Life history variation in cupuladriid bryozoans from either side of the Isthmus of Panama

Abstract

Cupuladriid bryozoans are able to produce new colonies both sexually through the production of larvae and asexually via fragmentation. The prevalence of asexual propagation and the physical and biological processes of fragmentation in cupuladriid species are currently little understood. In a large survey comprising collections of nearly 32 000 cupuladriids from either side of the Isthmus of Panama, patterns of cupuladriid species richness, occurrence and abundance were measured together with levels of asexual propagation, fragmentation and regeneration. The Caribbean side is characterised by greater cupuladriid diversity and dominance of the genus Cupuladria over Discoporella while the eastern Pacific coast is characterised by lower cupuladriid diversity and complete dominance of Discoporella. Life history variation was not found to be constrained by phylogeny and no systematic differences were found in life history or morphologies between Cupuladria and Discoporella to explain the patterns in generic dominance across the isthmus. Nonetheless, striking differences occur in life history strategies across the isthmus. Eastern Pacific species tend to be large, flat and lightly calcified, resulting in high levels of fragmentation and hence asexual propagation. Conversely, Caribbean species produce a wider range of morphologies, including small, highly domed and highly calcified colonies that protect from fragmentation. By correlating colony morphologies with reproductive life histories within species, we show that morphologies, particularly colony strength and size, control levels of fragmentation and thus mode of propagation in cupuladriids. Life history strategies that promote asexual propagation are found to track levels of primary productivity both between oceans across the isthmus and between regions within oceans.

Relation of form to life habit in free-living cupuladriid bryozoans

“…The material used in the present study was the same collection of recent cupuladriid colonies used in an analysis of life history variation in species across the Isthmus of Panama (O'Dea et al 2004). Since then, cupuladriid taxonomy has advanced (Herrera-Cubilla et al 2006, 2008 and so each of the nearly 20 000 colonies were re-classified to species level.…”

“…All colonies were used if the total sampled population of a species was <100 colonies. Colonies used for morphometric analysis were weighed to determine mean calcification index for each species following the methods of O'Dea et al (2004).…”

“…5). All colonies were identified according to Herrera-Cubilla et al (2006, 2008; see O'Dea et al (2004O'Dea et al ( , 2007 for collection methods.…”

“…Morphology is tightly coupled to mode of propagation. Small, robust colonies rarely fragment, and their colonies are sexually recruited; large, thinly calcified and indeterminately growing species tend to readily fragment, and their colonies are most often clonal (O'Dea et al 2004). …”

Evidence of El Niño/La Niña–Southern Oscillation Variability in the Neogene-Pleistocene of Panama Revealed by a New Bryozoan Assemblage-Based Proxy

“…Recent bryozoans from the Gulf of Panama (TEP), the Gulf of Chiriquí (TEP), San Blas (SWC), and Bocas del Toro (SWC) were obtained from dredge and trawl collections between the years 1996 and 2000 (O'Dea et al 2004, O'Dea et al 2007aFig. 2).…”