BIOL 215 Lecture Notes - Lecture 11: Aposematism, Coevolution, Herbivore

In a small paragraph, compare and summarize these two articles.

Article 1 Description

This article is an observational study, which discusses how frequency dependent selection affects two phenotypes of a predator through differential guarding response. The researcher examines the ratio of handedness of two samples of P. microlepis collected from two adjacent sites along Lake Tanganyika’s northwestern shoreline for a period of eleven years. The process of observations includes observing the correspondence between the handedness of P. microlepis and their targeted prey (Hori, 1993). The researcher carried observations to identify the direction from which P. microlepis attacked the flank of their prey. Moreover, the researcher used a gill net to catch each P. microlepis that attacked the lure. Catching the P. microbes made it possible for the researcher to observe its features and determine its handedness. The researcher determined the handedness of the scales of P. microlepis by observing the fish under a microscope.

During the period of study, Hori (1993) established that the ratio of handedness of P. microbes remained at 0.5 for each one-to-two year intervals throughout the eleven years of the study. Further investigations on temporal changes in handedness ratio showed that the ratio oscillated with amplitude of 0.15 within a five-year period (Hori, 1993). These observations were made for the two species of P. microlepis under investigation. The researcher concludes that the direction of mouth opening of scale eating cichlid fish in Lake Tanganyika is determined by the genetics of the fish. The researcher demonstrates that frequency-dependent natural selection determines the number of left-handedness or right-handedness fish. Based on researcher’s observations, when right-handed fish attack from behind, they snatch the scales from their prey from the left flank (Hori, 1993). On the other hand, when left-handed fish attack their prey from behind, they attack the right flank (Hori, 1993). Therefore, fish with rare phenotypes are more successful as predators than ones that have the more predominant phenotype. This study can be used to guide researchers who are interested in seeking ways of increasing the population of different species of fish. It can also be used as a basis for investigations on how fish type determines its survival tactics or predator tactics.

Article 2 Description

The study was an experimental analysis which sought to quantify phosphoglucose isomerase (Pgi) frequency change over a period of time and compare Pgi genotypes based on physiological responses to high temperatures and subzero thermal extremes encountered by beetles in nature. The research seeks to establish how the local climate in Bishop relates to changes in allele frequency at Pgi and other allozyme loci. It also seeks to establish if ambient temperature of beetle habitants rise to levels that expose beetles to stressful temperature. The researcher also seeks to establish how Pgi genotypes differ physiologically when exposed to subzero temperatures. By answering these questions, the researcher will establish the relationship between changes in enzyme genotype frequency and regional climate changes in addition to investigating major physiological mechanisms through which animals respond to change in climate.

To answer research questions and test research hypothesis, the researchers carried out several experiments and analyses of data. The experimental study involved collecting adult beetles that had emergent recently from pupae for a period of one year between August 1988 and August 1989 (Rank & Dahlhoff, 2002). Their genotype was determined at five different polymorphic enzyme loci. Some of the things analyzed during the study include fluctuations in climate and allele frequency change; daily and annual mean values of air temperature, Effects of Pgi genotype on HSP70 expression, and quantification of Pgi genotype on HSP70 expression among other things (Rank & Dahlhoff, 2002). The study results revealed that although beetle populations were genetically different the FST-values for 1996 were greater for each enzyme locus than those for 1998 (Rank & Dahlhoff, 2002). Moreover, researchers established that the frequency of Pgi allele had increased by 11 percent, a trend that was not observed for all the other loci investigated. Therefore, the researchers conclude that Pgi genotype differences in thermal physiology account for Pgi allele frequency change in nature. Contrary to selected hypothesis that the frequency of Pgi allele should increase with decrease in temperature, the study established that the frequency of Pgi allele decrease with decrease in temperature. This work is important because it provides a basis for more research on how variations in temperature affect beetle populations. The study findings can be used to guide researchers who are interested in seeking ways of protecting endangered beetle populations in different climatic conditions.