From morphological variability to taxonomic diversity in Proboscoida (Cnidaria, Hydrozoa): phylogenetic and morphometric inferences for lineages delimitation

Author(s)

Amanda Ferreira e Cunha

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2016-04-27

Examining board members

Antonio Carlos Marques; Alvaro Esteves Migotto; Thaís Pires Miranda; Mariana Cabral de Oliveira; Otto Müller Patrão de Oliveira

• Advisor: Antonio Carlos Marques

Abstract

Morphological variability is common in several marine taxa, and members of Cnidaria Medusozoa are noticeable for expressing variability in many different levels, especially in different phases of the life cycle. However, difficulties in interpreting the levels of variation have posed many taxonomic problems, since intraspecific variations are often misinterpreted as interspecific variations, and vice-versa. In this study, we reassessed patterns of morphological variation in Cnidaria Medusozoa to evaluate their influence on the taxonomy and diversity of the group. Following this approach, we investigated the phylogenetic relationships in the suborder Proboscoida, testing the relevance of traditional morphological diagnostic characters for delimiting lineages in several taxonomic levels. Also, we evaluated their patterns of morphological variation, contrasting morphometric and phylogenetic data. It is clear that in Medusozoa intraspecific variation often parallels interspecific variation, and there is overlap between the different levels. In addition, we show that species diversity in Medusozoa is probably misestimated, and there is still a great potential for the discovery of cryptic species in Hydrozoa. This is true for Proboscoida, since their phylogenetic patterns showed that several groups are not monophyletic, including the family Clytiidae, the genera Campanularia, Clytia, Obelia and Laomedea, and the species Orthopyxis integra, Clytia gracilis and Obelia dichotoma. Similarly, several traditional diagnostic characters were shown not be informative for the delimitation of species and genera. On the other hand, we found consistent morphometric patterns among characters investigated at different levels of comparison. Among them, size and shape of hydrotheca, perisarc thickness, as well as number and height of hydrothecal cusps, supported the delimitation of several lineages. Our results showed the importance of analyses combining phylogenetic and morphometric data, especially when the ranges of variation of morphological characters are compared and investigated in detail. Studies on Hydrozoa, as well as Medusozoa and other marine taxa will benefit from this approach, establishing well grounded valid species and refining our assessments of marine species diversity (AU)

• FAPESP's process: 11/22260-9 - Morphological variation and its phylogenetic signal in marine colonial organisms: a study with the family Campanulariidae (Cnidaria, Hydrozoa)
• Grantee: Amanda Ferreira e Cunha
• Support Opportunities: Scholarships in Brazil - Doctorate