Evolutionary transitions in specialised mating strategies of Nephila spiders - adaption and constraint
Final Report Abstract
To summarize our achievements, we have won valuable and novel insights into the complex mating strategies of Nephila spiders and into the factors that determine which behavioural strategy a male will adopt and how this relates to size. Furthermore, we were able to advance our knowledge on developmental plasticity and information use of these spiders. The comparison of a monogynous with a polygynous species contradicted most of our predictions. We have to reconsider the assumption that polygyny evolved together with alternative options of female monopolization such as seminal substances that reduce female receptivity or mate guarding. Field data suggest that male competition might be relaxed in the polygynous species, which would mean that males no longer need to invest into preventing sperm competition. The project was also characterized by several surprises which sparked new questions and research directions. Most importantly, we discovered a strong female bias in some matrilines in the laboratory most likely caused by selfish elements (Wolbachia) and we will follow up this line of research. Perhaps this is the true reason behind the low male numbers in the field and the mating system switch. This first documentation of sex-ratio bias in Nephila sheds a completely new light on population dynamics and the evolution of mating systems in this spider genus.
Publications
- 2011. Spider males adjust mate choice but not sperm allocation to cues of a rival. Ethology, 117: 970-978
Schneider J.M., Lucass C., Brandler W., & L. Fromhage
- 2015. Differential investment and size-related mating strategies in contesting male spiders (Nephila senegalensis) facilitate extreme male size variation through balanced paternity returns. Animal Behaviour 101: 107-115
Neumann R. & J.M. Schneider
(See online at https://doi.org/10.1016/j.anbehav.2014.12.027) - Socially cued developmental plasticity in web-building spiders. BMC Evolutionary Biology, 2016, 16:170
Neumann R. & J.M. Schneider
(See online at https://doi.org/10.1186/s12862-016-0736-7) - Transition from monogyny to polygyny in Nephila senegalensis (Araneae: Nephilidae) is not accompanied by increased investment in sperm. Biological Journal of the Linnean Society, Volume 119, Issue 4, 1 December 2016, Pages 1027–1035
Preik O., Schneider J.M., Uhl G. & P. Michalik
(See online at https://doi.org/10.1111/bij.12863)
