Abstract
Simple SummaryThe onion thrips (Thrips tabaci), which is a key pest worldwide, includes three characteristic, distinct groups (i.e., lineages) under the same species name. In the current report, we addressed the question of whether individuals from these lineages recognize and assess each other as potential mating partners. We demonstrated that at least two of these lineages do not belong to the same species, since under our laboratory conditions no mating occurred between them. Moreover, specimens from these cross pairings often exhibited an escape response upon contact with the other thrips, while most of the pairs from the same lineages readily mated at their first interaction. The behaviour of males clearly indicated that they can assess the mating status of a female and usually only try to copulate with virgins. Our findings are important not only because in agriculture it is vital to know whether morphologically similar entities belong to the same species, but also because knowledge about the communication of insects and the possible role of the cues involved can help the development of new plant protection techniques.Thrips tabaci Lindeman is a serious pest of various cultivated plants, with three, distinct lineages within a cryptic species complex. Despite the well-known significance of this pest, many attributes of these lineages are not yet fully understood, including their reproductive behaviour. We performed no-choice-design cross-mating experiments under a controlled laboratory environment with virgin adult individuals from all three lineages. The behaviour of thrips was recorded with a camera mounted on a stereomicroscope, and the recordings were analysed in detail. We found that the so-called leek-associated lineages of this cryptic species complex are reproductively isolated from the tobacco-associated lineage; therefore, they represent different species. Divergence in the behaviour of conspecific and heterospecific pairs became evident only after contact. There were no marked differences between the lineages in their precopulatory and copulatory behaviour, except in the duration of the latter. We confirmed mating between thelytokous females and arrhenotokous males; however, we assume some form of loss of function in the sexual traits of asexual females. The post-mating behaviour of males indicated the presence and role of an anti-aphrodisiac pheromone. We also demonstrated differences between lineages regarding their activity and their propensity for exhibiting an escape response upon interaction with heterospecific thrips.
Highlights
Cryptic species are usually defined as two or more species that are classified as a single nominal species, based on their morphological similarity [1]
We demonstrated that mating occurs between specimens from the same lineage under laboratory conditions; the lack of copulation in other treatments indicates reproductive isolation, which means that the two arrhenotokous lineages of onion thrips should be considered as distinct species
The formation of a so-called “V-position” by the copulating male and female seems to be common [41,45], while in the onion thrips cryptic species complex, we found that this position is not characteristic, and even if it happens, it seemed that it was not intentional, rather it happened by accident
Summary
Cryptic species are usually defined as two or more species that are (or were in the past) classified as a single nominal species, based on their morphological similarity [1]. Research on cryptic species complexes is crucial for the investigation of biological diversity and for conservation purposes [1,4], but clearly such studies on arthropods could be highly relevant to agriculture and plant protection. For example, that cryptic pest species could have important differences in their host range, as is seen in Dasineura oxycoccana Johnson (Diptera: Cecidomyiidae) [6], or in Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) [7]. The identification of morphologically similar species with differences in their host range could necessitate the reconsideration of quarantine actions against pests [8]. Detailed knowledge of the host adaptation of natural enemies in cryptic species complexes is vital for choosing the proper biocontrol agent in agriculture [9,10]. Cryptic species in allopatry could represent different biological species, despite their seemingly identical host range and pest status [11]. Within a complex of cryptic pest species, an invasive species can displace the indigenous species [12,13], raising the question of whether such species displacement, which could happen undetected, could change the pest status of the insect populations present in a region
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