Josep Vigo

Modern pollen—vegetation relationships along an altitudinal transect in the central Pyrenees (southwestern Europe)

Modern proxy-calibration studies are a powerful tool for paleoecological interpretation. This paper analyzes the relationships among modern pollen rain, vegetation and altitude in the central Pyrenees, where several paleo-palynological studies have been developed, but a modern analog survey is still unavailable. The work analyzes the pollen content of moss polsters from different vegetation communities along an altitudinal transect, as well as the flora and vegetation using the Braun-Blanquet system. DCCA showed that altitude satisfactorily explains both vegetation (r 2 = 0.988) and pollen (r 2 = 0.841) gradients. Besides the complexity of pollen—vegetation relationships, some regularities were found to be useful for paleoecological and paleoenvironmental interpretation. In general, altitudinal vegetation and pollen patterns show similarities, but pollen belts and boundaries are less well defined, likely because of the homogenizing effect of upward wind transport. Palynological differentiation of montane from subalpine/alpine belts is straightforward from the trends of the more significant pollen types, mainly the low-altitude deciduous trees and the high-mountain herbs. Palynological differences between subalpine and alpine belts, which boundary coincides with the treeline, are more subtle and need quantitative criteria and complementary proxies. From an individual point of view, four main groups of pollen were distinguished, in relation to their usefulness as vegetation and altitudinal indicators: (1) very good indicators, (2) good indicators, (3) non indicators, and (4) allochthonous pollen types. The first two groups resulted to be useful as indicator taxa for modern analogs for paleovegetational and paleoaltitudinal reconstruction, while the latter two groups should be interpreted with caution in paleoenvironmental studies.

New data on genome size in 128 Asteraceae species and subspecies, with first assessments for 40 genera, 3 tribes and 2 subfamilies

The Asteraceae family has been broadly studied, but the values of genome size of only 3.5% of their species are known. To expand these data, we carried out a flow cytometric study of nuclear DNA content in a wide range of taxa of this family, filling gaps in some less studied groups. In addition, some chromosome counts have been performed (46 taxa, including the first one in two species and one subspecies). We provide genome size data for 167 taxa (184 accessions). Of these, data are new for 128 species and subspecies (141 accessions), 40 genera, three tribes (Barnadesieae, Gochnatieae and Nassauvieae) and two subfamilies (Barnadesioideae and Gochnatioideae). Most values (about 75%) are small or very small (1C ≤ 3.5 pg). The second reports on 17 species previously studied with other methods (i.e. first flow cytometric assessments) are also given. Finally, we contribute results for 22 species for which a first flow cytometric assessment has been published during the preparation of this article. The current data-set moves the percentage of coverage approximately from 3% to 4.7% at the specific level, from 6% to 11.6% at the generic level, from 34.9% to 41.9% at the tribal level and from 33% to 50% at the subfamily level.

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.