Preprint volume - SIBM

Ancestry coefficient
100%
80%
60%
40%
20%
0%
Pre-print Volume - Oral presentations
Topic 2: MARINE ORGANISMS AND ECOSYSTEMS AS MODEL SYSTEMS
CLUSTERS
Adriatic Ionian Algal isolats Tyrrhenian Catalan Balearic Atlantic
Fig. 1 – Population structure based on 7 microsatellite loci in A. minutum. Assigment of 116
individuals to 4 genetically distinct groups. Each individual is represented by a vertical bar
coloured according to the assigned group.
Struttura genetica di popolazione basata sull’analisi di 7 loci microsatelliti in A. minutum.
Assegnazione di 116 individui a 4 gruppi geneticamente diversi. Ciascun individuo è
rappresentato da una barra verticale colorata in base al gruppo di assegnazione.
Conclusions – The results obtained by the screening of the microsatellite markers were
different from those obtained by previous analyses of ribosomal markers (Penna et al.,
2008; Lilly et al., 2005) conferming that ribosomal DNA was not informative to
estimate genetic diversity within A. minutum populations from different coastal areas.
In the Mediterranean Sea, it has been possible to identify four distinct genetic clusters
corresponding to 4 A. minutum populations through the analysis of 7 microsatellite
loci. The results showed a strong phylogeographical structure probably due to the
presence of physical and hydrographical barriers. Population isolation resulting from
the limited connectivity leaded to a low gene flow among A. minutum populations. This
isolation didn’t lead to a loss of variability (the gene diversity values were all above
62%). The presence of allochtonous and mixed genotypes within each population could
be explained (i) by assuming that the allochtonous genotypes can belong to original
populations that have re-colonized the Mediterranean after the Messinian Salinity
Crisis, or (ii) by both hypothesis of natural and/or human assisted way of dispersal, as
ballast water or aquaculture (Casabianca et al., unpublished data).
In this case study of the harmful microalgal species A. minutum, the application of the
microsatellite markers were useful and more sensitive tool for diagnostic screening of
different populations within this species that is responsible of potential harmful
outbreaks, thus giving a tool for the improved control and management activities of the
HAB events in the Mediterranean Sea.
References
EXCOFFIER L., LAVAL G., SCHNEIDER S. (2005) - Arlequin ver. 3.1: an integrated software
package for population genetics data analysis. Evol. Bioinform. Online, 1: 47-50.
GOUDET J. (2001) - FSTAT, a program to estimate and test gene diversities and fixation indices
(version 2.9.3.2).
LILLY E.L., HALANYCH K.M., ANDERSON D.M. (2005) - Phylogeny, biogeography, and species
boundaries within the Alexandrium minutum group. Harmful Algae, 4: 1004-1020.
NAGAI S., MCCAULEY L., YASUDA N., ERDNER D., KULIS D., MATSUYAMA Y.,
ITAKURA S., ANDERSON D.M. (2006) - Development of microsatellite markers in the toxic
dinoflagellate Alexandrium minutum (Dinophyceae). Mol. Ecol. Notes, 6: 756-758.
PENNA A., FRAGA S., MASÒ M, GIACOBBE M.G., BRAVO I., GARCÉS E, VILA M.,
BERTOZZINI E., ANDREONI F., LUGLIÉ A.,VERNESI C. (2008) - Phylogenetic
relationships among the Mediterranean Alexandrium (Dinophyceae) species based on sequences
of 5.8S gene and Internal Transcript Spacers of the rRNA operon. Eur. J. Phycol., 43: 163-178.
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
114
Adriatic
Ionian
Catalan
Tyrrhenian