Biología de la reproducción de las especies de Spartina presentes en las marismas del Golfo de Cádiz

Abstract

The main objective of present work was to study the reproductive biology of the Spartina taxa present in the salt marshes of the Gulf of Cádiz (Southwest lberian Península): native Spartina marítima (Curtís) Fernald., invasive Spartina densiflora Brongn., invasive Spartina patens (Aiton) Muhl., and the reciproca! transgressive hybrids between S. densif/ora and S. marítima: Spartina x onubensis Sánchez Gullón, M.O. Infante & B. Gallego subsp. onubensis and Spartina x onubensis subsp. tartessiana Sánchez Gullón, B. Gallego & M.O. Infante . Present PhO dissertation includes seven studies about these taxa in salt marshes along the Gulf of Cádiz: Our results document discriminating trait variables from populations of interspecific hybrids from Spartina marítima and S. densiflora that can be used to distinguish them from their parental species and each other. From these findings and the verification of type specimens, we describe two new nothotaxa, Spartinax onubensis subsp. onubensis and Spartina x onubensis subsp. tartessiana, and develop taxonomic keys for identification of the tour studied taxa. Spartina marítima was able to set moderate numbers of highly viable caryopses, and the percentage of spikelets with ali their stamens exerted was positively correlated with the percentage of mature caryopses. We found interannual variation for reproductive traits of S. densiflora which also differed among habitats. Our results indicate neither hybrid nor S. patens produced any mature caryopses. Spartina marítima and S. densiflora , presented protogyny, and were self-compatible. S. marítima fruit-set was associated positively with sexes overlap in its inflorescence. The lower rates of fruit set that presents S. marítima in comparison with S. densif/ora are explained by sorne disadvantages in its sexual breeding system such as its low rates of pollen dispersa! that reduced the chance of crossing, and its low degree of overlap between the two sexual phases in an inflorescence that reduced the chances of geitonogamy. Wet-stored Spartina seeds were able to maintain viability for months, while seeds under dry storage rapidly lost viability. S. densiflora spikelets showed greater ability than S. marítima to remain afloat. Native S. marítima did not establish transient or persistent seed banks, while invasive S. densiflora established transient seed banks. The germination of Spartina marítima and S. densiflora was inhibited and delayed at high salinities. S. densiflora was more tolerant of salinity at germination than S. marítima. S. densif/ora was able to germinate at hypersalinity and its germination percentage decreased at higher salinities compared to S. marítima. In contrast, S. marítima showed higher salinity tolerance in relation to seedling growth. Contrasting results were observed with differences in the tidal elevation of populations. Germination percentage of Spartina marítima and S. densiflora was not affected by any metal at any tested concentration (Cu, Zn and Ni from O to 2000 µM). S. marítima seedlings were more tolerant to metals than S. densiflora. Comparing our results to metal concentrations in the field, we expect invasive S. densiflora seedling development may be impacted in most metal-polluted areas in Odiel and Tinto Estuaries.