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：此前已有多项研究针对巴西沿海沿岸的茂密大西洋森林（Atlantic Forest）中的蚂蚁群落展开探讨。然而，针对大西洋森林分布区南部的混交林与草原群落，目前相关研究仍相对匮乏。本研究针对圣卡塔琳娜州（Santa Catarina）高地的林草镶嵌景观开展了首次标准化蚂蚁调查，旨在调查并比较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群落组成。本研究历时两年，采用地面陷阱、树冠陷阱以及枯落物取样三种方式采集蚂蚁标本。本次调查共记录到60种蚂蚁，其中包含22个普拉纳托塞拉诺（Planalto Serrano）地区新记录物种，以及3个圣卡塔琳娜州新记录物种：Eurhopalothrix depressa、Pheidole radoszkowskii与Wasmannia williamsoni。研究发现，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的层位更多，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物种占比，表明该蚂蚁群落的结构与温带蚂蚁群落结构相似。两类生境均存在大量特有物种。鉴于草原与森林的蚂蚁物种组成存在差异、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，因此巴西南部草原亟需加强保护——目前这类生境的保护区覆盖率仍极低。