[Return to Essay List]

Differential Dispersal of Introduced Species
as a Model for Punctuated Equilibrium Dispersal

 (Return to Top)

Introduction

One of the problems that creationists seem to have with evolution is how new species can rapidly disburse and sometimes displace existing species. This is especially true for the punctuated equilibrium ("punk eek") model of Gould and Eldridge and the problem of the "sudden appearance" of fossils in the geological record.

This essay is written to discuss the dispersal aspects of small populations into a new environment, removing the issue of new species evolution from the discussion, and looking instead at how fast a species can disperse under certain circumstances.

Bird species introduced into North America, both intentionally and accidentally, have shown different levels of dispersal across the continent. In some cases we know that they had only small initial populations located in one place, the point of release. We also know that they were not here before being introduced. Birds are also much studied and tracked by amateur as well as scientific groups, so their behavior habitat and range are well known. Thus such species are good models for how new species disperse into a new environment.

(Return to Top)

(1) European House Sparrow


http://www.rainieraudubon.org/bib/nestbox/sparrow-starling-info.htm
A homesick Englishman by the name of Nicholas Pike brought with him 50 House Sparrows from England and released them in Brooklyn, New York. Those 50 sparrows quickly adapted to the American lifestyle, driving out birds that had been native here. Today, House Sparrows are one of the most common birds in the World, having been introduced virtually everywhere.
These birds are considered destructive and dangerous to indigenous species.
http://www.americanartifacts.com/smma/per/spar1.htm
Although resembling our native sparrows, the English sparrow is actually a weaver finch, and now has its own family, the Passeridae. It was first imported to the United States in 1850, and, by 1887, some states had already seen fit to launch sparrow eradication programs.
From only 50 sparrows to continent wide in less than 150 years (maximum - probably more like 50 years).

(Return to Top)

(2) European Starling


http://www.rainieraudubon.org/bib/nestbox/sparrow-starling-info.htm
In the early 1890's, the Acclimation Society of North America released 50 pairs of Starlings into New York's Central Park as part of a project to introduce every bird ever mentioned in a Shakespeare play. Only 50 years later their populations had spread across the continent, competing for nesting sites with our native birds.
From only 50 starlings to continent wide in less than 50 years

(Return to Top)

(3) English Skylark


http://www.americanartifacts.com/smma/per/spar1.htm
John Gorgas, of Wilmington, Delaware, writes: "I imported last year from Liverpool two lots of skylarks, both of which arrived safely and in good health. The first lot, twenty in number, arrived on the 20th of February, (1853), and were kept confined until the 19th of March, when they were liberated. The other lot, 22 in number, arrived on the 18th of April and were set free the next day.
(italics in original)

Those skylarks did not survive. Others introduced to Vancouver Island (BC, Canada) in the 1900's have established a resident population on the island.

(Return to Top)

(4) Crested Myna


http://www.vancourier.com/101102/news/101102nn1.html
The crested myna first lighted on the shores of Vancouver sometime in the 1890s. Exactly how or when isn't known. ... By the 1920s, flocks could be found throughout Vancouver as well as in New Westminster, Richmond, Ladner and in Victoria, Nanaimo and Courtenay on Vancouver Island.

Although some have suggested that the population rose to about 20,000 crested mynas, bird experts believe they numbered around 6,000 to 7,000 at their peak.

Now getting down to the point where sightings are rare and they are expected to die out soon -- the last count only found two birds. One of the reasons for the decline is competition with the European Starlings: the decline started in the 1930's and that was about when the Starlings showed up.

(Return to Top)

(5) Chukar


http://iron-horse.us/chukar/alectoris_chukar_academy.shtml
Chukars have been successfully introduced as a game species into western North America, the Hawaiian Islands, England and New Zealand.

Chukar were introduced into North America during the 1930's and have established populations in all of the western states and into Canada. Historically, Nevada, Oregon and Idaho have been the top producing states. Huntable populations also exist in northeastern California and the Mojave Desert, eastern Washington, Utah, Colorado, Wyoming, Montana (primarily in Carbon County) and south central British Columbia. Arizona has a relatively small chukar population in the extreme northern portion of the state and small populations of uncertain status have been reported from New Mexico, western South Dakota, and southern Alberta

Numbers and range expanding in spite of being hunted.

(Return to Top)

(6) Budgerigar


http://www.wildflorida.org/bba/budg.htm
Native to Australia, the Budgerigar has been present in the St. Petersburg area since at least 1940 (Stevenson and Anderson 1994). By the mid-1960s, it was established in much of Pinellas County. Originally the population was comprised of escaped birds, but later augmented by deliberate introductions the birds were considered a tourist attraction (Owre 1973)! Budgerigars eventually became established along the Gulf coast from southern Hernando County to Sarasota County with the largest numbers in Pasco and Pinellas counties. As of 1995-96, Budgerigars appear to be virtually extirpated from Pinellas, Manatee, and Sarasota counties, with perhaps 100 birds each in southwest Hernando and northwest Pasco counties (B. Pranty, pers. obs.).

Formerly, Budgerigars were much more numerous and had a larger range along the Gulf Coast, but they suffered large-scale reductions in the early 1980s, apparently from the severe freezes that Florida experienced during this period. Competition with European Starlings over nesting sites may also have been a factor (D. Goodwin, pers. commun.), as well as disease or epidemic (W. Biggs, pers. commun.)

Budgerigars are sociable birds and congregate in large flocks. During the winter, they are often seen flocking with European Starlings. In 1978 Wenner and Hirth (1984) counted 6,000 to 8,000 Budgerigars in 1 roost in Pasco County. Comparable flocks have not been seen since the early 1980s, and the species may become extirpated from Florida within the next decade.

Peaked and now in decline.

(Return to Top)

(7) Rose-ringed Parakeets


http://natureali.org/roseringed_news.htm
About 187 rose-ringed parakeets have been confirmed in Bakersfield. They are naturalized, meaning they have been introduced to the area and have bred successfully.

"The population here is quite large," said Ted Weinheimer, a CSUB biology professor who said he is interested in how the parakeets interact with other species and whether they create competition.

The earliest confirmed report is a male who escaped from a cage in northeast Bakersfield 20 years ago. Sheehey said the parakeets are quite smart and escape easily.

Sheehey said her research shows 31 of the birds have been documented in Miami and 64 have been documented in Los Angeles. There are also some in London, she said.

The birds are found natively in Africa, West Africa and India, among other places.

Established in 3 different locations and apparently growing in one of them.

(Return to Top)

Conclusion

Thus we see two extremely successful dispersions and others of limited success and finally some that succeeded only to lose out to later competition. Obviously not all introductions are successful, and just as obviously not all newly evolved species will win out in similar circumstances.

Native species are being impacted by the "successful" introductions (Starlings and House Sparrows) but they are still viable at this time (probably most impacted is the Eastern Bluebird, although there are other stresses on this bird as well). There was no eco-niche vacuum for the newcomers to fill and there was competition, but they have been able to disperse across the continent.

Once a new species has evolved it could disperse in much the same way, and if they evolved in isolation in a small area or an area that didn’t make fossils then there would be no record of any transitions. Thus any one of these would have appeared "suddenly" and "without any transitions" in the fossil record under these circumstances, particularly as 50 years is the blink of an eye in historical time, to say nothing of geological time.

Enjoy.

(Return to Top)

(Note: this is an essay and as such represents the opinions of the author. You can e-mail comments to me at RAZD8@yahoo.com)

[Return to Essay List]

we are limited in our ability to understand
.... by our ability to understand
Rebel A American . Zen [ Deist
... to learn ... to think ... to live ... to laugh ...