Clustered or scattered? The impact of habitat quality clustering on establishment and early spread

Abstract

The match between the environmental conditions of an introduction area and the preferences of an introduced species is the first prerequisite for establishment. Yet, introduction areas are usually landscapes, i.e. heterogeneous sets of habitats that are more or less favourable to the introduced species. Because individuals are able to disperse after their introduction, the quality of the habitat surrounding the introduction site is as critical to the persistence of introduced populations as the quality of the introduction site itself. Moreover, demographic mechanisms such as Allee effects or dispersal mortality can hamper dispersal and affect spread across the landscape, in interaction with the spatial distribution of favourable habitat patches. In this study, we investigate the impact of the spatial distribution of heterogeneous quality habitats on establishment and early spread. First, we simulated introductions in one‐dimensional landscapes for different dispersal rates and either dispersal mortality or Allee effects. The landscapes differed by the distribution of favourable and less favourable habitats, which were either clustered into few large aggregates of the same quality or scattered into multiple smaller ones. Second, we tested the predictions of simulations by performing experimental introductions of hymenopteran parasitoids (Trichogramma chilonis) in ‘clustered’ and ‘scattered’ microcosm landscapes. Results highlighted two impacts of the clustering of favourable habitat: by decreasing the risks of dispersal from the introduction site to unfavourable habitat early during the invasion, it increased establishment success. However, by increasing the distance between favourable habitat patches, it also hindered the subsequent spread of introduced species over larger areas.

Colonisation debt: when invasion history impacts current range expansion

“…As dispersal was stochastic, so were these stops and their duration, generating additional variability in the overall invasion speed. This is consistent with modeling studies using binary landscapes rather than gradients, which showed that a larger non-habitat gap was more likely to alter the spread of density-dependent invaders (Dewhirst and Lutscher, 2009, Morel-Journel et al, 2018). Although this was not tested for this study, experimental invasion fronts have proved to be inherently stochastic and hardly predictable (Melbourne and Hastings, 2009).…”

Spatial–temporal evolution and correlation analysis between habitat quality and landscape patterns based on land use change in Shaanxi Province, China

“…Different from other studies on the continuous decrease of habitat quality with the rapid advancement of urbanization (Morel‐Journel et al., 2018 ), the overall trend of habitat quality in Shaanxi Province was first rising and then stable. On the one hand, the higher and high habitat quality areas increased, which was consistent with the increase in forest land and grassland and the decrease in arable land.…”

Colonisation debt: when invasion history impacts current range expansion

“…As dispersal was stochastic, so were these stops and their duration, generating additional variability in the overall invasion speed. This is consistent with modelling studies using binary landscapes rather than gradients, which showed that a larger non-habitat gap was more likely to alter the spread of density-dependent invaders (Dewhirst and Lutscher, 2009;Morel-Journel et al, 2018). Although this was not tested for this study, experimental invasion fronts have proved to be inherently stochastic and hardly predictable Peer Community Journal, Vol.…”