MEPS 540:13-26 (2015)  -  DOI: https://doi.org/10.3354/meps11526

ABSTRACT: To understand and predict patterns of diversity loss in response to global changes, combining historical ecological datasets with modern experimentation can be a valuable approach. In an intertidal seagrass community in northern Florida, USA, we used current and historical quantitative data and a factorial field experiment to investigate diversity changes within and across trophic levels from 1959 to 2013. Over this time period, an 80% reduction in habitat area due to changes in sediment deposition coincided with the disappearance of 2 of 6 large predatory gastropod species and a decline in the relative abundance of specialist relative to generalist gastropods. To investigate the effects of these compositional changes, we experimentally examined trophic interactions among community members in mimicked current and historical food webs. We found that the top predator (horse conch Triplofusus giganteus) had the greatest predatory effect on the 2 species that had disappeared from the community (lace murex Chicoreus florifer and true tulip Fasciolaria tulipa) and that lace murex had the greatest predatory effect on basal resources (bivalves). Therefore, the community not only experienced a reduction in the number of interaction pathways due to species loss, but also loss of the strongest top-down effects among trophic levels. Given that strong interactions are often unstable, this result may reflect loss of the least stable interactions in response to habitat loss. Whether interaction strength can predict extirpation vulnerability in ecosystems merits further empirical and theoretical investigation.

KEY WORDS: Biodiversity · Historical ecology · Non-random diversity change · Predator-prey interactions · Seagrass · Gastropods