Christian Silva | Universidade Estadual de Feira de Sanana (original) (raw)
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Papers by Christian Silva
Background and Aims Recent developments in DNA sequencing, so-called next-generation sequencing (... more Background and Aims Recent developments in DNA sequencing, so-called next-generation sequencing (NGS) methods, can help the study of rare lineages that are known from museum specimens. Here, the taxonomy and evolution of the Malagasy grass lineage Chasechloa was investigated with the aid of NGS. Methods Full chloroplast genome data and some nuclear sequences were produced by NGS from old herbarium specimens, while some selected markers were generated from recently collected Malagasy grasses. In addition, a scanning electron microscopy analysis of the upper floret and cross-sections of the rachilla appendages followed by staining with Sudan IV were performed on Chasechloa to examine the morphology of the upper floret and the presence of oils in the appendages. Key Results Chasechloa was recovered within tribe Paniceae, sub-tribe Boivinellinae, contrary to its previous placement as a member of the New World genus Echinolaena (tribe Paspaleae). Chasechloa originated in Madagascar between the Upper Miocene and the Pliocene. It comprises two species, one of them collected only once in 1851. The genus is restricted to northwestern seasonally dry deciduous forests. The appendages at the base of the upper floret of Chasechloa have been confirmed as elaiosomes, an evolutionary adaptation for myrmecochory. Conclusions Chasechloa is reinstated at the generic level and a taxonomic treatment is presented, including conservation assessments of its species. Our study also highlights the power of NGS technology to analyse relictual or probably extinct groups.
Ichnanthus hoffmannseggii is an annual panicoid grass that occurs in sandy and open areas of Braz... more Ichnanthus hoffmannseggii is an annual panicoid grass that occurs in sandy and open areas of Brazil and currently includes I. piresii in its synonymy. However, herbarium and field work led us to question this circumscription. In a previous phylo-genetic study, a specimen with morphological affinities to I. hoffmannseggii was recovered as more related to Echinolaena oplismenoides (currently I. oplismenoides). This study aimed to clarify the relationship between I. hoffmannseggii, I. oplis-menoides, and I. piresii using molecular and macro-and micromorphological data. We recognize these three taxa as distinct species and provide characters for distinguishing them and related species, including descriptions, comments, illustrations, distribution maps, SEM images of the upper anthecium, and phylogenetic relationships.
Resumo: Ichnanthus hoffmannseggii é uma gramínea panicoide anual que ocorre em áreas abertas e arenosas do Brasil e atualmente inclui I. piresii em sua sinonímia. Entretanto, informações de herbário e de campo nos levaram a questionar essa circun-scrição. Em um estudo filogenético prévio, um espécime com afinidades morfológicas a I. hoffmannseggii foi recuperado como mais relacionado a Echinolaena oplismenoides (atualmente I. oplismenoides). Este estudo objetivou esclarecer a relação entre I. hoffmannseggii, I. oplismenoides e I. piresii utilizando dados moleculares e macro-e micromorfológicos. Os três taxa são aqui reconhecidos como espécies distintas e são fornecidos caracteres para distinguir eles e espécies rela-cionadas, incluindo descrições, comentários, ilustrações, mapas de distribuição, imagens de MEV do antécio superior e as relações filogenéticas.
Canavalia is a pantropical legume genus of lianas comprising approximately 60 species distributed... more Canavalia is a pantropical legume genus of lianas comprising approximately 60 species distributed in a wide range of habitats. In the last taxonomic revision, the genus was divided into four subgenera: Canavalia (Pantropical), Catodonia (Neotropical, excepting one species also found in the Old World), Maunaloa (Hawaiian), and Wenderothia (Neotropical). In this study, we reconstructed the phylogeny of Canavalia using a broad taxon sampling and analyses of nuclear (ETS and ITS) and plastid markers (trnK/matK). We evaluated the infrageneric classification of the genus and investigated its biogeograph-ical history using molecular dating analyses and ancestral area reconstructions. The phylogenetic analyses resolved subgenus Wenderothia as monophyletic. Subgenus Catodonia needs to be recircumscribed and the relationships between subgenera Canavalia and Maunaloa remain unclear. Canavalia arose during the Miocene with a mean stem age estimate of 13.8 Ma and mean crown age estimate of 8.7 Ma, and most extant species evolved during the Pleistocene. Several climatic and geological events are chronologically coincident with the divergence of the major clades of Canavalia (glacial/interglacial periods, Andes uplift and the formation of Pebas and post-Pebas systems, closure of the Isthmus of Panama, and change in the direction of ocean currents). Ancestral area reconstructions for the early divergence of the genus are equivocal, although, some evidence suggests Canavalia originated in the wet forests of South America and achieved its current pantropical distribution through recent transoceanic dispersal. The evolution of Canavalia is better explained by a series of several processes than by discrete historical events.
Rodriguésia, 2012
ABSTRACT
Echinolaena and Ichnanthus are two tropical grass genera distributed mostly in the Americas, char... more Echinolaena and Ichnanthus are two tropical grass genera distributed mostly in the Americas, character-
ized by the presence of rachilla appendages in the shape of convex swellings, scars or wings at the base of
the upper anthecium. However, recent studies have shown that rachilla appendages arose several times
independently in several groups within Paniceae and Paspaleae (Panicoideae). Thus, this study aimed to
assess the monophyly of Echinolaena and Ichnanthus and their relationship to other genera of Paniceae
and Paspaleae, especially those including species with rachilla appendages. Parsimony and Bayesian anal-
yses of the cpDNA regions ndhF, rpl16, trnH-(rps19)-psbA, trnL-trnF, trnS-(psbZ)-trnG, and the rDNA ITS
region included 29 of the 39 known species of Echinolaena and Ichnanthus, 23 of which were sampled
for the first time. The multiple loci analyses indicated that Echinolaena and Ichnanthus are polyphyletic
in their current circumscriptions, with species in four distinct lineages within subtribe Paspalinae, each
one characterized by a single type of rachilla appendage. Thus, Echinolaena and Ichnanthus are each cir-
cumscribed in a narrow sense, and the other two lineages excluded from them are proposed as the new
genera Hildaea and Oedochloa, resulting in 15 new combinations and the restablishment of I. oplis-
menoides Munro ex Döll.
Background and Aims Recent developments in DNA sequencing, so-called next-generation sequencing (... more Background and Aims Recent developments in DNA sequencing, so-called next-generation sequencing (NGS) methods, can help the study of rare lineages that are known from museum specimens. Here, the taxonomy and evolution of the Malagasy grass lineage Chasechloa was investigated with the aid of NGS. Methods Full chloroplast genome data and some nuclear sequences were produced by NGS from old herbarium specimens, while some selected markers were generated from recently collected Malagasy grasses. In addition, a scanning electron microscopy analysis of the upper floret and cross-sections of the rachilla appendages followed by staining with Sudan IV were performed on Chasechloa to examine the morphology of the upper floret and the presence of oils in the appendages. Key Results Chasechloa was recovered within tribe Paniceae, sub-tribe Boivinellinae, contrary to its previous placement as a member of the New World genus Echinolaena (tribe Paspaleae). Chasechloa originated in Madagascar between the Upper Miocene and the Pliocene. It comprises two species, one of them collected only once in 1851. The genus is restricted to northwestern seasonally dry deciduous forests. The appendages at the base of the upper floret of Chasechloa have been confirmed as elaiosomes, an evolutionary adaptation for myrmecochory. Conclusions Chasechloa is reinstated at the generic level and a taxonomic treatment is presented, including conservation assessments of its species. Our study also highlights the power of NGS technology to analyse relictual or probably extinct groups.
Ichnanthus hoffmannseggii is an annual panicoid grass that occurs in sandy and open areas of Braz... more Ichnanthus hoffmannseggii is an annual panicoid grass that occurs in sandy and open areas of Brazil and currently includes I. piresii in its synonymy. However, herbarium and field work led us to question this circumscription. In a previous phylo-genetic study, a specimen with morphological affinities to I. hoffmannseggii was recovered as more related to Echinolaena oplismenoides (currently I. oplismenoides). This study aimed to clarify the relationship between I. hoffmannseggii, I. oplis-menoides, and I. piresii using molecular and macro-and micromorphological data. We recognize these three taxa as distinct species and provide characters for distinguishing them and related species, including descriptions, comments, illustrations, distribution maps, SEM images of the upper anthecium, and phylogenetic relationships.
Resumo: Ichnanthus hoffmannseggii é uma gramínea panicoide anual que ocorre em áreas abertas e arenosas do Brasil e atualmente inclui I. piresii em sua sinonímia. Entretanto, informações de herbário e de campo nos levaram a questionar essa circun-scrição. Em um estudo filogenético prévio, um espécime com afinidades morfológicas a I. hoffmannseggii foi recuperado como mais relacionado a Echinolaena oplismenoides (atualmente I. oplismenoides). Este estudo objetivou esclarecer a relação entre I. hoffmannseggii, I. oplismenoides e I. piresii utilizando dados moleculares e macro-e micromorfológicos. Os três taxa são aqui reconhecidos como espécies distintas e são fornecidos caracteres para distinguir eles e espécies rela-cionadas, incluindo descrições, comentários, ilustrações, mapas de distribuição, imagens de MEV do antécio superior e as relações filogenéticas.
Canavalia is a pantropical legume genus of lianas comprising approximately 60 species distributed... more Canavalia is a pantropical legume genus of lianas comprising approximately 60 species distributed in a wide range of habitats. In the last taxonomic revision, the genus was divided into four subgenera: Canavalia (Pantropical), Catodonia (Neotropical, excepting one species also found in the Old World), Maunaloa (Hawaiian), and Wenderothia (Neotropical). In this study, we reconstructed the phylogeny of Canavalia using a broad taxon sampling and analyses of nuclear (ETS and ITS) and plastid markers (trnK/matK). We evaluated the infrageneric classification of the genus and investigated its biogeograph-ical history using molecular dating analyses and ancestral area reconstructions. The phylogenetic analyses resolved subgenus Wenderothia as monophyletic. Subgenus Catodonia needs to be recircumscribed and the relationships between subgenera Canavalia and Maunaloa remain unclear. Canavalia arose during the Miocene with a mean stem age estimate of 13.8 Ma and mean crown age estimate of 8.7 Ma, and most extant species evolved during the Pleistocene. Several climatic and geological events are chronologically coincident with the divergence of the major clades of Canavalia (glacial/interglacial periods, Andes uplift and the formation of Pebas and post-Pebas systems, closure of the Isthmus of Panama, and change in the direction of ocean currents). Ancestral area reconstructions for the early divergence of the genus are equivocal, although, some evidence suggests Canavalia originated in the wet forests of South America and achieved its current pantropical distribution through recent transoceanic dispersal. The evolution of Canavalia is better explained by a series of several processes than by discrete historical events.
Rodriguésia, 2012
ABSTRACT
Echinolaena and Ichnanthus are two tropical grass genera distributed mostly in the Americas, char... more Echinolaena and Ichnanthus are two tropical grass genera distributed mostly in the Americas, character-
ized by the presence of rachilla appendages in the shape of convex swellings, scars or wings at the base of
the upper anthecium. However, recent studies have shown that rachilla appendages arose several times
independently in several groups within Paniceae and Paspaleae (Panicoideae). Thus, this study aimed to
assess the monophyly of Echinolaena and Ichnanthus and their relationship to other genera of Paniceae
and Paspaleae, especially those including species with rachilla appendages. Parsimony and Bayesian anal-
yses of the cpDNA regions ndhF, rpl16, trnH-(rps19)-psbA, trnL-trnF, trnS-(psbZ)-trnG, and the rDNA ITS
region included 29 of the 39 known species of Echinolaena and Ichnanthus, 23 of which were sampled
for the first time. The multiple loci analyses indicated that Echinolaena and Ichnanthus are polyphyletic
in their current circumscriptions, with species in four distinct lineages within subtribe Paspalinae, each
one characterized by a single type of rachilla appendage. Thus, Echinolaena and Ichnanthus are each cir-
cumscribed in a narrow sense, and the other two lineages excluded from them are proposed as the new
genera Hildaea and Oedochloa, resulting in 15 new combinations and the restablishment of I. oplis-
menoides Munro ex Döll.