Abstract
We found that competitive exclusion from agricultural habitats by invading species is likely playing a major role in the decline of several formerly-dominant native species. Several native species (Adalia bipunctata and Coccinella trifasciata) persist at low numbers in seminatural forest habitats embedded in agricultural landscapes but are no longer observed in cultivated habitat (Fig 6). This finding provides support to Evans’3 habitat compression hypothesis, a consequence of competitive exclusion in which native coccinellid species ‘retreat’ to ancestral habitats when resources in croplands become depleted by exotic species that have co-evolved with cultivated habitats. We found that the herbivore suppression potential of the ladybeetle community remained roughly constant since the initiation of the study (Fig. 7), and Shannon diversity of the community increased slightly (Fig 8). These results suggest that, despite invasions, the coccinellid community is still capable of providing the same level of pest suppression ecosystem service. However, declines in biodiversity are likely to occur if semi-natural habitats within the agricultural matrix are lost. Future work will explore niche interactions for species within the community and examine population cycling of individual species in the context of resource availability
Published Version
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