Limits...
Evolution of male genitalia: environmental and genetic factors affect genital morphology in two Drosophila sibling species and their hybrids.

Soto IM, Carreira VP, Fanara JJ, Hasson E - BMC Evol. Biol. (2007)

Bottom Line: Though genitalic size and shape variation have a significant genetic component in both species, shape varied across host cacti only in D. buzzatii.Such plastic expression of genital shape is the first evidence of the effect of rearing substrate on genitalic morphology in Drosophila.Our results suggest the evolution of different developmental networks after interspecific divergence and the existence of a complex genetic architecture, involving genetic factors with major effects affecting genital morphology.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina. soto@ege.fcen.uba.ar

ABSTRACT

Background: The rapid evolution of genital morphology is a fascinating feature that accompanies many speciation events. However, the underlying patterns and explanatory processes remain to be settled. In this work we investigate the patterns of intraspecific variation and interspecific divergence in male genitalic morphology (size and shape) in the cactophilic sibling species Drosophila buzzatii and D. koepferae. Genital morphology in interspecific hybrids was examined and compared to the corresponding parental lines.

Results: Despite of being siblings, D. buzzatii and D. koepferae showed contrasting patterns of genital morphological variation. Though genitalic size and shape variation have a significant genetic component in both species, shape varied across host cacti only in D. buzzatii. Such plastic expression of genital shape is the first evidence of the effect of rearing substrate on genitalic morphology in Drosophila. Hybrid genital morphology was not intermediate between parental species and the morphological resemblance to parental strains was cross-dependent.

Conclusion: Our results suggest the evolution of different developmental networks after interspecific divergence and the existence of a complex genetic architecture, involving genetic factors with major effects affecting genital morphology.

Show MeSH
Aedeagus morphology. Lateral aspect of the intromittent organ in Drosophila koepferae and D. buzzatii (modified with permission from [6]). Shaded areas represent the portion excluded from the shape quantification (See [6] for details of the morphology of male genitalia).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC1878482&req=5

Figure 5: Aedeagus morphology. Lateral aspect of the intromittent organ in Drosophila koepferae and D. buzzatii (modified with permission from [6]). Shaded areas represent the portion excluded from the shape quantification (See [6] for details of the morphology of male genitalia).

Mentions: As shown in Figure 5 there are conspicuous differences in aedeagus morphology between D. buzzatii and D. koepferae that preclude the possibility of determining an adequate number of reliable homologous landmarks. However, the aedeagus is a flat quitinous organ that can be effectively described in shape and size in two dimensions when flattened under a cover slip. Consequently, we decided to employ an approach based on elliptic Fourier descriptors (EFDs) [56] as a proper resolution to the problem of shape quantification [47]. This is a type of analysis in which differences in x and y coordinates of the outline of the studied organ are fit separately as functions of arc length by Fourier analysis, so that the outline can be decomposed into a weighted sum of sine and cosine functions designated as harmonics. Outlines from digital images were used to obtain Fourier coefficients for a polynomial function of 30th degree which were computed with SHAPE v1.2 package, [57] using Elliptic Fourier analysis [56,58,59]. For the quantification of organs' shape we only considered the distal part of the aedeagus excluding the apodeme and the gonopods (Shaded areas in Figure 1. Thus, we simplified the studied contour by taking into account only the portion of the organ effectively involved in the penetration of female genitalia.


Evolution of male genitalia: environmental and genetic factors affect genital morphology in two Drosophila sibling species and their hybrids.

Soto IM, Carreira VP, Fanara JJ, Hasson E - BMC Evol. Biol. (2007)

Aedeagus morphology. Lateral aspect of the intromittent organ in Drosophila koepferae and D. buzzatii (modified with permission from [6]). Shaded areas represent the portion excluded from the shape quantification (See [6] for details of the morphology of male genitalia).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1878482&req=5

Figure 5: Aedeagus morphology. Lateral aspect of the intromittent organ in Drosophila koepferae and D. buzzatii (modified with permission from [6]). Shaded areas represent the portion excluded from the shape quantification (See [6] for details of the morphology of male genitalia).
Mentions: As shown in Figure 5 there are conspicuous differences in aedeagus morphology between D. buzzatii and D. koepferae that preclude the possibility of determining an adequate number of reliable homologous landmarks. However, the aedeagus is a flat quitinous organ that can be effectively described in shape and size in two dimensions when flattened under a cover slip. Consequently, we decided to employ an approach based on elliptic Fourier descriptors (EFDs) [56] as a proper resolution to the problem of shape quantification [47]. This is a type of analysis in which differences in x and y coordinates of the outline of the studied organ are fit separately as functions of arc length by Fourier analysis, so that the outline can be decomposed into a weighted sum of sine and cosine functions designated as harmonics. Outlines from digital images were used to obtain Fourier coefficients for a polynomial function of 30th degree which were computed with SHAPE v1.2 package, [57] using Elliptic Fourier analysis [56,58,59]. For the quantification of organs' shape we only considered the distal part of the aedeagus excluding the apodeme and the gonopods (Shaded areas in Figure 1. Thus, we simplified the studied contour by taking into account only the portion of the organ effectively involved in the penetration of female genitalia.

Bottom Line: Though genitalic size and shape variation have a significant genetic component in both species, shape varied across host cacti only in D. buzzatii.Such plastic expression of genital shape is the first evidence of the effect of rearing substrate on genitalic morphology in Drosophila.Our results suggest the evolution of different developmental networks after interspecific divergence and the existence of a complex genetic architecture, involving genetic factors with major effects affecting genital morphology.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina. soto@ege.fcen.uba.ar

ABSTRACT

Background: The rapid evolution of genital morphology is a fascinating feature that accompanies many speciation events. However, the underlying patterns and explanatory processes remain to be settled. In this work we investigate the patterns of intraspecific variation and interspecific divergence in male genitalic morphology (size and shape) in the cactophilic sibling species Drosophila buzzatii and D. koepferae. Genital morphology in interspecific hybrids was examined and compared to the corresponding parental lines.

Results: Despite of being siblings, D. buzzatii and D. koepferae showed contrasting patterns of genital morphological variation. Though genitalic size and shape variation have a significant genetic component in both species, shape varied across host cacti only in D. buzzatii. Such plastic expression of genital shape is the first evidence of the effect of rearing substrate on genitalic morphology in Drosophila. Hybrid genital morphology was not intermediate between parental species and the morphological resemblance to parental strains was cross-dependent.

Conclusion: Our results suggest the evolution of different developmental networks after interspecific divergence and the existence of a complex genetic architecture, involving genetic factors with major effects affecting genital morphology.

Show MeSH