UV‐B radiation damage in leaves is prevented by epidermal UV‐screening compounds that can be modulated throughout ontogeny. In epiphytic orchids, roots need to be protected against UV‐B because they ...photosynthesize, sometimes even replacing the leaves. How orchid roots, which are covered by a dead tissue called velamen, avoid UV‐B radiation is currently unknown. We tested for a UV‐B protective function of the velamen using gene expression analyses, mass spectrometry, histochemistry, and chlorophyll fluorescence in Phalaenopsis × hybrida roots. We also investigated its evolution using comparative phylogenetic methods. Our data show that two paralogues of the chalcone synthase (CHS) gene family are UV‐B‐induced in orchid root tips, triggering the accumulation of two UV‐B‐absorbing flavonoids and resulting in effective protection of the photosynthetic root cortex. Phylogenetic and dating analyses imply that the two CHS lineages duplicated c. 100 million yr before the rise of epiphytic orchids. These findings indicate an additional role for the epiphytic orchid velamen previously thought to function solely in absorbing water and nutrients. This new function, which fundamentally differs from the mechanism of UV‐B avoidance in leaves, arose following an ancient duplication of CHS, and has probably contributed to the family's expansion into the canopy during the Cenozoic.
Animal-pollinated plants have to get pollen to a conspecific stigma while protecting it from getting eaten. Touch-sensitive stamens, which are found in hundreds of flowering plants, are thought to ...function in enhancing pollen export and reducing its loss, but experimental tests are scarce. Stamens of
and
are inserted between paired nectar glands and when touched by an insect's tongue rapidly snap forward so that their valvate anthers press pollen on the insect's tongue or face. We immobilized the stamens in otherwise unmodified flowers and studied pollen transfer in the field and under enclosed conditions. On flowers with immobilized stamens, the most common bee visitor stayed up to 3.6× longer, yet removed 1.3× fewer pollen grains and deposited 2.1× fewer grains on stigmas per visit. Self-pollen from a single stamen hitting the stigma amounted to 6% of the grains received from single bee visits. Bees discarded pollen passively placed on their bodies, likely because of its berberine content; nectar has no berberine. Syrphid flies fed on both nectar and pollen, taking more when stamens were immobilized. Pollen-tracking experiments in two
species showed that mobile-stamen-flowers donate pollen to many more recipients. These results demonstrate another mechanism by which plants simultaneously meter out their pollen and reduce pollen theft.
Cucurbitaceae contain c. 800 species in 130 genera and are among the economically most important families of plants. We inferred their phylogeny based on chloroplast DNA sequences from two genes, one ...intron, and two spacers (
rbcL,
matK,
trnL,
trnL-trnF,
rpl20-rps12) obtained for 171 species in 123 genera. Molecular data weakly support the traditional subfamilies Cucurbitoideae (111 genera) and Nhandiroboideae (19 genera, 60 species), and recover most of the eleven tribes, but almost none of the subtribes.
Indofevillea khasiana is sister to all other Cucurbitoideae, and the genera of Joliffieae plus a few Trichosantheae form a grade near the base of Cucurbitoideae. A newly discovered large clade consists of the ancestrally Asian genera
Nothoalsomitra,
Luffa,
Gymnopetalum,
Hodgsonia,
Trichosanthes, and the New World tribe Sicyeae. Genera that are poly- or paraphyletic include
Ampelosicyos,
Cucumis,
Ibervillea,
Neoachmandra,
Psiguria,
Trichosanthes, and
Xerosicyos. Flower characters, especially number of free styles, fusion of filaments and/or anthers, tendril type, and pollen size, exine, and aperture number correlate well with the chloroplast phylogeny, while petal and fruit characters as well as karyotype exhibit much evolutionary flexibility.
...the impact of evolutionary biology is extending further and further into biomedical research and nonbiological fields such as engineering, computer sciences, and even the criminal justice system. ...The pervasive relevance of evolution can be seen in the 2009 report commissioned by the National Research Council of the National Academies, A New Biology for the 21st Century 12, which identified four broad challenges for biology: develop better crops to feed the world, understand and sustain ecosystem function and biodiversity in a changing world, expand sustainable alternative energy sources, and understand individual health. Changes in the availability of data and an emerging scientific culture that embraces rapid, open access to many kinds of data (genomic, phenotypic, and environmental), along with a computational infrastructure that can connect these rich sources of data (19, Figure 1), will transform the nature and scale of problems that can be addressed by evolutionary biology. Aside from providing explanations for the occurrence of diseases, the field of evolutionary medicine is also concerned with suggesting strategies for slowing the evolution of resistance in pathogen populations 28-30; strategies to improve public health and reduce the incidence of common diseases 31,32; prediction of diseases that may emerge from recent host-shifts to humans 33; discovery, design, and enhancement of drugs and vaccines (e.g., 34); and understanding the role of the microbiome in human health 35.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Conservatism in climatic tolerance may limit geographic range expansion and should enhance the effects of habitat fragmentation on population subdivision. Here we study the effects of historical ...climate change, and the associated habitat fragmentation, on diversification in the mostly sub-Saharan cucurbit genus Coccinia, which has 27 species in a broad range of biota from semi-arid habitats to mist forests. Species limits were inferred from morphology, and nuclear and plastid DNA sequence data, using multiple individuals for the widespread species. Climatic tolerances were assessed from the occurrences of 1189 geo-referenced collections and WorldClim variables.
Nuclear and plastid gene trees included 35 or 65 accessions, representing up to 25 species. The data revealed four species groups, one in southern Africa, one in Central and West African rain forest, one widespread but absent from Central and West African rain forest, and one that occurs from East Africa to southern Africa. A few individuals are differently placed in the plastid and nuclear (LFY) trees or contain two ITS sequence types, indicating hybridization. A molecular clock suggests that the diversification of Coccinia began about 6.9 Ma ago, with most of the extant species diversity dating to the Pliocene. Ancestral biome reconstruction reveals six switches between semi-arid habitats, woodland, and forest, and members of several species pairs differ significantly in their tolerance of different precipitation regimes.
The most surprising findings of this study are the frequent biome shifts (in a relatively small clade) over just 6 - 7 million years and the limited diversification during and since the Pleistocene. Pleistocene climate oscillations may have been too rapid or too shallow for full reproductive barriers to develop among fragmented populations of Coccinia, which would explain the apparently still ongoing hybridization between certain species. Steeper ecological gradients in East Africa and South Africa appear to have resulted in more advanced allopatric speciation there.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Obligate mutualisms require filtering mechanisms to prevent their exploitation by opportunists, but ecological contexts and traits facilitating the evolution of such mechanisms are largely unknown.
...We investigated the evolution of filtering mechanisms in an epiphytic ant–plant symbiotic system in Fiji involving Rubiaceae and dolichoderine ants, using field experiments, metabolomics, X-ray micro-computed tomography (micro-CT) scanning and phylogenetics.
We discovered a novel plant reward consisting of sugary sap concealed in post-anthetic flowers only accessible to Philidris nagasau workers that bite through the thick epidermis. In five of the six species of Rubiaceae obligately inhabited by this ant, the nectar glands functioned for 10 d after a flower’s sexual function was over. Sugar metabolomics and field experiments showed that ant foraging tracks sucrose levels, which only drop at the onset of fruit development. Ontogenetic analyses of our focal species and their relatives revealed a 25-fold increase in nectary size and delayed fruit development in the ant-rewarding species, and Bayesian analyses of several traits showed the correlated evolution of sugar rewards and symbiosis specialization.
Concealed floral nectar forestalls exploitation by opportunists (generalist ants) and stabilizes these obligate mutualisms. Our study pinpoints the importance of partner choice mechanisms in transitions from facultative to obligate mutualisms.
Ephedra, Gnetum, and Welwitschia constitute the gymnosperm order Gnetales of still unclear phylogenetic relationships within seed plants. Here we review progress over the past 10 years in our ...understanding of their species diversity, morphology, reproductive biology, chromosome numbers, and genome sizes, highlighting the unevenness in the sampling of species even for traits that can be studied in preserved material, such as pollen morphology. We include distribution maps and original illustrations of key features, and specify which species groups or geographic areas are undersampled.
Of the c. 450 families of flowering plants, only two are left "unplaced" in the most recent APG classification of angiosperms. One of these is the Apodanthaceae, a clade of c. 19 holoparasitic ...species in two or three genera occurring in North and South America, Africa, the Near East, and Australia. Because of lateral gene transfer between Apodanthaceae and their hosts it has been difficult to infer the family's true closest relatives.
Here we report a phylogenetic analysis of 16 accessions representing six species of Apodanthaceae from the United States, Chile, Iran, and Australia, using the mitochondrial matR gene and the nuclear 18S gene. Data matrices include 190 matR sequences from up to 95 families in 39 orders of flowering plants and 197 18S sequences from 101 families representing the 16 orders of rosids. Analyses were performed at the nucleotide and at the amino acid level. Both gene trees agree with angiosperm phylogenies found in other studies using more genes. Apodanthaceae and the seven families of the order Cucurbitales form a clade with 100% bootstrap support from matR and 56% from 18 S. In addition, the Apodanthaceae and Cucurbitales matR gene sequences uniquely share two non-synonymous codon changes and one synonymous change, as well as a codon insertion, already found by Barkman et al. (2007).
Apodanthaceae belong in the Cucurbitales with which they share inferior ovaries, parietal placentation and a dioecious mating system, traits that are ancestral in Cucurbitales and which can now be interpreted as possible synapomorphies of an enlarged order Cucurbitales. The occurrence of Apodanthaceae in the Americas, Africa, the Near East, and Australia, and their adaptation to distantly related host species in the Fabaceae and Salicaceae suggest a long evolutionary history.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Insect pollination in basal angiosperms is assumed to mostly involve ‘generalized' insects looking for food, but direct observations of ANITA grade (283 species) pollinators are sparse. We present ...new data for numerous Schisandraceae, the largest ANITA family, from fieldwork, nocturnal filming, electron microscopy, barcoding and molecular clocks to infer pollinator/plant interactions over multiple years at sites throughout China to test the extent of pollinator specificity. Schisandraceae are pollinated by nocturnal gall midges that lay eggs in the flowers and whose larvae then feed on floral exudates. At least three Schisandraceae have shifted to beetle pollination. Pollination by a single midge species predominates, but one species was pollinated by different species at three locations and one by two at the same location. Based on molecular clocks, gall midges and Schisandraceae may have interacted since at least the Early Miocene. Combining these findings with a review of all published ANITA pollination data shows that ovipositing flies are the most common pollinators of living representatives of the ANITA grade. Compared to food reward-based pollination, oviposition-based systems are less wasteful of plant gametes because (i) none are eaten and (ii) female insects with herbivorous larvae reliably visit conspecific flowers.
Orchids are globally distributed, a feature often attributed to their tiny dustlike seeds. They were ancestrally terrestrial but in the Eocene expanded into tree canopies, with some lineages later ...returning to the ground, providing an evolutionarily replicated system. Because seeds are released closer to the ground in terrestrial species than in epiphytic ones, seed traits in terrestrials may have been under selective pressure to increase seed dispersal efficiency. In this study, we test the expectations that seed airspace—a trait known to increase seed flotation time in the air—is (i) larger in terrestrial lineages and (ii) has increased following secondary returns to a terrestrial habit. We quantified and scored 20 seed traits in 121 species and carried out phylogenetically informed analyses. Results strongly support both expectations, suggesting that aerodynamic traits even in dust seeds are under selection to increase dispersal ability, following shifts in average release heights correlated with changes in habit.
PDF
