Abstract
Invasive species and habitat disturbance threaten biodiversity worldwide by modifying ecosystem performance and displacing native organisms. Similar homogenization impacts manifest locally when urbanization forces native species to relocate or reinvade perpetually altered habitat. This study investigated correlations between ant richness and abundance in response to urbanization and the nearby presence of invasive ant species, odorous house ants (Tapinoma sessile), within its native region. Surveying localized ant composition within natural, semi-natural, and urban habitat supported efforts to determine whether T. sessile appear to be primary (drivers) threats as instigators or secondary (passengers) threats as inheritors of indigenous ant decline. Sampling 180 sites, evenly split between all habitats with and without T. sessile present, yielded 45 total species. Although urbanization and T. sessile presence factors were significantly linked to ant decline, their interaction correlated to the greatest reduction of total ant richness (74%) and abundance (81%). Total richness appeared to decrease from 27 species to 18 when natural habitat is urbanized and from 18 species to 7 with T. sessile present in urban plots. Odorous house ant presence minimally influenced ant communities within natural and semi-natural habitat, highlighting the importance of habitat alteration and T. sessile presence interactions. Results suggest urbanization releases T. sessile from unknown constraints by decreasing ant richness and competition. Within urban environment, T. sessile are pre-adapted to quickly exploit new resources and grow to supercolony strength wherein T. sessile drive adjacent biodiversity loss. Odorous house ants act as passengers and drivers of ecological change throughout different phases of urban ‘invasion’. This progression through surviving habitat alteration, exploiting new resources, thriving, and further reducing interspecific competition supports a “back-seat driver” role and affects pest management strategies. As demonstrated by T. sessile, this article concludes native species can become back-seat drivers of biodiversity loss and potentially thrive as “metro-invasive” species.
Highlights
Habitat alteration and invasive species are commonly cited as the main causes of biodiversity loss [1], [2]
A total of 45 ant species representing 894 nests were discovered in 180 plots (Table 1). These species comprised of 20 genera in 4 subfamilies. Both T. sessile presence and urbanization negatively correlated with adjacent ant community richness and diversity
Urbanization correlated with a diminished total ant richness from 27 to 18 species (233%), while the presence of T. sessile further lowered ant richness from 18 to 7 species (241%) in the immediate vicinity of T. sessile nests
Summary
Habitat alteration and invasive species are commonly cited as the main causes of biodiversity loss [1], [2]. Habitat alteration is thought to be the primary factor affecting biotic homogenization and localized species extinctions, and species invasions are thought to have a lesser, secondary role [1]–[3]. These two factors often overlap making it difficult to determine their relative contribution, if any, to localized extinctions. Several studies question the importance of species invasions, and propose invasive species are not drivers of biodiversity loss, but rather are passengers of more fundamental change in the ecosystem [4]–[6]. Additional research needs to de-couple invasion and habitat alteration by examining indigenous species intolerant of ecological change
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