Lycaena dispar is recorded as an early case of extinction and subsequent re‐introduction in the UK. However, repeated establishment attempts have not resulted in self‐sustaining populations, including those having taken place at Woodwalton Fen (Cambridgeshire, UK). Earlier studies at Woodwalton Fen showed that the highest mortalities occurred between the egg stage and resumption of larval feeding in spring. This study was designed; firstly, to investigate factors causing field mortality during different larval stages; secondly, to compare survival on Rumex hydrolapathum foodplants in different habitat situations; and thirdly, to compare survival in a natural population (Weerribben, The Netherlands) with the introduced Woodwalton Fen population. Experiments employed exclusion cages in order to examine the relative roles of vertebrate and invertebrate natural enemies, and survival on food‐plants in open fen and waterside situations was compared. Results suggest invertebrate predation to be the dominant mortality factor acting upon pre‐diapause larvae. Over the winter diapause natural enemies do not have a significant role. However during both these stages losses still occur that are unaccounted for. Extensive winter flooding appears to increase overwintering losses. Vertebrate predators cause significant mortality of post‐diapause larvae. No significant difference was found between larval survival on open fen versus waterside plants. Comparison of introduced and native populations reveal that overwintering survival was significantly higher in the latter; potential reasons for this difference are discussed.
1. The influence of seasonal flooding on wetland insects is understudied, and understanding of a potentially important influence on population dynamics is therefore incomplete. This is of particular consequence because many wetland insect species, including the large copper butterfly, Lycaena dispar batavus, are of conservation interest. 2. Previous studies on the submergence tolerance of diapausing L. d. batavus larvae have been inconclusive. This study investigated the effects of different periods of enforced submergence on overwintering survival, using both fresh and brackish water, and comparing effects on larvae in early and late diapause. 3. Larvae were submerged for up to 84 days, and survival was negatively correlated with submergence period, although periods of up to 28 days did not appear to reduce survival. Water type, i.e. fresh vs. brackish water, and larval stage, i.e. early vs. late diapause, had no significant influence on survival. 4. The relevance of these findings to the population biology and conservation of L. d. batavus is discussed. Further studies on the effects of submergence by seasonal flooding on wetland insect populations are encouraged.
Conservation of old-growth forests has become an increasingly important objective of Forest Service managers over the last three decades. The US Forest Service recently made changes to policies that prohibit cutting of live trees >53 cm (the “21-inch rule”). We review the disturbance ecology of dry and mesic old-growth forests of Oregon and contrast conservation policies for these two forest types. We describe the development of age-based alternatives to the 21-inch rule on the Klamath Reservation and in the Malheur National Forest in eastern Oregon. We conclude by outlining an adaptive management strategy to conserve dry forest old growth that seeks to restore the ecological processes that perpetuate old tree populations over time. We argue that what is good for dry forest ecosystems is good for dry forest old growth, especially in the face of changing climate and disturbance regimes. Study Implications: Age-based limits are a viable alternative to the size-based limits that the U.S. Forest Service has been using to conserve old growth in dry, fire-prone forests of eastern Oregon. Another alternative is a process-based approach that emphasizes restoring processes, including frequent fire that make old-growth trees resistant to a warmer and more fiery future. Multiscale inventories that track the abundance and distribution of trees of different species, sizes, and ages can inform tree conservation priorities and assess progress towards desired outcomes. Robust monitoring programs can facilitate collaborative data-driven adaptation at the local level and improve dry forest old-growth conservation outcomes.
Abstract. The large copper butterfly, Lycaena dispar batavus, a subspecies of much conservation interest, is host-specific to the great water dock, Rumex hydrolapathum, but little is known of the relationship between herbivore and host in wild populations. This study investigated the distribution of both R. hydrolapathum plants and L. d. batavus eggs in four different habitat types within the Weerribben National Park, The Netherlands, during the summer of 1993. As expected, host plant distribution strongly influenced that of its herbivore. Further, both species had significantly aggregated distributions, and that of R. hydrolapathum was in agreement with the negative binomial model. Host plant selection for oviposition showed no significant relationship with physical plant charac teristics, such as plant height and the number of leaves, and at the scale studied, habitat type was of only limited influence. The pos sible influence of the vegetational architecture surrounding host plants is discussed.
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