scholarly journals The finer points of urban adaptation: intraspecific variation in lizard claw morphology

2020 ◽  
Vol 131 (2) ◽  
pp. 304-318
Author(s):  
Cleo H Falvey ◽  
Kevin J Aviles-Rodriguez ◽  
Travis J Hagey ◽  
Kristin M Winchell
Keyword(s):  
Natural Experiment ◽  
Urban Environments ◽  
Phenotypic Change ◽  
Structural Environment ◽  
Claw Morphology ◽  
Anthropogenic Substrates ◽  
Urban Adaptation ◽  
Shape Changes ◽  
Forest Habitats ◽  
Claw Shape

Abstract Human activity drastically transforms landscapes, generating novel habitats to which species must adaptively respond. Consequently, urbanization is increasingly recognized as a driver of phenotypic change. The structural environment of urban habitats presents a replicated natural experiment to examine trait–environment relationships and phenotypic variation related to locomotion. We use geometric morphometrics to examine claw morphology of five species of Anolis lizards in urban and forest habitats. We find that urban lizards undergo a shift in claw shape in the same direction but varying magnitude across species. Urban claws are overall taller, less curved, less pointed and shorter in length than those of forest lizards. These differences may enable more effective attachment or reduce interference with toepad function on smooth anthropogenic substrates. We also find an increase in shape disparity, a measurement of variation, in urban populations, suggesting relaxed selection or niche expansion rather than directional selection. This study expands our understanding of the relatively understudied trait of claw morphology and adds to a growing number of studies demonstrating phenotypic changes in urban lizards. The consistency in the direction of the shape changes we observed supports the intriguing possibility that urban environments may lead to predictable convergent adaptive change.

scholarly journals Decreased vigilance or habituation to humans? Mechanisms on increased boldness in urban animals

2019 ◽  
Vol 30 (6) ◽  
pp. 1583-1590 ◽  
Author(s):  
Kenta Uchida ◽  
Kei K Suzuki ◽  
Tatsuki Shimamoto ◽  
Hisashi Yanagawa ◽  
Itsuro Koizumi
Keyword(s):  
Urban Environments ◽  
Urban Wildlife ◽  
Distance Measures ◽  
Coping Response ◽  
Red Squirrels ◽  
Risk Levels ◽  
Novel Objects ◽  
Alert Distance ◽  
Urban Adaptation ◽  
Flight Initiation

Abstract Increased boldness is one of the most prevalent behavioral modifications seen in urban animals and is thought to be a coping response to anthropogenic environmental alterations. Most previous studies have shown enhanced boldness manifested as changes in responses to humans approaching, such as reductions in flight initiation distance (FID). However, this includes two confounding factors related to “boldness,” that is, reduction of vigilance and habituation to humans. Confounding these totally different processes could lead to our misunderstanding of urban adaptation and how to properly manage urban wildlife. Here, we propose a simple framework to separate the two processes using two flight distance measures toward different approaching threats. We considered that the distance at which targeted individuals noticed an approaching object (i.e., alert distance, AD) was related to vigilance, whereas FID represented risk assessment, which is related to habituation. We applied a predictive framework using AD and FID to Eurasian red squirrels’ responses to multiple threats of different risk levels (i.e., humans, model predators, and novel objects). AD was shorter in urban individuals compared with rural ones but not different among the approaching objects. FID was shorter in urban individuals and also varied among the objects with the shortest FID toward humans, whereas rural individuals showed similar FID to the different objects. These results suggest that, although urban individuals showed reduced vigilance, they could still assess different risk levels. Our framework can easily be applied to many animals and could significantly improve our understanding of wild animals’ adaptations to urban environments.

scholarly journals Convergent Evolution of Claw Shape in a Transcontinental Lizard Radiation

2019 ◽  
Vol 60 (1) ◽  
pp. 10-23 ◽  
Author(s):  
Simon Baeckens ◽  
Charlotte Goeyers ◽  
Raoul Van Damme
Keyword(s):  
Habitat Use ◽  
Convergent Evolution ◽  
Interspecific Variation ◽  
Environmental Pressures ◽  
Form Analysis ◽  
Form And Function ◽  
Claw Morphology ◽  
And Function ◽  
Claw Shape ◽  
Structural Habitat

Abstract Species occupying similar selective environments often share similar phenotypes as the result of natural selection. Recent discoveries, however, have led to the understanding that phenotypes may also converge for other reasons than recurring selection. We argue that the vertebrate claw system constitutes a promising but understudied model system for testing the adaptive nature of phenotypic, functional, and genetic convergence. In this study, we combine basic morphometrics and advanced techniques in form analysis to examine claw shape divergence in a transcontinental lizard radiation (Lacertidae). We find substantial interspecific variation in claw morphology and phylogenetic comparative statistics reveal a strong correlation with structural habitat use: ground-dwelling species living in open areas are equipped with long, thick, weakly curved, slender-bodied claws, whereas climbing species carry high, short, strongly curved, full-bodied claws. Species occupying densely vegetated habitats tend to carry intermediately shaped claws. Evolutionary models suggest that claw shape evolves toward multiple adaptive peaks, with structural habitat use pulling species toward a specific selective optimum. Contrary to findings in several other vertebrate taxa, our analyses indicate that environmental pressures, not phylogenetic relatedness, drive convergent evolution of similarly shaped claws in lacertids. Overall, our study suggests that lacertids independently evolved similarly shaped claws as an adaptation to similar structural environments in order to cope with the specific locomotory challenges posed by the habitat. Future biomechanical studies that link form and function in combination with genomic and development research will prove valuable in better understanding the adaptive significance of claw shape divergence.

scholarly journals Continent-wide genomic signatures of adaptation to urbanisation in a songbird across Europe

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Pablo Salmón ◽  
Arne Jacobs ◽  
Dag Ahrén ◽  
Clotilde Biard ◽  
Niels J. Dingemanse ◽  
...  
Keyword(s):  
Parus Major ◽  
Urban Environments ◽  
Rural Site ◽  
Neural Function ◽  
Selective Sweeps ◽  
Genetic Changes ◽  
Ample Evidence ◽  
Genomic Signatures ◽  
Core Set ◽  
Urban Adaptation

AbstractUrbanisation is increasing worldwide, and there is now ample evidence of phenotypic changes in wild organisms in response to this novel environment. Yet, the genetic changes and genomic architecture underlying these adaptations are poorly understood. Here, we genotype 192 great tits (Parus major) from nine European cities, each paired with an adjacent rural site, to address this major knowledge gap in our understanding of wildlife urban adaptation. We find that a combination of polygenic allele frequency shifts and recurrent selective sweeps are associated with the adaptation of great tits to urban environments. While haplotypes under selection are rarely shared across urban populations, selective sweeps occur within the same genes, mostly linked to neural function and development. Collectively, we show that urban adaptation in a widespread songbird occurs through unique and shared selective sweeps in a core-set of behaviour-linked genes.

scholarly journals Tardigrade abundance in relation to urbanisation and highly anthropogenic substrates

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Thomas McCarthy ◽  
Javier delBarco-Trillo
Keyword(s):  
Leaf Litter ◽  
Urban Environments ◽  
Extreme Conditions ◽  
Rural And Urban ◽  
Challenges And Opportunities ◽  
Anthropogenic Substrates ◽  
Rural Sites ◽  
Urban Sites

Abstract Animals colonising urban environments are exposed to a series of novel stressors and ecological challenges, which can result in adaptations to alternative urban niches. Tardigrades are cosmopolitan invertebrates present in all types of ecosystems, including urban environments; and they can survive under extreme conditions, including periods of desiccation, thus allowing them to colonise novel harsh habitats. Tardigrades are thus a promising model to investigate the challenges and opportunities encountered by urban colonisers. Our aims were 1, to determine if tardigrade abundance in natural substrates (moss, lichen and leaf litter) differs between rural and urban sites and 2, to assess if tardigrades have successfully colonised urban substrates that are highly anthropogenic (road sediment, and material accumulated under cars and in wall crevices). Among natural substrates, we found fewer tardigrades in Cork city than in rural sites. However, in urban sites we found no differences between the number of tardigrades present in natural and anthropogenic substrates. In fact, the highest tardigrade abundances in urban samples were found in abiotic material accumulated in wall crevices. We conclude that even though urbanisation may restrict tardigrade abundance, this group of organisms can successfully colonise alternative urban substrates. More research is needed on the ability of tardigrades and other taxa to inhabit highly unusual and disturbed urban substrates effectively, and the adaptations that may take place when animals colonise such substrates.

scholarly journals Modern spandrels: The roles of genetic drift, gene flow and natural selection in the formation of parallel clines

2018 ◽  
Author(s):  
James S. Santangelo ◽  
Marc T. J. Johnson ◽  
Rob W. Ness
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
Genetic Architecture ◽  
Natural Populations ◽  
Urban Environments ◽  
Phenotypic Change ◽  
Phenotypic Traits ◽  
Evolutionary Processes ◽  
Urbanization Gradients

AbstractUrban environments offer the opportunity to study the role of adaptive and non-adaptive evolutionary processes on an unprecedented scale. While the presence of parallel clines in heritable phenotypic traits is often considered strong evidence for the role of natural selection, non-adaptive evolutionary processes can also generate clines, and this may be more likely when traits have a non-additive genetic basis due to epistasis. In this paper, we use spatially-explicit simulations modelled according to the cyanogenesis (HCN) polymorphism in white clover (Trifolium repens) to examine the formation of phenotypic clines along urbanization gradients under varying levels of drift, gene flow and selection. HCN results from an epistatic interaction between two Mendelian-inherited loci. Our results demonstrate that the genetic architecture of this trait makes natural populations susceptible to decreases in HCN frequencies via drift. Gradients in the strength of drift across a landscape resulted in phenotypic clines with lower frequencies of HCN in strongly drifting populations, giving the misleading appearance of deterministic adaptive changes in the phenotype. Studies of heritable phenotypic change in urban populations should generate null models of phenotypic evolution based on the genetic architecture underlying focal traits prior to invoking selection’s role in generating adaptive differentiation.

scholarly journals Modern spandrels: the roles of genetic drift, gene flow and natural selection in the evolution of parallel clines

2018 ◽  
Vol 285 (1878) ◽  
pp. 20180230 ◽  
Author(s):  
James S. Santangelo ◽  
Marc T. J. Johnson ◽  
Rob W. Ness
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
Genetic Architecture ◽  
Natural Populations ◽  
Urban Environments ◽  
Phenotypic Change ◽  
Phenotypic Traits ◽  
Evolutionary Processes ◽  
Urbanization Gradients

Urban environments offer the opportunity to study the role of adaptive and non-adaptive evolutionary processes on an unprecedented scale. While the presence of parallel clines in heritable phenotypic traits is often considered strong evidence for the role of natural selection, non-adaptive evolutionary processes can also generate clines, and this may be more likely when traits have a non-additive genetic basis due to epistasis. In this paper, we use spatially explicit simulations modelled according to the cyanogenesis (hydrogen cyanide, HCN) polymorphism in white clover ( Trifolium repens ) to examine the formation of phenotypic clines along urbanization gradients under varying levels of drift, gene flow and selection. HCN results from an epistatic interaction between two Mendelian-inherited loci. Our results demonstrate that the genetic architecture of this trait makes natural populations susceptible to decreases in HCN frequencies via drift. Gradients in the strength of drift across a landscape resulted in phenotypic clines with lower frequencies of HCN in strongly drifting populations, giving the misleading appearance of deterministic adaptive changes in the phenotype. Studies of heritable phenotypic change in urban populations should generate null models of phenotypic evolution based on the genetic architecture underlying focal traits prior to invoking selection's role in generating adaptive differentiation.

The influence of natural and urban environments on attentional processing of emotional stimuli

2014 ◽  
Author(s):  
Chrono Nu ◽  
Katie Mullin ◽  
Hailey Edwards ◽  
Kailey Kornhauser ◽  
Russell Costa ◽  
...  
Keyword(s):  
Urban Environments ◽  
Emotional Stimuli ◽  
Attentional Processing

THE STRUCTURAL ENVIRONMENT OF Te DOPANTS IN GaAs USING EXAFS IN FLUORESCENCE MODE

1986 ◽  
Vol 47 (C8) ◽  
pp. C8-901-C8-904 ◽  
Author(s):  
G. N. GREAVES ◽  
P. J. HALFPENNY ◽  
G. M. LAMBLE ◽  
K. J. ROBERTS
Keyword(s):  
Structural Environment

Minimetrò in Perugia as leverage for urban regeneration

TERRITORIO ◽  
2020 ◽  
pp. 148-163
Author(s):  
Luca Fondacci
Keyword(s):  
Urban Regeneration ◽  
Urban Environments ◽  
Low Carbon ◽  
Sustainable Mobility ◽  
Field Surveys ◽  
Peripheral Area ◽  
Alternative Means ◽  
Considerable Impact ◽  
The City ◽  
Historical Centre

In the 1970s, the fragile historical centre of the city of Perugia was a key area where the binomial of sustainable mobility and urban regeneration was developed and applied. At the turn of the xxi century, the low carbon automatic people-mover Minimetrò broadened that application from the city's historical centre to the outskirts, promoting the enhancement of several urban environments. This paper is the outcome of an investigation of original sources, field surveys and direct interviews, which addresses the Minimetrò as the backbone of a wide regeneration process which has had a considerable impact on the economic development of a peripheral area of the city which was previously devoid of any clear urban sense. The conclusion proposes some solutions to improve the nature of the Minimetrò as an experimental alternative means of transport.

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