Is the natural UV zone important for successful captive propagation of the Panther Chameleon (Furcifer pardalis); are different UVB irradiance exposures that generate a similar dose equally successful?

While we generally understand the optimal ultraviolet B (UVB) environment for the growth and reproduction of female Panther Chameleons Furcifer pardalis, we do not know the relative importance of UVB irradiance and dose for optimal husbandry outcomes. Accordingly, we experimented with Panther Chameleon females to test the hypothesis that UVB dose (irradiance × exposure duration) determines the outcome, regardless of the combination of UVB irradiance and exposure duration generating the dose. We varied UVB irradiance and exposure duration across treatment groups while keeping dose similar and within a range previously documented to result in reproductive success. The growth rate, age of maturity, and measurable vitamin D status were not significantly different among the treatment groups. Individuals in all groups produced viable eggs that successfully hatched. Thus, we found some support for the hypothesis that the UVB dose determines the outcome regardless of UVB irradiance. However, mean egg vitamin D3 concentration and percent hatching were higher in the highest UVB irradiance group, despite similar doses among the three groups. Preliminary field data reveal that this species occupies UV irradiance Zone 4 in Madagascar, the highest zone for reptiles recorded. Only the irradiance of the high UVB irradiance group in our experiment approached this zone and resulted in the best reproductive success. Biosynthesis of vitamin D3 and provisioning to eggs is more efficient when exposure to UVB irradiance is similar to that in their natural environment. Establishing an optimal UVB environment, based on knowledge of the natural UVB environment, is important for the propagation of Panther Chameleons in captivity.

Effects of diversity and pattern on relative yields of four michigan first year fallow field plant species.

1. A study was designed to investigate the effects of intra and inter-specific competition on the productivity of single and multi-species stands of plants normally dominant in first year old-field communities of mid-Michigan. The four species used were Amaranthus retroflexus, Chenopodium album, Panicum capillare and Setaria viridis. 2. Specifically, we tested (1) the relationship between diversity and productivity, (2) the effect of arrangement (pattern) of individuals within an array of old-field dominants on yield and (3) the expression of dominance and resultant allocation of yields within mixture arrays of different plant species. In direct contrast to many earlier studies, our experiments were completed in the field under natural conditions. 3. Mean yield of the highest yielding monoculture, Amaranthus, was greater than any of the yields of the mixture plots. 4. Changing the pattern within mixtures had no significant effect on the yields of the mixture plots. Distribution of biomass among the component species followed a geometric pattern similar to that predicted by the niche pre-emption hypothesis (Whittaker, 1965, 1969). Using yield as a criterion, dominance was clearly expressed in the mixture plots. Amaranthus contributed more than 50% of the yield in all of the mixture plots. 5. A relative competitive ability index (RCA) was developed to demonstrate more clearly the intra and interspecific relationships among the species in mixture plots and to "equalize" the inherent weight differential among species. Relative Competitive Ability, from highest to lowest, was Amaranthus, Chenopodium, Setaria and Panicum. 6. The paired species experiment demonstrated that the performance of species in multi-species arrays cannot be predicted from paired competition experiments. 7. In the diversity-yield experiment and the paired-species competitive ability experiment, dicotyledons were clearly superior to monocotyledons.

Insect response to mixture and monoculture patches of Michigan old-field annual herbs.

1. The response of insects to the presence of discrete arrays of mixture and monoculture plots of weed species normally dominant in first-year Michigan old-fields was studied. 2. Plant species used were Amaranthus retroflexus, Chenopodium album, Panicum capillare and Setaria viridis. 3. Two experiments were implemented, one with pure stands of each species and the other with mixture stands of equiproportionate numbers of each plant species (Fig. 1). 4. Sucking insects had significantly higher weights, lower diversities and greater expressions of dominance in Chenopodium stands (Tables 2 and 3) (Fig. 2). Chewing insects showed a similar response with regard to weight (Fig. 2), but not with respect to diversity and evenness indices (Tables 2 and 3). Non-herbivorous insects did not differentiate between the species when in pure stands. 5. Although there was a significantly greater mean weight of sucking insects in the mixture plots, none of the insect guilds differed significantly among the mixture treatments with respect to the parameters tested (Tables 2 and 3). 6. Results of this study support the C4 avoidance hypothesis (Caswell et al., 1973), especially with regard to sucking insects. 7. Continued studies investigating plant-insect interaction are discussed.