Genetic variability and telomeres: Insights from a tropical avian hybrid zone

Telomere lengths and telomere dynamics can correlate with lifespan,
behavior, and individual quality. Such relationships have spurred interest
in understanding variation in telomere lengths and their dynamics within
and between populations. Many studies have identified how environmental
processes can influence telomere dynamics, but the role of genetic
variation is much less well characterized. To provide a novel perspective
on how telomeric variation relates to genetic variability, we
longitudinally sampled individuals across a narrow hybrid zone (n = 127
samples), wherein two Manacus species characterized by contrasting
genome-wide heterozygosity interbreed. We measured individual (n = 66) and
population (n = 3) differences in genome-wide heterozygosity and, among
hybrids, amount of genetic admixture using RADseq-generated SNPs. We
tested for population differences in telomere lengths and telomere
dynamics. We then examined how telomere lengths and telomere dynamics
covaried with genome-wide heterozygosity within populations. Hybrid
individuals exhibited longer telomeres, on average, than individuals
sampled in the adjacent parental populations. No population differences in
telomere dynamics were observed. Within the parental population
characterized by relatively low heterozygosity, higher genome-wide
heterozygosity was associated with shorter telomeres and higher rates of
telomere shortening – a pattern that was less apparent in the other
populations. All of these relationships were independent of sex, despite
the contrasting life histories of male and female manakins.  Our
study highlights how population comparisons can reveal interrelationships
between genetic variation and telomeres, and how naturally occurring
hybridization and genome-wide heterozygosity can relate to telomere
lengths and telomere dynamics.