a megachilid bee, Lithurgus echinocacti, with Chaetodactylus mites Home

Multivariate Diagnostics of Cryptic Species of Bee Mites

Pavel Klimov ©

University of Michigan Museum of Zoology, 1109 Geddes Ave., Ann Arbor, Michigan 48109-1079 USA

Several bee mites are cryptic species. They do not have any obvious recognition characters to set them apart from the general species population. However, cryptic species are sexually isolated and often have different bee hosts. It is very important to recognize cryptic species of bee mites because each of them might interact with the host in different ways. Some parasitic mites can be very harmful if they occur on a bee other than their primary host. Such host shifts can be facilitated by the mite or bee behavior, bee parasites, or by humans in artificial settings. Thus, the accurate identification of cryptic species associated with bees is imperative to monitor for host shifts onto economically important bee species and to assess their long-term effect on the bee welfare. On the other hand, some mites are advantageous for bees, as the case of Cheletophyes preying on cleptoparasitic mites in the bee nests.
We used methods of multivariate morphometrics to distinguish between such species. Although the development of an accurate classification model is a very tedious and time consuming task, once the model is developed, unknown specimens can be easily classified. For model development, we used two alternative techniques, canonical variates analysis and logistic regression analysis. The two compliment each other when assumptions of one of them do not meet in real data. The classification is usually based on a few measurements that are used to calculate a canonical variate (discriminant function) or probabilities in a logistic regression model. The calculations and the process of classification are automated by JavaScript functions embedded in our web pages. A list of available models is given below.

• Chaetodactylus (Chaetodactylidae) associated with bees of the genus Osmia, subgenus Cephalosmia (Hymenoptera: Megachilidae)

• Chaetodactylus (Chaetodactylidae) associated with bees of the genus Lithurgus (Hymenoptera: Megachilidae) in North America

• Cheletophyes (Cheyletidae) associated with large African carpenter bees, Xylocopa nigrita and Xylocopa torrida (Hymenoptera: Apidae). Canonical variates analysis

• Cheletophyes (Cheyletidae) associated with large African carpenter bees, Xylocopa nigrita and Xylocopa torrida (Hymenoptera: Apidae). Logistic regression model

• Sennertia frontalis group (Chaetodactylidae) associated with large carpenter bees, Xylocopa spp. (Hymenoptera: Apidae) in the New World. Logistic regression model

On photo: Megachilid bee, Lithurgus echinocacti covered with mites of the genus Chaetodactylus abditus. Lithurgus echinocacti is the major pollinator of barrel cactuses (Ferocactus) in Arizona. There are three cryptic species of Chaetodactylus associated with cactus-pollinating Lithurgus in the United States.