Testing the Enemy Release Hypothesis on tall-statured grasses in South Africa, using Arundo donax, Phragmites australis, and Phragmites mauritianus as models

The Enemy Release Hypothesis (ERH) predicts that introduced plant species can escape herbivory and therefore have a competitive advantage over native plants, which are exposed to both generalist and specialist natural enemies. In this study, the ERH was explored using the invasive alien species, Arundo donax and two native tall-statured grasses, the cosmopolitan Phragmites australis and African endemic Phragmites mauritianus in South Africa. It was predicted that A. donax would have reduced species richness of herbivores compared with the native Phragmites spp., that it would be devoid of specialist herbivores and would thus be experiencing enemy escape in the adventive range. The herbivore assemblages were determined from both field surveys and a literature review. The assumptions of the ERH were for the most part not met; 13 herbivores were found on A. donax compared with 17 on P. australis and 20 on P. mauritianus. Arundo donax had two specialist herbivores from its native range, and shared native herbivores with Phragmites spp. Although A. donax had reduced species richness and diversity compared with that found in the native distribution, it has partially re-acquired a herbivore assemblage which is similar to that found on analogous native species. This suggests that enemy release may not fully explain the invasive success of A. donax in South Africa.

Distribution, habitat and status of ‘Endangered’ Sakalava Rail of Madagascar

SummaryThe ‘Endangered’ Sakalava Rail Amaurornis olivieri is endemic to wetlands in western Madagascar, where it has been recorded between the Betsiboka river in the north and the Mangoky river in the south. Between August 2003 and November 2006, including dry and wet seasons, we surveyed 36 potentially suitable wetlands throughout its known range. We found Sakalava Rails at five sites: Lacs Kinkony, Ampandra, Amparihy, Sahapy and Mandrozo. At each site the population was small (12–39 individuals) and the highest density was 20 individuals km−2. We found up to 67 birds in each field visit and the total number of birds (sum of maxima at each site) seen was 100. We estimate the total population at the five sites to be 215 rails. We cannot confirm that the population lies within the range estimated in the current Red List (250–999 individuals), although this may yet be proven correct. The typical breeding habitat of Sakalava Rail is lotic marshes with a mixture of large areas of open water, reed Phragmites mauritianus and floating Salvinia hastata. The major threats to Sakalava Rail appear to be habitat loss caused by wetland conversion to rice fields and by fires, disturbance by fishermen and people from local villages, and hunting. Other processes that may alter the ecological character of wetlands and so affect their suitability for Sakalava Rails, such as hydrological change or the effects of exotic fish or vegetation, remain to be investigated.

Design and Performance of Experimental Constructed Wetlands in Uganda, Planted with Cyperus Papyrus and Phragmites Mauritianus

The viability of the use of constructed wetlands planted with indigenous Cyperus papyrus and Phragmites mauritianus plants for the purification of pre-settled municipal wastewater in tropical environments was investigated in concrete lined constructed wetlands for a period of 11 months. BOD and total suspended solids concentrations in the effluents from both systems were below 20 mg/l and 25 mg/l, respectively. In the C. papyrus systems, the removal rates for COD, NH4+ and o-PO4− averaged to 3.75, 1.01 and 0.05 (g/m2.day), respectively. In P. mauritianus units, the rates were 1.52, 0.97 and 0.068 (g/m2.day), respectively. A high degree of faecal coliform removal was attained at longer retention times in the two systems.

Additional chromosome numbers and meiotic behaviour in tropical African grasses from western Zaïre

Chromosome numbers are reported for 88 accessions of grasses from western Zaïre belonging to 31 genera and 65 species. First chromosome counts are reported for the genera Paratheria, Robynsiochloa, and Ystia and for the following species: Phragmites mauritianus, Sporobolus congoensis, Sporobolus sanguineus, Brachiaria kotschyana. Digitaria polybotrya, Entolasia oliracea, Panicum brazzavillense, Panicum spongiosum, Paratheria prostrata, Setaria thollonii, Andropogon brazzae, Andropogon patris, Robynsiochloa purpurascens, Schizachyrium platyphyllutn, Schizachyrium thollonii, and Ystia stagnina. Chromosome numbers that differ from previously reported records are given for Sporobolus festivus, Digitaria diagonalis var. hirsuta, Digitaria longiflora, Panicum griffonii, Panicum sadinii, and Rhynchelytrum repens.