Gene flow in malaria vector Anopheles stephensi (Diptera: Culicidae) across the Aravalli Hills in North-west India

The population structure of An. stephensi in North-west India was studied to assess the impact of the Aravalli Hills, as a barrier to gene flow using microsatellite markers. Large and significant genetic differentiation was found along the sides of, as well as across, the Aravalli Hills as the mean F_ST and R_ST on west vs. east of the Aravalli Hills were 0.213, 0.112 and 0.179, 0.056, respectively. Similarly, across the hills, mean values of F_ST and R_ST were 0.100 and 0.094, respectively. Genetic diversity on both sides did not vary significantly. The F_ST values were more sensitive than R_ST values, indicating that genetic drift might have caused genetic differentiation between populations. A positive correlation (r = 0.0149 and 0.157, respective to F_ST and R_ST) was found between genetic differentiations and geographic distances irrespective of the hills. Low level of gene flow was found along both sides (Nm = 0.92 and 0.14; west vs. east of Aravalli Hills, respectively) as compared to across the Aravalli Hills (Nm = 2.25). It was found that the Aravalli Hills are not working as an effective barrier to gene flow for An. Stephensi, maybe because of the low average height and discontinuous hills, however, the distance is playing a major role for differentiation between populations due to active mode of dispersal of An. stephensi mosquitoes which have a short flight range. All this information should help draw the strategies for genetic control of mosquitoes using transgenic mosquitoes.     

Major disturbance events in terrestrial ecosystems detected using global satellite data sets

Ecosystem scientists have yet to develop a proven methodology to monitor and understand major disturbance events and their historical regimes at a global scale. This study was conducted to evaluate patterns in an 18‐year record of global satellite observations of vegetation phenology from the Advanced Very High Resolution Radiometer (AVHRR) as a means to characterize major ecosystem disturbance events and regimes. The fraction absorbed of photosynthetically active radiation (FPAR) by vegetation canopies worldwide has been computed at a monthly time interval from 1982 to 1999 and gridded at a spatial resolution of 0.5° latitude/longitude. Potential disturbance events of large extent ( > 0.5 Mha) were identified in the FPAR time series by locating anomalously low values (FPAR‐LO) that lasted longer than 12 consecutive months at any 0.5° pixel. We find that nearly 400 Mha of the global land surface could be identified with at least one FPAR‐LO event over the 18‐year time series. The majority of these potential disturbance events occurred in tropical savanna and shrublands or in boreal forest ecosystem classes. Verification of potential disturbance events from our FPAR‐LO analysis was carried out using documented records of the timing of large‐scale wildfires at locations throughout the world. Disturbance regimes were further characterized by association analysis with historical climate anomalies. Assuming accuracy of the FPAR satellite record to characterize major ecosystem disturbance events, we estimate that nearly 9 Pg of carbon could have been lost from the terrestrial biosphere to the atmosphere as a result of large‐scale ecosystem disturbance over this 18‐year time series.