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Intrasexual selection predicts the evolution of signal complexity in lizards
T J Ord1, D T Blumstein, C S Evans
1Department of Biological Sciences, Macquarie University, Sydney, NSW, Australia. terry@galliform.psy.mq.edu.au
Proceedings. Biological Sciences
|April 26, 2001
Summary
Intrasexual selection, or competition among same-sex individuals, drives the evolution of complex animal signals and sexual size dimorphism (SSD). This study provides the first evidence linking signal complexity and SSD, highlighting a key role for male-male competition in communication evolution.
Area of Science:
- Evolutionary biology
- Animal behavior
- Communication systems
Background:
- Sexual selection explains many adaptations for mating success, with female mate choice (intersexual selection) well-studied.
- The role of same-sex competition (intrasexual selection) in shaping animal signals is less understood.
- Sexual size dimorphism (SSD) often results from intense male-male competition.
Purpose of the Study:
- To investigate the coevolution of signal complexity and sexual size dimorphism (SSD).
- To determine if complex signals are associated with SSD in extant species.
- To explore historical patterns of signal complexity evolution in relation to pre-existing size dimorphism.
Main Methods:
- Employed two complementary comparative methods.
- Analyzed relationships between signal complexity and SSD across species.
- Examined phylogenetic patterns of signal complexity evolution.
Main Results:
- Found a significant association between complex signals and SSD in extant species.
- Demonstrated that historical increases in signal complexity occurred in clades with high pre-existing size dimorphism.
- Provided the first evidence for the coevolution of signal complexity and SSD.
Conclusions:
- Intrasexual selection, particularly male-male competition, plays a crucial role in the evolution of signal complexity.
- Complex signals may have evolved to enhance opponent assessment during male-male competition.
- Intrasexual selection is a significant, previously underestimated driver of communication system evolution.