Invasive Species, part 1

Wed. Mar. 30

Seed Dispersers and the Ecologically Viable Population Size

Concept

http://www.birding.in/images/Birds/great_hornbill.jpghttp://bp0.blogger.com/_

Seed dispersers in Borneo

Seeds need to be moved some distance from the parent to survive. The greater the dispersal radius, the greater the chance that one will be dropped in a favorable place.

Seed dispersers thus have a major ecological role. What happens when they are decreased?

Ecologically Functional Populations

MacArthur's "Strong interactors" – species that have large effects regardless of their normal abundance (not depleted abundance). Also called "fundamentally important species", many are dominant or keystone species.

Large mature fig trees as strong interactors in tropical systems.

• Many species depend on these dominant species and numerous interactions center around them. For example, if fig abundance decreases, so do hornbills and some primates. • Hornbills and macaque monkeys are in turn strong interactors with other tree species and most importantly, they are strong interactors with fig trees! (it works both ways).

Imagine the cascade here if the figs or seed dispersers fail.

Ecologically Functional Populations

no effect

not enough to support largest sizes followed by accelerated loss of seed production

no seed bearing trees

average seed crop size# seeds dispersed

Dracontomelon dao

macaques only

Polyalthea glauca

Hornbills and siamangs compete

http://homepage.mac.com/wildlifeweb/mammal/siamang/

Why Is the EFP Concept Important?

1. Maintain community function.

2. EFP is generally larger than MVP -- will require larger areas to meet EFP and therefore more effective ecosystem conservation.

3. Ecocentrism.

End of material for Exam #2

Invasive Species and their Implications for Conservation

Examples of Accelerating

Effects of Invasives

Conservation Implications

Brown tree snake induced electrical outages on Guam.

Acceleration of invasives in SF Bay

Impacts of Invasives

http://www.hear.org/images/captured_snakes_640x480.jpg

http://www.wettropics.gov.au/st/rainforest_explorer/Resources/Images/animals/snakes/BrownTreeSnake.jp

Introduced predatorsDue to the important role that predators play in communities, unchecked introduced predators can greatly alter structure and function – and they can cause extinctions. This is especially a problem with islands where many species may be endemics and could easily be driven to world-wide extinction.

Guam is an isolated, mid-Oceanic island

Guam and Brown Tree

Snakes

Boiga irregularis was introduced, probably as a boat stowaway shortly after the end of WWII. It originated in the SW Pacific.

For more information: http://www.fort.usgs.gov/Resources/Education/BTS/

Note the severe reduction in diversity. Note also the shift towards predominance of introduced species (asterisk).

The Effects of Zebra Mussels

http://www.epa.gov/glnpo/atlas/images/photo405.gif

http://webhost.bridgew.edu/dpadgett/zebra%2520mussel%2520pic.jpg

introduced competitorsplanktonic vs. host dispersed

The Atlantic Ctenophore in the Black Sea

http://www.underwaterphotography.com/Upload%5CUP%5CCompetition%5C25174.jpg

http://www.imagequest3d.com/pages/general/news/blackseajellies/Beroe%20eating%20Mnemiopsis.jpg

Beroe eating Mnemopsis

Mnemopsis-caused reductions in commercially important species.

One Invasive Helping Another

1. Gulf of Maine

2. Remove ground fish

3. Increase urchins

4. Decrease kelp

5. Harvest urchins

6. Kelp did not return completely and Asian macroalga and a bryozoan invade

7. Bryozoans encrust kelp causing breakage in winter storms, opens area for alga invasion.

8. Asian alga spread by breakage in winter storms

Effects on Other Species' Behaviors

http://www.flickr.com/photos/unclejefejefe/3367700309/in/photostream/

Pollinators such as bumblebees judge nectar sources by a number of criteria (specific choices are not innate). If the invader produces nectar that is more desirable to a native pollinator, there will be fewer visits to the native and lower seed set – an interesting and very significant form of competition.

Change in Preference

and Dependence

http://upload.wikimedia.org/wikipedia/commons/3/3b/Plantago_major2.jpg

http://floralore.com/fauna/butterflies/euphydryasEditha.jpg

This appears to be selection for a genetic preference (unlike bumblebees). What is the (immediate at least) effect of attempting to remove the non-native plantain?

Genetic Impacts

http://www.birdcapemay.org/gallery/

http://www.flickr.com/photos/23505652@N03/3229683119/

Hybrids

http://sdakotabirds.com/species/photos/american_black_duck.jpg

American Black Duck (NE native)

http://www.haryana-online.com/images/Birds/BhupendraYadav/Mallard.jpg

Mallard F&M (Eurasian)

Invasives and Ecosystem

Damage -- Nutria in North America

http://www.sivae.it/images/nutria%203.jpg

http://nas.er.usgs.gov/ARCIMS/interactive/interactive.asp?SpeciesID=1089

http://www.iiseagrant.org/EXOTICSP/nutria.htm

Invasives and Ecosystem

Damage

http://www.scn.org/savelake/NL.Spr.Sum.2006/NL.Spr.Sum.2006_files/Current_Nutria_Damage_5_06.JPG

http://www.conservewildlife.org/gfx/bad_marsh.jpg