Variation in the Parasitic Bee Mite Varroa Jacobsoni Oud. Denis Anderson
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Variation in the parasitic bee mite Varroa jacobsoni Oud. Denis Anderson To cite this version: Denis Anderson. Variation in the parasitic bee mite Varroa jacobsoni Oud.. Apidologie, Springer Verlag, 2000, 31 (2), pp.281-292. 10.1051/apido:2000122. hal-00891709 HAL Id: hal-00891709 https://hal.archives-ouvertes.fr/hal-00891709 Submitted on 1 Jan 2000 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Apidologie 31 (2000) 281–292 281 © INRA/DIB-AGIB/EDP Sciences Review article Variation in the parasitic bee mite Varroa jacobsoni Oud. Denis L. ANDERSON CSIRO Entomology, G.P.O. Box 1700, Canberra, ACT 2601, Australia (Invited paper) Abstract – Initial searches found little evidence of genotypic or phenotypic variance in the parasitic bee mite Varroa jacobsoni, despite numerous reports of significant variation in the mite’s repro- ductive behaviour on its adopted host Apis mellifera. However, in a recent search that employed DNA sequencing techniques and large numbers of V. jacobsoni collected from the mites’ native host A. cerana throughout Asia, a remarkable amount of genetic variation was observed. Subse- quent analysis of this variation, coupled with follow-up morphological and ecology-based studies, showed that V. jacobsoni was a species complex. Other work carried out as part of that study also showed that only two out of 18 genetically different mites within the complex have switched host to A. mellifera and become a pest of this bee worldwide. These two mites are not V. jacobsoni as has been assumed, but they belong to a group of mites that naturally infest specific populations of A. cerana on mainland Asia. These mites will soon be renamed as a new species. This and other reports of variation in V. jacobsoni are reviewed and discussed. Varroa jacobsoni / morphological variation / reproductive variation / genetic variation / Apis mellifera / A. cerana 1. INTRODUCTION researchers when it shifted host to the West- ern honey bee, A. mellifera Linnaeus, fol- The mesostigmatid mite, Varroa jacob- lowing that bee’s introduction to Asia by soni Oudemans, was first described as an man [11, 45]. This opportunistic host-shift ectoparasite of the Eastern honey bee, Apis led to the mite spreading from Asia to cerana Fabricius in Java in 1904 [38], become an almost cosmopolitan pest of although it was subsequently found to par- A. mellifera, although it has not yet been asitise A. cerana throughout Asia [28]. The reported in Australia, New Zealand, Hawaii mite later came to the attention of bee and parts of Africa [13, 34]. * Correspondence and reprints E-mail: [email protected] 282 D.L. Anderson Details of how V. jacobsoni shifted from different populations of the mite’s native A. cerana to A. mellifera are not clear. Some host A. cerana in Asia, that the true extent of authors [36, 37] have proposed that the shift genetic variation in V. jacobsoni has been occurred when A. mellifera colonies were exposed [5, 6]. transported to Eastern Russia in the first half In the remainder of this paper, I will first of this century. This could have allowed briefly review the early studies on morpho- A. mellifera to come into contact with Var- logical variation in V. jacobsoni before also roa-infested A. cerana, which, until then, examining studies reporting on variation in had been speciating allopatrically. Regard- the reproduction of V. jacobsoni on A. mel- less of how the shift occurred, however, it is lifera. Next, I shall review in some detail now generally assumed that Varroa mites the results of a recent search for genetic vari- that were natural parasites of mainland Asian ation among V. jacobsoni infesting A. cer- populations of A. cerana were the first to ana throughout Asia and A. mellifera come into contact with A. mellifera. This worldwide. I will conclude this paper by presumption is supported by early reports discussing the ramifications that the recent of V. jacobsoni infesting A. mellifera, and findings on genetic variation in V. jacob- from early records of V. jacobsoni speci- soni have for future research directions and mens in the Acarological Collection at Ore- for efforts to find alternative control meth- gon State University, Corvallis, OR, USA, ods for those Varroa that cause so much that were collected from A. mellifera in damage to A. mellifera worldwide. China [1]. Following the shift of V. jacobsoni to A. mellifera, significant efforts were directed 2. MORPHOLOGICAL VARIATION at developing appropriate control methods IN VARROA JACOBSONI for the mite [40, 41], at understanding the mites’ life-cycle and behaviour [8, 23] and An initial search for morphological vari- with developing simulations of V. jacob- ation in V. jacobsoni revealed only limited soni population dynamics [9, 33]. Very lit- phenotypic differences between female tle attention was initially paid to variation in V. jacobsoni collected from A. mellifera in V. jacobsoni. It was not until the 1980s that the USSR, Japan and Germany [25]. Sub- some studies were directed at morphologi- sequent searches among large numbers of cal variation among V. jacobsoni popula- mites collected from widespread colonies tions [21, 22, 25]. Searches for genetic vari- of A. cerana and A. mellifera also showed a ation soon followed [7, 14, 16, 27, 30], lack of variation in phenotypic characters following numerous reports of significant among female V. jacobsoni, except in their reproductive variation among different mite body size [21, 22]. The genetic identity of populations infesting A. mellifera [2−4, 10, the mites used in those studies was not cer- 17, 18, 20, 35, 42, 43, 46]. tain. Initial searches for genetic variation in Nevertheless, the results clearly demon- V. jacobsoni showed only limited differ- strated that female mites infesting A. cer- ences among populations. However, it is ana were significantly smaller than those now clear that too few mite populations were infesting A. mellifera, even though there included in those searches, and that they was some overlap in the body size of mites were mostly directed at V. jacobsoni infest- from the two populations. Without a genetic ing A. mellifera, on which the mite had only basis, mites in the two groups were regarded been co-existing for a short time. It has only as distinct ‘biotypes’. It is now clear that been in a recent search, which incorporated the mites used in those studies belonged to large numbers of V. jacobsoni collected from quite different genetic groups. A recent study Variation in the bee mite Varroa jacobsoni 283 [6] that re-examined the body sizes of par- DNA (RAPD) technique. It indicated that ticular genotypes of V. jacobsoni on A. cer- V. jacobsoni infesting A. cerana in ana is discussed later in this paper. Malaysian Borneo were genetically distinct from V. jacobsoni infesting A. mellifera in the US and Germany [30]. Another study 3. REPRODUCTIVE VARIATION [4], which compared mitochondrial DNA IN V. JACOBSONI INFESTING (mtDNA) gene sequences, also showed that A. MELLIFERA V. jacobsoni from A. cerana colonies of Javanese origin, which also lacked the abil- Even though female V. jacobsoni from ity to reproduce on A. mellifera, were genet- widespread populations show great consis- ically distinct from V. jacobsoni that were tency in the way they reproduce on their infesting and reproducing in A. mellifera native host A. cerana by reproducing solely colonies in Germany. on drone (male) brood and hence causing minimal harm to colonies [28, 29, 39], their An extensive search for genetic variation reproduction on their adopted host A. mel- among V. jacobsoni infesting A. cerana has lifera is not as uniform. Generally, in only recently been completed [5, 6]. The Europe, the Middle East, Asia and parts of level of variation detected was astonishing the Americas, female V. jacobsoni readily and, as these results will radically change reproduce on both the drone and worker the way Varroa is viewed in the future, they brood of A. mellifera, and most bee colonies will now be elaborated on in some detail. do not survive mite infestations unless effec- The study compared mitochondrial DNA tive mite control methods are implemented (mtDNA) cytochrome oxidase I (CO-I) cod- [19, 32]. However, in tropical and subtrop- ing gene sequences obtained from adult ical America where A. mellifera shows a female V. jacobsoni collected from popu- tolerance to V. jacobsoni [17, 18, 20, 26, lations of A. cerana distributed throughout 31, 35, 42, 44, 46], fewer female V. jacob- Asia. Similar DNA sequences obtained from soni reproduce on A. mellifera than is V. rindereri De Guzman and Delfinado and observed in Europe and the Middle East [42, from V. underwoodi Delfinado-Baker and 46], and mite offspring mortality rates are Aggarwal were also used in the study as a higher than in the UK [31]. The greatest gauge of genetic distances between species. variation in V. jacobsoni reproduction on In all, 18 genetically distinct types of mites A. mellifera, however, has been reported for (called haplotypes) were found. Each was female V. jacobsoni of Javanese origin; these assigned a name from the country or island are mites from which the species V. jacob- in which it was discovered. For example, a soni was first described in 1904. These mites ‘Korea haplotype’ was found on A. cerana fail to produce eggs or offspring when they in Korea, while a ‘Java haplotype’ was enter A.