Sean F. Craig

Positive flow dependence in the initial colonization of a fouling community: results from in situ water current manipulations

During late winter/early spring (1992–1993), a series of 12 tapered channels were placed subtidally in a Long Island, New York (U.S.A) estuary to examine total fouling community development. Rather than relying upon flow-dependent correlations among spatially segregated sites, these channels directly accelerated or decelerated the existing tidal currents ± 50% (ambient flow speeds ranged from 50 cm/s). In response to experimentally manipulated water flows over five months, the arborescent hydroid Obelia longissima Pallas (1766) accumulated onto Tygon tubing in direct proportion to mean free-stream flow speed, whereas barnacle (Balanus eburneus Gould) initial settlement and cumulative recruitment along plywood ceilings increased three-fold and five-fold, respectively, with a long-term doubling of water speed. These positive flow-dependent results directly contrast those from previous experiments in the same channel apparatus which failed to document any flow enhancement on the growth of suspension-feeding bivalves.

Kin or self-recognition? Colonial fusibility of the bryozoan Celleporella hyalina

Summary We estimated fusion frequency with respect to coancestry in the bryozoan Celleporella hyalina, whose briefly planktonic sexually produced larvae settle on algal substrata and proceed to form encrusting colonies by iterative budding. Frequency of fusion between paired colonies growing on an artificial substratum was positively correlated with coefficient of relatedness, with allorecognition ability increasing during the early stages of colonial growth after larval settlement. Parents repressed the growth of F1 progeny with which they had fused. The results are concordant with the Feldgarden‐Yund model of selection for self‐recognition, which regards fusion with kin as an inevitable source of error whose cost diminishes with increasing relatedness. Contrary to fusion compatibility, gametic compatibility is negatively correlated with coancestry, indicating a need for further research on the possibility of common or linked genetic control that has opposite effect at somatic and gametic levels.

Paradoxical polyembryony? Embryonic cloning in an ancient order of marine bryozoans.

Prolific polyembryony is reported in few major taxa, but its occurrence has generated theoretical debate on potential conflict between sexual and asexual reproduction. It is, therefore, important to genetically confirm a widely cited inference, based on microscopy, that polyembryony characterizes marine bryozoans of the order Cyclostomata. Microsatellite genotyping of brooded embryos and maternal colonies conclusively demonstrated polyembryony, while genetic variation among broods within colonies indicated outcrossing via water-borne sperm, in the rocky-shore species Crisia denticulata. The characteristically voluminous brood chamber of cyclostomes is judged to be an adaptation linked to larval cloning and hence an indicator of polyembryony. We speculate that although the almost universal occurrence of polyembryony among crown-group Cyclostomata is probably attributable to phylogenetic constraint, adaptive consequences are likely to be significant.

Rapid and reliable inference of mitochondrial phylogroups among Watersipora species, an invasive group of ship-fouling species (Bryozoa, Cheilostomata).

Tracking biological invasion is an essential part of conservation, and identifying invasive species quickly following an introduction can be imperative. Invasive organisms are often difficult to distinguish visually, which can delay appropriate response measures. We have designed a multiplex-PCR system to effectively distinguish colonies of divergent cytochrome oxidase subunit 1 (COI) sequence clades in the bryozoan genus Watersipora, a genus with invasive species which are aggressive foulers of ship hulls, to understand small-scale invasion patterns and the ecology of lineages of different geographic origins. The identification of previously defined COI lineage groups is conducted using PCR reactions containing five primers. Lineage-specific fragment lengths were produced with 100% reliability, suggesting the assay will offer a rapid and economical means of studying invasion dynamics and the role of adaptation in this rapidly invading species complex.

High-throughput Illumina sequencing and microsatellite design in Watersipora (Bryozoa), a complex of invasive species.

The bryozoan genus Watersipora includes rapidly invading species that are becoming common globally. We used paired-end Illumina sequencing to identify thousands of potentially amplifiable microsatellite loci, enabling researchers to track patterns of the invasive spread, and to facilitate ecological and evolutionary question setting. We describe variability of nine loci within recently introduced populations of two Watersipora species in California.