Is Aporia crataegi unsuitable host of Wolbachia symbionts?

The Black-veined White Aporia crataegi (Lepidoptera: Pieridae) is a trans-Palearctic species causing damage to various fruit and berry crops. Here we analyzed Wolbachia infection in A. crataegi populations. Wolbachia bacteria are maternally transmitted intracellular symbionts of many arthropods, including numerous Lepidoptera. We have studied 376 samples of A. crataegi collected in 10 regions of Russia from the Far East to Kaliningrad. Wolbachia prevalence was very low; only eight Wolbachia-positive specimens of A. crataegi were detected in Yakutia, Republic of Buryatia, Sverdlovsk and Kaliningrad Provinces, and no infection was found in other localities. Two Wolbachia haplotypes, ST-19 and ST-109, from A and B supergroups respectively, were identified using the multilocus sequence typing (MLST) protocol. These haplotypes were also previously reported in different lepidopteran species. Both Wolbachia haplotypes were associated with the same mtDNA haplotype (as inferred from the cytochrome oxidase subunit I gene) of A. crataegi, and ST-19 with two mtDNA haplotypes. This incongruence of maternally inherited agents indicates independent cases of the bacteria acquisition in A. crataegi history. The above data suggest that Wolbachia can infect Aporia crataegi but cannot establish in the host populations.

Kin relationships in cultural species of the marine realm: case study of a matrilineal social group of sperm whales off Mauritius island, Indian Ocean

Understanding the organization and dynamics of social groups of marine mammals through the study of kin relationships is particularly challenging . Here, we studied a stable social group of sperm whales off Mauritius, using underwater observations, individual-specific identification, non-invasive sampling and genetic analyses based on mitochondrial sequencing and microsatellite profiling. Twenty-four sperm whales were sampled between 2017 and 2019. All individuals except one adult female shared the same mitochondrial DNA (mtDNA) haplotype—one that is rare in the western Indian Ocean—thus confirming with near certainty the matrilineality of the group. All probable first- and second-degree kin relationships were depicted in the sperm whale social group: 13 first-degree and 27 second-degree relationships were identified. Notably, we highlight the likely case of an unrelated female having been integrated into a social unit, in that she presented a distinct mtDNA haplotype and no close relationships with any members of the group. Investigating the possible matrilineality of sperm whale cultural units (i.e. vocal clans) is the next step in our research programme to elucidate and better apprehend the complex organization of sperm whale social groups.

Prediction of mitochondrial genome-wide variation through sequencing of mitochondrion-enriched extracts

Although mitochondrial DNA (mtDNA) haplotype variation is often applied for estimating population dynamics and phylogenetic relationships, economical and generalized methods for entire mtDNA genome enrichment prior to high-throughput sequencing are not readily available. This study demonstrates the utility of differential centrifugation to enrich for mitochondrion within cell extracts prior to DNA extraction, short-read sequencing, and assembly using exemplars from eight maternal lineages of the insect species, Ostrinia nubilalis. Compared to controls, enriched extracts showed a significant mean increase of 48.2- and 86.1-fold in mtDNA based on quantitative PCR, and proportion of subsequent short sequence reads that aligned to the O. nubilalis reference mitochondrial genome, respectively. Compared to the reference genome, our de novo assembled O. nubilalis mitochondrial genomes contained 82 intraspecific substitution and insertion/deletion mutations, and provided evidence for correction of mis-annotated 28 C-terminal residues within the NADH dehydrogenase subunit 4. Comparison to a more recent O. nubilalis mtDNA assembly from unenriched short-read data analogously showed 77 variant sites. Twenty-eight variant positions, and a triplet ATT codon (Ile) insertion within ATP synthase subunit 8, were unique within our assemblies. This study provides a generalizable pipeline for whole mitochondrial genome sequence acquisition adaptable to applications across a range of taxa.

Mitogenome Diversity and Maternal Origins of Guangxi Cattle Breeds

Guangxi Province is located in the southernmost region of China, adjacent to the hotspot that is considered to be the putative migratory corridor or domestication area for Chinese indicine cattle. Here, we investigated the evolutionary status of Guangxi native breeds, Longlin (n = 21), Nandan (n = 18), and Weizhou cattle (n = 17) using mitogenome sequencing. Our results show that Bos indicus sub-haplogroup I1a predominates in Guangxi cattle breeds. Population structure by multidimensional-scaling analysis significantly differentiates Weizhou from the other two breeds (Longlin and Nandan). Moreover, the mtDNA haplotype composition and FST values indicate that the formation of Longlin and Nandan breeds may have been affected by Indian indicine, whereas, Weizhou island might have preserved pure Chinese indicine cattle due to its geographical isolation. We speculate that following the initial entry of zebu into southern China, the subsequent introgression of Indian indicine may have influenced the matrilineal origin of local breeds in southwestern China.

Sex-specific effects of mitochondrial haplotype on metabolic rate in Drosophila melanogaster support predictions of the Mother's Curse hypothesis

Evolutionary theory proposes that maternal inheritance of mitochondria will facilitate the accumulation of mitochondrial DNA (mtDNA) mutations that are harmful to males but benign or beneficial to females. Furthermore, mtDNA haplotypes sampled from across a given species distribution are expected to differ in the number and identity of these ‘male-harming’ mutations they accumulate. Consequently, it is predicted that the genetic variation which delineates distinct mtDNA haplotypes of a given species should confer larger phenotypic effects on males than females (reflecting mtDNA mutations that are male-harming, but female-benign), or sexually antagonistic effects (reflecting mutations that are male-harming, but female-benefitting). These predictions have received support from recent work examining mitochondrial haplotypic effects on adult life-history traits in Drosophila melanogaster . Here, we explore whether similar signatures of male-bias or sexual antagonism extend to a key physiological trait—metabolic rate. We measured the effects of mitochondrial haplotypes on the amount of carbon dioxide produced by individual flies, controlling for mass and activity, across 13 strains of D. melanogaster that differed only in their mtDNA haplotype. The effects of mtDNA haplotype on metabolic rate were larger in males than females. Furthermore, we observed a negative intersexual correlation across the haplotypes for metabolic rate. Finally, we uncovered a male-specific negative correlation, across haplotypes, between metabolic rate and longevity. These results are consistent with the hypothesis that maternal mitochondrial inheritance has led to the accumulation of a sex-specific genetic load within the mitochondrial genome, which affects metabolic rate and that may have consequences for the evolution of sex differences in life history. This article is part of the theme issue ‘Linking the mitochondrial genotype to phenotype: a complex endeavour’.

Quasi-Mendelian Paternal Inheritance of mitochondrial DNA: A notorious artifact, or anticipated mtDNA behavior?

A recent report by Luo et al (2018) in PNAS (DOI:10.1073/pnas.1810946115) presented evidence of biparental inheritance of mitochondrial DNA. The pattern of inheritance, however, resembled that of a nuclear gene. The authors explained this peculiarity with Mendelian segregation of a faulty gatekeeper gene that permits survival of paternal mtDNA in the oocyte. Three other groups (Vissing, 2019; Lutz-Bonengel and Parson, 2019; Salas et al, 2019), however, posited the observation was an artifact of inheritance of mtDNA nuclear pseudogenes (NUMTs), present in the father’s nuclear genome. We present justification that both interpretations are incorrect, but that the original authors did, in fact, observe biparental inheritance of mtDNA. Our alternative model assumes that because of initially low paternal mtDNA copy number these copies are randomly partitioned into nascent cell lineages. The paternal mtDNA haplotype must have a selective advantage, so ‘seeded’ cells will tend to proceed to fixation of the paternal haplotype in the course of development. We use modeling to emulate the dynamics of paternal genomes and predict their mode of inheritance and distribution in somatic tissue. The resulting offspring is a mosaic of cells that are purely maternal or purely paternal – including in the germline. This mosaicism explains the quasi-Mendelian segregation of the paternal mDNA. Our model is based on known aspects of mtDNA biology and explains all of the experimental observations outlined in Luo et. al., including maternal inheritance of the grand-paternal mtDNA.

Invasion genetics of the silver carp (Hypophthalmichthys molitrix) across North America: Differentiation of fronts, introgression, and eDNA detection

The invasive silver carpHypophthalmichthys molitrixescaped from southern U.S. aquaculture during the 1970s to spread throughout the Mississippi River basin and steadily moved northward, now reaching the threshold of the Laurentian Great Lakes. The silver carp is native to eastern Asia and is a large, prolific filter-feeder that decreases food availability for fisheries. The present study evaluates its population genetic variability and differentiation across the introduced range using 10 nuclear DNA microsatellite loci, sequences of two mitochondrial genes (cytochromeband cytochromecoxidase subunit 1), and a nuclear gene (ribosomal protein S7 gene intron 1). Populations are analyzed from two invasion fronts threatening the Great Lakes (the Illinois River outside Lake Michigan and the Wabash River, leading into the Maumee River and western Lake Erie), established areas in the southern and central Mississippi River, and a later Missouri River colonization. Results discern considerable genetic diversity and some significant population differentiation, with greater mtDNA haplotype diversity and unique microsatellite alleles characterizing the southern populations. Invasion fronts significantly differ, diverging from the southern Mississippi River population. About 3% of individuals contain a unique and very divergent mtDNA haplotype (primarily the southerly populations and the Wabash River), which may stem from historic introgression in Asia with female largescale silver carpH. harmandi. Nuclear microsatellites and S7 sequences of the introgressed individuals do not significantly differ from silver carp. MtDNA variation is used in a high-throughput sequence assay that identifies and distinguishes invasive carp species and their population haplotypes (includingH. molitrixandH. harmandi) at all life stages, in application to environmental (e)DNA water and plankton samples. We discerned silver and bighead carp eDNA from four bait and pond stores in the Great Lakes watershed, indicating that release from retailers comprises another likely vector. Our findings provide key baseline population genetic data for understanding and tracing the invasion’s progression, facilitating detection, and evaluating future trajectory and adaptive success.