Plethadon is a genus inclusive of the salamander family.
As a genus,it has a high rate of inter species genetic variability, The C value which is a measure of genetic variation in species is very high especially in this genus.
Low rate of mutation, climatic niche and low rate of DNA loss etc are some of the various factors.
p.larselli and p.richamondi has a difference in genome size and this difference can be attributed to the presence of more DNA segments
that are none coding in larselli compares to that of richamondi.
The DNA fragments that does not code for protein are the non coding sequence but they have some other revolutionary and evolutionary functions.
Some of these sites that doesn't code can be small repeating sequence, microsatellites and variable number tandem repeats etc and these shows high chances that richamondi have lost some of these sequence that are non coding from it's chromosome as part of a genetic or epigenetic changes during the course of evolution or there might be also a high rate of mutations among them leading them to loose some DNA fragments.