Ecophysiology of Pennisetum setaceum and three native grasses in the Canary Islands (ES)
Pennisteum setaceum (Asteraceae, EPPO Alert List) has proven very invasive in the dry tropics and subtropics. In the Canary Islands (ES), where it was introduced as an ornamental plant, P. setaceum has expanded along the roads from urbanized areas toward natural areas and is found in about 30% of the protected areas of Tenerife. Local administration bodies carry out eradication and control programs with variable success. P. setaceum has strongly invaded the protected areas of the coastal xerophytic scrub and the endemic communities dominated by Euphorbia canariensis and Euphorbia balsamifera. In these areas, P. setacerum first co-habits and then replaces the native grasses Hyparrhenia hirta, Cenchrus ciliaris and Aristida adscensionis. Several ecophysiological, architectural and reproductive traits between these three native grasses and P. setaceum were compared from two sites in Tenerife Island in order to test the invasive potential of P. setaceum under contrasting conditions.
It appeared that P. setaceum and the native grasses differed in all measured traits at the two sites considered. P. setaceum remained green for longer than the native grasses and its regrowth started 1-2 months earlier. Specific leaf area was lower in P. setaceum than in the native grasses. Although this reduces carbon assimilation per unit area, it also reduces transpiration, increasing water use efficiency and contributes to the maintenance of high relative water content. Leaf N in P. setaceum was lower than in the native grasses indicating higher nitrogen use efficiency. P. setaceum physiological responses were more buffered to seasonal and site variations whereas the natives had the largest seasonal variations. This buffering might indicate some phenotypic plasticity. The large invasive potential of P. setaceum, in concert with the projected global change strongly suggests risks for the conservation of the endemic flora and remaining native communities in the Canary Islands in the future.
Sources
González-Rodríguez AM, Baruch Z, Palomo D, Cruz-Trujillo G, Jiménez MS, Morales D (2010) Ecophysiology of the invader Pennisteum setaceum and three native grasses in the Canary Islands. Acta Oecologica 36, 248-254.