33 research outputs found
Vicariance and dispersal in southern hemisphere freshwater fish clades: a palaeontological perspective
Widespread fish clades that occur mainly or exclusively in fresh water represent a key target of biogeographical investigation due to limited potential for crossing marine barriers. Timescales for the origin and diversification of these groups are crucial tests of vicariant scenarios in which continental breakâups shaped modern geographic distributions. Evolutionary chronologies are commonly estimated through nodeâbased palaeontological calibration of molecular phylogenies, but this approach ignores most of the temporal information encoded in the known fossil record of a given taxon. Here, we review the fossil record of freshwater fish clades with a distribution encompassing disjunct landmasses in the southern hemisphere. Palaeontologically derived temporal and geographic data were used to infer the plausible biogeographic processes that shaped the distribution of these clades. For seven extant clades with a relatively wellâknown fossil record, we used the stratigraphic distribution of their fossils to estimate confidence intervals on their times of origin. To do this, we employed a Bayesian framework that considers nonâuniform preservation potential of freshwater fish fossils through time, as well as uncertainty in the absolute age of fossil horizons. We provide the following estimates for the origin times of these clades: Lepidosireniformes [125â95Â million years ago (Ma)]; totalâgroup Osteoglossomorpha (207â167Â Ma); Characiformes (120â95Â Ma; a younger estimate of 97â75Â Ma when controversial Cenomanian fossils are excluded); Galaxiidae (235â21Â Ma); Cyprinodontiformes (80â67Â Ma); Channidae (79â43Â Ma); Percichthyidae (127â69Â Ma). These dates are mostly congruent with published molecular timetree estimates, despite the use of semiâindependent data. Our reassessment of the biogeographic history of southern hemisphere freshwater fishes shows that longâdistance dispersals and regional extinctions can confound and erode preâexisting vicarianceâdriven patterns. It is probable that disjunct distributions in many extant groups result from complex biogeographic processes that took place during the Late Cretaceous and Cenozoic. Although longâdistance dispersals likely shaped the distributions of several freshwater fish clades, their exact mechanisms and their impact on broader macroevolutionary and ecological dynamics are still unclear and require further investigation.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/148368/1/brv12473_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148368/2/brv12473.pd
Alien Registration- Brikiatis, Demeetrula (Saco, York County)
https://digitalmaine.com/alien_docs/4097/thumbnail.jp
Alien Registration- Brikiatis, Vasilios P. (Saco, York County)
https://digitalmaine.com/alien_docs/4099/thumbnail.jp
Alien Registration- Brikiatis, Evanthia (Saco, York County)
https://digitalmaine.com/alien_docs/4098/thumbnail.jp
Alien Registration- Brikiatis, Demeetrula (Saco, York County)
https://digitalmaine.com/alien_docs/4097/thumbnail.jp
Alien Registration- Brikiatis, Vasilios P. (Saco, York County)
https://digitalmaine.com/alien_docs/4099/thumbnail.jp
Alien Registration- Brikiatis, Evanthia (Saco, York County)
https://digitalmaine.com/alien_docs/4098/thumbnail.jp