Propagule pressure rather than population growth determines colonisation ability: a case study using two phytophagous mite species differing in their invasive potential

Abstract

1. Colonisation, i.e. the establishment of dispersed individuals in an unoccupied area, is a fundamental biological process that drives the distribution and range dynamics of organisms. It is crucial to understand the basic mechanisms of colonisation, especially in invasive species.2. In this study, we investigated the importance of dispersal success (the proportion of settlers and founders) and intrinsic population growth rate for colonisation ability in phytophagous mites that spread both passively and actively. We performed laboratory experiments using two eriophyid mite species: Aceria tosichella [wheat curl mite (WCM)] and Abacarus hystrix [cereal rust mite (CRM)]. These are obligate herbivores of economic importance because they feed on cereal plants, including wheat.3. To test the colonisation ability of WCM and CRM on wheat when dispersed actively by walking and passively when blown by air currents, we estimated the number of individuals that established new populations after dispersal and calculated the intrinsic population growth rate (r) for both species.4. WCM had a higher colonisation ability on wheat than CRM. This resulted from the higher dispersal success of WCM; however, the two species did not differ in r. This pattern was consistent for both dispersal modes. Moreover, both species had higher colonisation success when dispersing actively, albeit with a very limited spatial range.5. These results underline the role of successful dispersal in the colonisation ability of species. The knowledge of the colonisation process of WCM and CRM is important for understanding their invasiveness and for predicting their potential geographical distributions.

Hitchhiking or hang gliding? Dispersal strategies of two cereal-feeding eriophyoid mite species

“…The two eriophyoid species studied significantly differed in their aerial dispersal success; WCM dispersed more effectively than CRM. Majer et al (2021a) also demonstrated that aerially transferred WCM have a higher colonisation ability than CRM. WCM also showed increased behavioural activity via wind, whereas the activity of CRM decreases in such conditions (Kiedrowicz et al 2017).…”

“…To calculate the model parameters, we used a Bayesian hierarchical modelling approach, as described in Kuczyński et al (2020) and modified in Majer et al (2021a). Dispersal success (d) of WCM and CRM using different dispersal modes was estimated independently.…”

“…At the other end of the tunnel, target plants were placed on a metal grille in an elbow connector and were protected within a polyamide funnel to prevent contamination during the experiments (Fig. 1A) (for details see Kuczyński et al 2020;Majer et al 2021a). The experiment was replicated 10× for each species, and trials for each species were run separately, but under similar room conditions (Majer et al 2021b).…”

“…Thus, there is a huge demand for empirical data on their dispersal abilities that would enable predictions of future expansion of harmful species. There is some evidence that eriophyoid mites can disperse actively for short distances, i.e., by walking within or between plants (Michalska et al 2010;Galvão et al 2012;Melo et al 2014;Majer et al 2021a). However, this mode of dispersal is extremely limited due to their minute size (length ca.…”

“…Here, we fill this gap and assess the dispersal success of WCM and CRM using wind and phoretic vectors. We investigated aerial dispersal in wind tunnels (Majer et al 2021a). To test phoretic dispersal, we used Anaphothrips obscurus Müller (Insecta: Thysanoptera) and a robot constructed from Lego Mindstorm kits (a device built according to Kuczyński et al 2020), as potential small and large vectors, respectively.…”