An official website of the United States government
Abstract The mechanisms that underlie senescence are not well understood in insects. Telomeres are conserved repetitive sequences at chromosome ends that protect DNA during replication. In many vertebrates, telomeres shorten during cell division and in response to stress and are often used as a cellular marker of senescence. However, little is known about telomere dynamics across the lifespan in invertebrates. We measured telomere length in larvae, prepupae, pupae, and adults of two species of solitary bees,Osmia lignariaandMegachile rotundata. Contrary to our predictions, telomere length was longer in later developmental stages in bothO. lignariaandM. rotundata.Longer telomeres occurred after emergence from diapause, which is a physiological state with increased tolerance to stress. InO. lignaria, telomeres were longer in adults when they emerged following diapause. InM. rotundata, telomeres were longer in the pupal stage and subsequent adult stage, which occurs after prepupal diapause. In both species, telomere length did not change during the 8 months of diapause. Telomere length did not differ by mass similarly across species or sex. We also did not see a difference in telomere length after adultO. lignariawere exposed to a nutritional stress, nor did length change during their adult lifespan. Taken together, these results suggest that telomere dynamics in solitary bees differ from what is commonly reported in vertebrates and suggest that insect diapause may influence telomere dynamics.
more »
« less
Telomere Length Differences Indicate Climate Change‐Induced Stress and Population Decline in a Migratory Bird
ABSTRACT Genomic projections of (mal)adaptation under future climate change, known as genomic offset, faces limited application due to challenges in validating model predictions. Individuals inhabiting regions with high genomic offset are expected to experience increased levels of physiological stress as a result of climate change, but documenting such stress can be challenging in systems where experimental manipulations are not possible. One increasingly common method for documenting physiological costs associated with stress in individuals is to measure the relative length of telomeres—the repetitive regions on the caps of chromosomes that are known to shorten at faster rates in more adverse conditions. Here we combine models of genomic offsets with measures of telomere shortening in a migratory bird, the yellow warbler (Setophaga petechia), and find a strong correlation between genomic offset, telomere length and population decline. While further research is needed to fully understand these links, our results support the idea that birds in regions where climate change is happening faster are experiencing more stress and that such negative effects may help explain the observed population declines.
more »
« less
- Award ID(s):
- 1942313
- PAR ID:
- 10610086
- Publisher / Repository:
- Molecular Ecology
- Date Published:
- Journal Name:
- Molecular Ecology
- ISSN:
- 0962-1083
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
ABSTRACT Yellow monkeyflowers (Mimulus guttatuscomplex, Phrymaceae) are a powerful system for studying ecological adaptation, reproductive variation, and genome evolution. To initiate pan‐genomics in this group, we present four chromosome‐scale assemblies and annotations of accessions spanning a broad evolutionary spectrum: two from a singleM. guttatuspopulation, one from the closely related selfing speciesM. nasutus, and one from a more divergent speciesM. tilingii. All assemblies are highly complete and resolve centromeric and repetitive regions. Comparative analyses reveal such extensive structural variation in repeat‐rich, gene‐poor regions that large portions of the genome are unalignable across accessions. As a result, thisMimuluspan‐genome is primarily informative in genic regions, underscoring limitations of resequencing approaches in such polymorphic taxa. We document gene presence–absence, investigate the recombination landscape using high‐resolution linkage data, and quantify nucleotide diversity. Surprisingly, pairwise differences at fourfold synonymous sites are exceptionally high—even in regions of very low recombination—reaching ~3.2% within a singleM. guttatuspopulation, ~7% within the interfertileM. guttatusspecies complex (approximately equal to SNP divergence between great apes and Old World monkeys), and ~7.4% between that complex and the reproductively isolatedM. tilingii. Genome‐wide patterns of nucleotide variation show little evidence of linked selection, and instead suggest that the concentration of genes (and likely selected sites) in high‐recombination regions may buffer diversity loss. These assemblies, annotations, and comparative analyses provide a robust genomic foundation forMimulusresearch and offer new insights into the interplay of recombination, structural variation, and molecular evolution in highly diverse plant genomes.more » « less
-
ABSTRACT Coastal organisms live in a dynamic environment where a myriad of environmental stressors, including climate change, ocean acidification, and human harvesting, act on variable spatio‐temporal scales. Each of these stressors may impose unique selective forces on a population, shaping a species' adaptive potential and its ability to persist under future climatic conditions. Genomic investigations of adaptive responses to environmental and anthropogenic disturbances remain rare, especially in marine systems. Here, we use whole genome sequencing data from the owl limpet,Lottia gigantea, and outlier detection methods to pinpoint signals of selection (1) across long‐standing environmental gradients spanning the species' distribution, (2) at the poleward edge of the species' range where it experienced a recent expansion, and (3) between sites vulnerable to or protected from human size‐selective harvesting within California. Loci associated with environmental gradients across the entire range show the strongest differentiation at the southern end of the species' range, potentially driven by adaptation to sea surface temperature and pH. Additionalad‐hocoutlier analyses revealed a distinct set of loci potentially under selection in the expanded range, with different functional roles than the range‐wide outliers. Despite demographic models suggesting that protection from harvesting has a positive impact on the abundance of large individuals, we did not find strong signals of selection or changes in genetic diversity between sites differing in harvesting vulnerability. Our findings suggest that range‐wide environmental selective signals established over longer time scales are distinct from those imposed by climatic anomalies at finer spatio‐temporal scales. We found that climatic variation has a stronger selective imprint than human harvesting, and thus conservation interventions should consider prioritizing the maintenance of climate‐related adaptive potential. Understanding how climatic trends and anomalies interact with anthropogenic pressures will allow us to make more informed decisions to sustain the evolutionary capacity ofL. giganteaand other key coastal species.more » « less
-
ABSTRACT Coral reefs are increasingly threatened by disease outbreaks, yet little is known about the genetic mechanisms underlying disease resistance. Since the 1970s, White Band Disease (WBD) has decimated the Caribbean staghorn coralAcropora cervicornis. However, 15% or more of individuals are highly disease‐resistant, and the genes controlling the production of Argonaut proteins, involved in microRNA (miRNA) post‐transcriptional gene silencing, are up‐regulated in WBD‐resistant corals. This suggests that miRNAs may be key regulators of coral immunity. In this study, we conducted an in situ disease transmission experiment with five healthy‐exposed control tanks and five WBD‐exposed tanks, each containing 50A. cervicornisgenotypes, sampled over 7 days and then sequenced miRNAs from 12 replicate genotypes, including 12 WBD‐exposed and 12 healthy‐exposed control fragments from two time points. We identified 67bona fidemiRNAs inA. cervicornis, 3 of which are differentially expressed in disease‐resistant corals. We performed a phylogenetic comparison of miRNAs across cnidarians and found greater conservation of miRNAs in more closely related taxa, including all three differentially expressed miRNAs being conserved in more than oneAcroporacoral. One of the three miRNAs has putative genomic targets involved in the cnidarian innate immunity. In addition, community detection coupled with over‐representation analysis of our miRNA–messenger RNA (mRNA) target network found two key uniqueA. cervicornismiRNAs regulating multiple important immune‐related pathways such as Toll‐like receptor pathway, endocytosis, and apoptosis. These findings highlight how multiple miRNAs may help the coral host maintain immune homeostasis in the presence of environmental stress including disease.more » « less
-
Abstract Intensifying climate change and an increasing need for understanding its impacts on ecological communities places new emphasis on testing environmental stress models (ESMs). Using a prior literature search plus references from a more recent search, I evaluated empirical support forESMs, focusing on whether consumer pressure on prey decreased (consumer stress model;CSM) or increased (prey stress model;PSM) with increasing environmental stress. Applying the criterion that testingESMsrequires conducting research at multiple sites along environmental stress gradients, the analysis found thatCSMswere most frequent, with ‘No Effect’ andPSMsoccurring at low but similar frequencies. This result contrasts to a prior survey in which ‘No Effect’ studies were most frequent, thus suggesting that consumers are generally more suppressed by stress than prey. Thus, increased climate change‐induced environmental stress seems likely to reduce, not increase impacts of consumers on prey more often than the reversemore » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/mec.17642
