Diversity, endemism and origins of scale insects on a tropical oceanic island: Implications for management of an invasive ant

Neumann, Gabor; O'Dowd, Dennis Jefferie; Gullan, Penny J.; Green, Peter T.

doi:10.1016/j.aspen.2015.12.015

Cited by 16 publications

(11 citation statements)

References 33 publications

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“…(Coccidae), and Saissetia sp. (Coccidae) [O'Dowd et al 2003, Abbott 2004, Abbott and Green 2007, Neumann et al 2016). Experimental removal of YCAs has shown that honeydew-producing scale insects rely upon YCAs for survival (Abbott and Green 2007), likely due to YCA removal of honeydew that prevents scale insect asphyxiation, husbandry of the scale insect mobile crawler stage, and protection of scale insects against natural enemies (Abbott 2004, Ness andBronstein 2004).…”

Section: Introductionmentioning

confidence: 99%

Carbohydrate supply drives colony size, aggression, and impacts of an invasive ant

2018

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Worldwide, the most ecologically damaging invasive ants are associated with introduced honeydew‐producing insects, yet the mechanisms by which this mutualism may support invasive ant populations and drive impacts remain unclear. On Christmas Island, the invasive yellow crazy ant (Anoplolepis gracilipes; YCA), found in association with introduced honeydew‐producing scale insects, can reach extraordinary densities, triggering an ecological meltdown. In this study, we utilized stable isotope analysis to determine resource use of YCAs in naturally occurring low‐ and high‐density populations, and we conducted laboratory experiments mimicking availability of honeydew to measure effects of carbohydrate subsidies on colony growth and worker behavior. High‐density YCA populations in nature incorporated a larger proportion of plant‐based resources in their diet than low‐density populations, and laboratory colonies with access to greater sugar resources had larger colony sizes, higher reproduction rates and worker survival, and higher per capita activity levels and showed higher aggression and potency toward opponents. These results support the positive feedback mechanism between honeydew‐producing insects and YCAs that underlies the ecological meltdown on Christmas Island, and add to the growing body of literature illustrating the importance of mutualistic interactions in the success of invasive species.

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Section: Introductionmentioning

confidence: 99%

Carbohydrate supply drives colony size, aggression, and impacts of an invasive ant

2018

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“…In this context, managing the mechanism which facilitates the entry and spread of A. fulica – yellow crazy ant invasion – should continue to be prioritized (Neumann et al . ) in preference to direct control of this secondary invader.…”

Section: Discussionmentioning

confidence: 99%

“…The yellow crazy ant ( Anoplolepis gracilipes ), a pantropical invader that has spread rapidly across the Indo‐Pacific region (Wetterer ), has formed a mutualistic relationship with a number of non‐native honeydew‐secreting insects (Neumann et al . ) which has resulted in expansive high‐density supercolonies on the island (O'Dowd et al . ; Abbott ).…”

Section: Methodsmentioning

confidence: 99%

The secondary invasion of giant African land snail has little impact on litter or seedling dynamics in rainforest

O’Loughlin

Green

2017

Austral Ecology

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In the absence of empirical evidence, invasive species are often assumed to have negative impacts because of their conspicuously high abundance. The giant African land snail Achatina (Lissachatina) fulica is one such invader where its impact in natural ecosystems remains completely untested. On Christmas Island (Indian Ocean), A. fulica has become established across large tracts of rainforest following the impacts of invasive yellow crazy ant (Anoplolepis gracilipes) in mutualism with non-native scale insects. Yellow crazy ants facilitate the secondary invasion of A. fulica by extirpating native red land crabs (Gecarcoidea natalis) that are normally effective predators of A. fulica. We used a multifaceted approach to investigate some potential impacts of abundant A. fulica in invaded rainforest. Over the course of a wet season, diel activity transects showed that A. fulica consumed detrital material almost exclusively. However, stable isotope analysis did not confidently identify A. fulica as a predominantly detritivorous species. We found no statistically significant treatment effects of A. fulica exclusion on standing leaf litter and seedling recruitment processes during a 6-month manipulative field study. However, litter cover and biomass did remain slightly higher where A. fulica were excluded, albeit with overlapping confidence intervals with control plots. Our study constitutes the first empirical test for impact of A. fulica in a natural ecosystem and suggests that for Christmas Island rainforest, this species is not a damaging invader. Other studies will need to assess the impacts of A. fulica in other natural areas before these findings could be considered broadly applicable.

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“…The yellow crazy ant ( Anoplolepis gracilipes ) is a pantropical invader that has spread rapidly across the Indo‐Pacific region (Wetterer ) and, in association with honeydew‐secreting insects (Neumann et al. ), has formed expansive high‐density supercolonies on Christmas Island (O'Dowd et al. , Abbott ).…”

Section: Methodsmentioning

confidence: 99%

“…The omnivorous red land crab also opportunistically preys on some non-native species, providing the community with biotic resistance against invaders O'Dowd 1991, Green et al 2011). The yellow crazy ant (Anoplolepis gracilipes) is a pantropical invader that has spread rapidly across the Indo-Pacific region (Wetterer 2005) and, in association with honeydew-secreting insects (Neumann et al 2016), has formed expansive high-density supercolonies on Christmas Island (O'Dowd et al 2003, Abbott 2006. Where supercolonies have formed, red land crabs are extirpated through predation by yellow crazy ants, which has led to considerable changes in forest understory structure (O'Dowd et al 2003).…”

Section: Study Systemmentioning

confidence: 99%

Habitat augmentation drives secondary invasion: an experimental approach to determine the mechanism of invasion success

O’Loughlin

Green

2016

Ecology

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The entry of secondary invaders into, or their expansion within, native communities is contingent on the changes wrought by other (primary) invaders. When primary invaders have altered more than one property of the recipient community, standard descriptive and modeling approaches only provide a best guess of the mechanism permitting the secondary invasion. In rainforest on Christmas Island, we conducted a manipulative field experiment to determine the mechanism of invasion success for a community of land snails dominated by non-native species. The invasion of rainforest by the yellow crazy ant (Anoplolepis gracilipes) has facilitated these land snails, either by creating enemy-free space and/or increased habitat and resources (in the form of leaf litter) through the removal of the native omnivorous-detritivorous red land crab (Gecarcoidea natalis). We manipulated predator densities (high and low) and leaf litter (high and low) in replicated blocks of four treatment combinations at two sites. Over the course of one wet season (five months), we found that plots with high leaf litter biomass contained significantly more snails than those with low biomass, regardless of whether those plots had high or low predation pressure, at both the site where land crabs have always been abundant, and at the site where they have been absent for many years prior to the experiment. Each site was dominated by small snail species (<2 mm length), and through handling size and predation experiments we demonstrated that red crabs tend not to handle and eat snails of that size. These results suggest that secondary invasion by this community of non-native land snails is facilitated most strongly by habitat and resource augmentation, an indirect consequence of red land crab removal, and that the creation of enemy-free space is not important. By using a full-factorial experimental approach, we have confidently determined-rather than inferred-the mechanism by which primary invaders indirectly facilitate a community of secondary invaders.

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Diversity, endemism and origins of scale insects on a tropical oceanic island: Implications for management of an invasive ant

Cited by 16 publications

References 33 publications

Carbohydrate supply drives colony size, aggression, and impacts of an invasive ant

Carbohydrate supply drives colony size, aggression, and impacts of an invasive ant

The secondary invasion of giant African land snail has little impact on litter or seedling dynamics in rainforest

Habitat augmentation drives secondary invasion: an experimental approach to determine the mechanism of invasion success

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