It’s clear that urbanization alters native animal and plant communities around the world. However, while some organisms become locally extinct as anthropogenic forces change the land, other species survive or even thrive in this urban landscape. A recent paper by George Perry reviews several cases of human behavior impacting the genetics of urban organisms. For example, we know that human-built landscapes can cause shifts in functional morphology (e.g. urban lizards have longer limbs and stickier toe pads, urban birds have pointier wings, and urban stream fish have more streamlined bodies). Additionally, selection pressures caused by hunting and fishing can lead to changes in body mass. In this review, Perry specifically looks at cases of behavioral adaptation in urban organisms in response to human behavior.
Case Study: Bird Feeders
Bird feeders are common in urban and suburban landscapes, allowing people to attract local avian wildlife and connect with nature. In the United Kingdom, researchers have shown that two bird taxa, Central European Blackcaps (Sylvia atricapilla) and Great Tits (Parus major) have longer bills that allow them to exploit bird feeders. The bill morphology is known to be linked to a collagen gene (COL4A5) and individual birds with longer bills that were homozygous for COL4A5 long-bill haplotype spent more time at bird feeders than those without the long-bill haplotype.
Case Study: Mosquito Nets
Another potential behavioral adaptation comes from a 4-year study in Paupa New Guinea where the mosquito (Anopheles farauti) was shown to increase bite rates in the early evening hours. This increase in early evening bite rates occurred in conjunction with the nationwide distribution of insecticidal nets that are placed over beds while sleeping. While it is unknown if this behavioral shift is genetic, the link between mosquito behavior and genetics has large implications for public health.
Case Study: Translocation of Non-endemic Fire Ants
In the 1940’s the fire ant (Solenopsis invicta) was introduced to the southeastern United States. This ant uses its venomous sting to capture prey and defend itself. Ground nesting birds are particularly vulnerable to fire ant attacks as well as the Eastern Fence Lizard (Sceloporus undulatus). Eastern Fence Lizards that co-exist with fire ants have longer hindlimbs and twitch more — a combined morphological and behavioral response to remove fire ants. While it is not known if the twitching behavior, is genetically controlled, this response clearly benefits survival.
Case Study: Flight Initiation Distance in Black Swans
An animal’s tolerance of humans is often measured using flight initiation distance (i.e. the distance at which an organism flees from a human stimulus). Research on Black Swans (Cygnus atratus) from both an urban population and a non-urban population, 30 km away, demonstrated that urban Black Swan populations have a shorter flight initiation distance and genetic variants in the dopamine receptor gene DRD4. This research suggests that there is likely a genetic basis for urban tolerance.
Where to go from here?
Perry proposes that urban evolution researchers begin to test if the genetically-mediated behaviors that are often observed in domesticated organisms, also arise in urban taxa (thus showing parallel evolution between domesticated and non-domesticated animals). Moreover, Perry suggests looking for these same comparisons between urban and non-urban forms of the same taxa, similar to the study of Black Swans described above. The increased availability and decreased cost of genomic scans of nonmodel organisms should greatly enhance our ability to detect these signatures of selection in urban populations and further help us grasp the specific ways in which urbanization shapes evolution.
Read the full article here: Perry, G.H. How human behavior can impact the evolution of genetically-mediated behavior in wild non-human species. J Comp Physiol A206, 337–342 (2020). https://doi.org/10.1007/s00359-020-01415-9
Featured image includes: “Bed with mosquito net at Cabinas Jenny – Cahuita CR” by catwommn is licensed under CC BY-NC-ND 2.0, “Blue jay eating at a feeder” by Frank Schulenburg is licensed under CC BY-SA 4.0, “Eastern Fence Lizard 03-20-08” by SchloughM is licensed under CC BY-SA 4.0, “Fire ants 01” by Stephen Ausmus is in the Public Domain, “Black Swan 2 – Pitt Town Lagoon” by JJ Harrison is licensed under CC BY-SA 4.0.
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