No evidence that rapid adaptation impedes biological control of an invasive plant.

Biological control is a popular tool for invasive species management, but its success in nature is difficult to predict. One risk is that invasive plants, which may have adapted to lower herbivore pressure in the introduced range, could rapidly evolve defences upon re-association with their biocontrol agent(s). Previous studies have demonstrated that populations of the invasive plant purple loosestrife (Lythrum salicaria) exposed to biocontrol exhibit traits consistent with the rapid evolution of defence. However, to date, no one has tested this hypothesis under field-natural levels of herbivory. Using seed from 17 populations of purple loosestrife growing in eastern Canada, that varied in their history of exposure to their biocontrol agent, the leaf beetle Neogalerucella spp., we transplanted 1,088 seedlings from 136 maternal families into a common garden under ambient herbivory. Over the following three and half years, we assessed plant performance in the face of biocontrol by measuring early-season plant size, defoliation, flowering, and season-end biomass. We discovered that a population history with biocontrol explained little variation in herbivory or plant performance, suggesting that adaptation is not hindering biocontrol effectiveness. Instead, plant size, subsequent defoliation, and spatio-temporal variables were the main predictors of plant growth and flowering during the study. The high individual variability we observed in plant performance underscores that flexible strategies of allocation and phenology are important contributors to the persistence of invasive plants. Our findings suggest that plant adaptation to biocontrol is unlikely to be a strong impediment to biological control in this species, however, the high survival and variable defoliation of plants in our study also indicate that biocontrol alone is unlikely to result in significant population decline. We recommend that the application of multiple forms of control simultaneously (e.g. thinning plus biocontrol) could help to prevent the existence of refuges of large, reproductive individuals.

Genetic structure and reproductive strategy of the ant Cardiocondyla elegans: strictly monogynous nests invaded by unrelated sexuals.

Cardiocondyla elegans is a Mediterranean ant that nests on river banks. It rears only wingless (ergatoid) males that live peacefully in the same nest as opposed to other species of the same genus, which have both peaceful, winged and mutually aggressive 'ergatoid' males. Using microsatellite analysis, we investigated the genetic structure of 21 colonies from three different locations as well as the parentage of sexuals of two colonies of C. elegans. We show that C. elegans is strictly monogynous, and that its nests can contain foreign sexuals. The presence of alien sexuals inside ant nests is described for the first time and probably counteracts inbreeding resulting from matings between siblings. In the laboratory, aggression tests showed that workers only allow alien males to enter their nests, while all winged female sexuals attempting to enter were attacked. Nevertheless, the presence of alien female sexuals in nests in the field seems to result from active carrying behaviour by workers during the reproductive period.

A new case of jumping behaviour in ants, as part of the foraging strategy.

We demonstrated for the first time in this laboratory study that the tree-dwelling ant Polyrhachis laboriosa can jump down beyond any context of escape or predation. When it is necessary to jump to reach an isolated food supply or explore a larger territory, workers of P. laboriosa jump down from a height of 5-100 cm. The characteristics of this active jumping display are described here. During foraging or exploratory conditions, the workers learnt to jump and integrated this behaviour into their strategy of exploitation of the 3D-environment. Under laboratory conditions, they began to jump earlier and more frequently as a function of their motivation during successive tests.

Ritualised versus aggressive behaviours displayed by Polyrhachis laboriosa (F. Smith) during intraspecific competition.

The intraspecific territoriality of Polyrhachis laboriosa was studied thanks to dyadic confrontations between nestmates and alien foragers in chemically marked and unmarked arenas, complementing experiments and observations in nature. When foragers meet, the alien flees while the resident attacks, especially when on a marked area. However, when an alien scout extends its territory, it attacks the resident ant, such confrontation resulting in a high rate of reciprocal full attacks. When surrounded by several residents, the intruder is always spread-eagled if it does not succeed in fleeing. We described ritualised displays, such as threatening (opening mandibles; bending the gaster) or appeasing behaviours (antennal boxing; attempt at trophallaxis; pupal posture; raising the gaster). They occur only when the encounter maintains a low level of aggression, during laboratory experiments, or in nature during encounters involving a queen or an experimentally-introduced intruder. Foraging queens are tolerated on the territories of conspecific mature colonies. When they encounter resident workers, reciprocal avoidance occurs. Nevertheless, the latter perform ritualised displays when the queens approach their nest or attempt to rob their prey. This situation seems to compensate in part the archaic semi-claustral mode of foundation of this species, as the queens are indirectly protected by their conspecifics who do not tolerate other competitors around large food sources.

The tectonic regimes along the convergent border of the Aegean Arc from the late Miocene to the present : Southern Peloponnesus as an example

Field analysis of fault kinematics demonstrates changes in the tectonic regime on the Aegean Arc border. During the Pliocene-Early Pleistocene extensional tectonics were active; extension trended radial retreat of a high angle-dipping slab which decreased the magnitude of the push on the Aegean lithosphere. During the Mid-Late Pleistocene compression has been active in the lowlands and extension in the highlands of the arc border, the extensional directions being orthogonal to the compressional directions and parallel to the arc border. It is suggested that this has resulted from a push of a low angle-dipping slab on the Aegean lithosphere. These stress patterns are interpreted at a large wavelenght as a result of a balance between the boundary forces acting along the arc border and the body forces due to the thickening of the crust. Rotations of the paleostress directions due to rigid rotations of the material and perturbations of the stress trajectories are also considered in analysis the paleostress maps of the Aegean

Traps in displaying optical performances of a progressive-addition lens.

Typical traps when displaying the partial optical performances of a progressive-addition lens (PAL) are presented. The PAL is briefly described first. Then the ray-tracing software is described in detail. It permits the computation of the optical performance of the PAL in typical cases. For a reference PAL optical partial performances, which are computed in different cases, are displayed. The plots show that the performance depends on the computation conditions, that displaying only some areas of the partial performance may lead to traps for the characterization of the PAL, and that coma must be taken into account to obtain a precise measurement.

Generalization of the Tscherning theory: optimization of aspheric ophthalmic lenses.

The perfect single vision ophthalmic lens should be free from oblique astigmatism, mean oblique error, distortion and chromatism. At the same time, it should be aesthetic and comfortable. By means of third-order theory, we show that T scherning ellipses can be considered to correspond merely to the particular case in which the lens surface is spherical in the three-dimensional space defined by the conic constant epsilon, the power of the first surface D1, and the back vertex power D. Consideration is given to the best way of building a merit function for final optimization with a classical ray tracing optimization program on a computer.