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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.


Morphology of a queen (a) and a worker (b) of Mystrium rogeri. Queens are larger than workers. The thorax of a queen is enlarged and made of distinct subunits, whereas the thorax of a worker is fused. Queens have three ocelli, whereas workers have none. Queens have a relatively larger gaster. LT and WG: length of tibia and width of gaster. c Digitalized outlines and semi-landmarks after sliding for queens (green circles) and worker (red circles). The differences in head morphology between both castes have been amplified by 10 %
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Fig2: Morphology of a queen (a) and a worker (b) of Mystrium rogeri. Queens are larger than workers. The thorax of a queen is enlarged and made of distinct subunits, whereas the thorax of a worker is fused. Queens have three ocelli, whereas workers have none. Queens have a relatively larger gaster. LT and WG: length of tibia and width of gaster. c Digitalized outlines and semi-landmarks after sliding for queens (green circles) and worker (red circles). The differences in head morphology between both castes have been amplified by 10 %

Mentions: We worked on six developmental modules corresponding to anatomical structures developing from distinct tagma, metameres, or imaginal disks during ontogeny. We took 2D measurements on four modules (head capsule, pronotum, mesonotum, and propodeum) and linear measurements on two modules (length of tibia and width of gaster). These modules are relevant for our investigation because they are rigid, unarticulated, and dimorphic between winged queens and workers (Fig. 2). Combining 2D and linear modules in the same analyses is not a problem because we did not compare shapes and sizes directly. Instead, we computed a dimensionless index of polyphenism as our main variable (see “queen-likeness index” here after).Fig. 2


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)

Morphology of a queen (a) and a worker (b) of Mystrium rogeri. Queens are larger than workers. The thorax of a queen is enlarged and made of distinct subunits, whereas the thorax of a worker is fused. Queens have three ocelli, whereas workers have none. Queens have a relatively larger gaster. LT and WG: length of tibia and width of gaster. c Digitalized outlines and semi-landmarks after sliding for queens (green circles) and worker (red circles). The differences in head morphology between both castes have been amplified by 10 %
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig2: Morphology of a queen (a) and a worker (b) of Mystrium rogeri. Queens are larger than workers. The thorax of a queen is enlarged and made of distinct subunits, whereas the thorax of a worker is fused. Queens have three ocelli, whereas workers have none. Queens have a relatively larger gaster. LT and WG: length of tibia and width of gaster. c Digitalized outlines and semi-landmarks after sliding for queens (green circles) and worker (red circles). The differences in head morphology between both castes have been amplified by 10 %
Mentions: We worked on six developmental modules corresponding to anatomical structures developing from distinct tagma, metameres, or imaginal disks during ontogeny. We took 2D measurements on four modules (head capsule, pronotum, mesonotum, and propodeum) and linear measurements on two modules (length of tibia and width of gaster). These modules are relevant for our investigation because they are rigid, unarticulated, and dimorphic between winged queens and workers (Fig. 2). Combining 2D and linear modules in the same analyses is not a problem because we did not compare shapes and sizes directly. Instead, we computed a dimensionless index of polyphenism as our main variable (see “queen-likeness index” here after).Fig. 2

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.