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Kenneth G. Ross - One of the best experts on this subject based on the ideXlab platform.

  • genetic regulation of colony social organization in Fire Ants an integrative overview
    The Quarterly Review of Biology, 2007
    Co-Authors: Dietrich Gotzek, Kenneth G. Ross
    Abstract:

    ABSTRACT Expression of colony social organization in Fire Ants appears to be under the control of a single Mendelian factor of large effect. Variation in colony queen number in Solenopsis invicta and its relatives is associated with allelic variation at the gene Gp‐9, but not with variation at other unlinked genes; workers regulate queen identity and number on the basis of Gp‐9 genotypic compatibility. Nongenetic factors, such as prior social experience, queen reproductive status, and local environment, have negligible effects on queen number, which illustrates the nearly complete penetrance of Gp‐9. As predicted, queen number can be manipulated experimentally by altering worker Gp‐9 genotype frequencies. The Gp‐9 allele lineage associated with polygyny in South American Fire Ants has been retained across multiple speciation events, which may signal the action of balancing selection to maintain social polymorphism in these species. Moreover, positive selection is implicated in driving the molecular evolut...

  • molecular phylogeny of Fire Ants of the solenopsis saevissima species group based on mtdna sequences
    Molecular Phylogenetics and Evolution, 2006
    Co-Authors: Dewayne Shoemaker, Michael E Ahrens, Kenneth G. Ross
    Abstract:

    The systematics of South American Fire Ants (Solenopsis saevissima species-group) has been plagued by difficulties in recognizing species and their relationships on the basis of morphological characters. We surveyed mtDNA sequences from 623 individuals representing 13 described and undescribed species within the species-group and 18 individuals representing other major Solenopsis lineages to generate a phylogeny of the mitochondrial genome. Our analyses support the monophyly of the S. saevissima species-group, consistent with a single Neotropical origin and radiation of this important group of Ants, as well as the monophyly of the socially polymorphic species within the group, consistent with a single origin of polygyny (multiple queens per colony) as a derived form of social organization. The mtDNA sequences of the inquiline social parasite S. daguerrei form a clade that appears to be distantly related to sequences from the several host species, consistent with the view that advanced social parasitism did not evolve via sympatric speciation of intraspecific parasites. An important general finding is that species-level polyphyly of the mtDNA appears to be the rule in this group of Ants. The existence of multiple divergent mtDNA lineages within several nominal species (including the pest S. invicta) suggests that the pattern of widespread polyphyly often stems from morphological delimitation that overcircumscribes species. However, in two cases the mtDNA polyphyly likely results from recent interspecific hybridization. While resolving species boundaries and relationships is important for understanding general patterns of diversification of South American Fire Ants, these issues are of added importance because invasive Fire Ants are emerging as global pests and becoming important model organisms for evolutionary research.

  • species delimitation in native south american Fire Ants
    Molecular Ecology, 2005
    Co-Authors: Kenneth G. Ross, Dewayne Shoemaker
    Abstract:

    The taxonomy of Fire Ants has been plagued by difficulties in recognizing species on the basis of morphological characters. We surveyed allozyme markers and sequences of the mtDNA COI gene in several closely related nominal species from two areas of sympatry in the native ranges to learn whether the morphology-based delimitation of these species is supported by genetic data. We found that Solenopsis invicta and Solenopsis richteri , pest species whose distinctiveness has been debated, appear to be fully reproductively isolated at both study sites. This isolation contrasts with the extensive hybridization occurring between them in the USA, where both have been introduced. We also found strong genetic differentiation consistent with barriers to gene flow between Solenopsis quinquecuspis and the other two species. However, several lines of evidence suggest that nuclear and mitochondrial genes of S. invicta and S. richteri are introgressing into S. quinquecuspis . The latter apparently is a recently derived member of the clade that includes all three species, suggesting that there has been insufficient time for its full development of intrinsic isolating mechanisms. Finally, our discovery of genetically distinct populations within both S. invicta and S. richteri suggests the presence of previously unrecognized (cryptic) species. Their existence, together with the difficulties in developing diagnostic morphological characters for described species, imply that the group is actively radiating species and that morphological divergence generally does not keep pace with the development of reproductive isolation and neutral genetic divergence in this process.

  • cladistic analysis of the Fire Ants of the solenopsis saevissima species group hymenoptera formicidae
    Zoologica Scripta, 2005
    Co-Authors: James P Pitts, Joseph V Mchugh, Kenneth G. Ross
    Abstract:

    Results are presented from a phylogenetic study of the Fire Ants comprising the Solenopsis saevissima species-group (Hymenoptera: Formicidae). Six most-parsimonious trees were identified following a cladistic analysis utilizing 18 taxa and 36 morphological characters derived from three castes and two developmental stages. A strict consensus tree recovered the following relationships: (S. daguerrei ((S. electra, S. pusilignis) (S. saevissima (S. pythia (S. interrupta, S. ‘undescribed species’, S. weyrauchi (S. richteri, S. invicta (S. megergates (S. quinquecuspis, S. macdonaghi)))))))). This phylogenetic hypothesis implies trends in Fire ant evolution towards both polygyny (multiple egg-laying queens per colony) and large major worker size. The phylogeny also provides a test of Emery's Rule, which is not supported in its strictest sense because the social parasite S. daguerrei is not the sister species to its host species. A modified version of Emery's Rule is supported, because the social parasite is the sister species to a larger clade containing its hosts, as well as nonhosts.

  • Alternative genetic foundations for a key social polymorphism in Fire Ants.
    Genetics, 2003
    Co-Authors: Kenneth G. Ross, Michael J. B. Krieger, Dewayne Shoemaker
    Abstract:

    Little is known about the genetic foundations of colony social organization. One rare example in which a single major gene is implicated in the expression of alternative social organizations involves the presumed odorant-binding protein gene Gp-9 in Fire Ants. Specific amino acid substitutions in this gene invariably are associated with the expression of monogyny (single queen per colony) or polygyny (multiple queens per colony) in Fire ant species of the Solenopsis richteri clade. These substitutions are hypothesized to alter the abilities of workers to recognize queens and thereby regulate their numbers in a colony. We examined whether these same substitutions underlie the monogyny/polygyny social polymorphism in the distantly related Fire ant S. geminata. We found that Gp-9 coding region sequences are identical in the polygyne and monogyne forms of this species, disproving our hypothesis that one or a few specific amino acid replacements in the protein are necessary to induce transitions in social organization in Fire Ants. On the other hand, polygyne S. geminata differs genetically from the monogyne form in ways not mirrored in the two forms of S. invicta, a well-studied member of the S. richteri clade, supporting the conclusion that polygyny did not evolve via analogous routes in the two lineages. Specifically, polygyne S. geminata has lower genetic diversity and different gene frequencies than the monogyne form, suggesting that the polygyne form originated via a founder event from a local monogyne population. These comparative data suggest an alternative route to polygyny in S. geminata in which loss of allelic variation at genes encoding recognition cues has led to a breakdown in discrimination abilities and the consequent acceptance of multiple queens in colonies.

Li Zi-chen - One of the best experts on this subject based on the ideXlab platform.

  • pseudacteon phorid flies host specificity and impacts on solenopsis Fire Ants
    Annual Review of Entomology, 2018
    Co-Authors: Li Zi-chen, Henry Y. Fadamiro
    Abstract:

    Human commerce has resulted in the spread of the imported Fire Ants, Solenopsis species, worldwide. Six species of parasitic Pseudacteon phorid flies that are highly host specific to the Solenopsis saevissima complex of Solenopsis Fire Ants have been successfully released in the southern United States. The presence of Pseudacteon phorid flies, in addition to having direct mortality effects on their host Ants, modifies foraging behavior and disrupts interspecific competition between host species and other ant species in the community. Fire ant workers have evolved effective methods to cope with parasitism pressure, which may relieve population-level impacts of introduced phorid flies. This review focuses on the mechanisms underlying host location, host preference, and host-size selection of Pseudacteon phorid flies and highlights their direct and indirect effects on Fire ant populations. Knowledge gained from parasitoid–ant interactions will enhance use of natural enemies as biological control agents for i...

  • intra and inter specific variation in alarm pheromone produced by solenopsis Fire Ants
    Bulletin of Entomological Research, 2017
    Co-Authors: Rammohan R Balusu, Henry Y. Fadamiro, W Q Zhang, Olufemi S Ajayi, Rensen Zeng, Li Zi-chen
    Abstract:

    Some Fire Ants of the genus Solenopsis have become invasive species in the southern United States displacing native species by competition. Although the displacement pattern seems clear, the mechanisms underlying competitive advantage remain unclear. The ability of ant workers to produce relatively larger amount of alarm pheromone may correspond to relative greater fitness among sympatric Fire ant species. Here we report on quantitative intra-specific (i.e. inter-caste) and inter-specific differences of alarm pheromone component, 2-ethyl-3,6-dimethylpyrazine (2E36DMP), for several Fire ant species. The alarm pheromone component was extracted by soaking Ants in hexane for 48 h and subsequently quantified by gas chromatography-mass spectrometry at single ion monitoring mode. Solenopsis invicta workers had more 2E36DMP than male or female alates by relative weight; individual workers, however, contained significantly less pyrazine. We thus believe that alarm pheromones may serve additional roles in alates. Workers of Solenopsis richteri, S. invicta, and hybrid (S. richteri × S. invicta) had significantly more 2E36DMP than a native Fire ant species, Solenopsis geminata. The hybrid Fire ant had significantly less 2E36DMP than the two parent species, S. richteri and S. invicta. It seems likely that higher alarm pheromone content may have favored invasion success of exotic Fire Ants over native species. We discuss the potential role of inter-specific variation in pyrazine content for the relationship between the observed shifts in the spatial distributions of the three exotic Fire ant species in southern United States and the displacement of native Fire ant species.

  • quantitative analysis of alkaloidal constituents in imported Fire Ants by gas chromatography
    Journal of Agricultural and Food Chemistry, 2014
    Co-Authors: Hongyi Wei, Henry Y. Fadamiro, Li Zi-chen
    Abstract:

    A method based on silica gel chromatography and GC-MS/GC-FID analyses was developed for the quantitation of alkaloidal compounds in imported Fire Ants, Solenopsis richteri, S. invicta, and their hybrid found in the southern United States. The cis and trans alkaloids from Fire ant body extracts were successfully separated by silica gel chromatography, identified by GC-MS, and quantitated by GC-FID. Piperideine compounds were eluted together with the cis and trans piperidines, but were well-resolved on a nonpolar GC column. Eight pairs of piperidine isomers and 12 piperideines were quantitated. The ratios of trans alkaloids to corresponding cis isomers ranged from 87 to 378:1 in S. invicta and were significantly higher than in S. richteri and hybrid Ants. The results were discussed in relation to the evolution of Fire ant venom alkaloids and their role as host location cues for parasitic Pseudacteon phorid flies.

  • comparing electroantennogram and behavioral responses of two pseudacteon phorid fly species to body extracts of black red and hybrid imported Fire Ants solenopsis spp
    Journal of Insect Physiology, 2012
    Co-Authors: Xiaofang He, Samuel A Ochieng, Li Zi-chen, Henry Y. Fadamiro
    Abstract:

    Abstract Several phorid fly species were introduced to the southern United States for biological control of the invasive imported Fire Ants, Solenopsis richteri (Black), Solenopsis invicta (Red), and their Hybrid S. richteri × S. invicta (Hybrid). It has been previously reported that the Jaguariuna biotype of Pseudacteon tricuspis and the Formosan biotype of Pseudacteon curvatus could distinguish among the three Fire ant species with greater preference for Hybrid and Red Fire Ants. We hypothesized that phorid flies might use host derived chemical cues to differentiate ant species. To determine possible differential olfactory sensitivity of phorid fly species to different Fire ant species, we compared electroantennogram (EAG) and behavioral responses of both sexes of P. tricuspis and P. curvatus to body extracts of Black, Red and Hybrid Fire Ants. As worker sizes of Black and Hybrid Fire Ants used in this study were much larger than that of Red Fire ant (the average weight for Black, Red and Hybrid workers was 1.707, 0.863, 1.223 mg per Ants, respectively), at doses of 0.01, 0.1, 1 worker equivalent, body extracts of Black and Hybrid Fire ant elicited significantly greater EAG response in both sexes of P. tricuspis than that of Red Fire ant. Similarly, the EAG response in female P. curvatus to body extract of Black Fire ant was significantly greater than to body extract of Red Fire ant. To eliminate worker size influence on EAG response in phorid flies, we conducted a second EAG study using a dose of 1 mg ant equivalent (body extract from 1 mg of worker). No difference in EAG responses was recorded to body extract obtained from the same amount of workers among the three Fire ant species (we consider viable Hybrid Fire ant as a species in this paper), suggesting that worker size differences contributed to difference in EAG response in the first EAG study. In both EAG studies, male P. tricuspis showed significantly greater EAG responses than male P. curvatus to all three Fire ant species. In four-way olfactometer bioassay, worker body extracts of all three Fire ant species were equally attractive to P. tricuspis and P. curvatus (i.e. both phorid fly species did not show any preferences among the three Fire ant species). Together, the results of the EAG and behavior studies suggest that parasitic phorid flies utilize host derived non-polar compounds from worker Ants extracted out by hexane for host location but not for host preference, since both fly species are not able to distinguish among the body extracts of the three Fire ant species. Future study will investigate possible involvement of polar compounds and/or non-chemical cues in mediating host preference by phorid flies.

  • comparing electroantennogram and behavioral responses of two pseudacteon phorid fly species to body extracts of black red and hybrid imported Fire Ants solenopsis spp
    Journal of Insect Physiology, 2012
    Co-Authors: Xiaofang He, Samuel A Ochieng, Li Zi-chen, Henry Y. Fadamiro
    Abstract:

    Abstract Several phorid fly species were introduced to the southern United States for biological control of the invasive imported Fire Ants, Solenopsis richteri (Black), Solenopsis invicta (Red), and their Hybrid S. richteri × S. invicta (Hybrid). It has been previously reported that the Jaguariuna biotype of Pseudacteon tricuspis and the Formosan biotype of Pseudacteon curvatus could distinguish among the three Fire ant species with greater preference for Hybrid and Red Fire Ants. We hypothesized that phorid flies might use host derived chemical cues to differentiate ant species. To determine possible differential olfactory sensitivity of phorid fly species to different Fire ant species, we compared electroantennogram (EAG) and behavioral responses of both sexes of P. tricuspis and P. curvatus to body extracts of Black, Red and Hybrid Fire Ants. As worker sizes of Black and Hybrid Fire Ants used in this study were much larger than that of Red Fire ant (the average weight for Black, Red and Hybrid workers was 1.707, 0.863, 1.223 mg per Ants, respectively), at doses of 0.01, 0.1, 1 worker equivalent, body extracts of Black and Hybrid Fire ant elicited significantly greater EAG response in both sexes of P. tricuspis than that of Red Fire ant. Similarly, the EAG response in female P. curvatus to body extract of Black Fire ant was significantly greater than to body extract of Red Fire ant. To eliminate worker size influence on EAG response in phorid flies, we conducted a second EAG study using a dose of 1 mg ant equivalent (body extract from 1 mg of worker). No difference in EAG responses was recorded to body extract obtained from the same amount of workers among the three Fire ant species (we consider viable Hybrid Fire ant as a species in this paper), suggesting that worker size differences contributed to difference in EAG response in the first EAG study. In both EAG studies, male P. tricuspis showed significantly greater EAG responses than male P. curvatus to all three Fire ant species. In four-way olfactometer bioassay, worker body extracts of all three Fire ant species were equally attractive to P. tricuspis and P. curvatus (i.e. both phorid fly species did not show any preferences among the three Fire ant species). Together, the results of the EAG and behavior studies suggest that parasitic phorid flies utilize host derived non-polar compounds from worker Ants extracted out by hexane for host location but not for host preference, since both fly species are not able to distinguish among the body extracts of the three Fire ant species. Future study will investigate possible involvement of polar compounds and/or non-chemical cues in mediating host preference by phorid flies.

Dewayne Shoemaker - One of the best experts on this subject based on the ideXlab platform.

  • viral infections in Fire Ants lead to reduced foraging activity and dietary changes
    Scientific Reports, 2018
    Co-Authors: Dewayne Shoemaker, Hungwei Hsu, Mingchung Chiu, Chincheng Scotty Yang
    Abstract:

    Despite the presence of conserved innate immune function, many insects have evolved a variety of mechanical, chemical, and behavioral defensive responses to pathogens. Illness-induced anorexia and dietary changes are two behavioral defensive strategies found in some solitary insects, but little is known regarding the role of such behaviors in social insects, especially in Ants. In the present study we examined if such reduced foraging activity exists for a social insect, the invasive Fire ant Solenopsis invicta, and its viral pathogen, Solenopsis invicta virus 1 (SINV-1). Virus-free Fire ant colonies were split into two colony fragments, one of which subsequently was inoculated with SINV-1. Four food resources with different macronutrient ratios were presented to both colony fragments. SINV-1-inoculated colony fragments consistently displayed reduced foraging performance (e.g., foraging intensity and recruitment efficiency), a decline in lipid intake, and a shift in dietary preference to carbohydrate-rich foods compared with virus-free fragments. These findings provide the first evidence for virus-induced behavioral responses and dietary shifts in shaping the host-pathogen interactions in Fire Ants. The findings also suggest a possible mechanism for how Fire ant colonies respond to viral epidemics. Potential implications of these behavioral differences for current management strategies are discussed.

  • propagule pressure and colony social organization are associated with the successful invasion and rapid range expansion of Fire Ants in china
    Molecular Ecology, 2012
    Co-Authors: Chincheng Yang, Marina S Ascunce, Lizhi Luo, Jingguo Shao, Chengjen Shih, Dewayne Shoemaker
    Abstract:

    We characterized patterns of genetic variation in populations of the Fire ant Solenopsis invicta in China using mitochondrial DNA sequences and nuclear microsatellite loci to test predictions as to how propagule pressure and subsequent dispersal following establishment jointly shape the invasion success of this ant in this recently invaded area. Fire Ants in Wuchuan (Guangdong Province) are genetically differentiated from those found in other large infested areas of China. The immediate source of Ants in Wuchuan appears to be somewhere near Texas, which ranks first among the southern USA infested states in the exportation of goods to China. Most colonies from spatially distant, outlying areas in China are genetically similar to one another and appear to share a common source (Wuchuan, Guangdong Province), suggesting that long-distance jump dispersal has been a prevalent means of recent spread of Fire Ants in China. Furthermore, most colonies at outlier sites are of the polygyne social form (featuring multiple egg-laying queens per nest), reinforcing the important role of this social form in the successful invasion of new areas and subsequent range expansion following invasion. Several analyses consistently revealed characteristic signatures of genetic bottlenecks for S. invicta populations in China. The results of this study highlight the invasive potential of this pest ant, suggest that the magnitude of international trade may serve as a predictor of propagule pressure and indicate that rates and patterns of subsequent range expansion are partly determined by the interplay between species traits and the trade and transportation networks.

  • mitochondrial genome evolution in Fire Ants hymenoptera formicidae
    BMC Evolutionary Biology, 2010
    Co-Authors: Dietrich Gotzek, Jessica Clarke, Dewayne Shoemaker
    Abstract:

    Complete mitochondrial genome sequences have become important tools for the study of genome architecture, phylogeny, and molecular evolution. Despite the rapid increase in available mitogenomes, the taxonomic sampling often poorly reflects phylogenetic diversity and is often also biased to represent deeper (family-level) evolutionary relationships. We present the first fully sequenced ant (Hymenoptera: Formicidae) mitochondrial genomes. We sampled four mitogenomes from three species of Fire Ants, genus Solenopsis, which represent various evolutionary depths. Overall, ant mitogenomes appear to be typical of hymenopteran mitogenomes, displaying a general A+T-bias. The Solenopsis mitogenomes are slightly more compact than other hymentoperan mitogenomes (~15.5 kb), retaining all protein coding genes, ribosomal, and transfer RNAs. We also present evidence of recombination between the mitogenomes of the two conspecific Solenopsis mitogenomes. Finally, we discuss potential ways to improve the estimation of phylogenies using complete mitochondrial genome sequences. The ant mitogenome presents an important addition to the continued efforts in studying hymenopteran mitogenome architecture, evolution, and phylogenetics. We provide further evidence that the sampling across many taxonomic levels (including conspecifics and congeners) is useful and important to gain detailed insights into mitogenome evolution. We also discuss ways that may help improve the use of mitogenomes in phylogenetic analyses by accounting for non-stationary and non-homogeneous evolution among branches.

  • molecular phylogeny of Fire Ants of the solenopsis saevissima species group based on mtdna sequences
    Molecular Phylogenetics and Evolution, 2006
    Co-Authors: Dewayne Shoemaker, Michael E Ahrens, Kenneth G. Ross
    Abstract:

    The systematics of South American Fire Ants (Solenopsis saevissima species-group) has been plagued by difficulties in recognizing species and their relationships on the basis of morphological characters. We surveyed mtDNA sequences from 623 individuals representing 13 described and undescribed species within the species-group and 18 individuals representing other major Solenopsis lineages to generate a phylogeny of the mitochondrial genome. Our analyses support the monophyly of the S. saevissima species-group, consistent with a single Neotropical origin and radiation of this important group of Ants, as well as the monophyly of the socially polymorphic species within the group, consistent with a single origin of polygyny (multiple queens per colony) as a derived form of social organization. The mtDNA sequences of the inquiline social parasite S. daguerrei form a clade that appears to be distantly related to sequences from the several host species, consistent with the view that advanced social parasitism did not evolve via sympatric speciation of intraspecific parasites. An important general finding is that species-level polyphyly of the mtDNA appears to be the rule in this group of Ants. The existence of multiple divergent mtDNA lineages within several nominal species (including the pest S. invicta) suggests that the pattern of widespread polyphyly often stems from morphological delimitation that overcircumscribes species. However, in two cases the mtDNA polyphyly likely results from recent interspecific hybridization. While resolving species boundaries and relationships is important for understanding general patterns of diversification of South American Fire Ants, these issues are of added importance because invasive Fire Ants are emerging as global pests and becoming important model organisms for evolutionary research.

  • species delimitation in native south american Fire Ants
    Molecular Ecology, 2005
    Co-Authors: Kenneth G. Ross, Dewayne Shoemaker
    Abstract:

    The taxonomy of Fire Ants has been plagued by difficulties in recognizing species on the basis of morphological characters. We surveyed allozyme markers and sequences of the mtDNA COI gene in several closely related nominal species from two areas of sympatry in the native ranges to learn whether the morphology-based delimitation of these species is supported by genetic data. We found that Solenopsis invicta and Solenopsis richteri , pest species whose distinctiveness has been debated, appear to be fully reproductively isolated at both study sites. This isolation contrasts with the extensive hybridization occurring between them in the USA, where both have been introduced. We also found strong genetic differentiation consistent with barriers to gene flow between Solenopsis quinquecuspis and the other two species. However, several lines of evidence suggest that nuclear and mitochondrial genes of S. invicta and S. richteri are introgressing into S. quinquecuspis . The latter apparently is a recently derived member of the clade that includes all three species, suggesting that there has been insufficient time for its full development of intrinsic isolating mechanisms. Finally, our discovery of genetically distinct populations within both S. invicta and S. richteri suggests the presence of previously unrecognized (cryptic) species. Their existence, together with the difficulties in developing diagnostic morphological characters for described species, imply that the group is actively radiating species and that morphological divergence generally does not keep pace with the development of reproductive isolation and neutral genetic divergence in this process.

Henry Y. Fadamiro - One of the best experts on this subject based on the ideXlab platform.

  • pseudacteon phorid flies host specificity and impacts on solenopsis Fire Ants
    Annual Review of Entomology, 2018
    Co-Authors: Li Zi-chen, Henry Y. Fadamiro
    Abstract:

    Human commerce has resulted in the spread of the imported Fire Ants, Solenopsis species, worldwide. Six species of parasitic Pseudacteon phorid flies that are highly host specific to the Solenopsis saevissima complex of Solenopsis Fire Ants have been successfully released in the southern United States. The presence of Pseudacteon phorid flies, in addition to having direct mortality effects on their host Ants, modifies foraging behavior and disrupts interspecific competition between host species and other ant species in the community. Fire ant workers have evolved effective methods to cope with parasitism pressure, which may relieve population-level impacts of introduced phorid flies. This review focuses on the mechanisms underlying host location, host preference, and host-size selection of Pseudacteon phorid flies and highlights their direct and indirect effects on Fire ant populations. Knowledge gained from parasitoid–ant interactions will enhance use of natural enemies as biological control agents for i...

  • intra and inter specific variation in alarm pheromone produced by solenopsis Fire Ants
    Bulletin of Entomological Research, 2017
    Co-Authors: Rammohan R Balusu, Henry Y. Fadamiro, W Q Zhang, Olufemi S Ajayi, Rensen Zeng, Li Zi-chen
    Abstract:

    Some Fire Ants of the genus Solenopsis have become invasive species in the southern United States displacing native species by competition. Although the displacement pattern seems clear, the mechanisms underlying competitive advantage remain unclear. The ability of ant workers to produce relatively larger amount of alarm pheromone may correspond to relative greater fitness among sympatric Fire ant species. Here we report on quantitative intra-specific (i.e. inter-caste) and inter-specific differences of alarm pheromone component, 2-ethyl-3,6-dimethylpyrazine (2E36DMP), for several Fire ant species. The alarm pheromone component was extracted by soaking Ants in hexane for 48 h and subsequently quantified by gas chromatography-mass spectrometry at single ion monitoring mode. Solenopsis invicta workers had more 2E36DMP than male or female alates by relative weight; individual workers, however, contained significantly less pyrazine. We thus believe that alarm pheromones may serve additional roles in alates. Workers of Solenopsis richteri, S. invicta, and hybrid (S. richteri × S. invicta) had significantly more 2E36DMP than a native Fire ant species, Solenopsis geminata. The hybrid Fire ant had significantly less 2E36DMP than the two parent species, S. richteri and S. invicta. It seems likely that higher alarm pheromone content may have favored invasion success of exotic Fire Ants over native species. We discuss the potential role of inter-specific variation in pyrazine content for the relationship between the observed shifts in the spatial distributions of the three exotic Fire ant species in southern United States and the displacement of native Fire ant species.

  • quantitative analysis of alkaloidal constituents in imported Fire Ants by gas chromatography
    Journal of Agricultural and Food Chemistry, 2014
    Co-Authors: Hongyi Wei, Henry Y. Fadamiro, Li Zi-chen
    Abstract:

    A method based on silica gel chromatography and GC-MS/GC-FID analyses was developed for the quantitation of alkaloidal compounds in imported Fire Ants, Solenopsis richteri, S. invicta, and their hybrid found in the southern United States. The cis and trans alkaloids from Fire ant body extracts were successfully separated by silica gel chromatography, identified by GC-MS, and quantitated by GC-FID. Piperideine compounds were eluted together with the cis and trans piperidines, but were well-resolved on a nonpolar GC column. Eight pairs of piperidine isomers and 12 piperideines were quantitated. The ratios of trans alkaloids to corresponding cis isomers ranged from 87 to 378:1 in S. invicta and were significantly higher than in S. richteri and hybrid Ants. The results were discussed in relation to the evolution of Fire ant venom alkaloids and their role as host location cues for parasitic Pseudacteon phorid flies.

  • comparing electroantennogram and behavioral responses of two pseudacteon phorid fly species to body extracts of black red and hybrid imported Fire Ants solenopsis spp
    Journal of Insect Physiology, 2012
    Co-Authors: Xiaofang He, Samuel A Ochieng, Li Zi-chen, Henry Y. Fadamiro
    Abstract:

    Abstract Several phorid fly species were introduced to the southern United States for biological control of the invasive imported Fire Ants, Solenopsis richteri (Black), Solenopsis invicta (Red), and their Hybrid S. richteri × S. invicta (Hybrid). It has been previously reported that the Jaguariuna biotype of Pseudacteon tricuspis and the Formosan biotype of Pseudacteon curvatus could distinguish among the three Fire ant species with greater preference for Hybrid and Red Fire Ants. We hypothesized that phorid flies might use host derived chemical cues to differentiate ant species. To determine possible differential olfactory sensitivity of phorid fly species to different Fire ant species, we compared electroantennogram (EAG) and behavioral responses of both sexes of P. tricuspis and P. curvatus to body extracts of Black, Red and Hybrid Fire Ants. As worker sizes of Black and Hybrid Fire Ants used in this study were much larger than that of Red Fire ant (the average weight for Black, Red and Hybrid workers was 1.707, 0.863, 1.223 mg per Ants, respectively), at doses of 0.01, 0.1, 1 worker equivalent, body extracts of Black and Hybrid Fire ant elicited significantly greater EAG response in both sexes of P. tricuspis than that of Red Fire ant. Similarly, the EAG response in female P. curvatus to body extract of Black Fire ant was significantly greater than to body extract of Red Fire ant. To eliminate worker size influence on EAG response in phorid flies, we conducted a second EAG study using a dose of 1 mg ant equivalent (body extract from 1 mg of worker). No difference in EAG responses was recorded to body extract obtained from the same amount of workers among the three Fire ant species (we consider viable Hybrid Fire ant as a species in this paper), suggesting that worker size differences contributed to difference in EAG response in the first EAG study. In both EAG studies, male P. tricuspis showed significantly greater EAG responses than male P. curvatus to all three Fire ant species. In four-way olfactometer bioassay, worker body extracts of all three Fire ant species were equally attractive to P. tricuspis and P. curvatus (i.e. both phorid fly species did not show any preferences among the three Fire ant species). Together, the results of the EAG and behavior studies suggest that parasitic phorid flies utilize host derived non-polar compounds from worker Ants extracted out by hexane for host location but not for host preference, since both fly species are not able to distinguish among the body extracts of the three Fire ant species. Future study will investigate possible involvement of polar compounds and/or non-chemical cues in mediating host preference by phorid flies.

  • comparing electroantennogram and behavioral responses of two pseudacteon phorid fly species to body extracts of black red and hybrid imported Fire Ants solenopsis spp
    Journal of Insect Physiology, 2012
    Co-Authors: Xiaofang He, Samuel A Ochieng, Li Zi-chen, Henry Y. Fadamiro
    Abstract:

    Abstract Several phorid fly species were introduced to the southern United States for biological control of the invasive imported Fire Ants, Solenopsis richteri (Black), Solenopsis invicta (Red), and their Hybrid S. richteri × S. invicta (Hybrid). It has been previously reported that the Jaguariuna biotype of Pseudacteon tricuspis and the Formosan biotype of Pseudacteon curvatus could distinguish among the three Fire ant species with greater preference for Hybrid and Red Fire Ants. We hypothesized that phorid flies might use host derived chemical cues to differentiate ant species. To determine possible differential olfactory sensitivity of phorid fly species to different Fire ant species, we compared electroantennogram (EAG) and behavioral responses of both sexes of P. tricuspis and P. curvatus to body extracts of Black, Red and Hybrid Fire Ants. As worker sizes of Black and Hybrid Fire Ants used in this study were much larger than that of Red Fire ant (the average weight for Black, Red and Hybrid workers was 1.707, 0.863, 1.223 mg per Ants, respectively), at doses of 0.01, 0.1, 1 worker equivalent, body extracts of Black and Hybrid Fire ant elicited significantly greater EAG response in both sexes of P. tricuspis than that of Red Fire ant. Similarly, the EAG response in female P. curvatus to body extract of Black Fire ant was significantly greater than to body extract of Red Fire ant. To eliminate worker size influence on EAG response in phorid flies, we conducted a second EAG study using a dose of 1 mg ant equivalent (body extract from 1 mg of worker). No difference in EAG responses was recorded to body extract obtained from the same amount of workers among the three Fire ant species (we consider viable Hybrid Fire ant as a species in this paper), suggesting that worker size differences contributed to difference in EAG response in the first EAG study. In both EAG studies, male P. tricuspis showed significantly greater EAG responses than male P. curvatus to all three Fire ant species. In four-way olfactometer bioassay, worker body extracts of all three Fire ant species were equally attractive to P. tricuspis and P. curvatus (i.e. both phorid fly species did not show any preferences among the three Fire ant species). Together, the results of the EAG and behavior studies suggest that parasitic phorid flies utilize host derived non-polar compounds from worker Ants extracted out by hexane for host location but not for host preference, since both fly species are not able to distinguish among the body extracts of the three Fire ant species. Future study will investigate possible involvement of polar compounds and/or non-chemical cues in mediating host preference by phorid flies.

Lawrence E. Gilbert - One of the best experts on this subject based on the ideXlab platform.

  • The urban Fire ant paradox: native Fire Ants persist in an urban refuge while invasive Fire Ants dominate natural habitats
    Biological Invasions, 2007
    Co-Authors: Robert M. Plowes, J. Dunn, Lawrence E. Gilbert
    Abstract:

    In contrast to the widespread extirpation of native Fire Ants (Solenopsis geminata) across southern US following the invasion by imported red Fire Ants (S. invicta), some residential areas of Austin form unexpected refuges for native Fire Ants. Ironically, these urban environments provide refuges for the native Fire Ants while adjacent natural habitats have been overrun by invasive Fire Ants. Resistance to invasive Fire Ants in these urban areas occurs mainly in older residential properties constructed prior to the S. invicta invasion, while more recent construction has allowed establishment by S. invicta. The invasive ability of S. invicta is often attributed to escape from parasitoids and efficient dispersal of polygyne multiple queen colonies. Here we also show the importance of landscape parameters in the invasion process, where low levels of disturbance and continuous plant cover in older residential areas form possible barriers to colonization. Dense leaf cover (high NDVI) was also found to be associated with native ant refuges. Long term residential land ownership may have resulted in lower recent disturbance levels and increased plant cover that support refuges of native Fire Ants.

  • development of pseudacteon nocens diptera phoridae on solenopsis invicta and solenopsis richteri Fire Ants hymenoptera formicidae
    Journal of Economic Entomology, 2006
    Co-Authors: Patricia J Folgarait, Richard J W Patrock, Lawrence E. Gilbert
    Abstract:

    Abstract We studied the developmental performance of the large morph of Pseudacteon nocens Borgmeier (Diptera: Phoridae), a prospective biological control agent of imported Fire Ants (Hymenoptera: Formicidae). We measured selected life history traits of this parasitoid as a function of 1) host species (Solenopsis invicta Buren versus Solenopsis richteri Forel), 2) temperature (22 versus 28°C), 3) source population of the fly (Corrientes and Santiago del Estero, Argentina), and 4) varied size distributions of offered host Ants. Developmental periods were influenced by host species, although the populations responded in opposing manners. Developmental times, however, were most strongly influenced by temperature with total developmental periods lengthened by 17–32% at 22°C. Pupal mortality was also significantly lower at this temperature. Although numbers of progeny per female were significantly higher for the Corrientes population, we found no significant differences in progeny per female according to host ...

  • development of pseudacteon obtusus diptera phoridae on solenopsis invicta and solenopsis richteri Fire Ants hymenoptera formicidae
    Environmental Entomology, 2005
    Co-Authors: Patricia J Folgarait, Monica G Chirino, Richard J W Patrock, Lawrence E. Gilbert
    Abstract:

    We studied the developmental performance of the large biotype of Pseudacteon obtusus Borgmeier, a promising biological control agent of imported Fire Ants. We measured selected life history traits of this parasitoid as a function of (1) host species (Solenopsis invicta Buren versus Solenopsis richteri Forel), (2) temperature (22 versus 28°C), and (3) size distributions of available host Ants (big versus mixed-size classes of workers). Survivorship on S. invicta was much greater than that on S. richteri under most conditions. Developmental time was strongly influenced by temperature with total developmental periods shortened by 21–34% at the 6°C higher temperature treatment. However, developmental periods were weakly influenced by hosts across temperatures. We found that larval, pupal, and total developmental periods of this phorid fly were up to 6.2% longer on S. richteri than on S. invicta, although these periods depended on temperature. Total developmental time was slightly shorter (by 4.8%) on S. invicta than S. richteri at 22°C but longer (by 5.7%) on S. invicta at 28°C. The relationship between host size and sex of emerging flies contrasts with that of previously documented Pseudacteon species, in that males were produced from all host size classes while females only came from larger Ants. Sex ratios favor females when a mixture of ant size classes were offered in comparison to when only big Ants could be chosen. Pseudacteon obtusus seems to be a promising candidate for biological control releases in that in addition to its high host specificity, it develops better on red Fire Ants, attacks Ants on trails and mounds, and chooses a worker size range that complements the two other Pseudacteon species already released.

  • Colony-level impacts of parasitoid flies on Fire Ants.
    Proceedings. Biological sciences, 2002
    Co-Authors: Natasha J. Mehdiabadi, Lawrence E. Gilbert
    Abstract:

    The red imported Fire ant is becoming a global ecological problem, having invaded the United States, Puerto Rico, New Zealand and, most recently, Australia. In its established areas, this pest is devastating natural biodiversity. Early attempts to halt Fire ant expansion with pesticides actually enhanced its spread. Phorid fly parasitoids from South America have now been introduced into the United States as potential biological control agents of the red imported Fire ant, but the impact of these flies on Fire ant populations is currently unknown. In the laboratory, we show that an average phorid density of as little as one attacking fly per 200 foraging Ants decreased colony protein consumption nearly twofold and significantly reduced numbers of large-sized workers 50 days later. The high impact of a single phorid occurred mainly because Ants decreased foraging rates in the presence of the flies. Our experiments, the first (to our knowledge) to link indirect and direct effects of phorids on Fire Ants, demonstrate that colonies can be stressed with surprisingly low parasitoid densities. We interpret our findings with regard to the more complex Fire ant-phorid interactions in the field.

  • foraging ecology and patterns of diversification in dipteran parasitoids of Fire Ants in south brazil
    Ecological Entomology, 1997
    Co-Authors: Matthew R Orr, S H Seike, Lawrence E. Gilbert
    Abstract:

    1. At least sixteen species of parasitoid flies in the genus Pseudacteon (family Phoridae) attack Fire Ants in the Solenopsis saevissima subcomplex in South America. Little is known of behavioural or ecological differences among Pseudacteon parasitoids of Fire Ants, although their coexistence in multispecies communities would suggest that important differences exist. Seven Pseudacteon species in two separate communities were studied in south-east Brazil. The way in which hosts detect and respond to the presence of parasitoids, attack rates of the parasitoids, and host location behaviour of the parasitoids were examined. 2. Reductions in Fire ant recruitment were more closely related to the number of Ants attacked along a foraging trail than to the amount of time that a phorid was present. 3. Pseudacteon solenopsidis differed from other phorid species by flying backwards while pursuing Ants, by attacking at lower rates than other phorids, and by spending longer around Fire ant foraging trails than other phorids before departing. Fire ant recruitment to food often rebounded in the continued presence of P. solenopsidis. 4. In each of the two communities, certain Pseudacteon species appeared frequently at Solenopsis foraging trails, whereas others appeared predominantly at mound disturbances. Two distinct size classes of phorids were present in each community, and the community with the larger ant host species also had a third and larger phorid species. No phorid species from the same community had similar body sizes and similar host location behaviours, although numerous species from different communities shared both of these traits. 5. Heterogeneity in host size and in the ecological circumstances under which hosts are vulnerable to attack appears to have influenced the evolution and perhaps maintenance of diverse Pseudacteon communities.