1. METAPOPULATIONS II. So far, we have discussed animal examples almost exclusively. Metapopulations were first applied to animals Do they apply to plants?

2. Plants and metapopulations Difficult to tell if plants are part of a metapopulation- Seed bank recruitment vs. immigration Most patchy distributions seem to be only partly dependent on meta- population dynamics

3. Plants and metapopulations Seem to occur most commonly when plant inhabits an ephemeral and unpredictable patch Examples: badger mounds gaps in forest canopy

4. Example of plant metapopulation Water hyacinths (Eichhornia paniculata) in Brazil No seed bank Subpopulations come and go

5. Another example Primula vulgaris Lives under gaps in forest canopy Relies on seed dispersal to reach newly formed gaps Gap grows closed, subpopulation dies

6. Furbish’s Lousewort (Pedicularia furbishiae) Endemic to the St. John river in Maine Inhabits early-mid successional streambanks Requires ice and flooding to remove competing species Metapopulation model appears to apply

7. Example of source-sink in plants American Searocket Cakile edentula (Keddy, PA. 1982. Oecologia 52:348-355)

8. Plant metapopulations and invasions Metapopulation dynamics do explain the rapid spread of invasive species Small, outlying populations critical to continuing the spread These are called “nascent foci” Examples: spread of oak in Britain after ice age; many invasive exotic spp.

9. Genetics and metapopulations What are the consequences of these movements among subpopulations for the subpopulations’ genetic structure?

10. Factors influencing genetic diversity in metapopulations 1.Carrying capacity of patches 2. Rate of turnover events (extinction followed by recolonization) 3. Number of sources of colonists in the metapopulation 4. Total number of patches 5. Rate of gene flow among patches

11. Metapopulations and genetic diversity All of these elements combined: Genetic diversity is a function of patch size and colonization and extinction rates. A few large patches will have greater genetic diversity than more smaller ones with the same overall N.

12. Metapopulations and genetic diversity The greatest overall genetic diversity will theoretically be maintained when: Some subpopulations have frequent migration, but others are nearly isolated

13. Metapopulations and genetic diversity LOSS OF GENETIC DIVERSITY: If migration among patches does not overcome genetic drift If colonization rare and from only one or very few individuals (founder effect) Metapopulation structure does not guarantee genetic diversity!

14. A botanical example Campion (Silene alba) roadside weed in Virginia High turnover rate Poor dispersal Most subpopulations founded by few individuals Over time, marked loss of genetic diversity (McCauley et al. 2001)

15. Landscape ecology vs. metapopulations How are they different? Primarily in how they deal with the space between patches How are they similar? Both deal with interactions among habitat patches

16. Landscape ecology Patches vary in quality both across space and through time There are boundaries between patches Movements of organisms and materials among landscape elements determine connectivity Patch characteristics and dynamics are a function of location relative to features in the landscape as a whole.

17. Landscape ecology (Ricklefs and Miller 2000, p.344)

18. Metapopulation theory and conservation Metapopulation theory highlighted need to maintain connectedness among populations Shifted conservation focus away from treating each small population separately Emphasis on connectivity and movement

19. Biological corridors Movement of organisms across a landscape is not necessarily random Conservation attempts to maintain “travel routes” for organisms to disperse among subpopulations Example: Cougars in S. CA (Beier, P. 1995. JWM 5(:228-237)

20. Biological Corridors An experimental approach: Corridors direct movement for which taxa? How much effect to corridors have? Do corridors increase emigration? Created patches and corridors of early successional vegetation in pine plantations of South Carolina (Haddad et al. 2003. Ecology 84:609-615)

21. Haddad et al.’s Corridor Test Two butterfly species Two rodent species The seeds of four plant species Pollen of one plant species One species of bee Also examined data from other studies

22. Haddad et al.’s Corridor Test The plants and animals studied did use corridors for movement First demonstration that interpatch movement by plants affected by connectivity Overall, 68% more individuals moved to connected patches rather than unconnected ones

23. Haddad et al.’s Corridor Test Emigration didn’t appear to be affected by the landscape If you were going to leave, you did so regardless of the surroundings. No relationship between taxa and size of corridor effect

24. Summary The metapopulation model applies to plants Most applicable to ephemeral and unpre- dictable habitats Also applies to invasive species- “nascent foci” Genetic diversity is not necessarily maxi- mized in metapopulation Landscape ecology adds realism to metapopulation models

25. Summary continued Metapopulation theory emphasized population connectivity and movements of individuals between them Widely applied to reserve design in conservation