Urban invaders are not bold risk-takers: a study of 3 invasive lizards in Southern California

Abstract Biological invasions threaten biodiversity worldwide, and therefore, understanding the traits of successful invaders could mitigate their spread. Many commonly invasive species do well in disturbed habitats, such as urban environments, and their abilities to effectively respond to disturbances could contribute to their invasiveness. Yet, there are noninvasive species that also do well in disturbed habitats. The question remains whether urban invaders behave differently in urban environments than noninvaders, which could suggest an “urban-exploiting” phenotype. In Southern California, the co-occurrence of invasive Italian wall lizards Podarcis siculus, brown anoles Anolis sagrei, and green anoles A. carolinensis, and native western fence lizards Sceloporus occidentalis offers an opportunity to test whether invasives exhibit consistent differences in risk-taking within human-altered habitats compared with a native species. We predicted that invasive lizards would exhibit more bold behavior by having shorter flight-initiation distances (FIDs) and by being found farther from a refuge (behaviors that would presumably maximize foraging in low-risk environments). Invasive populations had similar or longer FIDs, but were consistently found at distances closer to a refuge. Collectively, invasive lizards in urban habitats were not bolder than a native species. Reliance on nearby refuges might help species successfully invade urban habitats, and if a general pattern, may pose an added challenge in detecting or eliminating them.

Download Full-text

The effects of local filtering processes on the structure and functioning of native plant communities in experimental urban habitats

10.22541/au.163938361.18647838/v1 ◽

2021 ◽

Author(s):

Dorothy Borowy ◽

Chris Swan

Keyword(s):

Plant Species ◽

Functional Diversity ◽

Plant Communities ◽

Native Species ◽

Urban Environments ◽

Functional Composition ◽

Native Plant ◽

Urban Habitats ◽

Over Time ◽

Local Filtering

Despite a growing literature-base devoted to documenting biodiversity patterns in cities, little is known about the processes that influence these patterns, and whether they are consistent over time. In particular, numerous studies have identified the capacity of cities to host a rich diversity of plant species. This trend, however, is driven primarily by introduced species, which comprise a large proportion of the urban species pool relative to natives. Using an experimental common garden study, we assessed the relative influence of local assembly processes (i.e., soil environmental filtering and competition from spontaneous urban species) on the taxonomic and functional diversity of native plant communities sampled over four seasons in 2016-2018. Taxonomic and functional diversity exhibited different responses to local processes, supporting the general conclusion that species- and trait-based measures of biodiversity offer distinct insights into community assembly dynamics. Additionally, we found that neither soil nor competition from spontaneous urban species influenced taxonomic or functional composition of native species. Functional composition, however, did shift strongly over time and was driven by community-weighted mean differences in both measured traits (maximum height, Hmax; specific leaf area, SLA; leaf chlorophyll a fluorescence, chl a) and the relative proportions of different functional groups (legumes, annual and biennial-perennial species, C4 grasses, and forbs). In contrast, taxonomic composition only diverged between early and late seasons. Overall, our results indicate that native species are not only capable of establishing and persisting in vacant urban habitats, they can functionally respond to local filtering pressures over time. This suggests that regional dispersal limitation may be a primary factor limiting native species in urban environments. Thus, future regreening and management plans should focus on enhancing the dispersal potential of native plant species in urban environments, in order to achieve set goals for increasing native species diversity and associated ecosystem services in cities.

Download Full-text

Diversity of organisms

10.1093/oso/9780198827238.003.0005 ◽

2018 ◽

Author(s):

Philip James

Keyword(s):

Life Cycle ◽

Urban Areas ◽

Native Species ◽

New Technologies ◽

Urban Environments ◽

Green Spaces ◽

The Common ◽

Living Organisms ◽

Micro Organisms ◽

Diversity Of Life

The focus of this chapter is an examination of the diversity of living organisms found within urban environments, both inside and outside buildings. The discussion commences with prions and viruses before moving on to consider micro-organisms, plants, and animals. Prions and viruses cause disease in plants and animals, including humans. Micro-organisms are ubiquitous and are found in great numbers throughout urban environments. New technologies are providing new insights into their diversity. Plants may be found inside buildings as well as in gardens and other green spaces. The final sections of the chapter offer a discussion of the diversity of animals that live in urban areas for part or all of their life cycle. Examples of the diversity of life in urban environments are presented throughout, including native and non-native species, those that are benign and deadly, and the common and the rare.

Download Full-text

Species interactions limit the occurrence of urban-adapted birds in cities

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1809317115 ◽

2018 ◽

Vol 115 (49) ◽

pp. E11495-E11504 ◽

Cited By ~ 11

Author(s):

Paul R. Martin ◽

Frances Bonier

Keyword(s):

Economic Development ◽

Species Interactions ◽

Dominant Species ◽

Economic Transition ◽

Urban Environments ◽

Competitive Interactions ◽

Urban Habitats ◽

Phylogenetic Groups ◽

Geographic Ranges ◽

Subordinate Species

Urbanization represents an extreme transformation of more natural systems. Populations of most species decline or disappear with urbanization, and yet some species persist and even thrive in cities. What determines which species persist or thrive in urban habitats? Direct competitive interactions among species can influence their distributions and resource use, particularly along gradients of environmental challenge. Given the challenges of urbanization, similar interactions may be important for determining which species persist or thrive in cities; however, their role remains poorly understood. Here, we use a global dataset to test among three alternative hypotheses for how direct competitive interactions and behavioral dominance may influence the breeding occurrence of birds in cities. We find evidence to support the competitive interference hypothesis: behaviorally dominant species were more widespread in urban habitats than closely related subordinate species, but only in taxa that thrive in urban environments (hereafter, urban adapted), and only when dominant and subordinate species overlapped their geographic ranges. This result was evident across diverse phylogenetic groups but varied significantly with a country’s level of economic development. Urban-adapted, dominant species were more widespread than closely related subordinate species in cities in developed, but not developing, countries; countries in economic transition showed an intermediate pattern. Our results provide evidence that competitive interactions broadly influence species responses to urbanization, and that these interactions have asymmetric effects on subordinate species that otherwise could be widespread in urban environments. Results further suggest that economic development might accentuate the consequences of competitive interactions, thereby reducing local diversity in cities.

Download Full-text

Landscape Genetic Approaches to Understanding Movement and Gene Flow in Cities

Urban Evolutionary Biology ◽

10.1093/oso/9780198836841.003.0005 ◽

2020 ◽

pp. 54-73

Author(s):

Jason Munshi-South ◽

Jonathan L. Richardson

Keyword(s):

Gene Flow ◽

Urban Landscape ◽

Bare Soil ◽

Urban Environments ◽

Urban Habitats ◽

Urban Neighbourhoods ◽

Direct Tracking ◽

Landscape Genetic ◽

The Many ◽

Socioeconomic Data

Cities are home to a continuum of species that range from those specially adapted to exploit urban habitats, to others passing through as transient dispersers. Urbanization often has a profound impact on the movement and gene flow of these species. Compared to natural landscapes, urban environments are complex matrices of roads, buildings, bare soil, slopes, green space, and subterranean infrastructure. Urban neighbourhoods also vary greatly in their socioeconomic and cultural characteristics. This heterogeneity can lead to complex movement patterns in wildlife that are difficult or impossible to characterize using direct tracking methods. Population genetic analyses provide powerful approaches to evaluate spatial patterns of genetic variation and even signatures of adaptive evolution across the genome. When analysed with landscape, environmental, and socioeconomic data, genetic approaches may also identify which features of urban habitats impede or facilitate gene flow. These landscape genetic approaches, when paired with high-resolution sampling and replicated studies across multiple cities, identify dynamic processes that underpin wildlife movement in cities. This chapter reviews the use of spatially explicit genetic approaches in understanding urban wildlife movement, and highlights the many insights gained from rodents in particular as models for urban landscape genetics.

Download Full-text

Physiological and morphological responses of invasiveAmbrosia artemisiifolia(common ragweed) to different irradiances

Botany ◽

10.1139/b2012-096 ◽

2012 ◽

Vol 90 (12) ◽

pp. 1284-1294 ◽

Cited By ~ 4

Author(s):

Zhong Qin ◽

Dan Juan Mao ◽

Guo Ming Quan ◽

Jia-en Zhang ◽

Jun Fang Xie ◽

...

Keyword(s):

Leaf Area ◽

Native Species ◽

Southern China ◽

High Growth ◽

Ambrosia Artemisiifolia ◽

Total Biomass ◽

Plant Structure ◽

Morphological Adaptations ◽

Net Assimilation ◽

Disturbed Habitats

Invasion by the exotic herb Ambrosia artemisiifolia L. has become a serious agricultural and environmental problem and of increasing research interest as the species continues its southward spread into subtropical regions of China. To better understand the possible physiological and morphological adaptations of A. artemisiifolia in this region, we conducted a greenhouse experiment using seedlings of A. artemisiifolia and a comparative native species, Urena lobata L. (Caesar’s weed), which is an erect annual shrub in the Malvaceae that commonly co-occurs with A. artemisiifolia in open, disturbed habitats in southern China. Seedlings of both plants were grown under four irradiance regimes (10%, 30%, 55%, and 100% irradiance) from 14 May to 13 July 2010. Ambrosia artemisiifolia showed significantly higher total biomass, total leaf area, specific leaf area, relative growth rate, and net assimilation rate but lower leaf mass fraction than U. lobata at the 30%–100% irradiance levels. With decreasing irradiance, A. artemisiifolia significantly increased biomass allocation to stems and decreased allocation to roots. Meanwhile, A. artemisiifolia exhibited higher light-saturated photosynthetic rates and light saturation points with wide variances except at the 10% irradiance treatment. These findings suggest that A. artemisiifolia has generally higher irradiance plasticity for traits pertaining to biomass partitioning, growth, and plant structure than U. lobata. The ability of A. artemisiifolia to tolerate high shade conditions while maintaining high growth rates at elevated irradiance levels may afford it a competitive advantage and may help explain its recent colonization and spread in southern China.

Download Full-text

Nest-site competition and killing by invasive parakeets cause the decline of a threatened bat population

Royal Society Open Science ◽

10.1098/rsos.172477 ◽

2018 ◽

Vol 5 (5) ◽

pp. 172477 ◽

Cited By ~ 21

Author(s):

Dailos Hernández-Brito ◽

Martina Carrete ◽

Carlos Ibáñez ◽

Javier Juste ◽

José L. Tella

Keyword(s):

Native Species ◽

Population Decline ◽

Urban Environments ◽

Strong Impact ◽

Long Term Effects ◽

Individual Fitness ◽

Tree Cavities ◽

Negative Impacts ◽

Site Competition

The identification of effects of invasive species is challenging owing to their multifaceted impacts on native biota. Negative impacts are most often reflected in individual fitness rather than in population dynamics of native species and are less expected in low-biodiversity habitats, such as urban environments. We report the long-term effects of invasive rose-ringed parakeets on the largest known population of a threatened bat species, the greater noctule, located in an urban park. Both species share preferences for the same tree cavities for breeding. While the number of parakeet nests increased by a factor of 20 in 14 years, the number of trees occupied by noctules declined by 81%. Parakeets occupied most cavities previously used by noctules, and spatial analyses showed that noctules tried to avoid cavities close to parakeets. Parakeets were highly aggressive towards noctules, trying to occupy their cavities, often resulting in noctule death. This led to a dramatic population decline, but also an unusual aggregation of the occupied trees, probably disrupting the complex social behaviour of this bat species. These results indicate a strong impact through site displacement and killing of competitors, and highlight the need for long-term research to identify unexpected impacts that would otherwise be overlooked.

Download Full-text

Carnivore persistence in fragmented habitats in urban southern California

Pacific Conservation Biology ◽

10.1071/pc030144 ◽

2003 ◽

Vol 9 (2) ◽

pp. 144 ◽

Cited By ~ 3

Author(s):

Lourraine A. Tigas ◽

Dirk H. Van Vuren ◽

Raymond M. Sauvajot

Keyword(s):

Native Species ◽

Southern California ◽

Didelphis Virginiana ◽

Lynx Rufus ◽

Urban Habitat ◽

Secondary Importance ◽

Carnivore Species ◽

Close Proximity ◽

Remote Camera ◽

Total Species

We investigated the responses of carnivores to habitat fragmentation in urban southern California. We used scat, track, and remote camera surveys to determine presence and residence of carnivores on habitat fragments of various sizes (4.4-561.0 ha) and degrees of isolation (10-750 m). Fragment area explained a significant portion of the variation in all four measures of species richness (total species present, native species present, total species resident, and native species resident). Isolation was of secondary importance and was significant only for species presence. We suggest that fewer carnivore species at smaller or more isolated fragments resulted from foraging decisions based on lower food reward in smaller fragments and greater movement costs for more distant fragments. Carnivore species responded differentially to fragmentation. Bobcats Lynx rufus were fragmentation-sensitive and apparently required large fragments, thus they may be useful as focal species for conservation planning. In contrast, Coyotes Canis latrans were more fragmentation-tolerant and, along with smaller species such as Northern Raccoons Procyon lotor, Striped Skunks Mephitis mephitis, and Virginia Opossums Didelphis virginiana, can persist in smaller fragments. Our results suggest that most of the common carnivores can persist in fragmented urban habitat, provided that fragments are sufficiently large and in close proximity.

Download Full-text

Distributions of Invasive Arthropods across Heterogeneous Urban Landscapes in Southern California: Aridity as a Key Component of Ecological Resistance

Insects ◽

10.3390/insects10010029 ◽

2019 ◽

Vol 10 (1) ◽

pp. 29 ◽

Cited By ~ 1

Author(s):

Weston Staubus ◽

Savanah Bird ◽

Savannah Meadors ◽

Wallace Meyer

Keyword(s):

Native Species ◽

Southern California ◽

Propagule Pressure ◽

Urban Systems ◽

Urban Landscapes ◽

Resource Subsidies ◽

Ecological Resistance ◽

Large Numbers ◽

Sage Scrub ◽

Grassland Habitats

Urban systems often support large numbers of non-native species, but due to the heterogeneity of urban landscapes, species are not evenly distributed. Understanding the drivers of ecological resistance in urban landscapes may help to identify habitats that are most resistant to invasion, and inform efforts to model and conserve native biodiversity. We used pitfall traps to survey non-native ground-dwelling arthropods in three adjacent, low-elevation habitat types in southern California: California sage scrub, non-native grassland, and suburban development. We found that non-native species were fewer and less widely distributed in the sage scrub and grassland habitats. Due to the proximity of our sites, differences in propagule pressure is an unlikely explanation. Instead, we suggest that the absence of water subsidies in the sage scrub and grassland habitats increases those habitats’ resistance to arthropod invasions. Comparisons to studies conducted at fragments closer to the coast provide further support for the relationship between aridity and invasibility in southern California. Our findings highlight that inland fragments are important for conserving native arthropod diversity, that models of non-native species distributions in arid and semi-arid urban systems should include aridity measures, and that reducing resource subsidies across the region is critical to mitigating spread of non-natives.

Download Full-text

Experience in local urban wildlife research enhances a conservation education programme with school children.

Pacific Conservation Biology ◽

10.1071/pc120041 ◽

2012 ◽

Vol 18 (1) ◽

pp. 41 ◽

Cited By ~ 1

Author(s):

Monica Awasthy ◽

Ana Z Popovic ◽

Wayne L Linklater

Keyword(s):

Native Species ◽

Green Space ◽

Radio Telemetry ◽

Education Programme ◽

Urban Environments ◽

Conservation Education ◽

Biological Research ◽

Local Schools ◽

Hands On ◽

Nature Awareness

The “extinction of [ecological] experience” is a concern for children in urban centres. Urban environments, traditionally the refuge of exotic human-commensal species, are being increasingly colonised by native species. We used a native bird as a focal species for integrating urban biological research and environmental education (EE) in conservation. We tested whether incorporating biological researchers into classroom teaching and hands-on experiences with radio-telemetry of wild birds increased wildlife knowledge, environmental awareness and intentions to act amongst children from local schools. We found no significant increases in knowledge after our EE programme. However, those children who participated in exercises with researchers in local green space demonstrated a greater level of nature awareness than groups who participated in the schoolyard, and retained this level three months after the programme completion. We illustrate the importance of incorporating biological research in conservation education in urban centres.

Download Full-text

Urban birds have broader environmental tolerance

Biology Letters ◽

10.1098/rsbl.2007.0349 ◽

2007 ◽

Vol 3 (6) ◽

pp. 670-673 ◽

Cited By ~ 160

Author(s):

Frances Bonier ◽

Paul R Martin ◽

John C Wingfield

Keyword(s):

Urban Environments ◽

Urban Habitats ◽

Urban Birds ◽

Environmental Tolerance ◽

Global Comparison ◽

Ecological Flexibility

Urbanization dramatically changes the composition and diversity of biotic communities. The characteristics distinguishing species that persist in urban environments, however, are poorly understood. Here we test the hypothesis that broadly adapted organisms are better able to tolerate urbanization, using a phylogenetically controlled, global comparison of birds. We compared elevational and latitudinal distributions of 217 urban birds found in 73 of the world's largest cities with distributions of 247 rural congeners to test the hypothesis that urban birds possess broader environmental tolerance. Urban birds had markedly broader environmental tolerance than rural congeners, as estimated by elevational and latitudinal distributions. Our results suggest that broad environmental tolerance may predispose some birds to thrive in urban habitats. The mechanisms mediating such environmental tolerance warrant further investigation, but probably include greater behavioural, physiological and ecological flexibility.

Download Full-text