Jonathan W. Atwell

Publications of Jonathan W. Atwell

• Maintenance of MHC Class IIB diversity in a recently established songbird population

  Authors: Danielle J. Whittaker, Amy L. Dapper, Mark P. Peterson, Jonathan W. Atwell, Ellen D. Ketterson

  Journal of Avian Biology. 01/2012; in press.

• Intraspecific preen oil odor preferences in dark-eyed juncos (Junco hyemalis)

  Authors: Danielle J. Whittaker, Kaitlin M. Richmond, Allison K. Miller, Ryan Kiley, Christine Bergeon Burns, Jonathan W. Atwell, Ellen D. Ketterson

  Behavioral Ecology. 01/2011; 22(1256):1263.

• Directional cultural change by modification and replacement of memes.

  Authors: Gonçalo C Cardoso, Jonathan W Atwell

  Evolution; international journal of organic evolution. 01/2011; 65(1):295-300.

  Evolutionary approaches to culture remain contentious. A source of contention is that cultural mutation may be substantial and, if it drives cultural change, then current evolutionary models are notEvolutionary approaches to culture remain contentious. A source of contention is that cultural mutation may be substantial and, if it drives cultural change, then current evolutionary models are not adequate. But we lack studies quantifying the contribution of mutations to directional cultural change. We estimated the contribution of one type of cultural mutations--modification of memes--to directional cultural change using an amenable study system: learned birdsongs in a species that recently entered an urban habitat. Many songbirds have higher minimum song frequency in cities, to alleviate masking by low-frequency noise. We estimated that the input of meme modifications in an urban songbird population explains about half the extent of the population divergence in song frequency. This contribution of cultural mutations is large, but insufficient to explain the entire population divergence. The remaining divergence is due to selection of memes or creation of new memes. We conclude that the input of cultural mutations can be quantitatively important, unlike in genetic evolution, and that it operates together with other mechanisms of cultural evolution. For this and other traits, in which the input of cultural mutations might be important, quantitative studies of cultural mutation are necessary to calibrate realistic models of cultural evolution.

• Songbird chemosignals: volatile compounds in preen gland secretions vary among individuals, sexes, and populations.

  Authors: Danielle J Whittaker, Helena A Soini, Jonathan W Atwell, Craig Hollars, Milos V Novotny, Ellen D Ketterson

  Behavioral ecology : official journal of the International Society for Behavioral Ecology. 01/2010; 21(3):608-614.

  Chemical signaling has been documented in many animals, but its potential importance in avian species, particularly songbirds, has received far less attention. We tested whether volatile compounds inChemical signaling has been documented in many animals, but its potential importance in avian species, particularly songbirds, has received far less attention. We tested whether volatile compounds in the preen oil of a songbird (Junco hyemalis) contain reliable information about individual identity, sex, or population of origin by repeated sampling from captive male and female juncos originating from 2 recently diverged junco populations in southern California. One of the populations recently colonized an urban environment; the other resides in a species-typical montane environment. The birds were field-caught as juveniles, housed under identical conditions, and fed the same diet for 10 months prior to sampling. We used capillary gas chromatography-mass spectrometry to quantify the relative abundance of 19 volatile compounds previously shown to vary seasonally in this species. We found individual repeatability as well as significant sex and population differences in volatile profiles. The persistence of population differences in a common environment suggests that preen oil chemistry likely has a genetic basis and may thus evolve rapidly in response to environmental change. These finding suggest that songbird preen oil odors have the potential to function as chemosignals associated with mate recognition or reproductive isolation.

• Songbird chemosignals: volatile compounds in preen gland secretions vary among individuals, sexes, and populations

  Authors: Danielle J Whittaker, Helena A Soini, Jonathan W. Atwell, Craig Hollars, Milos V Novotny, Ellen D Ketterson

  Oxford University Press for the International Society for Behavioral Ecology, Behavioral Ecology. 01/2010; 21(3):608-614.

  Chemical signaling has been documented in many animals, but its potential importance in avian species, particularly songbirds, has received far less attention. We tested whether volatile compounds inChemical signaling has been documented in many animals, but its potential importance in avian species, particularly songbirds, has received far less attention. We tested whether volatile compounds in the preen oil of a songbird (Junco hyemalis) contain reliable information about individual identity, sex, or population of origin by repeated sampling from captive male and female juncos originating from 2 recently diverged junco populations in southern California. One of the populations recently colonized an urban environment; the other resides in a species-typical montane environment. The birds were field-caught as juveniles, housed under identical conditions, and fed the same diet for 10 months prior to sampling. We used capillary gas chromatography--mass spectrometry to quantify the relative abundance of 19 volatile compounds previously shown to vary seasonally in this species. We found individual repeatability as well as significant sex and population differences in volatile profiles. The persistence of population differences in a common environment suggests that preen oil chemistry likely has a genetic basis and may thus evolve rapidly in response to environmental change. These finding suggest that songbird preen oil odors have the potential to function as chemosignals associated with mate recognition or reproductive isolation. Copyright 2010, Oxford University Press.

• Phenotypic integration and independence: Hormones, performance, and response to environmental change.

  Authors: Ellen D Ketterson, Jonathan W Atwell, Joel W McGlothlin

  Integrative and comparative biology. 10/2009; 49(4):365-79.

  Hormones coordinate the co-expression of behavioral, physiological, and morphological traits, giving rise to correlations among traits and organisms whose parts work well together. This articleHormones coordinate the co-expression of behavioral, physiological, and morphological traits, giving rise to correlations among traits and organisms whose parts work well together. This article considers the implications of these hormonal correlations with respect to the evolution of hormone-mediated traits. Such traits can evolve owing to changes in hormone secretion, hormonal affinity for carrier proteins, rates of degradation and conversion, and interaction with target tissues to name a few. Critically, however, we know very little about whether these changes occur independently or in tandem, and thus whether hormones promote the evolution of tight phenotypic integration or readily allow the parts of the phenotype to evolve independently. For example, when selection favors a change in expression of hormonally mediated characters, is that alteration likely to come about through changes in hormone secretion (signal strength), changes in response to a fixed level of secretion (sensitivity of target tissues), or both? At one extreme, if the phenotype is tightly integrated and only the signal responds via selection's action on one or more hormonally mediated traits, adaptive modification may be constrained by past selection for phenotypic integration. Alternatively, response to selection may be facilitated if multivariate selection favors new combinations that can be easily achieved by a change in signal strength. On the other hand, if individual target tissues readily "unplug" from a hormone signal in response to selection, then the phenotype may be seen as a loose confederation that responds on a trait-by-trait basis, easily allowing adaptive modification, although perhaps more slowly than if signal variation were the primary mode of evolutionary response. Studies reviewed here and questions for future research address the relative importance of integration and independence by comparing sexes, individuals, and populations. Most attention is devoted to the hormone testosterone (T) and a songbird species, the dark-eyed junco (Junco hyemalis).

• Song types, song performance, and the use of repertoires in dark-eyed juncos (Junco hyemalis)

  Authors: Gon�alo C. Cardoso, Jonathan W. Atwell, Ellen D Ketterson, Trevor D. Price

  Oxford University Press for the International Society for Behavioral Ecology, Behavioral Ecology. 01/2009; 20(4):901-907.

  Song performance encompasses the idea of how physiologically demanding different songs are to sing, and this is thought to reflect the singing ability of individual birds. In the dark-eyed juncoSong performance encompasses the idea of how physiologically demanding different songs are to sing, and this is thought to reflect the singing ability of individual birds. In the dark-eyed junco (Junco hyemalis), each male has a repertoire of song types, some of which are shared with other males in the population. We used 4 measures of performance, based on trade-offs between song traits, to test if song performance is consistent among the song types making up the repertoire of individual males. We also tested if song types differ consistently in performance regardless of which males sing them. We found low but significant correlations of performance measures among the song types of individual males. This contrasts with highly consistent differences in performance among song types, regardless of which males sing them. We conclude that performance of single song types, as evaluated by trade-off--based measures of performance, gives little information about male singing ability. As song types differ in performance, we asked if males use the song types in their repertoires differently. We found that juncos use higher performance song types during bouts of more motivated singing, as evaluated by the length of songs, suggesting that song types may be preferentially used in different contexts depending on their performance. Copyright 2009, Oxford University Press.

• Inferring performance in the songs of dark-eyed juncos (Junco hyemalis)

  Authors: Gon�alo C. Cardoso, Jonathan W. Atwell, Ellen D Ketterson, Trevor D. Price

  Oxford University Press for the International Society for Behavioral Ecology, Behavioral Ecology. 01/2007; 18(6):1051-1057.

  Within bird species, songs differ in their attractiveness to females or effectiveness in male--male interactions. Some songs are more difficult to sing than others, and receivers may use a singer'sWithin bird species, songs differ in their attractiveness to females or effectiveness in male--male interactions. Some songs are more difficult to sing than others, and receivers may use a singer's performance of difficult songs as a means for evaluating the quality of the singer. The concept of song performance aims at quantifying how physiologically demanding are different songs. Using variation between song types of dark-eyed juncos, Junco hyemalis, we show that some song traits trade off with costly aspects of song output--short intervals between syllables or loud sound amplitude--suggesting that those traits are difficult to sing. First, after controlling for other traits, long syllables require longer intervals for recovery. This supports the idea that a measure of "respiratory performance" could be based on the relative lengths of syllables and intervals. Second, some syllable traits trade off strongly with sound amplitude, suggesting that these traits may be difficult to sing at high amplitudes. The ratio of frequency bandwidth and trill rate has been used to infer performance in other bird species, but we found no evidence that frequency bandwidth trades off with any aspect of song output in the junco. The negative association of bandwidth with trill rate may instead be a passive consequence of syllable length, with longer syllables randomly accumulating frequency modulation. We conclude that bird receivers may best evaluate how well a song is performed if they integrate multiple cues and discuss how researchers may similarly devise measures of song performance. Copyright 2007, Oxford University Press.

• Inferring performance in the songs of dark-eyed juncos (Junco hyemalis)

  Authors: Gonçalo C. Cardoso, Jonathan W. Atwell, Ellen D Ketterson, Trevor D. Price

  Within bird species, songs differ in their attractiveness to females or effectiveness in male–male interactions. Some songs are more difficult to sing than others, and receivers may use a singer'sWithin bird species, songs differ in their attractiveness to females or effectiveness in male–male interactions. Some songs are more difficult to sing than others, and receivers may use a singer's performance of difficult songs as a means for evaluating the quality of the singer. The concept of song performance aims at quantifying how physiologically demanding are different songs. Using variation between song types of dark-eyed juncos, Junco hyemalis , we show that some song traits trade off with costly aspects of song output—short intervals between syllables or loud sound amplitude—suggesting that those traits are difficult to sing. First, after controlling for other traits, long syllables require longer intervals for recovery. This supports the idea that a measure of “respiratory performance” could be based on the relative lengths of syllables and intervals. Second, some syllable traits trade off strongly with sound amplitude, suggesting that these traits may be difficult to sing at high amplitudes. The ratio of frequency bandwidth and trill rate has been used to infer performance in other bird species, but we found no evidence that frequency bandwidth trades off with any aspect of song output in the junco. The negative association of bandwidth with trill rate may instead be a passive consequence of syllable length, with longer syllables randomly accumulating frequency modulation. We conclude that bird receivers may best evaluate how well a song is performed if they integrate multiple cues and discuss how researchers may similarly devise measures of song performance.

• Song types, song performance, and the use of repertoires in dark-eyed juncos (Junco hyemalis)

  Authors: Gonçalo C. Cardoso, Jonathan W. Atwell, Ellen D Ketterson, Trevor D. Price

  Song performance encompasses the idea of how physiologically demanding different songs are to sing, and this is thought to reflect the singing ability of individual birds. In the dark-eyed junco (Song performance encompasses the idea of how physiologically demanding different songs are to sing, and this is thought to reflect the singing ability of individual birds. In the dark-eyed junco ( Junco hyemalis ), each male has a repertoire of song types, some of which are shared with other males in the population. We used 4 measures of performance, based on trade-offs between song traits, to test if song performance is consistent among the song types making up the repertoire of individual males. We also tested if song types differ consistently in performance regardless of which males sing them. We found low but significant correlations of performance measures among the song types of individual males. This contrasts with highly consistent differences in performance among song types, regardless of which males sing them. We conclude that performance of single song types, as evaluated by trade-off–based measures of performance, gives little information about male singing ability. As song types differ in performance, we asked if males use the song types in their repertoires differently. We found that juncos use higher performance song types during bouts of more motivated singing, as evaluated by the length of songs, suggesting that song types may be preferentially used in different contexts depending on their performance.