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• 1. [Article] Fish Species Introductions Provide Novel Insights into the Patterns and Drivers of Phylogenetic Structure in Freshwaters

  Despite long-standing interest of terrestrial ecologists, freshwater ecosystems are a fertile, yet unappreciated, testing ground for applying community phylogenetics to uncover mechanisms of species assembly. ...

  Citation × Citation Citation Abstract Copy Title: Fish Species Introductions Provide Novel Insights into the Patterns and Drivers of Phylogenetic Structure in Freshwaters Author: Strecker, Angela L., Olden, Julian D. Year: 2014 Despite long-standing interest of terrestrial ecologists, freshwater ecosystems are a fertile, yet unappreciated, testing ground for applying community phylogenetics to uncover mechanisms of species assembly. We quantify phylogenetic clustering and overdispersion of native and non-native fishes of a large river basin in the American Southwest to test for the mechanisms (environmental filtering versus competitive exclusion) and spatial scales influencing community structure. Contrary to expectations, non-native species were phylogenetically clustered and related to natural environmental conditions, whereas native species were not phylogenetically structured, likely reflecting human-related changes to the basin. The species that are most invasive (in terms of ecological impacts) tended to be the most phylogenetically divergent from natives across watersheds, but not within watersheds, supporting the hypothesis that Darwin's naturalization conundrum is driven by the spatial scale. Phylogenetic distinctiveness may facilitate non-native establishment at regional scales, but environmental filtering restricts local membership to closely related species with physiological tolerances for current environments. By contrast, native species may have been phylogenetically clustered in historical times, but species loss from contemporary populations by anthropogenic activities has likely shaped the phylogenetic signal. Our study implies that fundamental mechanisms of community assembly have changed, with fundamental consequences for the biogeography of both native and non-native species. Title: Fish Species Introductions Provide Novel Insights into the Patterns and Drivers of Phylogenetic Structure in Freshwaters Author: Strecker, Angela L., Olden, Julian D. Year: 2014 Despite long-standing interest of terrestrial ecologists, freshwater ecosystems are a fertile, yet unappreciated, testing ground for applying community phylogenetics to uncover mechanisms of species assembly. We quantify phylogenetic clustering and overdispersion of native and non-native fishes of a large river basin in the American Southwest to test for the mechanisms (environmental filtering versus competitive exclusion) and spatial scales influencing community structure. Contrary to expectations, non-native species were phylogenetically clustered and related to natural environmental conditions, whereas native species were not phylogenetically structured, likely reflecting human-related changes to the basin. The species that are most invasive (in terms of ecological impacts) tended to be the most phylogenetically divergent from natives across watersheds, but not within watersheds, supporting the hypothesis that Darwin's naturalization conundrum is driven by the spatial scale. Phylogenetic distinctiveness may facilitate non-native establishment at regional scales, but environmental filtering restricts local membership to closely related species with physiological tolerances for current environments. By contrast, native species may have been phylogenetically clustered in historical times, but species loss from contemporary populations by anthropogenic activities has likely shaped the phylogenetic signal. Our study implies that fundamental mechanisms of community assembly have changed, with fundamental consequences for the biogeography of both native and non-native species. Close

• 2. [Article] The Interplay Between Landscape Structure and Biotic Interactions

  Landscape structure and biotic interactions are closely linked. We identify five aspects of landscape structure that contribute to the co-occurrence of species and restrict or enable different types of ...

  Citation × Citation Citation Abstract Copy Title: The Interplay Between Landscape Structure and Biotic Interactions Author: Zarnetske, Phoebe, Baiser, Benjamin, Strecker, Angela L., Record, Sydne, Belmaker, Jonathan, Tuanmu, Mao-Ning Year: 2017 Landscape structure and biotic interactions are closely linked. We identify five aspects of landscape structure that contribute to the co-occurrence of species and restrict or enable different types of biotic interactions: patch size and habitat amount, isolation of patches, barriers to dispersal and movement, persistence of landscape structure, and landscape complexity. In addition, these aspects of landscape structure influence the strength and outcome of biotic interactions. Whereas most research focuses on the effects of the abiotic environment on species and their biotic interactions, research on foundation species and ecosystem engineers demonstrates the important influence of biotic interactions on landscape structure itself, including effects on landscape complexity, extent of habitat, and the structure of landscape features. In this review, we describe ecological theories that lay the foundation for interplay between landscape structure and biotic interactions, and summarize these connections across an array of interacting species in freshwater, marine, and terrestrial systems. We end with suggestions for integrating the fields of landscape ecology and community ecology to better understand the connections between landscape structure and biotic interactions and better predict their dynamics in light of global change. Title: The Interplay Between Landscape Structure and Biotic Interactions Author: Zarnetske, Phoebe, Baiser, Benjamin, Strecker, Angela L., Record, Sydne, Belmaker, Jonathan, Tuanmu, Mao-Ning Year: 2017 Landscape structure and biotic interactions are closely linked. We identify five aspects of landscape structure that contribute to the co-occurrence of species and restrict or enable different types of biotic interactions: patch size and habitat amount, isolation of patches, barriers to dispersal and movement, persistence of landscape structure, and landscape complexity. In addition, these aspects of landscape structure influence the strength and outcome of biotic interactions. Whereas most research focuses on the effects of the abiotic environment on species and their biotic interactions, research on foundation species and ecosystem engineers demonstrates the important influence of biotic interactions on landscape structure itself, including effects on landscape complexity, extent of habitat, and the structure of landscape features. In this review, we describe ecological theories that lay the foundation for interplay between landscape structure and biotic interactions, and summarize these connections across an array of interacting species in freshwater, marine, and terrestrial systems. We end with suggestions for integrating the fields of landscape ecology and community ecology to better understand the connections between landscape structure and biotic interactions and better predict their dynamics in light of global change. Close

• 3. [Article] Defining Conservation Priorities for Freshwater Fishes According to Taxonomic, Functional, and Phylogenetic Diversity

  To date, the predominant use of systematic conservation planning has been to evaluate and conserve areas of high terrestrial biodiversity. Although studies in freshwater ecosystems have received recent ...

  Citation × Citation Citation Abstract Copy Title: Defining Conservation Priorities for Freshwater Fishes According to Taxonomic, Functional, and Phylogenetic Diversity Author: Strecker, Angela L., Olden, Julian D., Whittier, Joanna B., Paukert, Craig Patrick Year: 2011 To date, the predominant use of systematic conservation planning has been to evaluate and conserve areas of high terrestrial biodiversity. Although studies in freshwater ecosystems have received recent attention, research has rarely considered the potential trade-offs between protecting different dimensions of biodiversity and the ecological processes that maintain diversity. We provide the first systematic prioritization for freshwaters (focusing on the highly threatened and globally distinct fish fauna of the Lower Colorado River Basin, USA) simultaneously considering scenarios of: taxonomic, functional, and phylogenetic diversity; contemporary threats to biodiversity (including interactions with nonnative species); and future climate change and human population growth. There was 75% congruence between areas of highest conservation priority for different aspects of biodiversity, suggesting that conservation efforts can concurrently achieve strong complementarity among all types of diversity. However, sizable fractions of the landscape were incongruent across conservation priorities for different diversity scenarios, underscoring the importance of considering multiple dimensions of biodiversity and highlighting catchments that contribute disproportionately to taxonomic, functional, and phylogenetic diversity in the region. Regions of projected human population growth were not concordant with conservation priorities; however, higher human population abundance will likely have indirect effects on native biodiversity by increasing demand for water. This will come in direct conflict with projected reductions in precipitation and warmer temperatures, which have substantial overlap with regions of high contemporary diversity. Native and endemic fishes in arid ecosystems are critically endangered by both current and future threats, but our results highlight the use of systematic conservation planning for the optimal allocation of limited resources that incorporates multiple and complementary conservation values describing taxonomic, functional, and phylogenetic diversity. Title: Defining Conservation Priorities for Freshwater Fishes According to Taxonomic, Functional, and Phylogenetic Diversity Author: Strecker, Angela L., Olden, Julian D., Whittier, Joanna B., Paukert, Craig Patrick Year: 2011 To date, the predominant use of systematic conservation planning has been to evaluate and conserve areas of high terrestrial biodiversity. Although studies in freshwater ecosystems have received recent attention, research has rarely considered the potential trade-offs between protecting different dimensions of biodiversity and the ecological processes that maintain diversity. We provide the first systematic prioritization for freshwaters (focusing on the highly threatened and globally distinct fish fauna of the Lower Colorado River Basin, USA) simultaneously considering scenarios of: taxonomic, functional, and phylogenetic diversity; contemporary threats to biodiversity (including interactions with nonnative species); and future climate change and human population growth. There was 75% congruence between areas of highest conservation priority for different aspects of biodiversity, suggesting that conservation efforts can concurrently achieve strong complementarity among all types of diversity. However, sizable fractions of the landscape were incongruent across conservation priorities for different diversity scenarios, underscoring the importance of considering multiple dimensions of biodiversity and highlighting catchments that contribute disproportionately to taxonomic, functional, and phylogenetic diversity in the region. Regions of projected human population growth were not concordant with conservation priorities; however, higher human population abundance will likely have indirect effects on native biodiversity by increasing demand for water. This will come in direct conflict with projected reductions in precipitation and warmer temperatures, which have substantial overlap with regions of high contemporary diversity. Native and endemic fishes in arid ecosystems are critically endangered by both current and future threats, but our results highlight the use of systematic conservation planning for the optimal allocation of limited resources that incorporates multiple and complementary conservation values describing taxonomic, functional, and phylogenetic diversity. Close

• 4. [Article] Invasive Predator, Bythotrephes, has Varied Effects on Ecosystem Function in Freshwater Lakes

  Bythotrephes longimanus is an invertebrate predator that has invaded the North American Great Lakes and a number of inland lakes, where it preys on crustacean zooplankton. We examined the effect of Bythotrephes ...

  Citation × Citation Citation Abstract Copy Title: Invasive Predator, Bythotrephes, has Varied Effects on Ecosystem Function in Freshwater Lakes Author: Strecker, Angela L., Arnott, Shelley E. Year: 2008 Bythotrephes longimanus is an invertebrate predator that has invaded the North American Great Lakes and a number of inland lakes, where it preys on crustacean zooplankton. We examined the effect of Bythotrephes on two measures of ecosystem function during a four month observational study of freshwater lakes on the boreal shield. Bythotrephes-invaded lakes had significantly lower epilimnetic zooplankton abundance and production compared to reference lakes. On average, Bythotrephes consumed 34% ofzooplankton production when it was present in lakes. There was some evidence of changes in the timing of zooplankton production, as well as shifts to cooler, less productive habitats, which may lessen the overall effect of the invader on the transfer of energy to higher trophic levels. We experimentally demonstrated a weak trophic cascade where invader predation reduced zooplankton biomass, and subsequently increased phytoplankton growth. However, the response was small in magnitude and not biologically relevant at the whole lake- scale. The most conspicuous effect of Bythotrephes that we measured was a diversion of energy away from native predators at higher trophic levels. Title: Invasive Predator, Bythotrephes, has Varied Effects on Ecosystem Function in Freshwater Lakes Author: Strecker, Angela L., Arnott, Shelley E. Year: 2008 Bythotrephes longimanus is an invertebrate predator that has invaded the North American Great Lakes and a number of inland lakes, where it preys on crustacean zooplankton. We examined the effect of Bythotrephes on two measures of ecosystem function during a four month observational study of freshwater lakes on the boreal shield. Bythotrephes-invaded lakes had significantly lower epilimnetic zooplankton abundance and production compared to reference lakes. On average, Bythotrephes consumed 34% ofzooplankton production when it was present in lakes. There was some evidence of changes in the timing of zooplankton production, as well as shifts to cooler, less productive habitats, which may lessen the overall effect of the invader on the transfer of energy to higher trophic levels. We experimentally demonstrated a weak trophic cascade where invader predation reduced zooplankton biomass, and subsequently increased phytoplankton growth. However, the response was small in magnitude and not biologically relevant at the whole lake- scale. The most conspicuous effect of Bythotrephes that we measured was a diversion of energy away from native predators at higher trophic levels. Close

• 5. [Article] The Aquarium Trade as an Invasion Pathway in the Pacific Northwest

  The aquarium trade moves thousands of species around the globe, and unwanted organisms may be released into freshwaters, with adverse ecological and economic effects. We report on the first investigation ...

  Citation × Citation Citation Abstract Copy Title: The Aquarium Trade as an Invasion Pathway in the Pacific Northwest Author: Strecker, Angela L., Campbell, Philip M., Olden, Julian D. Year: 2011 The aquarium trade moves thousands of species around the globe, and unwanted organisms may be released into freshwaters, with adverse ecological and economic effects. We report on the first investigation of the ornamental pet trade as an invasion pathway in the Pacific Northwest region of the United States, where a moderate climate and a large human population present ample opportunities for the introduction and establishment of aquarium trade species. Results from a regional survey of pet stores found that the number of fish (n=400) and plant (n=124) species currently in the aquarium trade is vast. Pet stores import thousands of fish every month, the majority of which (58%) are considered to pose an ecological threat to native ecosystems. Our propagule pressure model suggests that approximately 2,500 fish (maximum 21,000 individuals) are likely released annually to the Puget Sound region by aquarists, and that water temperatures in many parts of Washington are suitable for establishment of populations. In conclusion, the aquarium trade may be a significant source of past and future invasions in the Pacific Northwest, and we recommend enhanced public education programs, greater regulation of the aquarium industry, and improved legislation of nonnative species in the ornamental trade. Title: The Aquarium Trade as an Invasion Pathway in the Pacific Northwest Author: Strecker, Angela L., Campbell, Philip M., Olden, Julian D. Year: 2011 The aquarium trade moves thousands of species around the globe, and unwanted organisms may be released into freshwaters, with adverse ecological and economic effects. We report on the first investigation of the ornamental pet trade as an invasion pathway in the Pacific Northwest region of the United States, where a moderate climate and a large human population present ample opportunities for the introduction and establishment of aquarium trade species. Results from a regional survey of pet stores found that the number of fish (n=400) and plant (n=124) species currently in the aquarium trade is vast. Pet stores import thousands of fish every month, the majority of which (58%) are considered to pose an ecological threat to native ecosystems. Our propagule pressure model suggests that approximately 2,500 fish (maximum 21,000 individuals) are likely released annually to the Puget Sound region by aquarists, and that water temperatures in many parts of Washington are suitable for establishment of populations. In conclusion, the aquarium trade may be a significant source of past and future invasions in the Pacific Northwest, and we recommend enhanced public education programs, greater regulation of the aquarium industry, and improved legislation of nonnative species in the ornamental trade. Close

• 6. [Article] Impact of Bythotrephes Invasion on Zooplankton Communities in Acid-Damaged and Recovered Lakes on the Boreal Shield

  Invasive species introductions into freshwater ecosystems have had a multitude of effects on aquatic communities. Few studies, however, have directly compared the impact of an invader on communities with ...

  Citation × Citation Citation Abstract Copy Title: Impact of Bythotrephes Invasion on Zooplankton Communities in Acid-Damaged and Recovered Lakes on the Boreal Shield Author: Strecker, Angela L., Arnott, Shelley E. Year: 2005 Invasive species introductions into freshwater ecosystems have had a multitude of effects on aquatic communities. Few studies, however, have directly compared the impact of an invader on communities with contrasting structure. Historically high levels and subsequent reductions of acid deposition have produced landscapes of lakes of varying acidity and zooplankton communitystructure. We conducted a 30-day enclosure experiment in Killarney Provincial Park, Ontario, Canada, to test the effects ofBythotrephes longimanus, an invasive invertebrate predator, on two contrasting zooplankton communities at different stages of recovery from acidification: recovered and acid damaged. Bythotrephes significantly decreased zooplankton biomass and abundance in both communities but had a greater negative effect on the abundance of zooplankton in the recovered community.Bythotrephes reduced species diversity of the recovered zooplankton community but not of the acid-damaged community. Species richness of both community types was unaffected by Bythotrephes predation. The effect of Bythotrephes on small cladocerans, a preferred prey type, differed between the community types and appeared to be related to density-dependent predation byBythotrephes. Both community- and species-level results suggest that recovered and acid-damaged zooplankton assemblages may be negatively affected by an invasion of Bythotrephes but that the specific response is dependent on the original community structure. Title: Impact of Bythotrephes Invasion on Zooplankton Communities in Acid-Damaged and Recovered Lakes on the Boreal Shield Author: Strecker, Angela L., Arnott, Shelley E. Year: 2005 Invasive species introductions into freshwater ecosystems have had a multitude of effects on aquatic communities. Few studies, however, have directly compared the impact of an invader on communities with contrasting structure. Historically high levels and subsequent reductions of acid deposition have produced landscapes of lakes of varying acidity and zooplankton communitystructure. We conducted a 30-day enclosure experiment in Killarney Provincial Park, Ontario, Canada, to test the effects ofBythotrephes longimanus, an invasive invertebrate predator, on two contrasting zooplankton communities at different stages of recovery from acidification: recovered and acid damaged. Bythotrephes significantly decreased zooplankton biomass and abundance in both communities but had a greater negative effect on the abundance of zooplankton in the recovered community.Bythotrephes reduced species diversity of the recovered zooplankton community but not of the acid-damaged community. Species richness of both community types was unaffected by Bythotrephes predation. The effect of Bythotrephes on small cladocerans, a preferred prey type, differed between the community types and appeared to be related to density-dependent predation byBythotrephes. Both community- and species-level results suggest that recovered and acid-damaged zooplankton assemblages may be negatively affected by an invasion of Bythotrephes but that the specific response is dependent on the original community structure. Close

• 7. [Article] Dispersal Limitation and Climate-Related Environmental Gradients Structure Microcrustacean Composition in Freshwater Lakes, Ellesmere Island, Canada

  Dramatic environmental change is expected in the Arctic, yet little is known about the occurrence and community composition of microcrustaceans in Arctic lakes and how this will be influenced by future ...

  Citation × Citation Citation Abstract Copy Title: Dispersal Limitation and Climate-Related Environmental Gradients Structure Microcrustacean Composition in Freshwater Lakes, Ellesmere Island, Canada Author: Strecker, Angela L., Milne, Rebecca, Arnott, Shelley E. Year: 2008 Dramatic environmental change is expected in the Arctic, yet little is known about the occurrence and community composition of microcrustaceans in Arctic lakes and how this will be influenced by future environmental change. We sampled and calculated relative abundances of microcrustacean species in 54 lakes on Ellesmere Island, Canada. New species records on Ellesmere Island included Daphnia umbra, Tachidius discipes, and Artemeopsis stefanssoni. Daphnia middendorffiana/tenebrosa was the most common taxon and often dominated microcrustacean assemblages, likely a result of its pigmentation, which offers resistance to ultraviolet radiation. Species richness was positively associated with nutrients, dissolved organic carbon (DOC), temperature, calcium, and conductivity and negatively affected by elevation. In contrast to most findings in temperate systems, we detected a negative relationship between species richness and surface area. Community composition was influenced by DOC, nutrients, and elevation but was also related to spatial variables, suggesting that spatial gradients in environmental conditions and dispersal are important drivers of differences among sites. Arctic ecosystems are expected to change rapidly in the coming years because of climate change and ozone thinning, and we expect that associated changes in DOC, temperature, and nutrients will affect microcrustacean species richness and distribution throughout the landscape. Title: Dispersal Limitation and Climate-Related Environmental Gradients Structure Microcrustacean Composition in Freshwater Lakes, Ellesmere Island, Canada Author: Strecker, Angela L., Milne, Rebecca, Arnott, Shelley E. Year: 2008 Dramatic environmental change is expected in the Arctic, yet little is known about the occurrence and community composition of microcrustaceans in Arctic lakes and how this will be influenced by future environmental change. We sampled and calculated relative abundances of microcrustacean species in 54 lakes on Ellesmere Island, Canada. New species records on Ellesmere Island included Daphnia umbra, Tachidius discipes, and Artemeopsis stefanssoni. Daphnia middendorffiana/tenebrosa was the most common taxon and often dominated microcrustacean assemblages, likely a result of its pigmentation, which offers resistance to ultraviolet radiation. Species richness was positively associated with nutrients, dissolved organic carbon (DOC), temperature, calcium, and conductivity and negatively affected by elevation. In contrast to most findings in temperate systems, we detected a negative relationship between species richness and surface area. Community composition was influenced by DOC, nutrients, and elevation but was also related to spatial variables, suggesting that spatial gradients in environmental conditions and dispersal are important drivers of differences among sites. Arctic ecosystems are expected to change rapidly in the coming years because of climate change and ozone thinning, and we expect that associated changes in DOC, temperature, and nutrients will affect microcrustacean species richness and distribution throughout the landscape. Close

• 8. [Article] Variation in the Response of Crustacean Zooplankton Species Richness and Composition to the Invasive Predator Bythotrephes Longimanus

  The predacious invertebrate Bythotrephes longimanus has invaded >90 freshwater lakes in North America. There is some evidence that B. longimanus has a negative effect on summer zooplankton species richness; ...

  Citation × Citation Citation Abstract Copy Title: Variation in the Response of Crustacean Zooplankton Species Richness and Composition to the Invasive Predator Bythotrephes Longimanus Author: Strecker, Angela L., Arnott, Shelley E., Yan, Norman D., Girard, Robert Year: 2006 The predacious invertebrate Bythotrephes longimanus has invaded >90 freshwater lakes in North America. There is some evidence that B. longimanus has a negative effect on summer zooplankton species richness; however, no study has examined the effect of B. longimanus throughout the ice-free season in more than one lake. We visited 10 invaded and 4 reference lakes every 2 weeks from May to September, collecting B. longimanus, crustacean zooplankton, and water chemistry samples. Composite samples were pooled across the study season for each lake. Bythotrephes longimanus significantly reduced cladoceran species richness, diversity, and abundance, and the total zooplankton community also exhibited decreased richness, diversity, and abundance. Seasonal sampling was better than synoptic surveys at detecting changes in abundance, but richness estimates were similar. As B. longimanus continues to spread across lake landscapes, we expect it will have profound impacts on local and regional richness and species distribution patterns. Title: Variation in the Response of Crustacean Zooplankton Species Richness and Composition to the Invasive Predator Bythotrephes Longimanus Author: Strecker, Angela L., Arnott, Shelley E., Yan, Norman D., Girard, Robert Year: 2006 The predacious invertebrate Bythotrephes longimanus has invaded >90 freshwater lakes in North America. There is some evidence that B. longimanus has a negative effect on summer zooplankton species richness; however, no study has examined the effect of B. longimanus throughout the ice-free season in more than one lake. We visited 10 invaded and 4 reference lakes every 2 weeks from May to September, collecting B. longimanus, crustacean zooplankton, and water chemistry samples. Composite samples were pooled across the study season for each lake. Bythotrephes longimanus significantly reduced cladoceran species richness, diversity, and abundance, and the total zooplankton community also exhibited decreased richness, diversity, and abundance. Seasonal sampling was better than synoptic surveys at detecting changes in abundance, but richness estimates were similar. As B. longimanus continues to spread across lake landscapes, we expect it will have profound impacts on local and regional richness and species distribution patterns. Close