Molecular Systematics and Biogeography of the Southern South American Freshwater “Crabs” Aegla (Decapoda: Anomura: Aeglidae) Using Multiple Heuristic Tree Search Approaches

Abstract

Recently new heuristic genetic algorithms such as Treefinder and MetaGA have been developed to search for optimal trees in a maximum likelihood (ML) framework. In this study we combined these methods with other standard heuristic approaches such as ML and maximum parsimony hill-climbing searches and Bayesian inference coupled with Markov chain Monte Carlo techniques under homogeneous and mixed models of evolution to conduct an extensive phylogenetic analysis of the most abundant and widely distributed southern South American freshwater"crab,"the Aegla(Anomura: Aeglidae). A total of 167 samples representing 64 Aegla species and subspecies were sequenced for one nuclear (28S rDNA) and four mitochondrial (12S and 16S rDNA, COI, and COII) genes (5352 bp total). Additionally, six other anomuran species from the genera Munida,Pachycheles, and Uroptychus(Galatheoidea), Lithodes(Paguroidea), and Lomis(Lomisoidea) and the nuclear 18S rDNA gene (1964 bp) were included in preliminary analyses for rooting the Aegla tree. Nonsignificantly different phylogenetic hypotheses resulted from all the different heuristic methods used here, although the best scored topologies found under the ML hill-climbing, Bayesian, and MetaGA approaches showed considerably better likelihood scores (Delta> 54) than those found under the MP and Treefinder approaches. Our trees provided strong support for most of the recognized Aegla species except for A. cholchol,A. jarai,A. parana,A. marginata, A. platensis, and A. franciscana, which may actually represent multiple species. Geographically, the Aegla group was divided into a basal western clade (21 species and subspecies) composed of two subclades with overlapping distributions, and a more recent central-eastern clade (43 species) composed of three subclades with fairly well-recognized distributions. This result supports the Pacific-Origin Hypothesis postulated for the group; alternative hypotheses of Atlantic or multiple origins were significantly rejected by our analyses. Finally, we combined our phylogenetic results with previous hypotheses of South American paleodrainages since the Jurassic to propose a biogeographical framework of the Aegla radiation.

New species and records of the genus Aegla Leach, 1820 (Crustacea, Anomura, Aeglidae) from the West-Central region of Rio Grande do Sul, Brazil

“…Neither morphological features nor molecular phylogenetic analyses suggest the existence of hybrids between A. platensis and A. grisella. In the latter, samples of A. grisella from two different localities were used and they appear as paraphyletic, as already indicated by Pérez-Losada et al (2004). Further studies are needed to elucidate the taxonomic status of this species.…”

“…Branch support was assessed via the rapid bootstrap algorithm (100 replicates) (Stamakis et al, 2008;Pattengale et al, 2010). Aegla papudo Schmitt, 1942 was used as outgroup, since this species was found to be the most primitive Aeglidae, based on morphology (Jara, 1992) and molecular characters (Pérez-Losada et al, 2002;Pérez-Losada et al, 2004).…”

Revisão taxonômica e análise cladística de Aegla Leach, 1820 (Crustacea, Anomura, Aeglidae) com ocorrência nas bacias hidrográficas do Alto Paraná e do Alto Uruguai

“…Após a publicação dos capítulos 1 e 2 desta tese o número de espécies e subespécies de Aegla Leach, 1820 passará de 78 para 84 no total; no Brasil, de 47 para 53; e, no estado de São Paulo, de 9 para 15 espécies, um incremento de 60% neste último caso; 2. O clado C sensu Pérez-Losada et al (2004) 7. Revisões taxonômicas precisam ser realizadas para diversas espécies de eglídeos, como, por exemplo: Aegla castro, A. jarai, A. parana e A. parva para que seja possível compreender de forma mais precisa as relações filogenéticas entre as populações e, ainda, para que se possa produzir uma nova chave de identificação, robusta e completa, para este grupo de crustáceos tão singular.…”

“…Além disso, Schuldt et al (1988) foram os pioneiros na utilização da análise cladística para resolver problemas internos da família Aeglidae, uma vez que, em seu trabalho, os autores propuseram as relações de parentesco em um cladograma para sete espécies de Aegla com ocorrência no Chile. No mais recente estudo com descrições de espécies, Santos et al (2015) apresentam um cladograma de máxima verossimilhança baseado em caracteres moleculares com 18 espécies, correspondentes ao clado C sensu Pérez-Losada et al (2004), mostrando esse clado como monofilético novamente. No entanto, problemas filogenéticos e taxonômicos, que podem ser detectados desde o estudo de Pérez-Losada et al (2004) até Santos et.…”

“…No mais recente estudo com descrições de espécies, Santos et al (2015) apresentam um cladograma de máxima verossimilhança baseado em caracteres moleculares com 18 espécies, correspondentes ao clado C sensu Pérez-Losada et al (2004), mostrando esse clado como monofilético novamente. No entanto, problemas filogenéticos e taxonômicos, que podem ser detectados desde o estudo de Pérez-Losada et al (2004) até Santos et. al.…”