Dams on the Senegal river supported the expansion of agriculture upstream -- and created an epidemic of schistosomiasis.
By examining the patterns of genetic and phenotypic introgression in the wake of upstream expansion, we also assessed whether the decline of native C. venusta following the introduction of C. lutrensis is best characterized as a process of displacement or loss through introgressive hybridization.
The Neversink, as it turns out, hosts the mother lode of dwarf wedge mussels; the dam, however, prevented upstream expansion of an otherwise fragile population.
The authors observed multiple distinct flushing events after the activation of the subglacial hydrological system, suggesting that various types of meltwater pulse — drainage of lakes on the ice surface through moulins, rapid surface melting during warm spells, and upstream expansion of active subglacial water systems — can liberate subglacial methane.
A massive expansion of a GGGGCC repeat upstream of the C9orf72 coding region is the most common known cause of amyotrophic lateral sclerosis and frontotemporal dementia.
The expansion of SNCA-Rep1, an upstream, polymorphic microsatellite of the SNCA gene, is associated with elevated risk for sporadic PD.
About 10%% of all patients with amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD) or mixed presentation of both diseases (ALS/FTD) are caused by a massive expansion of a GGGGCC repeat upstream of the C9orf72-coding region [ 11, 18, 43].
Similarly, it is likely that the upstream expansion of the C. lutrensis × C. venusta hybrid swarm has been facilitated by yearly increases in the frequencies of successfully reproducing later-generation hybrids (Endler 1977; Huxel 1999; Hall et al. 2006).
Finally, abnormal intestinal motility prolonging colon transit [ 23, 24] deprives the colon from carbohydrates inducing upstream expansion of proteolytic species increasing generation of bacterial toxins and increasing time for their absorption [ 23].
Most of the hybrids that we collected were later-generation and backcrossed individuals, suggesting that continued upstream expansion of the hybrid swarm (Walters et al. 2008) is unlikely to be restricted by reduced hybrid viability and fertility (Blum et al. 2010).
