We present the application of a real-time quantitative PCR assay, previously developed to measure relative telomere length in humans and mice, to two bird species, the zebra finch Taeniopygia guttata and the Alpine swift Apus melba. This technique is based on the PCR amplification of telomeric (TTAGGG) n sequences using specific oligonucleotide primers. Relative telomere length is expressed as the ratio (T/S) of telomere repeat copy number (T) to control single gene copy number (S). This method is particularly useful for comparisons of individuals within species, or where the same individuals are followed longitudinally. We used glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a single control gene. In both species, we validated our PCR measurements of relative telomere length against absolute measurements of telomere length determined by the conventional method of quantifying telomere terminal restriction fragment (TRF) lengths using both the traditional Southern blot analysis (Alpine swifts) and in gel hybridization (zebra finches). As found in humans and mice, telomere lengths in the same sample measured by TRF and PCR were well correlated in both the Alpine swift and the zebra finch.. Hence, this PCR assay for measurement of bird telomeres, which is fast and requires only small amounts of genomic DNA, should open new avenues in the study of environmental factors influencing variation in telomere length, and how this variation translates into variation in cellular and whole organism senescence.

Telomeres often shorten with time, although this varies between tissues, individuals and species, and their length and/or rate of change may reflect fitness and rate of senescence. Measurement of telomeres is increasingly important to ecologists, yet the relative merits of different methods for estimating telomere length are not clear. In particular the extent to which interstitial telomere sequences (ITSs), telomere repeats located away from chromosomes ends, confound estimates of telomere length is unknown. Here we present a method to estimate the extent of ITS within a species and variation among individuals. We estimated the extent of ITS by comparing the amount of label hybridized to in-gel telomere restriction fragments (TRF) before and after the TRFs were denatured. This protocol produced robust and repeatable estimates of the extent of ITS in birds. In five species, the amount of ITS was substantial, ranging from 15% to 40% of total telomeric sequence DNA. In addition, the amount of ITS can vary significantly among individuals within a species. Including ITSs in telomere length calculations always underestimated telomere length because most ITSs are shorter than most telomeres. The magnitude of that error varies with telomere length and is larger for longer telomeres. Estimating telomere length using methods that incorporate ITSs, such as Southern blot TRF and quantitative PCR analyses reduces an investigator's power to detect difference in telomere dynamics between individuals or over time within an individual.

There has recently been much interest in the long-term effects of early growth conditions. Telomeres, the repetitive DNA sequences that cap eukaryotic chromosomes, are potentially a useful tool for studying such effects. Telomeres shorten at each cell division and considerable evidence links the rate at which they do so with cellular and organismal senescence. Previous research has shown that telomere loss is greatest during early life, so conditions during this time could significantly affect telomere attrition, and in this way, possibly also senescence rates. However, relatively little is known about the pattern of telomere loss under natural conditions. We examined telomere dynamics during growth under natural conditions in the lesser black-backed gull Larus fuscus. Although telomere length significantly decreased with age during the chick period, there was a considerable amount of inter-individual variation in both absolute telomere length and the rate of telomere shortening. While no one factor explained a significant amount of this variation, the trends in the data suggested that circumstances during embryonic growth were linked to hatching telomere length. There was a trend for larger hatchlings to have shorter telomere lengths [effect size =À0.18 AE 0.11 kb, 95% confidence interval (CI): À0.40, 0.05], suggesting that embryonic growth rate could have affected telomere attrition. Independent of this trend, males tended to have longer telomeres at hatching than females (effect size = 0.77 AE 0.40 kb, 95% CI: 1.55, À0.02). Egg volume and laying date had no relation to telomere length. There was a strong relationship between telomere length at hatching and at 10 days old (effect size= 0.52 AE 0.22, 95% CI: 0.94, 0.09), demonstrating that the variation in hatching telomere length caused by embryonic growth conditions remained consistent during the initial post-hatching period.

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As part of BioMed Central’s open science mission, we are pleased to announce that two of our journals have integrated with the open data repository Dryad. Authors submitting their research to either BMC Ecology or BMC Evolutionary Biology will now have the opportunity to deposit their data directly into the Dryad archive and will receive a permanent, citable link to their dataset. Although this does not affect any of our current data deposition policies at these journals, we hope to encourage a more widespread adoption of open data sharing in the fields of ecology and evolutionary biology by facilitating this process for our authors. We also take this opportunity to discuss some of the wider issues that may concern researchers when making their data openly available. Although we offer a number of positive examples from different fields of biology, we also recognise that reticence to data sharing still exists, and that change must be driven from within research communities in order to create future science that is fit for purpose in the digital age.This editorial was published jointly in both BMC Ecology and BMC Evolutionary Biology.