Article

Evolution of reproductive morphology among recently diverged taxa in the Drosophila mojavensis species cluster

Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, California 92093.
Ecology and Evolution (Impact Factor: 2.32). 02/2012; 2(2):397-408. DOI: 10.1002/ece3.93
Source: PubMed

ABSTRACT

The morphological evolution of sexual traits informs studies of speciation due to the potential role of these characters in reproductive isolation. In the current study, we quantified and compared genitalic variation within the Drosophila mojavensis species cluster to infer the mode of evolution of the male aedeagus. This system is ideal for such studies due to the opportunity to test and compare levels of variation along a divergence continuum at various taxonomic levels within the group. Shape variation was quantified using elliptic Fourier descriptors and compared among the four D. mojavensis host races, and between D. mojavensis and its sister species Drosophila arizonae. Aedeagus shape was diagnostic for D. arizonae, and among three of the four D. mojavensis subspecies. In each of these cases, there was less variation within subspecies than among subspecies, which is consistent with the pattern predicted if genitalia are evolving according to a punctuated change model, and are involved with mate recognition. However, aedeagus shape in Drosophila mojavensis sonorensis was highly variable and broadly overlapping with the other three subspecies, suggesting aedeagus evolution in this subspecies is more complex and subject to additional evolutionary factors. These results are interpreted and discussed in the context of selection on mate recognition systems and the potential for failed copulation.

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    • "Genital adaptations that confer upon males a competitive advantage may consequently reduce female fitness (Arnqvist & Rowe, 2005) and lead to sexually antagonistic coevolution between male and female morphologies (Arnqvist & Rowe, 2002a,2002b; Rönn et al., 2007; Tatarnic & Cassis, 2010). Although genital characters are ubiquitous taxonomic tools and used heavily in constructing phylogenetic relationships, the independent mapping of genital traits onto molecular phylogenies is less common, but has been highlighted in several recent studies (Richmond et al., 2012; Wojcieszek & Simmons, 2012; Yassin & Orgogozo, 2013). Mapping divergent genital morphologies onto molecular phylogenies can allow ancestral states to be reconstructed, and allow one to assess the likelihood of independent or convergent evolution of specific genital characters (Barmina & Kopp, 2007; Scharer et al., 2011). "
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    • "Thorax length is a significant life history trait, given its correlation with other characteristics such as flight performance, stress resistance, ovariole number (which is correlated with lifetime fecundity) and mating success (Markow and Ricker 1992; Azevedo et al. 1998; Hoffmann et al. 2001; Mangan 1978). Several morphological and pigmentation differences have been identified across all four host races, most notably divergence in features of the male genitalia such as the shape of the aedeagus (Richmond et al. 2012; Pfeiler et al. 2009). Overall, D. mojavensis is highly resistant to water stress relative to other Drosophila (Gibbs et al. 2003; Gibbs and Matzkin 2001; Matzkin et al. 2009), but yet significant differences in desiccation resistance exist between Catalina, Baja California and Sonora populations (Rajpurohit et al. 2013; Matzkin et al. 2007). "
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    • "Studies involving members of the repleta group have shown that females have high FRRs (Markow 1996; Bundgaard & Barker 2000; Good et al. 2006) and extremely rapid evolutionary rates of some reproductive tract proteins (Wagstaff & Begun 2005; Kelleher et al. 2011). In addition, it has been established that male genital morphology exhibits rapid adaptive evolution in Drosophila mojavensis (Richmond et al. 2012) and Drosophila buzzatii (Soto et al. 2013). Recently, Hurtado & Hasson (2013) found that female latency to remating is 14 times shorter in D. buzzatii than in D. koepferae, which suggests that female remating frequency and SC opportunities are quite higher in D. buzzatii. "
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