Michael Bogan

• Ph.D.
• Associate professor at University of Arizona

Flow variability plays an important role in structuring lotic communities, yet comparatively little is known about processes governing assemblage dynamics in stream ecosystems with stable environmental conditions , such as spring-fed rivers. Volcanic spring-fed rivers (hereafter spring-fed rivers) occur in geologically active landscapes of the west...

Headwater and intermittent streams have traditionally been considered less biologically diverse than downstream perennial reaches. However, recent studies have highlighted the significant role that headwaters play in supporting regional aquatic biodiversity. Additionally, intermittent streams in the Pacific Northwest may be more diverse than simila...

In arid regions, spring-fed habitats are frequently the only year-round source of surface water and are essential habitats for aquatic organisms and primary water sources for terrestrial animals and human settlements. While these habitats have been relatively well-studied in some regions, those of the southern Sonoran Desert have received little at...

During late summer and fall 2014, we documented western pond turtle (Actinemys marmorata) mortality, as indicated by the presence of turtle shells, along a 3.7-km reach of Coyote Creek in the Diablo Range of central California. In total, we observed 39 western pond turtle shells scattered irregularly along our study reach. Shells were found in dry...

Aquatic ecosystems overlying regions of limestone bedrock can feature active deposition of calcium carbonate in the form of travertine or tufa. Although most travertine deposits form a cement-like layer on stream substrates, mineral deposits can also form on benthic invertebrates. However, little is known about which taxa may be prone to calcium ca...

More than half of the world’s rivers dry up periodically, but our understanding of the biological communities in dry riverbeds remains limited. Specifically, the roles of dispersal, environmental filtering and biotic interactions in driving biodiversity in dry rivers are poorly understood. Here, we conduct a large-scale coordinated survey of patter...

Freshwater species face numerous threats across the globe, including urbanization. Within cities in regions with drier climates, dewatering and channelization of rivers commonly occur and reduce or eliminate freshwater biodiversity. The discharge of effluent (treated wastewater) has been used to restore flow in some of these rivers, but our knowled...

Stream drying is happening globally, with important ecological and social consequences. Most examples of stream drying come from systems influenced by dam operations or those with highly exploited aquifers. Stream drying is also thought to be driven by anthropogenic climate change; however, examples are surprisingly limited. We explored flow trends...

Studies of stream macroinvertebrates traditionally use sampling methods that target benthic habitats. These methods could underestimate biodiversity if important assemblage components exist outside of the benthic zone. To test the efficacy of different sampling methods, we collected paired reach‐wide benthic and edge samples from up to 10 study rea...

Intermittent streams are globally ubiquitous and represent a large percentage of stream networks. As climate change in many arid regions increases the frequency and intensity of drying disturbances, it is important to understand how aquatic biota will respond to such disturbances and how it would impact aquatic biodiversity. To address these topics...

The lack of data from non-perennial rivers, which regularly cease to flow and dry up, poses a significant challenge in understanding river biodiversity. These dynamic ecosystems, accounting for over half of the global river network, remain understudied. To address this gap, we conducted a coordinated experiment and a metabarcoding approach on envir...

Intermittent streams that cease to flow during dry periods represent more than half of the global river network, and are particularly common in arid and semi‐arid regions. They are characterised by high spatial and temporal variability in aquatic habitat, forming a shifting habitat mosaic that supports diverse assemblages of native and endemic spec...

Effluent-fed streams, which receive inputs from wastewater treatment plants, are becoming increasingly common across the globe as urbanization intensifies. In semi-arid and arid regions, where many natural streams have dried up due to over extraction of water, many streams rely completely on treated effluent to sustain baseflow during dry seasons....

Intermittent streams are globally distributed, comprise over half the length of the global river network, and are expected to become more prevalent. However, most studies of intermittent streams are conducted at extremes of scale, are limited in taxonomic and temporal scope, and focus exclusively on drying patterns. Here, we assessed how both flow...

Springs are essential sources of water for humans and wildlife in the Sonoran Desert and, despite their isolation, they often support diverse aquatic communities. However, flows in these systems are declining due to groundwater pumping and increasing temperatures and aridity. In the western Sonoran Desert, two spring-fed systems represent the vast...

The current erosion of biodiversity is a major concern that threatens the ecological integrity of ecosystems and the ecosystem services they provide. Due to global change, an increasing proportion of river networks are drying and changes from perennial to non‐perennial flow regimes represent dramatic ecological shifts with potentially irreversible...

Effluent discharge from wastewater treatment plants can be a substantial source of microplastics in receiving water bodies including rivers. Despite growing concern about microplastic pollution in freshwater habitats, the literature has not yet addressed effluent-dependent rivers, which derive 100% of their baseflow from effluent. The objective of...

Treated wastewater, also known as effluent, is discharged into streambeds where it can augment or create aquatic habitat in arid regions. However, discharge fluctuations can result in daily stream drying and rewetting. In this study, we documented flow intermittence and resulting fish stranding and mortality over a 12-week period on an effluent-dep...

Chlorophyll-a measurements are an important factor in the water quality monitoring of surface waters, especially for determining the trophic status and ecosystem management. However, a collection of field samples for extractive analysis in a laboratory may not fully represent the field conditions. Handheld fluorometers that can measure chlorophyll-...

Climate change is altering the water cycle globally, increasing the frequency and magnitude of floods and droughts. An outstanding question is whether biodiversity responses to hydrological disturbance depend on background climatic context – and if so, which contexts increase vulnerability to disturbance. Answering this question requires comparison...

Background Aquatic ecosystems are greatly altered by urban development, including the complete loss of natural habitat due to water diversions or channel burial. However, novel freshwater habitats also are created in cities, such as effluent-dependent streams that rely on treated wastewater for flow. It is unclear how diverse these novel ecosystems...

Increasing anthropogenic demands for freshwater have altered many aquatic systems, including the drying of formerly perennial streams. The discharge of treated effluent has returned perennial flow in some of these streams, especially in arid and semi-arid regions, but the ability of treated effluent to support diverse aquatic communities is poorly...

Conceptual models underpin river ecosystem research. However, current models focus on continuously flowing rivers and few explicitly address characteristics such as flow cessation and drying. The applicability of existing conceptual models to nonperennial rivers that cease to flow (intermittent rivers and ephemeral streams, IRES) has not been evalu...

We investigated the hypothesis that ostracode populations are sensitive to variations in sediment discharge related to watershed differences at Lake Tanganyika. Many ostracode species are documented to be sensitive to high turbidity which increases during runoff from strong rainfall events and changes in ostracode populations can impact organisms h...

Despite an historical connection between the arts and sciences, in the past century, the two disciplines have been greatly siloed. However, there is a renewed interest in collaboration across the arts and sciences to support conservation practice by understanding and communicating complex environmental, social, and cultural challenges in novel ways...

Non-perennial rivers, watercourses that cease to flow at some point in time and space, are widespread globally but often lack effective protections. Although it is thought that these ecosystems are undervalued by society, empirical studies exploring people’s perceptions of non-perennial rivers are uncommon. We carried out an image-based survey at t...

Rivers that cease to flow are globally prevalent. Although many epithets have been used for these rivers, a consensus on terminology has not yet been reached. Doing so would facilitate a marked increase in interdisciplinary interest as well as critical need for clear regulations. Here we reviewed literature from Web of Science database searches of...

• Worldwide, the addition of treated wastewater (i.e. effluent) to streams is becoming more common as urban populations grow and developing countries increase their use of wastewater treatment plants. Release of treated effluent can impair water quality and ecological communities, but also could help restore flow and maintain aquatic habitat in wat...

Streamflow observations can be used to understand, predict, and contextualize hydrologic, ecological, and biogeochemical processes and conditions in streams. Stream gages are point measurements along rivers where streamflow is measured, and are often used to infer upstream watershed‐scale processes. When stream gages read zero, this may indicate th...

Nonperennial rivers are a major—and growing—part of the global river network. New research and science-based policies are needed to ensure the sustainability of these long-overlooked waterways.

Intermittent rivers and ephemeral streams (IRES) may represent over half the global stream network, but their contribution to respiration and carbon dioxide (CO2) emissions is largely undetermined. In particular, little is known about the variability and drivers of respiration in IRES sediments upon rewetting, which could result in large pulses of...

Rock pools are important desert ecosystems that provide rare sources of surface water in arid regions. Hydroperiod is one of the primary limiting factors on aquatic macroinvertebrates living in rock pools. Resident macroinvertebrates must complete their life cycles before drying, and may employ active or passive dispersal strategies to survive dryi...

.—During the summers of 2015 and 2018, we observed predation on Foothill Yellow-legged Frogs (Rana boylii) by a giant water bug (Abedus indentatus), a California Red-legged Frog (Rana draytonii), and a Diablo Range Gartersnake (Thamnophis atratus zaxanthus) adjacent to 3 separate isolated pools along intermittent reaches of Coyote Creek, Santa Clar...

Climate change and human pressures are changing the global distribution and the extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico‐chemical changes (preconditioning), and...

Climate change and human pressures are changing the global distribution and the extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico‐chemical changes (preconditioning), and...

Perennial rivers and streams make a disproportionate contribution to global carbon (C) cycling. However, the contribution of intermittent rivers and ephemeral streams (IRES),which sometimes cease to flow and can dry completely, is largely ignored although theymay represent over half the global river network. Substantial amounts of terrestrialplant...

In the version of this Article originally published, the affiliation for M. I. Arce was incorrect; it should have been: ⁵Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany. This has now been corrected in the online versions of the Article.

Intermittent rivers and ephemeral streams (IRES) support diverse and sometimes distinctive aquatic invertebrate communities. Although flow intermittence has been linked to reduced taxa richness, the highly variable environmental conditions that characterize IRES can enhance both taxonomic and functional diversity, with different invertebrates chara...

Intermittent rivers and ephemeral streams (IRES) are temporally and spatially dynamic ecosystems, experiencing alternating wet and dry phases and supporting both aquatic and terrestrial habitats. For aquatic species to persist in these variable habitats, they must be resistant or resilient to disturbances such as flow cessation and drying. Resistan...

Species inhabiting intermittent streams must have life-history traits that confer resistance or resilience to flow cessation or drying. However, we lack basic life-history information for most aquatic invertebrate species, especially those from intermittent streams. I documented the life cycle and distribution of an unusual winter stonefly species,...

Species inhabiting intermittent streams must survive flow cessation and drying in situ (resistance) or recolonize temporary habitats when flow returns (resilience). Some studies have found that species are resistant to seasonal drying and can persist in small remnant pools after flow ceases, while others observed rapid declines in species richness...

Disturbance is a central factor shaping composition, structure, and dynamics of local communities. Drying is a disturbance that occurs in aquatic ecosystems globally and can strongly influence their communities. Although the effects of drying may depend on ecosystem connectivity and the dispersal abilities of resident species, there have been no co...

Sonoran Desert toads (Incilius alvarius) are known to consume invertebrates, small lizards, other toads, and mice. Here we report an attempt by a Sonoran Desert toad to consume a western desert tarantula (Aphonopelma chalcodes) at Sabino Canyon, Arizona. Despite nearly being completely swallowed, the tarantula was able to escape after a struggle la...

Fisheries have been described as large-scale evolutionary experiments; yet such “experiments” tend to be poorly replicated and therefore lack the predictive power essential for designing appropriate management strategies to minimize the effects of fisheries-induced selection. Large-scale removal of non-native trout from 35 montane lakes in Californ...

Temporal environmental fluctuations, such as seasonality, exert strong controls on biodiversity. While the effects of seasonality are well known, the predictability of fluctuations across years may influence seasonality in ways that are less well understood. The ability of a habitat to support unique, non-nested assemblages of species at different...

Intermittent rivers and ephemeral streams (IRES) are temporally and spatially dynamic, experiencing alternating wet and dry phases and supporting both aquatic and terrestrial habitats – Persistence in these highly variable habitats requires aquatic taxa to be resistant or resilient to disturbances such as drying – Resistance mechanisms include tole...

Intermittent rivers and ephemeral streams (IRES) are temporally dynamic ecosystems that can support a diverse and distinctive aquatic invertebrate fauna – Resistance and resilience mechanisms allow species and communities to persist in IRES during dry phases and to recolonize quickly once flow returns – Human influences including climate change and...

Water scarcity is becoming one of the greatest challenges that human societies will face during this century. Monitoring water availability is expensive and technically challenging. In this regard, biological communities (e.g. aquatic insects) offer a cost-effective alternative, since they integrate temporal and spatial hydrological variability. He...

A place of edges, a place of ecotones. Sky, sea, and desert give way to outposts of the tropics. Brown and parched during the long dry seasons and green when it rains. The sea is edged in halophytes and stunted mangroves. Spinescent desert spans most of the land, while riparian canyons host tropical trees and palm oases. Soil moisture and maritime...

This code modifies a function originally provided in the FD package (Laliberté, E., Legendre, P., and B. Shipley. 2014. FD: measuring functional diversity from multiple traits, and other tools for functional ecology. R package version 1.0-12.). It has been useful for some folks trying to implement our framework from Boersma et al 2016 Ecology so...

Flow variability plays an important role in structuring lotic communities, yet we know comparatively little about processes governing species assemblage dynamics in stream ecosystems exhibiting stable environmental conditions. We sampled invertebrate assemblages and quantified primary productivity and habitat characteristics over four seasons from...

Functional trait analysis is an appealing approach to study differences among biological communities because traits determine species' responses to the environment and their impacts on ecosystem functioning. Despite a rapidly expanding quantitative literature, it remains challenging to conceptualize concurrent changes in multiple trait dimensions (...

A number of insect orders are infrequently collected in freshwater habitats and have relatively low richness of aquatic species; however, these taxa may be locally abundant and can play important roles in freshwater food webs. The two families of Megaloptera, Corydalidae (fishflies and dobsonflies) and Sialidae (alderflies), have fully aquatic, pre...

Functional trait analysis is an appealing approach to study differences among biological communities because traits determine species' responses to the environment and their impacts on ecosystem functioning. Despite a rapidly expanding quantitative literature, it remains challenging to conceptualize concurrent changes in multiple trait dimensions (...

Nearly 70 years after North American conservationist Aldo Leopold reflected on his own struggle with the relationship between humans and wildlife in ‘A Sand County Almanac’, conservation scientists are still wrestling with the extent to which their research aims to protect and restore ecosystems for ‘nature's sake’ (i.e. intrinsic value), or for ‘h...

Aim Meta‐community structure is a function of both local (site‐specific) and regional (landscape‐level) ecological factors, and the relative importance of each may be mediated by the dispersal ability of organisms. Here, we used aquatic invertebrate communities to investigate the relationship between local and regional factors in explaining distanc...

Hydrology is a fundamental factor influencing ecosystem dynamics, life-history strategies, and diversity patterns in running-water habitats. However, it remains unclear how hydrology may structure the taxonomic and functional composition of communities, especially in systems with high spatiotemporal variability in flow. We examined invertebrate div...

Climate change is expected to intensify drought in many regions, but ecological impacts on stream communities are poorly understood. Many arid‐land streams are characterised by predictable seasonal cycles of wetting and drying, to which species are adapted, but unpredictable supraseasonal droughts may constitute extreme events that challenge reside...

Species occupying the same geographic range can exhibit remarkably different population structures across the landscape, ranging from highly diversified to panmictic. Given limitations on collecting population-level data for large numbers of species, ecologists seek to identify proximate organismal traits - such as dispersal ability, habitat prefer...

In dryland regions, increased demand for water has led to the reduction of natural aquatic habitats and threatens persisting aquatic habitats. In the Madrean Sky Islands (MSI), water demands have also resulted in the creation of novel aquatic habitats, including stock ponds. Stock ponds are important surrogate habitat for native species, yet little...

Background/Question/Methods Functional diversity provides an appealing approach to study differences between fragmented biological communities because traits determine species’ responses to the environment, and multiple traits covary within individuals. Consequently, interest in multivariate functional diversity methods has surged over the past d...

Background/Question/Methods Size-selective fishing is expected to trigger evolutionary changes but the potential for fishery-induced selection to significantly modify population characteristics is controversial and not yet well understood. More research is needed to understand how and when size-selective fishing alters traits and dynamics in harve...

Background/Question/Methods Streams that dry for extended periods of time tend to support less diverse aquatic communities than perennial streams. However, research quantifying patterns of community assembly in streams following flow resumption is uncommon. Studies from temperate streams suggest that community recovery following drying disturbanc...

Top predator losses aff ect a wide array of ecological processes, and there is growing evidence that top predators are disproportionately vulnerable to environmental changes. Despite increasing recognition of the fundamental role that top predators play in structuring communities and ecosystems, it remains challenging to predict the consequences of...

Early colonising ecosystem engineers modify habitats and alter the abundance of basal resources following disturbances. These changes can have profound effects on ecosystem recovery via facilitative or inhibitory effects on subsequent colonists. We quantified how black fly larvae, which can be pioneer species during secondary succession in streams,...

The Nature Conservancy and a team of 14 academic partners (the project team) received funding from the Bureau of Reclamation’s WaterSMART program and the Desert Landscape Conservation Cooperative in 2012 to conduct this Gila River Flow Needs Assessment. The assessment describes the existing condition of the Gila River in the Cliff-Gila Valley and e...

Seasonal droughts are predictable components of arid‐land stream hydrology, and many arid‐land aquatic taxa have adapted to their extreme environment. However, climate change is altering this predictable hydrology, producing longer and more severe droughts and creating novel disturbance regimes for resident organisms. The hydrologic transitions fro...

While distributions of aquatic insects are fairly well known in the southwestern United States, relatively few surveys have been conducted in northwestern Mexico. We report new collections of species of aquatic Heteroptera in the region, which extend the known range of several species by hundreds of kilometers, including the first record of Graptoc...

Background/Question/Methods Ecological theory predicts that species composition in fragmented communities may become more similar (convergent) or more distinct (divergent) through time. Fragmented communities may converge in composition due strong reductions in the overall number of species, loss of keystone species that facilitate persistence of...

Background/Question/Methods The predicted increase in drought conditions and intermittency of stream flow in the deserts of the American southwest is a major concern for aquatic organisms and adjacent terrestrial habitats. Alterations from natural stream conditions can cause shifts in population and community structure, species extirpations, ecol...

Temporary rivers are increasingly common freshwater ecosystems, but there have been no global syntheses of their community patterns. In this study, we examined the responses of aquatic invertebrate communities to flow intermittence in 14 rivers from multiple biogeographic regions covering a wide range of flow intermittence and spatial arrangements...

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...

Aquatic environments in the Madrean Sky Islands (MSI) consist of a matrix of perennial and intermittent stream segments, seasonal ponds, and human-built cattle trough habitats that support a diverse suite of aquatic macroinvertebrates. Although environmental conditions and aquatic communities are generally distinct in lotic and lentic habitats, MSI...

Dispersal is an essential process in metapopulation and metacommunity dynamics. Most studies of aquatic invertebrate dispersal in streams have focused on in-stream drift of larvae. However, understanding aerial dispersal is important for predicting community assembly in isolated habitats after disturbance or stream restoration. We used artificial p...

Large and severe wildfires can dramati-cally alter terrestrial and aquatic ecosystems. We documented changes in benthic macroinvertebrate communities and physical habitat at two sites along Angora Creek, CA, USA for 2 years following a severe fire. Although post-fire years had low precip-itation, canopy cover and bank stability declined dramaticall...

Background/Question/Methods Climate change and water withdrawals in arid regions are causing once-perennial streams to fragment or dry completely. One of the most notable changes accompanying this transition is the disappearance of aquatic top predators, such as fish and large-bodied invertebrates. These local extinctions presumably change stream...

1. Stream and riparian ecosystems in arid montane areas, like the interior western United States, are often just narrow mesic strands, but support diverse and productive habitats. Meadows along many such streams have long been used for rangeland grazing, and, while impacts to riparian areas are relatively well known, the effect of livestock grazing...

1. Ecological communities can be relatively stable for long periods of time, and then, often as a result of disturbance, transition rapidly to a novel state. When communities fail to recover to pre-disturbance configurations, they are said to have experienced a regime shift or to be in an alternative stable state. 2. In this 8-year study, we quanti...