Genetic differentiation at species level in the Neotropical army ant Labidus praedator

Abstract

The nomadic, swarm-raiding army ant Labidus praedator (Smith, 1858) is an important arthropod predator in the Neotropics with a strong ecological impact on invertebrate communities. However, despite its high abundance and ubiquity over a large distribution range, it received relatively little scientific attention. Moreover, the taxonomic status is confusing because some morphological descriptions point towards the co-occurrence of several distinct taxa which are lumped together as L. praedator in most classical keys. Yet, clarifying genetic studies are lacking. Here, we show strong genetic differentiation within an L. praedator population in Mexico. Both microsatellite genotype patterns and phylogenetic analyses (concatenated nuclear and mtDNA sequences, including the coxI genetic barcoding region), reveal the occurrence of two strongly isolated lineages. Colonies from the very same location, clearly identified as the same species (L. praedator) according to classical morphological keys, exhibit an extremely high average sequence divergence (9.7–12.8 %), which was well in the range of divergence among GenBank sequences from other Labidus species. Thus, our data very likely show genetic differentiation at species level or cryptic speciation within L. praedator, which should be recognized when investigating biodiversity and ecological importance of army ants (or other arthropods) in the Neotropics.