The crucial role of genome-wide genetic variation in conservation

The unprecedented rate of extinction calls for efficient use of genetics to help conserve biodiversity. Several recent genomic and simulation-based studies have argued that the field of conservation biology has placed too much focus on conserving genome-wide genetic variation, and that the field should instead focus on managing the subset of functional genetic variation that is thought to affect fitness. Here, we critically evaluate the feasibility and likely benefits of this approach in conservation. We find that population genetics theory and empirical results show that conserving genome-wide genetic variation is generally the best approach to prevent inbreeding depression and loss of adaptive potential from driving populations toward extinction. Focusing conservation efforts on presumably functional genetic variation will only be feasible occasionally, often misleading, and counterproductive when prioritized over genome-wide genetic variation. Given the increasing rate of habitat loss and other environmental changes, failure to recognize the detrimental effects of lost genome-wide genetic variation on long-term population viability will only worsen the biodiversity crisis.

The crucial role of genome-wide genetic variation in conservation

The unprecedented rate of extinction calls for efficient use of genetics to help conserve biodiversity. Several recent genomic and simulation-based studies have argued that the field of conservation biology has placed too much focus on the conservation of genome-wide genetic variation, and that this approach should be replaced with another that focuses instead on managing the subset of functional genetic variation that is thought to affect fitness. Here, we critically evaluate the feasibility and likely benefits of this approach in conservation. We find that population genetics theory and empirical results show that the conserving genome-wide genetic variation is generally the best approach to prevent inbreeding depression and loss of adaptive potential from driving populations towards extinction. Focusing conservation efforts on presumably functional genetic variation will only be feasible occasionally, often misleading, and counterproductive when prioritized over genome-wide genetic variation. Given the increasing rate of habitat loss and other environmental changes, failure to recognize the detrimental effects of lost genome-wide variation on long-term population viability will only worsen the biodiversity crisis.

Environmental and genetic influences on fitness-related traits in a hatchery coho salmon population.

Many natural and managed organisms will require substantial functional genetic variation to respond to selection in the face of rapid environmental change. Pacific salmon have experienced strong fluctuations in critical fitness traits over the past five decades. We examined genetic and phenotypic variability over three generations in a pedigreed hatchery population of coho salmon (Oncorhynchus kisutch) by monitoring seven fitness-related traits. Three-year-old adult return numbers varied more than five-fold, and jack (2-year old males) numbers varied 13-fold. Body sizes of Inch Creek coho salmon decreased consistently such that fish were only 40.7% as heavy in 2015 as in 2006 and female reproductive traits also decreased. During the study period, the majority of families produced returning adult progeny and effective population size was relatively constant. Heritability estimates for phenotypic traits were significantly greater than zero except for condition factor, and the estimated heritability for jacking was 0.42. The Inch Creek coho salmon population harbours substantial heritability for fitness and reproductive traits and thus likely retains significant capacity for adaptation despite many years of hatchery propagation.

The Role of Gene Encoding Variation ofDRD4in the Relationship between Inattention and Seasonal Daylight

ABSTRACTDaylight is the strongest synchronizer of human circadian rhythms. The circadian pathway hypothesis posits that synchrony between daylight and the circadian system relates to (in)attention. The dopamine neurotransmitter system is implicated in regulating the circadian system as well as in (attention)-deficit hyperactivity disorder [ADHD]. We studied the role of functional genetic variation in the gene encoding of dopamine-receptor-D4 (DRD4) in the relationship between inattention and seasonal daylight (changes). Gene-by-environment (GxE) mega-analyses were performed across eight studies including 3757 adult participants (with and without ADHD). We tested 1) theSpring-focus hypothesis, in which attention in 7R-carriers normalizes with increasing daylight levels preceding measurement, 2) theSummer-born ADHD hypothesis, in which 7R-carriers report more inattention when born in spring/summer than in autumn/winter, 3) theWinter-born ADHD hypothesis, opposing the second hypothesis. TheSpring-focus hypothesiswas upheld (1386 ADHD, 760 controls;d=-0.16 between periods); 7R-carriers reported evenlessinattention than 7R-non-carriers after winter solstice (d=0.27 between genotype-groups). Results were diagnosis-independent. Sensitivity analyses at individual study level confirmed the circannual patterns for 7R-carriers. Incorporating geographic changes into the independent measure, we also calculated changes in sunlight levels. This approach likewise showed that inattention correlated negatively with increasing light levels in 7R-carriers (r=-.135). Results emphasize peripheral effects of dopamine and the effects of (seasonal) daylight changes on cognition.

Start codon targeted polymorphism for evaluation of functional genetic variation and relationships in cultivated castor (Ricinus communis L.) genotypes

In the present study, 111 castor genotypes were differentiated by the DNA fingerprinting patterns using 37 SCoT primers. The selected primers amplified DNA fragments across the 111 genotypes studied with the number of amplified fragments varying from 3 (SCoT 14) to 10 (SCoT 30 and SCoT 44) and the amplicon size varied from 100 to 3000 bp. Of the 246 amplified bands, 186 were polymorphic with an average of 5.03 fragments per primer. The percentage of polymorphic bands ranged from 57.14 % (SCoT 34) to 100.00 % (SCoT 28 and SCoT 33) with an average of 77.50%. The polymorphic information content (PIC) values varied from 0.372 (SCoT 14) to 0.818 (SCoT 30) with an average of 0.677. A dendrogram was constructed from a genetic distance matrix based on profiles of the 37 SCoT primers using the unweighted pair-group method with the arithmetic average (UPGMA). According to analysis, the collection of 111 diverse accessions of castor was clustered into two main clusters (1 and 2). The first cluster were subdivided into two subclusters (1a and 1b). Subclaster 1a contained 11 genotypes of castor and subclaster 1b contained 6 genotypes of castor. Subclaster 2 were subdivided into two subclusters (2a and 2b). Subclaster 2a contained 44 castor genotypes and subclaster 2b contained 50 castor genotypes. Results showed the utility of SCoT markers for estimation of genetic diversity of castor genotypes leading to genotype identification.

A hybrid de novo genome assembly of the honeybee, Apis mellifera, with chromosome-length scaffolds

BackgroundThe ability to generate long sequencing reads and access long-range linkage information is revolutionizing the quality and completeness of genome assemblies. Here we use a hybrid approach that combines data from four genome sequencing and mapping technologies to generate a new genome assembly of the honeybee Apis mellifera. We first generated contigs based on PacBio sequencing libraries, which were then merged with linked-read 10x Chromium data followed by scaffolding using a BioNano optical genome map and a Hi-C chromatin interaction map, complemented by a genetic linkage map.ResultsEach of the assembly steps reduced the number of gaps and incorporated a substantial amount of additional sequence into scaffolds. The new assembly (Amel_HAv3) is significantly more contiguous and complete than the previous one (Amel_4.5), based mainly on Sanger sequencing reads. N50 of contigs is 120-fold higher (5.381 Mbp compared to 0.053 Mbp) and we anchor >98% of the sequence to chromosomes. All of the 16 chromosomes are represented as single scaffolds with an average of three sequence gaps per chromosome. The improvements are largely due to the inclusion of repetitive sequence that was unplaced in previous assemblies. In particular, our assembly is highly contiguous across centromeres and telomeres and includes hundreds of AvaI and AluI repeats associated with these features.ConclusionsThe improved assembly will be of utility for refining gene models, studying genome function, mapping functional genetic variation, identification of structural variants, and comparative genomics.