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Species interactions are integral drivers of community structure and can change from competitive to facilitative with increasing environmental stress. In subtidal marine ecosystems, however, interactions along physical stress gradients have seldom been tested. We observed seaweed canopy interactions across depth and latitudinal gradients to test whether light and temperature stress structured interaction patterns. We also quantified interspecific and intraspecific interactions among nine subtidal canopy seaweed species across three continents to examine the general nature of interactions in subtidal systems under low consumer pressure. We reveal that positive and neutral interactions are widespread throughout global seaweed communities and the nature of interactions can change from competitive to facilitative with increasing light stress in shallow marine systems. These findings provide support for the stress gradient hypothesis within subtidal seaweed communities and highlight the importance of canopy interactions for the maintenance of subtidal marine habitats experiencing environmental stress., (© 2015 John Wiley & Sons Ltd/CNRS.)

Gridded SST products developed particularly for offshore regions are increasingly being applied close to the coast for biogeographical applications. The purpose of this paper is to demonstrate the dangers of doing so through a comparison of reprocessed MODIS Terra and Pathfinder v5.2 SSTs, both at 4 km resolution, with instrumental in situ temperatures taken within 400 m from the coast. We report large biases of up to +6°C in places between satellite-derived and in situ climatological temperatures for 87 sites spanning the entire ca. 2 700 km of the South African coastline. Although biases are predominantly warm (i.e. the satellite SSTs being higher), smaller or even cold biases also appear in places, especially along the southern and western coasts of the country. We also demonstrate the presence of gradients in temperature biases along shore-normal transects - generally SSTs extracted close to the shore demonstrate a smaller bias with respect to the in situ temperatures. Contributing towards the magnitude of the biases are factors such as SST data source, proximity to the shore, the presence/absence of upwelling cells or coastal embayments. Despite the generally large biases, from a biogeographical perspective, species distribution retains a correlative relationship with underlying spatial patterns in SST, but in order to arrive at a causal understanding of the determinants of biogeographical patterns we suggest that in shallow, inshore marine habitats, temperature is best measured directly.

One of the impediments in the genetic improvement of cotton fiber is the paucity of information about genes associated with fiber development. Availability of chromosome arm substitution line CS-B22sh (chromosome 22 short arm substitution from 3-79 (Gossypium barbadense) into a TM-1 (Gossypium hirsutum) background) provides a novel opportunity to study fiber-associated genes because previous studies revealed this line was associated with some superior fiber quality traits compared to TM-1. We used an integrated approach of suppression subtractive hybridization (SSH), microarray, and real-time reverse transcription-polymerase chain reaction (RT-PCR) technologies to identify the potential genes associated with fiber development. Utilizing mRNAs from 15 days post-anthesis (dpa) fibers, we constructed a SSH cDNA library with chromosome substitution line CS-B22sh as the tester and TM-1 as the driver. The SSH cDNA library was screened using microarrays. Microarray analysis showed that 36 genes were differentially expressed in CS-B22sh 15-dpa fiber compared to TM-1 as confirmed by real time RT-PCR. These genes include two beta-tubulins, an actin, a putative kinesin light chain, a cellulose synthase, glycosyl hydrolase family 3 protein, pyruvate decarboxylase, glycoside hydrolase family 5, GDP-mannose pyrophosphorylase, dynamin-like protein, annexin, and a number of genes involved in signal transduction, and protein, nucleic acid, and lipid metabolisms. To our knowledge, this is the first report on identification of differentially expressed fiber-associated genes in a cotton chromosomal substitution line.