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It is widely accepted that insular terrestrial biodiversity progresses with island age because colonization and diversification proceed over time. Here, we assessed whether this principle extends to oceanic island streams. We examined rangewide mtDNA sequence variation in four stream-dwelling species across the Hawaiian archipelago to characterize the relationship between colonization and demographic expansion, and to determine whether either factor reflects island age. We found that colonization and demographic expansion are not related and that neither corresponds to island age. The snail Neritina granosa exhibited the oldest colonization time (~2.713 mya) and time since demographic expansion (~282 kya), likely reflecting a preference for lotic habitats most prevalent on young islands. Conversely, gobioid fishes (Awaous stamineus, Eleotris sandwicensis and Sicyopterus stimpsoni) colonized the archipelago only ~0.411-0.935 mya, suggesting ecological opportunities for colonization in this group were temporally constrained. These findings indicate that stream communities form across colonization windows, underscoring the importance of ecological opportunities in shaping island freshwater diversity., (© 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.)

Protecting the world's freshwater resources requires diagnosing threats over a broad range of scales, from global to local. Here we present the first worldwide synthesis to jointly consider human and biodiversity perspectives on water security using a spatial framework that quantifies multiple stressors and accounts for downstream impacts. We find that nearly 80% of the world's population is exposed to high levels of threat to water security. Massive investment in water technology enables rich nations to offset high stressor levels without remedying their underlying causes, whereas less wealthy nations remain vulnerable. A similar lack of precautionary investment jeopardizes biodiversity, with habitats associated with 65% of continental discharge classified as moderately to highly threatened. The cumulative threat framework offers a tool for prioritizing policy and management responses to this crisis, and underscores the necessity of limiting threats at their source instead of through costly remediation of symptoms in order to assure global water security for both humans and freshwater biodiversity.

Alteration of rivers for human use has resulted in substantial biodiversity declines, particularly for species restricted to the largest rivers. Conservation and restoration efforts on large rivers often focus on the mainstem, but societal reliance on benefits derived from these alterations generally prevents complete restoration of the river. We propose that certain tributaries, by virtue of their lower degree of alteration, offer underappreciated opportunities for conserving large-river biota. Using the distribution patterns of large-river specialist fishes from the Mississippi River Basin, we identify a threshold discharge (166 cubic meters per second) beyond which tributaries support all or most of these species. We merge our macroecological analysis of assemblage structure with data on dam locations to identify tributaries where restoration efforts offer the highest potential conservation gains for 60 of the 68 large-river specialist fish species that are of state, federal, or international conservation concern. Given the highly altered state of many mainstem rivers, this analytical approach could be used to select tributaries that will aid in the conservation of large-river species worldwide. [ABSTRACT FROM AUTHOR]

The article discusses the relationship between hydropower and biodiversity regarding dams built on the Mekong River, Congo River and the Amazon River. An overview of the impact that dams have in putting fresh water fish and fisheries at risk, including their impact on decreasing the biodiversity of fish, is provided.