Inbreeding Bumblebees and Declining Populations

By: Katelyn Lutes

September 23, 2010.

ENVS*1020*0140

The world is composed of many intricate systems working simultaneously together as one large system. Within these systems, species and organisms operate together, dependant on one another for food, reproduction and habitat. The threat of elimination of any one species can therefore have a significant impact on various plants, animals and individuals that are strongly or less significantly linked to it. The article British Bumblebees are Inbreeding Themselves to Extinction by John Plat (Scientific American) is focused on the endangerment of several species of bumblebees due to lack of genetic diversity, caused by inbreeding. Inbreeding is the mating of organisms that are of the same genetic decent. This occurs in small, isolated populations. The reasearch formatted in the article was developed from a scientific journal written by Penelope Whitehorn (BMC Evolutionary Biology, BioMed Central), titled Impacts of Inbreeding on Bumblebee Colony Fitness Under Field Conditions. Bumblebees play a vital role in the pollination of plants. The removal of these species from their British ecosystem will have a strong ripple effect on plant-life and surrounding herbivores and carnivores. The threat of extinction of bumblebees is an environmental issue.

The primary source of information, described experiments that were conducted on three populations of the bumblebee species Bombus terrestris. A picture of the species can be seen to the left of the text. One population was outbred, meaning that the queen of that colony was not produced by inbreeding. The other two populations were inbred, one producing males that have two sets of chromosomes (normal males will have only one copy of each chromosome), and the other inbred population producing normal males. Experiments were conducted on the three colonies. These experiments tested the success of the population in hibernation survival, colony foundation, colony growth amount and rate, and survival and growth in the field ecosystem. The secondary source of the information causes the reader to believe that all inbred populations of bumblebees are endangered. The research concludes that only colony that had significantly negative survival and growth in the field was the inbred population producing males with two sets of chromosomes. Plant's article fails to mention anything regarding the genetics of males, and is therefore misleading to the reader. Inbred colonies producing normal males were just as successful as outbred colonies.

The primary source was also principally concerned with male bees with two sets of chromosomes, and how it causes them to be sterile. This decreases the effective population size of the species. The secondary source mentioned only one sentance regarding the infertility. the primary article was also mostly focused on the bumblebee species Bombus terrestris. The secondary article refrences a species called Bombus moscorum, which was not included in the origanal journal at all. The article written by John Plat vaguely mentions potential risks that may occur because of bumblebee inbreeding, such as increased susceptibility to gut parasites. This differs from the primary source, as the scientific journal does not mention this fact.

Whitehorn's scientific journal (the primary source) also mentions that the experiments conducted are very dependent on small populations. Small populations are more susceptible to less genetic variability, which is a main cause of producing males with two chromosomes. The experiments were contained to isolated populations, and may represent what many, many years of genetic drift may produce. Whitehorn also states in the scientific journal that loss of habitat is strongly linked with declining populations of bumblebees. The title of the secondary source (British Bumblebees are Inbreeding Themselves into Extinction) causes the reader to get falsified information before the article is read. The truth is that some small, isolated populations of bumblebees have declining populations because of double-chromosome males, produced from inbreeding.

The secondary article was not an accurate portrayal of the information in the primary report. Several examples show that the information presented in the article is not completly accurate with the experimental results in the journal report. Since the author failed to mention the several details about the experiments, the reader gets the impression that all bumblebee species are endangered solely because of inbreeding. The species is endangered as a result of environmental and biological issues, and only partially because of inbreeding. The two written works differ considerable because of their intended audiences. The article is intended for a public audience, and the journal is for other professionals in the scientific field. Thus, scientific details are not essential to the main body of work in the article. However, the author did not present significant information about the main idea of the primary source.

Plat, John; Scientific American. "British Bumblebees are Inbreeding Themselves into Extinction". Extinction Countdown. September 13 2010. http://www.scientificamerican.com/blog/post.cfm?id=british-bumblebees-are-inbreeding-t-2010-09-13

Whitehorn, Penelope, R; BioMed Central. "Impacts of Inbreeding on Bumblebee Colony Fitness Under Field Conditions". BMC Evolutionary Biology. July 2, 2009. http://www.biomedcentral.com/content/pdf/1471-2148-9-152.pdf