Contradictory effects of leaf rolls in a leaf-mining weevil.

Leaf rolls by herbivorous insects evolved in various lepidopteran groups, aphids, and some attelabid weevil species. Leaf rolls are known to have a positive effect on the survival of immature insects, protecting them from natural enemies such as birds, ants, predatory wasps, and parasitoids as well as environmental stress. On the other hand, leaf rolls are considered to have a negative effect on immature survival, attracting natural enemies because of their noticeability and subsequent learning or specialization. In this study, we directly tested the effects of leaf rolls using an attelabid species by comparing the fate of immature insects between artificial leaf rolls and unrolled leaves. The results showed the following positive effects of leaf rolls: avoidance of parasitism by eulophid wasps and avoidance of egg predation by unknown predators. On the other hand, a negative effect of leaf rolls was also detected, specifically and increase in mortality via leaf roll herbivory. This study indicated that leaf shelters are not only protective refuges but are also sometimes risky hiding places, although total survival rates increased in leaf shelters.

A global phylogeny of leafmining Ectoedemia moths (Lepidoptera: Nepticulidae): exploring host plant family shifts and allopatry as drivers of speciation.

BACKGROUND: Host association patterns in Ectoedemia (Lepidoptera: Nepticulidae) are also encountered in other insect groups with intimate plant relationships, including a high degree of monophagy, a preference for ecologically dominant plant families (e.g. Fagaceae, Rosaceae, Salicaceae, and Betulaceae) and a tendency for related insect species to feed on related host plant species. The evolutionary processes underlying these patterns are only partly understood, we therefore assessed the role of allopatry and host plant family shifts in speciation within Ectoedemia. METHODOLOGY: Six nuclear and mitochondrial DNA markers with a total aligned length of 3692 base pairs were used to infer phylogenetic relationships among 92 species belonging to the subgenus Ectoedemia of the genus Ectoedemia, representing a thorough taxon sampling with a global coverage. The results support monophyletic species groups that are congruent with published findings based on morphology. We used the obtained phylogeny to explore host plant family association and geographical distribution to investigate if host shifts and allopatry have been instrumental in the speciation of these leafmining insects. SIGNIFICANCE: We found that, even though most species within species groups commonly feed on plants from one family, shifts to a distantly related host family have occasionally occurred throughout the phylogeny and such shifts are most commonly observed towards Betulaceae. The largest radiations have occurred within species groups that feed on Fagaceae, Rosaceae, and Salicaceae. Most species are restricted to one of the seven global biogeographic regions, but within species groups representatives are commonly found in different biogeographic regions. Although we find general patterns with regard to host use and biogeography, there are differences between clades that suggest that different drivers of speciation, and perhaps drivers that we did not examine, have shaped diversity patterns in different clades.

Tree litter and forest understorey vegetation: a conceptual framework to understand the effects of tree litter on a perennial geophyte, Anemone nemorosa.

BACKGROUND AND AIMS: Litter is a key factor in structuring plant populations, through positive or negative interactions. The litter layer forms a mechanical barrier that is often strongly selective against individuals lacking hypocotyle plasticity. Litter composition also interacts with plant growth by providing beneficial nutrients or, inversely, by allowing harmful allelopathic leaching. As conspicuous litter fall accumulation is often observed under deciduous forests, interactions between tree litter and understorey plant populations are worthy of study. METHODS: In a 1-year ex-situ experiment, the effects of tree litter on the growth of Anemone nemorosa, a small perennial forest geophyte, were investigated. Three 'litter quantity' treatments were defined, representative of forest floor litter (199, 356·5 and 514 g m(-2)), which were crossed with five 'litter composition' treatments (Quercus petraea, Fagus sylvatica, Carpinus betulus, Q. petraea + F. sylvatica and Q. petraea + C. betulus), plus a no-litter control. Path analysis was then used to investigate the pathways linking litter characteristics and components of adult plant growth. KEY RESULTS: As expected, the heavier the litter, the longer the petiole; rhizome growth, however, was not depreciated by the litter-induced petiole lengthening. Both rhizome mass increment and number of initiated buds marginally increased with the amount of litter. Rhizome mass increment was in fact determined primarily by leaf area and leaf life span, neither of which was unequivocally correlated with any litter characteristics. However, the presence of litter significantly increased leafing success: following a late frost event, control rhizomes growing in the absence of litter experienced higher leaf mortality before leaf unfolding. CONCLUSIONS: The study questions the role of litter as a physical or chemical barrier to ground vegetation; to better understand this role, there is a need for ex-situ, longer-term experiments coupled with in-situ observations in the forest.

Control of overwintering filbertworm (Lepidoptera: Tortricidae) larvae with Steinernema carpocapsae.

Filbertworm, Cydia latiferreana (Walsingham) (Lepidoptera: Tortricidae), is a key insect pest associated with hazelnuts, Corylus avellana L. (Fagales: Betulaceae), in North America. This study investigated the feasibility of entomopathogenic nematodes as an alternative strategy for filbertworm control. Laboratory and field experiments were conducted between October 2007 and May 2008 in Benton County, OR, to evaluate the ability of the nematode Steinernema carpocapsae (Weiser) (Rhabditida: Steinernematidae) to infect filbertworm larvae and pupae. The susceptibility of larvae with and without hibernacula as well as pupae to S. carpocapsae was tested in laboratory bioassays using nematode concentrations between 40 and 200 infective juveniles (IJs) per cm2. Percentage of nematode infection was not significantly affected by the presence of hibernacula (infection range, 90-92%) compared with larvae without hibernacula (80-95%), or by pupal stage (50-75%) compared with larvae (65-75%). In additional field trials, the effect of nematode rate, water application rate, and orchard floor cover on nematode efficacy was determined in October 2007 and May/June 2008. Sentinel filbertworm larvae in plots with either bare soil or debris (leaves, twigs, husks, and blank nuts) were treated with S. carpocapsae at rates ranging from 40 to 150 IJs per cm2 applied in 75 or 190 ml/m2 water. Average filbertworm mortality ranged from 2 to 11% and from 50 to 78% in October and May, respectively. Larval mortality increased with increasing nematode concentration, but was not significantly affected by water application rate or orchard floor cover. Our experiments suggest that S. carpocapsae can play a role in the control of filbertworm larvae overwintering on the orchard floor.

[Taxonomy and evolution of the genus Pratylenchoides (Nematoda: Pratylenchidae)].

The amended diagnosis of the genus Pratylenchoides and list of its valid species with synonyms are given. All the efficient diagnostic characters are listed. Modern taxonomic standard for the description of Pratylenchoides species is proposed; it may be used also in taxonomic databases. Tabular and text keys for all species of the genus are given. Five following groups are considered within the genus Pratylenchoides. The group arenicola differs from other groups in the primitive adanal bursa type; the groups magnicauda, crenicauda, ritteri, and megalobatus differ from each other in the position of cardium along the body axis in relation to the pharyngeal gland nuclei, pharynx types are named according to the stages of its evolution from the primitive tylenchoid pharynx (cardium situated posteriorly) to the advanced hoplolaimoid one (cardium situated anteriorly). Diagnoses and species compositions of the groups are given. Basing on the matrix of species characters, the dendrogram has been generated for all species of Pratylenchoides and for all characters (UPGMA, distance, mean character difference, random, characters ordered). Taking in view that the PAUP software gives equal weights to all characters, including the most important ones which define the prognostic species groups, the separate dendrograms for each prognostic species group were generated using the same above mentioned tree parameters. On the base of the records of Pratylenchoides species the matrices of plant host ranges, geographic distribution, and preferred soil-climatic conditions were developed. The dendrograms of the faunal similarities were generated using these matrices, with conclusions on a possible origin and evolution of the genus. The genus evolved from the flood lands with swampy soils and prevalence of dicotyledons (herbaceous Lamiaceae and woody Salicaceae families) to the forest mainland communities with balanced humidity and predominance of herbaceous Poaceae and Fabaceae with woody Fagaceae, Betulaceae, and Oleaceae. The leading factor of the evolutional adaptation to soil-climatic conditions was the factor of humidity, but its significance gradually decreased with the host change to more advanced plant taxa adapted to the communities with more dry balanced humidity. The genus took its origin on the south shores of Laurasia in the Cainozoe. Later, when Hindistant and Arabian Peninsula joined with Laurasia creating the Himalayas barrier, the Pratylenchoides spp. distributed by two branches: the northern one moved into Central Asia, East Europe and North America, and the south branch came into Indo-Malaya, West Asia and the north of Africa. The remnants of the ancient species groups remain in West Europe and East Asia. In the North America the genus gave an origin to its sister genus Apratylenchoides, which spread to the south up to Antarctica; another advanced branch spread in the North America reaching Alaska.

Comparison of leaf life span, photosynthesis and defensive traits across seven species of deciduous broad-leaf tree seedlings.

BACKGROUND AND AIMS: Leaf life span, photosynthetic parameters and defensive traits were compared across seven species of deciduous broad-leaved tree seedlings native to northern Japan to test the "cost-benefit hypothesis" that more productive leaves are more susceptible to herbivore attack than less productive leaves. METHODS: Studies were made on three early successional species, Alnus hirsuta, Betula maximowicziana and Betula platyphylla "japonica"; one mid-successional species, Ostrya japonica, and three late-successional species, Carpinus cordata, Quercus mongolica 'grosseserrata' and Acer mono. Photosynthetic parameters and defensive traits (total phenolics, condensed tannin and toughness) of leaves were measured for each species, and a bioassay test with Eri silkmoth larvae (Samia cynthia ricini) was undertaken to evaluate differences between species in susceptibility to herbivore attack. KEY RESULTS: Early successional species have a shorter leaf life span (62-88 d) than late successional species (155-187 d). Leaf nitrogen content and light-saturated photosynthetic rate per unit leaf area (P(sat)-area) and per unit leaf mass (P(sat)-mass) were negatively correlated with leaf life span. The nitrogen content of early successional species was about 30 mg g(-1) and that of late successional species was about 16 mg g(-1). Leaf toughness and the C/N ratio were positively correlated with leaf life span, although condensed tannin was not correlated with leaf life span. The bioassay test showed that the number of days the larvae survived was negatively correlated with leaf life span. Average survival of larvae feeding on leaves of A. hirsuta, which has the shortest leaf life span, was 14.4 d and that of Q. mongolica, which has the longest leaf life span, was 6.6 d. The number of days of larval survival was positively correlated with leaf nitrogen content. There was no correlation between days of larval survival and defensive traits. CONCLUSIONS: These results indicate that species with a shorter leaf life span have higher photosynthetic productivity and are more susceptible to herbivore attack than species with a longer leaf life span. This supports the "cost-benefit hypothesis".