Ground-Dwelling and Vegetation Ant Fauna in Southern Brazilian Grasslands

Abstract

Non-forest ecosystems, as natural grasslands from Southern Brazil, are still neglected in conservation policies. Measuring their biodiversity is one of the main steps to generate management strategies for these habitats. This study aims to (i) describe grassland ant richness and composition in Rio Grande do Sul state, and (ii) compare ant communities sampled on the ground and in grassland vegetation, adding to our knowledge of habitat use patterns and vegetation associated species. Six sites were sampled, three belonging to the Pampa biome and three in highland region from the Atlantic Forest biome. Ant fauna was collected once per year in summer during four years in each site with pitfalls traps and sweeping nets. Overall, 29,812 ant individuals were sampled belonging to eight subfamilies, 30 genera e 106 species. The grasslands of Pampa accumulated 91 species and 45 exclusive species, while highland grasslands summed up 61 species and only 15 exclusive species. Species composition differs between biomes as well as between sampling methods. Ant communities sampled from vegetation represented a clear subset of the fauna sampled with pitfall traps, and indication analysis showed only two species associated with this stratum: Myrmelachista gallicola and Pseudomyrmex nr. flavidulus. This study highlights the importance of Southern Brazilian grasslands and the need for specific conservation strategies for the natural grasslands from each biome.

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

“…This work joins recent studies that assessed ant communities in the grassland/mixed forest mosaics of the southern Atlantic forest (Pinheiro et al 2010, Dröse et al 2017, Franco & Feitosa 2018. Our results provide insights on the drivers of community organization, and suggest that the combination of relatively high latitude and altitude gives to the ant community some features of temperate habitats, thus distinct from the dense Atlantic Forest and from most Brazilian ecosystems.…”

“…Ants are thermophilic animals (Pie 2016) and, below a certain threshold, less species are able to tolerate low insolation and temperature inside forests. Even considering only grasslands, a decrease in species richness might be observed with altitude (Dröse et al 2017). Thus, although most species we found also occur in dense Atlantic Forest, the community is organized differently, and some species change their behavior accordingly.…”

“…The combination of pitfalls and leaf litter collection on the ground is strongly advised for biodiversity assessments (Alonso & Agosti 2000, Bestelmeyer et al 2000, King & Porter 2005, Lopes & Vasconcelos 2008, since the first method catch larger and more active species (Sabu et al 2011), while the second is efficient to sample smaller and less active ants, including cryptic species (Fisher 1999). Finally, our sampling effort in grasslands sites, a poorly surveyed physiognomy until now in Santa Catarina, is another important source of those new records, a trend that is increasingly highlighted in other grasslands surveys of South Brazil recently published (Pinheiro et al 2010, Rosado et al 2012, Dröse et al 2017, Franco & Feitosa 2018.…”

“…However, the low efficiency of the pitfalls and lack of exclusive species suggests a relatively small arboreal community. In grasslands, it was also observed that few species occur exclusively in vegetation (Dröse et al 2017). Most plants in this habitat do not provide proper nesting sites above the ground, and these would be even more affected by cold temperatures.…”

“…Silva & Lopes 1997, Freitas et al 2014, Silva & Brandão 2014. Comparatively little is known about highland mixed forests and grasslands (Ulysséa et al 2011), which only recently started to be systematically investigated (Pinheiro et al 2010, Dröse et al 2017, Franco & Feitosa 2018. We contributed to fill this knowledge gap with the first standardized assessment on the forest-grassland mosaic found in the highlands of the state of Santa Catarina, as a part of the "Programa de Pesquisa em Biodiversidade (PPBio) da Mata Atlântica" (Atlantic Forest Research Program on Biodiversity).…”