SignificanceThe formation of the Isthmus of Panama, which linked North and South America, is key to understanding the biodiversity, oceanography, atmosphere, and climate in the region. Despite its importance across multiple disciplines, the timing of formation and emergence of the Isthmus and the biological patterns it created have been controversial. Here, we analyze molecular and fossil data, including terrestrial and marine organisms, to show that biotic migrations across the Isthmus of Panama began several million years earlier than commonly assumed. An earlier evolution of the Isthmus has broad implications for the mechanisms driving global climate (e.g., Pleistocene glaciations, thermohaline circulation) as well as the rich biodiversity of the Americas.

Introduction 234Overview of Acipenseriformes 234International harvest and trade 240Major global fisheries 241 Caspian Sea 241 Black Sea and Sea of Azov 245 Abstract The 27 extant species of sturgeons and paddlefishes (Order Acipenseriformes) represent a unique and relict lineage of fishes. Producers of coveted black caviar, sturgeons are one of the most valuable wildlife commodities on earth. The group is among the most endangered fishes with all species listed under Convention on International Trade in Endangered Species (CITES) Appendix I (two species) or II (25 species), only two species considered Lower Risk by IUCN, four of the nine US taxa and one Caspian species protected under the Endangered Species Act, and local extinctions recorded for 19 of 27 species. Despite their well-publicized imperilled status, commercial pressure on 15 species persists.Here, after reviewing the biological characteristics of sturgeons and paddlefishes and their commercial use, an overview of global fisheries is presented. The synopsis demonstrates that, with few exceptions, sturgeon and paddlefish are imperilled across the globe and long-term survival in the wild is in jeopardy. All major sturgeon fisheries have surpassed peak productivity levels, with 70% of major fisheries posting recent harvests <15% of historic peak catches and 35% of the fisheries examined crashing within 7-20 years of inception. Even in Caspian Sea fisheries, the most important globally, present catches are below 10% of historic peak landings. Improved domestic and international fisheries management and attention to habitat and species restoration is now needed. Although captive rearing offers promise for caviar alternatives and endangered species restoration, it must advance cautiously to avoid environmental harm. To ensure a continued supply of caviar and the survival of these unique fishes we offer recommendations for priority conservation action for the future.

Although attempts to understand Central American freshwater fish provincialism date to the 1960s, early efforts lacked the wealth of distributional data now available. Biogeographic work on Central American freshwater fishes has been largely descriptive and regional, and lacked a broader synthesis. Here we use parsimony analysis of endemicity (PAE) to elucidate faunistic relationships between major drainages and to delineate areas of endemism. We then perform a Brooks parsimony analysis (BPA) on the resulting areas. The PAE recovered a primary division between four Pacific and six Atlantic slope areas of endemism. In contrast, the BPA recovered two Central American geographic clades, one sharing a history with North America and the other with South America. Fish diversity is uneven across Central America, with greater diversity in areas adjacent to the more species‐rich regions of North and South America. In northern and nuclear Central America, the paucity of ostariophysan freshwater fishes such as catfishes and characins (groups that dominate adjacent regions) contrasts with high species richness of poeciliids and cichlids. Results of this study are consistent with Myer's hypothesis that poeciliids and cichlids dispersed to Northern or Nuclear Middle America early in the Cenozoic, long before the Plio‐Pleistocene rise of the Isthmus of Panama.

LETTERSUndercover. Many Alpheidae shrimps live deep in the reef and are impossible to collect nonlethally. Published by AAAS

The contrasting distribution of species diversity across the major lineages of cichlids makes them an ideal group for investigating macroevolutionary processes. In this study, we investigate whether different rates of diversification may explain the disparity in species richness across cichlid lineages globally. We present the most taxonomically robust time-calibrated hypothesis of cichlid evolutionary relationships to date. We then utilize this temporal framework to investigate whether both species-rich and depauperate lineages are associated with rapid shifts in diversification rates and if exceptional species richness can be explained by clade age alone. A single significant rapid rate shift increase is detected within the evolutionary history of the African subfamily Pseudocrenilabrinae, which includes the haplochromins of the East African Great Lakes. Several lineages from the subfamilies Pseudocrenilabrinae (Australotilapiini, Oreochromini) and Cichlinae (Heroini) exhibit exceptional species richness given their clade age, a net rate of diversification, and relative rates of extinction, indicating that clade age alone is not a sufficient explanation for their increased diversity. Our results indicate that the Neotropical Cichlinae includes lineages that have not experienced a significant rapid burst in diversification when compared to certain African lineages (rift lake). Neotropical cichlids have remained comparatively understudied with regard to macroevolutionary patterns relative to African lineages, and our results indicate that of Neotropical lineages, the tribe Heroini may have an elevated rate of diversification in contrast to other Neotropical cichlids. These findings provide insight into our understanding of the diversification patterns across taxonomically disparate lineages in this diverse clade of freshwater fishes and one of the most species-rich families of vertebrates.

Despite recent progress on the higher-level relationships of Cichlidae and its Indian, Malagasy, and Greater Antillean

Ostariophysi is a superorder of bony fishes including more than 10,300 species in 1100 genera and 70 families. This superorder is traditionally divided into five major groups (orders): Gonorynchiformes (milkfishes and sandfishes), Cypriniformes (carps and minnows), Characiformes (tetras and their allies), Siluriformes (catfishes), and Gymnotiformes (electric knifefishes). Unambiguous resolution of the relationships among these lineages remains elusive, with previous molecular and morphological analyses failing to produce a consensus phylogeny. In this study, we use over 350 ultraconserved element (UCEs) loci comprising 5 million base pairs collected across 35 representative ostariophysan species to compile one of the most data-rich phylogenies of fishes to date. We use these data to infer higher level (interordinal) relationships among ostariophysan fishes, focusing on the monophyly of the Characiformes-one of the most contentiously debated groups in fish systematics. As with most previous molecular studies, we recover a non-monophyletic Characiformes with the two monophyletic suborders, Citharinoidei and Characoidei, more closely related to other ostariophysan clades than to each other. We also explore incongruence between results from different UCE data sets, issues of orthology, and the use of morphological characters in combination with our molecular data. [Conserved sequence; ichthyology; massively parallel sequencing; morphology; next-generation sequencing; UCEs.].

A molecular phylogenetic analysis recovers a pattern consistent with a drift vicariance scenario for the origin of Greater Antillean cichlids. This phylogeny, based on mitochondrial and nuclear genes, reveals that clades on different geographic regions diverged concurrently with the geological separation of these areas. Middle America was initially colonized by South American cichlids in the Cretaceous, most probably through the Cretaceous Island Arc. The separation of Greater Antillean cichlids and their mainland Middle American relatives was caused by a drift vicariance event that took place when the islands became separated from Yucatan in the Eocene. Greater Antillean cichlids are monophyletic and do not have close South American relatives. Therefore, the alternative hypothesis that these cichlids migrated via an Oligocene landbridge from South America is falsified. A marine dispersal hypothesis is not employed because the drift vicariance hypothesis is better able to explain the biogeographic patterns, both temporal and phylogenetic.