In addition to other factors, high altitude (HA) environment is characterized by high photosynthetic photon flux density (PPFD). Photosynthetic characteristics of wild and cultivated plants were studied at different irradiances at Losar, India (altitude 4 200 m). Wild plants were tolerant to high PPFDs. Slopes of curve between net photosynthetic rate (PN) and intercellular CO2 concentration
(Ci) or stomatal conductance (gs) increased with increase in irradiance suggesting insensitivity or tolerance of these plants to higher PPFD. Cultivated plants, however, were sensitive to higher PPFD, their slopes of curves between PN and Ci or gs decreased with increased PPFD. Tolerance or insensitivity to higher PPFD was an important parameter affecting plant performance at HA. and N. Kumar, S. Kumar, P. S. Ahuja.
The duration of development, reproduction and longevity of Gastrophysa viridula (DeGeer) was measured at constant temperatures and a long day photoperiod. At 18, 21.5, 25, and 28°C the average duration of development of the egg, larval and pupal stages and total development time (28.2, 21.6, 16.1, 15.0 days) decreased with temperature but the proportion of time spent in the egg, larval and pupal stages did not significantly change with temperature. Total development required 304.6 day degrees above the lower development threshold of 7.1°C. Pre-adult mortality and the rate of oviposition increased, and the duration of oviposition decreased with increasing temperature. Net reproduction rate Ro decreased (from 157 female eggs at 18°C to 75 female eggs at 28°C) and mean generation time T also decreased (from 45.5 days at 18°C to 24.1 days at 28°C) with increasing temperature. The intrinsic rate of population increase rm increased with temperature (from 0.111 at 18°C to 0.179 at 28°C). On a physiological time scale the average generation time T was 496 day degrees.
The Large Copper butterfly, Lycaena dispar, is extinct in Britain and rapidly declining in the rest of Europe, due predominantly to loss of its wetland habitats. In the Netherlands the sub-species L. d. batavus is at the edge of its range in Northern Europe and, as with most marginal butterflies, has more specialised food plant and habitat requirements than the core populations of L. d. rutilus. We investigate reasons for the relative specialisation of L. d. batavus on Rumex hydrolapathum in a fenland habitat when compared to the more widespread and common L. d. rutilus. Host-plant choice by ovipositing females and by larvae are measured as well as larval performance on alternative hosts. Laboratory experiments reveal that larvae are able to feed on other Rumex species without detriment to their overall survival and can utilise these alternative host plants at least as efficiently as their natural host plant. This suggests that plant chemistry is not responsible for their lack of utilisation in the wild. Under greenhouse conditions, females showed an equal willingness to oviposit on host and alternative Rumex, expressing no significant preference for any particular plant species. However, in field experiments using free-ranging females in a fenland habitat, eggs were laid only on R. hydrolapathum. Our interpretation is that there are no short distance cues discriminating between the three Rumex species but longer distance cues in the field situation may operate to maintain this host-plant specialisation. The selection pressure maintaining L. d. batavus as a specialist on R. hydrolapathum in a wetland may underlie its current rarity.
The Large Copper butterfly, Lycaena dispar batavus, is extinct in Britain and rapidly declining in Europe, due predominantly to loss of its wetland habitats. Northern populations have more specialised foodplant and habitat requirements than their more southerly counterparts and rely solely on Rumex hydrolapathum, the Great Water Dock, as their hostplants. Southern colonies use a greater range of Rumex. Previous work has shown that specialisation is not due to foodplant chemistry and in this paper we investigate the ability of different Rumex species to support the larval stages of L. d. batavus in a natural environment. Comparisons were also made between a captive colony at Woodwalton Fen, Cambridgeshire, UK and native larvae at De Weerribben, Netherlands. Field experiments using a captive colony revealed that other Rumex hosts can successfully support larvae throughout each of their larval stages in wet grassland and fenland habitats with no significant differences in survival rates compared with their natural hostplant R. hydrolapathum. An overwintering experiment using a native wild population of both butterfly and Rumex species in De Weerribben found 25% of larvae survived on the natural hostplant R. hydrolapathum and no survivors on alternative Rumex hosts. It is suggested that R. crispus and R. obtusifolius growing in their natural habitat may harbour significant competitors to L. d. batavus leading to its specialisation on R. hydrolapathum in fenland habitats.