Limits...
Diversification of Angraecum (Orchidaceae, Vandeae) in Madagascar: Revised Phylogeny Reveals Species Accumulation through Time Rather than Rapid Radiation

View Article: PubMed Central - PubMed

ABSTRACT

Angraecum is the largest genus of subtribe Angraecinae (Orchidaceae) with about 221 species. Madagascar is the center of the diversity for the genus with ca. 142 species, of which 90% are endemic. The great morphological diversity associated with species diversification in the genus on the island of Madagascar offers valuable insights for macroevolutionary studies. Phylogenies of the Angraecinae have been published but a lack of taxon and character sampling and their limited taxonomic resolution limit their uses for macroevolutionary studies. We present a new phylogeny of Angraecum based on chloroplast sequence data (matk, rps16, trnL), nuclear ribosomal (ITS2) and 39 morphological characters from 194 Angraecinae species of which 69 were newly sampled. Using this phylogeny, we evaluated the monophyly of the sections of Angraecum as defined by Garay and investigated the patterns of species diversification within the genus. We used maximum parsimony and bayesian analyses to generate phylogenetic trees and dated divergence times of the phylogeny. We analyzed diversification patterns within Angraecinae and Angraecum with an emphasis on four floral characters (flower color, flower size, labellum position, spur length) using macroevolutionary models to evaluate which characters or character states are associated with speciation rates, and inferred ancestral states of these characters. The phylogenetic analysis showed the polyphyly of Angraecum sensu lato and of all Angraecum sections except sect. Hadrangis, and that morphology can be consistent with the phylogeny. It appeared that the characters (flower color, flower size, spur length) formerly used by many authors to delineate Angraecum groups were insufficient to do so. However, the newly described character, position of the labellum (uppermost and lowermost), was the main character delimiting clades within a monophyletic Angraecum sensu stricto. This character also appeared to be associated with speciation rates in Angraecum. The macroevolutionary model-based phylogeny failed to detect shifts in diversification that could be associated directly with morphological diversification. Diversification in Angraecum resulted from gradual species accumulation through time rather than from rapid radiation, a diversification pattern often encountered in tropical rain forests.

No MeSH data available.


Phylogenetic relationships within subtribe Angraecinae.50% Bayesian majority-rule consensus tree from combined plastid data (matK, rps16 and trnL). Values above branches or at nodes represent posterior probability (PP) and bootstrap percentage (BP) support. Dashes represent branches that collapsed in MP strict consensus tree. Colors represent geographic distribution of taxa; in bold are Angraecum sensu Garay species. Abbreviations in brackets denote sections sensu Garay: Aca = Acaulia, Agd = Angraecoides, Ang = Angraecum, Arc = Arachnangraecum, Bor = Boryangraecum, Chl = Chlorangraecum, Fil = Filangis, Gom = Gomphocentrum, Had = Hadrangis, Hum = Humblotiangraecum, Lem = Lemurangis, Lep = Lepervenchea, Pct = Pectinaria, Per = Perrierangraecum, Psj = Pseudojumellea.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5036805&req=5

pone.0163194.g001: Phylogenetic relationships within subtribe Angraecinae.50% Bayesian majority-rule consensus tree from combined plastid data (matK, rps16 and trnL). Values above branches or at nodes represent posterior probability (PP) and bootstrap percentage (BP) support. Dashes represent branches that collapsed in MP strict consensus tree. Colors represent geographic distribution of taxa; in bold are Angraecum sensu Garay species. Abbreviations in brackets denote sections sensu Garay: Aca = Acaulia, Agd = Angraecoides, Ang = Angraecum, Arc = Arachnangraecum, Bor = Boryangraecum, Chl = Chlorangraecum, Fil = Filangis, Gom = Gomphocentrum, Had = Hadrangis, Hum = Humblotiangraecum, Lem = Lemurangis, Lep = Lepervenchea, Pct = Pectinaria, Per = Perrierangraecum, Psj = Pseudojumellea.

Mentions: The MrBayes, BEAST, and MP analyses were congruent. The 50% majority-rule consensus tree from Bayesian analyses of the combined plastid matrix is displayed in Fig 1. Our results support a monophyletic subtribe Angraecinae (PP 1.0, BP 100). Two well-supported clades were identified within Angraecinae: clade I (PP 1.0, BP 77) comprised of Malagasy, IOI, African and American genera, and clade II (PP 1.0, BP 91) with Malagasy and IOI genera. Clade II had more branch support and showed more resolution than clade I. Two main subclades are observed within clade I: a Malagasy-IOI clade A (PP 1.0), and an African-American clade B (PP 1.0). Four Malagasy Angraecum s.l. species (A. perparvulum, A. cf. humile, A. pterophyllum, and A. rhynchoglossum) are nested within clade A. Three major subclades were observed in clade II: Aeranthes (PP 1.0, BP 98), Jumellea (PP 1.0, BP 97), and Angraecum (PP 1.0). Here, we define Angraecum as a monophyletic group including all Angraecum species and all other taxa nested within it in clade II. Based on branch support (PP, BP) and morphological resemblance, eleven clades are observed within Angraecum (Fig 1, clade C to M). From the base to the top of the tree are: clade C (PP 1.0, BP 74) comprised members of sections Pectinaria, Pseudojumellea, Arachnangraecum and Filangis; clade D (PP 1.0, BP 81) comprising member of sections Perrierangraecum, Angraecum, Arachnangraecum and Filangis; clade E (PP 1.0) which includes A. sesquipedale, and A. sororium of section Angraecum; clade F (PP 1.0, BP 100) section Hadrangis; clade G (PP 1.0, BP 61) with section Humblotiangraecum and a member of section Perrierangraecum; clade H (PP 1.0, BP 94) section Boryangraecum; clade I (PP 1.0, BP 100) section Angraecoides; clade J section Arachnangraecum; clade K (PP 1.0, BP 98) section Angraecum (A. eburneum); clade L (PP 1.0, BP 75) comprised of members of sections Angraecum and Pseudojumellea; clade M (PP 1.0, BP 57) composed of sections Acaulia, Boryangraecum, Chlorangraecum, Gomphocentrum, Lemurangis, and Lepervenchea. Clades E and J received weak support despite the fact that their positions were supported in a strict consensus tree. Two species are not included in any of the clades, A. nanum sister to clade I (PP 1.0, BP 72), and A. amplexicaule intermediate between clade L and M (Fig 1). Furthermore, two Malagasy genera, Oeoniella and Sobennikoffia, are nested within Angraecum. Even though many clades were strongly supported within Angraecum, resolution between clades was low.


Diversification of Angraecum (Orchidaceae, Vandeae) in Madagascar: Revised Phylogeny Reveals Species Accumulation through Time Rather than Rapid Radiation
Phylogenetic relationships within subtribe Angraecinae.50% Bayesian majority-rule consensus tree from combined plastid data (matK, rps16 and trnL). Values above branches or at nodes represent posterior probability (PP) and bootstrap percentage (BP) support. Dashes represent branches that collapsed in MP strict consensus tree. Colors represent geographic distribution of taxa; in bold are Angraecum sensu Garay species. Abbreviations in brackets denote sections sensu Garay: Aca = Acaulia, Agd = Angraecoides, Ang = Angraecum, Arc = Arachnangraecum, Bor = Boryangraecum, Chl = Chlorangraecum, Fil = Filangis, Gom = Gomphocentrum, Had = Hadrangis, Hum = Humblotiangraecum, Lem = Lemurangis, Lep = Lepervenchea, Pct = Pectinaria, Per = Perrierangraecum, Psj = Pseudojumellea.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036805&req=5

pone.0163194.g001: Phylogenetic relationships within subtribe Angraecinae.50% Bayesian majority-rule consensus tree from combined plastid data (matK, rps16 and trnL). Values above branches or at nodes represent posterior probability (PP) and bootstrap percentage (BP) support. Dashes represent branches that collapsed in MP strict consensus tree. Colors represent geographic distribution of taxa; in bold are Angraecum sensu Garay species. Abbreviations in brackets denote sections sensu Garay: Aca = Acaulia, Agd = Angraecoides, Ang = Angraecum, Arc = Arachnangraecum, Bor = Boryangraecum, Chl = Chlorangraecum, Fil = Filangis, Gom = Gomphocentrum, Had = Hadrangis, Hum = Humblotiangraecum, Lem = Lemurangis, Lep = Lepervenchea, Pct = Pectinaria, Per = Perrierangraecum, Psj = Pseudojumellea.
Mentions: The MrBayes, BEAST, and MP analyses were congruent. The 50% majority-rule consensus tree from Bayesian analyses of the combined plastid matrix is displayed in Fig 1. Our results support a monophyletic subtribe Angraecinae (PP 1.0, BP 100). Two well-supported clades were identified within Angraecinae: clade I (PP 1.0, BP 77) comprised of Malagasy, IOI, African and American genera, and clade II (PP 1.0, BP 91) with Malagasy and IOI genera. Clade II had more branch support and showed more resolution than clade I. Two main subclades are observed within clade I: a Malagasy-IOI clade A (PP 1.0), and an African-American clade B (PP 1.0). Four Malagasy Angraecum s.l. species (A. perparvulum, A. cf. humile, A. pterophyllum, and A. rhynchoglossum) are nested within clade A. Three major subclades were observed in clade II: Aeranthes (PP 1.0, BP 98), Jumellea (PP 1.0, BP 97), and Angraecum (PP 1.0). Here, we define Angraecum as a monophyletic group including all Angraecum species and all other taxa nested within it in clade II. Based on branch support (PP, BP) and morphological resemblance, eleven clades are observed within Angraecum (Fig 1, clade C to M). From the base to the top of the tree are: clade C (PP 1.0, BP 74) comprised members of sections Pectinaria, Pseudojumellea, Arachnangraecum and Filangis; clade D (PP 1.0, BP 81) comprising member of sections Perrierangraecum, Angraecum, Arachnangraecum and Filangis; clade E (PP 1.0) which includes A. sesquipedale, and A. sororium of section Angraecum; clade F (PP 1.0, BP 100) section Hadrangis; clade G (PP 1.0, BP 61) with section Humblotiangraecum and a member of section Perrierangraecum; clade H (PP 1.0, BP 94) section Boryangraecum; clade I (PP 1.0, BP 100) section Angraecoides; clade J section Arachnangraecum; clade K (PP 1.0, BP 98) section Angraecum (A. eburneum); clade L (PP 1.0, BP 75) comprised of members of sections Angraecum and Pseudojumellea; clade M (PP 1.0, BP 57) composed of sections Acaulia, Boryangraecum, Chlorangraecum, Gomphocentrum, Lemurangis, and Lepervenchea. Clades E and J received weak support despite the fact that their positions were supported in a strict consensus tree. Two species are not included in any of the clades, A. nanum sister to clade I (PP 1.0, BP 72), and A. amplexicaule intermediate between clade L and M (Fig 1). Furthermore, two Malagasy genera, Oeoniella and Sobennikoffia, are nested within Angraecum. Even though many clades were strongly supported within Angraecum, resolution between clades was low.

View Article: PubMed Central - PubMed

ABSTRACT

Angraecum is the largest genus of subtribe Angraecinae (Orchidaceae) with about 221 species. Madagascar is the center of the diversity for the genus with ca. 142 species, of which 90% are endemic. The great morphological diversity associated with species diversification in the genus on the island of Madagascar offers valuable insights for macroevolutionary studies. Phylogenies of the Angraecinae have been published but a lack of taxon and character sampling and their limited taxonomic resolution limit their uses for macroevolutionary studies. We present a new phylogeny of Angraecum based on chloroplast sequence data (matk, rps16, trnL), nuclear ribosomal (ITS2) and 39 morphological characters from 194 Angraecinae species of which 69 were newly sampled. Using this phylogeny, we evaluated the monophyly of the sections of Angraecum as defined by Garay and investigated the patterns of species diversification within the genus. We used maximum parsimony and bayesian analyses to generate phylogenetic trees and dated divergence times of the phylogeny. We analyzed diversification patterns within Angraecinae and Angraecum with an emphasis on four floral characters (flower color, flower size, labellum position, spur length) using macroevolutionary models to evaluate which characters or character states are associated with speciation rates, and inferred ancestral states of these characters. The phylogenetic analysis showed the polyphyly of Angraecum sensu lato and of all Angraecum sections except sect. Hadrangis, and that morphology can be consistent with the phylogeny. It appeared that the characters (flower color, flower size, spur length) formerly used by many authors to delineate Angraecum groups were insufficient to do so. However, the newly described character, position of the labellum (uppermost and lowermost), was the main character delimiting clades within a monophyletic Angraecum sensu stricto. This character also appeared to be associated with speciation rates in Angraecum. The macroevolutionary model-based phylogeny failed to detect shifts in diversification that could be associated directly with morphological diversification. Diversification in Angraecum resulted from gradual species accumulation through time rather than from rapid radiation, a diversification pattern often encountered in tropical rain forests.

No MeSH data available.