| Abstract |
In the present PhD thesis, the polychaete community assemblages and the genetic population structure of the abundant species Hermodice carunculata from two hard substrate sites in Crete are investigated. Samples were collected in two successive years, in 2007 and 2008 from Alykes and Elounda, following the NaGISA sampling protocol. According to this protocol in each sampling sites 5 replicates units are collected: (i) from the 3 intertidal sub-zones and, (ii) from 5 subtidal depths. Sample collection was made by means of an underwater suction device. During the sampling procedure, it was made clear that a new sampler should be designed, developed and tested. The new sampler is called ManOSS (Manually Operated Suction Sampler) and it combines attributes from both suction samplers and slurp guns. The preliminary results showed that ManOSS has important advantages over the other two sampler types, which were hitherto in use. The analyses from community level showed that both sampling sites can be considered as representative for the Mediterranean Sea, under certain assumptions. Using the taxonomic distinctness indices (average and variation), randomization tests were performed. The results from those tests indicated that at small spatial observation scales (replicate unites and sampling depth), subtidal polychaete assemblages of the syllids seem to be formed at random from the pool of species hosted in the larger observational scales (e.g. sampling sites and Mediterranean Sea). The latter suggests that local processes such as species interaction are the major factor shaping these assemblages. The only factor that seems to impact the regional pattern of the Mediterranean intertidal sites, based on their polychaete inventories, was the ID of the data sets. This factor, however, inevitably includes a whole group of other factors which imply variability and bias in how research projects are carried out, from the sampling design through to data collection and analysis. For the genetic population analysis 80 individuals from Hermodice carunculata (40 from each sampling site) were analyzed. A significant divergence in haplotype distribution was recorded since only one was found to be shared in common by the two sampling sites while the others were equally allocated to both sites. Certainly, the values calculated for the population divergence of H. carunculata and beta diversity, derived from the whole polychaete taxo-communities, were almost identical, a fact supporting the hypothesis that the intra-specific genetic population structure of a single species may potentially be a sensible indicator of the ecological divergence of the community structure between the sampling sites.
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Οικολογικά πρότυπα και συμβολή στη μελέτη της γενετικής διαφοροποίησης των πολυχαιτών σε περιοχές σκληρού υποστρώματος στην Κρήτη
