The role of hydro-environmental factors in Mayfly (Ephemeroptera, Insecta) community structure: Identifying threshold responses.

Freshwater organisms are threatened by changes in stream flow and water temperature regimes due to global climate change and anthropogenic activities. Threats include the disappearance of narrow-tolerance species and loss of favorable thermal conditions for cold-adapted organisms. Mayflies are an abundant and diverse indicator of river health that performs important functional roles. The relative importance of key hydro-environmental factors such as water temperature and flow volumes in structuring these communities has rarely been explored in the tropical regions of Africa. Here, we investigate the response of mayfly species diversity to these factors in the Luvuvhu catchment, a strategic water source area in the arid northeastern region of South Africa. Mayfly larvae were sampled monthly in stones-in-current biotopes across 23 sites over a one-year period. The relationship between these environmental drivers and mayfly diversity was modeled using linear mixed effects models (LMMs) and a model-based multivariate approach. Threshold Indicator Taxa Analysis (TITAN) was used to model the response of mayfly species to important gradients and identify thresholds of change. Site-specific characteristic were the most important predictor of mayfly diversity, and there was considerable variation over time, with mayfly diversity peaking during winter. Along this, gradient temperature was the best predictor of assemblage structure, with five out of six reliable indicator species being cold-adapted, and a community threshold response at 19°C. Results support laboratory-based thresholds of temperature for mayfly species survival and development, extending empirical evidence to include field-based observations. Increased global (climate change) and local (riparian vegetation removal, impoundments) changes are predicted to have negative impacts on mayfly diversity and ultimately on ecosystem function.

Trophic overlap between fish and riparian spiders: potential impacts of an invasive fish on terrestrial consumers.

Studies on resource sharing and partitioning generally consider species that occur in the same habitat. However, subsidies between linked habitats, such as streams and riparian zones, create potential for competition between populations which never directly interact. Evidence suggests that the abundance of riparian consumers declines after fish invasion and a subsequent increase in resource sharing of emerging insects. However, diet overlap has not been investigated. Here, we examine the trophic niche of native fish, invasive fish, and native spiders in South Africa using stable isotope analysis. We compared spider abundance and diet at upstream fishless and downstream fish sites and quantified niche overlap with invasive and native fish. Spider abundance was consistently higher at upstream fishless sites compared with paired downstream fish sites, suggesting that the fish reduced aquatic resource availability to riparian consumers. Spiders incorporated more aquatic than terrestrial insects in their diet, with aquatic insects accounting for 45-90% of spider mass. In three of four invaded trout rivers, we found that the average proportion of aquatic resources in web-building spider diet was higher at fishless sites compared to fish sites. The probability of web-building and ground spiders overlapping into the trophic niche of invasive brown and rainbow trout was as high as 26 and 51%, respectively. In contrast, the probability of spiders overlapping into the trophic niche of native fish was always less than 5%. Our results suggest that spiders share resources with invasive fish. In contrast, spiders had a low probability of trophic overlap with native fish indicating that the traits of invaders may be important in determining their influence on ecosystem subsidies. We have added to the growing body of evidence that invaders can have cross-ecosystem impacts and demonstrated that this can be due to niche overlap.

SAR development of a selective 5-HT1D antagonist/serotonin reuptake inhibitor lead using rapid parallel synthesis.

Incorporation of an SRI (serotonin reuptake inhibitor) pharmacophore into a selective 5-HT(1D) agonist has led to the discovery of a molecule having both 5-HT(1D) antagonist and SRI activity. RPS methodology was used to develop the SAR and identify potential approaches to reduce unwanted adrenergic alpha 1 and dopamine D(2) cross-reactivities.

Bicyclo[2.2.1]heptanes as novel triple re-uptake inhibitors for the treatment of depression.

A series of substituted naphthyl containing chiral [2.2.1] bicycloheptanes were prepared utilizing asymmetric Diels-Alder chemistry. This paper describes structure-activity relationships in this series. The N-methyl 2-naphthyl analogue (16d) and its des-methyl analogue (17d) are active triple re-uptake inhibitors both in vivo and in vitro.