In the Light of Evolution Volume VI: Brain and Behavior (2013) / Chapter Skim
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11 To Flock or Fight: Neurochemical Signatures of Divergent Life Histories in Sparrows--James L. Goodson, Leah C. Wilson, and Sara E. Schrock
11 To Flock or Fight: Neurochemical Signatures of Divergent Life Histories in Sparrows--James L. Goodson, Leah C. Wilson, and Sara E. Schrock
Pages 193-210
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From page 193... ...
and medial amygdala of field sparrows, but not song sparrows. These spe cies differences likely relate to flocking rather than the suppression of winter aggression in field sparrows, because similar winter differences were found for two other emberizids that are not territorial in winter -- Department of Biology, Indiana University, Bloomington IN 47405.
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From page 194... ...
. Using four emberizid songbird species that have evolved divergent life-history strategies, we here examine seasonal variation and evolutionary diversity in six neurochemical systems and demonstrate links of those systems to both winter flocking and territorial aggression.
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From page 195... ...
. Consistent with these findings, septal VT infusions reduce territorial aggression in emberizid sparrows and estrildid finches (Goodson, 1998a,b)
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From page 196... ...
. Alternatively, given that neurochemical circuits that promote winter flocking may also be involved in other affiliation behaviors that are expressed in the breeding season, such as pair bonding and caring for young, we hypothesized that field sparrows may maintain some neuroendocrine systems year-round that show a winter collapse in song sparrows.
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From page 197... ...
a winter increase in flocking field sparrows that is not exhibited by song sparrows, or (ii) the maintenance of some neuroendocrine systems yearround in field sparrows that show a winter collapse in song sparrows.
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From page 198... ...
That is, spring VIP OD measures in the PVN, AH, and septal areas are actually higher in song than in field sparrows. Furthermore, as described in the following section, AH and CcS measures correlate positively with spring aggression, which we did not anticipate for variables that promote flocking.
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From page 199... ...
CRH-ir fibers in the LSc.d of field and song sparrows collected in spring and winter, showing increased innervation density in winter field sparrows.
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From page 200... ...
CRH-ir fibers in the anterior MeA of field and song sparrows collected in spring and winter, showing increased innervation density in winter field sparrows.
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From page 201... ...
. However, relevant to our focus on divergent life histories, we were particularly interested in determining whether measures of neurochemistry predicted species differences in aggression, given that that field sparrows are substantially less aggressive during the breeding season than are song sparrows.
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From page 202... ...
in the PVN, and VIP-ir OD in the BSTm of field and song sparrows. Right panels show corresponding data for juncos and towhees.
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From page 203... ...
Regression analyses reveal significant negative correlations with PC1 (and thus positive correlations with aggression) for VIP OD in the AH and CcS; ARO OD in the posterior MeA (with a strong trend in the anterior MeA, as well)
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From page 204... ...
. CG, central gray; ICo, nucleus intercollicularis; SPa, subparaventricular area.
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From page 205... ...
, those of seasonal flocking have not, and brain mechanisms that evolve in relation to species differences in the intensity of territorial aggression are likewise unknown. We now show that in emberizid songbirds, several neurochemical variables reflect seasonal shifts from territoriality to flocking, whereas numerous other variables correlate with both individual and species differences in territorial aggression.
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From page 206... ...
. The present findings are strongly consistent with those in estrildids: field sparrows show a significant increase in MT-ir fiber density in the LSc.d during winter, when they form flocks, whereas the year-round territorial song sparrow does not.
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From page 207... ...
Species Differences in Territorial Aggression As shown here, field sparrows are significantly less aggressive than are song sparrows. Thus, the present dataset allows us to identify neurochemical mechanisms that may have evolved in relation to territorial behavior, because we are able to correlate measures of neurochemistry with aggressive behavior across both individuals and species.
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From page 208... ...
the maintenance of some neuroendocrine systems year-round in flockers that show a winter collapse in nonflockers. The first pattern is exhibited in the MT and CRH innervation of the pallial LS and anterior MeA, and in the colocalization of MT and CRH in the PVN.
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From page 209... ...
Sparrow series 1 was labeled using sheep anti-TH (Novus Biologicals) , guinea pig anti-VP (Bachem)
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From page 210... ...
Note that although the Benjamini-Hochberg correction initially applies a Bonferroni criterion, it adjusts α in a stepwise manner for remaining tests as long as P values continue to be significant at each step. ACKNOWLEDGMENTS We thank Francisco Ayala, John Avise, and Georg Striedter for inviting this contribution; Jacob Callis, Brian Gress, Alexis Howard, Aubrey Kelly, Melissa Knisley, and Brittany Welsh for assistance with immunocytochemistry and/or cell counts; Ellen Ketterson, Dawn O'Neal, and Ryan Kiley for assistance with collections; and Drew King and Meredith West for property access; Harold Gainer for the donation of antiserum.
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