Corema

Abstract: Summary We report a study of the reproductive biology of the dioecious shrub Corema album in Galicia (N-W Spain). Male flowers were larger and heavier than female flowers, though the overall investment in sexual reproduction by females was higher. Population pollen-to-ovule ratio was very high (about 173 000:1). Flowering phenology was synchronous between males and females. The relative spatial distribution of the sexes appears to be random. Fruit set was not significantly dependent on either distance to the nearest male or sum of distances to the nearest five males. However, our results suggest that fruit set is higher in population nuclei with high population densities. Furthermore, mean single—fruit weight was higher in the population nucleus with highest fruit set than in the other nuclei studied.

Abstract: Examination of air photos from 1930, 1970 and 2002 revealed stands of the European Scots Pine ( Pinus sylvestris ) invading remnants of natural Corema ( Corema conradii ) heathland in the Annapolis valley. To document the impact of the introduced pines, four natural habitats were compared with two adjacent habitats already invaded by the pines. All surveyed habitats had been dominated by Corema heath based on air photos taken in 1930. Twenty 1 m 2 quadrats were used to record presence and cover of vascular plants at each site. The invasive alien pines reduce the native cover to 12%. Vascular plant biodiversity is reduced to less than 42% and the cover of the heathland dominant, Corema conradii , is reduced from over 100 % to less than 2%. with Deschampsia flexuosa becoming the dominant species. The modified ecosystem and loss of biodiversity has economic impacts through loss of pollinators of agricultural crops and loss of germplasm of native crop relatives.

Abstract: Hair-covered scent organs of the male arctiid moth Creatonotos produce and dissipate the volatile pheromone hydroxydanaidal. The biosynthesis of this substance depends quantitatively upon the uptake of pyrrolizidine alkaloids (PA) with the larval foodplant. The size of the tubular, eversible scent organ (corema) is also positively correlated with the ingested amount of the same alkaloid, which acts like a specific growth factor. After an assessment of the corema normogenesis by Rick-Wagner (PhD thesis, University of Cologne, 1986) we injected PA into PA-free raised larvae, prepupae, and pupae. We found that the PA competence (sensitivity) of the corema anlage terminates with the first prepupal day. Ecdysone titer determinations (radioimmunoassay) are in agreement with those in other moth species. Ligated (ecdysone-free) pupal abdomina never developed imaginal structures, with or without earlier PA application. Ecdysone injection into ligated pupal abdomina of PA-fed specimens initiated the development of imaginal structures and also of coremata of more than (ecdysone-free) control size. Pupal abdomina without PA pre-treatment only developed very small coremata. With these experiments we have separated and identified two morphogenetic control agents of corema development: the dietary PA specifies the size of the organ whereas ecdysone induces the anlage to proliferate within these PA-dependent ranges and to differentiate adult structures, as it does with other imaginal anlagen.