Introduction
The article provides a comprehensive report of research carried out in the Lake Malawi region in Malawi, Africa. The study was carried out between 2013 and 2014, and the article was published in March 2014. The aim was to investigate the evolution of animals around the lake, specifically examining the change of body shapes in populations of cichlids that lives on rocks near the lake (1). Thus, the research was carried under the knowledge that animals around the lake were experiencing an evolution in order to adapt to certain environmental conditions in the region. The article provides a report of the background, problem, methodology, results, and conclusions of the study. This paper attempts to develop a comprehensive review of the article in order to examine its worthiness in expanding or contributing to the expansion of the existing knowledge in evolutional biology.
Study problem
The study aimed at examining the existence of this phenomenon in mbuna cichlids.
Study hypothesis
In light of the ecological theory noted in this study, the researchers hypothesized that slight but significant ecological differences have occurred alongside sexual signals, and a correlation exists between the divergence of sexual traits and the divergence of ecological traits (3).
Study question
The study attempts to answer the following questions from an empirical perspective.
- Are there significant ecological differences accompanying sexual signals in Lake Malawi cichlids? (1)
- Is there a significant correlation between the divergence of sexual traits and divergence of ecological traits in Lake Malawi cichlids? (1)
Significance of the study
The researchers aimed at contributing to the growing body of knowledge in the evolution of animals inhabiting the same ecosystem. Modern studies are attempting to examine the impact and progress of evolution in living things (4). Among the less studied living things are the animals and plants living in isolation and in areas that are hard to reach. The Mbuna cichlids of Lake Malawi are an example of such animals, considering that few studies have been carried out on the living things in the lake (1). In addition, the study uses modern technologies in molecular biology, specifically DNA technologies such as Amplified Fragment Length Polymorphism (AFLP), to examine the progress of evolution from a molecular perspective, a very important and reliable method (5).
Methodology
The researchers used an empirical approach to the problem under study. A study is a quantitative approach that attempts to examine the evolution of the body shapes in populations of Maylandia zebra, a species within the cichlid groups in Lake Malawi. In addition, they examined a population of several non-barred congeners inhabiting the same region. They examined differences in mitochondrial DNA, which is one of the most important molecular aspects in animal cells that portray even the slightest change due to evolution and mutations (6). Mitochondrial DNA is increasingly being used to examine evolutionary changes in populations of living things within the same species or genus due to its ability to show evidence of small and recent changes in response to evolutional factors (7).
Samples of mitochondrial DNA were obtained from the cells in the cranial and jaw regions of the sample population. The cells were obtained from the same region across all the animals under study. In addition, the procedures used in isolation and treatment of the mitochondrial DNA were uniform for all the animals and cells.
The researchers used PCR-based AFLP technology to amplify DNA fragments obtained from the cells. The primers used were developed based on the prior knowledge of some of the regions of the Mitochondrial DNA in these cells (8). The amplification process produced a significant amount of DNA fragments. The AFLP technology was then applied to determine the differences in the DNA fragments across all the animals based on their sizes. It was based on the knowledge that different regions of mitochondrial DNA have different seizes due to mutations and evolution and will form different bands based on their sizes (9). Significant changes in similar regions from cells obtained from similar structures are likely to indicate that evolution has occurred, thus affecting the observed phenotypic differences between the sample populations (10).
Results
Phenotypic examination indicated that the barred populations of the animals differ in terms of their boy shapes from the congeners that are not barred. In addition, the researchers found that there were differences in the direction of the body shapes, which were maintained across all the barred and non-barred animals (1). Moreover, phenotypic examinations revealed that the population of the barred animals had deeper bodied structures, which was expected to be an adaptation to the habitat they prefer (rocks). On the other hand, the examination revealed that the bodies of the non-barred population were “fusiform” (1).
The empirical study with molecular DNA technologies RFLP revealed that the non-barred populations of the Lake Malawi cichlids are not monophyletic. Thus, these were an indication that there were multiple evolution events but were independent of the other population. The sizes of the DNA fragments from the same regions in the sample populations were differing, as indicated by the sizes of the RFLPs on the gel electrophoresis (1).
Conclusion
The researchers analyzed the mitochondrial DNA results obtained from the RFLPs in the study. They concluded that the evolution of coloration, as well as body shape in the animals, might have resulted from evolution. They confirmed the hypothesis that significant ecological differences have occurred alongside sexual signals, and a correlation exists between the divergence of sexual traits and the divergence of ecological traits (2).
Evaluation
The article is an important source of information for academic as well as scientific purposes. It is also important for Malawi’s tourism sector because it is likely to motivate more scientists to study the animals and plants in the lake, thus contributing to the region’s scientific tourism (1).
Bibliography
Husemann M, Tobler, McCauley C, Ding B, Danley PD. Evolution of body shape in differently colored sympatric congeners and allopathic populations of Lake Malawi’s rock-dwelling cichlids. Journal of Evolutionary Biology, 2014; 27(5): 826–839.
Zeddam J, Léry X, Gómez-Bonilla Y, Espinel-Correal C, Páez D. Responses of different geographic populations of two potato tuber moth species to genetic variants of Phthorimaea operculella granulovirus. Journal of Evolutionary Biology, 2013; 19(3): 126–139.
Crespo-Pérez V, Dangles O, Régnière J, Chuine I. Modeling temperature-dependent survival with small datasets: insights from tropical mountain agricultural pests. Bulletin of Entomological Research, 2013; 103(03): 336-343.
Dangles O, Herrera M, Mazoyer C, Silvain J. Temperature-dependent shifts in herbivore performance and interactions drive nonlinear changes in crop damages. Global Change Biology, 2013; 19(4): 1056-1063.
Blanford J, Blanford S, Crane RG, Mann ME, Paaijmans KP. Implications of temperature variation for malaria parasite development across Africa. Scientific Reports, 2013; 3(2): 219-223.
Dangles O, Herrera M, Anthelme F. Experimental support of the stress-gradient hypothesis in herbivore-herbivore interactions. New Phytologist, 2013; 197(2): 405-408.
Horgan FG, Quiring DT, ALagnaoui A, Pelletier Y. Life Histories and Fitness of Two Tuber Moth Species Feeding on Native Andean Potatoes. Neotropical Entomology, 2012; 41(4): 333-340.
Espinel-Correal C, López-Ferber M, Zeddam J, Villamizar L, Gómez J. Experimental mixtures of Phthorimaea operculella granulovirus isolates provide high biological efficacy on both Phthorimaea operculella and Tecia solanivora (Lepidoptera: Gelechiidae). Journal of Invertebrate Pathology, 2011; 110(3): 375-381.
Wilson RJ, Maclean IMD. Recent evidence for the climate change threat to Lepidoptera and other insects. Journal of Insect Conservati, 2012; 23(3): 346-354.
De Meester L, Van Doorslaer W, Geerts A, Orsini L, Stoks R. Thermal Genetic Adaptation in the Water Flea Daphnia and its Impact: An Evolving Metacommunity Approach. Integrative and Comparative Biology, 2011; 121(2): 239-248.