Abstract
Ageing refers to the loss of organismal functionality with age, a process that is characterised by decreased reproduction and survival probability. In natural populations, it is expected that environmental conditions influence an individual's ageing trajectory. Understanding the role of environmental heterogeneity on ageing variation could provide critical insights into population resilience and species distribution but remains overlooked. Telomeres, the end cap of chromosomes, are a promising integrative physiological marker of an individual's health and a possible proxy to aid the understanding of variation in ageing trajectories. Here, we review the existing information on telomere length and its dynamics in wild populations distributed across spatial scales. Despite a relative scarcity of information, there is evidence for divergence in telomere length between populations facing contrasting environments. Nonetheless, a higher spatial resolution and temporal replication are needed to fully understand the role that environmental conditions play on telomere length variation. Since most of the existing studies are correlational, future field and laboratory experiments are required. For the first time, we demonstrate the use of population telomere data to predict species habitat suitability through species distribution models (SDMs). This represents a promising new research area in the study of ageing pattern variation in wild populations. Furthermore, the inclusion of telomere data in future physiological SDMs may improve our understanding of species distribution and population resilience. However, the use of telomeres within this context could be limited if no previous knowledge on the relevance of telomeres as markers of health and survival at the species level is available. Finally, we suggest some key practical and theoretical considerations that, ideally, future studies combining biogeographic and telomere data should pay attention.
Highlights
Ageing is a widespread phenomenon across the tree of life defined by a decline in organismal functionality and a decrease in reproduction and survival probability with time (Williams 1957, Jones et al 2014)
While the study of telomeres is well established at the organismal level, at least for some species, the implications that different environmental conditions have on telomere variation across broad spatial patterns are still an overlooked aspect in eco-evolutionary studies
Despite a relative scarcity of studies quantifying telomeres within a spatial context, the available literature already evidences the existence of divergence in telomere length and/or its dynamics in populations exposed to contrasting environments (Table 1)
Summary
Ageing is a widespread phenomenon across the tree of life defined by a decline in organismal functionality and a decrease in reproduction and survival probability with time (Williams 1957, Jones et al 2014). The study of molecular mechanisms, such as immunological and oxidative stress parameters, has provided important insights into the mechanistic causes behind the age-related increase in mortality within and across wildlife populations (Monaghan et al 2009, Selman et al 2012, Peters et al 2019) In this line, the shortening of telomeres (the end cap of chromosomes), is generally considered an indicator of health and ageing in biomedical and epidemiological research (Aubert and Lansdorp 2008, Muñoz-Lorente et al 2019), which explains the increasing interest for telomeres in eco-evolutionary studies (Monaghan et al 2018). We still lack a complete picture of the relative contribution of genetic and environmental components to telomere dynamics, nor its evolvability, which makes it difficult to fully understand the transgenerational effects of environmental variation on wildlife telomeres, and more studies are needed in this direction
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