Spatial heterogeneity in invasive species impacts at the landscape scale

Invasive species can alter the structure and function of the communities they invade, as well as lead to biotic homogenization across their invasive range, thus affecting large‐scale diversity patterns. The mechanisms by which invasive species can lead to biotic homogenization are poorly understood. We argue that invasive species acting as strong, deterministic, and consistent filters within and across invaded communities are likely to cause biotic homogenization at multiple spatial scales. We studied Bromus inermis Leyss. invasion into eight grasslands covering most of the grassland and parkland natural regions of Alberta (western Canada). Specifically, we tested whether B. inermis (1) has a strong impact on species richness and composition, (2) consistently alters resources (nutrients, light, and soil moisture), imposing the same ecological filter to species establishment and persistence across sites, and hence (3) whether it leads to biotic homogenization within and across sites. We recorded plant cover and resources across native‐to‐invaded transition areas combining space‐for‐time substitutions with time‐series data analyses. Bromus inermis invasion was associated with rapid biotic homogenization of communities, within and among the eight grasslands. The sharp changes in species relative abundances following invasion was the initial driver of biotic homogenization, and species loss was delayed. Supporting the idea that biotic homogenization can occur when an invasive species presents a broad and consistent filter, resources modified by B. inermis invasion (particularly light and certain nutrients) were altered rather consistently within and across sites. The 50% reduction in light was likely the initial driver of biotic homogenization, and the increase in nutrient availability probably facilitates the displacement of species from the invaded areas and could lead to the establishment of self‐reinforcing dynamics. Overall, our results support the idea that invaders acting as strong, deterministic, and consistent ecological filters are likely to cause biotic homogenization of the communities they invade.

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“…, Latzka et al. ), but also in terms of the mechanisms behind the species impact, depending on local conditions (Ehrenfeld , Lankau et al. ).…”

Section: Introductionmentioning

confidence: 99%

Biotic homogenization within and across eight widely distributed grasslands following invasion by Bromus inermis

Stotz

Gianoli

Cahill

2019

Ecology

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“…Consequently, food web and whole‐ecosystem effects need to be considered when removing an invasive species (Hansen, Hein, et al, 2013; Zavaleta, Hobbs, & Mooney, 2001). To make things even more complex, invasive species abundance (Hansen, Vander Zanden, et al., ) and their impacts vary across habitats (Latzka, Hansen, Kornis, & Vander Zanden, ) and time‐scales (Crooks, ). These system‐specific differences underscore the need for basic ecological knowledge combined with local decision makers’ priorities to create evidence‐based control options.…”

Section: Discussionmentioning

confidence: 99%

A dynamical model for invasive round goby populations reveals efficient and effective management options

N’Guyen

Hirsch

Bozzuto³

et al. 2017

Journal of Applied Ecology

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Abstract1. When prevention of invasive species' introductions fails, society faces the challenge to manage invasive species in an effective and efficient way. The success of this depends on biological aspects and on cooperation between decision makers and scientists.Using the case of the round goby Neogobius melanostomus, one of Europe's "worst invasive species", we propose an approach guiding scientists to co-produce effective and efficient population control measures in collaboration with decision makers.2. We surveyed the effectiveness, urgency and simplicity perceived by decision makers as well as the support of two population control options: removal of eggs and/ or adults. Using a field study and a dynamical population model, we investigated the effectiveness and efficiency for both options in different population contexts.3. Decision makers initially seemed to lack a clear preference for either control option.After being presented with preliminary field and modelling results, decision makers mostly approved measures being developed to implement the two control options.4. Starting population control early after detecting the species requires in total fewer years for eradication than controlling an established population: to reach an eradication success rate of 95%, 13 years for early start vs. 18 years for late start are needed when removing eggs and adults; when removing adults only, 20 vs. 29 years are needed. Removing eggs and adults combined results in a yearly effort of 5.01 h/m 2 , while removing adults only results in a yearly effort of 1.76 h/m 2 . Thus, removing adults only proves to be the most efficient option to eradicate the population. Nonetheless, considerable effort is needed: when removing less than 57% of the adult population, eradication is not feasible, even assuming low survival and fecundity rates for the population. Furthermore, inflow of new propagules renders eradication efforts ineffective. Synthesis and applications.Scientists who aim to support decision makers in finding an optimal control strategy for invasive species need to be able to provide scientific knowledge on effectiveness and efficiency of different options. For round goby and most non-native species, eradication is only feasible if started early in recently arrived populations and if inflow of new propagules can be prevented.

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“…The intensity and outcome of aggression between invasive and native species is frequently context dependent (Hudina, Zganec, & Hock, ; Jackson, Ruiz‐Navarro, & Britton, ; Kaiser et al, ). The abundance of many invaders can be temporally and spatially heterogeneous, which in turn suggests that the intensity of their aggressive interactions with natives may be similarly variable (Latzka, Hansen, Kornis, & Vander Zanden, ). Aggressive interactions have typically been thought to increase with the population density of an invader due to a higher rate of contact with native competitors as well as a reduction in resources relative to population size (Kaiser et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…For example, both the coral dwelling bridled goby ( Coryphopterus glaucofraneum ) and goldspot goby ( Gnatholepis thompsoni ) were reported to be at least twice as aggressive towards conspecifics than towards heterospecifics (Forrester et al, ). However, support for this prediction is overwhelmingly provided by studies of species in their natural ranges (Connell, ; Goldberg & Barton, ; Mangla, Sheley, James, & Radosevich, ), neglecting the possibility that the behaviour of invasive species which are by definition outside of their native ranges may be inherently different to that of native species (Hansen et al, ; Latzka et al, ). For example, Argentine ant ( Linepithema humile ) populations are known to display reduced intra‐specific aggression between nests outside compared to within their native ranges (Tsutsui, Suarez, Holway, & Case, ).…”

Section: Introductionmentioning

confidence: 99%

The effect of density on aggression between a highly invasive and native fish

2019

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Population densities of invasive species fluctuate spatially and temporally, suggesting that the intensity of their aggressive interactions with native species is similarly variable. Although inter‐specific aggression is often thought to increase with population density, it is often theorized that it should be exceeded by intra‐specific aggression since conspecifics share a greater degree of resource overlap. Yet, the magnitude of intra‐specific aggression is seldom considered when examining aggressive interactions, particularly those between invasive and native species. Here, we manipulated the density of the invasive eastern mosquitofish, Gambusia holbrooki, and observed its aggressive interactions with juveniles of the native Australian bass, Macquaria novemaculeata in a laboratory setting. For both species, the magnitudes of intra‐ and inter‐specific aggression were recorded. Regardless of density, the native M. novemaculeata was more aggressive towards heterospecifics than G. holbrooki was. In addition to this, M. novemaculeata was more aggressive to G. holbrooki than towards conspecifics, at both low‐ and high‐density conditions. In contrast, G. holbrooki was similarly aggressive towards M. novemaculeata and G. holbrooki at a high density, yet at low density, displayed significantly more aggression towards conspecifics than M. novemaculeata. These findings demonstrate the importance of considering intra‐specific aggression when exploring behavioural interactions between native and invasive species.

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Spatial heterogeneity in invasive species impacts at the landscape scale

Cited by 30 publications

References 44 publications

Biotic homogenization within and across eight widely distributed grasslands following invasion by Bromus inermis

Biotic homogenization within and across eight widely distributed grasslands following invasion by Bromus inermis

A dynamical model for invasive round goby populations reveals efficient and effective management options

The effect of density on aggression between a highly invasive and native fish

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