1 / 20

Midterm 1b Results

Midterm 1b Results. Mean = 26.4 Minimal score : 9 Maximal score: 37 62 students improved their score. Habitat Mosaic:. Source and Sink Populations:. High value habitat. Lower value habitat. Note: populations are too far apart, dispersal too infrequent, to establish IDF.

virote
Download Presentation

Midterm 1b Results

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Midterm 1b Results Mean = 26.4 Minimal score : 9 Maximal score: 37 62 students improved their score.

  2. Habitat Mosaic:

  3. Source and Sink Populations: High value habitat Lower value habitat Note: populations are too far apart, dispersal too infrequent, to establish IDF.

  4. Lowest elevation: lush forests, early snowmelt Highest elevation: near the timberline, late snowmelt Golden-mantled ground squirrel

  5. Metapopulations in the Sierra Nevada: At the highest elevation (2730 m): emergence from hibernation: late May newborn females take two seasons to mature females are larger at first reproduction average litter size: 4.5 18% of pregnancies survived to 1 year-old At the lowest elevation (1460 m): emergence from hibernation: early April newborns take one season to mature females are smaller at first reproduction average litter size: 5.3 18% of pregnancies survived to 1 year-old Bronson 1979

  6. Net reproductive rates: Highest elevation: R0 = 0.998 Lowest Elevation: R0 = 1.01

  7. A sink-population: A deme within a metapopulation where mortality exceeds birth rates. Habitats remain occupied only due to immigration. A source-population: A deme within a metapopulation where birth rates exceed mortality. Surplus individuals leave this habitat to settle (breed) elsewhere. Rescue Effect: The persistence of a deme with negative population growth through the influx of immigrants.

  8. Source and Sink Populations: High value habitat: R0 > 1 source Lower value habitat R0 < 1  sink Net migration

  9. Source and Sink Populations: N(t+1) = (1+b-d+e-i) N(t) Source population: b>d and i > e Sink population: b<d and i< e

  10. What are the implications for source-sink structure in a metapopulation for stability and persistence? • Do sink populations constitute a “drain” on a metapopulation? • Do sink populations still provide the safety in numbers? • Do sinks always remain sinks, and sources always sources? • Where do most individuals reside, in source or sink populations?

  11. Eastern kingbird (Tyrannus tyrannus) Rivers, floodplains, uplands and farmer’s fields

  12. Survivorship: The floodplain is the safest habitat for adult birds. Murphy 2001

  13. Reproductive success: Reproduction was slightly lower in the floodplain (Clutch sizes were the same but the floodplain had more egg predators. Murphy 2001

  14. Population growth rates: In the year of the study, populations growth was positive only on the floodplain. Floodplain >> Creek > Upland Murphy 2001

  15. Dispersal probabilities: From habitat: Most net dispersal happens from the floodplain to the creek. Creek and Upland are local sinks. The floodplain is the local source. Murphy 2001

  16. 50-year simulation based on actual population growth and dispersal parameters: Number of pairs Best model fit was achieved assuming a 5% immigration rate from the outside into the upland population. Still, the Charlotte Valley Kingbird population was predicted to decline: It is a regional sink!

  17. Number of pairs What does it take to stabililize the Charlotte Valley kingbird population? - 5% increase in survivorship in creek populations ? - The creek population became a local source, and stabilized the floodplain population.

  18. The Charlotte Valley kingbird study shows that: Most members of the metapopulation may live in sink populations, i.e. habitats that, if isolated, would not support the species. Relatively small improvements in a fraction of the total habitat, including a sink habitat, can help maintain larger portions of the metapopulation. Local source populations may be part of a metapopulation that is itself a sink on a larger spatial scale.

  19. Excel Worksheets: • Source-Sink populations

  20. Summary: • Not all demes would support viable populations on their own. • sink population = not viable by itself • source population = viable, generates dispersers • Even so, because sink populations also remain occupied most of the time, they • increase total population size (genetic diversity etc.) • reduce the risk of regional extinction • can help restart source populations after a local extinction. • Thus, sink populations can stabilize meta-populations.

More Related