Transgressive aggression in Sceloporus hybrids confers fitness through advantages in male agonistic encounters

• Published in: The Journal of animal ecology 2010, Vol.79 (1), p.137-147
• Main Authors: Robbins, Travis R., Pruitt, Jonathan N., Straub, Lorelei E., Mccoy, Earl D., Mushinsky, Henry R.
• Format: Article
• Language: English
• Subjects: Aggression - physiology; Aggressiveness; Amphibia. Reptilia; Animal and plant ecology; Animal ecology; Animal, plant and microbial ecology; Animals; Behavior, Animal - physiology; Biological and medical sciences; Ecological genetics; ecological isolation; Evolutionary Ecology; extreme phenotype; Female; Fundamental and applied biological sciences. Psychology; General aspects; Habitats; heterosis; homoploid hybrid speciation; Human ecology; hybrid vigour; Hybridity; Hybridization; Hybridization, Genetic; Lizards; Lizards - genetics; Lizards - physiology; Male; Male animals; Mating behavior; Phenotypes; Reptiles & amphibians; Size; Species; Species Specificity; squamates; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Wildlife ecology
• ISSN: 0021-8790; 1365-2656
• DOI: 10.1111/j.1365-2656.2009.01594.x

1. We investigated agonistic behaviour and associated characteristics of Sceloporus woodi (Florida scrub lizard), Sceloporus undulatus (Eastern fence lizard) and their hybrids using staged territorial encounters. 2. These Sceloporus hybrids exhibit transgressive aggression and transgressive head-girth relative to the parental species and the transgressive aggression was specifically associated with an advantage in agonistic encounters. Our results suggest a hybrid advantage in natural habitats when defending and invading territories against either parental species. 3. We further analysed general advantages in agonistic encounters across the entire three-group system to elucidate characteristics that may be advantageous under specific circumstances. Individuals with larger body size (SVL) and greater aggression had an overall advantage in agonistic encounters; however, smaller individuals could win when slightly more aggressive and fatter, and less aggressive individuals could win when slightly larger, especially with greater head-girth. 4. The extreme hybrid phenotypes likely occurred through transgressive segregation, which has been implicated as a process through which homoploid, hybrid speciation can occur. Some form of ecological divergence is necessary, however, to impede parental gene flow. Our data suggest that ecological divergence could manifest in territorial species through transgressive aggression.