Modeling competition, niche, and coexistence between an invasive and a native species in a two‐species metapopulation

Abstract

Modeling the dynamics of competition and coexistence between species is crucial to predict long‐term impacts of invasive species on their native congeners. However, natural environments are often fragmented and variable in time and space. In such contexts, regional coexistence depends on complex interactions between competition, niche differentiation and stochastic colonization–extinction dynamics. Quantifying all these processes at landscape scale has always been a challenge for ecologists. We propose a new statistical framework to evaluate metapopulation parameters (colonization and extinction) in a two‐species system and how they respond to environmental variables and interspecific competition. It requires spatial surveys repeated in time, but does not assume demographic equilibrium. We apply this model to a long‐term survey of two snails inhabiting a network of freshwater habitats in the West Indies. We find evidence of reciprocal competition affecting colonization or extinction rates, modulated by species‐specific sensitivity to environmental variables. Simulations using model estimates allow us to predict species dynamics and explore the role of various coexistence mechanisms described by metacommunity theory in our system. The two species are predicted to stably coexist, because niche partitioning, source–sink dynamics and interspecific differences in extinction–colonization parameters all contribute to reduce the negative impacts of competition. However, none of these mechanisms is individually essential. Regional coexistence is primarily facilitated by transient co‐occurrence of the two species within habitat patches, a possibility generally not considered in theoretical metacommunity models. Our framework is general and could be extended to guilds of several competing species.

Host‐plant availability drives the spatiotemporal dynamics of interacting metapopulations across a fragmented landscape

“…Thus, the observed reciprocal positive effects of these two species on each other's probability of colonization are again hard to explain as the outcome of positive interspecific interactions. If competitive interactions are important, we would expect negative effects of competitor occurrence on colonization and/or persistence, as observed by Dubart et al (2019) for competing snail species. Both the mildew and butterfly larvae tend to cluster spatially within the host plant populations Laine 2006, Salgado et al 2020) and field observations suggest that they tend to occupy different parts of shared patches, which perhaps reduces any negative interaction between them.…”

“…Time‐series data on potentially interacting species collected from multiple sites can be used to assess how both spatial and temporal dynamics of species depend on the presence of potentially interacting species (Yackulic et al 2014, Rota et al 2016, Davis et al 2017, Ovaskainen et al 2017 a , Dubart et al 2019, Fidino et al 2019). For example, in their long‐term study of a native and an invasive snail occupying a network of several hundred ponds in the West Indies, Dubart et al (2019) detected strong effects of patch occupancy by the potential competitor on colonization rates, suggesting reciprocal competitive effects. Analyses of time‐series data have also provided insights into interactions between native and invasive bird species (Yackulic et al 2014), fish and amphibians in wetlands (Davis et al 2017), and mammals in urban environments (Fidino et al 2019).…”

Species coexistence and overlapping distributions in a metacommunity are compatible with niche differences and competition at a local scale

“…In order to estimate Daphnia metapopulation dynamics, we used a state-space modeling approach (MacKenzie et al 2003, Royle andKéry 2007) based on one developed by Dubart et al (2019), which models colonization and extinction rates as a function of the environment and the presence of other species, while accounting for imperfect species detection. This model allowed us to consider colonization rate as dependent on overall metapopulation occupancy, as in Levins' metapopulation model (Levins 1969).…”

“…This study extends the approach of Dubart et al (2019), who used multispecies metapopulation models to estimate colonization and extinctions rates based on environmental conditions and the presence of other species, while also accounting for imperfect species detection probabilities and non-equilibrium situations. Here, we extend this approach by including space explicitly and reformulating the initial model as a continuous time version, so that it applies to a wider range of real metacommunities.…”

Malacological survey in a bottle of water: A comparative study between manual sampling and environmental DNA metabarcoding approaches

“…Cryptic freshwater mollusc species are particularly difficult to detect and previous studies 340 estimated that about 20% of the species present at a single site are undetected after a single 341 prospecting session during malacological surveys (Dubart et al, 2019). Moreover, detecting 342 biases are also common in malacology because populations of snails are highly dynamic in 343 space and time (Lamy et al, 2012).…”