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Title: Latitudinal Differences in Thermal Tolerance among Microscopic Sporophytes of the Kelp Lessonia nigrescens (Phaeophyta: Laminariales) 
Author: Martinez, Enrique A.
Date: 1999-01
Publisher: University of Hawai'i Press
Citation: Martinez EA. 1999. Latitudinal differences in thermal tolerance among microscopic sporophytes of the kelp Lessonia nigrescens (Phaeophyta: Laminariales). Pac Sci 53(1): 74-81.
Abstract: The strong temperature increase during the 1982/1983 El Nino
event caused local extinction of many species in large coastal zones of northern
Chile and Peru. One brown algal species affected by massive mortality was the
intertidal kelp Lessonia nigrescens Bory, with a latitudinal distribution from
Cape Horn (55° S) to Peru (12° S). Between extreme localities of this distribution,
mean annual seawater temperatures may differ by around lO C. After the
massive mortality of 1982/1983, some populations survived in a few localities of
northern Chile, such as Iquique (20° S). I tested the hypothesis that these populations
represent thermal ecotypes. Those from the north, close to the El Nino impacted
zone, should tolerate higher temperatures than southern populations.
Microscopic sporophytes, cultivated from spores of plants collected in localities
at the north, center, and south of Chile, were subjected to three temperature
regimes. Two of them included the same average temperature, but different
extreme values. Comparisons of thermal tolerance in the microscopic progeny
from plants of the three Chilean localities showed that, at higher incubation
temperatures, central and northern thermal ecotypes do have higher survival
and growth rates than the ecotypes from the south. At lower incubation temperatures,
the growth trend was reversed. Also, as suggested in the literature,
sporophytic juveniles seem less tolerant than gametophytic microthalli. However,
the differences in tolerance between northern and southern thermal ecotypes
do not fully explain the survival of high seawater temperatures such as
those of the 1982/1983 El Nino event by the northern populations.
ISSN: 0030-8870

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