Genetic diversity of Philaenus spumarius and P. tesselatus (Hemiptera,Aphrophoridae): implications for evolution and taxonomy

The meadow spittlebugs Philaenus spumarius and P. tesselatus are closely related taxa with uncertain taxonomic position in the light of previous morphological, ecological, cytological and molecular research. Despite morphological homogeneity of P. spumarius (with the exception of high colour and pattern polymorphism) across its wide Holarctic range, it is possible that additional taxa (species or subspecies) exist. Philaenus spumarius is a potentially important pest in parts of its range where it was introduced. We used DNA markers to describe the genetic diversity of P. spumarius and P. tesselatus and to verify the taxonomic status of P. tesselatus and remote populations of the former species. The mitochondrial (cytochrome B) data showed that there are two main groups encompassing a northeastern (Asia and north‐central Europe) and a southwestern (Mediterranean area and western Europe, including North American specimens) clade. According to the elongation factor‐1α gene, there are three main clades: northeastern (Eurasiatic clade, E1), southeastern (east Mediterranean – Caucasus clade, E2) and southwestern (Iberian clade, E3). These two or three mitochondrial and nuclear clades could be considered as separate taxonomic units. On the other hand, all studied individuals of both species possessed the same internal transcribed spacer 2 haplotype. American specimens most probably originated from some western European populations. All studied specimens of P. tesselatus belong to the southwestern clade and western Mediterranean cluster. Therefore, together with cytological data, its species status is doubtful. To definitively solve the taxonomic status of P. tesselatus and populations of P. spumarius, further research using more samples and more genetic markers are needed.     

The learning advantage: bird species that learn their song show a tighter adjustment of song to noisy environments than those that do not learn

Song learning has evolved within several avian groups. Although its evolutionary advantage is not clear, it has been proposed that song learning may be advantageous in allowing birds to adapt their songs to the local acoustic environment. To test this hypothesis, we analysed patterns of song adjustment to noisy environments and explored their possible link to song learning. Bird vocalizations can be masked by low‐frequency noise, and birds respond to this by singing higher‐pitched songs. Most reports of this strategy involve oscines, a group of birds with learning‐based song variability, and it is doubtful whether species that lack song learning (e.g. suboscines) can adjust their songs to noisy environments. We address this question by comparing the degree of song adjustment to noise in a large sample of oscines (17 populations, 14 species) and suboscines (11 populations, 7 species), recorded in Brazil (Manaus, Brasilia and Curitiba) and Mexico City. We found a significantly stronger association between minimum song frequency and noise levels (effect size) in oscines than in suboscines, suggesting a tighter match in oscines between song transmission capacity and ambient acoustics. Suboscines may be more vulnerable to acoustic pollution than oscines and thus less capable of colonizing cities or acoustically novel habitats. Additionally, we found that species whose song frequency was more divergent between populations showed tighter noise–song frequency associations. Our results suggest that song learning and/or song plasticity allows adaptation to new habitats and that this selective advantage may be linked to the evolution of song learning and plasticity.     

Life cycle of Chattonella marina (Raphidophyceae) inferred from analysis of microsatellite marker genotypes

Red tides of Chattonella spp. have caused continuous damage to Japanese aquaculture, however, the life cycle of this organism remains incompletely understood. To further investigate this matter, we assessed genotypes at 14 microsatellite markers in three varieties of Chattonella marina, viz., C. marina var. antiqua, C. marina var. marina, and C. marina var. ovata, to establish whether Chattonella undergoes asexual diploidization or sexual reproduction. After genotyping 287 strains of C. marina, all but one of these strains was shown to be heterozygous for at least some loci, and thus, in the diploid state, suggesting that Chattonella strains undergo sexual reproduction. In addition, we performed single‐cell amplification on ‘small cells’ that are derived from vegetative cells under dark and low‐nutrient conditions. The results indicated the existence of two types of small cells. The ‘Small cell Type 1’ was found to be heterozygous, genotypically equivalent to the vegetative cells, and is therefore diploid. These small cells may change to resting cells (cysts) directly. The ‘Small cell Type 2’ was homozygous at all analyzed loci, suggesting that these small cells are haploid and may be derived by meiosis. As fusion between small cells has previously been observed, the ‘Small cell Type 2’ may be the gamete of Chattonella. We present a construct of the full life cycle of Chattonella marina based on our own and previous results.     

Temperature explains global variation in biomass among humid old‐growth forests

Aim To develop and test a simple climate‐based ecophysiological model of above‐ground biomass – an approach that can be applied directly to predicting the effects of climate change on forest carbon stores. Location Humid lowland forests world‐wide. Methods We developed a new approach to modelling the aboveground biomass of old‐growth forest (AGB_max) based on the influences of temperature on gross primary productivity (GPP) and what we call total maintenance cost (TMC), which includes autotrophic respiration as well as leaf, stem and other plant construction required to maintain biomass. We parameterized the models with measured carbon fluxes and tested them by comparing predicted AGB_max with measured AGB for another 109 old‐growth sites. Results Our models explained 57% of the variation in GPP across 95 sites and 79% of the variation in TMC across 17 sites. According to the best‐fit models, the ratio of GPP to maintenance cost per unit biomass (MCB) peaks at 16.5 °C, indicating that this is the air temperature leading to the highest possible AGB_max when temperatures are constant. Seasonal temperature variation generally reduces predicted AGB_max, and thus maritime temperate climates are predicted to have the highest AGB_max. The shift in temperatures from temperate maritime to tropical climates increases MCB more than GPP, and thus decreases AGB_max. Overall, our model explains exactly 50% of the variation in AGB among humid lowland old‐growth forests. Main conclusions Temperature plays an important role in explaining global variation in biomass among humid lowland old‐growth forests, a role that can be understood in terms of the dual effects of temperature on GPP and TMC. Our simple model captures these influences, and could be an important tool for predicting the effects of climate change on forest carbon stores.     

Description and ecological traits of a new species of Pitydiplosis (Diptera: Cecidomyiidae) that induces leaf galls on Pueraria (Fabaceae) in East Asia,with a possible diversification scenario of intraspecific groups

A gall midge that induces thick lenticular galls on leaflets of Pueraria species (Fabaceae) in Japan, mainland China, Taiwan and South Korea is described as Pitydiplosis puerariae sp. nov. (Diptera: Cecidomyiidae). Tanaostigmodes puerariae (Hymenoptera: Tanaostigmatidae), described earlier from mainland China as an inducer of the lenticular gall, is regarded to be an inquiline. Pitydiplosis puerariae is distinguishable from the only known congener, the Nearctic Pitydiplosis packardi, by the male genitalia with entire aedeagus and with hypoproct that is as long as cerci and bilobed with a U‐shaped emargination. DNA sequencing data indicate the existence of three genetically different intraspecific groups: (i) “YNT‐montana group” induces galls on Pueraria montana on the Yaeyama Islands, Japan and in northern Taiwan; (ii) “CT‐montana group” on P. montana in central Taiwan; (iii) and “JCK‐lobata group” on Pueraria lobata in mainland China, South Korea and Japan north of Okinoerabu Island. A possible diversification scenario of the three groups is hypothesized based on DNA sequencing data and geohistorical information. A distribution gap of the gall midge on five islands between Tokunoshima and Ishigaki Islands, Japan was confirmed by intensive field surveys. Ecological traits and adult behavior of Pity. puerariae are also described. Its possibility as a potential biological control agent against P. lobata seems counter‐indicated.     

GENOTYPE‐BY‐TEMPERATURE INTERACTIONS MAY HELP TO MAINTAIN CLONAL DIVERSITY IN ASTERIONELLA FORMOSA (BACILLARIOPHYCEAE)

Marine and freshwater phytoplankton populations often show large clonal diversity, which is in disagreement with clonal selection of the most vigorous genotype(s). Temporal fluctuation in selection pressures in variable environments is a leading explanation for maintenance of such genetic diversity. To test the influence of temperature as a selection force in continually (seasonally) changing aquatic systems we carried out reaction norms experiments on co‐occurring clonal genotypes of a ubiquitous diatom species, Asterionella formosa Hassall, across an environmentally relevant range of temperatures. We report within population genetic diversity and extensive diversity in genotype‐specific reaction norms in growth rates and cell size traits. Our results showed genotype by environment interactions, indicating that no genotype could outgrow all others across all temperature environments. Subsequently, we constructed a model to simulate the relative proportion of each genotype in a hypothetical population based on genotype and temperature‐specific population growth rates. This model was run with different seasonal temperature patterns. Our modeling exercise showed a succession of two to several genotypes becoming numerically dominant depending on the underlying temperature pattern. The results suggest that (temperature) context dependent fitness may contribute to the maintenance of genetic diversity in isolated populations of clonally reproducing microorganisms in temporally variable environments.     

Genetic and geographical structure in grapevines from northwestern Spain

The grapevine germplasm bank from Estación de Viticultura e Enoloxía de Galicia contains 110 accessions collected from more than 100‐year‐old grapevines from northwestern Spain. We identified 60 different genotypes (among which ‘Pinot Noir’ and ‘Shyrah’ were included as references) with 32 polymorphic microsatellites (SSRs), 21 of which were unlinked SSRs and without null alleles, which were used to detect genetic structure. We found four reconstructed populations that were highly differentiated by analysis of molecular variance (18.3%): (i) western Galician group (‘Caíño Bravo’); (ii) eastern Galician group (‘Merenzao’); (iii) Castilian group (‘Garnacha’) and (iv) southern Spanish group (‘Moscatel’). The greatest genetic differentiation was found between the western Galician/eastern Galician groups and the southern Spanish/Castilian groups, with Fst > 0.13. Western and eastern Galician groups contained most of the ancient Galician cultivars (86%) and included ancestors from central Europe, such as ‘Pinot Noir’ and ‘Shyrah’ in the western Galician group and the introgressant ‘Merenzao’ (French ‘Trousseau’) in the eastern Galician group; the Castilian and southern Spain groups included traditional cultivars from central and southern Spanish and suggest a further introduction of those cultivars in northwestern plantations. Genetic structure corresponded with East‐to‐West geographical differentiation in the northern Iberian Peninsula, following the old path to Santiago de Compostela from France, with the southern Spanish and Castilian groups in the East (Castilian plateau and southern Spain), the eastern Galician group and the western Galician group in the West. Five new relationships were discovered: ‘Caíño Bravo’/‘Caíño Longo2’, ‘Albarín Tinto’/‘Torrontés1’, ‘Treixadura’/‘Treixadura Francesa’, ‘Moscatel’/‘Moscatel de Bago Miúdo’ and ‘Moscatel’/‘Moscatel de Hamburgo’, indicating that hybridisation and further selection by growers have been the origin of most of the genetic diversity found in northwestern Spain.     

Delayed development of the whitefly (Bemisia tabaci) and increased parasitism by Encarsia bimaculata in response to sublethal doses of piperonyl butoxide

Abstract Effects of sublethal piperonyl butoxide (PB) on parasitization of Bemisia tabaci (Gennadius ) (Hemiptera: Aleyrodidae) by Encarsia bimaculata Heraty et Polaszek (Hymenoptera: Aphelinidae) were evaluated both in cage and greenhouse experiments. When first, second and third instar B. tabaci nymphs were treated with PB, all but the first instar were significantly prolonged. Data indicated that sublethal PB could improve E. bimaculata parasitism rates without influencing parasitoid eclosion rates. Prolonged development increased rates of parasitism by E. bimaculata, from 17.6% to 24.7% in cages, presumably by increasing the duration of host exposure. Sublethal PB combined with E. bimaculata as an integrated approach to control B. tabaci was evaluated using life table parameters under greenhouse conditions. Indices of population trend (I) calculated from life tables were estimated at 4.6 for B. tabaci exposed to PB and parasitoids compared to 14.1 with parasitoids alone and 23.5 in untreated controls. The results showed that after PB was sprayed and parasitoids introduced, development of B. tabaci was delayed and the peak of each stage was postponed. The older nymphal stage had highest mortality, primarily due to mortality caused by parasitism by E. bimaculata.     

Comparing survival among species with imperfect detection using multilevel analysis of mark—recapture data: a case study on bats

For comparative demography studies, 2 prerequisites are usually needed: 1) using typical parameter values for species, 2) correctly accounting for the uncertainty in the species specific estimates. However, although within‐species variability may be essential, it is typically not considered in analytical procedures, resulting in parameter estimates that may not be representative of the species. Further, data are analysed in 2 steps, first separately for each species, then estimates are compared among species. Accounting for the uncertainty in the species specific estimates is then difficult. Here we propose the application of multilevel Bayesian models on mark—recapture (MR) data for comparative studies on survival probabilities that solves these problems. Our models account for within‐species variability in space and time in the form of random effects. Models reflecting different biological predictions related to the species’ ecology and life‐history traits may further be contrasted. To illustrate our approach, we used long‐term data from 5 temperate tree‐roosting bat species and compared their survival probabilities. Results suggest that species foraging in open space, high reproductive output and short longevity records have lower survival than species foraging at short distances, with low reproductive output and high longevity records. Multilevel models provided relatively precise estimates, away from the edges of the parameter space, even for species with low encounter rates and short study duration. This is particularly valuable for less studied taxa such as bats for which available data are often more sparse. Our approach can be easily extended to include additional groups or levels of interest and effects at the individual level (e.g. sex or age). Different hypotheses regarding differences or similarities in parameters among species can be tested through the application of different models. Overall, it offers a flexible tool to ecologists, and population and evolutionary biologists for comparative studies, explicitly accounting for multilevel structures often encountered in MR data.