The effect of inbreeding on natural selection in a seed-feeding beetle - Article Example

Summary- The effect of inbreeding on natural selection in a seed feeding beetle Inbreeding has a deleterious effect on the population involved, and alters the genotypic as well as the phenotypic stability which results in the loss of fitness of the population as a whole, owing to decreased genetic diversity. In the study, researcher C.W. Fox studied the effect of inbreeding on the selection of egg size in Stator limbatus, a seed-feeding beetle. Directional selection of the egg size favors large eggs which can survive on the seeds of Parkisonia florida because larvas from small eggs are not competent to penetrate the seed coats for survival.

The objective of the study is to understand whether offspring survival related to egg size is affected by inbreeding or not. To conduct the experiment beetle population was collected from Acacia gregii and bred in the laboratory for almost 12 generation before experimentation. Seed pods from both A. greggii and P.florida trees were used to fulfill the seeds requirement in the experiment and the seeds of the individual trees were thoroughly mixed to control seed coat variation among the seeds.

Following the experimental design outbred females were mated with one sibling or non-sibling outbred male beetle after which the female laid their eggs on P.florida to record survival of all the offspring while A.greggii was used for rearing owing to the high rate of larval survival. These first generation adults when emerged from the seeds were used to create a second generation of both inbred and outbred offspring. The beetle pair was put in Petri dishes containing 20 seeds of P.florida and only one larva per seed was allowed to develop inside a chamber controlled at a temperature of 29-30 degrees.

In the experiment, 2-3 eggs were measured per Petri dish using a dissecting scope and finally 460 eggs from females mated to sibling males and 512 eggs from females mated to non-sibling males were collected. To illustrate the relation between the offspring survival and the size of the egg GAM model and linear probability models were used. The conclusive results showed that egg size did not differ much between females that were inbred and out bred; however, inbreeding vastly affected the survival rate.

Eggs resulting from outbreeding survived more than those that were inbred. The values for egg to adult survival 0.66 in case of outbred offspring but a reduction of about 29.5% was seen in case of inbred ones. Linear probability model revealed that larva from larger eggs survived more than those emerging from smaller ones.It was evident from the logistic regression values that inbreeding among the beetle population lowered the fitness but had no effect on the relation between egg size and fitness.

Though the experimental set up eliminates selection factors that normally occur in nature, the researcher expects that there will be a similarity in the inbreeding treatment pattern between that of nature and laboratory.REFERENCES:Fox, C. W. "The effect of inbreeding on natural selection in a seed-feeding beetle." Journal of Evolution Biology 26 (2012): 88-93. Web.