Divergent evolutionary pathways for aggression and territoriality in Astyanax cavefish

Abstract

The surface morph of the Mexican tetra fish (Astyanax mexicanus) exhibits strong territoriality behavior and high levels of aggression. In contrast, the eyeless cave-adapted morph from Sierra de El Abra, México, rarely are aggressive and have totally lost the territorial behavior. These behaviors are part of what has been called the cavefish behavioral syndrome. Here, we report that several Astyanax cave populations of Sierra de Guatemala, unlike those reported for the Sierra de El Abra cave populations, display significant territoriality and aggression when confined into a reduced space. We discuss divergent evolutionary trajectories in terms of agonistic behavior for cavefish populations inhabiting different mountain ranges.

Sensing in the dark: Constructive evolution of the lateral line system in blind populations of Astyanax mexicanus

“…Interestingly, when quantifying hair cell afferent neurotransmission across other cavefish populations, the authors found that Molino cavefish displayed an intermediate phenotype (Lunsford et al., 2022 ). This fits well with previous findings addressing other questions in A. mexicanus , where Molino cavefish have displayed intermediate phenotypes within physiological and behavioral contexts (Espinasa et al., 2022 ; Riddle et al., 2018 ; Rodriguez‐Morales et al., 2022 ; Xiong et al., 2018 ), and is another instance where ecological, cave‐specific contributions might be underlying cave‐trait variation.…”

“…Another behavior that evolved reductions in blind cavefish populations of the Mexican tetra is aggression (Parzefall & Hausberg, 2001). Previous work from others and I showed that multiple populations of A. mexicanus cavefish exhibit reductions in aggressive behaviors (Elipot et al, 2013;Espinasa et al, 2022;Rodriguez-Morales et al, 2022). Although one might think that not seeing another individual would eliminate social interactions, in A. mexicanus, surface fish remain aggressive when visually deprived, while blind Molino cavefish conserved aggressive behaviors (Rodriguez-Morales et al, 2022).…”

The nature and distribution of putative non-functional alleles suggest only two independent events at the origins of Astyanax mexicanus cavefish populations

“…At the phenotypic level, the partial complementation restoring sight in blind cavefish larvae after crosses between different cave populations [ 15 ], the loss of schooling behaviour that is very similar between Pachón and Tinaja but shows some differences in Molino [ 41 ], or the complete loss of aggressiveness in Sierra de El Abra populations but less so in Sierra de Guatemala populations [ 42 , 43 ] are also in favour of a common origin followed by independent evolution. Likewise, the observation that, among genes whose rhythmic expression is lost in at least one of three caves, 22% were arrhythmic in the three caves, was interpreted as evidence of repeated evolution of circadian clock dysregulation in independent populations [ 44 ].…”

The nature and distribution of non-functional alleles suggest only two independent events at the origins of Astyanax mexicanus cavefish populations

“…At the phenotypic level, the partial complementation restoring sight in blind cavefish larvae after crosses between different cave populations [13], the loss of schooling behaviour that is very similar between Pachón and Tinaja but shows some differences in Molino [38], or the complete loss of aggressiveness in Sierra de El Abra populations but less so in Sierra de Guatemala populations [39,40] are also in favour of a common origin followed by independent evolution. Likewise, the observation that, among genes whose rhythmic expression is lost in at least one of three caves, 22% were arrhythmic in the three caves, was interpreted as evidence of repeated evolution of circadian clock dysregulation in independent populations [41].…”