The effect of the armored scale,Rhizaspidiotus donacis (Hemiptera: Diaspididae), on shoot growth of the invasive plant Arundo donax (Poaceae: Arundinoideae)

The effect of feeding by the armored scale, Rhizaspidiotus donacis (Leonardi, 1920) (Hemiptera: Diaspididae) on the growth of the plant Arundo donax L. (Poaceae) was evaluated under field conditions in its native range. The study was designed to evaluate the impact of R. donacis, a candidate agent for biological control of A. donax which is invasive in arid riparian ecosystems of the Southwestern USA and Mexico. The study was carried out at five A. donax sites in the Province of Alicante, Spain, differing in altitude and climate. At each site, 30 infested lateral shoots were selected and 15 were randomly treated monthly with imidacloprid insecticide. Shoot lengths were measured monthly over a 1-year period in a comparative growth analysis. Shoots infested with R. donacis had an over 2-fold reduced growth rate as compared to treated shoots. Growth of shoots varied by site, and the effect of R. donacis on growth was most pronounced in the late spring, when mature females produced first instar scale crawlers. The impact of R. donacis on A. donax growth under field conditions in the native range, combined with its narrow host specificity, indicate that R. donacis is a promising candidate for biological control of A. donax in North America and other areas invaded by this weed.     

Impact of the biological control agent Tetramesa romana (Hymenoptera: Eurytomidae) on Arundo donax (Poaceae: Arundinoideae) along the Rio Grande River in Texas

Five years post-release of the arundo gall wasp, Tetramesa romana, into the riparian habitats of the lower Rio Grande River, changes in the health of the invasive weed, Arundo donax, or giant reed, have been documented. These changes in plant attributes are fairly consistent along the study area of 558 river miles between Del Rio and Brownsville, TX, and support the hypothesis that the arundo wasp has had a significant impact as a biological control agent. Plant attributes were measured prior to release in 10 quadrats at each of 10 field sites in 2007, and measured again at the same undisturbed sites, 5 years after the release of T. romana, in 2014. Above ground biomass of A. donax decreased on average by 22% across the 10 sites. This decline in biomass was negatively correlated to increased total numbers of T. romana exit holes in main and lateral shoots per site in 2014 compared to 2007. Changes in biomass, live shoot density and shoot lengths, especially the positive effect of galling on main and lateral shoot mortality, appear to be leading to a consistent decline of A. donax. Economically, this reduction in A. donax biomass is estimated to be saving 4.4 million dollars per year in agricultural water. Additional impacts are expected as populations of the wasp increase and as other biological control agents such as the arundo scale, Rhizaspidiotus donacis, become more widespread.     

Microsatellite markers for the polygamous termite Nasutitermes corniger (Isoptera: Termitidae)

We developed eight highly variable microsatellite markers for the termite Nasutitermes corniger. Allele number per locus ranged from nine to 34, and expected heterozygosity from 0.45 to 0.94, in samples from seven sites in the former canal zone of Panama. The utility of these markers was assessed for five congeners varying in phylogenetic distance to N. corniger. The markers will be useful for fine‐scale examination of population and colony genetic structure in N. corniger and other closely related species.     

Evaluation of Spanish Arundo scale Rhizaspidiotus donacis (Hemiptera; Diaspididae) survival and fecundity on three new world genotypes of Arundo donax (Poaceae; Arundinoideae)

A pre-release evaluation of survival and fecundity of the arundo scale, Rhizaspidiotus donacis, was conducted on three invasive genotypes of the riparian weed, Arundo donax. The three A. donax genotypes were collected from Laredo, Austin and Balmorhea, TX, which represented the majority of the genotypic diversity found in Texas watersheds. Although R. donacis developed on all three genotypes of the plant, the Austin A. donax genotype, followed by the Laredo genotype, were the most suitable in terms of the size of first-generation immature and adult scale populations that developed after crawler release. Both the Laredo and Austin genotypes of A. donax are likely to be of Spanish origin and are close genetic matches with scale's original host plant genotype in Alicante, Spain. In comparison, survival was lowest on the phylogenetically distant genotype of A. donax from Balmorhea, TX. Although the population size of settled, immature second-generation scales varied in a manner similar to that of the first generation, the fecundity of isolated first-generation females was not significantly different across the three plant genotypes, suggesting that R. donacis is not a genotype specialist in terms of nutrient assimilation for reproduction. Rather, differences in genotype suitability affect rates of success of crawler settling. These results indicate that selection of scale genotype from the native range may have a moderate influence on the success of R. donacis and ultimately the biological control programme.     

Prevalence and genetic diversity of three bacterial endosymbionts (Wolbachia, Arsenophonus, and Rhizobiales) associated with the invasive yellow crazy ant (Anoplolepis gracilipes)

Invasive species carry pathogens, parasites and mutualistic microorganisms into their new range. We examined the prevalence and genetic diversity of three bacterial endosymbionts (Wolbachia, Arsenophonus, and Rhizobiales) in four Anoplolepis gracilipes (Smith) populations in the Pacific region, four populations from mainland Australia and one population from Christmas Island in the Indian Ocean. Wolbachia was found in eight of the nine sampling sites, with between 31.8 and 100% of ants infected. These infection rates are substantially higher than those previously observed for other invasive ants such as Linepithema humile and Solenopsis invicta. All sequences of Wolbachia were genetically identical. Arsenophonus was observed in five of the nine sampling sites, with infection rates ranging between 4.5 and 50.8%. Like Wolbachia, Arsenophonus can modify the sex-ratio of its hosts via male-killing. Arsenophonus was found to co-occur with Wolbachia in the same ants in five of the nine sampling sites. Rhizobiales is a clade of symbiotic bacteria mostly found in herbivorous ants. These bacteria help provide nitrogen to their hosts and were found in only three of the nine sampling sites with an infection rate of 1.6–11.8%. It also co-occurred with the other bacteria. There was no genetic variation in Arsenophonus and Rhizobiales samples, with the exception of a sequence from one Arsenophonus sample in Samoa that differed by a single base pair. These bacterial endosymbionts may contribute to the population variability in A. gracilipes and may be manipulated for the purpose of pest management.     

Analysis of copy-number variation,insertional polymorphism,and methylation status of the tiniest class I (TRIM) and class II (MITE) transposable element families in various rice strains

Transposable elements (TEs) dominate the genetic capacity of most eukaryotes, especially plants, where they may compose up to 90% of the genome. Many studies, both in plants and animals reported that in fact non-autonomous elements that have lost their protein-coding sequences and became miniature elements were highly associated with genes, and showed a high level of transpositional activity such as mPing family in rice. In this study, we have investigated in detail the copy number, insertional polymorphism and the methylation status of the tiniest LTR retrotransposon family, termed TRIM, in nine rice strains, in comparison with mPing. While TRIM showed similar copy numbers (average of 79 insertions) in all the nine rice strains, the copy number of mPing varied dramatically (ranging from 6 to 203 insertions) in the same strains. Site-specific PCR analysis revealed that ~58% of the TRIM elements have identical insertion sites among the nine rice strains, while none of the mPing elements (100% polymorphism) have identical insertion sites in the same strains. Finally, over 65% of the TRIM insertion sites were cytosine methylated in all nine rice strains, while the level of the methylated mPing insertion sites ranged between 43 and 81.5%. The findings of this study indicate that unlike mPing, TRIM is most probably a fossil TE family in rice. In addition, the data shows that there might be a strong correlation between TE methylation and copy number.     

Population dynamics ofHemisarcoptes coccophagus Meyer (Astigmata: Hemisarcoptidae) attacking three species of armored scale insects (Homoptera: Diaspididae)

The parasitic miteHemisarcoptes coccophagus Meyer (Astigmata: Hemisarcoptidae) feeds on armored scale insects (Homoptera: Diaspididae). Three host scales were studied: chaff scale (Parlatoria pergandii Comstock andP. cinerea Hadden) infesting citrus (grapefruit and orange) orchards, latania scale [Hemiberlesia lataniae (Signoret)] and olcander scale (Aspidiotus nerii Bouche) occurring on acacia (Acacia cyanophylla) branches and leaves. The overall dynamics of mite populations were similar on the different scale species, although the level of attack on each sampled diaspidid host was different. Rates of young mite stages were highly variable on all three hosts throughout the sampling period while adult rates were stable, constituting around 20% of all mites. No oviposition by mites occurred in mid-winter on any scale species, on any plants or parts, at all sampling sites. Of the three diaspidids, highest mite prevalence (parasitization rate) occurred on latania scale. Mite prevalence on oleander scale infesting mature leaves was higher than on young leaves.H. coccophagus apparently first attacks latania scale on branches, it then disperses to the same host inhabiting mature leaves, from there to co-occurring oleander scale and finally to oleander scale infesting young leaves. Mite prevalence on chaff scale was influenced by host plants and climatic regions: in the Negev it was higher than in the coastal plain, with scales on grapefruit being more heavily attacked at the former site but not on coastal plain. Our data suggest thatH. coccophagus prefers ovipositing scale females. The decreasing order of preference for other scale stages was: young females immature males, 2nd-instar nymphs females.     

Host range of the European,rhizome-stem feeding scale Rhizaspidiotus donacis (Hemiptera: Diaspididae), a candidate biological control agent for giant reed,Arundo donax (Poales: Poaceae) in North America

The armored scale Rhizaspidiotus donacis (Leornardi) was evaluated as a potential biological control agent of the invasive reed grass Arundo donax in North America. No-choice tests, native range field surveys and non-target host exposures were used to determine the fundamental host range of the scale collected from Caloma, Spain and Perpignan, France. Thirty-five species, including two genotypes of A. donax and seven ecotypes of Phragmites australis, along with closely related grasses, economic grasses and habitat associates were tested. In quarantine no-choice testing using releases of 200 crawlers per plant, normal development of R. donacis was observed on A. donax and A. formosana, with very limited survival to the adult stage on Spartina alterniflora and Leptochloa spp. In follow-up studies using 1000 crawlers per plant, 10 live adult females were found on Leptochloa virgata, and one adult female on Spartina alterniflora, but average adult female abundance per plant was (2580%) 26-times lower on L. virgata and over (39,090%) 100-times lower on S. alterniflora than on A. donax. Field surveys were conducted at five locations in Spain and France at which A. donax infested with R. donacis, co-occurred with two non-target species of concern and R. donacis was only found on A. donax. Six-month field host exposures in Spain using potted Leptochloa plants entwined with heavily infested A. donax confirmed that R. donacis is specific to Arundo under field conditions. Based on our results, the scale R. donacis appears to be specific to the genus Arundo and is unlikely to harm native or cultivated plants in the Americas.     

Distribution and habitat utilization in two atyid shrimps (Crustacea: Decapoda) in rivers of Nuku-Hiva Island (French Polynesia)

The distribution of Atyoida pilipes (Newport, 1847) and Caridina weberi De Man, 1892 was studied at two spatial scales on Nuku-Hiva Island (Marquesas, French Polynesia). At the stream reach scale, the two species were present at 40 and 39 sites, respectively, out of a total of 49 sites sampled. These two taxa represented more than half of the invertebrates collected at 9 sites. There was no difference in distribution between the species at the reach scale. However, clear differences appeared between the two species at the microhabitat scale. A. pilipes was more abundant in lotic habitats, even waterfalls, while C. weberi was associated with accumulations of leaves in lentic habitats. A. pilipes, particularly males, were tolerant to parameters such as water velocity, leaves, and the presence of algae and rocks. C. weberi had a more restricted altitudinal distribution and were scarce upstream from large waterfalls. These differences were linked to differences in climbing ability rather than the effect of chemical parameters, such as oxygen content. Our results suggest that little competition for space or food resources occurs between the two species. Both are feeding on small detritus particles, but through differing mechanisms and in differing habitats.     

Dynamics of parasitism in the organ-pipe wasp, Trypoxylon politurn: effects of spatial scale on parasitoid functional response

Abstract.

• 1 Life tables and rates of parasitism were tabulated from mud nests built by Trypoxylon politum (Hymenoptera: Sphecidae) at nine different nesting sites from Missouri and Mississippi.
• 2 Most developmental mortality occurred either during the first two instars of development, or during the inactive prepupal phase. The majority (76%) of deaths were caused by insect parasitoids and cleptoparasites. Levels of parasitism and survivorship varied among nesting sites, and among locations within the two sites surveyed at a fine spatial scale.
• 3 Total developmental mortality, K, was positively associated with the number of hosts (immature T.politum) per site. Within one of two sites sampled at a fine spatial scale, K was negatively associated with the local density of hosts. Levels of total parasitism were positively associated with host population size, and negatively associated with local host density within one of the two sites sampled at a fine spatial scale.
• 4 Levels of parasitism by Melittobia (Hymenoptera: Eulophidae) were positively associated with the number of hosts per site, but negatively associated with the local density of hosts within sites. Melittobia parasitism was also negatively associated with the local density of old nesting material within sites.
• 5 Parasitism by Melittobia was a function of both the numbers of nests per quadrat and the mean nest size per quadrat at one of the two sites surveyed at a fine scale. At the other site, parasitism by Melittobia was a function of mean nest size per quadrat.
• 6 The life cycle and nesting behaviour of T.politum, in relation to the regulation of its numbers, is discussed.

     

The importance of sampling scale in the assessment of intraspecific life-history differences in plains killifish,Fundulus zebrinus,populations (Pisces: Cyprinodontidae)

Synopsis The purpose of this study was to determine the effects of unpredictable environmental fluctuations on the demographic and genetic structure of Fundulus zebrinus populations. Collections of F. zebrinus were taken from three rivers in the Arkansas River basin: the Arkansas, Chikaskia, and Ninnescah. Fish were sampled from three sites on each river on nine collection dates throughout 1984 and 1985. Totals of 2100 fish and 6000 fish were included in electrophoretic and demographic analyses, respectively. The results of the study indicate that within a limited geographic region (i.e. within rivers) spatial differences and temporal changes in both demographic and genetic population characteristics occur frequently and are primarily stochastic. However, on a larger spatial scale (i.e. across rivers), general trends emerge for demographic and especially for genetic population characteristics. These results illustrate the importance of sampling scale for conclusions of life-history evolution in fluctuating environments. In addition, it was found that regulation of Fundulus zebrinus populations includes an important density-independent component. Stochastic demographic differences across space and changes through time and spatially and temporally heterogeneous allele frequencies, are both indicative of density-independent regulation. Variation in population parameters, both demographic and genetic, was observed between populations sampled from each river. These population differences were attributed to differences between the rivers themselves.     

Genetic relationship of the melon fly,Bactrocera cucurbitae (Diptera: Tephritidae) inferred from mitochondrial DNA

Abstract The melon fruit fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae), has been the subject of worldwide quarantine and management efforts due to its widespread agricultural impact and potential for rapid range expansion. From its presumed native distribution in India, this species has spread throughout the hot‐humid regions of the world. We provide information that reveals population structure, invasion history and population connectivity from 23 locations covering nine countries based on DNA sequences of the mitochondrial cytochrome oxidase I (COI) gene. Forty‐two polymorphic sites were described among 38 haplotypes. The most common haplotype, H1, was observed in 73% of the samples distributed among all populations. Highest genetic diversity was seen within populations, and no isolation‐by‐distance was detected. The western regions (Nepal, Bangladesh, Thailand, Burma and China‐west) showed higher haplotype diversity than eastern regions (China‐east). China‐Yunnan showed highest levels of genetic diversity in China. Haplotype diversity decreased with longitude from west to east. Together, these analyses suggest that B. cucurbitae has expanded from west to east within a limited geographic scale and recently invaded China through Yunnan Province.     

The role of augmentative releases of indigenous parasitoid Metaphycus lounsburyi (Hymenoptera: encyrtidae) in enhancing the biological control of Saissetia oleae (Homoptera: coccidae) on olive in Egypt

The Mediterranean black scale, Saissetia oleae (Olivier) (Homoptera: Coccidae) is the most important pest of olive in Egypt. Indigenous parasitoid Metaphycus lounsburyi (Howard) (Hymenoptera: Encyrtidae) from different localities in Egypt, were manipulated, reared and mass produced for classical biological control in Egypt, more than 193130 parasitoids were released. Several releases were made between May 1999 to April 2001. Increases of the parasitism from 17.4 to 42.0 and from 6.4 to 19.2 during the first year (1999–2000) and the second year (2000–2001), respectively in the Northern Coast. This parasitoid became established in some of the release sites in El-Arish and Matruh Governorates.     

Repeated DNA sequences inTriticum (Poaceae): Chromosomal mapping and its bearing on the evolution of B and G genomes

The somatic chromosomes ofTriticum turgicum var.durum cv. Langdon andT. dicoccoides (AABB tetraploids),T. timopheevii, andT. araraticum (AAGG tetraploids) were assayed for distribution patterns of a highly repeated 120bp DNA sequence by in situ hybridization. The repeated sequence appears to be an ancient sequence shared withSecale andAegilops. The distribution patterns of the chromosomes were compared to the patterns of the A and B genome chromosomes ofT. aestivum cv. Chinese Spring (AABBDD hexaploid).T. turgidum andT. dicoccoides were observed to have identical in situ hybridization patterns. In both species, nine chromosomes with a total of 21 sites of hybridization were observed. The pattern, with few exceptions, was identical to that of Chinese Spring.T. araraticum andT. timopheevii were observed to have different patterns. InT. araraticum, six chromosomes with 21 total hybridization sites are present while inT. timopheevii nine chromosomes with 19 total sites exist. Major differences in hybridization patterns were observed between the B and G genomes. The divergence of the tetraploid wheats in this study appears to have resulted in changes in location, not in amount, of the ancient repeated sequence.     

Patterns of shrub expansion in Alaskan arctic river corridors suggest phase transition

Recent increases in deciduous shrub cover are a primary focus of terrestrial Arctic research. This study examined the historic spatial patterns of shrub expansion on the North Slope of Alaska to determine the potential for a phase transition from tundra to shrubland. We examined the historic variability of landscape‐scale tall shrub expansion patterns on nine sites within river valleys in the Brooks Range and North Slope uplands (BRNS) between the 1950s and circa 2010 by calculating percent cover (PCTCOV), patch density (PADENS), patch size variability (CVSIZE), mean nearest neighbor distance (MEDIST) and the multi‐scale information fractal dimension (d_I) to assess spatial homogeneity for shrub cover. We also devised conceptual models for trends in these metrics before, during, and after a phase transition, and compared these to our results. By developing a regression equation between PCTCOV and d_I and using universal critical d_I values, we derived the PCTCOV required for a phase transition to occur. All nine sites exhibited increases in PCTCOV. Five of the nine sites exhibited an increase in PADENS, seven exhibited an increase in CVSIZE, and five exhibited a decrease in MEDIST. The d_I values for each site exceeded the requirements necessary for a phase transition. Although fine‐scale heterogeneity is still present, landscape‐scale patterns suggest our study areas are either currently in a state of phase transition from tundra to shrubland or are progressing towards spatial homogeneity for shrubland. Our results indicate that the shrub tundra in the river valleys of the north slope of Alaska has reached a tipping point. If climate trends observed in recent decades continue, the shrub tundra will continue towards homogeneity with regard to the cover of tall shrubs.     

Distribution of Plectidae (Nematoda: Araeolaimida) in pasture soils

Abstract

Across 88 sites 9 species were found, with Anaplectus granulosus at 56 sites, Plectus parietinus at 47, P. longicaudatus at 30, P. parvus at 15, P. cirratus and Wilsonema otophorum at 11, P. armatus and A. porosus at 4, and Tylocephalus auriculatus at 1 site. A key to Anaplectus males is given. For nine sites mean length of female A. granulosus is negatively correlated with mean annual air temperature. The most diverse fauna comprised six species in Kaitoke silt loam; it appears that faunal diversity increases with higher rainfall. Species apparently coexist through separation in size and time. Tylocephalus was only found in soils with a thermic soil temperature regime.     

Origin of the invasive Arundo donax (Poaceae): a trans-Asian expedition in herbaria

Background and Aims

The hypothesis of an ancient introduction, i.e. archaeophyte origin, is one of the most challenging questions in phylogeography. Arundo donax (Poaceae) is currently considered to be one of the worst invasive species globally, but it has also been widely utilzed by man across Eurasia for millennia. Despite a lack of phylogenetic data, recent literature has often speculated on its introduction to the Mediterranean region.

Methods

This study tests the hypothesis of its ancient introduction from Asia to the Mediterranean by using plastid DNA sequencing and morphometric analysis on 127 herbarium specimens collected across sub-tropical Eurasia. In addition, a bioclimatic species distribution model calibrated on 1221 Mediterranean localities was used to identify similar ecological niches in Asia.

Key Results

Despite analysis of several plastid DNA hypervariable sites and the identification of 13 haplotypes, A. donax was represented by a single haplotype from the Mediterranean to the Middle East. This haplotype is shared with invasive samples worldwide, and its nearest phylogenetic relatives are located in the Middle East. Morphometric data characterized this invasive clone by a robust morphotype distinguishable from all other Asian samples. The ecological niche modelling designated the southern Caspian Sea, southern Iran and the Indus Valley as the most suitable regions of origin in Asia for the invasive clone of A. donax.

Conclusions

Using an integrative approach, an ancient dispersion of this robust, polyploid and non-fruiting clone is hypothesized from the Middle East to the west, leading to its invasion throughout the Mediterranean Basin.     

Barbus xanthos,a new barbel from the Southern Aegean basin (Teleostei: Cyprinidae)

Barbus xanthos, a new species, is described from the Eşen, Dalaman, Tersakan and Büyük Menderes rivers in south-western Anatolia. It differs from other Barbus species in the adjacent basins by having 53–60 lateral line scales, a weakly ossified last unbranched dorsal-fin ray (about 33–50%), numerous small irregular-shaped black or dark-brown spots smaller than scales, often forming large, black or dark-brown blotches on back and flank in juveniles and adults, and a straight or slightly convex posterior dorsal-fin margin. B. xanthos differs from its most closely related congener, B. pergamonensis, by nine nucleotide substitution sites in the mitochondrial DNA cytochrome oxidase I barcode region.     

Millipede (Diplopoda) communities in an arboretum: Influence of tree species and soil properties

The paper deals with the influence of tree species on millipede communities (Diplopoda). The research was carried out in nine sites in the Borová hora arboretum (Zvolen town, Central Slovakia). Each studied site represents a monoculture of one of nine tree species: Betula pubescens Ehrh., Pinus sylvestris L., Larix decidua Mill., Carpinus betulus L., Abies alba Mill., Picea abies (L.) Karst., Alnus incana (L.) Moench, Populus nigra L., Ulmus laevis Pall. Millipedes were collected by pitfall trapping during vegetation periods in 2008-2011. In total, 1064 individuals of 17 species and 7 families were obtained. The results of research confirmed (i) an influence of tree species on the composition of millipede communities, (ii) a significant influence of soil nitrogen on the species richness and biodiversity, and (iii) an impact of soil pH on the species composition of these terrestrial invertebrate communities. In terms of total dynamic activity and species richness of millipedes, the most favourable conditions were revealed in the forest stands of Alnus incana, Populus nigra, Ulmus laevis and Carpinus betulus. On the contrary, the least favourable biotopes were (from both points of view) the forest stands of Betula pubescens and Larix decidua.     

Role of Coccophagus sp. in the suppression of the soft green scale Coccus viridis (Green) (Hompoptera: Coccidae) on sapota

The soft green scale Coccus viridis (Green) (Homoptera: Coccidae) has become a major pest of sapota, Manilkara achras (Mill.) Forberg in India. A field study was conducted on the population dynamics of soft green scale Coccus viridis (Green) for 2 years (2004–2006) on sapota at the Indian Institute of Horticultural Research (IIHR) farm, Bangalore, India. The population of green scale declined from 30.72 per leaf in May 2004 to 1.62 per leaf in March 2006. Two coccinellid predators Chilocorus nigrita (Fab.) and Cryptolaemus montrouzieri (Muls.) and one aphelinid parasitoid Coccophagus sp. were recorded on C. viridis. Both the predators played a minor role in the population fluctuation of C. viridis. The parasitoid Coccophagus sp. was the dominant natural enemy observed throughout the study recording a mean of 10.24–94.67% parasitism. A significant positive correlation of the scale population with minimum temperature (r=0.54) and negative relationship with the parasitism by Coccophagus sp. (r=0.81) was recorded. Multiple regression analysis revealed that 75.7% of the variation present in the green scale population could be predicted by abiotic factors and parasitism by Coccophagus sp. Further, step-wise regression procedure employed to arrive at a multiple regression model showed that about 65.60% of the scale population could be predicted by one factor namely, parasitism by Coccophagus sp. These results showed that parasitism by Coccophagus sp. played a major role in regulating the population of the soft green scale infesting sapota.