Flow intermittency alters longitudinal patterns of invertebrate diversity and assemblage composition in an arid‐land stream network

Abstract

Summary 1. Temporary streams comprise a large proportion of the total length of most stream networks, and the great majority of arid‐land stream networks, so it is important to understand their contribution to biotic diversity at both local and landscape scales. 2. In late winter 2010, we sampled invertebrate assemblages in 12 reaches of a large arid‐land stream network (including perennial and intermittent headwaters, intermittent middle reaches and perennial rivers) in south‐east Arizona, U.S.A. Intermittent reaches had then been flowing for c. 60 days, following a dry period of more than 450 days. We sampled a subset of the perennial study reaches three more times between 2009 and 2011. Since intermittent reaches were dry during these additional sampling periods, we used assemblage data from two other intermittent streams in the study network (sampled in 2004–05 and 2010) to explore interannual variability in intermittent stream assemblage composition. 3. Invertebrate richness was lowest in intermittent reaches, despite their often being connected to species‐rich perennial reaches. The assemblages of these intermittent reaches were not simply a subset of the species in perennial streams, but rather were dominated by a suite of stoneflies, blackflies and midges with adaptations to intermittency (e.g. egg and/or larval diapause). On average, 86% of individuals in these samples were specialists or exclusive to intermittent streams. Predators were 7–14 times more abundant in perennial than in intermittent reaches. 4. Despite being separated by long distances (12–25 km) and having very different physical characteristics, the assemblages of perennial headwaters and rivers were more similar to one another than to intervening intermittent reaches, emphasising the prime importance of local hydrology in this system. 5. The duration and recurrence intervals of dry periods, and the relative importance of dispersal from perennial refuges, probably influence the magnitude of biological differences between neighbouring perennial and temporary streams. Although perennial headwaters supported the highest diversity of invertebrates, intermittent reaches supported a number of unique or locally rare species and as such contribute to regional species diversity and should be included in conservation planning.

Experimentally disentangling the influence of dispersal and habitat filtering on benthic invertebrate community structure

“…Network structure and dispersal can interact with larger scale habitat variables like drying and elevation Bogan, Boersma, & Lytle, 2013;Canedo-Arguelles et al, 2015;Leigh & Datry, 2017) and that these interactions can be highly context dependent (Heino, Gr€ onroos, Soininen, et al, 2012;Tonkin, Heino, Sundermann, Haase, & J€ ahnig, 2016;Schmera et al 2017). Even on smaller spatial scales like the stream reach scale, natural complexity and habitat variability can directly affect the process of macroinvertebrate dispersal (Brooks, Wolfenden, Downes, & Lancaster, 2017).…”

The effect of spatial configuration of habitat capacity on β diversity

“…Even with only dispersal limitation in the model, patterns of species turnover measured by these indices were non-monotonic. Non-monotonicity, such as ''peaks,'' ''valleys,'' and ''plateaus'' (e.g., Condit et al 2002, Anderson et al 2013, Bogan et al 2013, in species spatial turnover has been used as evidence for local environmental filtering processes shaping community composition and distribution. We did not observe nonmonotonicity in the species spatial turnover measured by Chao index (Fig.…”

“…In the ''random-shuffle'' configuration, we randomized the spatial distribution of habitat capacities along the gradient. In the ''V-shaped'' configuration, habitat capacity was set high at both ends and low in the middle of the gradient; this is akin to a stream system in which the headwater receives much rainfall and the downstream end connects to a large river, while the middle reaches are intermittent streams (e.g., Bogan et al 2013). In the ''hump-shaped'' configuration, habitat capacity was large in the middle and small at the two extremes of the gradient-akin to an edge effect such as the boundaries of a forest experiencing more external pressure than its interior.…”

“…Species turnover refers to the rate of change in community structure along a given gradient, such as the distance decay relationship (DDR) describing decreasing taxonomic similarity with geographic distance (e.g., Qian andRicklefs 2007, Brown andSwan 2010). Ecologists expect monotonic decay of species spatial turnover to occur when a system is predominantly controlled by dispersal limitation, whereas deviations from DDR (i.e., ''peaks'' and ''valleys'' in the species spatial turnover) indicate the importance of local environmental filtering on species occurrence (e.g., Condit et al 2002, Anderson et al 2013, Bogan et al 2013. b diversity as variation is captured by Whittaker's original measures (b w ¼ c=ā) or the mean dissimilarity index (such as Bray-Curtis and Sorensen dissimilarity index) among communities (d ¼ 1 m R i; j , i d ij ; m ¼ NðN À 1Þ=2 is total sample units; Anderson et al 2011).…”

Multi-scale functional and taxonomic β-diversity of the macroinvertebrate communities in a Mediterranean coastal lagoon

“…It is worth noting that taxonomic replacements do not always lead to variations in functional diversity and, consequently, in ecological functioning. The lack of significant variability in functional composition discloses a pattern of functional redundancy, profusely described for macroinvertebrate communities (Sigala et al, 2012;Bogan et al, 2013). Functional redundancy may be a result of environmental filtering, which restricts trait diversity (Heino, 2005) and is an indicator of relative resilience of the traits and may help in maintaining the functions of an ecosystem after disturbance (Schmera et al, 2012).…”