Understanding Your Neighbors: Geographic Variation in LRS and SRS of Dark-eyed Juncos (Junco hyemalis)

Student: Nate Dedek
Mentor: Dustin Reichard (Department of Zoology)

I’m studying how short-range songs and long-range songs vary geographically in Dark-eyed juncos (Junco hyemalis).  Moreover, I’m determining if short-range songs are more unique than long-range songs to each population of dark-eyed juncos dispersed across the western United States.  If so, then it can be assumed that these short-range songs can be used as a mating barrier between the different populations.  Mating barriers can eventually lead to the formation of different species which may have a major impact on the evolution of dark-eyed juncos.

Nearly all species of songbird produce high-amplitude songs that can be detected over long distances, which have fittingly been classified as long-range song (LRS). These songs have been well documented in numerous species and most commonly function in mate attraction and territory defense.  Recently, researchers have begun to investigate low-amplitude songs that are intended for receivers in the immediate vicinity of the signaler.  This second class of song has been referred to as short-range song (SRS).  Research on SRS is sparse, thus its overarching function or even how it varies between species remains poorly understood.  For Dark-eyed juncos (Junco hyemalis) both LRS and SRS appear to be species-typical.  Species-typical songs tend to vary across different geographic scales, sometimes creating dialects between different populations.  These dialects have the potential to become barriers to reproduction that could in turn lead to speciation.  LRS is known to vary significantly among subspecies and populations of Dark-eyed juncos but no distinct dialects exist among them.  Little to no research has been conducted to assess variation in SRS within and among these populations.  This raises the question as to whether or not SRS is more distinct than LRS among different populations.  I will analyze multiple acoustic features to determine if SRS is more distinct than LRS between five subspecific populations of dark-eyed juncos.  Given its role in close-proximity courtship interactions, I predict that SRS will be under less selective pressure for efficient transmission and greater selective pressure from female mating preferences than LRS.  That is, if SRS is less constrained by sound transmission then it would be expected that SRS is more labile and will differ more significantly between populations.  These results may help better our understanding of the development of SRS and its role in assortative mating.