The Contribution of Headwater Streams to Biodiversity in River Networks¹

Abstract

The diversity of life in headwater streams (intermittent, first and second order) contributes to the biodiversity of a river system and its riparian network. Small streams differ widely in physical, chemical, and biotic attributes, thus providing habitats for a range of unique species. Headwater species include permanent residents as well as migrants that travel to headwaters at particular seasons or life stages. Movement by migrants links headwaters with downstream and terrestrial ecosystems, as do exports such as emerging and drifting insects. We review the diversity of taxa dependent on headwaters. Exemplifying this diversity are three unmapped headwaters that support over 290 taxa. Even intermittent streams may support rich and distinctive biological communities, in part because of the predictability of dry periods. The influence of headwaters on downstream systems emerges from their attributes that meet unique habitat requirements of residents and migrants by: offering a refuge from temperature and flow extremes, competitors, predators, and introduced species; serving as a source of colonists; providing spawning sites and rearing areas; being a rich source of food; and creating migration corridors throughout the landscape. Degradation and loss of headwaters and their connectivity to ecosystems downstream threaten the biological integrity of entire river networks.

Ichthyofauna of the upper Juruena river on Chapada dos Parecis, Mato Grosso, Brazil

“…Additionally, as stated by Meyer et al (2007) fish fauna from headwater streams can make a significant contribution to regional fish diversity. The presence of a high number of endemic fish and at least five new species in a small portion of the upper rio Juruena indicates it as a hotspot area for fish diversity, and as such as having potential priority for conservation measures (Carvalho & Bertaco 2006, Britski & Lima 2008, Ohara & Lima 2015.…”

“…The headwater streams seem to harbor a unique species assemblage due to observed differences in abiotic factors such as temperature, light, hydrologic regime, water chemistry, substrate type, food resources and species pool influenced by small-scale differences in local conditions (Meyer et al 2007).…”

Environmental and Anthropogenic Factors Influencing Salamanders in Riparian Forests: A Review

“…For example, the physical and chemical conditions of headwater streams are closely linked to terrestrial inputs of nutrients, toxins, and sediment, which makes them sensitive to anthropogenic disturbance [115,116]. Consequently, salamanders and other headwater specialist taxa in the United States may be particularly vulnerable to human perturbation [27,117]. In this section, we identify five anthropogenic activities that have been shown to negatively impact salamander populations in riparian forests and examine the mechanisms behind their effects.…”

“…), and mink (Neovison vison) are often associated with riparian areas [25]. Some species of invertebrates, such as the mayfly Paraleptophlebia gergalis, the stonefly Soyedina interrupta, and certain craneflies and crayfish, may even be unique or uniquely adapted to headwater riparian areas [26,27], and amphibians such as salamanders can be particularly diverse and abundant within riparian systems [28][29][30].…”

Bacterial community dynamics in the hyporheic zone of an intermittent stream

“…Watersheds comprise hundreds of small, headwater streams within their boundaries (Naiman et al, 2005), and biodiversity in these streams remains largely underestimated (Meyer et al, 2007). North American headwater streams are first-and secondorder streams along the river continuum (Vannote et al, 1980), small in scale (for example, o3 m), largely fishless and characterized by predictable low-flow conditions (Richardson and Danehy, 2007).…”