Few Continuous data irregularly dispersed over geographic range

Hi everyone
I have e little dataset of biological data (concentrations) collected over a geographic range of 1000 km grouped in 4 spots (ca. 100 km each).
Given the tiny sample (2*25 samples corresponding to two different time periods), I thought about Bayesian methods and a MCMC approach in order to compare potential geographic clines between the two periods.
My question is rather simple : is it possible and if yes, how could I do that in R please ?
Many thanks to all the folks that could give me some help !