Limits...
Behavioral plasticity mediates asymmetric competition between invasive wasps and native ants.

Grangier J, Lester PJ - Commun Integr Biol (2012)

Bottom Line: One of the most successful invasive species is the common wasp, Vespula vulgaris.We first highlight the questions this interaction raises regarding the competitive advantages offered by asymmetries in body size and flight ability.Then, we argue that this study system illustrates the important role of behavioral plasticity in biological invasions; not only in the success of invaders but also in the ability of native species to coexist with these invaders.

View Article: PubMed Central - PubMed

Affiliation: Centre for Biodiversity and Restoration Ecology; School of Biological Sciences; Victoria University of Wellington; Wellington, New Zealand.

ABSTRACT
One of the most successful invasive species is the common wasp, Vespula vulgaris. We recently reported how foragers of this species have adopted previously unknown interference behavior when competing for food with native ants. Picking their opponents up in their mandibles, flying backward and dropping them some distance away from the disputed resource, wasps were shown to efficiently deal with a yet aggressive competitor and to modulate this behavior according to circumstances. Here we further discuss the nature and functioning of this unusual strategy. We first highlight the questions this interaction raises regarding the competitive advantages offered by asymmetries in body size and flight ability. Then, we argue that this study system illustrates the important role of behavioral plasticity in biological invasions; not only in the success of invaders but also in the ability of native species to coexist with these invaders.

No MeSH data available.


Related in: MedlinePlus

Figure 1.  Percentage of ant-wasp encounters resulting in aggressive acts by wasps (A) or ants (B), as a function of the ratio between average ant and wasp abundance at protein baits (n = number of bait stations per ratio category). Box plots show 10th and 90th percentiles (whiskers), 25th and 75th percentiles (boundary of the box), median (line) and outliers (black dots). All data were obtained by videotaping ant-wasp interactions at each bait station for approximately 40 min (see ref. 4 for details). Inset pictures show the typical postures of (A) wasps just before picking up an ant and dropping it away from the resource, or (B) ants adopting a threatening posture with wide open mandibles and a drop of acid at the tip of the gaster (white arrow). Below the x-axis of (B) is a schematic representation of ants and wasps (small and large black dots, respectively) when both species were present around the food bait (large gray dot). The proportion of aggressive interactions is relative to the number of passive contacts (contacts that resulted in no response from either species). This proportion differed significantly in both wasps and ants according to the category of ant/wasp abundance ratio (Kruskal-Wallis tests: H = 9.42, p = 0.024 and H = 8.43, p = 0.038; respectively). Different letters indicate a significant difference after a Dunn’s post-hoc test (p < 0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3376045&req=5

Figure 1: Figure 1. Percentage of ant-wasp encounters resulting in aggressive acts by wasps (A) or ants (B), as a function of the ratio between average ant and wasp abundance at protein baits (n = number of bait stations per ratio category). Box plots show 10th and 90th percentiles (whiskers), 25th and 75th percentiles (boundary of the box), median (line) and outliers (black dots). All data were obtained by videotaping ant-wasp interactions at each bait station for approximately 40 min (see ref. 4 for details). Inset pictures show the typical postures of (A) wasps just before picking up an ant and dropping it away from the resource, or (B) ants adopting a threatening posture with wide open mandibles and a drop of acid at the tip of the gaster (white arrow). Below the x-axis of (B) is a schematic representation of ants and wasps (small and large black dots, respectively) when both species were present around the food bait (large gray dot). The proportion of aggressive interactions is relative to the number of passive contacts (contacts that resulted in no response from either species). This proportion differed significantly in both wasps and ants according to the category of ant/wasp abundance ratio (Kruskal-Wallis tests: H = 9.42, p = 0.024 and H = 8.43, p = 0.038; respectively). Different letters indicate a significant difference after a Dunn’s post-hoc test (p < 0.05).

Mentions: This ant-dropping behavior also illustrates how interactions between native and invasive species may be mediated by plasticity. In social wasps, the invasive success and ecological impacts of V. pensylvanica in Hawaii have been linked to plasticity of life history traits.13 Our study suggests that flexibility in competitive behavior is another type of plasticity that may promote the success of invasive Vespula wasps. Increased ant abundance seemed to cause fewer wasps to visit food resources, but wasps that did compete with increasing densities of ants increased their competitive efforts so they can get at least a brief access to the resource. Indeed, the more ant competitors at food baits, the more frequently ant-removals occurred (Fig. 1A) and the further away ants were dropped.4 These results suggest that wasps are able to assess the degree of competition and modify their behavior accordingly. Interestingly, ants themselves also seem to adjust their competitive behavior to the circumstances. Further examination of our results revealed that the proportion of interactions in which ants behaved aggressively toward wasps varied as a function of the ratio between average ant and wasp abundances. The frequency of aggressive acts by ants was the highest with an ant/wasp ratio of between 50 and 200, but tended to be lower both below and above these values (Fig. 1B). An explanation for such a pattern could be that aggressiveness in P. advenus workers is dependent on group size and competitive pressure, as it is in other Formicine species.14,15 As a result, ants would be less aggressive toward wasps when perceiving either (1) that they are not numerous enough to efficiently face the threat posed by many individual wasps, and/or (2) that on the contrary they have secured the food item through massive recruitment, making wasps visits increasingly rare and costly aggressive behavior redundant. Additional work is currently being conducted by our team to examine in detail how the intensity of ant aggression, and also the exact amount of food collected by ants and wasps, varies according to the abundance of both species. The results obtained so far, however, suggest that behavioral plasticity characterizes responses of both invasive wasps and these native ants. This plasticity can be hypothesized to promote their coexistence, in line with more general views about the ecological consequences of phenotypic plasticity.16 A reduced level of competitive or aggressive responses when the context makes such behaviors useless or inefficient may result in both ants and wasps taking the advantage alternatively, enabling some degree of food collection for both. Accordingly to this hypothesis, the two species were usually not seen to completely exclude each other from food resources, and abundant populations of native ants and invasive wasps can co-exist (unpublished data).


Behavioral plasticity mediates asymmetric competition between invasive wasps and native ants.

Grangier J, Lester PJ - Commun Integr Biol (2012)

Figure 1.  Percentage of ant-wasp encounters resulting in aggressive acts by wasps (A) or ants (B), as a function of the ratio between average ant and wasp abundance at protein baits (n = number of bait stations per ratio category). Box plots show 10th and 90th percentiles (whiskers), 25th and 75th percentiles (boundary of the box), median (line) and outliers (black dots). All data were obtained by videotaping ant-wasp interactions at each bait station for approximately 40 min (see ref. 4 for details). Inset pictures show the typical postures of (A) wasps just before picking up an ant and dropping it away from the resource, or (B) ants adopting a threatening posture with wide open mandibles and a drop of acid at the tip of the gaster (white arrow). Below the x-axis of (B) is a schematic representation of ants and wasps (small and large black dots, respectively) when both species were present around the food bait (large gray dot). The proportion of aggressive interactions is relative to the number of passive contacts (contacts that resulted in no response from either species). This proportion differed significantly in both wasps and ants according to the category of ant/wasp abundance ratio (Kruskal-Wallis tests: H = 9.42, p = 0.024 and H = 8.43, p = 0.038; respectively). Different letters indicate a significant difference after a Dunn’s post-hoc test (p < 0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376045&req=5

Figure 1: Figure 1. Percentage of ant-wasp encounters resulting in aggressive acts by wasps (A) or ants (B), as a function of the ratio between average ant and wasp abundance at protein baits (n = number of bait stations per ratio category). Box plots show 10th and 90th percentiles (whiskers), 25th and 75th percentiles (boundary of the box), median (line) and outliers (black dots). All data were obtained by videotaping ant-wasp interactions at each bait station for approximately 40 min (see ref. 4 for details). Inset pictures show the typical postures of (A) wasps just before picking up an ant and dropping it away from the resource, or (B) ants adopting a threatening posture with wide open mandibles and a drop of acid at the tip of the gaster (white arrow). Below the x-axis of (B) is a schematic representation of ants and wasps (small and large black dots, respectively) when both species were present around the food bait (large gray dot). The proportion of aggressive interactions is relative to the number of passive contacts (contacts that resulted in no response from either species). This proportion differed significantly in both wasps and ants according to the category of ant/wasp abundance ratio (Kruskal-Wallis tests: H = 9.42, p = 0.024 and H = 8.43, p = 0.038; respectively). Different letters indicate a significant difference after a Dunn’s post-hoc test (p < 0.05).
Mentions: This ant-dropping behavior also illustrates how interactions between native and invasive species may be mediated by plasticity. In social wasps, the invasive success and ecological impacts of V. pensylvanica in Hawaii have been linked to plasticity of life history traits.13 Our study suggests that flexibility in competitive behavior is another type of plasticity that may promote the success of invasive Vespula wasps. Increased ant abundance seemed to cause fewer wasps to visit food resources, but wasps that did compete with increasing densities of ants increased their competitive efforts so they can get at least a brief access to the resource. Indeed, the more ant competitors at food baits, the more frequently ant-removals occurred (Fig. 1A) and the further away ants were dropped.4 These results suggest that wasps are able to assess the degree of competition and modify their behavior accordingly. Interestingly, ants themselves also seem to adjust their competitive behavior to the circumstances. Further examination of our results revealed that the proportion of interactions in which ants behaved aggressively toward wasps varied as a function of the ratio between average ant and wasp abundances. The frequency of aggressive acts by ants was the highest with an ant/wasp ratio of between 50 and 200, but tended to be lower both below and above these values (Fig. 1B). An explanation for such a pattern could be that aggressiveness in P. advenus workers is dependent on group size and competitive pressure, as it is in other Formicine species.14,15 As a result, ants would be less aggressive toward wasps when perceiving either (1) that they are not numerous enough to efficiently face the threat posed by many individual wasps, and/or (2) that on the contrary they have secured the food item through massive recruitment, making wasps visits increasingly rare and costly aggressive behavior redundant. Additional work is currently being conducted by our team to examine in detail how the intensity of ant aggression, and also the exact amount of food collected by ants and wasps, varies according to the abundance of both species. The results obtained so far, however, suggest that behavioral plasticity characterizes responses of both invasive wasps and these native ants. This plasticity can be hypothesized to promote their coexistence, in line with more general views about the ecological consequences of phenotypic plasticity.16 A reduced level of competitive or aggressive responses when the context makes such behaviors useless or inefficient may result in both ants and wasps taking the advantage alternatively, enabling some degree of food collection for both. Accordingly to this hypothesis, the two species were usually not seen to completely exclude each other from food resources, and abundant populations of native ants and invasive wasps can co-exist (unpublished data).

Bottom Line: One of the most successful invasive species is the common wasp, Vespula vulgaris.We first highlight the questions this interaction raises regarding the competitive advantages offered by asymmetries in body size and flight ability.Then, we argue that this study system illustrates the important role of behavioral plasticity in biological invasions; not only in the success of invaders but also in the ability of native species to coexist with these invaders.

View Article: PubMed Central - PubMed

Affiliation: Centre for Biodiversity and Restoration Ecology; School of Biological Sciences; Victoria University of Wellington; Wellington, New Zealand.

ABSTRACT
One of the most successful invasive species is the common wasp, Vespula vulgaris. We recently reported how foragers of this species have adopted previously unknown interference behavior when competing for food with native ants. Picking their opponents up in their mandibles, flying backward and dropping them some distance away from the disputed resource, wasps were shown to efficiently deal with a yet aggressive competitor and to modulate this behavior according to circumstances. Here we further discuss the nature and functioning of this unusual strategy. We first highlight the questions this interaction raises regarding the competitive advantages offered by asymmetries in body size and flight ability. Then, we argue that this study system illustrates the important role of behavioral plasticity in biological invasions; not only in the success of invaders but also in the ability of native species to coexist with these invaders.

No MeSH data available.


Related in: MedlinePlus