Disentangling historical relationships within Poeciliidae (Teleostei: Cyprinodontiformes) using ultraconserved elements.

Poeciliids (Cyprinodontiformes: Poeciliidae), commonly known as livebearers, are popular fishes in the aquarium trade (e.g., guppies, mollies, swordtails) that are widely distributed in the Americas, with 274 valid species in 27 genera. This group has undergone various taxonomic changes recently, spurred by investigations using traditional genetic markers. Here we used over 1,000 ultraconserved loci to infer the relationships within Poeciliidae in the first attempt at understanding their diversification based on genome-scale data. We explore gene tree discordance and investigate potential incongruence between concatenation and coalescent inference methods. Our aim is to examine the influence of incomplete lineage sorting and reticulate evolution on the poeciliids' evolutionary history and how these factors contribute to the observed gene tree discordace. Our concatenated and coalescent phylogenomic inferences recovered four major clades within Poeciliidae. Most supra-generic level relationships we inferred were congruent with previous molecular studies, but we found some disagreements; the Middle American taxa Phallichthys and Poecilia (Mollienesia) were recovered as non-monophyletic, and unlike other recent molecular studies, we recovered Brachyrhaphis as monophyletic. Our study is the first to provide signatures of reticulate evolution in Poeciliidae at the family level; however, continued finer-scale investigations are needed to understand the complex evolutionary history of the family along with a much-needed taxonomic re-evaluation.

Beyond Pairwise Interactions: Multispecies Character Displacement in Mexican Freshwater Fish Communities.

Competition has long been recognized as a central force in shaping evolution, particularly through character displacement. Yet research on character displacement is biased, as it has focused almost exclusively on pairs of interacting species while ignoring multispecies interactions. Communities are seldom so simple that only pairs of species interact, and it is not clear whether inferences from pairwise interactions are sufficient to explain patterns of phenotypes in nature. Here, we test for character displacement in a natural system of freshwater fishes in western Mexico that contains up to four congeneric species of the genus Poeciliopsis. We analyzed body shape differences between populations with different numbers of competitors while accounting for confounding environmental variables. Surprisingly, we found evidence for convergent character displacement in populations of P. prolifica, P. viriosa, and P. latidens. We also found that the convergence in body shape was not consistently in the same direction, meaning that when three or more competitors co-occurred, we did not find more extreme body shapes compared with when there were only two competitors. Instead, when three or more competitors co-occurred, body shape was intermediate between the shape found with a pair of species and the shape found with no competitor present. This intermediate shape suggests that evolution in multispecies communities likely occurs in response to several competitors rather than to simple pairwise interactions. Overall, our results suggest that competition among multiple species is more complex than simple pairwise competitive interactions.

Colorful invasion in permissive Neotropical ecosystems: establishment of ornamental non-native poeciliids of the genera Poecilia/Xiphophorus (Cyprinodontiformes: Poeciliidae) and management alternatives

Headwater creeks are environments susceptible to invasion by non-native fishes. We evaluated the reproduction of 22 populations of the non-native livebearers guppy Poecilia reticulata, black molly Poecilia sphenops, Yucatan molly Poecilia velifera, green swordtail Xiphophorus hellerii, southern platyfish Xiphophorus maculatus, and variable platyfish Xiphophorus variatus during an annual cycle in five headwater creeks located in the largest South American ornamental aquaculture center, Paraíba do Sul River basin, southeastern Brazil. With few exceptions, females of most species were found reproducing (stages 2, 3, 4) all year round in the creeks and gravid females of all species showed small sizes indicating stunting. Juveniles were frequent in all sites. The fecundity of the six poeciliids was always low in all periods. The sex ratio was biased for females in most species, both bimonthly as for the whole period. Water temperature, water level and rainfall were not significantly correlated with reproduction in any species. Therefore, most populations appeared well established. The pertinence of different management actions, such as devices to prevent fish escape, eradication with rotenone and research about negative effects on native species, is discussed in the light of current aquaculture practices in the region.(AU)

Riachos de cabeceira são ambientes susceptíveis à invasão por peixes não-nativos. Neste trabalho, avaliou-se a reprodução de 22 populações dos poecilídeos não-nativos guppy Poecilia reticulata, molinésia preta Poecilia sphenops, molinésia Poecilia velifera, espadinha Xiphophorus hellerii, plati Xiphophorus maculatus e plati variado Xiphophorus variatus durante diferentes anos em cinco riachos de cabeceira localizados no maior polo de piscicultura ornamental da América do Sul, bacia do rio Paraíba do Sul, sudeste do Brasil. Foram encontradas fêmeas da maioria das espécies em reprodução (estágios 2, 3, 4), durante todos os anos nos riachos e fêmeas grávidas de todas as espécies apresentaram pequeno tamanho indicando nanismo. Juvenis de todas as espécies foram frequentes em todos os locais. A fecundidade das seis espécies sempre foi baixa em todos os períodos. Para os períodos bimestrais e totais, encontrou-se mais fêmeas que machos na maioria das espécies. Temperatura e nível de água dos riachos, bem como precipitação pluviométrica não foram correlacionadas com a reprodução. Todas as populações estão estabelecidas nos locais e ações de gerenciamento como dispositivos para impedir a fuga de peixes, erradicação com rotenona e pesquisa científica sobre os efeitos negativos nas espécies nativas são discutidas em relação às práticas de piscicultura na região.(AU)