History and evolution of the arctic flora: in the footsteps of Eric Hultén

A major contribution to our initial understanding of the origin, history and biogeography of the present-day arctic flora was made by Eric Hultén in his landmark book Outline of the History of Arctic and Boreal Biota during the Quarternary Period, published in 1937. Here we review recent molecular and fossil evidence that has tested some of Hultén's proposals. There is now excellent fossil, molecular and phytogeographical evidence to support Hultén's proposal that Beringia was a major northern refugium for arctic plants throughout the Quaternary. In contrast, most molecular evidence fails to support his proposal that contemporary east and west Atlantic populations of circumarctic and amphi-Atlantic species have been separated throughout the Quaternary. In fact, populations of these species from opposite sides of the Atlantic are normally genetically very similar, thus the North Atlantic does not appear to have been a strong barrier to their dispersal during the Quaternary. Hultén made no detailed proposals on mechanisms of speciation in the Arctic; however, molecular studies have confirmed that many arctic plants are allopolyploid, and some of them most probably originated during the Holocene. Recurrent formation of polyploids from differentiated diploid or more low-ploid populations provides one explanation for the intriguing taxonomic complexity of the arctic flora, also noted by Hultén. In addition, population fragmentation during glacial periods may have lead to the formation of new sibling species at the diploid level. Despite the progress made since Hultén wrote his book, there remain large gaps in our knowledge of the history of the arctic flora, especially about the origins of the founding stocks of this flora which first appeared in the Arctic at the end of the Pliocene (approximately 3 Ma). Comprehensive analyses of the molecular phylogeography of arctic taxa and their relatives together with detailed fossil studies are required to fill these gaps.     

Effects of enhanced UV-B radiation in the field on the concentration of phenolics and chlorophyll fluorescence in two boreal and arctic–alpine lichens

Lichens constitute a prominent part of the vegetation at high latitudes and altitudes, but the effects of UV-B radiation on these symbiotic organisms are not well known. In a northern boreal site (Abisko, northern Sweden), the usnic acid-producing lichens Flavocetraria nivalis and Nephroma arcticum were exposed to enhanced UV-B radiation, corresponding to 25% ozone depletion, for two and one growing seasons, respectively. They were compared with lichens grown under ambient UV-B and harvested fresh from the field. The treated thalli of F. nivalis had been transplanted from a site 24 km from the treatment site. From this source locality, untreated thalli were also harvested. Enhanced UV-B did not affect concentrations of usnic acid and the two depsides phenarctin and nephroarctin. A gradual decline of usnic acid, probably coupled to unusually long periods of dry, sunny weather, was observed both under enhanced and ambient UV-B and in untreated thalli. Photosystem II efficiency in both species was slightly reduced by enhanced UV-B. However, differences between seasons were larger than differences between treatments, which indicate that UV-B effects are minor in comparison to other climatic variables. Concentrations of UV-B-absorbing phenolics in lichens do not show a simple relationship to UV-B dose and therefore cannot be used as bioindicators of UV-B levels.     

Bertilia — A new monotypic genus in the Senecioneae (Asteraceae) from South Africa

The unusual disjunct distribution of the yellow-flowered, radiate, Northern Cape endemic Emilia hantamensis J.C.Manning & Goldblatt, relative to the other Emilia species in southern Africa, prompted investigation into its phylogenetic position and relationships. Phylogenies based on the ITS and trnL–trnF regions reveal that it is not a member of the genus Emilia but belongs in a well-supported clade with Bolandia, a genus comprising five species mainly from the Western and Northern Cape, and the monotypic genera Stilpnogyne and Mesogramma. It is placed sister to Bolandia and its cypselas match those of Bolandia in shape, colour and indumentum, except for a distinct ridge of hairs on the inner rib of the ray cypselas. It is further distinguished from Bolandia by its annual habit and conical disc floret style apices and obtuse to rounded ray floret style apices. It is recognised and described here as a new monotypic genus, Bertilia Cron with the single species B. hantamensis (J.C.Manning & Goldblatt) Cron.     

Chromosome evolution and phylogeny in Ronderosia (Orthoptera,Acrididae, Melanoplinae): clues of survivors to the challenge of sympatry?

In an attempt to unveil the origin of neo‐sex chromosomes in Ronderosia Cigliano grasshoppers, we performed a combined phylogenetic analysis based on morphological (external morphology and male genitalia) and molecular data (COI, COII, 16S and ITS2) to explore the chromosome evolution within the genus. We also analysed the distributional patterns of the various Ronderosia species and considered the possible role of chromosome rearrangements (CRs) in speciation processes within the genus in the light of ‘suppressed‐recombination’ models. We mapped the states of three chromosomal characters on the combined tree topology. The combined evidence supported Ronderosia as a monophyletic group. The cytogenetic analyses of the genus demonstrated the importance of rearranged karyotypes with single, complex and multiples neo‐sex chromosome determination systems in all species. The chromosome character optimisation suggests X‐autosome centric fusion as the mechanism responsible for neo‐sex chromosome formation in most Ronderosia species, except in R. dubia and R. bergii. Similar autosomes were involved in fusions with the ancestral X chromosome in Ronderosia, supporting previous hypotheses on the unique origin of X‐autosome fusion for the sex chromosome in the genus. As a source of chromosome variation, autosome‐autosome centric fusion played a secondary role in Ronderosia compared with other Dichroplini. Given the homogeneity in the morphological features, the sympatric distribution of closely related species and the intrinsic property of centric fusion as suppressors of the crossing over, we suggest that CRs may have played a key role during the speciation process within Ronderosia.     

Importance of demographic history for phylogeographic inference on the arctic–alpine plant Phyllodoce caerulea in East Asia

Arctic–alpine plants have enormous ranges in the Northern Hemisphere. Phylogeographic studies have provided insights into their glacial survival as well as their postglacial colonization history. However, our understanding of the population dynamics of disjunct alpine populations in temperate regions remains limited. During Pleistocene cold periods, alpine populations of arctic–alpine species in East Asia were either connected to an ice-free Beringia refugium or they persisted with prolonged isolation after their establishment. To estimate which of these scenarios is more likely, we elucidated the genetic structure of Phyllodoce caerulea (Ericaceae) in Beringia and northern Japan, East Asia. Sequence variation in multiple nuclear loci revealed that P. caerulea can be distinguished into northern and southern groups. A demographic analysis demonstrated that the north–south divergence did not predate the last glacial period and detected introgression from Phyllodoce aleutica, relative widely distributed in East Asia, exclusively into the southern group. Therefore, although there has been genetic divergence between northern Japan and Beringia in P. caerulea, the divergence is unlikely to have resulted from their prolonged geographic separation throughout several cycles of glacial and interglacial periods. Instead, our study suggests that the introgression contributed to the genetic divergence of P. caerulea and that the range of P. caerulea was plausibly connected between northern Japan and Beringia during the last glacial period. Overall, our study not only provides a biogeographic insight into alpine populations of arctic–alpine plants in East Asia but also emphasizes the importance of careful interpretation of genetic structure for inferring phylogeographic history.     

Respiratory proteins in Sipunculus nudus — Implications for phylogeny and evolution of the hemerythrin family

Three major classes of respiratory proteins are known, hemoglobin, molluscan and arthropod hemocyanin, and hemerythrin (Hr). Similar to hemoglobin, respiratory Hr is packed into erythrocytes floating in the coelomic fluid and is only known from sipunculids, brachiopods, and priapulids. Owing to this scattered distribution, the presence of Hr is generally assumed to be the plesiomorphic condition without phylogenetic importance. By sequencing 2000 Expressed Sequence Tags (ESTs) from Sipunculus nudus, we found 75 Hr-coding ESTs assembled to 20 cDNA contigs classified as four distinct Hr isoforms: three polymeric Hrs (subunit A, A', and B) and the monomeric myo-hemerythrin (myoHr). Phylogenetic analyses revealed a clade of annelid and sipunculan monomeric Hrs, distinct from polymeric Hrs. Monomeric Hrs from annelids and sipunculids can be clustered together using Maximum Likelihood tree-building and network analyses, as well as applying Bayesian methods. Three distinct Hr clusters were found for S. nudus, suggesting a new monomeric Hr isoform.     

The phylogeny and evolution of thePterygodium—Corycium complex (Coryciinae,Orchidaceae)

The leaf-anatomy, palynology, seed-morphology, vegetative morphology and especially the highly complicated floral morphology of theCoryciinae s. str. (Diseae: Orchidoideae: Orchidaceae) are described and illustrated in detail. On the basis of these characters the presumed phylogeny, based on a rigorous cladistic analysis, is presented. The cladistic biogeographical analysis of theCoryciinae s. str. shows that it is a member of the Afrotemperate Track, with a pattern of vicariance events typical of the members of this track. An analysis of the patterns of speciation shows that allopatric speciation appears to be rare, and that parapatric speciation across edaphic boundaries may be the most important factor. Proceeding from the information presented, a new classification of the group is proposed in which we recognize the four generaCeratandra, Evotella, Pterygodium andCorycium. The new monotypic genusEvotella comprises a species originally described asPterygodium rubiginosum. The three species of the genusAnochilus are transferred toCorycium andPterygodium. P. magnum, which was originally described asPterygodium but was transferred toCorycium lately, is placed in a monotypic section ofPterygodium.     

Contrasting effects of biotic interactions on richness and distribution of vascular plants,bryophytes and lichens in an arctic–alpine landscape

Biotic interactions may strongly affect the distribution of individual species and the resulting patterns of species richness. However, the impacts can vary depending on the species or taxa examined, suggesting that the influences of interactions on species distributions and diversity are not always straightforward and can be taxon-contingent. The aim of this study was therefore to examine how the importance of biotic interactions varies within a community. We incorporated three biotic predictors (cover of the dominant vascular species) into two correlative species richness modelling frameworks to predict spatial variation in the number of vascular plants, bryophytes and lichens in arctic–alpine Fennoscandia, in N Europe. In addition, predictions based on single-species distribution models were used to determine the nature of the impact (negative vs. positive outcome) of the three dominant species on individual vascular plant, bryophyte and lichen species. Our results suggest that biotic variables can be as important as abiotic variables, but their relative contributions in explaining the richness of sub-dominant species vary among dominant species, species group and the modelling framework implemented. Similarly, the impacts of biotic interactions on individual species varied among the three species groups and dominant species, with the observed patterns partly reflecting species’ biogeographic range. Our study provides additional support for the importance of biotic interactions in modifying arctic–alpine biodiversity patterns and highlights that the impacts of interactions are not constant across taxa or biotic drivers. The influence of biotic interactions, including the taxon contingency and range-based impacts, should therefore be accounted for when developing biodiversity forecasts.     

Molecular phylogeny of ciliates: What does it tell us about the evolution of the cytoskeleton and of developmental strategies?

An rRNA phylogeny of 22 species of ciliates belonging to seven of Small and Lynn's eight classes has been obtained by distance and parsimony methods. It displays good congruence with classical systematics at low taxonomic levels and several major surprises at higher levels: (1) The species analyzed group into five major branches, four of which emerge almost simultaneously: hypotrichs, oligohymenophorans, lito-stomes, and nassophoreans corresponding to four of Small and Lynn's classes. The simultaneous emergence of these groups contradicts the long accepted view that litostomes (a group with “simple”, symmetrical, apical oral apparatus) are “primitive,” while hypotrichs are “highly evolved.” (2) Heterotrichs group with a karyorelictid, together forming the first emerging branch. While this supports the view that karyorelictids may be early-emerging ciliates, it completely explodes the traditional “spirotrichs” taxon, which united heterotrichs and hypotrichs. Instead, this reinforces the concept of Postciliodesmatophora and suggests that asymmetric oral apparatuses (i.e., with distinct paroral and adoral ciliatures) may be primitive in ciliates. The global topology of the tree therefore does not fit with the classical views of ciliate evolution, from “simple” oral apparatus and stomatogenesis to “complex” ones. Instead, a rather striking agreement with the strategy adopted to construct the cortical framework was disclosed. We noted that the cytoskeletal elements used to strengthen the cell surface could be subdivided into four main types: epiplasm, filaments, continuous microtu-bules, or basal body derived fibers. These four types fitted quite well with the major evolutionary lines disclosed by the molecular phylogeny. We therefore discuss unorthodox hypotheses assuming an early explosive radiation of ciliates into a small number of major lineages differing essentially in the solution adopted to subtend the cell surface and anchor the infraciliature. © 1992 Wiley-Liss, Inc.     

History and evolution of the International Association for Plant Biotechnology (IAPB): 1963–2008

The International Association for Plant Biotechnology (IAPB) was founded in 1963 at the first truly international conference on plant tissue culture, which was organized by Philip R. White. White was a devoted internationalist and was strongly committed to global scientific cooperation. He felt that the time had come for the international tissue culture community to organize so that it could meet regularly and provide a forum to its members for the exchange of ideas and information of mutual interest and use. The various activities of the IAPB since its founding—the publication of its newsletter, its journal, and the proceedings of its quadrennial congresses—faithfully document the remarkable advances in plant biotechnology that were made possible by the successful integration of tissue culture and molecular biology. In particular, the congress proceedings serve as time capsules, providing a wealth of information about the best of science and the most prominent scientists of the time. The history of the IAPB is indeed the history of plant biotechnology.     

A molecular phylogeny of Glaphyridae (Coleoptera: Scarabaeoidea): evolution of pollination and association with ‘Poppy guild’ flowers

Among Scarabaeoidea, pollen feeding occurs in two major lineages, pleurostict Scarabaeidae and Glaphyridae. Here we infer for the first time the phylogeny of the scarabaeoid lineage Glaphyridae (Coleoptera) based on molecular data using partial gene sequences for 28S rRNA, cytochrome oxidase I (cox1) and 16S rRNA (rrnL) for 41 species. Based on the resulting tree topology, we inferred the timing of the origin of pollination and of their coevolution with different flower host taxa, with particular focus on the prominent red-coloured ‘poppy guild’ flowers. All genera of Glaphyridae that were sampled with multiple species were recovered as monophyletic. According to this analysis, the origin of Glaphyridae was around 140 Ma, while crown group divergence was dated to have occurred c. 112 Ma. Pollen feeding originated in Glaphyridae only once and much later than in other important pollinator groups, between 97 and 67 Ma. According to the reconstruction of ancestral feeding traits, Asteraceae (Cicharioidae) were the first hosts of Glaphyridae. Presumably, a further adaptive radiation was triggered by feeding on and pollination of red flowers (poppy guild) which arose at a later stage. It occurred for the first time between 30 and 40 Ma, whereby the clades that use red Ranunculaceae (Pygopleurus spp.) are older than clades using exclusively red Papaveraceae (Eulasia spp.) (25–30 Ma). The rather young age of red Ranunculaceae would imply that Pygopleurus species only subsequently used red Ranunculus species as flower hosts, and that a broad parallel host shift probably from red Papaver spp. to red Ranunculus asiaticus has occurred rather recently.     

Reconstructing vegetation and climate in the Nihewan Basin,North China,during the middle Pleistocene (~603–587 ka) to trace the evolution of human environments

重建中国北方泥河湾盆地中更新世(^~603–587 ka)植被与气候中国北方泥河湾盆地发育了一套含有东方人类活动证据的晚新生代地层,既发现有早更新世(距今~1.66Ma–78ka)直立人使用的石制品,也有中更新世晚期(~370–260ka)早期智人的头盖骨、牙齿等直接证据。该系列地层中孢粉学的研究为我们探索早期人类生存环境提供了可能。本文研究的虎头梁剖面地质年代距今约603–587ka,介于直立人向早期智人演化的过渡时期。基于地层孢粉学组合分析,我们重建了当时的植被从温带针阔混交林-草原(以云杉属、冷杉属、桦木属、胡桃属、蒿属和藜科为主)逐渐向以松、云冷杉为主的针叶林转变的动态过程。通过对比同时期全球其他人类遗址,揭示了早期人类以洞穴生活为主,同时伴随比较开阔的草原或森林-草原植被,以及丰富的哺乳动物。据此,推测本研究揭示的~603–587ka前泥河湾盆地茂密针叶林的出现和开阔草原的消失可能是人类追逐着大多数哺乳动物向草原或森林-草原等开阔地迁移,而离开了泥河湾的新证据。这些新发现有助于增进和丰富我们对早期人类饮食、迁徙和定居等行为方面的认知,同时也填补了泥河湾盆地中更新世(780–400ka)时期古植被与古环境研究的空白。     

Comparison of genetic diversity in the two arctic–alpine plants Diapensia lapponica var. obovata (Diapensiaceae) and Empetrum nigrum var. japonicum (Empetraceae) between Sakhalin in Russian Far East and Jeju Island in Korea, the southernmost edge of their distribution range

We compared allozyme variation in the two arctic–alpine plants Diapensia lapponica var. obovata and Empetrum nigrum var. japonicum between Sakhalin Island in Russian Far East, within their range core, and the Korean island of Jeju, their world’s southernmost distribution. For D. lapponica var. obovata, Sakhalin populations harbored moderate levels of within-population genetic variation and low among-population divergence, whereas extremely low levels of within-population genetic diversity and high among-population differentiation were found in Jeju Island populations. In contrast, we found moderate levels of within-population variation and low among-population differentiation in E. nigrum var. japonicum in both northern populations (those of Sakhalin and an additional population from northern Japan) and Jeju Island populations. Under a similar scenario of immigration history of arctic–alpine plants on Jeju Island during the glacial periods of the Pleistocene and local persistence through glacial/interglacial cycles, the contrasting genetic structure between D. lapponica var. obovata and E. nigrum var. japonicum is mainly attributable to their different life-history, ecological, and demographic traits: (1) hermaphroditic versus monoecious, dioecious or polygamous, (2) seeds with no adaptations for long-distance dispersal versus berry-like drupes dispersed by animals and birds, and (3) a very small patch near the peak of Mt. Halla with a few hundred individuals versus a relatively continuous distribution around the peak of Mt. Halla with numerous individuals. From a conservation perspective, in situ and ex situ conservation measures should be strengthened for D. lapponica var. obovata on Jeju Island given their extreme rarity there.     

Male–male relationships in chimpanzees and the evolution of human pair bonds

The evolution of monogamy has been a central question in biological anthropology. An important avenue of research has been comparisons across “socially monogamous” mammals, but such comparisons are inappropriate for understanding human behavior because humans are not “pair living” and are only sometimes “monogamous.” It is the “pair bond” between reproductive partners that is characteristic of humans and has been considered unique to our lineage. I argue that pair bonds have been overlooked in one of our closest living relatives, chimpanzees. These pair bonds are not between mates but between male “friends” who exhibit enduring and emotional social bonds. The presence of such bonds in male–male chimpanzees raises the possibility that pair bonds emerged earlier in our evolutionary history. I suggest pair bonds first arose as “friendships” and only later, in the human lineage, were present between mates. The mechanisms for these bonds were co-opted for male-female bonds in humans.