Interspecific interactions through 2 million years: are competitive outcomes predictable?

Area of Science:

• Paleontology
• Evolutionary Biology
• Marine Ecology

Background:

• Ecological interactions are crucial for survival and reproduction, but difficult to study in extinct populations.
• Understanding temporal variation in competitive interactions is key to grasping long-term evolutionary changes.

Purpose of the Study:

• To investigate the outcomes of spatial competition in an extinct marine community over evolutionary timescales.
• To analyze competitive dynamics in encrusting cheilostome bryozoans from the Wanganui Basin, New Zealand, over a 2-million-year period.

Main Methods:

• Analysis of encrusting cheilostome bryozoans from the Wanganui Basin (Pleistocene to Recent).
• Statistical assessment of interspecific competitive encounters to identify consistent winners and losers.
• Examination of spatial distribution and interaction patterns of conspecific colonies.

Main Results:

• A subset of species consistently won or lost interspecific competitive encounters.
• Most species maintained stable competitive abilities over 2 million years, while a minority showed fluctuating success.
• Conspecifics exhibited spatial clustering, with most interactions resulting in growth cessation (stand-offs) rather than displacement.
• Competitive ability was found to have no correlation with ecological dominance.

Conclusions:

• Long-term ecological competition can result in stable winner/loser dynamics within a community.
• Species competitive strategies can change over evolutionary time, but many remain stable.
• Ecological dominance is not solely determined by direct competitive interactions.