Bryozoans offer one of the few systems in which competitive interactions for living space can be studied in the fossil record. Here, we describe the outcome of competitive overgrowths in a 3-million-year-old bryozoan palaeocommunity encrusting shells of the bivalve Anomia simplex from the lower Tamiami Formation in Florida (upper Pliocene, Piacenzian). We found that win–lose overgrowths are more common than stand-offs in interspecific encounters, while stand-offs are more common than win–lose overgrowths in intraspecific encounters. We observed more intraspecific encounters and fewer interspecific interactions than expected under a null hypothesis, suggesting that bryozoans of the same species are likely to be clustered. For some species, intraspecific encounters are more likely to result in the apparent fusion of the two colonies, with the development of rows of kenozooids along the contact edge, probably reflecting relatively low dispersal. We also identified some clear winners and some clear losers. A negative correlation was found between the number of colonies observed and the probability of winning for a species, resulting in a dominance of loser species in the assemblage, a pattern previously described as typical for early colonizers of hard substrates. Our results also confirm the finding of earlier studies that having large zooids and, subordinately, multilayered growth are key traits for success in overgrowth competition, with angle of encounter also having an effect for both poor and good competitors that take advantage of ‘attacking’ colonies of other species from the rear and the flank.

Sneaking up on ‘enemies’: alleviating inherent disadvantages in competitive outcomes in a nearly 3-million-year-old palaeocommunity from Florida, USA

Di Martino E.
Primo
;
2020-01-01

Abstract

Bryozoans offer one of the few systems in which competitive interactions for living space can be studied in the fossil record. Here, we describe the outcome of competitive overgrowths in a 3-million-year-old bryozoan palaeocommunity encrusting shells of the bivalve Anomia simplex from the lower Tamiami Formation in Florida (upper Pliocene, Piacenzian). We found that win–lose overgrowths are more common than stand-offs in interspecific encounters, while stand-offs are more common than win–lose overgrowths in intraspecific encounters. We observed more intraspecific encounters and fewer interspecific interactions than expected under a null hypothesis, suggesting that bryozoans of the same species are likely to be clustered. For some species, intraspecific encounters are more likely to result in the apparent fusion of the two colonies, with the development of rows of kenozooids along the contact edge, probably reflecting relatively low dispersal. We also identified some clear winners and some clear losers. A negative correlation was found between the number of colonies observed and the probability of winning for a species, resulting in a dominance of loser species in the assemblage, a pattern previously described as typical for early colonizers of hard substrates. Our results also confirm the finding of earlier studies that having large zooids and, subordinately, multilayered growth are key traits for success in overgrowth competition, with angle of encounter also having an effect for both poor and good competitors that take advantage of ‘attacking’ colonies of other species from the rear and the flank.
2020
Bryozoa
Cheilostomata
ecological interactions
overgrowths
spatial competition
File in questo prodotto:
File Dimensione Formato  
Di Martino et al., 2020_Lethaia.pdf

accesso aperto

Tipologia: Versione Editoriale (PDF)
Licenza: Creative commons
Dimensione 4.68 MB
Formato Adobe PDF
4.68 MB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11769/598329
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 5
  • ???jsp.display-item.citation.isi??? 5
social impact