Paternity tests support a diallelic self‐incompatibility system in a wild olive (Olea europaea subsp. laperrinei,Oleaceae)

Self‐incompatibility (SI) is the main mechanism that favors outcrossing in plants. By limiting compatible matings, SI interferes in fruit production and breeding of new cultivars. In the Oleeae tribe (Oleaceae), an unusual diallelic SI system (DSI) has been proposed for three distantly related species including the olive (Olea europaea), but empirical evidence has remained controversial for this latter. The olive domestication is a complex process with multiple origins. As a consequence, the mixing of S‐alleles from two distinct taxa, the possible artificial selection of self‐compatible mutants and the large phenological variation of blooming may constitute obstacles for deciphering SI in olive. Here, we investigate cross‐genotype compatibilities in the Saharan wild olive (O. e. subsp. laperrinei). As this taxon was geographically isolated for thousands of years, SI should not be affected by human selection. A population of 37 mature individuals maintained in a collection was investigated. Several embryos per mother were genotyped with microsatellites in order to identify compatible fathers that contributed to fertilization. While the pollination was limited by distance inside the collection, our results strongly support the DSI hypothesis, and all individuals were assigned to two incompatibility groups (G1 and G2). No self‐fertilization was observed in our conditions. In contrast, crosses between full or half siblings were frequent (ca. 45%), which is likely due to a nonrandom assortment of related trees in the collection. Finally, implications of our results for orchard management and the conservation of olive genetic resources are discussed.     

Reductions in the dietary niche of southern sea otters (Enhydra lutris nereis) from the Holocene to the Anthropocene

The sea otter (Enhydra lutris) is a marine mammal hunted to near extinction during the 1800s. Despite their well‐known modern importance as a keystone species, we know little about historical sea otter ecology. Here, we characterize the ecological niche of ancient southern sea otters (E. lutris nereis) using δ¹³C analysis and δ¹⁵N analysis of bones recovered from archaeological sites spanning ~7,000 to 350 years before present (N = 112 individuals) at five regions along the coast of California. These data are compared with previously published data on modern animals (N = 165) and potential modern prey items. In addition, we analyze the δ¹⁵N of individual amino acids for 23 individuals to test for differences in sea otter trophic ecology through time. After correcting for tissue‐specific and temporal isotopic effects, we employ nonparametric statistics and Bayesian niche models to quantify differences among ancient and modern animals. We find ancient otters occupied a larger isotopic niche than nearly all modern localities; likely reflecting broader habitat and prey use in prefur trade populations. In addition, ancient sea otters at the most southerly sites occupied an isotopic niche that was more than twice as large as ancient otters from northerly regions. This likely reflects greater invertebrate prey diversity in southern California relative to northern California. Thus, we suggest the potential dietary niche of sea otters in southern California could be larger than in central and northern California. At two sites, Año Nuevo and Monterey Bay, ancient otters had significantly higher δ¹⁵N values than modern populations. Amino acid δ¹⁵N data indicated this resulted from shifting baseline isotope values, rather than a change in sea otter trophic ecology. Our results help in better understanding the contemporary ecological role of sea otters and exemplify the strength of combing zooarchaeological and biological information to provide baseline data for conservation efforts.     

Genetic variation in an ephemeral mudflat species: The role of the soil seed bank and dispersal in river and secondary anthropogenic habitats

Many ephemeral mudflat species, which rely on a soil seed bank to build up the next generation, are endangered in their natural habitat due to the widespread regulation of rivers. The aim of the present study was to elucidate the role of the soil seed bank and dispersal for the maintenance of genetic diversity in populations of near‐natural river habitats and anthropogenic habitats created by traditional fish farming practices using Cyperus fuscus as a model. Using microsatellite markers, we found no difference in genetic diversity levels between soil seed bank and above‐ground population and only moderate differentiation between the two fractions. One possible interpretation is the difference in short‐term selection during germination under specific conditions (glasshouse versus field) resulting in an ecological filtering of genotypes out of the reservoir in the soil. River populations harbored significantly more genetic diversity than populations from the anthropogenic pond types. We suggest that altered levels and patterns of dispersal together with stronger selection pressures and historical bottlenecks in anthropogenic habitats are responsible for the observed reduction in genetic diversity. Dispersal is also supposed to largely prohibit genetic structure across Europe, although there is a gradient in private allelic richness from southern Europe (high values) to northern, especially north‐western, Europe (low values), which probably relates to postglacial expansion out of southern and/or eastern refugia.     

The complete chloroplast genome of Myriophyllum spicatum reveals a 4‐kb inversion and new insights regarding plastome evolution in Haloragaceae

Myriophyllum, among the most species‐rich genera of aquatic angiosperms with ca. 68 species, is an extensively distributed hydrophyte lineage in the cosmopolitan family Haloragaceae. The chloroplast (cp) genome is useful in the study of genetic evolution, phylogenetic analysis, and molecular dating of controversial taxa. Here, we sequenced and assembled the whole chloroplast genome of Myriophyllum spicatum L. and compared it to other species in the order Saxifragales. The complete chloroplast genome sequence of M. spicatum is 158,858 bp long and displays a quadripartite structure with two inverted repeats (IR) separating the large single copy (LSC) region from the small single copy (SSC) region. Based on sequence identification and the phylogenetic analysis, a 4‐kb phylogenetically informative inversion between trnE‐trnC in Myriophyllum was determined, and we have placed this inversion on a lineage specific to Myriophyllum and its close relatives. The divergence time estimation suggested that the trnE‐trnC inversion possibly occurred between the upper Cretaceous (72.54 MYA) and middle Eocene (47.28 MYA) before the divergence of Myriophyllum from its most recent common ancestor. The unique 4‐kb inversion might be caused by an occurrence of nonrandom recombination associated with climate changes around the K‐Pg boundary, making it interesting for future evolutionary investigations.     

Metapopulation dynamics and foraging plasticity in a highly vagile seabird,the southern rockhopper penguin

Population connectivity is driven by individual dispersal potential and modulated by natal philopatry. In seabirds, high vagility facilitates dispersal yet philopatry is also common, with foraging area overlap often correlated with population connectivity. We assess the interplay between these processes by studying past and current connectivity and foraging niche overlap among southern rockhopper penguin colonies of the coast of southern South America using genomic and stable isotope analyses. We found two distinct genetic clusters and detected low admixture between northern and southern colonies. Stable isotope analysis indicated niche variability between colonies, with Malvinas/Falklands colonies encompassing the species entire isotopic foraging niche, while the remaining colonies had smaller, nonoverlapping niches. A recently founded colony in continental Patagonia differed in isotopic niche width and position with Malvinas/Falklands colonies, its genetically identified founder population, suggesting the exploitation of novel foraging areas and/or prey items. Additionally, dispersing individuals found dead across the Patagonian shore in an unusual mortality event were also assigned to the northern cluster, suggesting northern individuals reach southern localities, but do not breed in these colonies. Facilitated by variability in foraging strategies, and especially during unfavorable conditions, the number of dispersing individuals may increase and enhance the probability of founding new colonies. Metapopulation demographic dynamics in seabirds should account for interannual variability in dispersal behavior and pay special attention to extreme climatic events, classically related to negative effects on population trends.     

Canadian polar bear population structure using genome‐wide markers

Predicting the consequences of environmental changes, including human‐mediated climate change on species, requires that we quantify range‐wide patterns of genetic diversity and identify the ecological, environmental, and historical factors that have contributed to it. Here, we generate baseline data on polar bear population structure across most Canadian subpopulations (n = 358) using 13,488 genome‐wide single nucleotide polymorphisms (SNPs) identified with double‐digest restriction site‐associated DNA sequencing (ddRAD). Our ddRAD dataset showed three genetic clusters in the sampled Canadian range, congruent with previous studies based on microsatellites across the same regions; however, due to a lack of sampling in Norwegian Bay, we were unable to confirm the existence of a unique cluster in that subpopulation. These data on the genetic structure of polar bears using SNPs provide a detailed baseline against which future shifts in population structure can be assessed, and opportunities to develop new noninvasive tools for monitoring polar bears across their range.     

Prior evolution in stochastic versus constant temperatures affects RNA virus evolvability at a thermal extreme

It is unclear how historical adaptation versus maladaptation in a prior environment affects population evolvability in a novel habitat. Prior work showed that vesicular stomatitis virus (VSV) populations evolved at constant 37°C improved in cellular infection at both 29°C and 37°C; in contrast, those evolved under random changing temperatures between 29°C and 37°C failed to improve. Here, we tested whether prior evolution affected the rate of adaptation at the thermal‐niche edge: 40°C. After 40 virus generations in the new environment, we observed that populations historically evolved at random temperatures showed greater adaptability. Deep sequencing revealed that most of the newly evolved mutations were de novo. Also, two novel evolved mutations in the VSV glycoprotein and replicase genes tended to co‐occur in the populations previously evolved at constant 37°C, whereas this parallelism was not seen in populations with prior random temperature evolution. These results suggest that prior adaptation under constant versus random temperatures constrained the mutation landscape that could improve fitness in the novel 40°C environment, perhaps owing to differing epistatic effects of new mutations entering genetic architectures that earlier diverged. We concluded that RNA viruses maladapted to their previous environment could “leapfrog” over counterparts of higher fitness, to achieve faster adaptability in a novel environment.     

Exploring context dependency in eco‐evolutionary patterns with the stick insect Timema cristinae

Rapid evolution can influence the ecology of populations, communities, and ecosystems, but the importance of evolution for ecological dynamics remains unclear, largely because the contexts in which evolution is powerful are poorly resolved. Here, we carry out a large observational study to test hypotheses about context dependency of eco‐evolutionary patterns previously identified on the stick insect Timema cristinae. Experiments and observations conducted in 2011 and 2012 documented predator‐mediated negative effects of camouflage maladaptation (i.e., evolutionary dynamics) on: (a) T. cristinae abundance and, (b) species richness and abundance of other arthropods. Here we show that camouflage maladaptation does not correlate with T. cristinae abundance and, instead, is associated with increased abundance and species richness of cohabitating arthropods. We furthermore find that plants with high levels of Timema maladaptation tend to have higher foliar nitrogen, that is, higher nutritional value, and more positive mass‐abundance slopes in the coexisting arthropod communities. We propose explanations for the observed contrasting results, such as negative density‐ and frequency‐dependent selection, feedbacks between herbivore abundance and plant nutritional quality, and common effects of predation pressure on selection and prey abundance. Our results demonstrate the utility of observational studies to assess the context dependency of eco‐evolutionary dynamics patterns and provide testable hypotheses for future work.