2.4. Molecular methods and systematics
Molecular technology was first used in varroa research during the 1990s to look for variation within and among mite populations (Kraus and Hunt, 1995; De Guzman et al., 1997, 1998, 1999; Anderson and Fuchs, 1998). Initially it was expensive and was only used by specialised laboratories. Currently, the landscape has changed and a number of quick and easy commercial kits can be purchased for extracting DNA from tissue and any number of laboratories will sequence DNA for a reasonable fee within hours of its extraction. Sequence data from small DNA fragments (< 1,000 base pairs) has been particularly useful in providing ‘snap-shots’ of genetic variation across the entire varroa genome and for use in phylogenetic analyses or as molecular markers (Avise, 2004). Sequencing involves three basic steps described below in sections 2.4.1., 2.4.2. and 2.4.3.: 1. Extraction of total DNA from mite tissue. 2. Amplifying (making copies of) fragments of that DNA using Polymerase Chain Reaction (PCR). 3. Sequencing the amplified fragments.