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Do Early-Life Conditions Drive Variation in Senescence of Female Bighorn Sheep?

ABSTRACT: The rate of senescence may vary among individuals of a species according to individual life histories and environmental conditions. According to the principle of allocation, changes in mortality driven by environmental conditions influence how organisms allocate resources among costly functions. In several vertebrates, environmental conditions during early life impose trade-offs in allocation between early reproduction and maintenance. The effects of conditions experienced during early life on senescence, however, remain poorly documented in wild populations. We examined how several early-life environmental conditions affected reproductive and survival senescence in wild bighorn sheep. We found long-term effects of high population density at birth, precipitations during the winter before birth, and temperature during the winter following birth that decreased survival after 7 years of age. High temperature during the first summer and autumn of life and high Pacific decadal oscillation decreased reproductive success at old ages. However, harsh early-life environment did not influence the rate of senescence in either survival or reproduction. Contrary to our expectation, we found no trade-off between reproductive allocation prior to senescence and senescence. Our results do show that early-life environmental conditions are important drivers of later survival and reproductive success and contribute to intra-specific variation in late-life fitness, but not aging patterns. These conditions should therefore be considered when studying the mechanisms of senescence and the determinants of variation in both survival and reproductive senescence at older ages.

SUBMITTER: Pigeon G

PROVIDER: S-EPMC8173223 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Abstract The mitochondrial genome has been used in numerous species to discern evolutionary patterns, phylogeny, and speciation. Previous studies including mitochondrial genome assemblies in bighorn and domestic sheep indicate variation between these two species. This variation can be used to determine whether animal tissue originates from bighorn or domestic species. In this study, we designed and validated an assay that uses amplification of two targets in the mitochondrial genome followed by short read sequencing to identify single nucleotide polymorphisms (SNPs) in bighorn and domestic sheep. Tissue samples were acquired from two Rocky Mountain bighorn sheep and two domestic sheep (Suffolk and Icelandic breeds), and mitochondrial DNA was extracted. A target designed on the Cytochrome B (CYTB) gene (266 base pairs in length) and a target on the NADH dehydrogenase subunit 6 (ND6) gene (328 base pairs in length) were amplified using PCR and sequenced with an Illumina Mi-Seq. Sequences were aligned to Ovis aries Oar_v4.0 mitochondrial reference (NC_001941.1) and Ovis canadensis mitochondrial reference (JN181255), and variants were called using CLC Genomics Workbench v11.0 with sequence depth of over 40X. Bighorn sheep sequences aligned to the domestic mitochondrial reference displayed 17 SNPs in each target, with a total of 34 SNPs and 94% sequence identity, while domestic sequences displayed 0–2 SNPs for both targets and 99–100% sequence identity. Bighorn sheep sequences aligned to the bighorn mitochondrial reference displayed 0 variants and 100% sequence identity, while domestic sheep sequences displayed 16–17 SNPs in each target, with 33–34 total SNPs identified and 94% sequence identity. The assay designed in this study and variants identified can be used to determine whether samples are of Ovis aries or Ovis canadensis origin. Further, these data provide additional insight into mitochondrial genome variation between two Ovisspecies; one domestic and one wild.

Project description:Managing water (e.g., catchments) to increase the abundance and distribution of game is popular in arid regions, especially throughout the southwest United States, where biologists often manage water year-round for desert bighorn sheep (Ovis canadensis nelsoni). Bighorn may visit water when predators (e.g., mountain lions [Puma concolor], coyotes [Canis latrans]) do not, suggesting that differences in species ecology or their surface water requirements influence visit timing. Alternatively, visits by desert bighorn sheep and predators may align. The former outcome identifies opportunities to improve water management by providing water when desert bighorn sheep visit most, which hypothetically may reduce predator presence, range expansion and predation, thereby supporting objectives to increase sheep abundances. Since advancing water management hinges on understanding the patterns of species visits, we identified when these three species and mule deer (Odocoileus hemionus) visited managed waters in three North American deserts (Chihuahuan, Sonoran, Mojave). We unraveled the ecological basis describing why visits occurred by associating species visits with four weather variables using multi-site, multi-species models within a Bayesian hierarchical framework (3.4 million images; 105 locations; 7/2009-12/2016). Desert bighorn sheep concentrated visits to water within 4-5 contiguous months. Mountain lions visited water essentially year-round within all deserts. Higher maximum temperature influenced visits to water, especially for desert bighorn sheep. Less long-term precipitation (prior 6-week total) raised visits for all species, and influenced mountain lion visits 3-20 times more than mule deer and 3-37 times more than sheep visits. Visits to water by prey were inconsistent predictors of visits to water by mountain lions. Our results suggest improvements to water management by aligning water provision with the patterns and ecological explanations of desert bighorn sheep visits. We exemplify a scientific approach to water management for enhancing stewardship of desert mammals, be it the southwest United States or arid regions elsewhere.

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Do Early-Life Conditions Drive Variation in Senescence of Female Bighorn Sheep?

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