In Mediterranean habitats, the specialist butterfly Euphydryas aurinia oviposits on Lonicera implexa. Previous work has shown that ovipositing females select and lay a higher number of egg clusters on certain plants. In this paper the results of a field study aimed at assessing whether females use plant size and/or plant or leaf greenness (i.e., chlorophyll concentrations) as cues for oviposition are described. Size of plants did not appear to be an important factor in determining host plant selection, probably because even small plants provide enough resources for the young larvae to reach the diapausing stage and because last instar larvae, the most likely to face resource depletion, can move great distances in search of food. Measurements of both spectral reflectance and chlorophyll concentration of plants failed to reveal differences between host and non-host plants. On the other hand, reflectance and chlorophyll concentration of leaves were found to be important in oviposition choice as egg clusters were generally located on the greenest leaves with the highest chlorophyll contents. This suggests that females use visual cues to select the leaves that will provide optimal growth opportunities for newly hatched larvae. Although there was some indication that plants receiving a greater number of egg clusters also had more leaves of high chlorophyll content, multiple egg batches on single plants could also be a consequence of females being attracted by the presence of conspecific egg clusters.
Twelve randomly chosen Stipa tenacissima L. individuals were grouped into three tussock size classes, small (ST), medium (MT), and large (LT) with 5.6±0.8, 34.1±4.2, and 631.9±85.8 g of dry green foliar matter, respectively, in three plots with different S. tenacissima cover. Instantaneous (WUEi) and long-term (WUEl) water-use efficiencies were measured in two seasons of contrasting volumetric soil water content (early winter 21.0±0.8 % and summer 5.8±0.3 %). Maximum photochemical efficiency of photosystem 2 and stomatal conductance in summer assessed the extent of water and irradiance stress in tussocks of different size. WUEi was lower in MT and ST “water spender” strategies than in LT during the high water-availability season. In summer net photosynthetic rate and WUEi were higher and photoinhibition was lower in LT than in MT and ST. Significant spatial variability was found in WUEi. Water uptake was competitive in stands with denser alpha grass and more water availability in summer, reducing their WUEi. However, WUEl showed a rising tendency when water became scarce. Thus it is important to explicitly account for plant size in ecophysiological studies, which must be combined with demographic information when estimating functional processes at stand level in sequential scaling procedures. and D. A. Ramírez ... [et al.].