The Opuntia (Cactaceae) and Dactylopius (Hemiptera: Dactylopiidae) in Mexico: a historical perspective of use, interaction and distribution with particular emphasis on chemical and phylogenetic aspects of the Dactylopius species

Historical aspects on the use and production of Mexican species of Dactylopius (Hemiptera: Dactylopiidae) and Opuntia (Cactaceae: Opuntioidae), as well as on their origin, diversity and distribution were investigated. Main issues on the conservation of these taxa are discussed. The colorant of five species of Dactylopius was analyzed using high-performance liquid chromatography with a photodiode array detector, and phylogeny of these insects was analyzed through PCR amplified 12S rRNA and 18S rRNA gene sequences. Opuntia and Dactylopius are endemic to the American Continent, Opuntia spp. being among the main components of human diet during pre-agricultural times and their cultivation started several hundred years ago, whereas cochineal was used and probably cultivated at least from the tenth century. Mexico is one of the main areas of diversity of Opuntia, having 83-104 out of nearly 200 species worldwide. More than 50 species are used mainly as food, fodder and medicine and 20 species are cultivated with different degrees of domestication. Dactylopius includes nine species, with five of them naturally occurring in Mexico, with a distribution corresponding with that of their hosts. Arid and semi-arid areas of Mexico are among the most important reservoirs of biological diversity for both genera, particularly for D. coccus. Only D. coccus has been cultivated and domesticated but other wild species have been used throughout history as a source of natural red colorant, among other uses. The chemical analysis allowed each species to be identified on the basis of differences in their metabolic profiles, and to be recognized as a source of colorant. The first molecular analysis of Dactylopius species was obtained. These analyses were useful to describe Dactylopius-Opuntioideae host association. Specific measures for protecting such biodiversity and genetic resources are necessary. Particularly, strategies for in situ conservation associated with the promotion of cochineal use and production are promising policies.