A Genetic Comparison of Two Species of Clam Shrimp in the Genus Eulimnadia
The main goal of the authors of the journal article was to address the taxonomic classifications of members of the family Spinicaudata (clam shrimp). According to Weeks and Duff, though bronchiopods (a small phylum of invertebrates) are ubiquitous, they are still widely understudied (295). The authors further stated that the taxonomic classifications of this genus were based solely on morphology which has been proven to be inconsistent, as evidenced by the collapsing of seven known species of Eulimnadia (E. alienata, E.
francesae, E. inflecta, E. thompsoni, E. ventricosa, E. oryzae and E. diversa) into one single morphologically variable species called Eulimnadia diversa. Even after this incident, classification of the members of these species are still based on morphology (classification is based on the more reliant trend of egg morphology over anatomical morphology) and that there are still no interspecific and intergeneric genetic comparisons for members of the Spinicaudata family nor are there studies on reproductive isolation across species.
The findings of this research will represent the first interspecific genetic comparison for Spinicaudata (Weeks and Duff 295). Section II – Hypothesis The research’s main hypothesis is that there are genetic variances between Spinicaudata species that can be used as a basis for the proper and true taxonomic classification of these arthropods. A subtopic to this hypothesis is the assumption that there is a cross species reproductive isolation that will allow for the first evaluation of genetic population structure within Spinicaudata (Weeks and Duff 296).
Section III – Methods The research was conducted in two phases: a) the rearing protocol and data collection phase; and b) the electrophoretic data analysis phase. In the first phase of the experiment, samples of soil with clam shrimp cysts were gathered from six sampling ponds in the state of New Mexico and 3 from the state of Arizona. These samples were raised and cultured in a controlled environment, sexed, and then frozen for electrophoresis.
The second phase of the study involved the usage of electrophoresis wherein the subsequently gathered data were measured for F-Statistics, Nei’s estimate for genetic distance, and Reynolds co-ancestry distance via a software called Genetic Data Analysis package version 1. 0 (Weeks and Duff 296). Section IV – Results and Conclusion Initial classification of the samples gathered through egg morphology revealed seven E. texana populations of and two populations of E. diversa. Upon electrophoresis, it was found that one population of E.
diversa was genetically distinct from the other seven populations of E. texana at six allozyme loci. It was also discovered that after the three F-statistics calculations were performed for the seven E. texana populations, the results were positive, indicating that the population structure was highly inbred and is most likely responsible for the homogenicity of the samples. However, the other population of E. diversa labeled YCOM in the experiment was found to contain alleles from both species and that 20% of the population were of mixed genotype — an indication of hybridization.
Further investigation showed that the progress of hybridization was from E. diversa toward E. texana and not vice versa. Explanations offered behind these phenomena are: a) E. diversa males mated with E. texana hermaphrodites and are made viable due to genetic and behavioral reasons; or b) YCOM was a mixture of male and hemaphrodite E. diversa and hermaphrodite E. texana. The latter is believed to be more likely since it can explain the presence of “pure” E. diversa in the population. These findings point towards two main conclusions: a) E. diversa and E.
texana are genetically distinct at 6 allozyme loci, and b) hybridization is occurring between these two species, possibly proving that there is no reproductive isolation between these two species. This apparent hybridization between the two species have shed doubts on the true distinctions between the two species, opening the thought that the two are probable sub-species and are not true evolutionary-distinct species (Weeks and Duff 297-301). Section V – Personal Opinion It is in my opinion that the authors of the research article were onto something important in terms of brachiopodal studies and in the field of taxonomic classifications.
By bringing into focus the importance of genetic relevance when classifying members of different genuses and families, this can bring about a more orderly classification system that in the future might be useful when the need to track genetic lineage or roots would be of primary importance in specific scientific studies — especially now when we are at the height of genetics research and genome mapping. By giving equal notice to understudied fields in science, we are greatly expanding our available pool of knowledge.
As we all know, the future of science research and scientific progress relies heavily on the foundation of concrete information. Attention to detail has always been a hallmark of true scientific excellence. Thus, by doing this research, Weeks and Duff revived this aspect of scientific pursuit and set a good example to future researchers and scientists as well. Work Cited Weeks, Stephen C. , and R. Joel Duff. “A Genetic Comparison of Two Species of Clam Shrimp in the Genus Eulimnadia: An Electrophoretic Approach. ” Hydrobiologia 486 (2002): 295-302.
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