Does mother know best? The preference–performance hypothesis and parent–offspring conflict in aboveground–belowground herbivore life cycles

1. A substantial amount of research on host‐plant selection by insect herbivores is focused around the preference–performance hypothesis (PPH). To date, the majority of studies have primarily considered insects with aboveground life cycles, overlooking insect herbivores that have both aboveground and belowground life stages, for which the PPH could be equally applicable. 2. This study investigated the factors influencing the performance of the root‐feeding vine weevil (Otiorhynchus sulcatus) larvae and whether this was linked to the oviposition behaviour of the maternal adult living aboveground. 3. Maternal insects feeding aboveground reduced root biomass by 34% and increased root carbon by 4%. Larvae feeding on plants subjected to aboveground herbivory had reduced mass. Irrespective of the presence of maternal herbivory, larval mass was positively correlated with root biomass. 4. Larval mass was also reduced by conspecific larvae, previously feeding on roots (19% reduction). However, the mechanism underpinning this effect remains unclear, as in contrast to maternal herbivory aboveground, prior larval feeding did not significantly affect root biomass or root carbon concentrations. 5. Maternal insects did not distinguish between plants infested with larvae and those that were free of larvae, in terms of their egg‐laying behaviour. Conversely, maternal insects tended to lay eggs on plants with smaller root systems, a behaviour that is likely to negatively affect offspring performance. 6. The PPH is not supported by our findings for the polyphagous vine weevil feeding on the host plant raspberry (Rubus idaeus), and in fact our results suggest that there is the potential for strong parent–offspring conflict in this system.     

Notes on the vegetation of the Bougainville Peninsula,Osborn and Institut Islands,North Kimberley District,Western Australia

The Bougainville Peninsula is formed of basalt capped with mesaform remnants of a bauxitic duricrust. On the plateau so formed there is little soil and the vegetation comprises scattered stunted eucalypts with grasses and hummock grasses or an understorey of Acacia and other shrubs. Locally there are patches of woodland of Eucalyptus nesophila and E. miniata. On the basalt country below the plateau there is deciduous vine thicket in the less accessible parts, a patchy mixture of vine thicket and savanna elsewhere including communities of vine thicket with scattered emergent eucalypts. The Osborn Islands are similar except that the mesaform capping is generally of sandstone. It is concluded that fire is the principal factor regulating the balance between vine thicket and savanna. Up to 40 years ago the area was populated by aborigines and regularly burnt off but this has now ceased so that colonisation by vine thicket is in progress, in spite of the low rainfall of the area.These authors are indebted to the Amax Exploration Company for providing helicopter transport to the localities concerned and for approval to publish this paper: also to the staff of the Western Australian Herbarium, Mr M. I. Brooker, Mr J. Macorochie and Dr V. Semeniuk for the identification of botanical specimens.This author is indebted to the Department of Defence (Navy Office) for permission to join a naval patrol boat. The assistance of Lieutenants J. Wells, R. Gates and the crew of HMAS Attack is gratefully acknowledged. The co-operation of Mr T. P. Farrell (CRA Services) and the Mitchell Plateau Bauxite Company for providing helicopter transport is also appreciated.     

The simulation of the vine biomass at different planting ages in Ningxia vineyards using DNDC model

The vine total biomass of different planting ages from plants in vineyard (1–12?years) was investigated by analysing biomass in stands with various ages and also simulated using the denitrification-decomposition (DNDC) model in the east Helan Mountains, Ningxia in 2011. The results indicated that the DNDC model accurately simulated the total biomass at different planting ages in the studied vineyard; the simulated results were approximately 93.6% of the measured results, and the biomass determination coefficient R² between the model simulation and the in situ observations was 0.948 (p?<?0.01), representing a significant correlation. Under the simulation, the vine biomass accumulation was found to be sensitive to the changes of fertilisation depth, soil organic carbon content, pH and other factors, and would effectively increase by appropriate increase of the fertilisation amount and decrease of the irrigation amount at the same time. Therefore, the DNDC model is applicable for simulating biomass in Ningxia vineyards and it has the potential to be widely applied to assess crop biomass variations under different climate conditions or management methods.