Response of plant species and life form diversity to variable fire histories and biomass in the jarrah forest of south‐west Australia

Frequent fires reduce the abundance of woody plant species and favour herbaceous species. Plant species richness also tends to increase with decreasing vegetation biomass and cover due to reduced competition for light. We assessed the influence of variable fire histories and site biomass on the following diversity measures: woody and herbaceous species richness, overall species richness and evenness, and life form evenness (i.e. the relative abundance or dominance among six herbaceous and six woody plant life forms), across 16 mixed jarrah (Eucalyptus marginata) and marri (Corymbia calophylla) forest stands in south‐west Australia. Fire frequency was defined as the total number of fires over a 30‐year period. Overall species richness and species evenness did not vary with fire frequency or biomass. However, there were more herbaceous species (particularly rushes, geophytes and herbs) where there were fewer shrubs and low biomass, suggesting that more herbaceous species coexist where dominance by shrubs is low. Frequently burnt plots also had lower number and abundance of shrub species. Life form evenness was also higher at both high fire frequency and low biomass sites. These results suggest that the impact of fire frequency and biomass on vegetation composition is mediated by local interactions among different life forms rather than among individual species. Our results demonstrate that measuring the variation in the relative diversity of different woody and herbaceous life forms is crucial to understanding the compositional response of forests and other structurally complex vegetation communities to changes in disturbance regime such as increased fire frequency.     

The distributions of a wide range of taxonomic groups are expanding polewards

Evidence is accumulating of shifts in species' distributions during recent climate warming. However, most of this information comes predominantly from studies of a relatively small selection of taxa (i.e., plants, birds and butterflies), which may not be representative of biodiversity as a whole. Using data from less well‐studied groups, we show that a wide variety of vertebrate and invertebrate species have moved northwards and uphill in Britain over approximately 25 years, mirroring, and in some cases exceeding, the responses of better‐known groups.     

Coincidence between consumer and host occurrence: macrolepidoptera in Britain

1. The interspecific relationship between the distributions of consumers and resources is examined, using data for macrolepidoptera (moths) in Britain.
2. Monophagous moth species feeding on host plants with small geographical ranges also have small ranges, whilst those feeding on host plants with large ranges may have small or large ranges themselves. Likewise, there is an approximately triangular relationship between the proportion of the range of its host that a monophagous moth occupies and the size of the host range.
3. Most monophagous moths occupy a small proportion of the range of their host, and only feed on hosts that have relatively large geographical ranges.
4. Factors determining both the range size of a monophage and the proportion of the host plant's range that it occupies are independent of taxonomy.
5. Monophages tend to have smaller geographical ranges than congeneric polyphages, but do not occupy a smaller proportion of the ranges of the plants that they consume.     

Nutritional reserves regulate male participation in Mediterranean fruit fly leks

1. The mating system of Mediterranean fruit flies ( Ceratitis capitata , Diptera: Tephritidae), is based on male leks that form on the foliage of trees. Following observations that not all males participate in leks, the hypotheses that (a) small males are absent from leks and (b) males with inadequate nutrient reserves are unable to participate in leks were examined.
2. The size and weight of lekking males ( n = 183) and resting males captured at the same time in the vicinity of leks ( n = 148) were established. In addition, using biochemical techniques, the amounts of sugar, glycogen, lipid and protein in each individual were established quantitatively.
3. There was no significant size difference between lekking and resting males. However, lekking males were significantly heavier and contained significantly more sugars and protein than resting males.
4. In conclusion, leks are exclusive, and only males with adequate nutritional reserves may join. Thus, in this species, reproductive success is closely linked to foraging success.     

Cyclic AMP Promotion and Abscisic Acid Inhibition of {alpha}-Amylase Activity in the Seeds of Rice (Oryza sativa L.)

Cyclic AMP and GA₃ stimulated both -amylase activity in riceendosperm and the germination of the seed. In combination theyalso induced germination of ABA-treated seeds but cyclic AMPalone failed to neutralize the inhibitory effect of ABA; withadded kinetin, however, it promoted the -amylase activity ofthe dormant seeds. The enzyme activity decreased as the storageperiod of seeds increased. Cyclic AMP and GA