Although urban sprawl is increasingly becoming a worldwide problem, the effects associated with urbanization on local biodiversity particularly in the developing countries, is still poorly understood. We investigated plant species richness along urbanrural gradients in an Afro-tropical metropolitan Morogoro city in Tanzania, and examined patterns of species movement by humans within and outside the city and its potential impact on habitat homogenization of urban ecosystems. Biodiversity information was assessed in 120 sample plots (25 9 25 m) distributed in core urban, sub-urban and periurban (rural) zones, while patterns of plant resource use and species movement were surveyed from 120 households in the study area. We found the highest tree species richness in the urban core (82.6 ± 1.4 species) whereas tree density decreased from peri-urban (465.60 ± 152.03 tree/ha) to urban core (244.00 ± 120.86 tree/ha) and species diversity decreased from urban core (a = 2.82 ± 0.01) to peri-urban area (a = 2.61 ± 0.23). Further, the proportion of exotic species was significantly higher (75.6 %) than that of native species in the study area (p = 0.001). Tree community assemblages showed least differences among the study zones (dissimilarity = 10 %) and appear to have been influenced by local cultural differences, species movement as well as local resource use. Furthermore, species movement exhibited a random and multi-directional pattern perpetuated by human and nonhuman factors. Movements were significantly higher between backyard gardens within the city than from outside. Alien species by far outnumbered Communicated by David L. Hawksworth.

Understanding the behavior of species threatened with extinction is important for conservation planning and for solving problems facing species in captivity and the wild. We examined diurnal activity budgets and habitat use of the extinct in the wild Kihansi spray toad to provide insights into ongoing conservation initiatives for this species. Observations on eight target behaviors were made each morning and evening for 14 days, in two subpopulations at Kihansi and University of Dar es Salaam captive breeding centers. There were significantly more bouts of resting than calling, amplexing, hunting, walking, climbing, or feeding. There was no difference in mean time spent in each activity between the two subpopulations. The use of habitat was variable between age classes, subpopulations and sampling time. Young toads spent significantly more time resting at the top of vegetation and on walls while adults rested more on logs. Further, adults foraged more on the walls and vegetation in the morning and on the ground in the evening. Contrastingly, young toads foraged more on the ground in the morning and switched to elevated patches during evening. The similarity of the toads' behavior suggests that important biological traits are still maintained in captivity and retained across toad generations. Furthermore, temporal and spatial variations in the use of habitat structures between age groups suggest fine-scale resource partitioning to reduce competition in this gregarious species. These results highlight the importance of maintaining diverse habitat structures in captivity and are useful for planning species reintroduction and future restocking programs.

Fifty bread wheat lines were evaluated for heat tolerance and compared to some local cultivars under three sowing dates (November 25th, December 15th and January 5th). Four agronomic traits were evaluated, i.e. No. of spikes per plant, grain yield per plant, 100-kernel weight and harvest index under normal and stress conditions. Analysis of variance showed highly significant variations among the tested lines and demonstrating that the main effect of sowing dates was due to the late date. Grain yield per plant was the most affected trait by heat followed by 100-kernel weight and No. of spikes per plant, while harvest index showed the lowest reduction due to heat stress. Six lines (L1, L11, L16, L34, L37 and L41) showed heat tolerance based on high performance in grain yield/plant by 29.45, 29.75, 27.75, 27.43, 27.37 and 31.90 g, respectively under late sowing conditions as well as low heat sensitivity index. The sequence related amplified polymorphism (SRAP) was able to differentiate between bulked DNA samples of lines with the highest and lowest performance in agronomic traits under heat stress. SRAP generated 2, 1 and 3 bands specific for lines with high performance of No. of spikes per plant, grain yield per plant and harvest index, respectively as well as it showed 5 and 3 bands specific for lines with low performance of grain yield per plant and harvest index, respectively. These specific bands could serve in wheat genotyping and screening, and might be used as SRAP markers associated with heat tolerance in wheat breeding programs.

The tropical forest kapok tree occurs widely in urban environments, dispersing thousands of floss during the fruiting season. However, its seedlings are rarely seen around human settlements, raising questions on what factors might be limiting its recruitment. We examined the pattern of floss release, seed fall post-dispersal and influences of watering frequency on germination of Ceiba pentandra seeds. Evening, overall, was associated with a significantly higher rate and quantity of floss release (p = 0.0001) than were midday and morning, correlating well with the speed of wind across the day (rh = 0.666, p = 0.001). Mean dispersal quantity differed significantly between the individual sampled trees, in which the highest dispersal was recorded from trees located in relatively open areas and the lowest was recorded in closed stand trees. Seed fall was higher within 100 m distances than seed fall farther away from dispersing trees, depending on the microsites and weather conditions. Germination started on day 5 onwards and only 15.67% of sown seeds germinated. Watering frequency strongly influenced seed germination while local human activities determined fate of dispersed seeds. We conclude that recruitment of C. pentandra species in the study area may have been limited by environmental and human factors operating at various local and spatial scales.