Phylogenetic position of the acariform mites: sensitivity to homology assessment under total evidence

Autor(es)

Pepato, Almir R. ^[1] ; da Rocha, Carlos E. F. ^[1] ; Dunlop, Jason A. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Dept Zool, Inst Biociencias, BR-05508900 Sao Paulo - Brazil

^[2] Humboldt Univ, Museum Nat Kunde, Leibniz Inst Res Evolut & Biodivers, D-10115 Berlin - Germany

• Tipo de documento: Artigo Científico
• Fonte: BMC Evolutionary Biology; v. 10, AUG 2 2010.
• Citações Web of Science: 73

Resumo

Background: Mites (Acari) have traditionally been treated as monophyletic, albeit composed of two major lineages: Acariformes and Parasitiformes. Yet recent studies based on morphology, molecular data, or combinations thereof, have increasingly drawn their monophyly into question. Furthermore, the usually basal (molecular) position of one or both mite lineages among the chelicerates is in conflict to their morphology, and to the widely accepted view that mites are close relatives of Ricinulei. Results: The phylogenetic position of the acariform mites is examined through employing SSU, partial LSU sequences, and morphology from 91 chelicerate extant terminals (forty Acariformes). In a static homology framework, molecular sequences were aligned using their secondary structure as guide, whereby regions of ambiguous alignment were discarded, and pre-aligned sequences analyzed under parsimony and different mixed models in a Bayesian inference. Parsimony and Bayesian analyses led to trees largely congruent concerning infraordinal, well-supported branches, but with low support for inter-ordinal relationships. An exception is Solifugae + Acariformes (P. P = 100%, J. = 0.91). In a dynamic homology framework, two analyses were run: a standard POY analysis and an analysis constrained by secondary structure. Both analyses led to largely congruent trees; supporting a (Palpigradi (Solifugae Acariformes)) clade and Ricinulei as sister group of Tetrapulmonata with the topology (Ricinulei (Amblypygi (Uropygi Araneae))). Combined analysis with two different morphological data matrices were run in order to evaluate the impact of constraining the analysis on the recovered topology when employing secondary structure as a guide for homology establishment. The constrained combined analysis yielded two topologies similar to the exclusively molecular analysis for both morphological matrices, except for the recovery of Pedipalpi instead of the (Uropygi Araneae) clade. The standard (direct optimization) POY analysis, however, led to the recovery of trees differing in the absence of the otherwise well-supported group Solifugae + Acariformes. Conclusions: Previous studies combining ribosomal sequences and morphology often recovered topologies similar to purely morphological analyses of Chelicerata. The apparent stability of certain clades not recovered here, like Haplocnemata and Acari, is regarded as a byproduct of the way the molecular homology was previously established using the instrumentalist approach implemented in POY. Constraining the analysis by a priori homology assessment is defended here as a way of maintaining the severity of the test when adding new data to the analysis. Although the strength of the method advocated here is keeping phylogenetic information from regions usually discarded in an exclusively static homology framework; it still has the inconvenience of being uninformative on the effect of alignment ambiguity on resampling methods of clade support estimation. Finally, putative morphological apomorphies of Solifugae + Acariformes are the reduction of the proximal cheliceral podomere, medial abutting of the leg coxae, loss of sperm nuclear membrane, and presence of differentiated germinative and secretory regions in the testis delivering their products into a common lumen. (AU)

• Processo FAPESP: 05/03458-1 - Filogenia de Halacaridae (Acari: Prostigmata), referida a partir de evidências moleculares e da ultraestrutura dos espermatozóides
• Beneficiário: Almir Rogério Pepato
• Modalidade de apoio: Bolsas no Brasil - Doutorado
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• Beneficiário: Miguel Trefaut Urbano Rodrigues
• Modalidade de apoio: Auxílio à Pesquisa - Temático
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• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 04/09961-4 - Biodiversidade, evolução, endemismo e conservação dos Medusozoa do Atlântico Sul-Ocidental
• Beneficiário: Antonio Carlos Marques
• Modalidade de apoio: Auxílio à Pesquisa - Temático