Aploneura Lentisci Research Articles

Root aphid (Aploneura lentisci) population size on perennial ryegrass is determined by drought and endophyte strain

Climate change is anticipated to lead to an increase in the occurrence and intensity of drought and fluctuations in insect cycles that will challenge modern pasture systems. Feeding by root aphids such as Aploneura lentisci Pass. can be a significant challenge to pastures. These below-ground living aphids are commonly found in New Zealand and Australia, feeding year-round on the roots of graminaceous plants such as perennial ryegrass (Lolium perenne L.). Some strains of the fungal endophyte Epichloë festucae var. lolii in perennial ryegrass can provide protection against root aphids and greater resilience under drought, contributing to higher persistency and growth than endophyte-free plants. However, the interaction between insect pressure and drought is not understood. This study examined the effect of drought on root aphid populations and plant performance in perennial ryegrass plants relative to endophyte status (±) and endophyte strain (AR37, NZCT) in a glasshouse experiment. Plants were cloned across the drought and well-watered treatments, and half of the plants were inoculated with root aphids, whilst half of the plants were treated with insecticide. Endophyte infection with strain NZCT and AR37 reduced root aphid numbers. Aphid populations were significantly higher in drought-stressed than in well-watered plants in both endophyte-infected and endophyte-free treatments. Under drought conditions, root aphid populations were increased 4-fold in NZCT and 8-fold in AR37 and endophyte-free plants in comparison with their well-watered counterparts. Root aphids reduced shoot dry weight by 16% in drought-exposed and 26% in well-watered plants in comparison with their insecticide-treated counterparts whilst reducing root biomass by 49%. Our results suggest that root aphids are likely able to exploit the higher availability of amino acids in the plant sap of drought-exposed plants. This study provides evidence that climate change-mediated impacts of root aphids could reduce production in perennial ryegrass-dominant pastures. However, field trials would be necessary to determine whether this effect is seen in situ, where numerous additional factors will be operating at the same time.

Differential transport of a guild of mutualistic root aphids by the ant Lasius flavus.

Mutually beneficial associations are widespread in ecological networks. They are typically assembled as multispecies guilds of symbionts that compete for one or more host species. The ant Lasius flavus engages in an intriguing and obligate mutualistic association with a community of aphids that are cultivated on plant roots in its nests. The ant displays a repertoire of amicable behaviors toward the aphids, including their transport. I examined whether L. flavus preferentially carried some of the root aphids. Using a no-choice and a choice experiment, I comparatively analyzed the transport rate of 5 obligate and one loosely associated species back to the ant nest and used the transport rate of the ant larvae as a reference. All associated root aphids were carried back to the nest, but in a clear preferential hierarchy. Geoica utricularia, Forda Formicaria, and Trama rara were rapidly transported, but slower than the own larvae. Tetraneura ulmi and Geoica setulosa were collected at a moderate rate and the loosely associated Aploneura lentisci was slowly retrieved. In contrast, different species of unassociated aphids were not transported and even provoked aggressive behavior in L. flavus. This study revealed that co-occurring symbionts may induce different degrees of host attraction, which ultimately may affect the coexistence and assembly of ant-symbiont communities.

Costs and benefits of hosting <i>Epichloë</i> endophytes: a comparison of three haplotypes in <i>Lolium perenne</i> with contrasting effects on two herbivores

The symbiotic relationship between Lolium perenne and Epichloe festucae var. lolii, a fungal endophyte that lives asymptomatically in its above-ground parts, benefits both the host and fungus. In an outdoor container experiment, the effects of three distinct endophyte haplotypes (AR1, AR37 and CT) on natural infestations of a root aphid, Aploneura lentisci and a mealybug Phenococcus graminicola were compared with an endophyte-free (Nil) control. Populations of these insects were suppressed in a genetically identical set of plants treated with insecticide. Over 18 months, foliar and root growth, tiller numbers and plant mortality were compared between the different endophyte treatments and between insecticide-treated and untreated plants. Hyphal densities were recorded once during the trial. Untreated plants infected with AR37 had the lowest populations of A. lentisci and P. graminicola, and the highest root and foliar growth compared with other treatments. Growth parameters of untreated plants infected with CT often exceeded that of AR1 and Nil due to low infestations of P. graminicola and lower populations of A. lentisci. Growth of Nil, AR1 and CT plants were higher in insecticide-treated than in corresponding untreated plants but was unaffected in AR37. Untreated Nil and AR1 plants had a lower survival than AR37 and CT plants. Cumulative root outgrowth for treated AR37 plants was significantly lower than for treated AR1 on three sampling occasions. These Epichloe haplotypes are primarily mutualists, although there are circumstances when they may be disadvantageous to their host. Opposing outcomes likely originate in the ecosystems in which associations evolved.

A root aphid Aploneura lentisci is affected by Epichloë endophyte strain and impacts perennial ryegrass growth in the field

The aphid Aploneura lentisci is widespread in Australia and New Zealand, living all year round on roots of its secondary grass hosts. The fungal endophyte (Epichloë festucae var. lolii), strain AR37 in Lolium perenne is known to greatly reduce populations and was a likely reason for the superior growth and persistence of this association previously observed in the field. Aphid populations were quantified in a field trial near Ballarat, comparing yields of perennial ryegrass infected with eight different endophyte strains and an endophyte-free (Nil) control in a common ryegrass background (Grasslands Samson (G. Samson)). AR37 and another endophyte strain, AR5, had significantly fewer aphids than all other endophytes. These differences were significantly related to yield increases taken before and after sampling that persisted until the end of the trial. In a pot trial comparing commercially available ryegrass-endophyte combinations with equivalent Nil controls, aphid numbers were lower on G. Samson AR37 and Banquet II with AR5 (Endo®5) than on all other cultivar-endophyte combinations. Compared with Nil controls, the common toxic strain in G. Samson, and two strains in Trojan also reduced aphid numbers. The AR5 endophyte produces the alkaloid ergovaline but high concentrations of this in roots of potted plants could not account for differences in root aphid numbers. Root concentrations of epoxyjanthitrems, the only known alkaloids produced by AR37, were low and unlikely to be the cause of resistance to A. lentisci.

DIVERSITY AND ABUNDANCE OF LANDING APHIDS IN TWO AREAS OF SEED POTATO PRODUCTION IN TUNISIA; RELATIVE TO THE INCIDENCE OF POTATO VIRUSES

Aphid flight activities were monitored in 2015 in two areas of seed potato production in Tunisia. Yellow water traps were used to investigate the diversity of aphidofauna and the incidence of aphids involved in potato virus transmission. A total of 9966 specimens belonged to 73 taxa were captured. The cumulative abundance recorded in Douala (first site) was much higher than in El Ogla (second site) (8768 vs 1189 specimens). The most preponderant species in Douala were Aphis spiraecola Patch (66.1%) and Aphis spp. group (13.5%). In El Ogla Rhopalosiphum padi (L.) comprised 58.9% of total catches, followed by Acyrthosiphon pisum (Harris) (12%) and Aploneura lentisci (Passerini) (10.4%). The highest values of diversity indices were recorded on April 23 th [Shannon-Wiener index (H’)=2.58; Simpson index (1-D)=0.88] in Douala and on May 12th (H’=1.70; 1-D=0.75) in El Ogla. The detection of viral infections by DAS-ELISA determined the predominance of Potato virus Y amongst five main potato viruses tested. Overall Chi-square analysis determined significant differences crossing all areas of seed and ware potatoes and season crops. The highest incidence of viruses was recorded in Douala (18.5%) while El Ogla was under the threshold value (4%). This might be attributed to the occurrence of aphids in early season known previously to be efficient vectors of PVY and to the characteristics of area including climatic conditions, altitude and landscape structure. These results provide new evidence for El Ogla as ideal site to produce healthy tubers while conversely Douala is favourable for the propagation of vectors and viruses.

Novel bioassay to assess antibiotic effects of fungal endophytes on aphids.

Perennial ryegrass is an important feed base for the dairy and livestock industries around the world. It is often infected with mutualistic fungal endophytes that confer protection to the plant against biotic and abiotic stresses. Bioassays that test their antibiotic effect on invertebrates are varied and range from excised leaves to whole plants. The aim of this study was to design and validate a "high-throughput" in-planta bioassay using 7-day-old seedlings confined in small cups, allowing for rapid assessments of aphid life history to be made while maintaining high replication and treatment numbers. Antibiosis was evaluated on the foliar and the root aphid species; Diuraphis noxia (Mordvilko) and Aploneura lentisci (Passerini) feeding on a range of perennial ryegrass-Epichloë festucae var. Lolii endophyte symbiota. As expected, both D. noxia and A. lentisci reared on endophyte-infected plants showed negatively affected life history traits by comparison to non-infected plants. Both species exhibited the highest mortality at the nymphal stage with an average total mortality across all endophyte treatments of 91% and 89% for D. noxia and A. lentisci respectively. Fecundity decreased significantly on all endophyte treatments with an average total reduction of 18% and 16% for D. noxia and A. lentisci respectively by comparison to non-infected plants. Overall, the bioassay proved to be a rapid method of evaluating the insecticidal activity of perennial ryegrass-endophyte symbiota on aphids (nymph mortality could be assessed in as little as 24 and 48 hours for D. noxia and A. lentisci respectively). This rapid and simple approach can be used to benchmark novel grass-endophyte symbiota on a range of aphid species that feed on leaves of plants, however we would caution that it may not be suitable for the assessment of root-feeding aphids, as this species exhibited relatively high mortality on the control as well.

Aploneura lentisci (Homoptera: Aphididae) and Its Interactions with Fungal Endophytes in Perennial Ryegrass (Lolium perenne).

Aploneura lentisci Pass. is endemic to the Mediterranean region where it is holocyclic, forming galls on its primary host, Pistacia lentiscus and alternating over a 2-year period between Pistacia and secondary hosts, principally species of Gramineae. This aphid is widely distributed in Australia and New Zealand on the roots of the common forage grasses, ryegrass (Lolium spp.) and tall fescue (Schedonorus phoenix) where it exists as permanent, anholocyclic, parthenogenetic populations. Previous studies have indicated that infestations of A. lentisci significantly reduce plant growth and may account for differences in field performance of Lolium perenne infected with different strains of the fungal endophyte Epichloë festucae var. lolii. These obligate biotrophs protect their host grasses from herbivory via the production of alkaloids. To confirm the hypothesis that growth of L. perenne is associated with the effect of different endophyte strains on aphid populations, herbage and root growth were measured over time in two pot trials that compared three fungal endophyte strains with an endophyte-free control. In both pot trials, aphid numbers were lowest on plants infected with endophyte strain AR37 at all sampling times. In plants infected with a common toxic strain naturalized in New Zealand, aphid numbers overall were lower than on uninfected plants or those infected with strain AR1, but numbers did not always differ significantly from these treatments. Populations on AR1-infected plants were occasionally significantly higher than those on endophyte-free. Cumulative foliar growth was reduced in AR1 and Nil treatments relative to AR37 in association with population differences of A. lentisci in both trials and root dry weight was reduced in one trial. In four Petri dish experiments survival of A. lentisci on plants infected with AR37 declined to low levels after an initial phase of up to 19 days during which time aphids fed and populations were similar to those on plants without endophyte. Aphids on AR37-infected plants became uncoordinated in their movement and developed tremors before dying suggesting a neurotoxin was responsible for their mortality. Results support the hypothesis that differences in A. lentisci populations due to endophyte infection status and strain affects plant growth.

Impact of novel endophytes in perennial ryegrass on herbage production and insect pests from pastures under dairy cow grazing in northern New Zealand

AbstractPerennial ryegrass (Lolium perenne L.) infected with a novel endophyte (AR37 or AR1), Wild‐type endophyte or no endophyte (Nil) was sown with white clover (Trifolium repens L.) in autumn 2005. The pastures were rotationally grazed by dairy cows from 2005–2009. Annual dry matter (DM) yield did not differ but AR37 pastures had a higher ryegrass tiller density, especially after the 2008 summer drought (+130%), and less white clover than did AR1 pastures. Concentrations of alkaloids produced by the Wild‐type association (lolitrem B, ergovaline) followed the same seasonal trends as did the AR37 alkaloids (epoxy‐janthitrems) but summer drought reduced concentrations of lolitrem B and epoxy‐janthitrems to less than half the mid‐summer (February) peak concentrations in the other years. Insect pests were monitored annually between 2006 and 2009. Tiller damage by Argentine stem weevil (Listronotus bonariensis (Kuschel)) was significantly reduced by all endophyte treatments. African black beetle (Heteronychus arator (F.)) populations in soil samples increased during the experiment with Nil > AR1 > Wild‐type = AR37. Root aphid (Aploneura lentisci (Pass.)) infestations followed the pattern AR1 > Nil > Wild‐type = AR37. A lower pest pressure from all insect pests in AR37 pastures is likely to have contributed to this treatment having the highest ryegrass tiller densities.

Effects of wild-type, AR1 and AR37 endophyte-infected perennial ryegrass on dairy production in Victoria, Australia

A 3-year experiment compared the effects of wild-type ryegrass endophyte and two novel endophytes on milk production in dairy cattle. On three 9.9-ha farmlets in West Gippsland, Victoria, pasture swards were established that were dominant in perennial ryegrass (Lolium perenne) infected with either wild-type, AR1 or AR37 endophytes. Each farmlet was stocked with 25 spring-calving Holstein–Friesian cows, which rotationally grazed nine paddocks within their farmlet during three lactations over 3 years. The three endophytes are known to produce different alkaloids, with wild-type producing ergot alkaloids, lolitrems and peramine, AR1 producing peramine and AR37 producing epoxy-janthitrems. These alkaloids were present in fresh pasture as well as hay and silage made from that pasture. Grazed pasture comprised 53% of estimated annual DM intake. The proportion was least from December to March when the daily ration of 2 kg DM/cow.day cereal grain was increased to 6 kg/day and forage supplements were fed consisting of purchased lucerne (Medicago sativa) hay and pasture silage grown on the farmlets. There were no differences in pasture accumulation rates or nutritive characteristics of ryegrass pastures on the three farmlets and no differences in the production of milk, fat or protein by cows grazing pasture infected with the three endophytes. Ryegrass staggers was only observed in four cows consuming the wild-type-infected ryegrass in the first year when the highest concentrations of lolitrem B were recorded in pasture. Soil samples showed lower numbers of root aphids (Aploneura lentisci), mealybugs (Pseudococcidae) and pasture tunnel moths (Philobota spp.) beneath ryegrass infected with the AR37 endophyte compared with the other two endophytes. Numbers of redheaded (Adoryphorus couloni) and blackheaded (Aphodius tasmaniae) cockchafers did not differ between treatments. Under dairy management and supplementary feeding regimes common to south-eastern Australia, the novel endophytes AR1 and AR37 had no effect on the milk production compared with the wild-type endophyte, and did not cause ryegrass staggers.

Phylogeography and gene diversity of the gall-forming aphid <i>Aploneura lentisci</i> in the Mediterranean basin

Pistacia lentiscus L. (Anacardiaceae) is a common shrub in the Mediterranean vegetation. Throughout its distribution area, this species is the obligate host of the kidney-shaped gall-forming aphid Aploneura lentisci (Homoptera: Fordinae). Despite the wide distribution of Pistacia lentiscus in diverse habitats along a climatic gradient in Israel, our previous study did not reveal any pattern of ecologically related genetic differentiation. Here we examined changes in gall density and genetic diversity of the gall-forming aphid A. lentisci along its distribution gradient in Israel, in the neighboring island of Cyprus, and in Tunisia, North Africa. Gall density and mass differed significantly among the Israeli populations and were positively correlated with annual precipitation and plants' annual growth. Gene diversity of A. lentisci was very low in all populations and, as with its host plant, the genetic similarity was high within and among the Israeli populations and between the Israeli and Cyprian populations. To conclude, we found no evidence for any gene flow barrier and genetic differentiation among the aphid populations.

Molecular phylogeny of Iberian Fordini (Aphididae: Eriosomatinae): implications for the taxonomy of genera Forda and Paracletus

Abstract Mediterranean representatives of the galling aphid tribe Fordini (Hemiptera: Aphididae: Eriosomatinae) are usually grouped under the subtribe term Fordina. Aphids within Fordina display two‐year life cycles, alternating between Pistacia shrubs, where they induce conspicuous galls, and roots of Poaceae species. The high number of morphs present in a given species, the lack of knowledge of the complete cycle in some species, and the similarity between homologous morphs observed in different species pose many taxonomic problems in this group. We present results of a survey to elucidate the phylogenetic relationships among Fordini species present in the Iberian Peninsula and the Canary Islands. Sequences from the nuclear long‐wavelength opsin (LWO) and translation elongation factor 1α (EF‐1α) genes and from a region of the mitochondrial DNA containing the genes encoding the subunits six and eight of the F‐ATPase were used to infer relationships among 10 Fordina species, namely Smynthurodes betae, Aploneura lentisci, Baizongia pistaciae, two Geoica species (G. utricularia and G. setulosa), three species of Forda and two of Paracletus. Relationships between and within representatives of the genera Forda and Paracletus, both exemplifying taxonomic and ecological problems, were investigated in greater depth through extensive sampling and morphometric analysis. A total of eight, six and six samples from F. formicaria, F. marginata and F. riccobonii, respectively, were included in the survey, along with 40 and 4 samples classified initially as P. cimiciformis and P. donisthorpei, respectively. Our results are relevant to current studies on the evolution of host selection by aphids and on the evolution of gall morphology. Our phylogeny suggests that the group can be divided into two main clades. One clade is composed of aphids inducing small, low‐capacity galls on either P. atlantica or P. terebinthus (Smynthurodes betae and genera Forda and Paracletus). The second clade is composed of species inducing larger galls on P. lentiscus and P. terebinthus (Aploneura lentisci, Baizongia pistaciae and Geoica species). Our results suggest that revision of diagnostic characters used in the taxonomy of Paracletus is needed, and suggest Forda rotunda as a new synonym of Paracletus cimiciformissyn.n.

Agronomic performance of AR37-infected ryegrass in northern New Zealand

The agronomic merits of a perennial ryegrass (Lolium perenne) cultivar infected with a new endophyte (Neotyphodium lolii), AR37, were compared with the same cultivar infected with currently available endophytes (AR1, Standard) at two sites in northern New Zealand for at least 3 years. AR37-infected ryegrass was the highest yielding treatment at both sites (11 080 kg DM/ ha/yr) producing more dry matter than either AR1 or Standard-infected ryegrass which yielded similar amounts (8870 kg DM/ha/yr). Yield advantages of AR37-infected ryegrass were greater at Kerikeri (36%) than Hamilton (17%), with differences increasing over successive years at both sites. At Hamilton, tiller populations were lowest in AR37-infected ryegrass in Year 2, and lowest in AR1- infected ryegrass 3 and 5 years after sowing. At both sites AR37-infected ryegrass had the lowest infestation scores for root aphid. At Hamilton in Year 4, more damage by African black beetle larvae occurred to AR1-infected plants than to AR37 and Standard-infected plants. These pests are likely to have contributed to the differences in agronomic performance observed. These agronomic results suggest AR37-infected ryegrass cultivars will be a useful choice for farmers in northern New Zealand. Keywords: endophyte, Neotyphodium lolii, perennial ryegrass, Lolium perenne, dry matter yields, plant persistence, root aphid, Aploneura lentisci, African black beetle, Heteronychus arator

Reductions in root aphid populations by non-toxic endophyte strains in tall fescue

In two separate pot trials, tall fescue plants infected with the endophyte strain AR542, which is non-toxic to livestock, were shown to have lower numbers of root aphid per plant compared with uninfected plants, but more aphids than plants infected with other non-toxic endophytes (AR502, AR510 and AR514). These differences were not always significant when aphid numbers per gram of root were analysed. A Petri dish trial investigated the mechanism of resistance. Aphid survival was lower on endophyte-free fescue than on AR514- and AR542-infected fescue. Compared with endophyte-free, fewer aphids on roots of AR514- and AR542-infected tall fescue showed signs of feeding, as measured by production of wax and honey dew, and more were mobile on and around roots. Keywords: Aploneura lentisci, Festuca arundinacea, Neotyphodium

Interactions between host plant genotype and Neotyphodium fungal endophytes affects insects

Neotyphodium endophytes usually confer resistance on their host grasses to insect attack, but can also occasionally increase host plant susceptibility to particular insects. In either case host plant genotype interaction with the endophyte appears to play a role in determining the strength of the interactions between the insect and its host. An example of this is the relationship between the root aphid, Aploneura lentisci and perennial ryegrass infected with different strains of endophyte. Aphid numbers on individual ryegrass plants infected with the Wild-type endophyte are generally similar to, or less than, those on endophyte-free (Nil) ryegrass whereas populations on plants infected with the AR1 endophyte are significantly higher. By analysing for differences between individual plants using data from five different samplings, significant differences in both the total number of root aphid per plant and aphid loading (number/g of root) were found among 20 plants infected with either the Wild-type or AR1 (P

Occurrence and impact of pasture mealybug (Balanococcus poae) and root aphid (Aploneura lentisci) on ryegrass (Lolium spp.) with and without infection by Neotyphodium fungal endophytes

Pasture mealybug (Balanococcuspoae) was found infesting two field trials evaluating the performance of selected strains of the endophyte Neotyphodium lolii in ryegrass (Lolium spp.) in Canterbury, New Zealand. Deterioration of endo‐phyte‐free plots relative to endophyte‐infected plots had been observed. In Trial A, pasture mealybug were sampled in plots of the perennial ryegrass cultivar ‘Grasslands Nui’, without endophyte (nil), or infected with the wild‐type endophyte, or the selected strains, AR1 and AR37. In Trial B, mealybug numbers on six ryegrass cultivars infected with AR1 or wild‐type were compared with those on the same cultivars without endophyte. In sampling these trials, the presence of a root aphid, Aploneura lentisci, was also noted. Populations of mealybug in both trials were similar on all endophyte‐infected treatments and significantly lower than populations on nil treatments. Neither AR1 nor wild‐type appeared to reduce root aphid numbers, while AR37 may have had some effect. The amount of dead grass was significantly greater in nil than in endophyte‐infected plots in Trial A, and yield of ryegrass was correlated with numbers of mealybug and root aphid present. Pasture productivity in nil treatments had recovered by spring, in the year of the outbreak. The presence of endophyte, strain of endophyte and cultivar were all significant factors affecting both total dry matter and green yield in Trial B. Pasture mealybug accounted for 55% of the variation in a decline in growth rate that occurred in this trial over the summer‐autumn periods between 2000 and 2001, particularly in the nil treatments. Two years after the outbreak there was 25% less ryegrass and persistently lower pasture yields in nil plots. We conclude that pasture mealybug are capable of inflicting severe damage to endophyte‐free ryegrass in Canterbury, particularly during dry summer‐autumn periods.

Differential colonization of host trees by galling aphids: Selection of hosts or selection by hosts?

Summary The pattern of adaptive diversification of galling aphids (Pemphigidae: Fordinae) on Pistacia (Anacardiaceae) is different from other gall-inducing insects. The Fordinae are host-specific, and radiated mainly by using different sites on one plant organ. Other gallers, including other galling aphids (Pemphiginae), share hosts and attack different plant organs. Species richness is very different among the three Pistacia hosts of the Fordinae in Israel. Pistacia palaestina and Pistacia atlantica each have 6–9 host-specific galling aphids. In contrast, P. lentiscus is colonized by only one species, Aploneura lentisci, throughout the Mediterranean and Middle-Eastern distribution of the host tree. Attraction to specific volatiles emitted by the leaves, or host-tree apparency, are unlikely to be effective mechanisms of selection of hosts in the Fordinae. The pattern is more likely due to selection by the hosts. Different response of the plant tissues to stimulation by fundatrices of different aphid species is possible. The presence of resin in the phloem of Pistacia may require special adaptation of the phloem-feeding Fordinae. P. lentiscus in particular produces commercially exploitable quantities of resin. A. lentisci may have evolved a unique mechanism to exploit this host. Several host shifts are suggested by the phylogeny of the Fordinae. None of these shifts involved P. lentiscus. The difference in species richness between hosts may have been conserved phylogenetically.

Soil biota associated with endophyteinfected tall fescue in the field

Invertebrates present in soil samples taken from plots of tall fescue (Festuca arundinacea) infected with two nontoxic strains of Neotyphodium endophyte (AR501 and AR542) at Aorangi near Palmerston North and one strain (AR501) at Lincoln in Canterbury together with endophytefree controls at both sites were determined in autumn 2002 Roots taken from these samples were stained and checked for the presence of arbuscular mycorrhiza At Lincoln numbers of root aphid (Aploneura lentisci) associated with plants infected with AR501 were significantly less than those on endophytefree plants while grass grub numbers (Costelytra zealandica) did not differ between treatments Beneficial invertebrates Collembola mites and earthworms were not affected by endophyte at either site and neither was colonisation of roots by mycorrhiza

The effects of slope orientation on plant growth, developmental instability and susceptibility to herbivores

South-facing slopes (SFS) may receive six times higher solar radiation than north-facing slopes (NFS). Although located only a few hundred meters apart, the microclimatic conditions on the slopes vary dramatically, affecting the biology of organisms at all levels. This study was conducted on both slopes of three canyons, where we examined leaf traits of Pistacia lentiscus L. and characterized the populations of its specific herbivore—the gall-forming aphid Aploneura lentisci Pass. Both a larger leaf size and lower gall density were found on NFS. However, gall size and leaf symmetry were not affected by slope. The unique biology of the aphids may explain their higher density on the SFS. Gall formers usually prefer and perform better on large plant organs (leaves), in accordance with the plant vigour hypothesis. Our results demonstrate that larger shaded leaves are an exception.

The effects of host‐plant properties on gall density, gall weight and clone size in the aphid Aploneura lentisci (Pass.) (Aphididae: Fordinae) in Israel

SummarySamples of shoots of Pistacia lentiscus carrying galls of the aphid, Aploneura lentisci, were collected at three localities in Israel.Shoots growing near pruning scars carried more galls than elsewhere on the plant, but these galls weighed less and contained fewer aphids (smaller clones). The proportion of empty galls increased with gall density. Crowding of galls at such sites may be due to the early burst of buds at the time of aphid emergence from the overwintering eggs, and not to active search for preferred sites.Shoots bearing larger numbers of leaves carried heavier galls, which contained larger aphid clones. The position of the galled leaf on the shoot had no effect on gall weight nor on clone size.The physiological condition of the plant may be an important environmental (ecological) factor affecting the variation in clone‐size and in aphid morphology among galls.

Aphid trapping in Victoria. I. The seasonal occurrence of aphids in three localities and a comparision of two trapping methods

Information about the seasonal occurrence and peaks of activity of winged aphid species was obtained by trapping during a period of 15 months at three locations within 45 miles of Melbourne. Most species were caught in greatest numbers during either the spring or the autumn. Species such as Myzus persicae (Sulz.) and Brevicoryne brassicae (L.) were caught throughout the year. Cavariella aegopodii (Scop.) was trapped only in cool weather, while Aploneura lentisci (Pass.) was caught only in warm weather. Water-filled yellow trays were very efficient for trapping many species, but a wind-vane sticky trap caught more of some species, including the grass-feeding aphids, than did the yellow tray.