Shrinking into the big city: influence of genetic and environmental factors on urban dragon lizard morphology and performance capacity

Abstract

Urban wildlife faces a novel set of challenges resulting in selective pressure that can lead to population-level changes. We studied Australian water dragons (Intellagama lesueurii) from urban and natural populations to test if urban populations differed in body size, shape, and performance capacity. If urban-derived morphology has arisen through selection, we predicted distinct morphological differences between wild dragons from urban and natural areas in both adult and hatchling life-stages. Urban hatchlings were morphologically distinct (shorter body lengths and longer limbs) from natural populations, while urban adult males continued this trend but only for body size (shorter body lengths). We then experimentally reared hatchlings originating from urban and natural populations within urban-and natural-style enclosures (2 × 2 factorial design) for a year to determine if differences in morphology and performance capacity (sprint speed, endurance, and clinging ability) were related to either the individual's origin population or developmental environment. Yearlings reared in urban-style enclosures, irrespective of population origin, had smaller body sizes compared to those from natural-style enclosures, suggesting developmental environment was affecting their morphology. Despite this difference in body size, yearling dragon performance capacity was not significantly different between treatments. Overall, this study provides evidence of a complex relationship driving urban-divergent morphologywhereby urban dragons emerge as smaller hatchlings with longer limbs (innate traits) and are then further influenced by the urban environments that they develop in (phenotypic plasticity); however, and potentially owing to behavioral, ecological, and demographical differences, these changes appear to be sex-specific.

Selection in the city: Rapid and fine‐scale evolution of urban eastern water dragons

“…and (2) What could be the functional significance of this morphological differentiation (i.e., fitness)? Here, we speculate that snout-vent length and jaw width may be adapted to local population densities given their relationship with agonistic behavior, conspecific density, and fitness (Husak et al 2006;Baxter-Gilbert et al 2020;Piza-Roca et al 2020). Additionally, these two traits may diverge between our city parks as dragons adapt to locally available food types or are constrained in their growth by the local resource availability.…”

“…For instance, as seen in the case of plasticityled evolution, phenotypic plasticity may precede and even facilitate adaptive changes to the genome (Irschick and Meyers 2007;Winchell et al 2016;Levis and Pfennig 2021). Indeed, previous work has shown that although there is a heritable component to morphology in eastern water dragons, trait expression may depend on environmental contexts (i.e., plasticity) (Baxter-Gilbert et al 2020). Furthermore, given this study was conducted on adult individuals, we are unable to account for genotype-environment interactions during development (Grishkevich and Yanai 2013).…”

“…Indeed, previous work has shown that although there is a heritable component to morphology in eastern water dragons, trait expression may depend on environmental contexts (i.e., plasticity) (Baxter‐Gilbert et al. 2020 ). Furthermore, given this study was conducted on adult individuals, we are unable to account for genotype‐environment interactions during development (Grishkevich and Yanai 2013 ).…”

Social and spatial patterns of two Afromontane crag lizards (Pseudocordylus spp.) in the Maloti‐Drakensberg Mountains, South Africa

“…We used R version 3.5.0 to test for differences in morphological traits and bite force between males and females for each species (R Core Team 2018). All morphological traits and SVL were log 10transformed before analyses to ensure a scalar linear relationship (Lailvaux et al, 2004;Baxter-Gilbert et al 2020). First, we used a Type I analysis of variance (ANOVA) to test for a difference in SVL between sexes, which was performed using the R package 'car' and the function 'aov' (Fox & Weisberg 2019).…”

Island Hopping through Urban Filters: Anthropogenic Habitats and Colonized Landscapes Alter Morphological and Performance Traits of an Invasive Amphibian

“…Much in the same way, island ecosystems have been seen to expedite phenotypic shifts and adaptation in insular populations (e.g., island mammal morphology [ 9 ]). So too have urban habitats driven rapid phenotypic change in a variety of traits (i.e., urban evolution [ 7 ]), such as behavior [ 10 , 11 , 12 ], morphology [ 13 , 14 , 15 ], and performance capacity [ 16 ]. Many of the challenges and selective forces faced by colonizing populations—whether they be in novel island ecosystems or urban landscapes—can be quite similar, such as novel resources [ 17 , 18 , 19 ], sources of mortality [ 20 , 21 ], and altered thermal or hydric conditions [ 22 , 23 ].…”