Behavioural responses of the vine weevil, Otiorhynchus sulcatus, to semiochemicals from conspecifics, Otiorhynchus salicicola, and host plants

The vine weevil Otiorhynchus sulcatus is a parthenogenetic reproducing species which forages for suitable host plants at night, but is found congregated in dark places during the day. Frass of this weevil species is suspected to contain attractive compounds that are host‐plant related. Using a still‐air olfactometer, we tested adult vine weevils at night for their behavioural response to odours from conspecifics, feeding on a mixture of spindle tree (Euonymus fortunei) and yew (Taxus baccata), and to a sexually reproducing related species (Otiorhynchus salicicola), feeding on a mixture of ivy (Hedera helix) and cherry laurel (Prunus laurocerasus). Their attraction to conspecifics and O. salicicola appeared to be related to frass production. Freshly collected frass from O. sulcatus and from O. salicicola males and females was attractive. Prunus laurocerasus and H. helix have not been observed to be hosts of the vine weevil in the field. However, our tests showed that the vine weevil was attracted to mechanically damaged leaves of both plant species, whereas undamaged leaves were not attractive. Only undamaged young unfolding leaves of H. helix were also attractive. The attraction to odours from mechanically damaged host and non‐host plants suggested the involvement of compounds that are commonly found in many plant species. The involvement of plant compounds and/or aggregation pheromones in attraction to frass of the vine weevil and frass of the related weevil species O. salicicola is discussed.     

Palynological and chemical volatile components of typically autumnal honeys of the western Mediterranean

Measurements and observations of pollen grains of varying structure before and after dehiscence of the anther sac illustrate large magnitudes of harmomegathic changes in volume and shape. Such changes are compared for colpate, porate, and colporate grains, and it is suggested that the nature of the harmomegathal action may serve to distinguish colpi or furrows from pores. Consideration of the requirement to allow harmomegathy while preventing wall collapse may provide at least partial explanation for evolution of the internal structure and external sculpturing of pollen grain walls.     

Function of leaf hamamelitol as a compatible solute during water stress treatment of Hedera helix L.

Hamamelitol is an unusual branched-chain sugar alcohol previously suggested to function as a leaf compatible solute. In this study, we have examined the leaf metabolism and intracelluiar compartmentalization of hamamelitol and other soluble sugars during long-term water stress treatment of Hedera helix (English ivy). Total leaf hamamelitol content was relatively low in greenhouse control plants, but increased 2-fold during water stress treatment to levels approaching those observed in field-grown plants (6–7 μmol g^?1 fresh weight). Using density gradient fractionation with non-aqueous solvents, we showed that hamamelitol occurs primarily in the cytoplasm and vacuoles of leaf mesophyll cells. During water stress treatment most of the increase in leaf hamamelitol occurred in the mesophyll cytoplasm, compensating osmotically for a decrease in cytoplasmic sucrose concentration. The maximum concentration of cytoplasmic hamamelitol was 155 mol m^?3 and occurred in field-grown plants. Labelling experiments showed that hamamelitol is slowly synthesized from ¹⁴CO₂ in leaves of H. helix, but is very long-lived (estimated t_1/2 of 4 years). Together, these data indicate that hamamelitol probably functions during long-term stress conditions as an osmotically active, compatible solute in plant leaves. We suggest that the signal for enhanced accumulation of hamamelitol during the water stress treatment was initiated by decreased plant growth and increased leaf sucrose hydrolysis.     

Photosynthesis of Hedera Canariensis var. Azorica Variegated Leaves as Affected by Ozone

A differential response to long-term ozone exposures (50 and 100 mm3 m-3) was observed in the green and white areas of variegated leaves of Hedera canariensis var. azorica L. In green tissue the photosynthetic activity was depressed via a stomatal mechanism, and in white regions no effect was observed. Chlorophyll fluorescence parameters remained unchanged in green portions, whereas in the white ones Fm and Fv/Fm significantly diminished following ozone fumigation.     

Urushiols of poisonous anacardiaceae

GC-MS has been used to analyze and characterize the mixture of bis-trimethylsilyl derivatives of 3-n-alk(en)ylcatechols (urushiol) obtained from certain poisonous members of the Anacardiaceae. Analyses revealed a variation in composition of urushiol obtained from the same species. Furthermore, urushiols from poison ivy and poison wood, while consisting largely of n-C₁₅-substituted catechols, also contain varying amounts of the homologous n-C₁₇-substituted catechols. Similarly, the 3-alk(en)ylcatechol mixtures from poison oak, while containing mainly n-C₁₇-species, also contain varying amounts of the _n-C₁₅ species. The analysis of a single poison sumac sample revealed that it contained predominantly 3-_n-pentadec(en)ylcatechols.     

Increase in CO2 concentration could alter the response of Hedera helix to climate change

Increasing CO₂ concentration ([CO₂]) is likely to affect future species distributions, in interaction with other climate change drivers. However, current modeling approaches still seldom consider interactions between climatic factors and the importance of these interactions therefore remains mostly unexplored. Here, we combined dendrochronological and modeling approaches to study the interactive effects of increasing [CO₂] and temperature on the distribution of one of the main European liana species, Hedera helix. We combined a classical continent‐wide species distribution modeling approach with a case study using H. helix and Quercus cerris tree rings, where we explored the long‐term influence of a variety of climate drivers, including increasing [CO₂], and their interactions, on secondary growth. Finally, we explored how our findings could influence the model predictions. Climate‐only model predictions showed a small decrease in habitat suitability for H. helix in Europe; however, this was accompanied by a strong shift in the distribution toward the north and east. Our growth ring data suggested that H. helix can benefit from high [CO₂] under warm conditions, more than its tree hosts, which showed a weaker response to [CO₂] coupled with higher cavitation risk under high temperature. Increasing [CO₂] might therefore offset the negative effects of high temperatures on H. helix, and we illustrate how this might translate into maintenance of H. helix in warmer areas. Our results highlight the need to consider carbon fertilization and interactions between climate variables in ecological modeling. Combining dendrochronological analyses with spatial distribution modeling may provide opportunities to refine predictions of how climate change will affect species distributions.     

Growth promotion of ivy (Hedera helix L.) by paclobutrazol

Paclobutrazol was applied to juvenile ivy plants in an attempt to induce the mature form by the inhibition of gibberellin biosynthesis. Contrary to expectation, shoot elongation and adventitious root formation on aerial shoots were promoted.     

Fungal and animal associates of Toxicodendron spp. (Anacardiaceae) in North America

Toxicodendron spp. (Anacardiaceae; the poison ivies, oaks, and sumacs) are regarded by some as noxious, tenacious weeds in forests, grasslands, and waste places across the United States, despite playing numerous important ecological roles. Biological control of Toxicodendron spp. is a virtually unexplored option for ecosystem managers. The purpose of this review is twofold: (1) to synthesize and consider what is known about the biological relationships of Toxicodendron spp. from an ecological standpoint; and subsequently (2) to consider these associations from a managerial standpoint. Fungal, arthropodal, mammalian, and avian relationships are detailed, and their potential utility as biological control agents for Toxicodendron spp. are evaluated based on effectiveness, selectivity, practicality, and indirect or side effects. Fungi, and to a lesser extent arthropods, represent the most feasible agents for Toxicodendron spp. biological control.