Abstract
Determining both individual age and population age distribution is
crucial for an array of ecological studies. This is generating growing
interest in molecular age markers such as telomere length. Most studies
exploring the relationship between age and telomere length have been
cross-sectional, but such studies face problems with large individual
variation and the selective loss paradox. Thus, interest is growing
rapidly for turning to longitudinal studies. In this study, the rate of
telomere loss was analyzed for the extraordinarily long-lived North
Island brown kiwi, Apteryx mantelli. Relative telomere length (RTL) was
quantified using qPCR from blood from four separate sampling occasions
across 14 years were analysed. Uniquely, the analysis of RTL was
combined with high resolution analysis of genomic quality to get
numerical values of DNA integrity. The analysis of RTL suggested a circa
5 % annual increase in A. mantelli telomere length. However, RTL was
found to be highly correlative with DNA integrity, indicating that the
perceived elongation of telomeres was a result of DNA quality
differences between cohorts. Notably, the observed, positive correlation
remained significant even when analyzing only samples classified as
being of high DNA quality. Previous work has highlighted the potential
impact of sample storage differences on RTL. However, to our knowledge,
this is the first study to suggest that even small differences in DNA
integrity between samples cohorts can impact the results of telomere
studies. These findings are of great importance since longitudinal
telomere studies of long-lived species tend to be “after the fact”
utilizing already available samples for which handling and/or storage
regimes might differ or be unknown. For such studies, we suggest that
analysis of DNA quality with higher precision than traditional gel
electrophoresis is needed to generate reliable results of telomere
dynamics.