Summary of lecture 8 Habitat loss -----> fragmentation an increase in patch number a decrease in patch size increasing patch isolation higher edge:core ratios Fragmentation can have -ve and +ve effects The relative importance of habitat loss and habitat configuration can be assessed using statistical models

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

Fragmentation - understanding the process Rosenberg 1999 Tanagers - a continental approach

1057 sites measured Forest cover Patch size Isolation Edge Point counts assessed Tanager Cowbird avian predators other predators

Probability of occurrence Geographic area. Scarlet ___ Summer …… Western Low… Fragmentation gradient …high Q. Which species would you expect to be most impacted by fragmentation?

PC1 - forest cover/patch size/isolation Probability of occurrence Low… Fragmentation gradient …high Q.What do you conclude about fragmentation effects on tanagers

Biotic processes at edges Predation - additional factors Conclusion: The landscape surrounding the patch influences predation effects at edges Host abundance Proportion of nests depredated Amount of forest remaining 90% Donovan 1997 Ecology

Biotic processes at edges Parasitism - additional factors Conclusion: The landscape surrounding the patch influences cowbird abundance and parasitism rates % forest cover % forest cover Cowbirds per point count % nests parasitized Thompson et al. 2000

Edge effects on predation and parasitism in Eastern and Western Landscapes Data: 656, 1122, nests 23 species Cavitt and Martin 2002 Studies in Avian Biol 25 East West Daily mortality rate Fragmented Unfragmented

Edge effects on predation and parasitism in Eastern and Western Landscapes Data: >10000 nests 23 species Cavitt and Martin 2002 Studies in Avian Biol 25 East West Proportion of nests parasitized Fragmented unfragmented

Biotic processes at edges Predation at edges 64 experiments later Overall - edges have a significant effect But N America > Central America Deciduous forest > coniferous forest = tropical forest Effect varies with habitat in matrix

Question for discussion Why does fragmentation have different effects on predation and parasitism rates east and west of the Rockies?

Habitat loss ---> fragmentation ---> patches that vary in size/shape/isolation quality EXAMPLES

Forestry - determining best practises Group retention harvesting 50% retained 30% retained 10 % retained How do we assess how to cut up the block or the quality of the patches that are left ??

Protecting kit foxes in California 8 sites Sites vary How do we assess which to protect first?

Protecting murrelet breeding habitat BC - >130 WHA’s have been established for murrelets Forest habitat in Desolation Sound (green) Nests (red) How do we decide what forest patches to protect?

Habitat loss ---> fragmentation ---> patches that vary in size/shape/isolation quality Q. How would you assess quality or decide what patches to protect?

One approach - we could protect preferred habitat Density Presence/Absence Preference is often evaluated based on usage relative to availability high usage habitat is preferred low usage is avoided

Use of density or presence/absence to assess habitat quality or decide what patches to protect assumes animals are ideal (have perfect knowledge) animals are free (not constrained) Morris 1996 Oikos 75: Eg1 White footed mice Prefer forest over edge Preference has a fitness pay-off Survival rate is higher Eg2 Spanish Imperial Eagle Ferrer and Donozar 1996 Ecology 77 Prefer cork oak/stone pine over marsh and coastal dunes Preference has a fitness payoff Breeding success is greater

Use of density or presence/absence to assess habitat quality or decide what patches to protect assumes animals are ideal (have perfect knowledge) animals are free (not constrained) so density is correlated with rs and survival and preferred habitats can support source populations Source areas where local reproductive success is greater than mortality Sink areas where local productivity is less than local mortality

Source or sink Simplest case - one patch Finite rate of pop’n growth, = P A +P J  P A - Adult survival during year P J - Juvenile survival rate during year  - Number juveniles produced per adult per year Example /pair Q. Is this a source or a sink pop’n

How do animals assess habitat suitability? Internal information - habitat imprinting Direct habitat assessment Indirect habitat assessment - presence of conspecifics (“social attraction”) - performance of conspecifics - (“public information”) - use of cues that predict quality

How do animals assess habitat suitability? - habitat imprinting False clownfish Imprint to chemical cues in the nest Use these cues to find host anemones Peregrine falcon Ind’s that fledge from buildings are more likely to breed on builings than cliffs and vice versa

How do animals assess habitat suitability? - direct habitat assessment Koalas assessDippers assess plant chemistry invertebrate abundance

How do animals assess habitat suitability? - the use of cues that predict habitat quality Periodical cicada Females use canopy openness to select where they lay eggs.

Canopy openness predicts long term tree growth rapid root development and the food supply for the developing nymphs

How do animals assess habitat suitability? - Presence of conspecifics (“social attraction”) From polychaetes to birds

How do animals assess habitat suitability? - Performance of conspecifics (“public information”) First time breeders select sea cliffs based on their productivity in the previous year Older breeders emigrate from the least productive cliffs and settle at the most productive (Danchin et al 1998)

You should be able to Design an experiment to test for edge effects Discuss why edge effects vary Collect data to evaluate patch quality Understand any assumptions made when using this data Be able to distinguish between a source and a sink population NEXT – bad decisions