Genome Size and Labellum Epidermal Cell Size Are Evolutionarily Correlated With Floral Longevity in Paphiopedilum Species

Genome size is known to influence phenotypic traits in leaves and seeds. Although genome size is closely related to cellular and developmental traits across biological kingdoms, floral longevity is a floral trait with important fitness consequence, but less is known about the link between floral longevity and sizes of genomes and cells. In this study, we examined evolutionary coordination between genome size, floral longevity, and epidermal cell size in flowers and leaves in 13 Paphiopedilum species. We found that, across all the study species, the genome size was positively correlated with floral longevity but negatively associated with labellum epidermal cell size, and a negative relationship was found between floral longevity and labellum epidermal cell size. This suggested that genome size is potentially correlated with floral longevity, and genome size has an important impact on life-history trait. In addition, genome size was positively correlated with leaf epidermal cell size, which was different from the relationship in flower due to different selective pressures they experienced or different functions they performed. Therefore, genome size constraints floral longevity, and it is a strong predictor of cell size. The impact of genome size on reproduction might have more implications for the evolution of flowering plants and pollination ecology.

Connections to the Deep: Deep Vertical Migrations, an Important Part of the Life Cycle of Apherusa glacialis, an Arctic Ice-Associated Amphipod

Arctic sea ice contains a substantial amount of living biota of which part is lost through melt and export out of the Arctic Ocean every year. It is unclear how populations can be maintained within the Arctic Ocean. A representative ice inhabitant, the amphipod Apherusa glacialis was previously assumed to spend its entire life in the sea ice habitat, hence being dependent on sea ice to complete its life cycle. However, several recent studies report pelagic occurrences and suggest that seasonal vertical migrations might be an adaptive life history trait enabling a viable population size in the Arctic Ocean. In this study we use a particle-tracking model to investigate to what extent vertical migration might affect the species’ retention in the Arctic Ocean and the sea ice habitat. The modeled trajectories of A. glacialis were calculated based on ice drift and ocean currents from a coupled ocean – sea ice model covering the Arctic Ocean. We test two scenarios: (1) trajectories of A. glacialis that stay attached to the ice or follow the surface currents if they melt out of the ice and (2) trajectories of A. glacialis that undertake a seasonal vertical migration to drift with the currents at depth for parts of the year. In the multi-year model simulations it is assumed that after an initial period of 2 years A. glacialis that are located outside sea-ice cover each spring will perish while those located within the ice-covered region will reproduce. The model results show that a seasonal vertical migration both increases the total number of individuals and leads to a population distribution within the Arctic Ocean more in line with previous findings than the results from the non-migrating A. glacialis. Our results support the hypothesis that a seasonal migration may be an adaptive life history strategy in this species.

Assessment of Plasmodium falciparum Infection and Fitness of Genetically Modified Anopheles gambiae Aimed at Mosquito Population Replacement

Genetically modified (GM) mosquitoes expressing anti-plasmodial effectors propagating through wild mosquito populations by means of gene drive is a promising tool to support current malaria control strategies. The process of generating GM mosquitoes involves genetic transformation of mosquitoes from a laboratory colony and, often, interbreeding with other GM lines to cross in auxiliary traits. These mosquito colonies and GM lines thus often have different genetic backgrounds and GM lines are invariably highly inbred, which in conjunction with their independent rearing in the laboratory may translate to differences in their susceptibility to malaria parasite infection and life history traits. Here, we show that laboratory Anopheles gambiae colonies and GM lines expressing Cas9 and Cre recombinase vary greatly in their susceptibility to Plasmodium falciparum NF54 infection. Therefore, the choice of mosquitoes to be used as a reference when conducting infection or life history trait assays requires careful consideration. To address these issues, we established an experimental pipeline involving genetic crosses and genotyping of mosquitoes reared in shared containers throughout their lifecycle. We used this protocol to examine whether GM lines expressing the antimicrobial peptide (AMP) Scorpine in the mosquito midgut interfere with parasite infection and mosquito survival. We demonstrate that Scorpine expression in the Peritrophin 1 (Aper1) genomic locus reduces both P. falciparum sporozoite prevalence and mosquito lifespan; both these phenotypes are likely to be associated with the disturbance of the midgut microbiota homeostasis. These data lead us to conclude that the Aper1-Sco GM line could be used in proof-of-concept experiments aimed at mosquito population replacement, although the impact of its reduced fitness on the spread of the transgene through wild populations requires further investigation.

Mitochondrial mutational spectrum is associated with mammalian longevity: a novel signature of oxidative damage.

The mutational spectrum of the mitochondrial DNA (mtDNA) does not resemble any of the known mutational signatures of the nuclear genome and variation in mtDNA mutational spectra between different tissues and organisms is still incomprehensible. Since mitochondria is tightly involved in aerobic energy production, it is expected that mtDNA mutational spectra may be affected by the oxidative damage which is increasing with organismal aging. However, the well-documented mutational signature of the oxidative damage, G>T substitutions, is typical only for the nuclear genome while it is extremely rare in mtDNA. Thus it is still unclear if there is a mitochondria-specific mutational signature of the oxidative damage. Here, reconstructing mtDNA mutational spectra for 424 mammalian species with variable generation length which is a proxy for oocyte age, we observed that the frequency of AH>GH substitutions (H - heavy chain notation) is positively correlated with organismal longevity. This mutational bias from AH to GH significantly affected the nucleotide content of analyzed 650 complete mammalian mitochondrial genomes, where fourfold degenerative synonymous positions of long-lived species become more AH poor and GH rich. Because (i) A>G is a substitution, typical for mtDNA; (ii) it is characterized by very strong asymmetry: A>G is several-fold more frequent on a heavy chain as compared to the light one; (iii) it is sensitive to the time being single-stranded during mtDNA asynchronous replication; (iv) it is associated with oxidative damage of single-stranded DNA in recent experimental studies we propose that A>G is a novel mutational signature of age-associated oxidative damage of single-stranded mtDNA. The described association of the mtDNA mutational spectra with a species-specific life-history trait can significantly affect general patterns of molecular evolution of mtDNA.

Perinatal Food Deprivation Modifies the Caloric Restriction Response in Adult Mice Through Sirt1

Variations in the availability of nutritional resources in animals can trigger reversible adjustments, which in the short term are manifested as behavioral and physiological changes. Several of these responses are mediated by Sirt1, which acts as an energy status sensor governing a global genetic program to cope with changes in nutritional status. Growing evidence suggests a key role of the response of the perinatal environment to caloric restriction in the setup of physiological responses in adulthood. The existence of adaptive predictive responses has been proposed, which suggests that early nutrition could establish metabolic capacities suitable for future food-scarce environments. We evaluated how perinatal food deprivation and maternal gestational weight gain impact the transcriptional, physiological, and behavioral responses in mice, when acclimated to caloric restriction in adulthood. Our results show a strong predictive capacity of maternal weight and gestational weight gain, in the expression of Sirt1 and its downstream targets in the brain and liver, mitochondrial enzymatic activity in skeletal muscle, and exploratory behavior in offspring. We also observed differential responses of both lactation and gestational food restriction on gene expression, thermogenesis, organ masses, and behavior, in response to adult caloric restriction. We conclude that the early nutritional state could determine the magnitude of responses to food scarcity later in adulthood, mediated by the pivotal metabolic sensor Sirt1. Our results suggest that maternal gestational weight gain could be an important life history trait and could be used to predict features that improve the invasive capacity or adjustment to seasonal food scarcity of the offspring.

Density-by-diet interactions during larval development shape adult life-history trait expression and fitness in a polyphagous fly

Habitat quality early in life determines individual fitness, with possible long-term evolutionary effects on groups and populations. In holometabolous insects, larval ecology plays a major role in determining the expression of traits in adulthood, but how ecological conditions during larval stage interact to shape adult life-history and fitness, particularly in non-model organisms, remains subject to scrutiny. Consequently, our knowledge of the interactive effects of ecological factors on insect development is limited. Here, using the polyphagous fly Bactrocera tryoni, we conducted a fully-factorial design where we manipulated larval density and larval diet (protein-rich, standard, and sugar-rich) to gain insights into how these ecological factors interact to modulate adult fitness. As expected, a protein-rich diet resulted in faster larval development, heavier and leaner adults that were more fecund compared with standard and sugar-rich diets, irrespective of larval density. Females from the protein-rich larval diet had overall higher reproductive rate (i.e., eggs per day) than females from other diets, and reproductive rate decreased linearly with density for females from the protein-rich but non-linearly for females from the standard and sugar-rich diets over time. Surprisingly, adult lipid reserve increased with larval density for adults from the sugar-rich diet (as opposed to decreasing, as in other diets), possibly due to a stress-response to an extremely adverse condition during development (i.e., high intraspecific competition and poor nutrition). Together, our results provide insights into how ecological factors early in life interact and shape the fate of individuals through life-stages in holometabolous insects.

Reproductive Allocation and Maternal Investment in Intertidal Whelks

<p>Parental investment per offspring is a key life history trait in which offspring size and number combinations are balanced in order to maximise fitness. When food is scarce and energy for reproduction is reduced, changes in reproductive allocation can be expected. These adjustments may go on to influence the growth and survival of the next generation. Trade-offs in reproductive allocation in response to food availability occurred differently in each of the three whelks species of this study. However, each species traded numbers of offspring rather than size of offspring when fed low food. Offspring size was more variable among and within capsules than among food treatments. Capsule size was a plastic trait that varied in response to food treatments in each of the species and varied among populations of the same species. Carry-over effects of maternal nutrition influenced juvenile growth in all three species. However, while juvenile growth was greater when adults were fed high food in two of the species, high adult food suppressed the growth of juveniles of the third species. This may be a mechanism to prevent potential negative consequences of rapid growth. There was no evidence of a maternal effect of mortality in any of the three species. Greater variation in hatchling size occurred in the species in which nurse egg feeding occurred. Nurse egg feeding may be a successful strategy in unpredictable environments where optimal offspring size changes from year to year. Regional differences in reproductive allocation between whelks separated by small distances suggest that populations may be isolated from one another and may need to be managed separately for conservation purposes. This study highlights the influence of maternal nutritional effects on life history and the potential impacts that these may have on population and community structure.</p>

Reproductive Allocation and Maternal Investment in Intertidal Whelks

<p>Parental investment per offspring is a key life history trait in which offspring size and number combinations are balanced in order to maximise fitness. When food is scarce and energy for reproduction is reduced, changes in reproductive allocation can be expected. These adjustments may go on to influence the growth and survival of the next generation. Trade-offs in reproductive allocation in response to food availability occurred differently in each of the three whelks species of this study. However, each species traded numbers of offspring rather than size of offspring when fed low food. Offspring size was more variable among and within capsules than among food treatments. Capsule size was a plastic trait that varied in response to food treatments in each of the species and varied among populations of the same species. Carry-over effects of maternal nutrition influenced juvenile growth in all three species. However, while juvenile growth was greater when adults were fed high food in two of the species, high adult food suppressed the growth of juveniles of the third species. This may be a mechanism to prevent potential negative consequences of rapid growth. There was no evidence of a maternal effect of mortality in any of the three species. Greater variation in hatchling size occurred in the species in which nurse egg feeding occurred. Nurse egg feeding may be a successful strategy in unpredictable environments where optimal offspring size changes from year to year. Regional differences in reproductive allocation between whelks separated by small distances suggest that populations may be isolated from one another and may need to be managed separately for conservation purposes. This study highlights the influence of maternal nutritional effects on life history and the potential impacts that these may have on population and community structure.</p>

Standardised empirical dispersal kernels emphasise the pervasiveness of long-distance dispersal in European birds

Dispersal is a key life-history trait for most species and essential to ensure connectivity and gene flow between populations and facilitate population viability in variable environments. Despite the increasing importance of range shifts due to global change, dispersal has proved difficult to quantify, limiting empirical understanding of this phenotypic trait and wider synthesis. Here we aim to estimate and compare empirical dispersal kernels for European breeding birds considering average dispersal, natal (before first breeding) and breeding dispersal (between subsequent breeding attempts), and test whether different dispersal properties are phylogenetically conserved. We standardised and analysed data from an extensive volunteer-based bird ring-recoveries database in Europe (EURING) by accounting for biases related to different censoring thresholds in reporting between countries and to migratory movements. Then, we fitted four widely used probability density functions in a Bayesian framework to compare and provide the best statistical descriptions of the average, the natal and the breeding dispersal kernels for each bird species. The dispersal movements of the 234 European bird species analysed were statistically best explained by heavy-tailed kernels, meaning that while most individuals disperse over short distances, long-distance dispersal is a feature in almost all bird species. The overall phylogenetic signal in both median and long dispersal distances was low (Pagel lambda < 0.40), implying a high degree of taxonomic generality in our findings. As expected in birds, natal dispersal was 5 Km greater as an average than breeding dispersal for most species (88% species analysed). Our comprehensive analysis of empirical kernels indicates that long-distance dispersal is common among European breeding bird species and across life stages. The dispersal estimates offer a first guide to selecting appropriate dispersal kernels in range expansion studies and provide new avenues to improve our understanding of the mechanisms and rules underlying dispersal events.