Size rather than complexity of sexual ornaments prolongs male metamorphosis and explains sexual size dimorphism in sepsid flies. Issue 1998 (10th May 2023)

• Record Type: Journal Article
• Authors: Rajaratnam, Gowri; Lui, Gerald; Su, Kathy F. Y.; Chew, Martin S. J.; Ang, Yuchen; Puniamoorthy, Nalini; Rohner, Patrick T.; Blanckenhorn, Wolf U.; Meier, Rudolf
• Is Part Of: Proceedings. Volume 290:Issue 1998(2023)
• Publication Date: 2023-05-10
• Subjects: metamorphosis -- sexual ornaments -- development time -- sexual dimorphism -- growth -- secondary sexual trait complexity; Biology -- Periodicals; 570.5
• DOI: 10.1098/rspb.2022.2531
• Languages: English
• ISSNs: 0962-8452

Abstract

Abstract : Male sexual ornaments often evolve rapidly and are thought to be costly, thus contributing to sexual size dimorphism. However, little is known about their developmental costs, and even less about costs associated with structural complexity. Here, we quantified the size and complexity of three morphologically elaborate sexually dimorphic male ornaments that starkly differ across sepsid fly species (Diptera: Sepsidae): (i) male forelegs range from being unmodified, like in most females, to being adorned with spines and large cuticular protrusions; (ii) the fourth abdominal sternites are either unmodified or are converted into complex de novo appendages; and (iii) male genital claspers range from small and simple to large and complex (e.g. bifurcated). We tracked the development of 18 sepsid species from egg to adult to determine larval feeding and pupal metamorphosis times of both sexes. We then statistically explored whether pupal and adult body size, ornament size and/or ornament complexity are correlated with sex-specific development times. Larval growth and foraging periods of male and female larvae did not differ, but the time spent in the pupal stage was ca 5% longer for sepsid males despite emerging 9% smaller than females on average. Surprisingly, we found no evidence that sexual trait complexity prolongs pupal development beyond some effects of trait size. Evolving more complex traits thus does not incur developmental costs at least in this system.