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The distribution and population biology of the triclad Phagocata vitta in a Welsh stream
Author(s) -
Armitage M. J.,
Young J. O.
Publication year - 1992
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1992.tb07489.x
Subject(s) - biology , abiotic component , ecology , abundance (ecology) , biotic component , population , reproduction , zoology , demography , sociology
The ecology of Phagocata vitta (Dugès) in a small mountain stream in North Wales was studied at monthly intervals over two years. The triclad occurred along the length of the stream but was abundant at only three of the 11 sampling sites. The ultimate factor influencing the abundance and distribution patterns was gradient and the proximate factor was the nature of the substratum; greatest numbers were found where the gradient was shallow and higher proportions of finer substrata and flora were present. The roles of other measured abiotic and biotic factors were not major. During the course of a year, low continual recruitment through sexual reproduction, and to a lesser extent through fissioning, took place, distinct cohorts could not be identified, the mean lengths of triclads stayed remarkably constant, and numbers fluctuated apparently erratically with no discernible seasonal pattern. Increases and decreases could not be attributed to changes in birth rates and death rates, respectively, and may have been due to irregular shifts in horizontal and vertical distribution. Factors controlling and regulating population size remain obscure.