Rats,pigs and men: disturbance and diversity in the New Guinea highlands

A trapping study of four species of Rattus and three of Melomys in rainforest and grassland habitats revealed differences in altitudinal distribution and in both gross and subtle habitat selection between species. The species are ranked on a scale of increasing opportunism on the basis of various demographic characteristics (e.g. reproductive rate, life span and population density). Species judged to be more opportunistic occur in habitats subject to more intense disturbance from pigs and humans. It is argued that changes in the pattern of species coexistence have followed overt human impact in the New Guinea highlands.     

Determinants of foraging profitability in two nectarivorous butterflies

ABSTRACT.

• 1 I studied flower selection and foraging energetics of Agraulis vanillae L. (Nymphalidae) and Phoebis sennae (Pieridae), two butterfly species common to north central Florida. I identified the major nectar resources exploited by several populations of these butterflies and, for each plant species, measured available nectar volumes and concentrations, corolla lengths, and density. I quantified foraging behaviour of each butterfly species at each nectar source (flower visitation rate and percentage of foraging time in flight), and used these data to estimate the net rate of energy intake of each butterfly species at each nectar source.
• 2 Estimated mean energy contents of individual flowers of the eleven exploited plant species spanned three orders of magnitude, ranging between 0.015 and 9.27 joules. Mean energy content of individual flowers was strongly correlated with mean foraging profit of both butterfly species.
• 3 Mean nectar volume strongly influenced energy content and varied widely within and among species, ranging from 0.0076 to 1.853 μ1. Nectar concentration varied between 17.1% and 40.4% sucrose-equivalents. Nectar volume was the best single predictor of foraging profitability (correlation coefficients of 0.994 and 0.984 for Phoebis and Agraulis respectively). Corolla length also strongly affected foraging profitability for both butterfly species; flower species with longer corollas were generally more profitable.
• 4 Flower density and nectar concentration showed weak or nonsignificant associations with foraging profitability.
• 5 The usefulness and limitations of these floral characteristics as bases for foraging selectivity, and the selective pressures foraging butterflies might place on the visited plants are discussed.

     

Are galling insects better protected against parasitoids than exposed feeders?: a test using tenthredinid sawflies

ABSTRACT.

• 1 Data mostly from the published literature were used to assess the effect of galling on the number of parasitoid species per host species in the phylogeny of nematine sawflies from free external feeders (colonial and solitary) to leaf gallers and shoot gallers.
• 2 The strongest effects of galling were the total elimination of the species-rich cocoon-attacking guild of parasitoids, and eonymphal parasitoids, from the parasitoid community on shoot gallers, all of which are in the genus Euura.
• 3 All tachinid larval parasitoids were also eliminated by the galling habit.
• 4 The cumulative effects of these exclusions resulted in a decline in mean number of parasitoid species per host species from almost sixteen species on external colonial feeders to 4.0 species on shoot gallers.
• 5 General patterns in per cent parasitism by non-tachinid and tachinid larval parasitoids, eonymphal and cocoon parasitoids, on exposed feeders to shoot gallers, showed declines in non-tachinid attack and elimination of tachinid, eonymphal and cocoon parasitoids. But leaf gallers tended to be attacked more than exposed feeders by non-tachinid larval parasitoids.
• 6 The galling habit had a long-term impact by reducing the number of parasitoid species attacking nematine sawfly gallers and per cent mortality inflicted, so that natural enemies may have been important as a selective factor in the evolution of galling nematine sawflies.

     

New land tortoises (Testudines: Testudinidae) from the Miocene of Africa

The described fossil testudinids from the Miocene of Africa are reviewed. Geochelone stromeri sp. nov . is described from Lower Pliocene (Langebaanweg) and Miocene (Namib) specimens. Kinixys erosa , an extant species, is reported from Songhor Hill. Chersina sp. is reported from Arrisdrift. Impregnochelys pachytectis gen. et sp. nov . is described from Rusinga Island, Kenya, and is unique in having the anterior shell opening orientated ventrally and in having struts on the internal surface of the neurals, but shares with Kinixys a unique epiplastron shape, a high number of axillary scutes and unique orientation of the head of the femur.     

Polyamine Depletion Following Exposure to DL-α-Difluoromethylornithine Both In Vivo and In Vitro Initiates Morphological Alterations and Mitochondrial Activation in a Monomorphic Strain of Trypanosoma brucei brucei

ABSTRACT. DL-α-difluoromethylornithine (DFMO), a specific irreversible inhibitor of ornithine decarboxylase (ODC), rapidly depletes cells of intracellular putrescine. When administered to animals and humans, DFMO cures acute infections of trypanosomiasis. In order to determine if the mechanism of drug action is related to initiation of transformation and biochemical alterations subsequent to polyamine depletion, trypanosome morphology and mitochondrial activation were studied in a monomorphic strain of Trypanosoma brucei brucei. Exposure of trypanosomes to DFMO in vivo in infected rodents or in vitro in culture resulted in a depletion of intracellular putrescine and a cessation of cell division without specific cytotoxicity. These events were followed by a transformation of the long slender bloodstream form to a short stumpy form via an intermediate morphology. Putrescine, the product of the ODC reaction, abrogates this effect. When introduced into SDM-79 medium, the intermediate form is capable of further transformation to an "insect" procyclic trypomastigote whereas the long slender form and short stumpy form are not. Short stumpy forms are incapable of binary fission and have lost their infectivity for the vertebrate host. In addition, the mitochondrial marker enzyme, NAD diaphorase, was found only in the short stumpy and intermediate forms. We hypothesize that the short stumpy phenotype may not be a viable stage in the natural transformation of the trypanosome from its mammalian host to the insect vector.