Preprint volume - SIBM

Pre-print Volume - Oral presentations
Topic 2: MARINE ORGANISMS AND ECOSYSTEMS AS MODEL SYSTEMS
Results – The mean March SST in Agrigento in 1985-2007 is 14.6 °C and this
temperature was chosen as a reference temperature, characterizing the minimum
temperature conditions needed by E. punctata to start its reproductive cycle.
The SST series of Agrigento, Catania and Messina are similar in shape with the highest
value in 1990, the peak of a period of temperatures above the reference level from
1988 to 1991. Further peaks above the reference level are 1994, 1998 and then again
2001. In Agrigento, Catania and Messina the species has been recorded for the whole
considered time frame (despite data suggest that the colonization of Messina took place
later than the other southern Sicilian localities).
In Vibo Valentia, the temperature trend is similar in shape to the stations in Sicilia with
slightly lower temperatures. The first record of E. punctata is in 1997 (D’Anna, 1997).
The hypothesis is that the temperature peak in 1990 allowed the settling of
reproductive populations along the Tyrrhenian coastline north of Sicilia and that
populations slowly spread northwards until the first records in Vibo (almost 100 km
from Messina). The time lag between the first evidence of adequate temperatures and
the recording of populations depends on how far new stations are from already
established ones and the time needed by larvae to travel, settle and develop
reproductive populations.
In Napoli, temperature peaks above the reference level happened in 1990, 1994, 1998
and 2001 like for more southern stations but the first record of the species is in 2001 in
Salerno (80 km coastline south of Napoli, Soppelsa et al., 2004) and 2004 in Napoli.
Therefore, the temperature peak in 2001 allowed the colonization of this stretch of
coastline. The explanation for the lack of records in the 1990s, despite adequate
temperatures were present, could be explained with the time lag phenomenon described
for Vibo Valentia: the settling of reproductive populations requires time since the
colonization is a progressive phenomenon along the coastline.
In Fiumicino the mean temperature in March is often close to the reference level, but it
is never above it until 2007. The first records of E. punctata date to 2008 (P.G. Albano,
unpublished data). The analysis of a longer time series may confirm the phenomenon
already described for Vibo Valentia and Napoli.
In Argentario and Livorno the mean temperature in March is never above the reference
level and the species is, consistently, not recorded so far.
A similar interesting phenomenon has taken place in Puglia, despite driven by different
currents. In Gallipoli, the first peak above the reference level takes place in 2001, but
already in 1998 and 1999 the temperature is close to the reference level. The first
records of E. punctata can be traced back to 2000 (Albano & Trono, 2008). If a
continuous flow of pelagic larvae from Greece could be hypothesized, then in the late
1990s the temperature is close to the adequate one for colonization and the first records
are consistently found in 2000. Otranto, despite closer to the supposed origin of Puglia
populations, is colder than Gallipoli. There is a single temperature peak in 2001, but
other years are well below the reference level.
Conclusions – It is clear that the range expansion of E. punctata is driven by currents
transporting pelagic larvae but that the establishment of reproductive populations need
temperatures high enough to allow its reproductive cycle.
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
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