Abstract
Understanding patterns of species diversity relies on accurate taxonomy which can only be achieved by long‐term natural history research and the use of complementary information to establish species boundaries among cryptic taxa. We used DNA barcoding to characterize the ant diversity of Iguazú National Park (INP), a protected area of the Upper Paraná Atlantic Forest ecoregion, located at the southernmost extent of this forest. We assessed ant diversity using both cytochrome c oxidase subunit 1 (COI) sequences and traditional morphological approaches, and compared the results of these two methods. We successfully obtained COI sequences for 312 specimens belonging to 124 species, providing a DNA barcode reference library for nearly 50% of the currently known ant fauna of INP. Our results support a clear barcode gap for all but two species, with a mean intraspecific divergence of 0.72%, and an average congeneric distance of 17.25%. Congruently, the library assembled here was useful for the discrimination of the ants of INP and allowed us to link unidentified males and queens to their worker castes. To detect overlooked diversity, we classified the DNA barcodes into Molecular Operational Taxonomic Units (MOTUs) using three different clustering algorithms, and compared their number and composition to that of reference species identified based on morphology. The MOTU count was always higher than that of reference species regardless of the method, suggesting that the diversity of ants at INP could be between 6% and 10% higher than currently recognized. Lastly, our survey contributed with 78 new barcode clusters to the global DNA barcode reference library, and added 36 new records of ant species for the INP, being 23 of them new citations for Argentina.
Highlights
Comprehensive species inventories are prerequisites for conservation planning and for understanding ecological processes such as the role of biodiversity in ecosystem stability and function (Bickford et al, 2007; Coleman & Whitman, 2005; Mace, 2004)
The use of sequence-based specimen identification, known as DNA barcoding (Hebert, Cywinska, Ball, & deWaard, 2003), is increasingly proving to be a useful tool for species identification and diversity assessment (e.g., Delsinne et al, 2012; Ferreira, Poteaux, Delabie, Fresneau, & Rybak, 2010; Hebert, Penton, Burns, Janzen, & Hallwachs, 2004; Zenker et al, 2016). This technique is based on the amplification and analysis of a standardized short sequence of mitochondrial DNA near the 5′ end of the cytochrome c oxidase subunit I (COI) gene and relies on the premise that intraspecific diversity is predictably lower than interspecific diversity at this locus, even between closely related species (Hebert, Cywinska, et al, 2003; Hebert, Ratnasingham, & Waard, 2003)
As the results were almost identical between these two methods, and because Kimura 2-parameter (K2P) is the most common model implemented in DNA barcoding and allows a more direct comparison with previous studies, we only report those obtained using K2P
Summary
Comprehensive species inventories are prerequisites for conservation planning and for understanding ecological processes such as the role of biodiversity in ecosystem stability and function (Bickford et al, 2007; Coleman & Whitman, 2005; Mace, 2004). When coupled with different clustering algorithms, DNA barcodes can be used to delimit Molecular Operational Taxonomic Units (MOTUs): clusters of sequences grouped together based on similarity (Floyd, Abebe, Papert, & Blaxter, 2002) These MOTUs can be used to accelerate specimen identification, unveil cryptic diversity, test species delimitation hypothesis (e.g., Ramalho, Santos, Fernandes, Morini, & Bueno, 2016), or to perform fast census of animal diversity that could serve as the basis for subsequent taxonomic work (e.g., Smith, Hallwachs, Janzen, & Longino, 2014). Coupled with the limitation that most taxonomic keys to species level are based solely on worker castes, associating queens and males to workers in inventories can be problematic This undermines the scope of diversity studies and ecological work in general, for example, by impeding the study of the phenology of ant reproduction (e.g., Feitosa et al, 2016; Kaspari, Pickering, & Windsor, 2001). We compared MOTU counts and their composition across methods and assessed the correspondence between reference species and MOTUs boundaries
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