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1. Single-Species Co-management Improves Fish Assemblage Structure and Composition in a Tropical River

   https://doi.org/10.3389/fevo.2021.604170  

   Medeiros-Leal, Wendell M. ; Castello, Leandro ; Freitas, Carlos E. ; Siqueira-Souza, Flávia K. ( March 2021 , Frontiers in Ecology and Evolution)

   Co-management is increasingly recognized as an effective model for managing fisheries, but little information exists on whether co-management can produce effects in species other than the target species. Fishery co-management in the tropics, where fish diversity is high and fish catches tend to be multispecies, is prone to produce assemblage-wide effects via alterations in the food web and changes in the overall capture of non-target species. Here, we assessed the effects of co-management for the species Arapaima sp. in relation to the structure and composition of the overall fish assemblage in floodplain lakes of the central Amazon Basin. These floodplain lakes are managed under a system of zoning of fishing activities. We used data from surveys of six floodplain lakes, including two lakes of each of three categories (lakes where fishing is prohibited, limited-access lakes, and open fishing lakes). The surveys were carried out before and after implementation of co-management, through gillnet fishing. The study area was the lower Solimões River, in the Amazon Basin, Brazil. Statistical models showed significant changes in the composition and structure of the fish assemblages after the implementation of the co-management, regardless of the zoning category. Through regulation of gear use and fishing practices, co-managementmore »allowed the colonization of species that had not been present before, which lead to higher richness and consequently increased fish sizes, abundance and biomass. Species of sedentary habits, migrants of short and medium distances, with commercial importance benefited the most from co-management. In the results presented in temporal scale, it was possible to observe a potential spillover effect being provided by the lakes where fishing is prohibited (no-take zones) and those of limited access that benefited those open to fishing. Thus, co-management had positive effects in the structure and composition of fish assemblages in all lakes, regardless of zoning category.« less
2. Recent lineage diversification in a venomous snake through dispersal across the Amazon River

   GIBBS, HL. ( January 2018 , Biological Journal of the Linnean Society)

   Identifying the evolutionary and ecological mechanisms that drive lineage diversification in the species-rich tropics is of broad interest to evolutionary biologists. Here, we use phylogeographic and demographic analyses of genomic scale RADseq data to assess the impact of a large geographic feature, the Amazon River, on lineage formation in a venomous pitviper, Bothrops atrox. We compared genetic differentiation in samples from four sites near Santarem, Brazil that spanned the Amazon and represented major habitat types. A species delimitation analysis identified each population as a distinct evolutionary lineage while a species tree analysis with populations as taxa revealed a phylogenetic tree consistent with dispersal across the Amazon from north to south. Phylogenetic analyses of mtDNA variation confirmed this pattern and suggest that all lineages originated during the mid- to late-Pleistocene. Historical demographic analyses support a population model of lineage formation through isolation between lineages with low ongoing migration between large populations and reject a model of differentiation through isolation by distance alone. Our results provide a rare example of a phylogeographic pattern demonstrating dispersal over evolutionary time scales across a large tropical river and suggest a role for the Amazon River as a driver of in-situ divergence by both impeding (butmore »not preventing) gene flow and through parapatric differentiation along an ecological gradient.« less
3. Metabolic asymmetry and the global diversity of marine predators

   https://doi.org/10.1126/science.aat4220  

   Grady, John M. ; Maitner, Brian S. ; Winter, Ara S. ; Kaschner, Kristin ; Tittensor, Derek P. ; Record, Sydne ; Smith, Felisa A. ; Wilson, Adam M. ; Dell, Anthony I. ; Zarnetske, Phoebe L. ; et al ( January 2019 , Science)

   Species richness of marine mammals and birds is highest in cold, temperate seas—a conspicuous exception to the general latitudinal gradient of decreasing diversity from the tropics to the poles. We compiled a comprehensive dataset for 998 species of sharks, fish, reptiles, mammals, and birds to identify and quantify inverse latitudinal gradients in diversity, and derived a theory to explain these patterns. We found that richness, phylogenetic diversity, and abundance of marine predators diverge systematically with thermoregulatory strategy and water temperature, reflecting metabolic differences between endotherms and ectotherms that drive trophic and competitive interactions. Spatial patterns of foraging support theoretical predictions, with total prey consumption by mammals increasing by a factor of 80 from the equator to the poles after controlling for productivity.
4. Narrow thermal tolerance and low dispersal drive higher speciation in tropical mountains

   https://doi.org/10.1073/pnas.1809326115  

   Polato, Nicholas R. ; Gill, Brian A. ; Shah, Alisha A. ; Gray, Miranda M. ; Casner, Kayce L. ; Barthelet, Antoine ; Messer, Philipp W. ; Simmons, Mark P. ; Guayasamin, Juan M. ; Encalada, Andrea C. ; et al ( November 2018 , Proceedings of the National Academy of Sciences)

   Species richness is greatest in the tropics, and much of this diversity is concentrated in mountains. Janzen proposed that reduced seasonal temperature variation selects for narrower thermal tolerances and limited dispersal along tropical elevation gradients [Janzen DH (1967)Am Nat101:233–249]. These locally adapted traits should, in turn, promote reproductive isolation and higher speciation rates in tropical mountains compared with temperate ones. Here, we show that tropical and temperate montane stream insects have diverged in thermal tolerance and dispersal capacity, two key traits that are drivers of isolation in montane populations. Tropical species in each of three insect clades have markedly narrower thermal tolerances and lower dispersal than temperate species, resulting in significantly greater population divergence, higher cryptic diversity, higher tropical speciation rates, and greater accumulation of species over time. Our study also indicates that tropical montane species, with narrower thermal tolerance and reduced dispersal ability, will be especially vulnerable to rapid climate change.
5. Conserved ancestral tropical niche but different continental histories explain the latitudinal diversity gradient in brush-footed butterflies

   https://doi.org/10.1038/s41467-021-25906-8  

   Chazot, Nicolas ; Condamine, Fabien L. ; Dudas, Gytis ; Peña, Carlos ; Kodandaramaiah, Ullasa ; Matos-Maraví, Pável ; Aduse-Poku, Kwaku ; Elias, Marianne ; Warren, Andrew D. ; Lohman, David J. ; et al ( September 2021 , Nature Communications)

   The global increase in species richness toward the tropics across continents and taxonomic groups, referred to as the latitudinal diversity gradient, stimulated the formulation of many hypotheses to explain the underlying mechanisms of this pattern. We evaluate several of these hypotheses to explain spatial diversity patterns in a butterfly family, the Nymphalidae, by assessing the contributions of speciation, extinction, and dispersal, and also the extent to which these processes differ among regions at the same latitude. We generate a time-calibrated phylogeny containing 2,866 nymphalid species (~45% of extant diversity). Neither speciation nor extinction rate variations consistently explain the latitudinal diversity gradient among regions because temporal diversification dynamics differ greatly across longitude. The Neotropical diversity results from low extinction rates, not high speciation rates, and biotic interchanges with other regions are rare. Southeast Asia is also characterized by a low speciation rate but, unlike the Neotropics, is the main source of dispersal events through time. Our results suggest that global climate change throughout the Cenozoic, combined with tropical niche conservatism, played a major role in generating the modern latitudinal diversity gradient of nymphalid butterflies.