Understanding the role of the ecological and social environment in the evolution of complex communication in peacock spiders

A project undertaken at the School of Biological, Earth and Environmental Sciences, University of New South Wales, and supervised by Michael Kasumovic

Males use a variety of signals to attract and persuade females to mate. In a perfect world, information would be passed seamlessly between individuals such that receivers have complete knowledge of the information sent by a signaller. This would allow receivers to perfectly judge the quality of signallers allowing them to select only the best mates. Ecological and social environments, however, can affect how signals are transmitted, and therefore, received. For example, ecological complexities in lighting patterns can alter how colour is perceived by receivers, while different substrates (e.g., leaves, branches) can alter how vibrations are attenuated and the strength at which they reach a receiver.


This complex signalling environment is hypothesized as the explanation for the unimodal specialization of communication tactics seen in most species. Despite this specialization, some species demonstrate complex signals where multiple modalities are incorporated (exemplified by visual and auditory displays of birds-of-paradise). This evolution questions (a) what factors are necessary to overcome the costs associated with multimodal signalling and (b) whether such signalling patterns cause more rapid speciation rates. Our understanding of the evolution of multimodal signalling, however, is hampered by the fact that studies often focus on single representative species within a genus in a single habitat type. This results in the inability to distinguish between social and ecological factors driving multimodal signal evolution. In addition, without the comparison of multiple species within a genus, it is impossible to ascertain whether it is signal complexity or the specific social or ecological factors that are driving the rapid speciation.


To remedy this, we use the spider genus Maratus; a group that is endemic to Australia. Males of this genus produce vibrational songs while simultaneously displaying brightly coloured ornamented flaps on their abdomen during courtship, leading to their common name of peacock spiders. Peacock spiders are very diverse (over 40 species), exhibit a variety of forms and behaviours from drab to remarkable, and are found in a variety of habitats throughout Australia. This genus thus provides an excellent opportunity to understanding the relative importance of ecological and social environments in shaping multimodal signalling, thereby providing unparalleled insight into the evolution of complex multimodal signals.


This project has three main objectives. (1) To determine the functional role of each modality (vibrational and visual) plays in multimodal signals. (2) To understand the relative importance of ecological and social environments in shaping multimodal evolution.  (3) To gain a better understanding of the spider genus Maratus, a largely undescribed genus endemic to Australia.


Since the description of M. volans in the literature, interest in spiders in general and peacock spiders specifically has exploded in the media. This is a unique opportunity to increase the awareness of endemic invertebrates to the general public and emphasizing the importance of habitat conservation as it leads to the identification of new and exciting species.

Popular Science Publications

YouTube video link of the courtship dance of Maratus volans: http://www.youtube.com/watch?v=sUypt5lMYUo

"The Conversation", December 2, 2015, click here

Publications

Girard, M.B., Elias, D.O, and Kasumovic, M.M. (2015). Female preference for multi-modal courtship: Multiple signals are important for male mating success in peacock spiders. Proc. R. Soc. B 282: 20152222. http://dx.doi.org/10.1098/rspb.2015.2222

 

 


 


Figure 1. Some of the many species of the Genus Maratus examined in this study. All photos © Madeline Girard. (Click on images to enlarge)