Mitochondrial DNA Differentiation Between Two Cryptic Halictus (Hymenoptera: Halictidae) Species

Halictus ligatus Say and its cryptic sibling species H. poeyi Lepeletier were sampled from an area of sympatry and typed for mitochondrial DNA sequence differentiation, as was 1 individual of each species from allopatric populations. Two other species, H. rubicundus (Christ) and H. farinosus Smith, were included to root the tree. Phylogenetic analysis of the aligned sequences showed that H. ligatus and H. poeyi are sister species and differ from each other at 33 of the 797 aligned nucleotide positions. Sequence divergence within species was <0.6%, whereas that between species exceeded 4%. These data support an earlier report that H. ligatus and H. poeyi represent distinct species (based on nuclear allozyme markers) and are sufficient to cast doubt on a recent glaciationinduced speciation event as the cause of the differentiation of these 2 taxa.