Song in the city: the effects of urban noise on communication patterns and population genetics of an Australian passerine

Transcription

1 Song in the city: the effects of urban noise on communication patterns and population genetics of an Australian passerine Dr. Dominique Potvin Museum Victoria

2 Overview Introduction Acoustic Adaptation Silvereyes Part I: Urban Silvereyes The role of noise, morphology, genetics, meme use and plasticity Part II: Island Silvereyes The role of morphology, genetics, founder effects and habitat Conclusions

3 Introduction: The Basics What is song? complex learned trait usually males mate attraction, territory defense dialects Calls: not learned (innate?), used for contact/alarm, both sexes

4 Introduction: The Basics Song Call

5 Introduction: The Basics Acoustic Adaptation Morton 1975 vocalizations should be modified to minimize degredation by environment HOW? sing simpler songs, avoid frequencies present in background noise Nicholls & Goldizen 2006

6 Introduction: The Question what shapes a song?

7 Part I: Urban silvereyes birds sing higher in cities: great tits, blackbirds, song sparrows acoustic adaptation? songs in the same frequency range as urban noise (1-4kHz) may not be heard singing higher avoids masking (overlapping) by urban noise. BUT???

8 PART I : urban silvereyes Questions are urban and rural silvereye vocalizations different? (How?) possible mechanisms behind the change Cultural evolution, plasticity, morphological/genetic change

9 My study species: Zosterops lateralis abundant expansive range island colonization song 2-8 khz DNA microsatellites three vocalization types

10 PART I : urban silvereyes Methods the field study

11 PART I : urban silvereyes Results silvereyes sing AND call at a higher pitch in cities and sing slower Potvin et al Proc. R. Soc. B.

12 PART I : urban silvereyes Silvereye sounds

13 PART I : urban silvereyes How about alarm calls? Urban silvereyes have LOWER alarm calls!

14 % trills in songs PART I : urban silvereyes Are urban silvereyes using different syllables? urban silvereyes use similar memes in songs: slower syllables, more trills Urban Rural Potvin & Parris Ecol & Evol

15 PART I : urban silvereyes Do urban silvereyes have their own city dialect? RDA: habitat features (urbanization, noise) predict 24% of repertoire similarity between populations this is comparable to geographic effects on dialect formation! Potvin & Parris Ecol & Evol

16 What s going on? Are city silvereyes evolving? Can look at genetic differences, body size/shape differences Are silvereyes just really flexible? Do they respond quickly to noise?

17 Are there morphological/genetic differences? high gene flow between urban/rural populations (Fst) urban silvereyes aren t more or less inbred urban and rural silvereyes look pretty much the same Potvin et al Evol Ecol.

18 Results silvereyes won t sing in captivity on demand silvereyes also don t respond to playback in captivity two silvereyes won t do much of anything in captivity conclusion: Silvereyes are uncooperative and difficult (albeit cute).but then!

19 Methods captive study

20 Call frequency (Hz) Results the captive study silvereyes adjust calls immediately in response to noise whether low OR high Quiet Low F.N. High F. N. Potvin & Mulder Behav Ecol: in Press

21 Conclusions - Part I urban and rural silvereyes are morphologically and genetically similar urban silvereyes sing/call higher, are able to immediately adjust the pitch of vocalizations to avoid noise = real time flexibility urban silvereyes use similar memes, and have possibly converging repertoires = acoustic adaptation via cultural evolution!

22 Conclusions - Part I THIS IS NOT A RULE alarm calls are LOWER in cities, and wellmasked by urban noise maybe some changes are/seem maladaptive physiological, developmental effects of living in the city (i.e. stress when developing vocal apparatus)? different current predator risks in urban environment?

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24 Part II Island Silvereyes islands are ideal places to study song evolution: isolated populations should show rapid acoustic adaptation to environment can also consider the effects of genetic isolation/colonization, environment and connectivity on song dialect

25 Part II: Island Silvereyes Isolated populations should show rapid acoustic adaptation to their environments However, other factors can play into an island population s dialect Cultural drift/founder effects Morphological/genetic changes

26 PART II : island silvereyes Questions how does an island dialect develop? Are island repertoires well-suited to/predicted by their environment (Acoustic Adaptation)? how does morphology affect song? do song repertoires experience cultural drift and founder effects? Meme flow? are these associated with genetic founder effects?

27 PART II : island silvereyes Methods: The island study

28 PART II : island silvereyes Results: The island study silvereyes on islands are BIGGER this size difference coincides with lower frequency songs, contact calls AND alarm calls

29 PART II : island silvereyes Results: the island study island dialect similarity is predicted by habitat (.45), geographic proximity (0.32), genetic similarity (0.44) effective founder sizes of islands do not affect repertoire sizes (no evidence for repertoire bottleneck)

30 PART II : island silvereyes Conclusions Part II island dialects may be affected by morphology (affecting frequency) genetic connectivity & habitat both predict some level of repertoire similarity no evidence for lasting bottleneck or founder effects on song

31 Discussion what factors contribute to the evolution of vocalizations? 1. morphology 2. genetics (?) 3. ENVIRONMENT 4. plasticity 5. sexual selection

32 Discussion environment plays a large part in the structure of vocalizations plasticity allows vocalizations to change: birds can be selective in their meme use (cultural evolution), adjust tempo or frequency real-time/within lifetimes sometimes, changes may appear maladaptive, must consider other possibilities also important to consider isolation, morphology and founder effects when analyzing song

33 A few interesting unanswered questions: how does city living affect development? stress levels? song learning? exactly what syllables are kept in specific habitats? are different syllables sexy in different habitats? what are the implications for changed songs and calls in cities? Can rural and urban birds communicate effectively?

34 Acknowledgments Supervisors: Raoul Mulder, Kirsten Parris Jeremy Kruckel Many many banders, local experts and rangers Academic help: Mick McCarthy, Henrik Brumm & lab; Sonya Clegg; Gonçalo Cardoso; Evolution and Behaviour Group at U of M Funding: Holsworth WRF, Birds Australia (Victoria, Tasmania and national groups, now Birdlife), Australian Geographic Society, University of Melbourne

35 . Questions?