RESUMO
South America is home to the highest freshwater fish biodiversity on Earth, and the hotspot of species richness is located in the western Amazon basin. The location of this hotspot is enigmatic, as it is inconsistent with the pattern observed in river systems across the world of increasing species richness towards a river's mouth. Here we investigate the role of river capture events caused by Andean mountain building and repeated episodes of flooding in western Amazonia in shaping the modern-day richness pattern of freshwater fishes in South America, and in Amazonia in particular. To this end, we combine a reconstruction of river networks since 80 Ma with a mechanistic model simulating dispersal, allopatric speciation and extinction over the dynamic landscape of rivers and lakes. We show that Andean mountain building and consequent numerous small river capture events in western Amazonia caused freshwater habitats to be highly dynamic, leading to high diversification rates and exceptional richness. The history of marine incursions and lakes, including the Miocene Pebas mega-wetland system in western Amazonia, played a secondary role.
Assuntos
Biodiversidade , Ecossistema , Animais , América do Sul , Lagos , PeixesRESUMO
Species establish different interactions (e.g. antagonistic, mutualistic) with multiple species, forming multilayer ecological networks. Disentangling network co-structure in multilayer networks is crucial to predict how biodiversity loss may affect the persistence of multispecies assemblages. Existing methods to analyse multilayer networks often fail to consider network co-structure. We present a new method to evaluate the modular co-structure of multilayer networks through the assessment of species degree co-distribution and network module composition. We focus on modular structure because of its high prevalence among ecological networks. We apply our method to two Lepidoptera-plant networks, one describing caterpillar-plant herbivory interactions and one representing adult Lepidoptera nectaring on flowers, thereby possibly pollinating them. More than 50% of the species established either herbivory or visitation interactions, but not both. These species were over-represented among plants and lepidopterans, and were present in most modules in both networks. Similarity in module composition between networks was high but not different from random expectations. Our method clearly delineates the importance of interpreting multilayer module composition similarity in the light of the constraints imposed by network structure to predict the potential indirect effects of species loss through interconnected modular networks.
Assuntos
Cadeia Alimentar , Lepidópteros/fisiologia , Modelos Biológicos , Fenômenos Fisiológicos Vegetais , Animais , Biodiversidade , Flores , Herbivoria/fisiologia , Plantas , Simbiose/fisiologiaRESUMO
A challenge for conservation management is to understand how population and habitat dynamics interact to affect species persistence. In real landscapes, timing and duration of disturbances can vary, and species' responses to habitat changes will depend on how timing of dispersal and reproduction events relate to the landscape temporal structure. For instance, increasing disturbance frequency may promote extinction of species that are unable to appropriately time their reproduction in an ever-changing habitat and favor species that are able to track habitat changes. We developed a mathematical model to compare the effects of pulsed dispersal, initiated by shifts in habitat quality, with temporally continuous dispersal. We tested the effects of habitat (and population) turnover rates on metapopulation establishment, persistence, and long-term patch occupancy. Pulsed dispersal reduced patch occupancy and metapopulation longevity when habitat patches are relatively permanent. In such cases, demographic extinction was the primary form of local extinction. Conversely, when habitat patches are short-lived and new ones are frequently formed, pulsed dispersal promoted rapid colonization, increased occupancy, and prolonged metapopulation persistence. Our results show that species responsiveness to habitat disturbance is critical to metapopulation persistence, having profound implications for the species likely to persist in landscapes with altered disturbance regimes.