Coexistence between native and exotic species is facilitated by asymmetries in competitive ability and susceptibility to herbivores

Heard, Matthew J.; Sax, Dov F.

doi:10.1111/ele.12030

Cited by 73 publications

(76 citation statements)

References 48 publications

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“…A failure of competition to exclude native species at regional or global scales could arise because introduced plants deplete the resources they initially thrive on and accumulate herbivores and diseases, which together apply density-dependent control to introduced species before they can exclude the native plants. In addition, native plants may have the capacity to out-compete or coexist with the invaders, at least in some local environments (29)(30)(31)(32)(33).…”

mentioning

confidence: 99%

Non-native plants add to the British flora without negative consequences for native diversity

Thomas

Palmer

2015

Proc. Natl. Acad. Sci. U.S.A.

104

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Plants are commonly listed as invasive species, presuming that they cause harm at both global and regional scales. Approximately 40% of all species listed as invasive within Britain are plants. However, invasive plants are rarely linked to the national or global extinction of native plant species. The possible explanation is that competitive exclusion takes place slowly and that invasive plants will eventually eliminate native species (the "time-to-exclusion hypothesis"). Using the extensive British Countryside Survey Data, we find that changes to plant occurrence and cover between 1990 and 2007 at 479 British sites do not differ between native and non-native plant species. More than 80% of the plant species that are widespread enough to be sampled are native species; hence, total cover changes have been dominated by native species (total cover increases by native species are more than nine times greater than those by non-native species). This implies that factors other than plant "invasions" are the key drivers of vegetation change. We also find that the diversity of native species is increasing in locations where the diversity of non-native species is increasing, suggesting that high diversities of native and non-native plant species are compatible with one another. We reject the time-toexclusion hypothesis as the reason why extinctions have not been observed and suggest that non-native plant species are not a threat to floral diversity in Britain. Further research is needed in island-like environments, but we question whether it is appropriate that more than three-quarters of taxa listed globally as invasive species are plants.invasive species | biodiversity | Anthropocene | ecology | botany T he Global Invasive Species Database (1) lists 3,163 plant (Plantae) and 820 animal (Animalia) species as invasive because they "threaten native biodiversity and natural ecosystems" in the regions to which they have been introduced. Given the relative numbers of animal and plant species that have been described (2-4), this implies that the per species likelihood of being listed as invasive is ∼25 times higher for plants than for animals. For the United Kingdom, 49 of 125 species (39%) categorized as invasive in the same database are plants (1), and a more detailed analysis included 102 plants in a list of 244 non-native species (∼42%, depending on taxonomic designations) that have negative ecological or human effects in Great Britain (5, 6). These numbers imply that non-native plants must be key threats to biodiversity both globally and in Britain. It is surprising, therefore, that examples of regional-scale or species-level extinctions associated with invasive plants are apparently rare (7-12).Most extinctions associated with introduced species have been caused by invasive predators and diseases encountering "naïve" prey and host species in distant and isolated parts of the world (13)(14)(15)(16)(17)(18)(19). Putative examples of competitive exclusion in the invasive species literature have usually turned out to be exam...

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confidence: 99%

Non-native plants add to the British flora without negative consequences for native diversity

Thomas

Palmer

2015

Proc. Natl. Acad. Sci. U.S.A.

104

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“…This, in conjunction with the fact that A. modestus has been present in Ireland since the 1950s (Beard 1957), indicates that this species is more likely to coexist with native barnacle species than to displace or outcompete them, at this location. While invasive species have the potential to outcompete native species, there have been many reports of native and invasive species coexisting (Buschbaum et al 2006;Briggs 2010;Davies et al 2011), even over long temporal scales (Heard and Sax 2013). Hui and Moyse (1987) noted that the native barnacle Semibalanus balanoides would continue to persist in the presence of A. modestus, provided that the alien species had not colonised all available space before S. balanoides spatfall.…”

Section: Discussionmentioning

confidence: 99%

Room for one more? Coexistence of native and non-indigenous barnacle species

et al. 2016

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Space can be a limiting factor in intertidal communities and competition for this resource plays a role in determining community composition. Invasive species are known to be opportunistic, and are capable of rapidly colonising free space. Since its introduction to Europe, over 70 years ago, the invasive barnacle species, Austrominius (=Elminius) modestus has become widespread on European coasts and is now the dominant barnacle species at numerous locations. However, little is known about its competitive interactions with native barnacle species. During this study, 18 removal plots (25 cm 2 ) were created at each of six sites in south-west Ireland, encompassing a range of exposure levels and including both artificial structures and natural rocky shores. Monthly monitoring of these plots over 19 months revealed that, despite high recruitment of native species seasonally, A. modestus ultimately outnumbered natives in removal plots at four sites. With the provision of free space, the invasive species increased its relative abundance at three sites, but did not entirely displace natives at any site. Continued recruitment of the native species at high abundances on a seasonal basis in addition to the invasive species not entirely colonising all available space, ensure native species can persist and co-exist with A. modestus at the majority of sites at this location.

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“…Understanding how invasive species physiologically affect native species could provide important insights into their applied ecology or conservation needs (Wikelski and Cooke 2006;Busch and Hayward 2009;Seebacher and Franklin 2012). With respect to competition between native species and introduced species, inference from GC responses could help indicate the degree of coexistence between introduced competitors and native competitors and hence help evaluate short-or long-term impacts of competition dynamics, a major area of conservation management prioritization and investment (Heard and Sax 2013). We demonstrated that the adrenocortical response of lace monitors was activated by a capture stress protocol as corticosterone synthesis significantly increased with time postcapture.…”

Section: Discussionmentioning

confidence: 99%

An Introduced Competitor Elevates Corticosterone Responses of a Native Lizard (Varanus varius)

Jessop¹,

Anson²,

Narayan³

et al. 2015

Physiological and Biochemical Zoology

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Glucocorticoid hormone profiles are increasingly used as physiological markers to infer the strength of species interactions that can influence fitness and ensuing population dynamics of animals. Here we investigated two aims. First, we measured the effect of a 90-min capture stress protocol on the plasma corticosterone responses of a large native Australian lizard, the lace monitor (Varanus varius). Second, we compared the basal and postcapture stress corticosterone responses of lace monitors in habitats where they were exposed to high or low densities of the European red fox (Vulpes vulpes), an introduced competitor. Lace monitors responded to the capture stress protocol by significantly increasing plasma levels of corticosterone above basal at 45- and 90-min-postcapture blood-sampling intervals. In habitats with high fox densities, lace monitors produced a significantly greater basal and capture-stress-induced corticosterone response compared to individuals in low-fox density habitat. A significant interaction among fox density, time postcapture, and body condition was also found to influence plasma corticosterone values. These results suggest competition with red fox, perhaps via nutritional stress and increased hypersensitivity of the adrenocortical axis in lizards. At present, without further research, we do not understand whether such responses mediate lizard fitness or whether they have adaptive or maladaptive consequences for lizard populations in response to red fox competition. Nevertheless, our results help broaden understanding of the physiological implications arising from species interactions and specifically how introduced competitors could mediate diverse impacts on native biodiversity.

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Coexistence between native and exotic species is facilitated by asymmetries in competitive ability and susceptibility to herbivores

Cited by 73 publications

References 48 publications

Non-native plants add to the British flora without negative consequences for native diversity

Non-native plants add to the British flora without negative consequences for native diversity

Room for one more? Coexistence of native and non-indigenous barnacle species

An Introduced Competitor Elevates Corticosterone Responses of a Native Lizard (Varanus varius)

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