Differential Host Plant-Associated Genetic Variation Between Sympatric Mite Species of the GenusOligonychus(Acari: Tetranychidae)

Abstract

Adaptation to different host plants can lead to host-associated differentiation (HAD). The mites Oligonychus perseae and Oligonychus punicae have a broad range of host plants, but, to date, records of them coexisting sympatrically had only been reported on avocado. However, our field observations showed both species coexisting on host plants other than avocado. The lack of previous records of these mites on the host plants studied here suggests only recent divergence to new host plant species. Previous studies showed that O. punicae had a limited migration capacity compared with O. perseae, suggesting that O. punicae is more likely to develop a close host plant relationship leading to HAD. Adults of both species were collected from trees hosting both mite species. Three genera of host plants considered were Persea, Salix, and Alnus; two species within one genus were Alnus jorullensis and Alnus acuminata; and three varieties within one species were Persea americana var. Fuerte, var. Hass, and var. Criollo, a noncommercial variety. Using sequence data from a segment of the mitochondrial cytochrome oxidase subunit I, the phylogenetic relationships and genetic population structure of both mite species in relation to the host plant were determined. Oligonychus perseae populations showed a significant population structure in relation to host plant at the species and genus level, but there was no effect of variety. In contrast, host plant explained none of the genetic variation among O. punicae populations. The potential role of coexistence mechanisms in the contrasting genetic population structure of both mite species is discussed.

Population Genetics ofOligonychus perseae(Acari: Tetranychidae) Collected from Avocados in Mexico and California

“…However, examination of their sequences (GenBank accessions KX072889-921; Guzmán-Valencia et al 2017) reveals levels of divergence between the COI of their avocado populations and those they sampled from the 2 Alnus species, similar to those reported herein (~8%), suggesting that they may also have encountered 2 cryptic species (in their case, on 2 different types of host plant). Unfortunately, the regions of COI used in our study and that of Guzmán-Valencia et al (2017) do not overlap, and additional genetic marker sequences are not available from Guzmán-Valencia et al (2017). Thus, it is uncertain whether or not there is overlap in the potential cryptic species reported in the 2 studies.…”

“…Although we have strong molecular evidence for O. perseae being a complex of 3 cryptic species, biological (e.g., interpopulation mating studies) and ecological data (these putative cryptic species occupy near identical niches and cause very similar feeding damage) to sup-port their status is currently lacking, and we strongly recommend these as future lines of research. Interestingly, Guzmán-Valencia et al (2017) recently assessed genetic variation among sympatric O. perseae and O. punicae populations on 6 perennial host trees in the state of México, which included the hardwood species Salix bonplandiana Kunth (Salicaceae), Alnus jorullensis Kunth (Betulaceae), and Alnus acuminata Kunth (Betulaceae), alongside 3 avocado cultivars ('Hass', 'Fuerte', and 'Criollo'). As it relates to our study on avocado, Guzmán-Valencia et al (2017) found no genetic variation among the COI sequences of morphologically-identified O. perseae populations sampled from the 3 avocado cultivars.…”

“…Interestingly, Guzmán-Valencia et al (2017) recently assessed genetic variation among sympatric O. perseae and O. punicae populations on 6 perennial host trees in the state of México, which included the hardwood species Salix bonplandiana Kunth (Salicaceae), Alnus jorullensis Kunth (Betulaceae), and Alnus acuminata Kunth (Betulaceae), alongside 3 avocado cultivars ('Hass', 'Fuerte', and 'Criollo'). As it relates to our study on avocado, Guzmán-Valencia et al (2017) found no genetic variation among the COI sequences of morphologically-identified O. perseae populations sampled from the 3 avocado cultivars. However, examination of their sequences (GenBank accessions KX072889-921; Guzmán-Valencia et al 2017) reveals levels of divergence between the COI of their avocado populations and those they sampled from the 2 Alnus species, similar to those reported herein (~8%), suggesting that they may also have encountered 2 cryptic species (in their case, on 2 different types of host plant).…”