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Phenotypic plasticity and modularity allow for the production of novel mosaic phenotypes in ants.

Londe S, Monnin T, Cornette R, Debat V, Fisher BL, Molet M - Evodevo (2015)

Bottom Line: In addition, we found that many other individuals traditionally classified as workers or queens also exhibit some level of mosaicism.Indeed, we found that most mosaics have queen-like head and gaster but a worker-like thorax congruent with the morphology of ergatoid queens and soldiers, respectively.Ergatoid queens of M. oberthueri, a sister species of M. rogeri, could have evolved from intercastes produced ancestrally through such a process.

View Article: PubMed Central - PubMed

Affiliation: UMR 7618 Institute of Ecology and Environmental Sciences of Paris, Sorbonne Universités, UPMC Univ Paris 06, 7 quai St Bernard, 75 252 Paris, France.

ABSTRACT

Background: The origin of discrete novelties remains unclear. Some authors suggest that qualitative phenotypic changes may result from the reorganization of preexisting phenotypic traits during development (i.e., developmental recombination) following genetic or environmental changes. Because ants combine high modularity with extreme phenotypic plasticity (queen and worker castes), their diversified castes could have evolved by developmental recombination. We performed a quantitative morphometric study to investigate the developmental origins of novel phenotypes in the ant Mystrium rogeri, which occasionally produces anomalous 'intercastes.' Our analysis compared the variation of six morphological modules with body size using a large sample of intercastes.

Results: We confirmed that intercastes are conspicuous mosaics that recombine queen and worker modules. In addition, we found that many other individuals traditionally classified as workers or queens also exhibit some level of mosaicism. The six modules had distinct profiles of variation suggesting that each module responds differentially to factors that control body size and polyphenism. Mosaicism appears to result from each module responding differently yet in an ordered and predictable manner to intermediate levels of inducing factors that control polyphenism. The order of module response determines which mosaic combinations are produced.

Conclusions: Because the frequency of mosaics and their canalization around a particular phenotype may evolve by selection on standing genetic variation that affects the plastic response (i.e., genetic accommodation), developmental recombination is likely to play an important role in the evolution of novel castes in ants. Indeed, we found that most mosaics have queen-like head and gaster but a worker-like thorax congruent with the morphology of ergatoid queens and soldiers, respectively. Ergatoid queens of M. oberthueri, a sister species of M. rogeri, could have evolved from intercastes produced ancestrally through such a process.

No MeSH data available.


Distribution of queen-likeness for each module between groups. Green queens; blue intercastes; red workers. Gray histograms represent total distribution without caste distinction. Queen-likeness of intercastes was different from and intermediate between queens and workers except for legs, which did not differ from queens
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Fig4: Distribution of queen-likeness for each module between groups. Green queens; blue intercastes; red workers. Gray histograms represent total distribution without caste distinction. Queen-likeness of intercastes was different from and intermediate between queens and workers except for legs, which did not differ from queens

Mentions: We compared queen-likeness distributions between groups according to a priori assignation. Queen-likeness was significantly different between queens and workers for each module, with an overlap for head, legs, and gaster (Fig. 4). Queen-likeness of intercastes was different from and intermediate between queens and workers (Kruskal–Wallis rank sum test: P < 10−6), with the exception of legs, which did not differ from those of queens (Chi2 = 0.44, P = 0.51). The three thoracic modules of intercastes were more similar to workers than to queens and overlapped with workers (Fig. 4). Workers were significantly more variable than queens for all modules (Bartlett test: P < 10−3) with the exception of pronotum (K2 = 0.12, P = 0.73) and mesonotum (K2 = 0.24, P = 0.62). Workers were also significantly more variable than intercastes (Bartlett test: P < 0.05) except for pronotum (K2 = 1.75, P = 0.19). Intercastes were more variable than queens for mesonotum and propodeum (Bartlett test: P < 10−6) but not other modules.Fig. 4


Phenotypic plasticity and modularity allow for the production of novel mosaic phenotypes in ants.

Londe S, Monnin T, Cornette R, Debat V, Fisher BL, Molet M - Evodevo (2015)

Distribution of queen-likeness for each module between groups. Green queens; blue intercastes; red workers. Gray histograms represent total distribution without caste distinction. Queen-likeness of intercastes was different from and intermediate between queens and workers except for legs, which did not differ from queens
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4666092&req=5

Fig4: Distribution of queen-likeness for each module between groups. Green queens; blue intercastes; red workers. Gray histograms represent total distribution without caste distinction. Queen-likeness of intercastes was different from and intermediate between queens and workers except for legs, which did not differ from queens
Mentions: We compared queen-likeness distributions between groups according to a priori assignation. Queen-likeness was significantly different between queens and workers for each module, with an overlap for head, legs, and gaster (Fig. 4). Queen-likeness of intercastes was different from and intermediate between queens and workers (Kruskal–Wallis rank sum test: P < 10−6), with the exception of legs, which did not differ from those of queens (Chi2 = 0.44, P = 0.51). The three thoracic modules of intercastes were more similar to workers than to queens and overlapped with workers (Fig. 4). Workers were significantly more variable than queens for all modules (Bartlett test: P < 10−3) with the exception of pronotum (K2 = 0.12, P = 0.73) and mesonotum (K2 = 0.24, P = 0.62). Workers were also significantly more variable than intercastes (Bartlett test: P < 0.05) except for pronotum (K2 = 1.75, P = 0.19). Intercastes were more variable than queens for mesonotum and propodeum (Bartlett test: P < 10−6) but not other modules.Fig. 4

Bottom Line: In addition, we found that many other individuals traditionally classified as workers or queens also exhibit some level of mosaicism.Indeed, we found that most mosaics have queen-like head and gaster but a worker-like thorax congruent with the morphology of ergatoid queens and soldiers, respectively.Ergatoid queens of M. oberthueri, a sister species of M. rogeri, could have evolved from intercastes produced ancestrally through such a process.

View Article: PubMed Central - PubMed

Affiliation: UMR 7618 Institute of Ecology and Environmental Sciences of Paris, Sorbonne Universités, UPMC Univ Paris 06, 7 quai St Bernard, 75 252 Paris, France.

ABSTRACT

Background: The origin of discrete novelties remains unclear. Some authors suggest that qualitative phenotypic changes may result from the reorganization of preexisting phenotypic traits during development (i.e., developmental recombination) following genetic or environmental changes. Because ants combine high modularity with extreme phenotypic plasticity (queen and worker castes), their diversified castes could have evolved by developmental recombination. We performed a quantitative morphometric study to investigate the developmental origins of novel phenotypes in the ant Mystrium rogeri, which occasionally produces anomalous 'intercastes.' Our analysis compared the variation of six morphological modules with body size using a large sample of intercastes.

Results: We confirmed that intercastes are conspicuous mosaics that recombine queen and worker modules. In addition, we found that many other individuals traditionally classified as workers or queens also exhibit some level of mosaicism. The six modules had distinct profiles of variation suggesting that each module responds differentially to factors that control body size and polyphenism. Mosaicism appears to result from each module responding differently yet in an ordered and predictable manner to intermediate levels of inducing factors that control polyphenism. The order of module response determines which mosaic combinations are produced.

Conclusions: Because the frequency of mosaics and their canalization around a particular phenotype may evolve by selection on standing genetic variation that affects the plastic response (i.e., genetic accommodation), developmental recombination is likely to play an important role in the evolution of novel castes in ants. Indeed, we found that most mosaics have queen-like head and gaster but a worker-like thorax congruent with the morphology of ergatoid queens and soldiers, respectively. Ergatoid queens of M. oberthueri, a sister species of M. rogeri, could have evolved from intercastes produced ancestrally through such a process.

No MeSH data available.