Joan Martín

Biology, Genome Evolution, Biotechnological Issues and Research Including Applied Perspectives in Artemisia (Asteraceae)

Abstract Artemisia is one of the largest genera of the family Asteraceae or Compositae, itself the biggest flowering plant family. It comprises around 600 taxa at specific and subspecific levels, present in all continents but Antarctica, mostly distributed in the Northern Hemisphere, with no more than 25 taxa in the Southern Hemisphere. The genus displays a huge ecological plasticity, with species occurring from sea level to high mountains and from arid zones to wetlands. Some species are cosmopolitan, including landscape-dominating plants over large areas, and others are endemics with a quite restricted distribution area. Many species of the genus have economic uses at both folk and industrial levels, and some of them are widely cultivated and submitted to breeding programmes as crops. In this review, we will set out the state of art of Artemisia systematics and phylogeny, as well as all the biological aspects of the genus, with particular attention paid to those of genome organization, and of applied questions related to its useful taxa. In the first part of this chapter, we will review all the systematic points in the genus and in some closely related genera that constitute, with the core genus Artemisia, a pool with controversial structuring. Besides, the infrageneric classification will be addressed. All these questions will be treated in the light of recent molecular phylogenetic studies, which have had an important impact on its systematics and taxonomy. A second part will be devoted to genome organization and evolution in Artemisia, with special attention to cytogenetic data, including genome size, and genetic variability. These points are relevant for understanding the evolutionary pathways in the genus and for applied purposes. The third and fourth parts of the chapter will review, respectively, the uses of Artemisia species in different domains and the biotechnological issues linked to their productivity. Finally, the perspectives of the knowledge and applied aspects of the genus will be addressed.

Lessons from Plectocephalus (Compositae, Cardueae-Centaureinae): ITS disorientation in annuals and Beringian dispersal as revealed by molecular analyses

BACKGROUND AND AIMS The geographic distribution of the genus Plectocephalus comprises a single species in Ethiopia, two in North America and possibly four more in South America, in a striking disjunction that is exceptional for genera of the tribe Cardueae. The enormity of this disjunction cast doubts on the precise taxonomic delineation of the genus, which is not unanimously recognized as a natural entity. The aims of this study were to define the generic boundaries of Plectocephalus and to formulate a hypothesis that would explain its natural range. METHODS A combined molecular approach, using nuclear internal transcribed spacers (ITS) and external transcribed spacers (ETS), and plastid trnL-trnL-F, rpl32-trnL(UAG) and ndhF markers, was chosen for phylogenetic reconstruction by maximum parsimony and Bayesian inference. KEY RESULTS Phylogenetic analysis shows that Plectocephalus is a natural genus that includes the African species P. varians, together with all the native South American species, currently classified as Centaurea, C. cachinalensis, C. floccosa and C. tweediei. The recognition of Centaurodendron as an independent genus, which we consider appropriate, would make Plectocephalus paraphyletic. Affinities of Plectocephalus should lie with eastern representatives of Centaureinae. Geographic disjunction is explained as a consequence of dispersal via the Bering Land Bridge during the Miocene--Pliocene. The phylogeny of the basal grade of Centaureinae differs from previous phylogenies, and artefacts resulting from differences in mutation rates of annual and perennial taxa are confirmed. Sensitivity of ITS to these differences was the highest observed for all DNA regions used in this study. CONCLUSIONS The natural status of the genus Plectocephalus is confirmed and several nomenclatural combinations are proposed. New evidence contributes to the debate concerning problems posed by the use of ITS in the phylogenetic reconstruction of groups that differ in terms of their life cycles. Dispersal from Caucasus and Anatolia along the Siberian route and then across the Bering Land Bridge follows a route previously proposed for other taxonomic groups.

Structure of the apertural sporoderm of pollen grains inEuphorbia andChamaesyce (Euphorbiaceae)

The tricolporate pollen grains of 38 Mediterranean and Macaronesian species ofEuphorbia L. andChamaesyceS. F. Gray have a special apertural sporoderm not found in the other taxa of theEuphorbiaceae. At the apertural margo the ectexine is thinner because of shorter columellae and the thin, fragmented or even absent foot-layer. Ectexinous granules, mixed with endexinous material, are present near the ora. The endexine is homogeneous and thickened under the colpi (at the end and at the proximity of the end of colpus). Around the ora, the endexine is granulate and lamellar with irregular cavities. The apertural intine presents a characteristic structure with thickenings running along both sides of the colpi. The arrangement and structure of these intinous thickenings depend on the distance from the ora. This special morphology of the intine is present in all taxa studied here. The genusEuphorbia is considered to be the most evolved taxon of this family. The characteristic apertural sporoderm may be an adaptative modification to different physiological conditions, so it may present an apertural mechanism which is more adapted to harmomegathic changes and thus facilitate the germination and the formation of the pollen tube.

Phylogenetic and cytogenetic studies reveal hybrid speciation in Saxifraga subsect. Triplinervium (Saxifragaceae)

Hybridization has played an important role in Saxifraga evolution causing reticulation and a high number of described hybrids, but little is known about how hybrid speciation had occurred in the genus. We focus on a group of closely related Saxifraga species of the subsection Triplinervium from Pyrenees, the phylogenetic relationships of which remain unsolved. Trying to unmask cryptic (or ancient) hybridization processes, we analyze one nuclear (ITS) and three plastid regions (rpl32‐trnL, trnS‐trnG‐trnG, and 3′trnV‐ndhC), as well as nuclear DNA content. Pollen and seed morphology and viability studies were carried out to evaluate the status of spontaneous hybrids. DNA ploidy levels were also inferred for the two Madeiran taxa (of the same Saxifraga subsection), where recent hybridization processes are not expected. Molecular markers revealed multiple reticulation events, which, as suggested by DNA content and chromosome numbers, have occurred in homoploidy (without genome doubling after hybridization). In addition, autopolyploidy has occurred in some species or populations, especially in the Madeiran archipelago colonization. Chromosome number variation appears to be related to centric fission events, which also could lead to the formation of the B chromosomes inferred in some taxa. Spontaneous hybrids do not produce viable seeds and this could be due to differences in parental chromosome numbers. Hybrid speciation has probably been successful by chromosomal arrangements, which also generated new, more or less intermediate, chromosomal numbers in this group of taxa.

A correlation study between airborne pollen and cases of pollinosis in humans

This study aims to establish themathematical relationship between allergenicpollen in the air and clinical cases ofpollinosis (hay fever) in humans, and toevaluate the immediate effect of wind and rainon such cases. The pollen was collected inFigueres, Catalonia, Spain (42°30′ Nand 3° E), through a filtration method,in the spring of 1998. Skin tests revealed thatthe antigenic taxa are Olea europaea,Plantago sp., Parietaria officinalisand Gramineae. A linear correlation –with the number of days with presence of pollenas the abscissa and the number of days withcoincidence of pollinosis as the ordinate – wasperformed. The linear correlation coefficientwas 0.9285, at the limit of a directcorrelation by two degrees of freedom.Furthermore, a negative relationship wasobserved between the number of days with rainand number of days with pollinosis, and apositive relationship between the number ofdays with fixed wind speed and number of dayswith pollinosis.