Aim  Hybridization is a common and potent mechanism of plant evolution that has the potential to be evolutionary significant in its own right, and hybrids are common between invasive and native congeneric species. Our aims were to document the existence and nature of new Spartina hybrids arising between introduced Spartina densiflora and native S. maritima in tidal marshes of the Iberian Peninsula, to examine the actual and potential range of hybrids in the intertidal zone, and to analyse the seed set of hybrids. Location  South‐West Iberian Peninsula. Methods  Hybrids were characterized using chloroplast and nuclear DNA, and ploidy assessments. The ecological tolerance of the hybrids was studied using vegetation surveys and transplant experiments. Results  We found that both parental species have been seed parents to hybrids and that all hybrids had an additive pattern of species‐specific nuclear markers consistent with F1 hybrids. Hybrid chromosome numbers varied between 2n = ca. 65 and 2n = ca. 94–97, while S. maritima had 2n = ca. 60 and S. densiflora had 2n = ca. 70. Hybrids grew in three discrete locations along the intertidal zone but were capable of growing throughout the ranges of both parental species in transplanted gardens, and in most cases, grew better than the parental species. While the potential exists for the origination of another invasive Spartina hybrid species, thus far hybrid plants are not fertile, limiting their ability to invade and spread. Main conclusions  We recommend the eradication of all of the currently quite limited hybrid cordgrass and to fight the S. densiflora invasion in the Iberian Peninsula to prevent the origination of a new invasive allopolyploid Spartina species.

No abstract

This study compares how Lantana camara, an invasive species, and L. peduncularis, an autochthonous one, cope with drought in Galapagos. Soil surface temperature was the abiotic environmental parameter that best explained variations in photosynthetic stress. Higher soil surface temperatures were recorded in the lowlands and in rain-shadow areas, which were also the driest areas. L. peduncularis, with a shallow root system, behaved as a drought-tolerant species, showing lower relative growth rates, which decreased with leaf water content and higher photosynthetic stress levels in the lowlands and in a northwest rain-shadow area in comparison with higher and wetter locations. Its basal and maximal fluorescences decreased at lower altitudes, reflecting the recorded drops in chlorophyll concentration. In contrast, L. camara with a deep root system behaved as a drought-avoiding species, showing leaf and relative water contents higher than 55% and avoiding permanent damage to its photosynthetic apparatus even in the driest area where it showed very low chlorophyll content. Its relative growth rate decreased more in dry areas in comparison to wetter zones than did that of L. peduncularis, even though it had greater water content. Furthermore, L. camara showed higher water contents, growth rate, and lower photosynthetic stress levels than L. peduncularis in the arid lowlands. Thus, L. peduncularis maintained lower maximum quantum efficiency of photosystem II photochemistry (F v /F m ) than L. camara even at sunrise, due to higher basal fluorescence values with similar maximal fluorescence, which indicated Ó Springer Science+Business Media B.V. 2006 permanent damage to PSII reaction centres. Our results help to explain the success and limitations of L. camara in the invasion of arid and sub-arid environments.

No abstract

No abstract