Contrasting Responses of Native Ant Communities to Invasion by an Ant Invader, Linepithema Humile
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Biol Invasions https://doi.org/10.1007/s10530-021-02522-7 (0123456789().,-volV)( 0123456789().,-volV) ORIGINAL PAPER Contrasting responses of native ant communities to invasion by an ant invader, Linepithema humile Adam J. M. Devenish . Rosemary J. Newton . Jon R. Bridle . Crisanto Gomez . Jeremy J. Midgley . Seirian Sumner Received: 29 January 2020 / Accepted: 5 February 2021 Ó The Author(s) 2021 Abstract Invasive alien species pose a serious threat through the displacement and local extinction of to the integrity and function of natural ecosystems. native species. However, sampling methods and Understanding how these invaders alter natural com- intensities are rarely standardised across such studies, munities is therefore an important aspect in predicting meaning that it is not clear whether differences in the likely future outcomes of biological invasions. response among native communities to the same Many studies have documented the consequences of invader species are due to biological differences invasive alien species on native community structure, between the invaded regions, or differences in the methodologies used. Here we use a matched sampling methodology to compare the effects of the Argentine Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/ ant (Linepithema humile Mayr) on native ant commu- s10530-021-02522-7. nity assemblages in two distinct biogeographical regions that share similar ecologies: Girona (Spain) & A. J. M. Devenish ( ) Á R. J. Newton and Jonkershoek Nature Reserve (South Africa). We Conservation Science, Royal Botanic Gardens Kew, Wakehurst Place, Ardingly, UK found a strong negative association between L. humile e-mail: [email protected] presence and native ant species richness within both geographic regions. However, the effects differed A. J. M. Devenish Á J. R. Bridle Á S. Sumner between the two study regions: in Girona, a single School of Biological Sciences, University of Bristol, Bristol, UK native ant species (Plagiolepis pygmaea) persisted in invaded sites; by contrast, substantially more native A. J. M. Devenish ant species persisted at invaded sites in Jonkershoek Department of Life Sciences, Imperial College London, Nature Reserve. In addition, in Jonkershoek Nature London, UK Reserve, the abundance of certain native species A. J. M. Devenish Á J. R. Bridle Á S. Sumner appeared to increase in the presence of L. humile.This CBER, Department of Genetics, Evolution and study therefore demonstrates the potential variable Environment, University College London, London, UK effects of an invasive species in contrasting locations C. Gomez within different biogeographical regions. Future work Department of Environmental Sciences, University of should explore the causes of this differential resistance Girona, Girona, Spain among communities and expand standardised sam- pling approaches to more invaded zones to further J. J. Midgley Department of Biological Sciences, University of Cape explore how local biotic or abiotic conditions of a Town, Rondebosch, Cape Town, South Africa 123 A. J. M. Devenish et al. region determine the nature and extent of impact of L. region. In reality the impacts of IAS are heteroge- humile invasion on native ant communities. neous, and seldom unidirectional (Vila` et al. 2011). Variable responses of different native communities to Keywords Argentine ant Á Biological invasions Á the same IAS may be due to the innate differences in Cape floristic region Á Community structure Á the abiotic (e.g. temperature, rainfall) and/or biotic Competitive displacement Á Field experiment Á (e.g. population size, taxonomic diversity, functional Formicidae Á Iberian peninsula Á Linepithema humile diversity) conditions of the environment (Sofaer et al. 2018). Understanding what these differential responses tell us more broadly about community organisation and resilience requires not only a large Introduction source pool of studies, but also greater consistency in the approaches used. This is necessary to ensure Invasive alien species (IAS) pose a serious threat to the findings are comparable across studies and/or geo- structure and function of native communities. The graphic regions, so that they are representative of frequency of IAS introductions has increased world- geographic and taxonomic differences, rather than wide, with more than a third of all introductions differences in study design. occurring over the last 45 years (Seebens et al. 2018). Invasive ants are among the worst and the most Displacement of native species as a result of invasion pervasive of IAS. As with other IAS, ants have is widely recognised as one of the leading drivers of benefited from the breakdown of geographical barriers global biodiversity loss (Clavero and Garcı´a-Berthou and increase in globalisation, so much so that today 2005; Simberloff et al. 2013; Bellard et al. 2016). The invasive ant species can be found on every continent presence of an IAS within a region is often associated except Antarctica (Bertelsmeier et al. 2017). Many ant with a number of negative impacts on resident invasions go unnoticed until they are already well communities, such as the reduction in the abundance established; however, once present, these invaders not and diversity of native species (Vila` et al. 2011). only displace native species, but also cause a rapid Cascading effects on the structure, function and shift in the native ant community structure (Sanders resilience of native communities and ecosystems et al. 2003; Wittman 2014). Some areas in which they (Sanders et al. 2003; Sax and Gaines 2008) following are found show up to a 90% reduction in resident ant IAS introductions can, in turn, have severe negative species richness, which can significantly alter the impacts on the economy and human health (Essl et al. phylogenetic structure of native ant communities 2011; Carpenter et al. 2013; Bradshaw et al. 2016). (Holway et al. 2002; Lessard et al. 2009). Ants, Understanding, predicting, and mitigating the impact therefore, represent an excellent study system with of invasive species on biodiversity and human liveli- which to explicitly test for different responses of hoods therefore remains a key priority for the global native communities across different continents and community. In order to prioritise when and where an communities. intervention is applied, one needs a clear understand- Five invasive ant species (Anoplolepis gracilipes; ing of which ecosystems are more vulnerable to Linepithema humile; Pheidole megacephala; invasion. Solenopsis invicta; Wasmannia auropunctata) are Our ability to predict the impacts of IAS largely recognised as being among the ‘100 of the worst’ comes from knowledge of prior invasion histories. invaders in the world (Global Invasive Species Increasingly, more sophisticated tools and methods Database 2020). Of these species, one of the most are being used to detect future invaders, and to identify well-known is the Argentine ant (Linepithema humile where future invasions are likely to occur (Fournier Mayr; subfamily Dolichoderinae). Originating from et al. 2019). Nevertheless, predicting the direction and/ South America, L. humile can now be found across six or magnitude of the impact of IAS remains challeng- continents and several oceanic islands (Suarez et al. ing (Jaric´ et al. 2019). This is because these predictions 2001; Wetterer et al. 2009). It is particularly common often assume the impact measured in one location or in regions with a Mediterranean or subtropical climate geographic region is likely to be representative of the (Tsutsui et al. 2000). Once present, it can quickly potential impact in another location or geographic overwhelm the resident community, leading to 123 Contrasting responses of native ant communities to invasion by an ant invader, Linepithema… declines in species richness and abundance of both Spain native ants (Suarez et al. 1998; Human and Gordon 1999; Sanders et al. 2003) and other invertebrates Linepithema humile was first recorded in the Iberian (Human and Gordon 1997). Whilst this species is Peninsula at the beginning of the nineteenth century generally associated with human-modified and dis- (Espadaler and Go´mez 2003). Since then its popula- turbed habitats (Holway et al. 2002), it is also found in tion has expanded considerably in Northern Spain, more ‘natural’ and undisturbed habitats (De Kock and particularly in coastal regions at an estimated rate of Giliomee 1989; Christian 2001; Gomez and Oliveras 7.94 (± 2.99) metres per year (Roura-Pascual et al. 2003; Holway and Suarez 2006; Luruli 2007; Roura- 2010). The study in Spain was conducted across eight Pascual et al. 2010; Mothapo 2013). Despite the sites (four control and four invaded; Fig. 1a) in and almost ubiquitous nature of L. humile, assessing its around Girona (North-eastern Spain) (Devenish et al. impact across native communities remains difficult 2018). Four of the selected sites were previously because different studies have used different sampling known to be invaded by L. humile; two were near methods or have chosen different temporal periods University of Girona Montilivi Campus over which to measure its impact on native ant (41°58059.20‘‘N, 02°49029.75’’E) and two near Castell community structure. Globally, of the regions that L. d’Aro (30 km away) (41°49004.61‘‘N, humile has invaded, the South African Cape Floristic 03°04000.68’’E). Sites were selected on the basis that Region is arguably one of the least studied