Hey guys, look! An Ecosystem Service!

My favorite part of this was the Fark headline that linked me to it: Modern farmers shocked to find out that what every agricultural civilization since the dawn of time believed to be true is actually right: Flooding your fields before planting is good for the crops.

http://abcnews.go.com/Business/wireStory?id=10663809

Functional Ecosystems and Biodiversity Buzzwords

Paul Goldstein argues in this refreshing paper that conservationists and land managers are getting too far away from knowledge of natural history, and thus, may not be reaching their stated goals. He argues that one of the main issues with having faulty management stems from definitions which are too vague, or lack species specific information. He discusses the faults with creating boundaries or managing off of ecosystem processes and functions, without looking at the species at hand.

In the discussion of ecosystem management he points out that the older idea of trying to save most area possible by using one species (e.g. grizzly bear) does not take into account micro or unique habitats which may be important but are not within the range of the target species. From this, he then goes on to discuss, what is ‘ecosystem management anyway’? The definition of this has been lost in debate and become more and more generalized, leading to the term being used in almost any way possible. For example, he calls out the insane idea of a Mass. Politian including ATVs in plans to manage a beach area! He also discusses how even now, this “ecosystem management” often ends up being single species management. He defines ecosystem management as including the following 3 ideas: 1) to protect biological diversity, one must safeguard the context in which ecological and evolutionary processes persist. 2) simple species richness is not a sufficient gauge of management success. And 3) Management must be planned and conducted for the long term.

He then goes on to discuss what seems to be a subject he feels quite passionate about (and rightfully so, as it is his profession), the idea of removing all life history knowledge and simply characterizing communities through abstract, theoretical numbers (e.g. diversity, rank abundance). He points out the obvious example of a community appearing “healthy” and a goal being met based on the dominance of a single invasive species increase a sites abundance.

The next section discusses managing for emerging properties in structure and function. There are many faults in this approach, for example, strictly managing for fire through prescribed burns, though it may sound like a good idea, could result in elimination of the most rare species, and a homogenous landscape. Managing for function also has many faults, and here, his paper ties in with Naeem’s. He demonstrates how managers have used ecological redundancy to ignore species ID and just manage for function. As we learned from Naeem, redundancy, is important and thus, species should be considered.

Conservation biology and land management should not be characterized by “buzzwords” and lack of defined goals. In order to be successful, managers must create defined goals which account for species life histories in the area or habitat which is being conserved. Although knowing each organism in each habitat is likely not feasible, in the least, a good understanding of species at hand will greatly increase the success of efforts.

Now regarding out class discussion – Is Dr. Goldstein just a “bug counter” who is against models and theoretical progress? No, he is simply reminding us all of the dangers of drifting too far from the base of what we want to preserve. Although management would likely never be feasible without the use of generalized ideas, a mixture of both models/theory/ and natural history will likely give us the best results.

Algae and Island Biogeography

Matt and I recently attended the Northeast Algal Society (NEAS) conference and while we were there, we heard a really interesting talk by Dr. Craig Schneider of Trinity College discussing the algal flora of Bermuda and how it relates to Island Biogeography.

Bermuda is a small island far off the coast of the US. It is only about 20mi² and has a tropical climate (you may think it is redundant to state that it's climate is tropical, however, this is not a trivial fact when it comes to discussing the marine algal species present). Dr. Schneider's talk was a summary of many years of work, spread out over several publications that have compared an initial report of all marine algal taxa present on the island (published in the 1920's) to a modern-day analysis of the taxa present.
First the unimpressive news: After sampling and sampling and sampling for many years in Bermuda, the algal species richness has not changed a whole lot from the 1920's to modern day. There were only about 20 new species added to the list. You would think there would have been more since overall lots of new algal species have been added to the roster and the methods for identifying them have gotten better. But no, just a handful of new ones.
Now for the impressive news: On the initial species roster, over 80 of the algal taxa listed were species that had been initially described in countries like England, Scotland, Norway, Denmark, etc. Doesn't that set a flag off in your head? Why would an algal species from frickin' freezing Norway be happy in warm, sunny Bermuda? And aren't all those places REALLY far away from Bermuda? Island Biogeography says that mainland species can come to inhabit islands, but doesn't 3371 mi seem really far, even for Island Biogeography? And this is exactly the sort of thoughts that Dr. Schneider had. So when he and his team looked at the algal species they collected with their modern day keys and microscopes and DNA barcoding rosters, this is exactly the sort of thing they found. These species are not the species they claim to be. So who are they? Where are they more likely to be from? If you answered that they're probably from somewhere closer and warmer, you'd be right! A lot of the species found at Bermuda were in fact from closer places like Jamaica (1253 mi), Mexico, Florida, Georgia, and South America. Over 100 species were re-identified to be different species from these tropical locations. So while the total species richness didn't change a whole lot, the identities of those species changed quite drastically.

In other interesting news, there is the matter of obvious species. An obvious species is one that is big and/or everywhere and you've put any effort at all into sampling, you'll have seen it. Trouble is, this new survey missed some of the really obvious species that the 1920's list indicated were there. And the new list indicates some obvious species the 1920's list didn't find at all....what's going on here? While re-naming things that were previously labeled incorrectly isn't really a shift in community composition, this is! And a shift in composition is something you'd expect after an island has been isolated for a long time. I think this is where that graph from E.O. Wilson comes in handy....

...So the obvious species found in the 1920's had immigrated to the island and have since become extinct. These new obvious species are either new species to Bermuda and/or recent immigrants to the island. Probably some combination of those two...

So we went from a list created by Europeans in the 1920's who identified these tropical algal taxa based on the temperate species they were more familiar with, to a whole new species list comprised of taxa from other tropical mainlands, a changing of the guard of obvious species, and some new ones. Those are some big changes. But if you just looked at richness? Meh...not too much going on. I guess we'll have to leave Dr. Schneider to continue his dreary work in Bermuda, continuing to catalog the algal species composition of that far-off island!

http://www.trincoll.edu/~cschneid/bermuda.html

Craig W. Schneider – An assessment of the island biogeography theory using a century of floristics in Bermuda—immigration and extirpation or simply systematics? 49th Northeast Algal Society Meeting. April 16-18, 2010.

Mutualisms and Aquatic Community Structure: The Enemy of My Enemy Is My Friend

Mark E. Hay, et. al.

Using ample aquatic anecdotes, Hay provides a context for a wide range of species interactions and how predation and competition are not the only interactions that influence community structure. Hay and friends argue that the oft-overlooked positive interactions, such as mutualisms, also play a critical role in community development and structure.

One reason that mutualisms are commonly left out is that many in the scientific community have an oversimplified definition and understanding of a mutualism. Historically, mutualisms have been limited to tightly coevolved beneficial interactions between two species. However, upon more careful examination, mutualisms are much more common and widespread than previously acknowledged. Under the right community and environmental conditions, interactions can shift and those that were previously negative, such as competition and predation, could potentially become mutualistic. This broader view of mutualism includes a multitude of interactions that play a critical role in developing and maintaining community structures and functions.

Communities are often defined by prominent foundation species. These species generally provide the structure and framework of the community by having a relatively larger influence on the community's species composition. Hay provides a few examples of mutualisms between a foundation species and other species that provide some form of benefit back.

Corals form the foundation of the complex coral reef communities along with their photosynthetic zooxanthellae symbionts, without which many coral reef systems would not survive. The zooxanthellae provide carbohydrates to the coral via photosynthesis while the corals provide the zooxanthellae with nitrogenous nutrients. Historically, corals were thought to have coevolved with a specific species of zooxanthellae. However, recent studies have shown that corals can reject and acquire new zooxanthellae symbionts in response to changing environmental conditions. For example, when moved from low-light to high-light conditions, the corals that replaced their zooxanthellae had a lower mortality rate than those that did not acquire new symbionts.

Microbes will often defend their hosts in order to increase survival of both species. One example is of shrimp embryos that are covered by a species of bacteria. The bacteria produces a chemical that protects the shrimp embryos, which act as a growth surface for the bacteria, from a pathogenic fungus. Without the bacteria, the fungus kills the embryos.

Pocilloporid corals commonly harbor a crab and shrimp to act as bodyguards and ward off attackers. The two species will shelter in the corals where they are provided nutrients and are less vulnerable to predation and in return they protect the corals from attack by starfish. The presence of pocilloporid corals protect other corals from starfish attacks despite the fact that they will compete for space and resources - exemplifying the complex interactions that can be involved with mutualisms.

Hay et al conclude the review with a number of examples of interactions that are antagonistic in relation to the two species involved, but become mutualistic when the broader community interactions are considered. For example, interspecific competition is almost always regarded as a negative interaction for both competing species. Congeneric scale-eating cichlids share the same prey resource. However, when two congeneric species of cichlids are present, attack success increased since prey fish could not be as vigilant against multiple attack strategies.

Species Redundancy and Ecosystem Reliability

Naeem’s paper discusses the usage of hypothetical relationships describing ecosystem functions as they provide value to biodiversity. Many of these relationships include species redundancy as a factor. Figure 1 displays charts of these hypothetical relationships, where species redundancy is a factor in any graph where the curve becomes constant for “Ecosystem Function”. The term “redundancy” was originally used to argue that conservation efforts should prioritize species whose contribution to an ecosystem are unique but it has become an argument that conservation of redundant species is unnecessary. Naeem argues that this assessment of redundancy should be reevaluated. “Redundant” species are both necessary and valuable and are a source of reliability in an ecosystem.

Functional groups are used to measure redundancy. A functional group can be defined as a group of species sharing common biogeochemical attributes. Ecosystems can be conceptually divided into compartments: core or peripheral, abiotic or biotic; from which functional groups and redundancy may be determined. Figure 2 provides a representation of these ecosystem compartments. Core biotic compartments include autotrophs and decomposers while core abiotic compartments include nutrients in the form of organic or inorganic matter. Peripheral compartments are either autotroph- or decomposer-derived and may occur at different trophic levels. Links exist between these compartments as shown by arrows in this graphic. Each compartment in this example contains three redundant species.

Naeem further clarifies terms necessary to his argument:

-Local extinction within a functional group is considered a stochastic process.

-Complexity describes the number of functional groups in an ecosystem.

-An ecosystem is said to have failed when it no longer provides the service or goods originally demanded of it. This does not necessitate complete collapse but may be a shift in its function.

-The reliability of an ecosystem (likelihood of failure) is a function of the reliability of its components. As such, more complex ecosystems are more likely to fail.

-While all species are unique, from an ecosystem perspective species are rarely singular in their function. The overall function of an ecosystem will be more significantly altered when changes affect entire functional groups; therefore ecosystems are more sensitive when functional groups are comprised of fewer species.

-Parallel redundancy, or fully compensatory redundancy of a species, can increase the reliability of an ecosystem.

Naeem provides several formulas which model the probability of local extinction of or colonization by a species in a certain functional group, the probability of a functional group providing a service to its ecosystems, and the probability of an ecosystem providing a service given its number of functional groups. Together these show that increasing redundancy increases reliability of an ecosystem, and increasing redundancy is necessary in compensating for the decreased reliability of complex ecosystems. These formulas are however limited in their assumption that extinction and colonization are constant and independent of each other, which is not held in natural processes.

In terms of conservation, it is important to understand that increased rates of global extinction reduces redundancy and diversity of functional groups, and increased fragmentation decreases the recovery effect of colonization. Further research to demonstrate increased compensatory ability with increased redundancy is valuable in showing that a decrease in biodiversity leads to decreased reliability of an ecosystem. The argument can then be made that the maintenance of biodiversity and species redundancy is a requirement for preserving ecosystem services.