The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Kevin R Crooks - One of the best experts on this subject based on the ideXlab platform.
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Urban Habitat fragmentation and genetic population structure of bobcats in coastal southern california
American Midland Naturalist, 2012Co-Authors: Emily W Ruell, Seth P D Riley, Marlis R Douglas, Michael F Antolin, J R Pollinger, Jeff A Tracey, Lisa M Lyren, Erin E Boydston, Robert N Fisher, Kevin R CrooksAbstract:Abstract Although Habitat fragmentation is recognized as a primary threat to biodiversity, the effects of Urban development on genetic population structure vary among species and landscapes and are not yet well understood. Here we use non-invasive genetic sampling to compare the effects of fragmentation by major roads and Urban development on levels of dispersal, genetic diversity, and relatedness between paired bobcat populations in replicate landscapes in coastal southern California. We hypothesized that bobcat populations in sites surrounded by Urbanization would experience reduced functional connectivity relative to less isolated nearby populations. Our results show that bobcat genetic population structure is affected by roads and development but not always as predicted by the degree that these landscape features surround fragments. Instead, we suggest that Urban development may affect functional connectivity between bobcat populations more by limiting the number and genetic diversity of source popula...
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extirpation colonization and Habitat dynamics of a keystone species along an Urban gradient
Biological Conservation, 2010Co-Authors: Seth B. Magle, Perla E Reyes, Kevin R CrooksAbstract:Using 5 years of patch occupancy data for 384 Habitat fragments, we evaluated population and Habitat dynamics of the black-tailed prairie dog in Urban Habitat remnants in the rapidly developing landscape of Denver, CO, USA. Specifically, we evaluated the landscape factors, including fragment area, age, and connectivity, that characterize the Habitat fragments most likely to be colonized by prairie dogs, as well as those experiencing local extinctions. In addition, we determined which patch types were most often removed by land development. Sites in proximity to colonies were more likely to be colonized by prairie dogs. Local extinctions were most common on isolated colonies, and older and more isolated colonies were more likely to be extirpated by human activity. In general, smaller and older Habitat patches were at the highest risk of being lost to land development. Our results provide observations of dynamic changes to the distribution of a potential keystone species in an Urban area, which can be used to inform island biogeographic and metapopulation models for wildlife persistence in developing landscapes. Although populations are currently in decline, most local extinctions are the direct result of human activity, and we suggest that prairie dogs in this area can persist with appropriate management.
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relative sensitivities of mammalian carnivores to Habitat fragmentation
Conservation Biology, 2002Co-Authors: Kevin R CrooksAbstract:I examined the effects of Habitat fragmentation on the distribution and abundance of mamma- lian carnivores in coastal southern California and tested the prediction that responses to fragmentation var- ied with the body size of carnivore species. I conducted track surveys for nine native and two exotic carnivore species in 29 Urban Habitat fragments and 10 control sites. Fragment area and isolation were the two stron- gest landscape descriptors of predator distribution and abundance. Six species were sensitive to fragmenta- tion, generally disappearing as Habitat patches became smaller and more isolated; three species were en- hanced by fragmentation, with increased abundance in highly fragmented sites; and two species were tolerant of fragmentation, with little to no effect of landscape variables on their distribution and abundance. Within Urban Habitat fragments, the carnivore visitation rate increased at sites with more exotic cover and closer to the Urban edge, a pattern driven largely by the increased abundance of fragmentation-enhanced carnivores at edge sites. Finally, body size, in conjunction with other ecological characteristics, partially ac- counted for the heterogeneity in responses to fragmentation among carnivore species. These differential sensi- tivities are useful criteria for choosing appropriate focal species for ecological research and conservation planning, a choice that depends on the scale of fragmentation in a region and the commensurate responses of carnivore populations at that scale.
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arthropods in Urban Habitat fragments in southern california area age and edge effects
Ecological Applications, 2000Co-Authors: Douglas T Bolger, Kevin R Crooks, Andrew V Suarez, Scott A Morrison, Ted J CaseAbstract:The distribution of non-ant arthropods was examined in 40 Urban Habitat fragments in coastal San Diego County, California, USA, to look for effects of fragmen- tation, proximity to developed edge, and the non-native Argentine ant (Linepithema humile). Arthropods were sampled with pitfall traps and by vacuum sampling from California buck- wheat shrubs (Eriogonumfasciculatum). Individual arthropods were identified to order and Recognizable Taxonomic Unit (RTU), or morphospecies. At the fragment scale we looked for correlations in the point diversity and abundance of arthropods as a function of the age and area of the fragment being sampled. At the scale of the individual sample points we looked for correlations of abundance and diversity with variables that describe the species composition of the shrub vegetation and distUrbance. As indicators of distUrbance we used the cover of native woody and exotic non-woody vegetation, the distance to the nearest developed edge, and the abundance of Argentine ants. The following patterns were found: (1) In general, arthropods showed a fragmentation effect with point diversity and abundance positively correlated with fragment area and negatively correlated with fragment age. (2) The pitfall samples were dominated by three primarily non-native orders, Isopoda (pillbugs), Dermaptera (earwigs), and Blattaria (roaches). Over 35% of all pitfall-captured arthropods belonged to four species in these orders. Dermaptera and Blattaria increased in abundance in smaller and older fragments, respectively. Isopod abundance, in contrast, was unrelated to fragment attributes. None of these groups appeared to be associated with edges, but were distributed throughout the fragments. (3) Point diversity and abundance in ground-active spiders appears to be enhanced by fragmentation. (4) Total pitfall RTU richness and abun- dance, and abundance or richness in the Coleoptera (vacuum), Diptera, non-ant Hymenop- tera, Hemiptera, Microcoryphia, and Acarina had significant partial negative correlations with Argentine ant abundance. The Diptera and Coleoptera had this negative partial rela- tionship with the Argentine ants despite the fact that both they and the ants were positively associated with edges. (5) In general, diversity in most orders was higher in sampling locations dominated by coastal sage scrub Habitat than in those with appreciable cover of chaparral shrub species. (6) There was a strong seasonal variation in abundance and diversity in most orders. Diversity and abundance were highest in spring, intermediate in winter, and lowest in the fall. (7) Although higher trophic levels are often considered to be more sensitive to fragmentation, two groups of arthropod predators, spiders and carabid beetles, increased in abundance in older fragments. Abundance of these predators was positively correlated with the abundance of Argentine ants and the non-native Isopods, Dermaptera, and Blattaria.
Roeland Samson - One of the best experts on this subject based on the ideXlab platform.
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intra Urban spatial variation of magnetic particles monitoring via leaf saturation isothermal remanent magnetisation sirm
Atmospheric Environment, 2012Co-Authors: Fatemeh Kardel, Karen Wuyts, Barbara A Maher, Roeland SamsonAbstract:Motorised traffic generates large numbers of particulate pollutants in the Urban environment. Exposure to small particles has been associated with adverse effects on human health. Biomonitoring of magnetic particles accumulated on leaf surfaces may provide information on the concentration of, and exposure to, atmospheric particles at high spatial resolution. In this study, leaf saturation isothermal remanent magnetisation (SIRM) of three Urban tree types (Carpinus betulus and Tilia sp. with hairy and non-hairy leaves) was measured at high spatial resolution in the city of Ghent, Belgium, in June and September 2009. We compared leaf SIRM between land use classes with different Urban Habitat quality. In a multiple regression model, we tried to explain the spatial variability in the leaf SIRM by tree species, sampling height, distance to the nearest road and its traffic intensity, tram frequency and a measure for regional traffic emissions (derived from traffic intensity of and the distance to the most important highways around the city in the main four wind directions). We found that the leaf SIRM was significantly influenced by tree species, distance to the nearest road and its traffic intensity and tram frequency. The SIRM significantly increased with increasing traffic intensity and tram frequency and by decreasing distance to the nearest road. It is concluded that the leaf SIRM is a good bio-indicator for monitoring spatial variation of magnetic particles in Urban environments.
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tree leaf wettability as passive bio indicator of Urban Habitat quality
Environmental and Experimental Botany, 2012Co-Authors: Fatemeh Kardel, Tatiana Wuytack, Karen Wuyts, Manoochehr Babanezhad, Sandy Adriaenssens, Roeland SamsonAbstract:Abstract This study evaluated the effect of Urban Habitat quality on the wettability of tree leaves. We measured leaf wettability of five common tree species, i.e., Alnus glutinosa , Acer pseudoplatanus , Betula pendula , Quercus robur and Sambucus nigra , in semi-natural and industrial Urban Habitats in the city of Gent (Belgium). Possible seasonal variation was taken into account by measuring in late spring and in late summer. Drop contact angle (DCA), and height over width ratio were measured on the abaxial and the adaxial leaf surface as proxies for leaf wettability. The relative standard deviation for the height over width ratio was higher than for the DCA, so that only the latter was considered further. Habitat type significantly influenced leaf wettability: the DCA values of Q. robur leaves were significantly lower in the industrial than in the semi-natural areas, in both June and September while, for S. nigra , the DCA was in both sampling events significantly higher in the industrial areas. For the adaxial leaf side, the differences between the considered Habitats were more pronounced in June than in September. The adaxial DCA of A. pseudoplatanus was significantly higher in June compared to September, while the opposite held for abaxial values of A. glutinosa . We conclude that leaf wettability is potentially a good indicator to point out differences in Urban Habitat quality, but selection of the most sensitive tree species and the appropriate time of measuring is an important prerequisite.
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Assessing Urban Habitat quality based on specific leaf area and stomatal characteristics of Plantago lanceolata L.
Environmental Pollution, 2009Co-Authors: Fatemeh Kardel, Tatiana Wuytack, Karen Wuyts, Manoochehr Babanezhad, U.w.a. Vitharana, Geert Potters, Roeland SamsonAbstract:This study has evaluated Urban Habitat quality by studying specific leaf area (SLA) and stomatal characteristics of the common herb Plantago lanceolata L. SLA and stomatal density, pore surface and resistance were measured at 169 locations in the city of Gent (Belgium), distributed over four land use classes, i.e., sub-Urban green, Urban green, Urban and industry. SLA and stomatal density significantly increased from sub-Urban green towards more Urbanised land use classes, while the reverse was observed for stomatal pore surface. Stomatal resistance increased in the Urban and industrial land use class in comparison with the (sub-) Urban green, but differences between land use classes were less pronounced. Spatial distribution maps for these leaf characteristics showed a high spatial variation, related to differences in Habitat quality within the city. Hence, stomatal density and stomatal pore surface are assumed to be potentially good bio-indicators for Urban Habitat quality.
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biomonitoring of Urban Habitat quality by anatomical and chemical leaf characteristics
Environmental and Experimental Botany, 2009Co-Authors: Roeland Samson, U.w.a. Vitharana, B L W K Balasooriya, F Mbikwa, Pascal Boeckx, M Van MeirvenneAbstract:Abstract This study focused on the potential of specific leaf area, stomatal density and stomatal pore surface as easy-to-measure plant parameters in low cost biomonitoring of Urban Habitat quality with a high spatial resolution. The study area (81.5 km 2 ) was the city of Gent, Belgium. In the study area 148 sampling locations were identified within 4 land use classes. Specific leaf area, stomatal density, stomatal pore surface, minimal stomatal resistance, chlorophyll a and b , C and N content, δ 13 C and δ 15 N in the leaf samples of a common herbaceous plant Taraxacum officinalis were measured. The stomatal pore surface and minimal stomatal resistance of T. officinalis varied significantly between land use classes. In the harbor and industry land use class and the Urban land use class a 27% and 21% lower mean stomatal pore surface at the abaxial leaf surface, and a 29% and 27% lower mean stomatal pore surface at the adaxial leaf surface was observed compared to that in the pasture land use class. The minimal stomatal resistance at the abaxial leaf surface was significantly higher in the Urban land use class and harbor and industry land use class by 28% and 29%, respectively compared to that in the pasture land use class. In addition, Urbanized and industrial land use classes as the harbour and industry and the Urban land use classes showed significantly lower δ 13 C values compared to pasture land use class. The specific leaf area, stomatal parameters and δ 13 C data were geostatistically analyzed to understand their spatial variation. The spatial distributions of stomatal pore surface and minimal stomatal resistance varied considerably across the study area, indicating a different Habitat quality from the harbour area in the north, over the city centre in the middle and the industrial areas in the south, compared to off city areas. Spatial patterns of δ 13 C showed depleted δ 13 C levels in city areas indicating the diluted δ 13 C in the Urban atmosphere by fuel combustion. We concluded that stomatal characteristics seem to be the most promising parameter for estimating Urban Habitat quality.
Karen Wuyts - One of the best experts on this subject based on the ideXlab platform.
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intra Urban spatial variation of magnetic particles monitoring via leaf saturation isothermal remanent magnetisation sirm
Atmospheric Environment, 2012Co-Authors: Fatemeh Kardel, Karen Wuyts, Barbara A Maher, Roeland SamsonAbstract:Motorised traffic generates large numbers of particulate pollutants in the Urban environment. Exposure to small particles has been associated with adverse effects on human health. Biomonitoring of magnetic particles accumulated on leaf surfaces may provide information on the concentration of, and exposure to, atmospheric particles at high spatial resolution. In this study, leaf saturation isothermal remanent magnetisation (SIRM) of three Urban tree types (Carpinus betulus and Tilia sp. with hairy and non-hairy leaves) was measured at high spatial resolution in the city of Ghent, Belgium, in June and September 2009. We compared leaf SIRM between land use classes with different Urban Habitat quality. In a multiple regression model, we tried to explain the spatial variability in the leaf SIRM by tree species, sampling height, distance to the nearest road and its traffic intensity, tram frequency and a measure for regional traffic emissions (derived from traffic intensity of and the distance to the most important highways around the city in the main four wind directions). We found that the leaf SIRM was significantly influenced by tree species, distance to the nearest road and its traffic intensity and tram frequency. The SIRM significantly increased with increasing traffic intensity and tram frequency and by decreasing distance to the nearest road. It is concluded that the leaf SIRM is a good bio-indicator for monitoring spatial variation of magnetic particles in Urban environments.
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tree leaf wettability as passive bio indicator of Urban Habitat quality
Environmental and Experimental Botany, 2012Co-Authors: Fatemeh Kardel, Tatiana Wuytack, Karen Wuyts, Manoochehr Babanezhad, Sandy Adriaenssens, Roeland SamsonAbstract:Abstract This study evaluated the effect of Urban Habitat quality on the wettability of tree leaves. We measured leaf wettability of five common tree species, i.e., Alnus glutinosa , Acer pseudoplatanus , Betula pendula , Quercus robur and Sambucus nigra , in semi-natural and industrial Urban Habitats in the city of Gent (Belgium). Possible seasonal variation was taken into account by measuring in late spring and in late summer. Drop contact angle (DCA), and height over width ratio were measured on the abaxial and the adaxial leaf surface as proxies for leaf wettability. The relative standard deviation for the height over width ratio was higher than for the DCA, so that only the latter was considered further. Habitat type significantly influenced leaf wettability: the DCA values of Q. robur leaves were significantly lower in the industrial than in the semi-natural areas, in both June and September while, for S. nigra , the DCA was in both sampling events significantly higher in the industrial areas. For the adaxial leaf side, the differences between the considered Habitats were more pronounced in June than in September. The adaxial DCA of A. pseudoplatanus was significantly higher in June compared to September, while the opposite held for abaxial values of A. glutinosa . We conclude that leaf wettability is potentially a good indicator to point out differences in Urban Habitat quality, but selection of the most sensitive tree species and the appropriate time of measuring is an important prerequisite.
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Assessing Urban Habitat quality based on specific leaf area and stomatal characteristics of Plantago lanceolata L.
Environmental Pollution, 2009Co-Authors: Fatemeh Kardel, Tatiana Wuytack, Karen Wuyts, Manoochehr Babanezhad, U.w.a. Vitharana, Geert Potters, Roeland SamsonAbstract:This study has evaluated Urban Habitat quality by studying specific leaf area (SLA) and stomatal characteristics of the common herb Plantago lanceolata L. SLA and stomatal density, pore surface and resistance were measured at 169 locations in the city of Gent (Belgium), distributed over four land use classes, i.e., sub-Urban green, Urban green, Urban and industry. SLA and stomatal density significantly increased from sub-Urban green towards more Urbanised land use classes, while the reverse was observed for stomatal pore surface. Stomatal resistance increased in the Urban and industrial land use class in comparison with the (sub-) Urban green, but differences between land use classes were less pronounced. Spatial distribution maps for these leaf characteristics showed a high spatial variation, related to differences in Habitat quality within the city. Hence, stomatal density and stomatal pore surface are assumed to be potentially good bio-indicators for Urban Habitat quality.
Fatemeh Kardel - One of the best experts on this subject based on the ideXlab platform.
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intra Urban spatial variation of magnetic particles monitoring via leaf saturation isothermal remanent magnetisation sirm
Atmospheric Environment, 2012Co-Authors: Fatemeh Kardel, Karen Wuyts, Barbara A Maher, Roeland SamsonAbstract:Motorised traffic generates large numbers of particulate pollutants in the Urban environment. Exposure to small particles has been associated with adverse effects on human health. Biomonitoring of magnetic particles accumulated on leaf surfaces may provide information on the concentration of, and exposure to, atmospheric particles at high spatial resolution. In this study, leaf saturation isothermal remanent magnetisation (SIRM) of three Urban tree types (Carpinus betulus and Tilia sp. with hairy and non-hairy leaves) was measured at high spatial resolution in the city of Ghent, Belgium, in June and September 2009. We compared leaf SIRM between land use classes with different Urban Habitat quality. In a multiple regression model, we tried to explain the spatial variability in the leaf SIRM by tree species, sampling height, distance to the nearest road and its traffic intensity, tram frequency and a measure for regional traffic emissions (derived from traffic intensity of and the distance to the most important highways around the city in the main four wind directions). We found that the leaf SIRM was significantly influenced by tree species, distance to the nearest road and its traffic intensity and tram frequency. The SIRM significantly increased with increasing traffic intensity and tram frequency and by decreasing distance to the nearest road. It is concluded that the leaf SIRM is a good bio-indicator for monitoring spatial variation of magnetic particles in Urban environments.
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tree leaf wettability as passive bio indicator of Urban Habitat quality
Environmental and Experimental Botany, 2012Co-Authors: Fatemeh Kardel, Tatiana Wuytack, Karen Wuyts, Manoochehr Babanezhad, Sandy Adriaenssens, Roeland SamsonAbstract:Abstract This study evaluated the effect of Urban Habitat quality on the wettability of tree leaves. We measured leaf wettability of five common tree species, i.e., Alnus glutinosa , Acer pseudoplatanus , Betula pendula , Quercus robur and Sambucus nigra , in semi-natural and industrial Urban Habitats in the city of Gent (Belgium). Possible seasonal variation was taken into account by measuring in late spring and in late summer. Drop contact angle (DCA), and height over width ratio were measured on the abaxial and the adaxial leaf surface as proxies for leaf wettability. The relative standard deviation for the height over width ratio was higher than for the DCA, so that only the latter was considered further. Habitat type significantly influenced leaf wettability: the DCA values of Q. robur leaves were significantly lower in the industrial than in the semi-natural areas, in both June and September while, for S. nigra , the DCA was in both sampling events significantly higher in the industrial areas. For the adaxial leaf side, the differences between the considered Habitats were more pronounced in June than in September. The adaxial DCA of A. pseudoplatanus was significantly higher in June compared to September, while the opposite held for abaxial values of A. glutinosa . We conclude that leaf wettability is potentially a good indicator to point out differences in Urban Habitat quality, but selection of the most sensitive tree species and the appropriate time of measuring is an important prerequisite.
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Assessing Urban Habitat quality based on specific leaf area and stomatal characteristics of Plantago lanceolata L.
Environmental Pollution, 2009Co-Authors: Fatemeh Kardel, Tatiana Wuytack, Karen Wuyts, Manoochehr Babanezhad, U.w.a. Vitharana, Geert Potters, Roeland SamsonAbstract:This study has evaluated Urban Habitat quality by studying specific leaf area (SLA) and stomatal characteristics of the common herb Plantago lanceolata L. SLA and stomatal density, pore surface and resistance were measured at 169 locations in the city of Gent (Belgium), distributed over four land use classes, i.e., sub-Urban green, Urban green, Urban and industry. SLA and stomatal density significantly increased from sub-Urban green towards more Urbanised land use classes, while the reverse was observed for stomatal pore surface. Stomatal resistance increased in the Urban and industrial land use class in comparison with the (sub-) Urban green, but differences between land use classes were less pronounced. Spatial distribution maps for these leaf characteristics showed a high spatial variation, related to differences in Habitat quality within the city. Hence, stomatal density and stomatal pore surface are assumed to be potentially good bio-indicators for Urban Habitat quality.
Hans Slabbekoorn - One of the best experts on this subject based on the ideXlab platform.
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Habitat dependent acoustic divergence affects playback response in Urban and forest populations of the european blackbird
Behavioral Ecology, 2010Co-Authors: Erwin A P Ripmeester, Maarten Mulder, Hans SlabbekoornAbstract:Habitat-dependent song variation could play a role in ecological speciation from the incipient stages until completion of reproductive isolation. The evolutionarily novel Urban Habitat provides an excellent opportunity to study this role for song in the initial steps of population divergence associated with contrasting Habitats close to home. In this study, we show spectral and temporal song divergence at population level in European blackbirds in 3 city–forest pairs. The observed upward spectral shift in frequency for Urban songs relative to forest songs is consistent with previous studies on the same and several other species. A reciprocal playback experiment showed that male blackbirds pay attention to the origin of the stimulus and the divergent spectral trait independently of each other, as well as to a combination of both. The fact that Urban and forest males responded differentially to the same spectral song features suggests that the song divergence could influence where males with typical Urban or forest songs settle and are able to maintain a territory. Our findings show that Habitat-dependent song divergence has the potential to affect the responsiveness to signals in the initial stages of population differentiation. Key words: anthropogenic noise, bird song, ecological speciation, geographic variation, Turdus merula. [Behav Ecol]
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Habitat dependent acoustic divergence affects playback response in Urban and forest populations of the european blackbird
Behavioral Ecology, 2010Co-Authors: Erwin A P Ripmeester, Maarten Mulder, Hans SlabbekoornAbstract:Habitat-dependent song variation could play a role in ecological speciation from the incipient stages until completion of reproductive isolation. The evolutionarily novel Urban Habitat provides an excellent opportunity to study this role for song in the initial steps of population divergence associated with contrasting Habitats close to home. In this study, we show spectral and temporal song divergence at population level in European blackbirds in 3 city--forest pairs. The observed upward spectral shift in frequency for Urban songs relative to forest songs is consistent with previous studies on the same and several other species. A reciprocal playback experiment showed that male blackbirds pay attention to the origin of the stimulus and the divergent spectral trait independently of each other, as well as to a combination of both. The fact that Urban and forest males responded differentially to the same spectral song features suggests that the song divergence could influence where males with typical Urban or forest songs settle and are able to maintain a territory. Our findings show that Habitat-dependent song divergence has the potential to affect the responsiveness to signals in the initial stages of population differentiation. Copyright 2010, Oxford University Press.
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sound transmission and song divergence a comparison of Urban and forest acoustics
The Condor, 2007Co-Authors: Hans Slabbekoorn, Pamela J Yeh, Kimberly HuntAbstract:Abstract ABSTRACT Degradation of acoustic signals during transmission presents a challenging selection pressure for animals dependent on vocal communication. Sound transmission properties differ among Habitats and may drive the evolution of vocal signals in different directions. Urban Habitat is expanding worldwide and an increasing number of species, including many birds, must now communicate around buildings and over concrete. Urban Habitats are evolutionarily new, although to some extent they may acoustically resemble rocky Habitat such as cliffs and canyons. Neither Urban nor these natural Habitats have been studied in any detail for the selection pressure they may exert on animal communication. Dark-eyed Juncos (Junco hyemalis) commonly inhabit montane pine forests across North America, but for about 25 years an isolated population has been successfully breeding in an Urban environment in southern California. We investigated potentially divergent selection pressures on junco songs, using sound transm...
