Comparative micromorphology of petals in Macaronesian Lotus (Leguminosae) reveals a loss of papillose conical cells during the evolution of bird pollination
Ojeda I, Santos-Guerra A, Caujapé-Castells J, Jaén-Molina R, Marrero Á, Cronk QCB
International Journal of Plant Sciences 173: 365-374
Bird pollination has evolved in four species of Macaronesian Lotus from a bee-pollinated ancestor. The transition is associated with the modification of several floral traits, including flower color and size, relative size and orientation of the petals, and nectar composition and quantity. Here, we examine petal surface micromorphology in relation to pollination type, using SEM and LM. In the bee-pollinated Lotus (the majority of the genus), papillose conical cells (PCS) are the most abundant epidermal type on dorsal and lateral petals. However, bird-pollinated species completely lack PCS on their dorsal petals and have only a small patch of PCS in a highly localized region of the lateral petal. In the bee-pollinated species (including those most closely related to the bird-pollinated species), PCS develop early in floral development. In contrast, the small amount of residual PCS in bird-pollinated species forms later in development, after the other two major epidermal types have been formed. The almost complete elimination of PCS during the shift of pollination syndrome from bee to birds may be adaptively driven as a both probird and antibee trait.
Molecular taxonomy of Dunaliella (Chlorophyceae) with a special focus on D. salina: ITS-2 sequences revisited with an extensive geographical sampling
Assunçao P, Jaén-Molina R, Caujapé-Castells J, De la Jara A, Carmona L, Freijanes K, Mendoza H
Aquatic Biosystems 8:2 (2012 in press, doi:10.1186/2046-9063-8-2)
We used ITS2 primary and secondary structure and Compensatory Base Changes (CBCs) analyses on new French and Spanish Dunallela salina strains to investigate their phylogenetic position and taxonomic status within the genus Dunaliella. Our analyses show a great diversity within D. salina (with only some clades not statistically supported) and reveal considerable genetic diversity and structure within Dunaliella, although the CBC analysis did not bolster the existence of different biological groups within this taxon. The ITS2 sequences of the new Spanish and French D. salina strains were very similar except for two of them: ITC5105 "Janubio" from Spain and ITC5119 from France. Although the Spanish one had a unique ITS2 sequence profile and the phylogenetic tree indicates that this strain can represent a new species, this hypothesis was not confirmed by CBCs, and clarification of its taxonomic status requires further investigation with new data. Overall, the use of CBCs to define species boundaries within Dunaliella was not conclusive in some cases, and the ITS2 region does not contain a geographical signal overall.
The origin of bird pollination in Macaronesian Lotus (Loteae, Leguminosae)
Ojeda I, Santos-Guerra A, Jaén-Molina R, Oliva-Tejera F, Caujapé-Castells J, Cronk Q
Molecular Phylogenetics and Evolution 62: 306-318 (2012)
The four red-flowered, apparently bird-pollinated Lotus species from the Canary Islands have previously been classified in their own genus, Rhyncholotus. Currently, they are considered as a separate section within genus Lotus, distinct from other herbaceous Canarian congeners which are yellow-flowered and bee-pollinated. A combined analysis of four nuclear regions (including ITS and three homologues of CYCLOIDEA) and three plastid regions (CYB6, matK and trnH-psbA) nests the four bird-pollinated species within a single extant species of bee-pollinated Lotus (L. sessilifolius), in a very extreme example of species paraphyly. Therefore, our data compellingly support the hypothesis that the Macaronesian Lotus species with a bird pollination syndrome are recently derived from entomophilous ancestors. Calibration of the phylogenetic trees using geological age estimates of the most recent islands (La Palma and El Hierro) together with oldest ages of Fuerteventura indicates that bird pollination evolved ca. 1.7 Ma in the Canarian Lotus. These four bird-pollinated species share a most recent common ancestor (MRCA) with L. sessilifolius that dates to about 2.2 Ma. Our analyses further suggest that the evolution of the bird pollination syndrome was likely triggered by the availability of new niches in La Palma and Tenerife as a result of recent volcanic activity.
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