Joachim W. Kadereit

The effect of Quaternary climatic changes on plant distribution and evolution

Abstract Climatic oscillations in the Quaternary have played a major role in changing the geographical distribution of plant species. Recent molecular work has provided new insights into the location of glacial refugia and routes of postglacial expansion. A comparative analysis shows that phylogeographic patterns in Europe appear to be less congruent than in North America. The change of geographical distribution has also provided opportunities for speciation through isolation, and hybridization after secondary contact. However, a complete understanding of the significance of the Quaternary climatic changes for plant speciation requires further research into the estimation of reliable and accurate divergence times.

Differential cycles of range contraction and expansion in European high mountain plants during the Late Quaternary: insights from Pritzelago alpina (L.) O. Kuntze (Brassicaceae)

Nuclear DNA sequence variation of the internal transcribed spacer (ITS) and amplified fragment length polymorphisms (AFLPs) were used to illuminate the evolutionary history of Pritzelago alpina, a herbaceous perennial of (sub)alpine to nival habitats of the European high mountains. Maximum likelihood analysis of ITS sequences of P. alpina, Hornungia petraea and Hymenolobus procumbens (the ‘Pritzelago alliance’) resolved P. alpina and H. petraea as sister taxa. ITS divergence estimates support an origin for P. alpina in the Late Tertiary, while intraspecific diversification started in the Late Quaternary (0.4–0.9 million years ago). AFLP analysis of 76 individuals of P. alpina, representing 24 localities across its entire west–east distribution, identified four mountain lineages in Cantabria, the Pyrenees, (south‐) western Alps, and northeastern Alps/Tatras/Carpathians. In an analysis of molecular variance (amova), 14.3% of the total variation derived from this separation. However, relationships among these lineages remained unresolved in neighbour‐joining and principal co‐ordinates analyses, suggesting a population history of near simultaneous vicariance. Comparison with our previous ITS/AFLP study of Anthyllis montana (Fabaceae) indicates that the two co‐distributed but altitudinally differentiated plant species exhibit temporally concordant but spatially discordant patterns of genetic variation. Moreover, levels of AFLP divergence were significantly lower in P. alpina than in the submediterranean, lower‐elevation A. montana. Together, these data are consistent with a ‘displacement refugia model’, which predicts that European mountain plant species associated with lower‐ and upper‐elevation habitats had a different cycle of range contraction into (long‐term) glacial and (short‐term) interglacial refugia, respectively.

An ITS phylogeny of tribe Senecioneae (Asteraceae) and a new delimitation of Senecio L

Senecioneae is the largest tribe ofAsteraceae, comprised ofca. 150 genera and 3,000 species. Approximately one-third of its species are placed in Senecio, making it one of the largest genera of flowering plants. Despite considerable efforts to classify and understand the striking morphological diversity in Senecioneae, little is known about its intergeneric relationships. This lack ofphylogenetic understanding is predominantly caused by conflicting clues from morphological characters, the large size ofthe tribe, and the absence of a good delimitation of Senecio. Phylogenetic analyses of nrITS and plastid DNA sequence data were used to produce a hypothesis of evolutionary relationships in Senecioneae and a new, monophyletic, delimitation of Senecio. The results of separate and combined phylogenetic analyses of the two datasets were compared to previous taxonomic treatments, morphological and karyological data, and biogeographic patterns. These studies indicate that the subtribal delimitation of Senecioneae needs to be revised to reflect exclusively monophyletic subtribes. This would involve abolishing subtribes Adenostylinae, Blennospermatinae, and Tephroseridinae and recognizing subtribes Abrotanellinae, Othonninae, and Senecioninae. Moreover, Tussilagininae may need to be split into three or four subtribes: Brachyglottidinae, Chersodominae, Tussilagininae, and perhaps Doronicinae. On the intergeneric level, these phylogenies provide new insights into evolutionary relationships, resulting in a first approximation of a comprehensive phylogeny for the tribe. Most species currently assigned to Senecio form a well supported clade. Thus, a new delimitation of Senecio is proposed, which involves transferring the species ofAetheolaena, Culcitium, Hasteola, locenes, Lasiocephalus, and Robinsonia to Senecio and removing several Senecio groups that are only distantly related to the core of Senecio. Area optimization analyses indicate a strong African influence throughout the evolutionary history of Senecioneae, predominantly in subtribes Senecioninae and Othonninae.

Phylogeny and quaternary history of the European montane/alpine endemic Soldanella (Primulaceae) based on ITS and AFLP variation.

Soldanella contains 16 species of herbaceous perennials that are endemic to the central and south European high mountains. The genus is ecogeographically subdivided into forest/montane and alpine species. Evolutionary relationships and large-scale biogeographic patterns were inferred from parsimony analyses of the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA, and genetic distance analyses based on amplified fragment length polymorphism (AFLP) markers. The ITS region proved useful for examining subgeneric relationships and testing hypotheses on genus-wide divergence times, whereas the AFLP markers were suitable for studying relationships among closely related taxa and biogeographic patterns of divergence. Neither ITS nor AFLP data supported sectional delimitations, particularly those related to the grouping of S. alpina (sect. Soldanella) with S. pusilla (sect. Tubiflores), which may be the result of hybridization. Additional results and conclusions drawn are (1) Soldanella is derived from an ancestor of Asian origin with a montane ecology; (2) estimates of divergence times suggest a late Quaternary origin of the genus; (3) alpine species of sect. Tubiflores diverged from within a paraphyletic sect. Soldanella of mainly montane species; (4) alpine and montane species of Soldanella experienced different cycles of range expansion and contraction during late Quaternary climatic changes, resulting in differential patterns of geographic distribution; and (5) AFLP divergence among montane species from eastern Europe was lower than between alpine species; we hypothesize that the latter differentiated in allopatric regions of expansion during glacials, while the former experienced secondary contact at lower elevations in more southern refugia.

The colonization history of Olea europaea L. in Macaronesia based on internal transcribed spacer 1 (ITS-1) sequences, randomly amplified polymorphic DNAs (RAPD), and intersimple sequence repeats (ISSR)

Phylogenetic relationships in the Olea europaea complex and the phylogeography of 24 populations of the Macaronesian olive (O. europaea ssp. cerasiformis) were assessed by using three molecular markers: nuclear ribosomal internal transcribed spacer 1 (ITS‐1) sequences, randomly amplified polymorphic DNAs (RAPD), and intersimple sequence repeats (ISSR). Parsimony analysis of the ITS‐1 sequences and Neighbour‐joining (NJ) analyses of RAPD and ISSR banding variation revealed four major lineages in the O. europaea complex: (1) ssp. cuspidata; (2) ssp. cerasiformis from Madeira; (3) ssp. laperrinei; and (4) ssp. cerasiformis from the Canary Islands plus ssp. europaea. These results provide unequivocal support for two independent dispersal events of Olea to the Madeira and Canary Islands. Molecular and morphological evidence led to recognition of two separate olive taxa in Macaronesia, to date included in ssp. cerasiformis. NJ analyses of the combined RAPD and ISSR data suggest that the colonization of the Canaries by O. europaea may have followed an east to west stepping‐stone model. An interisland dispersal sequence can be recognized, starting from the continent to Fuerteventura, Gran Canaria, Tenerife, La Gomera, and finally La Palma. High dispersal activity of the lipid‐rich Olea fruits by birds in the Mediterranean region is congruent with multiple dispersal of olives to Macaronesia and successive colonization of the archipelagos. The observation of strong genetic isolation between populations of different islands of the Canary Islands suggests, however, that subsequent interisland dispersal and establishment has been very rare or may not have occurred at all.

The phylogeny of Gentianella (Gentianaceae) and its colonization of the southern hemisphere as revealed by nuclear and chloroplast DNA sequence variation

Abstract The generic circumscription and infrageneric phylogeny of Gentianella was analysed based on matK and ITS sequence variation. Our results suggested that Gentianella is polyphyletic and should be limited to species with only one nectary per petal lobe. Gentianella in such a circumscription is most closely related to one part of a highly polyphyletic Swertia. within uninectariate Gentianella two major groups could be recognized: 1) northern hemispheric species with vascularized fimbriae at the base of the corolla lobes, and 2) northern hemispheric, South American, and Austrlia/New Zealand species without vascularized fimbriae. When fimbriae are present in this latter group, they are non-vascularized. whereas ITS data suggested a sister group relationship between the fimbriate and efimbriate group, the matK data suggested paraphyly of the efimbriate group with Eurasian efimbriate species as sister to the remainder of the clade. Based on the phylogeny and using geological and fossil evidence and a molecular clock approach, it is postulated that the efimbriate lineage originated in East Asia near the end of the Tertiary. From East Asia it spread via North america to south America, and from there it reached Australia/New Zealand only once by a single long-distance dispersal event. The place of origin of the fimbriate lineage remained doubtful. The high specific diversity of Gentianella in South America probably resulted mainly from the availability of a very large alpine area open to colonization rather than from particularly high speciation rates in comparison to other taxa.

Late Quaternary distributional stasis in the submediterranean mountain plant Anthyllis montana L. (Fabaceae) inferred from ITS sequences and amplified fragment length polymorphism markers

Anthyllis montana is a submediterranean, herbaceous plant of the southern and central European mountains. The internal transcribed spacer (ITS) regions of nuclear ribosomal DNA were sequenced from multiple accessions of the species and several closely related taxa. In addition, amplified fragment length polymorphism (AFLP) was analysed from 71 individuals of A. montana collected in 20 localities, mainly in the Pyrenees, Alps, Italian Peninsula and Balkans. Our ITS phylogeny showed a sequential branching pattern in A. montana, implying a western Mediterranean origin followed by an eastward migration. ITS clock calibrations suggest that speciation of A. montana took place at the Pliocene–Pleistocene boundary, while intraspecific divergence dates to Late Quaternary times (i.e. 0.7 million years ago). The AFLP analyses revealed a major genetic (west/east) subdivision within A. montana, probably caused by the massive glaciation of the Alps during this latter time period. The present‐day absence of A. montana from vast parts of the Alps, which appear ecologically suitable for the species, together with the finding of evenly distributed AFLP variability within each of the two western and eastern lineages identified, is taken as evidence for a largely static Late Quaternary history without large‐scale migration. High levels of AFLP variation observed among populations, together with weak or absent patterns of isolation by distance, seem to be in accord with long‐term population insularization and distributional stasis. However, recent small‐scale migration and a narrow hybrid zone between western and eastern lineages need to be postulated to explain the intermediate genetic composition of individuals from the Maritime Alps, a well‐known suture‐zone for other plant and animal species.

Patterns and causes of incongruence between plastid and nuclear Senecioneae (Asteraceae) phylogenies

One of the longstanding questions in phylogenetic systematics is how to address incongruence among phylogenies obtained from multiple markers and how to determine the causes. This study presents a detailed analysis of incongruent patterns between plastid and ITS/ETS phylogenies of Tribe Senecioneae (Asteraceae). This approach revealed widespread and strongly supported incongruence, which complicates conclusions about evolutionary relationships at all taxonomic levels. The patterns of incongruence that were resolved suggest that incomplete lineage sorting (ILS) and/or ancient hybridization are the most likely explanations. These phenomena are, however, extremely difficult to distinguish because they may result in similar phylogenetic patterns. We present a novel approach to evaluate whether ILS can be excluded as an explanation for incongruent patterns. This coalescence-based method uses molecular dating estimates of the duration of the putative ILS events to determine if invoking ILS as an explanation for incongruence would require unrealistically high effective population sizes. For four of the incongruent patterns identified within the Senecioneae, this approach indicates that ILS cannot be invoked to explain the observed incongruence. Alternatively, these patterns are more realistically explained by ancient hybridization events.

Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae)

To explore the biogeographic history of Mediterranean/arid plant disjunctions, Old and New World Senecio sect. Senecio were analyzed phylogenetically using nuclear ribosomal DNA sequences (ITS). A clade corresponding to sect. Senecio was strongly supported. Area optimization indicated this clade to be of southern African origin. The Mediterranean and southern African floras were not distinguishable as sources of the main New World lineage, estimated to have become established during the middle Pliocene. Another previously suspected recent dispersal to the New World from the Mediterranean was confirmed for the recently recognized disjunction in S. mohavensis. The loss of suitable land connections by the Miocene means that both New World lineages must represent long-distance dispersal, providing the first evidence of repeat intercontinental dispersal in a Mediterranean group. In contrast, migration within Africa may have utilized an East African arid corridor. Recent dispersal to northern Africa is supported for S. flavus, which formed part of a distinct southern African lineage. Novel pappus modifications in both disjunct species may have enabled dispersal by birds. An estimated early Pliocene origin of sect. Senecio coincides with the appearance of summer-dry climate. However, diversification from 1.6 BP highlights the importance of Pleistocene climate fluctuations for speciation.

Historical biogeography in a linear system: genetic variation of Sea Rocket (Cakile maritima) and Sea Holly (Eryngium maritimum) along European coasts

The exclusively coastal Cakile maritima and Eryngium maritimum represent a linear biogeographical system. Genetic variation among 25 individuals of C. maritima and 16 individuals of E. maritimum, from the coasts of Europe, North Africa and the Canary Islands, was analysed using random amplified polymorphic DNAs (RAPDs) and intersimple sequence repeats (ISSRs). Genetic distances (Dice) were calculated and used to investigate the correlation between genetic and geographical distances, to construct Neighbour Joining (NJ) trees, and to compare mean genetic distances between areas within and across species. Genetic distances and geographical distances measured along the coast are well correlated in Cakile and Eryngium. This implies that dispersal in both species is largely along the coast. The NJ analyses resulted in the recognition of Atlantic and Mediterranean clusters in both Cakile and Eryngium. The genetic distance between these two clusters is much larger in Eryngium (0.285) than in Cakile (0.037). Mean genetic distances are substantially higher in the Mediterranean than in the Atlantic clusters in both species, and higher in Cakile than in Eryngium particularly in the Atlantic cluster. It is argued that all similarities and differences between the two species can be explained with the presumed distribution of the two species in the Würm glacial as reconstructed from their extant temperature requirements, the distribution of ice cover, permafrost, and sea surface temperatures in that period, and indirect fossil evidence.