Experimental Zoogeography of Islands: Defauantion and Monitoring Techniques by Wilson and Simberloff, 1969

This paper provided an extensive account of the methodology used by Wilson and Simberloff, to remove fauna on small islands. The purpose was to develop an effective technique of defaunation that would allow experimentation of colonization and provide data to test the hypotheses of MacArthur and Wilson (1963 and 1967). These hypotheses make suggestions on the equilibrium number of species on an island and the predicted survival times of recolonization, but are limited in what they can explain and the data to support them were scarce (at least at the time). Empirical evidence was needed to further explore these ideas.

The authors decided that in order to accurately determine appropriate methods for defaunation of small island a few criteria were needed:

1. There needed to be enough islands for replication and variation.
2. There needed to be sufficiently large animal diversity and organisms that were large enough to accurately find and identify.
3. Small island size was needed to compensate for the close distance they were to the mainland source.

Small islands along the Overseas Highway of southern Florida fit all of the study criteria. A total of nine islands of varying size (11-25m diameter) and distance from the mainland source (2-1188m) were censused (25-43 initial numbers of arthropod species on each island). Island flora consisted of mangrove trees and fauna consisted of arthropods, mostly arboreal, with about 75 species of insects, about 15 species of spiders and various other arthropod species. A few vertebrates including birds, snakes and raccoons were also found but were not included in the census as these were usually on the island to forage and were not considered inhabitants.

Of the nine islands censused, two were controls and not subjected to defaunation, one was an island used to test defaunation method and six were experimental islands were defaunation was performed. Five islands censused (four experimental, one control) were located in Great White Heron National Wildlife Refuge and three islands (two experimental, one control) were located in the Everglades National Park.

Two methods of defaunation were tested to determine overall effectiveness. The first attempt used a spray application of parathion and diazinon (insecticides). However, it was found that the spray couldn’t penetrate hollow twigs and although it did kill many arthropods species, it did not completely defaunate the island.

The second attempt was to use a fumigation method to remove arthropods from the island. Field and lab tests were conducted on mainland Florida to test four insoluble fumigants. Of the four tested, methyl bromide was found to have the lowest impact on plants and was the most effective at killing arthropods, including eggs and pupae of the more resilient species. Fumigation was conducted on two experimental islands, however heat damage occurred to the plants during the daytime fumigations and all other islands were fumigated at night.

Once the chemical and application technique was determined the next experimental issue was how to construct a fumigation tent without damaging the trees. The first tent constructed was supported by a temporary full frame that was constructed at the island site and used to raise the tent. Methyl bromide was introduced through the tent wall and an electric fan was used to disperse the gas. After fumigation, the gas was released through a seam in the tent for 45 minutes and the tent was removed. Although a success, the few live insects that were found in the six man hours spend exploring the island resulted in an increased concentration of methyl bromide on all subsequent islands.

Due to the difficulty in erecting scaffolding framework to hold the tent at islands of farther distance from a land source, a new method was devised. A tower was created at the island center and used to support most of the tent weight. This proved to be easier to construct on islands farther out, but was also more vulnerable to wind.

All islands were fumigated under a tent and examined after tent removal. Of the six experimental islands, there were no live insects on four, one live beetle on one island and one live millipede on another island. The authors concluded that their fumigation technique was efficient at removing all arthropods species, with the possible exception of deep boring species.

During monitoring, care was taken not to contaminate islands and also to prevent destruction of possible habitats. Dead insects were collected after fumigation to determine species composition on the island before defaunation. Species census was taken for two days, every 18 days after defaunation. Discovery of new species was very high until about 14 man hours post defaunation, at which point the new species discovery declined to near zero. Variation in island size and distance, and weather conditions were found to cause minor differences in the times in which species were discovered, however the cumulative species count curves were very similar in shape for the three islands that were plotted in species accumulation graphs.

This paper presents an interesting account of the author’s persistent attempts to refine and perfect their methodology of small island defaunation. Although I appreciate their perseverance and thorough account of their trials and errors, I wonder if all of their “failures” would be published in present-day articles, or if only the successful methods and subsequent results would be publishable and thus not needing a separate methods paper?

Pollinators in Harlem

Hey, this sounds familiar!

Singleton 2010

Barred Owl Space Use and Habitat Selection in the Eastern Cascades, Washington

Barred owls (Strix varia varia) compete with spotted owls (Strix occidentalis caurina). The range of barred owls is expanding from the deciduous forests of eastern North America to the coniferous forests of western north America. Now the ranges of barred owls and spotted owls largely overlap. Spotted owl populations are declining, particularly where barred owl populations are most abundant. The effects of expanding ranges of barred owls on spotted owls includes: consumptive competition, displacement, and hybridization. Other major threats to the spotted owls include habitat loss, infestations of defoliating insects, and forest management practices.

The objective of this study was to obtain more information about barred owl ecology to inform management practices. The authors looked at space use patterns of barred owls, factors that determined habitat selection by barred owls, and the relationship between these factors and the probability of habitat use by the owls.

The study area was a mixed conifer vegetation zone in Chelan County WA. The site was chosen because it encompassed a range of environmental conditions. The birds were located using recorded calls. The birds were then captured and fitted with radio tracking devices. Spatial data was obtained using GIS.

The findings of this study were consistent with findings of previous studies. Barred owl habitat is moist, structurally diverse, closed canopy forests on gentile slopes. Habitat use was most strongly associated with highly productive moist forest. In contrast, spotted owls prefer dry forest habitats. The differences in ecology may be related to prey types.

Forest managers may use this information to protect areas of forest where spotted owls are most likely to be found and where barred owls are least likely to exclude them.

Fleischner 2005

This article was a nice change from the traditional rigid and emotionless articles that we are usually immersed in. Written in poetic prose, Fleischner begins by recounting a life changing experience that he had in Alaska. He was hired by the National Marine Fisheries Services to find out the basic natural history of bowhead whales.

Natural history seems so basic and simple, yet it is fundamental if we want to learn anything about life on earth. Natural history is studying life at the level of the individual and how it interacts with its’ environment. It asks who, what, where, when, and how?

Although natural history has been around since civilization, it has gone in and out of fashion. As science advances, studies have become increasingly experimental and theoretical. Many people perceive ecology as mostly descriptive and an archaic form of science. These people are forgetting that theories mean nothing if they are not based on sound natural history.

Breakthroughs in our understanding of biology have been made by individuals who spent painstaking hours just observing. Darwin and Wallace both completely engrossed themselves in their systems before they had their revelations. Barbara McClintock discovered transposable elements by staring at corn squashes endlessly. She said that she felt like she was physically in there with the transposable elements.

For conservation biologists, knowing the natural history of at risk organisms is essential to making management decisions. You need to know where and how many individuals there are. This year is a census year in our country. The census is a kind of natural history survey of people. Policy makers need to know how the population is distributed in order to find what communities are most in need.

The best source of reliable natural history information is indigenous people. Their knowledge is local and reliable because they are one with their surroundings. Their survival depends on it. Their level of being in tuned with their surroundings is something most people never ascertain.

There have been moments in the field when I felt like I was completely in touch with my surroundings. I felt so small and insignificant. Those were some of the most primal and euphoric moments in my life so far. We need to return to natural history. We need to return to loving the earth.

For all you NPR Wh… um… Junkies

Did anyone else have NPR on in the background while working on their Community Ecology papers this weekend? In case you didn’t, Wait Wait Don’t Tell Me (the oddly informative news quiz) had two community ecology related segments this weekend. Not quite peer review caliber, but worth a listen. I’m not great with figuring out how stable links are, but you should be able to hear the show (on the internet or via podcast) and/or see the transcripts from the show’s website www.npr.org/programs/waitwait .

The first community ecology-ish bit was in the Bluff the Listener segment, where Adam Felber recounts a story of a mega-mall which has evolved its own “…weather, indigenous plant life, and at least two unique species of poison resistant, highly aggressive rats.” It is also quoted as having “become a sort of retail Galapagos.” The other community eco-ish bit was towards the end of the Panel Round Two segment, where host Peter Sagal quotes a Pentagon study that a decline in science education in the country has lead to fewer “nerds” being produced. Sagal then spins a yarn that “High school is just like any other complex ecosystem, it balances out. Without nerds to stuff into lockers, jocks will have to feed on the burnouts, allowing the marijuana crops to flourish and multiply, which in turn leads to stoned cheerleaders. Then, the jocks, with no one to cheer for them, begin to die out, freeing nerds to rise again.”

And if all of this is not enough reason to listen to this week’s show, the Not my Job guests were two members of the band (and cultural icon) The Village People!

Diadromous fish and “eco-social anomie”

Here is a link to a brief article I received earlier today. Although not heavy on the community ecology end, it offers some interesting insight on species conservation.

Enjoy

http://e360.yale.edu/content/feature.msp?id=2258