Size Matters, but Species Do Not: No Evidence for Species-Specific Swimming Performance in Co-Occurring Great Basin Stream Fishes

For fishes, swimming performance is an important predictor of habitat use and a critical measure for the design of effective fish passage systems. Few studies have examined burst and prolonged types of swimming performance among several co-occurring species, and swimming performance in many fish communities is undocumented. In this study, we characterize both burst (c-start velocity) and prolonged speed (critical swim speed) across a poorly documented, co-occurring group of stream fishes within the Great Basin of the western USA. We documented the variation in swim speed associated with species, habitat, and body size. Body size had an overwhelming effect on both burst speed and prolonged speed, whereas habitat use and species identity were not significant predictors. Among species, there is no evidence of a trade-off between burst swim speed and prolonged swim speed. Lack of a trade-off in performance between burst swim speed and prolonged swim speed among species may be due to unexpectedly high prolonged swim speeds exhibited by species that used substrate-bracing behaviors. Incorporating body size and variation in behavior, such as substrate-bracing behaviors, into fish passage models will likely be sufficient to ensure the passage of all species without the need to account for species-specific swimming abilities. However, these results characterize the swimming performance for threatened and common fish species such that other comparisons can be made and species-specific studies can access accurate data.

Metapopulation-level associations in mutualistic stream fishes

Positive biotic interactions are recognized as important factors determining species distributions. Although effects of positive interactions have often been observed at local scales, much less is known about consequences at larger spatial scales such as metapopulation dynamics. Here, we study nest associations of stream fishes - widespread reproductive mutualism between host (nest-builder) and beneficiary (nest associate) species in North America - as a model system to examine the role of positive interactions in determining the metapopulation-level association between host and beneficiary species. Using regional data of fish distribution in the Midwestern US, we found that watershed-level occupancy of host species (i.e., metapopulation occupancy) remarkably increased that of nest associates. Importantly, our results illustrated that the effects of positive biotic interactions at the metapopulation level were comparable or even stronger than environmental drivers, i.e., factors that have been studied most extensively in metapopulation studies. This study provides insightful evidence that positive biotic interactions have large-scale consequences for distributions of organisms than previously thought. Successful biodiversity conservation may need a broader framework that appreciates the role of positive biotic interactions at larger spatial scales.

ECOLOGIA FILOGENÉTICA DE COMUNIDADES DE PEIXES DE RIACHO NEOTROPICAIS

Neotropical stream fishes exhibit a complex evolutionary history and encompass both old and recent lineages. Patterns of species diversity of stream fishes are relatively well-studied for Neotropical streams, but not for patterns of clade distribution and historical factors that structure these assemblages, which are the main interests of phylogenetic ecology. Understanding the evolutionary context of communities provides important insights into large-scale mechanisms that structure them. This review aims to: (i) discuss the main concepts of phylogenetic ecology and its application to Neotropical stream fishes; and (ii) highlight the main methods applied in this background. The first section presents the main phylogenetic hypothesis of fishes and discusses how their gaps in Neotropical stream fishes hinder phylogenetic ecology. Afterward, we discuss the main concepts of phylogenetic ecology (phylogenetic signal, community phylogenetic structure, and phylogenetic diversity), as well as gaps and potential applications of these concepts and tools to understand Neotropical stream fish assemblages. The second section introduces the main methods to address the phylogenetic ecology, including a standardized procedure to edit fish phylogenetic trees, comparative methods, and indices and analytical tools to understand community structure and conservation importance. Finally, we discuss the perspectives to the next years to better understand the Neotropical stream fish assemblages in the light of past and current historical processes.

ECOLOGIA TRÓFICA DE PEIXES DE RIACHO: UMA RELEITURA 20 ANOS DEPOIS

The great extent and diversity of ecological conditions of stream ecosystems in Brazil are widely recognized. In the last two decades, studies on stream fishes have contributed to the knowledge about their trophic ecology. However, the large amount of available information is yet fragmented. This chapter presents the state of the art of studies about feeding and trophic ecology of stream fishes in Brazil, an essential topic to understand ecosystem functioning. The review presented here was based on searches on different databases (Scopus, Web of Science, ASFA and Scielo). Results included studies that used different methods and approaches to evaluate the diet of fish species and assemblages, their relationship with morphology and ontogenetic variation, resource partitioning, seasonal and spatial variations, and anthropic impacts on trophic interactions. Finally, knowledge gaps and perspectives for future studies on fish trophic ecology are pointed out, including responses to anthropic influences, theoretical aspects, and the use of underexplored approaches to the subject, which may aid to our understanding of tropical streams

AVANÇOS EM MÉTODOS DE COLETA DE PEIXES E CARACTERIZAÇÃO DE HABITAT DE RIACHOS TROPICAIS

This paper brings some advances in fish data sampling and stream environments. Since the publication in 1999 of volume VI “Ecology of Stream Fishes” in the former Oecologia Brasiliensis journal, today Oecologia Australis, several progresses have occurred. Several methods of collecting fish themselves, have remained the same. However, in relation to the use of electric fishing, collection of eggs and fish larvae, and characterization of physical habitats in streams, there was remarkable development and improvement. The purpose of this article is to present the “state of the art” of these three aspects of sampling fish and habitats in streams. By the end, preparation methods of samples for genetic, stable isotopes and heavy metal analyses are briefly presented

IDADE E CRESCIMENTO DE PEIXES DE RIACHO: MÉTODOS E DESAFIOS PARA A OBTENÇÃO DE ESTIMATIVAS ROBUSTAS

Age and growth are key elements on the fish population dynamics, allowing the age structure identification, age of first maturity, mortality rates and longevity calculations, among others. There are also age-based fisheries and ecological models that depends on these studies. It is a challenger field due to the intrinsic variability of growth process at individual and population levels, influenced by endogen and exogen factors. For freshwater fishes, the modal progression analysis, and the analysis of growth rings on scales are widespread applied for age and growth. Like all methods, premises and limitations exist and they must be observed. Otolith analysis is more accurate, unless difficult to stream fishes due to sample size requirements, small otolith size and rings record, specially at the Neotropical region. In this study, sample techniques, material and data acquirement and analyses are presented, focusing stream fishes. Limitations were identified in the results available in the scientific literature due to no consideration of methods premises allied to the mechanic use of software and manuals. For further studies, length frequency analysis, otolith daily rings and experiments are recommended to estimate age and growth of fishes from brooks and streams.

Widespread convergence in stream fishes

Convergent evolution, the evolution of similar phenotypes among distantly related lineages, is often attributed to adaptation in response to similar selective pressures. Here, we assess the prevalence and degree of convergence in functional traits of stream fishes at the microhabitat scale in five zoogeographical regions across the world. We categorized species by microhabitat, water velocity and preference for substrate complexity and calculated the prevalence of convergence, degree of convergence and functional diversity for each category. Among species occupying similar microhabitats of small, low-gradient streams, 34% had combinations of convergent traits. Convergence occurred at higher rates than expected by chance alone, implying that adaptation to similar environmental conditions often resulted in similar evolutionary patterns along multiple niche dimensions. Two of the microhabitat groupings had significantly convergent species represented in all zoogeographical regions. Fishes occupying microhabitats with high water velocity and low structural complexity generally occupied a restricted morphospace and exhibited greater prevalence and higher degrees of convergence. This suggests that water velocity and habitat structural complexity interact, selecting a restricted distribution of trait distributions and higher degrees of convergence in stream fish assemblages. Furthermore, these results suggest that microhabitat features in streams select for fish trait distributions in a fairly predictable and deterministic manner worldwide.

The discovery of a microbialite-associated freshwater fish in the world’s largest saline soda lake, Lake Van (Turkey)

Lake Van is the largest saline soda lake in the world and one of the world’s few endorheic lakes of greater than 3,000 km2 surface area. Despite its huge size, no fish species have so far been known to permanently occur in this lake due to its extreme environmental conditions. Here, we report the discovery of a fish population that permanently inhabits some of the unique microbialites of the lake, at a maximum depth of 13 m and about 500 m offshore. We tested whether this is an undescribed species or a new occurrence of a known species. A molecular and morphological examination showed that the newly discovered fish represents an isolated population of Oxynoemacheilus ercisianus, the only nemacheilid loach native to the freshwater tributaries of the Lake Van endorheic basin. Our further hypotheses on the prediction that (a) stream fishes would have a more anterior placement of fins than lake fishes were supported; but, that (b) stream fishes would be more slender bodied than their lake conspecifics was not supported. The lake dwelling population also shows very small sequence divergence (0.5% K2P distance) to its stream dwelling conspecific in the mtDNA-COI barcode region. The notable morphological difference with minute molecular divergence implies that the newly discovered population might have lost its link to freshwater during desiccation and transgressional phases of the Lake Van, and has adapted to a life on the microbialites.