Danielle June Whittaker

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• 10Publications

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Publications

• 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. in press.

• Role of Testosterone in Stimulating Seasonal Changes in a Potential Avian Chemosignal.

  Authors: Danielle J Whittaker, Helena A Soini, Nicole M Gerlach, Amanda L Posto, Milos V Novotny, Ellen D Ketterson

  Journal of chemical ecology.

  Songbird preen oil contains volatile and semivolatile compounds that may contain information about species, sex, individual identity, and season. We examined the relationship between testosterone (T)Songbird preen oil contains volatile and semivolatile compounds that may contain information about species, sex, individual identity, and season. We examined the relationship between testosterone (T) and the amounts of preen oil volatile and semivolatile compounds in wild and captive dark-eyed juncos (Junco hyemalis). In wild males and females, we observed an increase in volatile compound relative concentration early in the breeding season. This increase mirrored previously described seasonal elevation in T levels in wild males and females, suggesting a positive relationship between hormone levels and preen gland secretions, and a possible role for these secretions in signaling receptivity. In females, the greatest relative concentrations of most compounds were observed close to egg laying, a time when steroid hormones are high and also the only time that females respond to an injection of gonadotropin-releasing hormone with a short-term increase in T. In a study of captive juncos held on short days, we asked whether the seasonal increases observed in the wild could be induced with experimental elevation of T alone. We found that exogenous T stimulated the production of some volatile compounds in non-breeding individuals of both sexes. However, of the 15 compounds known to increase during the breeding season, only four showed an increase in relative concentration in birds that received T implants. Our results suggest that testosterone levels likely interact with other seasonally induced physiological changes to affect volatile compound amounts in preen oil.

• 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. 22(1256):1263.

• Natural Selection on Testosterone Production in a Wild Songbird Population.

  Authors: Joel W McGlothlin, Danielle J Whittaker, Sara E Schrock, Nicole M Gerlach, Jodie M Jawor, Eric A Snajdr, Ellen D Ketterson

  The American naturalist.

  Abstract: Because of their role in mediating life-history trade-offs, hormones are expected to be strongly associated with components of fitness; however, few studies have examined how naturalAbstract: Because of their role in mediating life-history trade-offs, hormones are expected to be strongly associated with components of fitness; however, few studies have examined how natural selection acts on hormonal variation in the wild. In a songbird, the dark-eyed junco (Junco hyemalis), field experiments have shown that exogenous testosterone alters individuals' resolution of the survival-reproduction trade-off, enhancing reproduction at the expense of survival. Here we used standardized injections of gonadotropin-releasing hormone (GnRH) to assay variation in the testosterone production of males. Using measurements of annual survival and reproduction, we found evidence of strong natural selection acting on GnRH-induced increases in testosterone. Opposite to what would be predicted from the survival-reproduction trade-off, patterns of selection via survival and reproduction were remarkably similar. Males with GnRH-induced testosterone production levels that were slightly above the population mean were more likely to survive and also produced more offspring, leading to strong stabilizing selection. Partitioning reproduction into separate components revealed positive directional selection via within-pair siring success and stabilizing selection via extrapair mating success. Our data represent the most complete demonstration of natural selection on hormones via multiple fitness components, and they complement previous experiments to illuminate testosterone's role in the evolution of life-history trade-offs.

• 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. 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.

• Behavioral responses of nesting female dark-eyed juncos Junco hyemalis to hetero- and conspecific passerine preen oils

  Authors: Danielle J. Whittaker, Dustin G. Reichard, Amy L. Dapper, Ellen D. Ketterson

  Journal of Avian Biology. 40(579):583.

• Resolution of the Hylobates phylogeny: congruence of mitochondrial D-loop sequences with molecular, behavioral, and morphological data sets.

  Authors: Danielle J Whittaker, Juan Carlos Morales, Don J Melnick

  Molecular phylogenetics and evolution. 45(2):620-8.

  Gibbons of the genus Hylobates likely speciated very rapidly following isolation by rising sea levels during the Pleistocene. We sequenced the hypervariable region I (HV-I) of the mitochondrialGibbons of the genus Hylobates likely speciated very rapidly following isolation by rising sea levels during the Pleistocene. We sequenced the hypervariable region I (HV-I) of the mitochondrial D-loop to reconstruct the phylogeny of this group. Although the results clearly supported monophyly of each of the six species, the relationships among them were not clearly resolved by these data alone. A homogeneity test against published data sets of a coding mitochondrial locus (ND3-ND4 region), behavioral characters (vocalizations), and morphological traits (including skeletal and soft tissue anatomy) revealed no significant incongruence, and combining them resulted in a phylogenetic tree with much stronger support. The Kloss's gibbon (H. klossii), long considered a primitive taxon based on morphology, shares many molecular and vocal characteristics with the Javan gibbon (H. moloch), and appear as the most recently derived species. The northernmost species (H. lar and H. pileatus) are the most basal taxa. These data suggest that ancestral gibbons radiated from north to south. Unlike other markers, the HV-I region can accurately identify members of different gibbon species much like a DNA barcode, with potential applications to conservation.

• Molecular phylogenetic affinities of the simakobu monkey (Simias concolor).

  Authors: Danielle J Whittaker, Nelson Ting, Don J Melnick

  Molecular phylogenetics and evolution. 39(3):887-92.

• Conservation action plan for the Mentawai primates

  Authors: Danielle J. Whittaker

  Primate Conservation. 20(95):106.

• New population estimates for the endemic Kloss’s gibbon Hylobates klossii on the Mentawai Islands, Indonesia

  Authors: Danielle J. Whittaker

  Oryx. 39(458):461.