Inter‐individual variation in movement: is there a mobility syndrome in the large white butterfly Pieris brassicae?

1. One of the main drivers of the genesis and maintenance of biodiversity is mobility, i.e. the net result of the interaction between physiological performances (movement capacity) and behavioural decisions (movement decisions). Although several previous studies have found personality traits related to mobility, it is not yet clear whether mobility involves a real syndrome, i.e. whether individuals showing good movement capacity are also more likely to decide to move, and whether these inter‐individual differences are consistent across time. 2. The aim of the present study was therefore to disentangle the mechanisms underlying the maintenance of inter‐individual variation in mobility by measuring three traits related to mobility under experimental conditions in a butterfly species, and to test the existence of correlations between these traits. These measures implied movement capacity and movement decision. 3. It was shown that mobility‐related traits were (i) consistent across time, (ii) inter‐correlated, and (iii) dependent upon sex and morphology. 4. These results therefore suggest the existence of a mobility syndrome in a butterfly. Such findings highlight the necessity to accurately integrate inter‐individual variation (behavioural syndrome) in our comprehension of the evolution of movement strategies.     

Influence of Tops and Roots on Net Assimilation Rate of Sugar-beet and Spinach Beet and Grafts between them

Sugar-beet has a larger storage root and greater net assimilationrate (E) than spinach beet. To determine whether the greaterroot was a result or cause of the greater E, grafts were madebetween tops and roots of sugar-beet and spinach-beet in allfour possible combinations. Grafted plants with sugar-beet roots had greater E and rootdry weight, less leaf area and top dry weight and lower concentrationof sugar in the leaf lamina, than those with spinach-beet roots,irrespective of the type of top. Grafted plants with sugar-beettops had greater E, total and root dry weight, but less leafarea, than those with spinach-beet tops, irrespective of thetype of root. The difference in E between grafted plants withsugar-beet tops and spinach-beet tops was similar to that betweengrafted plants with sugar-beet roots and spinach-beet roots.It increased with time to 60 per cent. Increases in E probably represent increases in rate of photosynthesis.Sugar-beet roots probably increased photosynthesis by providinga better sink for assimilates than spinach-beet roots.     

Manipulation of host plant development by the gall-midge Rhabdophaga strobiloides

Abstract. 1. The gall-midge Rhabdophaga strobiloides (O.S.) forms a gall in the apical bud of actively growing willow twigs.
2. Galls were not randomly distributed among twigs. Twigs that arose towards the distal end of the branch were much more likely to be galled. Distally located twigs also grew to greater girth than more proximally located twigs.
3. Comparisons of galled twigs with normal twigs in similar locations along their branch showed that the gall causes even greater growth in twig girth than when no gall is present.
4. The hypothesis that galled twigs draw photosynthate produced elsewhere in the plant was tested in an experiment that measured the growth of galled and normal twigs. with their leaves intact, to galled and normal twigs that were manually defoliated. Defoliation caused reduced growth in normal twigs, but galled twigs grew equally well with or without their leaves. Leaf removal had no effect on gall growth.
5. Twig diameter was positively correlated with gall diameter. Call diameter was positively correlated with larval biomass.
6. Patterns of twig and gall growth suggest that the gall-midge manipulates host plant growth and development to provide resources for growth and survival. Manipulation of the host may be an important phenomenon in the evolution of parasitic organisms.     

Hatching agents for the potato cyst-nematode, Heterodera rostochiensis Woll

Of 444 compounds tested for their ability to stimulate eggs of Heterodera rostochiensis to hatch, forty-five did so to varying extents. Many compounds that hatched H. schachtii Schm. eggs did not hatch H. rostochiensis eggs. The most effective compounds with H. rostochiensis were picrolonic acid, anhydro-tetronic acid and vanadates. Tests with analogues of picrolonic and anhydro-tetronic acids suggested some structures that may be concerned in hatching H. rostochiensis and H. schachtii. The simple analogues hatched the eggs of H. schachtii but not those of H. rostochiensis. Suitably placed polarisable atoms seemed to be an essential feature. Picrolonic acid contains pairs of polarizable atoms, about 4 and 6·7 Å apart, that may respectively be associated with the hatching of H. schachtii and H. rostochiensis. Other features of the more active hatching agents were a cis and co-planar arrangement of the two polarizable atoms with respect to the rest of the molecule. The function of hatching agents is discussed.