Bryozoans and serpuloideans in skeletobiont communities from the Pleistocene of Sicily: spatial utilisation and competitive interactions

Sessile encrusters with mineralised skeletons in the fossil record generally retain their original spatial relationships to the substrate and each other. Being short living and not significantly time averaged, communities on shelly substrates represent excellent systems to study such relationships. Bryozoan and serpuloidean skeletobionts on molluscs and rhodolites from Lower Pleistocene localities in Sicily have been studied. Species composition and specimen sizes testify to a short exposure of the shells on the sea floor. Skeletobiont community structure is characterised by the dominance of a few species (5 bryozoans out of 87 and 3 serpuloideans out of 17). Substrate coverage is usually low (<5%), rarely reaching 50-60% or more. On bivalves, skeletobiont distribution does not exhibit a clear trend for inner/outer sides or left/right valves. Oriented growths, differential patterns in microenvironment utilisation of the substrate and spatial competition have been analysed. Several of the recorded overgrowths resulted from superimposition of specimens growing on skeletons of previous, already dead encrusters. True competitive interactions mainly involved bryozoans and only a few serpuloideans. Within bryozoans interspecific encounters usually led to overgrowth or abutment whereas intraspecific encounters commonly resulted in standoffs and growth side by side in cheilostomes, and to fusion of colonies in some cyclostome species.

[1]  S. Kidwell,et al.  Symbiosis, competition, and physical disturbance in the growth histories of Pliocene cheilostome bryoliths , 2007 .

[2]  Mark A. Wilson,et al.  Palaeoecology and evolution of marine hard substrate communities , 2003 .

[3]  Mark A. Wilson,et al.  A New Terminology for Marine Organisms Inhabiting Hard Substrates , 2002 .

[4]  E. Kupriyanova,et al.  Serpulidae (Annelida, Polychaeta) of the Arctic Ocean , 1997 .

[5]  H. Lescinsky.  Epibiont communities: Recruitment and competition on North American Carboniferous brachiopods , 1997, Journal of Paleontology.

[6]  F. Mckinney.  Encrusting organisms on co-occurring disarticulated valves of two marine bivalves: comparison of living assemblages and skeletal residues , 1996, Paleobiology.

[7]  F. Mckinney.  One hundred million years of competitive interactions between bryozoan clades: asymmetrical but not escalating , 1995 .

[8]  F. Mckinney.  Taphonomic effects and preserved overgrowth relationships among encrusting marine organisms , 1995 .

[9]  H. Lescinsky.  Taphonomy and paleoecology of epibionts on the scallops Chlamys hastata (Sowerby 1843) and Chlamys rubida (Hinds 1845) , 1993 .

[10]  M. Ward,et al.  Distribution of encrusting bryozoans and other epifauna on the subtidal bivalveChlamys opercularis , 1991 .

[11]  S. Lidgard,et al.  Growth in encrusting cheilostome bryozoans: I. Evolutionary trends , 1989, Paleobiology.

[12]  M. Ward,et al.  Assessment of space utilisation in a subtidal temperate bryozoan community , 1989 .

[13]  W. Miller,et al.  Temporal change as an aspect of biogenic shell utilization and damage, Pleistocene of North Carolina, U.S.A , 1986 .

[14]  K. A. Rasmussen,et al.  Taphonomy of Holocene cryptic biotas from St. Croix, Virgin Islands: Information loss and preservational biases , 1985 .

[15]  J. Jackson.  Overgrowth competition between encrusting cheilostome ectoprocts in a jamaican cryptic reef environment , 1979 .

[16]  J. Jackson.  Competition on Marine Hard Substrata: The Adaptive Significance of Solitary and Colonial Strategies , 1977, The American Naturalist.

[17]  A. Rosso,et al.  Cooling evidence from Pleistocene shelf assemblages in SE Sicily , 2000, Geological Society, London, Special Publications.

[18]  M. Weedon.  Tube microstructure of Recent and Jurassic serpulid polychaetes and the question of the Palaeozoic spirorbids , 1994 .

[19]  Leo W. Buss,et al.  Population biology and evolution of clonal organisms , 1988 .

[20]  J. Rubin.  Mortality and avoidance of competitive overgrowth in encrusting Bryozoa , 1985 .

[21]  J. Jackson,et al.  Biological Determinants of Present and Past Sessile Animal Distributions , 1983 .

[22]  J. Harmelin.  Le sous-ordre des Tubuliporina (Bryozoaires Cyclostomes) en Méditerranée. Ecologie et systématique , 1976 .