Description of Onthophagus humboldti and Uroxys bonplandi, two new scarab beetles (Coleoptera, Scarabaeidae, Scarabaeinae) from Costa Rica, with notes on tropical mountain brachyptery and endemicity.

Two new endemic species of scarab beetles are described from Costa Rica, Onthophagus humboldti sp. nov. and Uroxys bonplandi sp. nov. Onthophagus humboldti sp. nov. is also the tenth brachypterous Onthophagus species to be described worldwide, representing also a case of extreme brachyptery in Onthophagini. Illustrations for both new species, as well as marking differences with closely related species are included. Maps showing the distribution of the new species, as well as the distribution of brachypterous and endemic scarab-beetle species for Costa Rica are presented and discussed. The Cordillera de Talamanca represents an area where Scarabaeinae (four genera) show very high known levels of brachypterism in Mesoamerica. A reconstruction of the montane environment in the Cordillera de Talamanca during the Last Glacial Maximum (~24 ka) is analyzed, in order to try to understand a possible historical biogeography model that might promote high levels of brachypterism in scarab-beetles. The present study supports previous proposals that brachyptery is correlated with stable environments associated with deeply incised valleys. Tropical mountain ranges are also identified as having more endemics than lowland rain forests, contradicting accepted wisdom. Lastly, a mitochondrial DNA analysis supports the existence of the Onthophagus dicranius and the O. clypeatus species-groups as two well-defined and closely related branches.

Phylogenetic relationships and historical biogeography of Oligosarcus (Teleostei: Characidae): Examining riverine landscape evolution in southeastern South America.

The pike-characin Oligosarcus is a group of Characidae composed of 22 species, which have mostly allopatric distributed species in southeastern South America and sympatric occurrence of few species. Oligosarcus shares a similar distribution pattern with other fish genera and therefore, can help us to understand biogeographic events that influenced freshwater fish distribution in the southeastern South America. Our paper presents the most extensive taxonomic coverage for molecular analysis of Oligosarcus and uses various methods to examine the evolutionary history of the genus. Phylogenetic relationships among species of Oligosarcus were examined using a multilocus dataset by Maximum Likelihood and Bayesian methods. A relaxed molecular clock was used to estimate lineage divergence times, which provide a framework to examine the biogeographic history of this clade across the drainage basins of southeastern South America. Oligosarcus was resolved as monophyletic with strong support, and related to lineages currently assigned to the genus Astyanax. Within Oligosarcus, two groups of approximately equal species richness were resolved as monophyletic, mainly restricted to continental and coastal drainages of southeastern South America. Oligosarcus radiation is estimated to the late Neogene, with its origin in the Pliocene and most speciation events occurring in the Pleistocene. Some apomorphic characteristics associated with piscivory (e.g. large caniniform teeth) in Oligosarcus likely have evolved once, and are convergent to similar phenotypes observed in a distantly related clade of Astyanax (formerly Bramocharax). In addition, the presence of morphological convergence within the genus Oligosarcus (e.g. trophic morphology) seems to explain the difference between the present molecular hypothesis and some previous morphological studies. Ancestral geographical range estimation using analytical methods (e.g. DIVALIKE and DEC) demonstrated the effects of different Landscape Evolution Models (LEMs) on diversification of Oligosarcus. The results suggest that the two main Oligosarcus clades evolved in allopatry in continental and coastal drainages, with subsequent range extension and vicariance events that established the modern distributions. LEM analyses indicate the importance of formation of riverine barriers across the watershed of the La Plata basin and the effects of sea-level changes during the Pleistocene for delineating lineage distributions of Oligosarcus.

Historical biogeography of fishes from coastal basins of Maranhão State, northeastern Brazil

The Amazonian ichthyofauna is one of the most diverse in the world, yet fishes from the adjacent coastal basins of Maranhão State in Northeastern Brazil remain poorly known. We use phylogeographic, community phylogenetic and phylogenetic beta diversity methods to study the biogeographic history of fishes from the coastal basins of Maranhão State. We report a total of 160 fish species from the basins of the Maranhão region, representing a 93% increase over results of previous studies. All the fish species assemblages from Maranhão are polyphyletic, with only a few putative sister species pairs inhabiting the region. The modern watershed divides among Maranhão basins do not form substantial barriers to dispersal for freshwater fish species, and are more effectively modelled as biogeographic islands than as biogeographic provinces. In combination these results suggest that the Maranhão ichthyofauna was assembled under the influence of several macroevolutionary (extinction, dispersal) and landscape evolution processes, during the Miocene and Pliocene, as well as by the modern ecological characteristics of the region. The results indicate that the distinctive geological and climatic conditions and history of Northeastern Brazil strongly constrained the formation of aquatic faunas in coastal basins of Maranhão State.(AU)

A ictiofauna da Amazônia é uma das mais diversificadas do mundo, mas os peixes das bacias costeiras adjacentes do estado do Maranhão, no Nordeste do Brasil, ainda são pouco conhecidos. Utilizamos métodos filogeográficos, filogenia de comunidade e de diversidade beta filogenética para estudar a história biogeográfica de peixes das bacias costeiras do estado do Maranhão. Nós relatamos um total de 160 espécies de peixes das bacias da região do Maranhão, representando um aumento de 93% sobre os resultados de estudos anteriores. Todas as assembleias de espécies de peixes do Maranhão são polifiléticas, com apenas alguns supostos pares de espécies irmãs habitando a região. As divisões modernas das bacias hidrográficas do Maranhão não formam barreiras substanciais para a dispersão de espécies de peixes de água doce, e são mais efetivamente modeladas como ilhas biogeográficas do que como províncias biogeográficas. Em conjunto, esses resultados sugerem que a ictiofauna maranhense foi montada sob a influência de vários processos de evolução macroevolutiva (extinção, dispersão) e paisagística, durante o Mioceno e Plioceno, bem como pelas características ecológicas modernas da região. Os resultados indicam que as distintas condições geológicas e climáticas e a história do Nordeste do Brasil restringiram fortemente a formação de faunas aquáticas em bacias costeiras do estado do Maranhão.(AU)

Historical biogeography of fishes from coastal basins of Maranhão State, northeastern Brazil

The Amazonian ichthyofauna is one of the most diverse in the world, yet fishes from the adjacent coastal basins of Maranhão State in Northeastern Brazil remain poorly known. We use phylogeographic, community phylogenetic and phylogenetic beta diversity methods to study the biogeographic history of fishes from the coastal basins of Maranhão State. We report a total of 160 fish species from the basins of the Maranhão region, representing a 93% increase over results of previous studies. All the fish species assemblages from Maranhão are polyphyletic, with only a few putative sister species pairs inhabiting the region. The modern watershed divides among Maranhão basins do not form substantial barriers to dispersal for freshwater fish species, and are more effectively modelled as biogeographic islands than as biogeographic provinces. In combination these results suggest that the Maranhão ichthyofauna was assembled under the influence of several macroevolutionary (extinction, dispersal) and landscape evolution processes, during the Miocene and Pliocene, as well as by the modern ecological characteristics of the region. The results indicate that the distinctive geological and climatic conditions and history of Northeastern Brazil strongly constrained the formation of aquatic faunas in coastal basins of Maranhão State.(AU)

A ictiofauna da Amazônia é uma das mais diversificadas do mundo, mas os peixes das bacias costeiras adjacentes do estado do Maranhão, no Nordeste do Brasil, ainda são pouco conhecidos. Utilizamos métodos filogeográficos, filogenia de comunidade e de diversidade beta filogenética para estudar a história biogeográfica de peixes das bacias costeiras do estado do Maranhão. Nós relatamos um total de 160 espécies de peixes das bacias da região do Maranhão, representando um aumento de 93% sobre os resultados de estudos anteriores. Todas as assembleias de espécies de peixes do Maranhão são polifiléticas, com apenas alguns supostos pares de espécies irmãs habitando a região. As divisões modernas das bacias hidrográficas do Maranhão não formam barreiras substanciais para a dispersão de espécies de peixes de água doce, e são mais efetivamente modeladas como ilhas biogeográficas do que como províncias biogeográficas. Em conjunto, esses resultados sugerem que a ictiofauna maranhense foi montada sob a influência de vários processos de evolução macroevolutiva (extinção, dispersão) e paisagística, durante o Mioceno e Plioceno, bem como pelas características ecológicas modernas da região. Os resultados indicam que as distintas condições geológicas e climáticas e a história do Nordeste do Brasil restringiram fortemente a formação de faunas aquáticas em bacias costeiras do estado do Maranhão.(AU)

Hypotheses to explain the origin of species in Amazonia / Hipóteses para explicar a origem das espécies na Amazônia

The main hypotheses proposed to explain barrier formation separating populations and causing the differentiation of species in Amazonia during the course of geological history are based on different factors, as follow: (1) Changes in the distribution of land and sea or in the landscape due to tectonic movements or sea level fluctuations (Paleogeography hypothesis), (2) the barrier effect of Amazonian rivers (River hypothesis), (3) a combination of the barrier effect of broad rivers and vegetational changes in northern and southern Amazonia (River-refuge hypothesis), (4) the isolation of humid rainforest blocks near areas of surface relief in the periphery of Amazonia separated by dry forests, savannas and other intermediate vegetation types during dry climatic periods of the Tertiary and Quaternary (Refuge hypothesis), (5) changes in canopy-density due to climatic reversals (Canopy-density hypothesis) (6) the isolation and speciation of animal populations in small montane habitat pockets around Amazonia due to climatic fluctuations without major vegetational changes (Museum hypothesis), (7) competitive species interactions and local species isolations in peripheral regions of Amazonia due to invasion and counterinvasion during cold/warm periods of the Pleistocene (Disturbance-vicariance hypothesis) and (8) parapatric speciation across steep environmental gradients without separation of the respective populations (Gradient hypothesis). Several of these hypotheses probably are relevant to a different degree for the speciation processes in different faunal groups or during different geological periods. The basic paleogeography model refers mainly to faunal differentiation during the Tertiary and in combination with the Refuge hypothesis. Milankovitch‡ cycles leading to global main hypotheses proposed to explain barrier formation separating populations and causing the differentiation of species in Amazonia during the course of geological...

As principais hipóteses propostas para explicar as formações de barreiras separando populações e causando diferenciações de espécies na Amazônia são baseadas em diferentes fatores (a maioria históricos), como os seguintes: 1) Mudanças na distribuição da terra e mar ou na paisagem devido a movimentos tectônicos ou flutuações do nível do mar (hipótese Paleogeográfica); 2) o efeito de barreiras dos rios amazônicos (hipótese de Rios); 3) uma combinação de efeitos de barreiras de rios largos e mudanças vegetacionais no norte e sul da Amazônia (hipótese de Refúgio-rios), 4) o isolamento dos blocos de floresta úmida das áreas de relevo de superfície na periferia da Amazônia separadas por florestas secas, savanas e outros tipos de vegetação intermediária durante os períodos climáticos secos do Terciário e Quaternário (hipótese de Refúgios), 5) mudanças na densidade do dossel devido a mudanças climáticas (hipótese de Densidade do dossel), 6) o isolamento e especiação de populações animais em pequenas áreas montanhosas na Amazônia devido a flutuações climáticas sem maiores mudanças vegetacionais (hipótese de Museu), 7) interações competitivas entre espécies e isolamentos de espécies locais em regiões periféricas da Amazônia devido a invasão e contra-invasão durante períodos frios/quentes do Pleistoceno (hipótese Distúrbio-vicariante), e 8) especiação parapátrica através de acentuados gradientes ambientais sem separação das respectivas populações (hipótese de Gradiente). Muitas dessas hipóteses provavelmente são relevantes para diferentes graus de processos de especiação em diferentes grupos da fauna ou durante diferentes períodos geológicos. O modelo básico de paleogeografia refere-se principalmente a diferenciação faunística durante o terciário e em combinação com a hipótese de Refúgio. Os ciclos de Milankovitch que levam a mudanças climáticas-vegetacionais globais afetaram os biomas do mundo não apenas durante o Pleistoceno mas também durante...

Hypotheses to explain the origin of species in Amazonia

The main hypotheses proposed to explain barrier formation separating populations and causing the differentiation of species in Amazonia during the course of geological history are based on different factors, as follow: (1) Changes in the distribution of land and sea or in the landscape due to tectonic movements or sea level fluctuations (Paleogeography hypothesis), (2) the barrier effect of Amazonian rivers (River hypothesis), (3) a combination of the barrier effect of broad rivers and vegetational changes in northern and southern Amazonia (River-refuge hypothesis), (4) the isolation of humid rainforest blocks near areas of surface relief in the periphery of Amazonia separated by dry forests, savannas and other intermediate vegetation types during dry climatic periods of the Tertiary and Quaternary (Refuge hypothesis), (5) changes in canopy-density due to climatic reversals (Canopy-density hypothesis) (6) the isolation and speciation of animal populations in small montane habitat pockets around Amazonia due to climatic fluctuations without major vegetational changes (Museum hypothesis), (7) competitive species interactions and local species isolations in peripheral regions of Amazonia due to invasion and counterinvasion during cold/warm periods of the Pleistocene (Disturbance-vicariance hypothesis) and (8) parapatric speciation across steep environmental gradients without separation of the respective populations (Gradient hypothesis). Several of these hypotheses probably are relevant to a different degree for the speciation processes in different faunal groups or during different geological periods. The basic paleogeography model refers mainly to faunal differentiation during the Tertiary and in combination with the Refuge hypothesis. Milankovitch‡ cycles leading to global main hypotheses proposed to explain barrier formation separating populations and causing the differentiation of species in Amazonia during the course of geological history are based on different factors, as follow: (1) Changes in the distribution of land and sea or in the landscape due to tectonic movements or sea level fluctuations (Paleogeography hypothesis), (2) the barrier effect of Amazonian rivers (River hypothesis), (3) a combination of the barrier effect of broad rivers and vegetational changes in northern and southern Amazonia (River-refuge hypothesis), (4) the isolation of humid rainforest blocks near areas of surface relief in the periphery of Amazonia separated by dry forests, savannas and other intermediate vegetation types during dry climatic periods of the Tertiary and Quaternary (Refuge hypothesis), (5) changes in canopy-density due to climatic reversals (Canopy-density hypothesis) (6) the isolation and speciation of animal populations in small montane habitat pockets around Amazonia due to climatic fluctuations without major vegetational changes (Museum hypothesis), (7) competitive species interactions and local species isolations in peripheral regions of Amazonia due to invasion and counterinvasion during cold/warm periods of the Pleistocene (Disturbance-vicariance hypothesis) and (8) parapatric speciation across steep environmental gradients without separation of the respective populations (Gradient hypothesis). Several of these hypotheses probably are relevant to a different degree for the speciation processes in different faunal groups or during different geological periods. The basic paleogeography model refers mainly to faunal differentiation during the Tertiary and in combination with the Refuge hypothesis. Milankovitch cycles leading to global climatic-vegetational changes affected the biomes of the world not only during the Pleistocene but also during the Tertiary and earlier geological periods. New geoscientific evidence for the effect of dry climatic periods in Amazonia supports the predictions of the Refuge hypothesis. The disturbance-vicariance hypothesis refers to the presumed effect of cold/warm climatic phases of the Pleistocene only and is of limited general relevance because most extant species originated earlier and probably through paleogeographic changes and the formation of ecological refuges during the Tertiary.

As principais hipóteses propostas para explicar as formações de barreiras separando populações e causando diferenciações de espécies na Amazônia são baseadas em diferentes fatores (a maioria históricos), como os seguintes: 1) Mudanças na distribuição da terra e mar ou na paisagem devido a movimentos tectônicos ou flutuações do nível do mar (hipótese Paleogeográfica); 2) o efeito de barreiras dos rios amazônicos (hipótese de Rios); 3) uma combinação de efeitos de barreiras de rios largos e mudanças vegetacionais no norte e sul da Amazônia (hipótese de Refúgio-rios), 4) o isolamento dos blocos de floresta úmida das áreas de relevo de superfície na periferia da Amazônia separadas por florestas secas, savanas e outros tipos de vegetação intermediária durante os períodos climáticos secos do Terciário e Quaternário (hipótese de Refúgios), 5) mudanças na densidade do dossel devido a mudanças climáticas (hipótese de Densidade do dossel), 6) o isolamento e especiação de populações animais em pequenas áreas montanhosas na Amazônia devido a flutuações climáticas sem maiores mudanças vegetacionais (hipótese de Museu), 7) interações competitivas entre espécies e isolamentos de espécies locais em regiões periféricas da Amazônia devido a invasão e contra-invasão durante períodos frios/quentes do Pleistoceno (hipótese Distúrbio-vicariante), e 8) especiação parapátrica através de acentuados gradientes ambientais sem separação das respectivas populações (hipótese de Gradiente). Muitas dessas hipóteses provavelmente são relevantes para diferentes graus de processos de especiação em diferentes grupos da fauna ou durante diferentes períodos geológicos. O modelo básico de paleogeografia refere-se principalmente a diferenciação faunística durante o terciário e em combinação com a hipótese de Refúgio. Os ciclos de Milankovitch que levam a mudanças climáticas-vegetacionais globais afetaram os biomas do mundo não apenas durante o Pleistoceno mas também durante o Terciário e períodos geológicos anteriores. Novas evidências geocientíficas para o efeito dos períodos climáticos secos na Amazônia suportam as predições da hipótese de Refúgios. A hipótese de distúrbio-vicariância refere-se aos presumidos efeitos das fases climáticas frio/quente ocorridos somente no pleistoceno e é de relevância geral limitada, pois a maioria das espécies se originam antes, provavelmente através de trocas paleogeográficas e a formação de refúgios ecológicos durante o Terciário.

Hypotheses to explain the origin of species in Amazonia

The main hypotheses proposed to explain barrier formation separating populations and causing the differentiation of species in Amazonia during the course of geological history are based on different factors, as follow: (1) Changes in the distribution of land and sea or in the landscape due to tectonic movements or sea level fluctuations (Paleogeography hypothesis), (2) the barrier effect of Amazonian rivers (River hypothesis), (3) a combination of the barrier effect of broad rivers and vegetational changes in northern and southern Amazonia (River-refuge hypothesis), (4) the isolation of humid rainforest blocks near areas of surface relief in the periphery of Amazonia separated by dry forests, savannas and other intermediate vegetation types during dry climatic periods of the Tertiary and Quaternary (Refuge hypothesis), (5) changes in canopy-density due to climatic reversals (Canopy-density hypothesis) (6) the isolation and speciation of animal populations in small montane habitat pockets around Amazonia due to climatic fluctuations without major vegetational changes (Museum hypothesis), (7) competitive species interactions and local species isolations in peripheral regions of Amazonia due to invasion and counterinvasion during cold/warm periods of the Pleistocene (Disturbance-vicariance hypothesis) and (8) parapatric speciation across steep environmental gradients without separation of the respective populations (Gradient hypothesis). Several of these hypotheses probably are relevant to a different degree for the speciation processes in different faunal groups or during different geological periods. The basic paleogeography model refers mainly to faunal differentiation during the Tertiary and in combination with the Refuge hypothesis. Milankovitch‡ cycles leading to global main hypotheses proposed to explain barrier formation separating populations and causing the differentiation of species in Amazonia during the course of geological history are based on different factors, as follow: (1) Changes in the distribution of land and sea or in the landscape due to tectonic movements or sea level fluctuations (Paleogeography hypothesis), (2) the barrier effect of Amazonian rivers (River hypothesis), (3) a combination of the barrier effect of broad rivers and vegetational changes in northern and southern Amazonia (River-refuge hypothesis), (4) the isolation of humid rainforest blocks near areas of surface relief in the periphery of Amazonia separated by dry forests, savannas and other intermediate vegetation types during dry climatic periods of the Tertiary and Quaternary (Refuge hypothesis), (5) changes in canopy-density due to climatic reversals (Canopy-density hypothesis) (6) the isolation and speciation of animal populations in small montane habitat pockets around Amazonia due to climatic fluctuations without major vegetational changes (Museum hypothesis), (7) competitive species interactions and local species isolations in peripheral regions of Amazonia due to invasion and counterinvasion during cold/warm periods of the Pleistocene (Disturbance-vicariance hypothesis) and (8) parapatric speciation across steep environmental gradients without separation of the respective populations (Gradient hypothesis). Several of these hypotheses probably are relevant to a different degree for the speciation processes in different faunal groups or during different geological periods. The basic paleogeography model refers mainly to faunal differentiation during the Tertiary and in combination with the Refuge hypothesis. Milankovitch cycles leading to global climatic-vegetational changes affected the biomes of the world not only during the Pleistocene but also during the Tertiary and earlier geological periods. New geoscientific evidence for the effect of dry climatic periods in Amazonia supports the predictions of the Refuge hypothesis. The disturbance-vicariance hypothesis refers to the presumed effect of cold/warm climatic phases of the Pleistocene only and is of limited general relevance because most extant species originated earlier and probably through paleogeographic changes and the formation of ecological refuges during the Tertiary.

As principais hipóteses propostas para explicar as formações de barreiras separando populações e causando diferenciações de espécies na Amazônia são baseadas em diferentes fatores (a maioria históricos), como os seguintes: 1) Mudanças na distribuição da terra e mar ou na paisagem devido a movimentos tectônicos ou flutuações do nível do mar (hipótese Paleogeográfica); 2) o efeito de barreiras dos rios amazônicos (hipótese de Rios); 3) uma combinação de efeitos de barreiras de rios largos e mudanças vegetacionais no norte e sul da Amazônia (hipótese de Refúgio-rios), 4) o isolamento dos blocos de floresta úmida das áreas de relevo de superfície na periferia da Amazônia separadas por florestas secas, savanas e outros tipos de vegetação intermediária durante os períodos climáticos secos do Terciário e Quaternário (hipótese de Refúgios), 5) mudanças na densidade do dossel devido a mudanças climáticas (hipótese de Densidade do dossel), 6) o isolamento e especiação de populações animais em pequenas áreas montanhosas na Amazônia devido a flutuações climáticas sem maiores mudanças vegetacionais (hipótese de Museu), 7) interações competitivas entre espécies e isolamentos de espécies locais em regiões periféricas da Amazônia devido a invasão e contra-invasão durante períodos frios/quentes do Pleistoceno (hipótese Distúrbio-vicariante), e 8) especiação parapátrica através de acentuados gradientes ambientais sem separação das respectivas populações (hipótese de Gradiente). Muitas dessas hipóteses provavelmente são relevantes para diferentes graus de processos de especiação em diferentes grupos da fauna ou durante diferentes períodos geológicos. O modelo básico de paleogeografia refere-se principalmente a diferenciação faunística durante o terciário e em combinação com a hipótese de Refúgio. Os ciclos de Milankovitch que levam a mudanças climáticas-vegetacionais globais afetaram os biomas do mundo não apenas durante o Pleistoceno mas também durante o Terciário e períodos geológicos anteriores. Novas evidências geocientíficas para o efeito dos períodos climáticos secos na Amazônia suportam as predições da hipótese de Refúgios. A hipótese de distúrbio-vicariância refere-se aos presumidos efeitos das fases climáticas frio/quente ocorridos somente no pleistoceno e é de relevância geral limitada, pois a maioria das espécies se originam antes, provavelmente através de trocas paleogeográficas e a formação de refúgios ecológicos durante o Terciário.