RESUMEN
Interspecific hybridization is an important and common evolutionary mechanism, but field-based evaluations of changes in realized niches and zonation patterns of native and exotic hybrids relative to those of their parental plant species are rare. Would native hybrids forming hybrid zones between their parental species show realized niches similar to that of their parents, whereas would exotic hybrids show larger realized niches than their parents, and alter zonation patterns of native species? To address these questions, we examined key sediment characteristics in plots representing realized niches of native Sarcocornia hybrids, invasive Spartina hybrids and parental species in 14 salt marshes from four estuaries in the Gulf of Cadiz, Southwest Iberian Peninsula. In one representative marsh, the presence of plant taxa relative to intertidal plant zonation was recorded. Results documented that native and fertile hybrids of Sarcocornia had similar realized niche dimensions as their parental species and co-occurred with other plant species, supporting community diversity. However, exotic sterile hybrids of Spartina had realized niche dimensions lower than those of their parental species and occurred in monocultures. The native hybrids played a community structuring role, whereas the exotic Spartina hybrids were a disruptive influence that changed native halophyte zonation pattern and decreased diversity. This negative functional role could intensify if the sterile hybrids evolve and become fertile. Our study suggests the ecological niche dimension concept is an important tool for understanding species roles in ecosystems, incorporating many ideas from the individual to ecosystem levels.
Asunto(s)
Ecosistema , Plantas Tolerantes a la Sal , Hibridación Genética , Poaceae , HumedalesRESUMEN
Sedimentary abiotic environment, and concentration and stock of nine metals were analyzed in vegetation and sediments to evaluate the phytoremediation capacity of restored Spartina maritima prairies in the highly polluted Odiel Marshes (SW Iberian Peninsula). Samples were collected in two 10 -m long rows parallel to the tidal line at two sediments depths (0-2 cm and 2-20 cm). Metal concentrations were measured by inductively coupled plasma spectroscopy. Iron, aluminum, copper, and zinc were the most concentrated metals. Every metal, except nickel, showed higher concentration in the root zone than at the sediment surface, with values as high as ca. 70 g Fe kg(-1). The highest metal concentrations in S. maritima tissues were recorded in its roots (maximum for iron in Spartina roots: 4160.2 +/- 945.3 mg kg(-1)). Concentrations of aluminum and iron in leaves and roots were higher than in superficial sediments. Rhizosediments showed higher concentrations of every metal than plant tissues, except for nickel. Sediment metal stock in the first 20 cm deep was ca. 170.89 t ha(-1). Restored S. maritima prairies, with relative cover of 62 +/- 6%, accumulated ca. 22 kg metals ha(-1). Our results show S. maritima to be an useful biotool for phytoremediation projects in European salt marshes.