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Invasive fire ants reduce reproductive success and alter the reproductive strategies of a native vertebrate insectivore.

Ligon RA, Siefferman L, Hill GE - PLoS ONE (2011)

Bottom Line: To explore the effects of fire ants on a native insectivorous vertebrate, we compared the reproductive success and strategies of eastern bluebirds (Sialia sialis) inhabiting territories with different abundances of fire ants.We found that more bluebird young fledged from treated territories than from adjacent control territories.These results illustrate the negative effects that invasive species can have on native biota, including species from taxonomically distant groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Auburn University, Auburn, Alabama, United States of America. russell.ligon@gmail.com

ABSTRACT

Background: Introduced organisms can alter ecosystems by disrupting natural ecological relationships. For example, red imported fire ants (Solenopsis invicta) have disrupted native arthropod communities throughout much of their introduced range. By competing for many of the same food resources as insectivorous vertebrates, fire ants also have the potential to disrupt vertebrate communities.

Methodology/principal findings: To explore the effects of fire ants on a native insectivorous vertebrate, we compared the reproductive success and strategies of eastern bluebirds (Sialia sialis) inhabiting territories with different abundances of fire ants. We also created experimental dyads of adjacent territories comprised of one territory with artificially reduced fire ant abundance (treated) and one territory that was unmanipulated (control). We found that more bluebird young fledged from treated territories than from adjacent control territories. Fire ant abundance also explained significant variation in two measures of reproductive success across the study population: number of fledglings and hatching success of second clutches. Furthermore, the likelihood of bluebird parents re-nesting in the same territory was negatively influenced by the abundance of foraging fire ants, and parents nesting in territories with experimentally reduced abundances of fire ants produced male-biased broods relative to pairs in adjacent control territories.

Conclusions/significance: Introduced fire ants altered both the reproductive success (number of fledglings, hatching success) and strategies (decision to renest, offspring sex-ratio) of eastern bluebirds. These results illustrate the negative effects that invasive species can have on native biota, including species from taxonomically distant groups.

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Probability of bluebirds re-nesting in their original territory as a function of fire ant abundance.Relationship between fire ant abundance (mean number of ants captured per sample vial) and the calculated probability of re-nesting by the same eastern bluebird parents (n = 29). Logistic regression equation (Y = e1.9204 -0.00958(fire ant abundance)/1+ e1.9204 - 0.00958(fire ant abundance)), where Y is equal to the probability of re-nesting, represented by the line.
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pone-0022578-g003: Probability of bluebirds re-nesting in their original territory as a function of fire ant abundance.Relationship between fire ant abundance (mean number of ants captured per sample vial) and the calculated probability of re-nesting by the same eastern bluebird parents (n = 29). Logistic regression equation (Y = e1.9204 -0.00958(fire ant abundance)/1+ e1.9204 - 0.00958(fire ant abundance)), where Y is equal to the probability of re-nesting, represented by the line.

Mentions: To determine whether bluebird parents re-used the same nest box during their second breeding attempt of the season we had to capture both parents at the nest box during both breeding attempts. After analyzing the 39 nest locations across the study population where either a) we positively identified mothers and fathers from both first and second broods or b) no second nesting attempt occurred, we determined that re-nesting by one or both of the original parents at a nest was equally likely in both treated and untreated territories (overall probability of re-nesting  =  0.64, chi-square between control and treated territories  =  0.03, d.f. = 1, p = 0.86). However, when we used a logistic regression to analyze the likelihood of re-nesting across territories for which we had data on abundance of foraging fire ant and re-nesting information (n = 29 nests), we found a significant negative relationship between fire ant abundance and likelihood of re-nesting (n = 29, p = 0.045). This effect may be driven by territories with very high fire ant numbers and the fact that parents at these nests did not undertake a second breeding attempt at the same site (Fig. 3).


Invasive fire ants reduce reproductive success and alter the reproductive strategies of a native vertebrate insectivore.

Ligon RA, Siefferman L, Hill GE - PLoS ONE (2011)

Probability of bluebirds re-nesting in their original territory as a function of fire ant abundance.Relationship between fire ant abundance (mean number of ants captured per sample vial) and the calculated probability of re-nesting by the same eastern bluebird parents (n = 29). Logistic regression equation (Y = e1.9204 -0.00958(fire ant abundance)/1+ e1.9204 - 0.00958(fire ant abundance)), where Y is equal to the probability of re-nesting, represented by the line.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3140521&req=5

pone-0022578-g003: Probability of bluebirds re-nesting in their original territory as a function of fire ant abundance.Relationship between fire ant abundance (mean number of ants captured per sample vial) and the calculated probability of re-nesting by the same eastern bluebird parents (n = 29). Logistic regression equation (Y = e1.9204 -0.00958(fire ant abundance)/1+ e1.9204 - 0.00958(fire ant abundance)), where Y is equal to the probability of re-nesting, represented by the line.
Mentions: To determine whether bluebird parents re-used the same nest box during their second breeding attempt of the season we had to capture both parents at the nest box during both breeding attempts. After analyzing the 39 nest locations across the study population where either a) we positively identified mothers and fathers from both first and second broods or b) no second nesting attempt occurred, we determined that re-nesting by one or both of the original parents at a nest was equally likely in both treated and untreated territories (overall probability of re-nesting  =  0.64, chi-square between control and treated territories  =  0.03, d.f. = 1, p = 0.86). However, when we used a logistic regression to analyze the likelihood of re-nesting across territories for which we had data on abundance of foraging fire ant and re-nesting information (n = 29 nests), we found a significant negative relationship between fire ant abundance and likelihood of re-nesting (n = 29, p = 0.045). This effect may be driven by territories with very high fire ant numbers and the fact that parents at these nests did not undertake a second breeding attempt at the same site (Fig. 3).

Bottom Line: To explore the effects of fire ants on a native insectivorous vertebrate, we compared the reproductive success and strategies of eastern bluebirds (Sialia sialis) inhabiting territories with different abundances of fire ants.We found that more bluebird young fledged from treated territories than from adjacent control territories.These results illustrate the negative effects that invasive species can have on native biota, including species from taxonomically distant groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Auburn University, Auburn, Alabama, United States of America. russell.ligon@gmail.com

ABSTRACT

Background: Introduced organisms can alter ecosystems by disrupting natural ecological relationships. For example, red imported fire ants (Solenopsis invicta) have disrupted native arthropod communities throughout much of their introduced range. By competing for many of the same food resources as insectivorous vertebrates, fire ants also have the potential to disrupt vertebrate communities.

Methodology/principal findings: To explore the effects of fire ants on a native insectivorous vertebrate, we compared the reproductive success and strategies of eastern bluebirds (Sialia sialis) inhabiting territories with different abundances of fire ants. We also created experimental dyads of adjacent territories comprised of one territory with artificially reduced fire ant abundance (treated) and one territory that was unmanipulated (control). We found that more bluebird young fledged from treated territories than from adjacent control territories. Fire ant abundance also explained significant variation in two measures of reproductive success across the study population: number of fledglings and hatching success of second clutches. Furthermore, the likelihood of bluebird parents re-nesting in the same territory was negatively influenced by the abundance of foraging fire ants, and parents nesting in territories with experimentally reduced abundances of fire ants produced male-biased broods relative to pairs in adjacent control territories.

Conclusions/significance: Introduced fire ants altered both the reproductive success (number of fledglings, hatching success) and strategies (decision to renest, offspring sex-ratio) of eastern bluebirds. These results illustrate the negative effects that invasive species can have on native biota, including species from taxonomically distant groups.

Show MeSH
Related in: MedlinePlus