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Summary ・Phytochromes play a central role in mediating adaptive responses to light and temperature throughout plant life cycles. Despite evidence for adaptive importance of natural variation in phytochromes, little information is known about molecular mechanisms that modulate physiological responses of phytochromes in nature. ・We show evolutionary divergence in physiological responses relevant to thermal stability of a physiologically active form of phytochrome (Pfr) between two sister species of Brassicaceae growing at different latitudes. The higher latitude species (Cardamine bellidifolia; Cb) responded more strongly to light‐limited conditions compared with its lower latitude sister (C. nipponica; Cn). Moreover, CbPHYB conferred stronger responses to both light‐limited and warm conditions in the phyB‐deficient mutant of Arabidopsis thaliana than CnPHYB: that is Pfr CbphyB was more stable in nuclei than CnphyB. ・Our findings suggest that fine tuning Pfr stability is a fundamental mechanism for plants to optimise phytochrome‐related traits in their evolution and adapt to spatially varying environments, and open a new avenue to understand molecular mechanisms that fine tune phytochrome responses in nature.

The Arctic is one of the most extreme terrestrial environments on the planet. Here, we present the first chromosome‐scale genome assembly of a plant adapted to the high Arctic, Draba nivalis (Brassicaceae), an attractive model species for studying plant adaptation to the stresses imposed by this harsh environment. We used an iterative scaffolding strategy with data from short‐reads, single‐molecule long reads, proximity ligation data, and a genetic map to produce a 302 Mb assembly that is highly contiguous with 91.6% assembled into eight chromosomes (the base chromosome number). To identify candidate genes and gene families that may have facilitated adaptation to Arctic environmental stresses, we performed comparative genomic analyses with nine non‐Arctic Brassicaceae species. We show that the D. nivalis genome contains expanded suites of genes associated with drought and cold stress (e.g., related to the maintenance of oxidation‐reduction homeostasis, meiosis, and signaling pathways). The expansions of gene families associated with these functions appear to be driven in part by the activity of transposable elements. Tests of positive selection identify suites of candidate genes associated with meiosis and photoperiodism, as well as cold, drought, and oxidative stress responses. Our results reveal a multifaceted landscape of stress adaptation in the D. nivalis genome, offering avenues for the continued development of this species as an Arctic model plant., see also the Perspective by Tanja Pyhäjärvi and Tiina M. Mattila

Extreme environments offer powerful opportunities to study how different organisms have adapted to similar selection pressures at the molecular level. Arctic plants have adapted to some of the coldest and driest biomes on Earth and typically possess suites of similar morphological and physiological adaptations to extremes in light and temperature. Here, we compare patterns of molecular evolution in three Brassicaceae species that have independently colonized the Arctic and present some of the first genetic evidence for plant adaptations to the Arctic environment. By testing for positive selection and identifying convergent substitutions in orthologous gene alignments for a total of 15 Brassicaceae species, we find that positive selection has been acting on different genes, but similar functional pathways in the three Arctic lineages. The positively selected gene sets identified in the three Arctic species showed convergent functional profiles associated with extreme abiotic stress characteristic of the Arctic. However, there was little evidence for independently fixed mutations at the same sites and for positive selection acting on the same genes. The three species appear to have evolved similar suites of adaptations by modifying different components in similar stress response pathways, implying that there could be many genetic trajectories for adaptation to the Arctic environment. By identifying candidate genes and functional pathways potentially involved in Arctic adaptation, our results provide a framework for future studies aimed at testing for the existence of a functional syndrome of Arctic adaptation in the Brassicaceae and perhaps flowering plants in general.

Offspring growth rates impact fitness and can be influenced by maternal effects. Despite efforts to understand the influence of maternal traits (e.g. age, size, body condition) on reproductive effort, much less is known about how maternal traits and environment influence the behaviour of offspring and ultimately, how offspring behaviour may influence the efficiency of the translation of maternal investment into offspring growth. Offspring of capital breeders, such as the northern elephant seal, Mirounga angustirostris, are nursed exclusively from maternal body reserves and investment is limited by the resources acquired prior to parturition. Combined new and previously published milk energy intake and offspring storage data (N = 38) suggest impacts of maternal age on growth efficiency that are independent of rates of energy delivery. To determine the mechanisms underlying this effect of maternal age, behavioural data were collected from pups of 46 known-age females, from parturition to weaning, across 6 years and three different sites along the central California coast, representing 3954 seal-hours of observation. Pup behaviours were divided into five mutually exclusive categories that potentially impacted pup energetics. The offspring of older females spent more time resting, while offspring of younger females spent more time locomoting and distant from their mother. As pups developed, they spent more time suckling and locomoting and less time resting. Pup behaviour showed strong diel patterns, with activity decreasing over the day. The magnitude of these relationships varied between rookeries, suggesting influences of harem size, topography or environmental features on pup behaviour. Together these findings suggest direct impacts of maternal age and breeding experience on pup behaviour and growth efficiency.

Background and Aims The Arctic tundra, with its extreme temperatures and short growing season, is evolutionarily young and harbours one of the most species-poor floras on Earth. Arctic species often show little phenotypic and genetic divergence across circumpolar ranges. However, strong intraspecific post-zygotic reproductive isolation (RI) in terms of hybrid sterility has frequently evolved within selfing Arctic species of the genus Draba. Here we assess whether incipient biological species are common in the Arctic flora. Methods We conducted an extensive crossing experiment including six species representing four phylogenetically distant families collected across the circumpolar Arctic. We crossed conspecific parental populations representing different spatial scales, raised 740 F1 hybrids to maturity and measured fertility under laboratory conditions. We examined genetic divergence between populations for two of these species (Cardamine bellidifolia and Ranunculus pygmaeus). Key Results In five of the six species, we find extensive reduction in pollen fertility and seed set in F1 hybrids; 219 (46 %) of the 477 F1 hybrids generated between parents separated by ≥427 km had Conclusion We show that post-zygotic RI has developed multiple times within taxonomically recognized Arctic species belonging to several distantly related lineages, and that RI may have developed over just a few millennia. Rapid and widespread evolution of incipient biological species in the Arctic flora might be associated with frequent bottlenecks due to glacial cycles, and/or selfing mating systems, which are common in the harsh Arctic environment where pollinators are scarce.

The objective of this cross-sectional study was to investigate risk markers indicating the presence of albuminuria in patients with hypertension in rural sub-Saharan Africa (SSA). Urine albumin-creatinine ratio, glycated hemoglobin (HbA1c ), blood pressure, anthropometry, and other patient characteristics including medications were assessed. We identified 160 patients with hypertension, of whom 68 (42.5%) were co-diagnosed with diabetes mellitus (DM). Among the included participants, 57 (35.6%) had albuminuria (microalbuminuria [n=43] and macroalbuminuria [n=14]). A backward multivariate logistic regression model identified age (per 10-year increment) (odds ratio [OR], 1.42; 95% confidence interval [CI], 1.03-1.95), HbA1c >53 compared with

Objectives To investigate the diagnostic accuracy of random blood glucose (RBG) on good glycaemic control among patients with diabetes mellitus (DM) in a rural African setting. Methods Cross-sectional study at St. Francis' Hospital in eastern Zambia. RBG and HbA1c were measured during one clinical review only. Other information obtained was age, sex, body mass index, waist circumference, blood pressure, urine albumin–creatinine ratio, duration since diagnosis and medication. Results One hundred and one patients with DM (type 1 DM = 23, type 2 DM = 78) were included. Spearman's rank correlation coefficient revealed a significant correlation between RBG and HbA1c among the patients with type 2 DM (r = 0.73, P

The Brazilian Cerrado is the most species-rich tropical savanna in the world. Within this biome, the Campos Rupestres (‘rocky savannas’) constitute a poorly studied and highly threatened ecosystem. To better understand how plants characteristic of this vegetation have evolved and come to occupy the now widely-separated patches of rocky formations in eastern Brazil, we reconstruct the biogeographical history of the rare orchid genus Hoffmannseggella. We apply parsimony and Bayesian methods to infer the phylogenetic relationships among 40 out of the 41 described species. Absolute divergence times are calculated under penalized likelihood and compared with estimates from a Bayesian relaxed clock. Ancestral ranges are inferred for all nodes of the phylogeny using Fitch optimization and statistical dispersal vicariance analysis. In all analyses, phylogenetic uncertainty is taken into account by the independent analysis of a large tree sample. The results obtained indicate that Hoffmannseggella underwent rapid radiation around the Middle/Late Miocene (approximately 11–14 Mya). The region corresponding today to southern Minas Gerais acted as a main source area for several independent range expansions north- and eastwards via episodic corridors. These results provide independent evidence that climate cooling following the Middle Miocene Climatic Optimum (approximately 15 Mya) led to important vegetational shifts in eastern Brazil, causing an increase in the dominance of open versus closed habitats. Polyploidy following secondary contact of previously isolated populations may have been responsible for the formation of many species, as demonstrated by the high ploidy levels reported in the genus. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 597–607.

The main objectives of this thesis are to study patterns and processes of plant speciation in arctic and alpine diploid plants. Cryptic species are here referred to as morphologically similar individuals belonging to the same taxonomic species but that are unable to produce fertile offspring (i.e. 'sibling' species). The arctic flora is considered as one of the most species-poor floras of the world, and the latitudinal gradient with decreasing diversity from low to high latitudes is likely the oldest recognised pattern in ecology. However, these estimates are usually based on morphological differentiation into taxonomically recognizable species and may not provide accurate numbers of biological species. Previous intraspecific crossing experiments in three diploid circumpolar species of Draba (Brassicaceae) revealed the presence of numerous cryptic biological species within each taxonomic species. The present study expands the knowledge based on these previously published results and suggests that frequent formation of cryptic biological species may be a general pattern in the arctic flora. Intraspecific crossing experiments including several distantly related circumpolar diploid plant species revealed that intrinsic postzygotic isolation has developed multiple times, even at small geographical scales. This was shown for all five selfing species investigated, whereas crosses within one outcrossing species generated fully fertile F1 hybrids. This suggests that a selfing mating system may accelerate the accumulation of hybrid incompatibilities. The barriers have in addition developed very rapidly, apparently within a few millennia, suggesting that speciation rates are unexpectedly high in the arctic flora. Cryptic biological species, although not yet recognisable morphologically, are thought to represent starting points for new evolutionary lineages that given sufficient time may develop into full-fledged new taxa. Other factors may thus account for the low diversity of the contemporary arctic flora in terms of taxonomic species. It is likely that high extinction rates rather than low speciation rates have played an important role in shaping the extent diversity in the arctic flora, possibly associated with climatic shifts during the Pleistocene glacial cycles. The genetic mechanisms involved in the build-up of reproductive isolation are of central importance in understanding the evolution of new species. This thesis presents further insights into the mechanisms underlying reproductive isolation in Draba nivalis (Brassicaceae) – a small, circumpolar, predominantly selfing diploid herb that demonstrates numerous cryptic biological speciation events. By performing genetic linkage mapping and searching for quantitative trait loci (QTL) associated with reproductive isolation more knowledge about the mechanisms involved in the evolution of intrinsic postzygotic reproduction in this system has been gathered. The linkage map was produced by combining both codominant and dominant markers and resolved eight linkage groups that most likely correspond to the eight chromosomes of D. nivalis. Observed patterns of inheritance were consistent with the influence of both nuclear-nuclear interactions and chromosomal changes. In particular, all seed set QTLs and one pollen fertility QTL displayed underdominant effects, matching expectations of chromosomal speciation models. Theory struggles to account for the establishment of large and strongly underdominant chromosomal translocations. Draba nivalis may however be an exception as a selfing mating system, is conducive for the establishment of chromosomal rearrangements through genetic drift. Overall this study confirms that multiple genetic mechanisms are involved in the build-up of reproductive isolation in D. nivalis, suggesting the involvement of both nuclear-nuclear interactions and structural chromosomal changes. As plants are sessile organisms, they depend largely on adapting to locally changing climatic conditions such as temperature, aridity, and day length. Natural selection acting on traits that respond to such changes has likely played an important role in the evolution of plants. Climatic cycles of the Pleistocene caused drastic changes to species’ ranges. For example, the Japanese alpine endemic plant Cardamine nipponica (Brassicaceae) probably diverged into northern and central populations during the Pleistocene climatic oscillations. The northern and central populations present highly diverged alleles of a particular photoreceptor gene phytochrome E (PHYE). Phytochromes such as PHYE monitor the surrounding light environment, and likely play an important role in the regulation of plant life cycles. The present study infers the evolutionary history of the PHYE in C. nipponica and its close relatives using maximum likelihood models. The resulting genealogical relationship suggested that standing genetic variation of PHYE, which diverged under positive selection prior to speciation, resulted in the selective differentiation between the northern and central Japanese populations of C. nipponica. This further suggests the importance of standing genetic variation in regard to quick responses to climatic changes. List of papers. The papers are removed from the thesis due to publisher restrictions. I. A. Lovisa S. Gustafsson, Galina Gussarova, Liv Borgen, Hajime Ikeda, Jan Suda, Loren H. Rieseberg, Christian Brochmann. High speciation rates in arctic plants. Manuscript. II. A. Lovisa S. Gustafsson, Inger Skrede, Heather C. Rowe, Galina Gussarova, Liv Borgen, Loren H. Rieseberg, Christian Brochmann, Christian Parisod. Genetics of cryptic speciation within an arctic mustard, Draba nivalis. Submitted. III. Hajime Ikeda, A. Lovisa S. Gustafsson, Christian Brochmann, Hiroaki Setoguchi. Pre-speciation origin of selective divergence and balancing selection in a plant photoreceptor gene, phytochrome E. Submitted.

The Brazilian Cerrado is the most species-rich tropical savanna in the world. Within this biome, the Campos Rupestres (‘rocky savannas’) constitute a poorly studied and highly threatened ecosystem. To better understand how plants characteristic of this vegetation have evolved and come to occupy the now widely-separated patches of rocky formations in eastern Brazil, we reconstruct the biogeographical history of the rare orchid genus Hoffmannseggella. We apply parsimony and Bayesian methods to infer the phylogenetic relationships among 40 out of the 41 described species. Absolute divergence times are calculated under penalized likelihood and compared with estimates from a Bayesian relaxed clock. Ancestral ranges are inferred for all nodes of the phylogeny using Fitch optimization and statistical dispersal vicariance analysis. In all analyses, phylogenetic uncertainty is taken into account by the independent analysis of a large tree sample. The results obtained indicate that Hoffmannseggella underwent rapid radiation around the Middle/Late Miocene (approximately 11–14 Mya). The region corresponding today to southern Minas Gerais acted as a main source area for several independent range expansions north- and eastwards via episodic corridors. These results provide independent evidence that climate cooling following the Middle Miocene Climatic Optimum (approximately 15 Mya) led to important vegetational shifts in eastern Brazil, causing an increase in the dominance of open versus closed habitats. Polyploidy following secondary contact of previously isolated populations may have been responsible for the formation of many species, as demonstrated by the high ploidy levels reported in the genus.

Crossing experiments indicate that hybrid sterility barriers frequently have developed within diploid, circumpolar plant species of the genus Draba. To gain insight into the rapid evolution of postzygotic reproductive isolation in this system, we augmented the linkage map of one of these species, D. nivalis, and searched for quantitative trait loci (QTLs) associated with reproductive isolation. The map adds 63 new dominant markers to a previously published dataset of 31 co-dominant microsatellites. These markers include 52 amplified fragment length polymorphisms (AFLPs) and 11 sequence-specific amplified polymorphisms (SSAPs) based on retrotransposon sequence. 22 markers displaying transmission ratio distortion were further included in the map. We resolved eight linkage groups with a total map length of 894 cM. Significant genotype-trait associations, or quantitative trait loci (QTL), were detected for reproductive phenotypes including pollen fertility (4 QTLs), seed set (3 QTLs), flowering time (3 QTLs) and number of flowers (4 QTLs). Observed patterns of inheritance were consistent with the influence of both nuclear-nuclear interactions and chromosomal changes on these traits. All seed set QTLs and one pollen fertility QTL displayed underdominant effects suggestive of the involvement of chromosomal rearrangements in hybrid sterility. Interestingly, D. nivalis is predominantly self-fertilizing, which may facilitate the establishment of underdominant loci and contribute to reproductive isolation.