Acaricide-Mediated Competition Between the Sibling Species Tetranychus cinnabarinus and Tetranychus urticae

Abstract

The carmine spider mite (Tetranychus cinnabarinus [Acarifonnes: Tetranychidae]) and the two-spotted spider mite (Tetranychus urticae [Acarifonnes: Tetranychidae]) are two notorious pests of agricultural crops. Control of these pests has been dependent upon using different kinds of acaricides. The purpose of this study was to determine the differential responses of these two pest species collected from crops in the same field to acaricide treatments. Field trials have shown that without spraying acaricides, T. cinnabarinus will displace T. urticae. However, the application of abamectin has the potential to change the composition of spider mite complexes and facilitate the interspecific competition of T. urticae against T. cinnabarinus when both are fed on cowpeas and eggplants. Moreover, T. urticae is more prone to develop resistance than T. cinnabarinus when selected in the laboratory using cyflumetofen or fenpropathrin. After 20 generations of acaricide selection, the activities of detoxifying enzymes were considerably higher in T. urticae with more detoxifying enzymes upregulated after selection in this species. The results of this study demonstrate that differential responses to acaricide treatments have made it possible for T. urticae to overcome the competitive advantage present in T. cinnabarinus during the absence of acaricide application.

Competition for food affects the strength of reproductive interference and its consequences for species coexistence

“…Here, in absence of competition for food, we found asymmetric reproductive interference between T. cinnabarinus and T. urticae -, a result that is congruent with previous findings on pre- and post-mating reproductive isolation between the two populations used in this study 50,54 . This is also compatible with earlier studies using Chinese populations of these species, in which T. cinnabarinus consistently displaces T. urticae when at an even initial frequency 41,47 . However, these studies also revealed that this outcome is reversed in the presence of pesticides, due to stronger pesticide resistance in T. urticae .…”

“…Therefore, designing experiments that measure the impact of each of these interactions separately (which is needed as a control to evaluate their joint effect) is a true challenge. Herbivorous spider mites represent an ideal system to do so, given their amenability to experimental manipulation of both competition for food [39][40][41] and reproduction (incl. reproductive interference 42,43 ).…”

“…Here, we studied the single and combined effects of reproductive interference and competition for food between two sibling species of spider mites, Tetranychus urticae and T. cinnabarinus 44 (also often referred to as the green and red forms of T. urticae 45 ). These two species have overlapping distributions and host plant ranges 46 , compete for food 41,47 , and suffer from strong reproductive interference 43 due to variable reproductive incompatibilities and unfit hybridization (ranging from partial to complete hybrid sterility and hybrid breakdown [48][49][50] ). With this experimental system, we used recent modelling advances rooted in coexistence theory 27 and its recent extensions accounting for priority effects 51 , and performed a set of experiments manipulating the presence or absence of food competition and reproductive interference.…”

Wolbachiastrengthens the match between pre-mating and early post-mating isolation in spider mites

“…Finally, building upon the recent idea that partial reproductive isolation may be an adaptive optimum (Servedio and Hermisson 2020), we considered the possibility that heterotypic mating preference might be selected for under reproductive interference (Gröning and Hochkirch 2008), as the two colour forms have overlapping distribution and host plant range (Migeon and Dorkeld 2023), and often co-occur on the same individual host plant (Lu et al 2017(Lu et al , 2018Zélé et al 2018b). Although most conditions that have been theoretically considered to promote the evolution of 'disassortative mating', such as a heterozygote advantage (e.g., Maisonneuve et al 2021), are not met in our system (hybrids are sterile or suffer breakdown; Cruz et al 2021), heterotypic mating preference may still confer higher benefits than costs to the green-form population in the presence of red-form competitors.…”

“…To improve our understanding of the role that Wolbachia can play in ongoing speciation processes of its hosts, we aimed at disentangling the relative contributions of Wolbachia and host genetic factors to the strength of both pre-and post-mating pre-zygotic barriers between two colour forms, green and red, of the two spotted spider mite T. urticae (sometimes also referred to as T. urticae and T. cinnabarinus; Xie et al 2006;Auger et al 2013;Lu et al 2017Lu et al , 2018. A previous study focusing on the joint effects of Wolbachia-induced and host-associated post-mating incompatibilities between populations of these two forms revealed full reproductive isolation due to late post-zygotic barriers (hybrid sterility and hybrid breakdown) that were independent of Wolbachia infection (Cruz et al 2021).…”