Land planarians (Platyhelminthes) as a model organism for fine-scale phylogeographic studies: understanding patterns of biodiversity in the Brazilian Atlantic Forest hotspot

Abstract

The Brazilian Atlantic Forest is one of the richest biodiversity hotspots of the world. Paleoclimatic models have predicted two large stability regions in its northern and central parts, whereas southern regions might have suffered strong instability during Pleistocene glaciations. Molecular phylogeographic and endemism studies show, nevertheless, contradictory results: although some results validate these predictions, other data suggest that paleoclimatic models fail to predict stable rainforest areas in the south. Most studies, however, have surveyed species with relatively high dispersal rates whereas taxa with lower dispersion capabilities should be better predictors of habitat stability. Here, we have used two land planarian species as model organisms to analyse the patterns and levels of nucleotide diversity on a locality within the Southern Atlantic Forest. We find that both species harbour high levels of genetic variability without exhibiting the molecular footprint of recent colonization or population expansions, suggesting a long‐term stability scenario. The results reflect, therefore, that paleoclimatic models may fail to detect refugia in the Southern Atlantic Forest, and that model organisms with low dispersal capability can improve the resolution of these models.

Planarian (Platyhelminthes, Tricladida) Diversity and Molecular Markers: A New View of an Old Group

“…These ideas were applied in a study of the Brazilian Atlantic Forest (BAF, one of the richest biodiversity areas in the world and also one of the most endangered. Using two species of terrestrial planarians as model organisms, and two molecular markers (the mitochondrial Cox1 and the nuclear ITS-1) to analyse the patterns and levels of nucleotide diversity in an area of the South American Atlantic Forest (SAF; Serra da Bocaina (SP)), it was found that both species have high levels of genetic variation, without showing the molecular fingerprint of a recent colonization and population expansion [30]. These data suggest a scenario of long-term stability, and therefore, contradict studies based on paleoclimatic models suggesting that the southern parts of the BAF had lost all forest cover during the Pleistocene glaciation period.…”

Insights into the origin and distribution of biodiversity in the Brazilian Atlantic forest hot spot: a statistical phylogeographic study using a low-dispersal organism

“…We amplified and sequenced B800 bp of the mitochondrial gene cytochrome oxidase I (COI) and B500 bp of the nuclear ribosomal internal transcribed spacer-1 (ITS-1) as described in Alvarez-Presas et al (2011).…”

“…Land planarians (Platyhelminthes, Tricladida, Geoplanidae) are particularly appropriate for fine geographical scale genetic studies (Sunnucks et al, 2006;Alvarez-Presas et al, 2011 because of their poor vagility and low capacity to prevent water loss, thus being strongly dependent on environmental moisture (Froehlich, 1955;McDonald and Jones, 2007). They seemingly withstand this limitation through behavioural strategies, such as hiding in damp soil refuges in the forest during the day and becoming active during the night.…”

Hidden diversity in forest soils: Characterization and comparison of terrestrial flatworm’s communities in two national parks in Spain

“…Samples preserved in 100% ethanol were used for DNA extraction with the Wizard ® Genomic purification kit (Promega, Madison, WI, USA) following the same protocol as in Álvarez‐Presas, Carbayo, Rozas, and Riutort (2011). A fragment of the gene encoding the mitochondrial cytochrome oxidase I (Cox1) was analyzed by polymerase chain reaction (PCR) together with three nuclear genes: genes encoding the 18S type II rRNA (18S) and 28S rRNA (28S) and a fragment of Elongation Factor 1‐alpha (EF).…”

“…For 18S and 28S, we used primers and PCR conditions as in Álvarez‐Presas, Baguñà, and Riutort (2008) for Cox1 as in Álvarez‐Presas et al. (2011) and for the EF as in Carbayo et al. (2013).…”