H. Pakker et al., TEMPERATURE RESPONSES AND EVOLUTION OF THERMAL TRAITS IN CLADOPHOROPSIS-MEMBRANACEA (SIPHONOCLADALES, CHLOROPHYTA), Journal of phycology, 30(5), 1994, pp. 777-783
Temperature tolerances and relative growth rates were determined for d
ifferent isolates of the tropical to warm temperate seaweed species Cl
adophoropsis membranacea (C. Agardh) Boergesen (Siphonocladales, Chlor
ophyta) and some related taxa. Most isolates of C. membranacea survive
d undamaged at 18 degrees C for at least 8 weeks. Lower temperatures (
5 degrees-15 degrees C) were tolerated for shorter periods of time but
caused damage to cells. All isolates survived temperatures up to 34 d
egrees C, whereas isolates from the eastern Mediterranean and Red Sea
survived higher temperatures up to 36 degrees C. Growth occurred betwe
en 18 degrees and 32 degrees C, but an isolate from the Red Sea had an
extended growth range, reaching its maximum at 35 degrees C. Struvea
anastomosans (Harvey) Piccone & Grunow, Cladophoropsis sundanensis Rei
nbold, and an isolate of c. membranacea from Hawaii were slightly less
cold- tolerant, with damage occurring at 18 degrees C. Upper survival
temperatures were between 32 degrees and 36 degrees C in these taxa.
Temperature response data were mapped onto a phylogenetic tree. Tolera
nce for low temperatures appears to be a derived character state that
supports the hypothesis that C. membranacea originated from a strictly
tropical ancestor. Isolates from the Canary Islands, which is near th
e northern limit of distribution, are ill adapted to local temperature
regimes. Isolates from the eastern Mediterranean and Red Sea show som
e adaptation to local temperature stress. They are isolated from those
in the eastern Atlantic by a thermal barrier at the entrance of the M
editerranean.