研究区域内森林女神蝶的定殖是非常近期的,因为限制定殖的最重要因素是与避难所的距离,而目标斑块的栖息地质量相关性较小。为了保护该物种,保护管理者应专注于提高大型斑块的质量,同时也应将努力方向指向较小且更破碎的斑块,包括那些资源可利用性相对较低的斑块,因为这样的栖息地片段对特有物种具有重要作用。