Simple does not mean poor: grasslands and forests harbor similar ant species richness and distinct composition in highlands of southern Brazil

Abstract: Several studies addressed ant communities in the dense Atlantic Forest that runs along the Brazilian coast. However, comparatively little is known about the mixed forests and grasslands that occur in the southern range of the Atlantic Forest domain. In this study we performed the first standardized assessment of ants in the forest-grassland mosaic found in the highlands of the state of Santa Catarina. We aimed to investigate and compare ant richness and composition between mixed forests and grasslands in the main mountain range of south Brazil. Ants were collected in two years with ground pitfalls, tree pitfalls and litter samples. Sixty ant species were recorded, resulting in 22 new records for "Planalto Serrano" region and three for the state of Santa Catarina: Eurhopalothrix depressa, Pheidole radoszkowskii and Wasmannia williamsoni. There was significant dissimilarity in ant species composition between grasslands and forests, but no difference in ant species richness, even considering the higher number of strata in mixed forests. Similar richness and low number of arboreal species suggest that this ant community is structured similarly to temperate ones. Both habitats presented a large proportion of exclusive species. The fact that species composition between grassland and forest areas differed, coupled with the similarity in species richness between habitats and the record of new ant species for the region, calls for strong conservation efforts in grasslands of southern Brazil, which still are little protected by conservation areas.

摘要：沿巴西海岸分布的茂密大西洋森林（Atlantic Forest）中的蚂蚁群落，已有多项研究予以探讨，但学界对大西洋森林分布区南部的混交林与草原群落的认知仍相对匮乏。本研究针对圣卡塔琳娜州（Santa Catarina）高地分布的林草镶嵌景观开展首次标准化蚂蚁调查，旨在探究巴西南部主要山地范围内混交林与草原的蚂蚁物种丰富度及物种组成差异。研究历时两年，采用地面陷阱（ground pitfalls）、树栖陷阱（tree pitfalls）及枯落物采样（litter samples）法采集蚂蚁样本，共计记录到60个蚂蚁物种，其中包含「普拉纳图塞拉诺（Planalto Serrano）」地区的22个新分布记录，以及圣卡塔琳娜州的3个新分布记录：短扁平胸蚁（Eurhopalothrix depressa）、拉多什克氏大头蚁（Pheidole radoszkowskii）与威廉氏沃斯曼蚁（Wasmannia williamsoni）。分析结果显示，草原与森林的蚂蚁物种组成存在显著差异，但即便考虑到混交林拥有更多的植被层，二者的蚂蚁物种丰富度并无显著差异。相似的物种丰富度与较低的树栖蚂蚁物种数量，表明该蚂蚁群落的构建模式与温带蚂蚁群落相似。两种生境均包含大量特有物种。鉴于草原与森林的物种组成存在差异、两类生境的物种丰富度相近，且本研究记录了该区域的蚂蚁新物种，亟需加强巴西南部草原的保护工作——目前该类生境的受保护面积仍极为有限。