title: Seed coat development in Velloziaceae: primary homology assessment and insights on seed coat evolution.
abstract: •
  
  
  OBJECTIVE
  Seed coat characteristics have historically been used to infer taxonomic relationships and are a potential source of characters for phylogenetic reconstruction. In particular, seed coat morphoanatomy has never been studied in detail in Velloziaceae. One character based on seed surface microsculpture has been used in phylogenies, but was excluded from recent studies owing to problems in primary homology. This work aimed to clarify the origin and general composition of seed coat cell layers in Velloziaceae and to propose hypotheses of primary homology among seed characters.•
  
  
  METHODS
  Seed coat development of 24 Velloziaceae species, comprising nine genera, and one species of Pandanaceae (outgroup) was studied using standard anatomical methods. Developmental data were interpreted in the light of a recently published phylogeny.•
  
  
  RESULTS
  Eight types of seed coat were identified. Whereas the most common type has four distinct cell layers (two-layered tegmen and testa), we encountered much more variation in seed coat composition than previously reported, the analysis of which revealed some potential synapomorphies. For instance, an exotesta with spiral thickenings may be a synapomorphy of Barbacenia.•
  
  
  CONCLUSIONS
  Our results showed that the character states previously used in phylogenies are not based on homologous layers and that the same state was misattributed to species exhibiting quite different seed coats. This study is a first step toward a better understanding of seed coat structure evolution in Velloziaceae.
authors.affiliation: Universidade de São Paulo, Instituto de Biociências, Departamento de Botânica, Rua do Matão 277 05508-090 São Paulo, SP, Brazil.
authors.forename: Mariane S
authors.initials: MS
authors.lastname: Sousa-Baena
authors.affiliation: Universidade de São Paulo, Instituto de Biociências, Departamento de Botânica, Rua do Matão 277 05508-090 São Paulo, SP, Brazil.
authors.forename: Nanuza L
authors.initials: NL
authors.lastname: de Menezes
mesh_terms: D005075:Biological Evolution; D019684:Magnoliopsida / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development; D010802:Phylogeny; D012098:Reproduction; D012639:Seeds / Q000033:anatomy & histology / Q000254:growth & development*
keywords: Pandanales; Velloziaceae; character coding; developmental anatomy; homology; potential synapomorphy; seed coat anatomy