Influence of host plants on development, fecundity and egg hatchability of the arctiid moth Diacrisia casignetum

Measurements were made of the differences between sunflower and climbing hempweed leaves for development, fecundity and egg hatchability of Diacrisia casignetum Kollar. Developmental time and weight gains of sunflower-fed larvae were respectively longer and greater than those of hempweed-fed ones. The development time and weight gain, attributable to differences in host plants, were statistically heterogeneous (P<0.05-<0.10). Relative fecundity and egg hatchability of sunflower reared insects were greater than those of hempweed reared ones, and these were also statistically heterogeneous (P<0.1 and <0.05, respectively). Hempweed leaves contained relatively high titres of phenols and low ratios of proteins to phenols. Ovaries were heavier in insects reared on sunflower than on hempweed, whereas the level of phenols incorporated into the ovary was higher in insects fed on hempweed than those on sunflower. The differences in these parameters may be due to variations in nutritional quality of these hosts and incorporation of ingested phenolic materials to ovary and insect biomass.

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Résumé L'étude a porté sur l'évaluation de l'influence des feuilles de tournesol (Helianthus annuus) et de Mikana cordata sur le développement, la fécondité et l'éclosion des oeufs de D. casignetum Kollaz. La durée de développement et le gain de poids sur tournesol étaient plus importants que sur M. cordata. La durée de développement était statistiquement hétérogène (P<0.05), ce qui peut être dû à des différences entre plantes. La fécondité et le taux d'éclosion chez les insectes élevés sur tournesol étaient plus élevés que ceux observés sur M. cordata, dont les résultats étaient aussi hétérogènes (P<0.1 et<0.05 respectivement). Les feuilles de M. cordata contenaient des taux relativement élevés de phénols et des rapports protéines sur phénols bas. Tout ceci suggère que les différences observées sont attribuables à des variations dans la qualité nutritive de ces hôtes et dans l'incorporation à la biomasse de l'insecte de matériaux phénologiques ingérés.

     

Tuning of color contrast signals to visual sensitivity maxima of tree shrews by three Bornean highland Nepenthes species

Three species of Nepenthes pitcher plants (Nepenthes rajah, Nepenthes lowii and Nepenthes macrophylla) specialize in harvesting nutrients from tree shrew excreta in their pitchers. In all three species, nectaries on the underside of the pitcher lid are the focus of the tree shrews' attention. Tree shrews are dichromats, with visual sensitivity in the blue and green wavebands. All three Nepenthes species were shown to produce visual signals, in which the underside of the pitcher lid (the area of highest nectar production) stood out in high contrast to the adjacent area on the pitcher (i.e., was brighter), in the blue and green wavebands visible to the tree shrews. N. rajah showed the tightest degree of “tuning,” notably in the green waveband. Conversely, pitchers of Nepenthes burbidgeae, a typical insectivorous species sympatric with N. rajah, did not produce a color pattern tuned to tree shrew sensitivity maxima.     

Pollen production in some plant taxa with a supposed role in allergy in Eastern India

This paper deals with the production of pollen grains per anther per flower of 15 probably allergenic pollen producing angiospermic plant taxa growing in Eastern India. The selected plant taxa includesAilanthus excelsa, Alstonia scholaris, Argemone mexicana, Azadirachta indica, Cassia alata, C. siamea, Dalbergia sissoo, Holarrhena pubescens, Lagerstroemia speciosa, Madhuca indica, Milletia pinnata, Mimusops elengi, Morus alba, M. indica andMurraya paniculata. Among the investigated taxa,A. excelsa produces the highest number of pollen grains (1635180) followed byC. siamea (1589245) andA. mexicana (463800). The production of pollen grains is lowest inH. pubescens (2500), followed byA. scholaris (5175),A. indica (6220) andM. paniculata (11200).     

Steppe-like grassland as a refuge of the wild edible and medicinal plant species in anthropogenic landscape in northeastern Croatia

Habitat fragmentation and modification have been recognized as the most serious threats to biodiversity. In Croatia, the intensive human activities resulted in the landscape transformation, reduction of grassland areas and loss of species number. Increasingly threatened are the wild edible and medicinal plants which contribute remarkably to the biodiversity of different grassland types. In northeastern Croatia, one of the last remnants of the steppe-like grassland remained preserved in a very complex anthropogenic landscape. We examined the diversity of vascular plants occurring on this small habitat patch. Among the relatively high number of plant taxa (in a total of 177) found during the two years of investigations, most could be used both for human nutrition (28 taxa), and for the treatment of a wide range of diseases (60 taxa), while some taxa have nutritional value for livestock (17 taxa). All 23 recorded taxa with edible and medicinal properties are threatened in Croatia, 21 are threatened across Europe, and two are Red Listed taxa. Our results showed that small and isolated steppe-like grassland represents an important refuge for variety of valuable plant species in intensively used landscapes. Accordingly, such small habitats should be, at least locally, effectively protected.     

Hybridization and the evolution of invasiveness in plants and other organisms

Less than a decade ago, we proposed that hybridization could serve as a stimulus for the evolution of invasiveness in plants (Ellstrand and Schierenbeck Proc Nat Acad Sci USA 97:7043–7050, 2000). A substantial amount of research has taken place on that topic since the publication of that paper, stimulating the symposium that makes up this special issue. Here we present an update of this emergent field, based both on the papers in this volume and on the relevant literature. We reevaluate the lists that we presented in our earlier paper of reports in which hybridization has preceded the evolution of invasiveness. We discard a few cases that were found to be in error, published only as abstracts, or based on personal communication. Then we augment the list from examples in this volume and a supplementary literature search. Despite the omissions, the total number of cases has increased. Many have been strengthened. We add a list of cases in which there has been evidence that intra-taxon hybridization has preceded the evolution of invasiveness. We also provide a number of examples from organisms other than plants. We consider how our examples suggest mechanisms whereby hybridization may act to stimulate the evolution of invasiveness. Hybridization does not represent the only evolutionary pathway to invasiveness, but it is one that can explain why the appearance of invasiveness often involves a long lag time and/or multiple introductions of exotics.