Changes in temperature have occurred throughout Earth's history. However, current warming trends exacerbated by human activities impose severe and rapid loss of biodiversity. Although understanding ...the mechanisms orchestrating organismal response to climate change is important, remarkably few studies document their role in nature. This is because only few systems enable the combined analysis of genetic and plastic responses to environmental change over long time spans. Here, we characterize genetic and plastic responses to temperature increase in the aquatic keystone grazer Daphnia magna combining a candidate gene and an outlier analysis approach. We capitalize on the short generation time of our species, facilitating experimental evolution, and the production of dormant eggs enabling the analysis of long‐term response to environmental change through a resurrection ecology approach. We quantify plasticity in the expression of 35 candidate genes in D. magna populations resurrected from a lake that experienced changes in average temperature over the past century and from experimental populations differing in thermal tolerance isolated from a selection experiment. By measuring expression in multiple genotypes from each of these populations in control and heat treatments, we assess plastic responses to extreme temperature events. By measuring evolutionary changes in gene expression between warm‐ and cold‐adapted populations, we assess evolutionary response to temperature changes. Evolutionary response to temperature increase is also assessed via an outlier analysis using EST‐linked microsatellite loci. This study provides the first insights into the role of plasticity and genetic adaptation in orchestrating adaptive responses to environmental change in D. magna.
The Glanville fritillary butterfly (Melitaea cinxia) has been studied in the Åland Islands in Finland since 1991, where it occurs as a classic metapopulation in a large network of 4000 dry meadows. ...Much ecological work has been conducted on this species, but population genetic studies have been hampered by paucity of suitable genetic markers. Here, using single nucleotide polymorphisms and microsatellites developed for the Glanville fritillary, we examine the correspondence between the demographic and genetic spatial structures. Given the dynamic nature of the metapopulation, the current genetic spatial structure may bear a signal of past changes in population sizes and past patterns of gene flow rather than reflect the current demographic structure or landscape structure. We analyse this question with demographic data for 10 years, using the Rand index to assess the similarity between the genetic, demographic, and landscape spatial structures. Our results show that the current genetic spatial structure is better explained by the past rather than by the current demographic spatial structure or by the spatial configuration of the habitat in the landscape. Furthermore, current genetic diversity is significantly explained by past metapopulation sizes. The time lag between major demographic events and change in the genetic spatial structure and diversity has implications for the study of spatial dynamics.
Allozyme variation at the phosphoglucose isomerase (PGI) locus in the Glanville fritillary butterfly (Melitaea cinxia) is associated with variation in flight metabolic rate, dispersal rate, fecundity ...and local population growth rate. To map allozyme to DNA variation and to survey putative functional variation in genomic DNA, we cloned the coding sequence of Pgi and identified nonsynonymous variable sites that determine the most common allozyme alleles. We show that these single-nucleotide polymorphisms (SNPs) exhibit significant excess of heterozygotes in field-collected population samples as well as in laboratory crosses. This is in contrast to previous results for the same species in which other allozymes and SNPs were in Hardy-Weinberg equilibrium or exhibited an excess of homozygotes. Our results suggest that viability selection favours Pgi heterozygotes. Although this is consistent with direct overdominance at Pgi, we cannot exclude the possibility that heterozygote advantage is caused by the presence of one or more deleterious alleles at linked loci.
Morphological investigations of motile cells and cysts of a small dinoflagellate (strain CCMP 2088) isolated from Canadian Arctic waters were carried out under both light and scanning electron ...microscopy. This species strongly resembled Polarella glacialis (strain CCMP 1383), which up to now was known only from Antarctic sea ice. The photosynthetic pigment composition of strain CCMP 2088 is typical of dinoflagellates, with peridinin as a major accessory pigment. Phylogenetic relationships between the two strains and other dinoflagellate species were inferred from SSU nrDNA using Neighbour Joining and weighted parsimony analyses. Our results showed that strain CCMP 2088 and P. glacialis (strain CCMP 1383) grouped in the same clade (Suessiales clade), showing high similarity values (0.99%). Morphological and molecular data support the assignment of the Arctic strain to P. glacialis. The free-living Gymnodinium simplex and the two P. glacialis strains have a basal position in the Suessiales clade, as compared to Symbiodinium spp.
In nonpolypoid colorectal lesions, the presence of irregular, distorted glands in the colon (a disrupted crypt pattern) on magnification chromoendoscopy (MCE) is strongly associated with submucosal ...invasive cancer. The aim of the present study was to evaluate the ability of MCE to differentiate between an invasive crypt pattern and a noninvasive crypt pattern, including nonneoplastic lesions, and to assess the ability of this MCE classification to predict invasiveness and allow patients to be selected for endoscopic resection or surgical resection.
In a prospective study including 1560 colonoscopies, 153 flat or depressed colorectal lesions were evaluated with MCE among 534 colorectal lesions; the remainder had a polypoid appearance. The pit pattern was classified as nonneoplastic (type II) or neoplastic (types III - V), and the latter was subdivided into noninvasive (types III or IV) or submucosally invasive (type V). Lesions with a nonneoplastic and noninvasive neoplastic appearance were resected endoscopically if technically feasible, whereas those with a type V pattern were resected surgically. The resection specimens were analyzed histologically in relation to the Vienna classification.
Using this management strategy based on the pit pattern, 86 % (n = 70) of the type II lesions were hyperplastic; the remaining 11 had low-grade intraepithelial neoplasia. Type III and IV lesions (n = 58) represented either low-grade or high-grade intraepithelial neoplasia in 95 % of the cases. Three patients had sm1 (n = 2) or sm2/3 invasive cancers. Among the patients with type V lesions (n = 14), 11 had invasive cancers (four sm1 and seven sm2/3). Endoscopic differentiation based on the pit pattern thus had a positive predictive value (PPV) of 86 % and a negative predictive value of 96 % for distinguishing between nonneoplastic and neoplastic lesions. The pit pattern criteria for distinguishing between invasive and noninvasive neoplasia (including nonneoplastic lesions), and hence the choice between endoscopic and surgical resection, had a PPV of 79 % and a NPV of 98 %. Excluding nonneoplastic lesions, the NPV would be 95 %.
The endoscopic pit pattern on MCE has only a moderate predictive value for nonneoplastic lesions, so that leaving these flat hyperplastic lesions in place on the basis of the endoscopic magnification appearance alone cannot be generally recommended. However, MCE has a good predictive value for guiding management toward either endoscopic resection (if technically feasible) or surgical resection.
In Nordic countries and across Europe, breast cancer screening participation is high. However, a significant number of breast cancer cases are still diagnosed due to symptoms between screening ...rounds, termed “interval cancers”. Radiologists use the interval cancer proportion as a proxy for the screening false negative rate (ie, 1‐sensitivity). Our objective is to enhance our understanding of interval cancers by applying continuous tumour growth models to data from a study involving incident invasive breast cancer cases. Building upon previous findings regarding stationary distributions of tumour size and growth rate distributions in non‐screened populations, we develop an analytical expression for the proportion of interval breast cancer cases among regularly screened women. Our approach avoids relying on estimated background cancer rates. We make specific parametric assumptions concerning tumour growth and detection processes (screening or symptoms), but our framework easily accommodates alternative assumptions. We also show how our developed analytical expression for the proportion of interval breast cancers within a screened population can be incorporated into an approach for fitting tumour growth models to incident case data. We fit a model on 3493 cases diagnosed in Sweden between 2001 and 2008. Our methodology allows us to estimate the distribution of tumour sizes at the most recent screening for interval cancers. Importantly, we find that our model‐based expected incidence of interval breast cancers aligns closely with observed patterns in our study and in a large Nordic screening cohort. Finally, we evaluate the association between screening interval length and the interval cancer proportion. Our analytical expression represents a useful tool for gaining insights into the performance of population‐based breast cancer screening programs.
Posidonia oceanica is an endemic seagrass in the Mediterranean Sea, where it provides important ecosystem services and sustains a rich and diverse ecosystem. P. oceanica meadows extend from the ...surface to 40 meters depth. With the aim of boosting research in this iconic species, we generated a comprehensive RNA-Seq data set for P. oceanica by sequencing specimens collected at two depths and two times during the day. With this approach we attempted to capture the transcriptional diversity associated with change in light and other depth-related environmental factors. Using this extensive data set we generated gene predictions and identified an extensive catalogue of potential Simple Sequence Repeats (SSR) markers. The data generated here will open new avenues for the analysis of population genetic features and functional variation in P. oceanica. In total, 79,235 contigs were obtained by the assembly of 70,453,120 paired end reads. 43,711 contigs were successfully annotated. A total of 17,436 SSR were identified within 13,912 contigs.
PDF
