Major changes to local river habitats, after impoundment, are expected to restrict the reproductive activity of fishes with migratory strategies, although the changes are not expected to have relevant effects on fishes with other strategies. The reproductive activity of fishes with different reproductive strategies was evaluated along a longitudinal gradient before, and after, the formation of a reservoir on the Tocantins River (Tocantins State, Brazil). Samples were collected at six sites distributed along 80‐km stretch of the reservoir (R1 to R6 in the upstream–downstream direction) before and after the impoundment. The highest mean values of the reproductive activity index (RAI), considering all species in the river phase, were recorded for the intermediate segments (R4). The reproductive activity was classified as intense at the two sites located further upstream (R2 and R1). The highest mean RAI value after impoundment was observed for the site further upstream (R1). The reproductive activity was classified as intense, however, at every site, except for R6. Regardless of the reproductive strategy, mean RAI values were higher in this phase at site R1, particularly for long‐distance migratory species (LDM). The most lacustrine area (R6) was only relevant for the group of species with parental care. For non‐long‐distance migratory species, without parental care, the reproductive activity was intense at every site, except for R6. Overall, after the impoundment, the fish species tended to seek more lotic environments to spawn, including the riverine zone of the reservoir and side tributaries, regardless of the reproductive strategy. The results of this study provide evidence that impoundments affect the reproduction of the fish, independent of the reproductive strategy, although the intensity of the effect is different for each group.

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Anthropogenic impacts are altering ecosystems, especially aquatic habitats, resulting in the loss of critical biodiversity. This study aimed to evaluate the influence of human pressure, as surrogated by the human footprint index (HFI), on the functional diversity of fish assemblages from 109 Neotropical reservoirs while considering covariates such as temperature, flooded area and age since damming. We assessed two components of functional diversity (richness and dispersion) and the specific trait composition of each fish assemblage. We found that both components of fish functional diversity decreased with increasing human pressure and that this relationship was stronger in reservoirs near large cities. There was a positive relationship between functional diversity and reservoir area, and a negative relationship between functional diversity and reservoir age. We also observed strong relationships between all the explanatory variables and functional traits, particularly for the HFI. We can infer that the ichthyofaunas of those reservoirs under higher human pressure are likely undergoing a simplification process along with homogenization of functional diversity.

The flood pulse is the main driving force for communities' structure and functioning in river-floodplain systems. High synchrony exists between the hydrological cycle and reproductive cycle events for several fish species. However, species with different reproductive strategies can respond in different ways to the flood regime. Thus, this study intends to evaluate the relationship between the recruitment of different reproductive guilds of freshwater fish and flood attributes (flood duration, maximum annual water level, and delay of flood) from a time series of 20 years in the Upper Paraná River floodplain, Brazil. The abundance of four guilds was evaluated: (i) long-distance migratory with external fertilization and without parental care (LMEF); (ii) non-migratory or short-distance migratory with external fertilization and without parental care (NEFW); (iii) non-migratory or short-distance migratory with external fertilization and parental care (NEFP); and (iv) non-migratory or short-distance migratory with internal fertilization and without parental care (NIF). Multiple regression analyses were applied between flood attributes and abundance of young-of-the-year or juveniles for each reproductive guild. This study observed a consistent pattern of long-lasting flooding positively influencing the recruitment of all reproductive guilds, while water level intensity and the time of the onset of flooding also influenced some non-migratory strategies. We can conclude that the conservation of fish populations and the maintenance of ecosystem functions and services associated with them need to be considered in the operating protocols of upstream hydroelectric plants, since they are dependent on the flooding controlled by them.

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Human activities affecting freshwater ecosystems, such as regulation of rivers by dams and introduction of non‐native species, are recognised as major threats to freshwater biodiversity, with fish communities strongly impacted. We evaluated patterns of functional diversity of native and non‐native species in local fish assemblages in the upper Paraná River floodplain over a 33‐year period (1986–2019) in three rivers with different degrees of alteration by dams (highly altered, moderately altered, and little altered). We also examined the effect of non‐native species on functional diversity of native species and investigated the responses of functional traits of native and non‐native fishes in regions with different histories of flow alteration. We measured 13 functional traits associated with five niche dimensions: feeding, habitat use, metabolism, life history, and defence. Functional diversity was evaluated from functional richness, functional redundancy, and Rao's quadratic entropy. The effect of non‐native species on functional diversity indices of native species was evaluated using a simple linear regression between each index and the level of dominance by non‐native species. To evaluate changes in functional traits of native and non‐native species over time and among rivers, we performed an RLQ analysis. Functional richness and Rao's quadratic entropy of native species decreased over time, while functional redundance increased especially in the most altered river. The level of dominance by non‐native species was negatively associated with functional richness and Rao's quadratic entropy of native species. Native species that are migratory with high fecundity, single spawning events and large body size were most common during the first 2 decades and within the least altered river. Non‐native species with parental care, multiple spawning, relatively large eggs, and brood defence tended to have greater prevalence during the last 2 decades and within the moderately altered region. Comparison of temporal trends in the functional diversity and characteristics of native and non‐native fishes within regions of the upper Paraná River floodplain having different levels of environmental alteration suggests that non‐native species and alteration by dams interact to adversely impact the functional diversity of native fishes, with especially strong effects on migratory fishes with a periodic life history strategy.

Uma revisão sistemática do impacto da Teoria da Rainha Vermelha (TRV) foi realizada desde o ano da sua formulação em 1973 até 2018. Publicada há 45 anos, a TRV tenta elucidar a manutenção do sexo ao longo da árvore da vida, considerando os custos inerentes aos envolvidos. O objetivo geral do trabalho foi identificar, tendências, lacunas e sistemas biológicos onde a TRV é válida em diferentes disciplinas relacionadas à biodiversidade. Houve uma frequência variável de citações e um aumento das publicações na última década. Quanto ao número de publicações, todos os principais países são ricos: Estados Unidos da América, Inglaterra e Suíça. As revistas de alto fator de impacto foram responsáveis por 30 % dos artigos publicados e os estudos de nível populacional, compostos por 70 % das publicações, provavelmente porque os artigos da TRV estudaram a coevolução interespecífica, quando abordados pela perspectiva ecológica. A maioria dos artigos focou em invertebrados e microorganismos, superando as publicações com vertebrados e plantas. As publicações abrangeram todas as disciplinas relacionadas com a biodiversidade, mas a Biologia Evolutiva e a Ecologia foram as mais predominantes. Isso demonstra o potencial aumento do impacto, visibilidade e discussão da teoria refletida em estudos de ciências naturais de longo prazo, contribuindo para o aumento do apoio financeiro e questões que abordam outros grupos taxonômicos e níveis ecológicos, tornando-se historicamente uma fonte de subsídio teórico de informação.

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