COEXISTENCE AND COLLAPSE - AN EXPERIMENTAL INVESTIGATION OF THE PERSISTENT COMMUNITIES OF A PROTIST SPECIES POOL

Citation
Aj. Weatherby et al., COEXISTENCE AND COLLAPSE - AN EXPERIMENTAL INVESTIGATION OF THE PERSISTENT COMMUNITIES OF A PROTIST SPECIES POOL, Journal of Animal Ecology, 67(4), 1998, pp. 554-566
Citations number
40
Categorie Soggetti
Ecology,Zoology
Journal title
ISSN journal
00218790
Volume
67
Issue
4
Year of publication
1998
Pages
554 - 566
Database
ISI
SICI code
0021-8790(1998)67:4<554:CAC-AE>2.0.ZU;2-7
Abstract
1. Using protists in laboratory microcosms we investigated the long-te rm coexistence of combinations of species from a six species set to ad dress the following questions: (i) What proportion of the possible com munities from the species pool are persistent? (ii) From how many init ial states are each of these persistent communities obtained? (iii) Wh at are the impacts of individual species on community collapse? (iv) C an the behaviour of the system be characterized by a simple set of rul es? (v) To what extent does knowledge of the results from the pairwise species combinations allow prediction of the outcomes of the more spe cies-rich sets? 2. Replicated microcosms were set up with each of the 63 possible combinations of species from a pool of six protist species (three bacterivores, two predators and one omnivore) along with a mix ed bacterial flora. Microcosms were maintained, with nutrient replenis hment, for over 100 days until a constant species composition was reac hed. 3. Forty-seven of the 63 starting combinations showed a repeatabl e collapse to one of eight communities (including the 'empty' communit y - containing just bacteria). The number of starting combinations lea ding to each of these persistent communities varied from 17 down to on e. Extinction rates were higher in more species-rich systems. 4. The e ffects of each species in determining the composition of the persisten t community were characterized as to whether they were present in the final set or not, and whether their occurrence in the starting combina tion had any effect on the eventual presence or absence of others. Und er this classification the larger species seem to be more influential in shaping the final community. 5. The collapse from the initial speci es composition to that at the end could be stated in terms of four sim ple rules in 34 of the 47 starting combinations for which a persistent community could be defined. 6. Using the outcomes from the single-spe cies and two-species starting sets only, the eventual states to which the larger communities collapsed could be correctly predicted in 27 ou t of the 31 starting combinations containing three or more species for which persistent communities could be defined.