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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.


Consequence of the distinct profiles of variation among modules (a) on mosaicism (b). a Profiles of variation as a function of individual body length for the six modules. b Mosaicism as a function of individual body length for each individual (green squares queens; blue triangles intercastes; red circles workers). Mosaicism was low for both low and high body length, i.e., when all modules either showed a low or a high queen-likeness. As individual body length increased up to intermediate values, mosaicism increased from workers to intercastes (as expected from Fig. 1). There was no quantitative difference in mosaicism between the largest workers and intercastes
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Fig6: Consequence of the distinct profiles of variation among modules (a) on mosaicism (b). a Profiles of variation as a function of individual body length for the six modules. b Mosaicism as a function of individual body length for each individual (green squares queens; blue triangles intercastes; red circles workers). Mosaicism was low for both low and high body length, i.e., when all modules either showed a low or a high queen-likeness. As individual body length increased up to intermediate values, mosaicism increased from workers to intercastes (as expected from Fig. 1). There was no quantitative difference in mosaicism between the largest workers and intercastes

Mentions: The six modules had distinct profiles of variation (Fig. 5, 6a). Two types of profiles of variation could be distinguished graphically. As individual body length increases, queen-likeness of pronotum, mesonotum, and propodeum forms a long plateau at low values, and then increases late and suddenly to a plateau at high values. In contrast, queen-likeness of head, legs, and gaster increases earlier, at low values, and climbs continuously to plateau at high values. The two modules with the most divergent pattern were mesonotum and legs. The relative shape of their profiles of variation suggests that intercastes with an intermediate body length should have a worker-like mesonotum and queen-like legs. The transition points of the fitted parametric functions occurred at different body lengths among modules (pairwise comparisons on bootstrap distributions: P < 10−6) except for pronotum vs. mesonotum (P = 0.93) and head vs. gaster (P = 0.33). When body length increased, modules switched from worker-like to queen-like in the following sequence: legs, then gaster and head, then propodeum, and finally mesonotum and pronotum (Fig. 7).Fig. 5


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)

Consequence of the distinct profiles of variation among modules (a) on mosaicism (b). a Profiles of variation as a function of individual body length for the six modules. b Mosaicism as a function of individual body length for each individual (green squares queens; blue triangles intercastes; red circles workers). Mosaicism was low for both low and high body length, i.e., when all modules either showed a low or a high queen-likeness. As individual body length increased up to intermediate values, mosaicism increased from workers to intercastes (as expected from Fig. 1). There was no quantitative difference in mosaicism between the largest workers and intercastes
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4666092&req=5

Fig6: Consequence of the distinct profiles of variation among modules (a) on mosaicism (b). a Profiles of variation as a function of individual body length for the six modules. b Mosaicism as a function of individual body length for each individual (green squares queens; blue triangles intercastes; red circles workers). Mosaicism was low for both low and high body length, i.e., when all modules either showed a low or a high queen-likeness. As individual body length increased up to intermediate values, mosaicism increased from workers to intercastes (as expected from Fig. 1). There was no quantitative difference in mosaicism between the largest workers and intercastes
Mentions: The six modules had distinct profiles of variation (Fig. 5, 6a). Two types of profiles of variation could be distinguished graphically. As individual body length increases, queen-likeness of pronotum, mesonotum, and propodeum forms a long plateau at low values, and then increases late and suddenly to a plateau at high values. In contrast, queen-likeness of head, legs, and gaster increases earlier, at low values, and climbs continuously to plateau at high values. The two modules with the most divergent pattern were mesonotum and legs. The relative shape of their profiles of variation suggests that intercastes with an intermediate body length should have a worker-like mesonotum and queen-like legs. The transition points of the fitted parametric functions occurred at different body lengths among modules (pairwise comparisons on bootstrap distributions: P < 10−6) except for pronotum vs. mesonotum (P = 0.93) and head vs. gaster (P = 0.33). When body length increased, modules switched from worker-like to queen-like in the following sequence: legs, then gaster and head, then propodeum, and finally mesonotum and pronotum (Fig. 7).Fig. 5

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.