Outline for Lectures 9 and 10

1. Outline for Lectures 9 and 10 Edge effects Assessing patch quality in a fragmented landscape Source vs sink populations Ecological traps Scaling up and predicting population dynamics

2. Habitat Quality Source (good habitat) areas where local reproductive success is greater than mortality  >1 Sink (poor habitat) areas where local productivity is less than local mortality  <1

3. Source or sink Simplest case - one patch Finite rate of pop’n growth,  = PA+PJ Example 0.76 0.58 6.33/pair PA - Adult survival during year PJ - Juvenile survival rate during year  - Number juveniles produced per adult per year Q. Is this a source or a sink pop’n

4. What happens when good animals love poor habitats? edges?  an ecological trap

5. Sources sinks and population dynamics Habitat quality High  >1 Low  <1 Habitat selection Preferred Avoided source sink What do individuals do and what happens to populations At low density At high density

6. But so is light reflecting off tarmac So mayflies frequently lay eggs on asphalt BUT Animals can be fooled Mayflies are attracted to horizontally polarized light Because light reflected from a water surface is polarized

7. Ecological traps Habitat 1 - HIGH quality has attributes ABC Habitat 2 - medium quality has attributes CDE but not AB Natural selection leads to preference for habitat with AB Habitat 1MODIFIED---> LOW quality still has attributes ABC Habitat 2 - medium quality has attributes CDE but not AB Preference based on cues AB is maladaptive - Suitable but avoided

8. Ecological traps and population dynamics Habitat quality High  >1 Low  <1 Habitat selection Preferred Avoided source trap source sink What happens to individuals and populations in the modified environment At low density At high density

9. Ecological traps and population dynamics Prior to modification A better quality than B …. Expected breeding success in terr n ___ Mean breeding success of population After modification A worse than B but A preferred Open circles - expected success Lower line - mean breeding success Kokko and Sutherland 2001 Evol Ecol Research 3: 537-551

10. Ecological traps and population dynamics Kokko and Sutherland model shows both reduced reproduction or mortality can cause traps initial population size is important in determining the outcome there is a threshold level of trap habitat that will result in pop’n extinctions

11. Ecological traps: how good is the evidence? Habitat edges - Birds Preference Fitness Payoff Nests/ha Distance to edge (m) Flaspohler et al 2001 Q. Any concerns about the conclusion?

12. Ecological traps: how good is the evidence? Habitat edges - Insects Egg case Mantid (Stagmomantis limbata)

13. Ecological traps: how good is the evidence? Habitat edges - Mantids Preference Payoff Predation rate Egg case density /ha Ries and Fagan 2003 Ecol Appl 28 567-572

14. Ecological traps: how good is the evidence? Exotic species Lonicera spp Bush honeysuckles

15. Payoff Ecological traps: how good is the evidence? Exotic species Preference

16. Conclusion Traps are created by diverse processes in many habitat types across a diversity of spatial scales landscape, within patches, within territiries (eg selecting nest sites) SO potential impact is ENORMOUS

17. But identifying ecological traps is DIFFICULT AND DATA INTENSIVE • need to show • Habitat is preferred • Habitat is a sink need to distinguish from pseudosink habitat with low productivity /survival due to high densities

18. Sources and sinks - scaling up to populations Pika Age structured population Juv 1 2 3 Two habitats Meadow and Snowbed

19. Meadow snowbed Nt+1/Nt Sources and sinks - scaling up to populations Pika Age structured population Juv 1 2 3 Two habitats Meadow and Snowbed Birth Juv Adult  Meadow 1.72 0.3 0.43 0.89 Snowbed 0.33 0.21 0.17 0.12 Immigration - 3x more immigrants in snowbeds than meadow

20. Sources and sinks - scaling up to landscapes DDT caused pop’n crashes in the 50’s Management strategies banning of DDT and reintroductions

21. With captive release Without Sources and sinks - scaling up to landscapes Post DDT Northern pop’n -  > 1 Coastal pop’n -  < 1 Wootton and Bell 1992 Source-sink dynamics should lead to recovery

22. Sources and sinks - scaling up to landscapes DATA - 30 BBIRD sites 17 states 22 spp - National Landcover Dataset - 21 types Nest parasitism - increases with the amount of developed land within a 20 km radius Predation - edge effect in East - increases with amount of developed land within a 10 km radius Combined ---> landscape effect - productivity decreases with amount of developed land within 10 km radius NEXT STEP - link landscape effects to  - based on  = PA+PJ -  declines with amount of developed land

23. Source sink model and Breeding bird survey data suggest Ovenbird pop’ns are growing Wood thrush pop’ns are declining Lloyd et al 2005 Ecol Applic 15: 1504-1514

24. Summing up Habitats vary in quality Source habitats produce an excess of individuals These individuals can disperse to Sink habitats where productivity is less than mortality Demographic rates can vary temporally Source-sink dynamics have implications for identifying critical habitat

25. Questions you should be able to discuss. What are the issues about using presence/absence/abundance data to identify critical habitat? What data is needed to determine whether a habitat acts as a source or a sink? If animals can evaluate habitat quality how will changes in overall population size affect source and sink populations?