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The Role of the Territory in the Ecology of the Intertidal Limpet Lottia Gigantea (Gray)
Author(s) -
Stimson John
Publication year - 1973
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1935568
Subject(s) - limpet , intertidal zone , ecology , biology , population , algae , tide pool , gastropoda , algal mat , grazing , abundance (ecology) , demography , sociology
The marine mollusk Lottia gigantea, a large grazing limpet of the upper intertidal zone, grazes algal film from a territory which it defends against intrusions by conspecifics and other grazers as well as the gradual encroachment of sessile organisms. The areas of the territories are correlated with the length of the resident Lottia, but for a given size of Lottia the areas vary greatly at different study sites. The thickness of the algal film charcteristic of the territory fluctuates, being greatest in spring. Experimental removal of abundant algal film from some territories in spring was followed by enlargement of these territories relative to controls. Growth rates of Lottia are positively correlated with the thickness of the algal film in their territories. The smaller limpets (1—2 cm in length) of the genus Acmaea are able to crop the algal film more closely than Lottia and will remove almost all the algal film from a territory if the territory—resident is removed. Experiments to determine whether territorial behavior sets a limit to the abundance of Lottia showed that removal of large individuals from the smooth surfaces they characteristically graze allowed smaller Lottia to move from less suitable sites and establish territories on the smooth surface. Experimental reduction of abundant algal film in enclosures where Lottia were living at high densities was followed by a decrease in the numbers of Lottia relative to controls. The decline in numbers of Lottia over 3 years in a population at the principal study site was due to a decrease in recruitment from the plankton or a low rate of survival of newly settled animals but was not a result of mortality induced by territorial defence. Territorial behavior of Lottia apparently evolved as an adaptation that allows the defence of a thick algal film necessary for growth of such a large grazing limpet. Defense of territories also keeps the grazing area free of sessile organisms that compete for space.