About flat mites

Adventive species and invasiveness

Mesa et al. (2009) lists the number of flat mite species described from the Nearctic region as 138 species in 6 genera, and according to Baker and Yin (1988) over 250 species have been reported in the USA. This means that a significant number of exotic species are present, or have been reported, in the USA to date.

Despite their economic importance, flat mites remain poorly understood world-wide. This is due mainly to a lack of collecting globally and unfortunately to poor taxonomy. With most geographic regions remaining significantly under-collected, little can be concluded about species distributions and invasiveness, nor about the relationships within the group. The current geographic patterns reflect more the distribution of active acarologists than they do actual species richness. We can say for sure that based on the number of interceptions from 1990 to 2011, the number of flat mites entering the USA is on the rise, and these interceptions are closely associated with the increase in trade of ornamentals, fruits, and other crops world-wide.

Biogeographic patterns based on what we know so far, for the largest tenuipalpid genera, are as follows:

• Brevipalpus is a new world group with most diversity occurring in the Neotropical region, followed by the Nearctic region.
• Raoiella is a mainly Austral-Asian group.
• Tenuipalpus appears to be a mostly old world group with most diversity occurring in the African region, followed by the Oriental and Neotropical regions.
• Aegyptobia is most diverse in the Nearctic region, followed closely by the Western Palearctic region.
• Cenopalpus is most diverse in the Western Paleartic region, with most of the species known from Mediterranean countries.