We present the results of two exploratory parsimony analyses of DNA sequences from 475 and 499 species of seed plants, respectively, representing all major taxonomic groups. The data are exclusively from the chloroplast gene rbcL, which codes for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO or RuBPCase). We used two different state-transformation assumptions resulting in two sets of cladograms: (i) equal-weighting for the 499-taxon analysis; and (ii) a procedure that differentially weights transversions over transitions within characters and codon positions among characters for the 475-taxon analysis. The degree of congruence between these results and other molecular, as well as morphological, cladistic studies indicates that rbcL sequence variation contains historical evidence appropriate for phylogenetic analysis at this taxonomic level of sampling. Because the topologies presented are necessarily approximate and cannot be evaluated adequately for internal support, these results should be assessed from the perspective of their predictive value and used to direct future studies, both molecular and morphological. In both analyses, the three genera of Gnetales are placed together as the sister group of the flowering plants, and the anomalous aquatic Ceratophyllum (Ceratophyllaceae) is sister to all other flowering plants. Several major lineages identified correspond well with at least some recent taxonomic schemes for angiosperms, particularly those of Dahlgren and Thorne. The basalmost clades within the angiosperms are orders of the apparently polyphyletic subclass Magnoliidae sensu Cronquist. The most conspicuous feature of the topology is that the major division is not monocot versus dicot, but rather one correlated with general pollen type: uniaperturate versus triaperturate. The Dilleniidae and Hamamelidae are the only subclasses that are grossly polyphyletic; an examination of the latter is presented as an example of the use of these broad analyses to focus more restricted studies. A broadly circumscribed Rosidae is paraphyletic to Asteridae and Dilleniidae. Subclass Caryophyllidae is monophyletic and derived from within Rosidae in the 475-taxon analysis but is sister to a group composed of broadly delineated Asteridae and Rosidae in the 499-taxon study.

The study of islands as model systems has played an important role in the development of evolutionary and ecological theory. The 50th anniversary of MacArthur and Wilson's (December 1963) article, 'An equilibrium theory of insular zoogeography', was a recent milestone for this theme. Since 1963, island systems have provided new insights into the formation of ecological communities. Here, building on such developments, we highlight prospects for research on islands to improve our understanding of the ecology and evolution of communities in general. Throughout, we emphasise how attributes of islands combine to provide unusual research opportunities, the implications of which stretch far beyond islands. Molecular tools and increasing data acquisition now permit reassessment of some fundamental issues that interested MacArthur and Wilson. These include the formation of ecological networks, species abundance distributions, and the contribution of evolution to community assembly. We also extend our prospects to other fields of ecology and evolution -understanding ecosystem functioning, speciation and diversification -frequently employing assets of oceanic islands in inferring the geographic area within which evolution has occurred, and potential barriers to gene flow. Although island-based theory is continually being enriched, incorporating non-equilibrium dynamics is identified as a major challenge for the future.

No abstract

Heterostyly is a wide-spread floral adaptation to promote outbreeding, yet its genetic basis and evolutionary origin remain poorly understood. In Primula (primroses), heterostyly is controlled by the S-locus supergene that determines the reciprocal arrangement of reproductive organs and incompatibility between the two morphs. However, the identities of the component genes remain unknown. Here, we identify the Primula CYP734A50 gene, encoding a putative brassinosteroid-degrading enzyme, as the G locus that determines the style-length dimorphism. CYP734A50 is only present on the short-styled S-morph haplotype, it is specifically expressed in S-morph styles, and its loss or inactivation leads to long styles. The gene arose by a duplication specific to the Primulaceae lineage and shows an accelerated rate of molecular evolution. Thus, our results provide a mechanistic explanation for the Primula style-length dimorphism and begin to shed light on the evolution of the S-locus as a prime model for a complex plant supergene.DOI: http://dx.doi.org/10.7554/eLife.17956.001

Some of the most interesting but still most contentious disjunct biogeographical distributions involve Southern Hemisphere tropical and warm temperate families. The PHMV clade of Myrtales includes four families (Psiloxylaceae, Heteropyxidaceae, Myrtaceae, and Vochysiaceae) that exhibit a number of these biogeographical patterns. The related Psiloxylaceae and Heteropyxidaceae are small families restricted in distribution to the recent volcanic Mascarene Islands to the east of Madagascar and to southeast Africa, respectively. Myrtaceae are found on three major Gondwanan regions (South America, Australasia, and Africa). Because the New World taxa are almost exclusively fleshy fruited, it is unclear whether the family distribution is a classic Gondwanan vicariance pattern or results from one or more long-distance dispersal events over ocean barriers. The Vochysiaceae represent one of a handful of families with amphi-Atlantic distributions vigorously argued to support both long-distance dispersal over the Atlantic and vicariance of western Gondwanan biota by Atlantic seafloor spreading. Molecular phylogenetic relationships, fossil dating of nodes, and penalized likelihood rate smoothing of maximum likelihood trees were employed for a Myrtaleswide analysis using rbcL and ndhF and an analysis of the PHMV analysis using ndhF and matK. The results indicate that the PHMV differentiated during the late Cretaceous. The African lineage of Vochysiaceae is nested within a South American clade and probably arose via long-distance dispersal in the Oligocene at a time when the Atlantic had already rifted 80 m.yr. at the equatorial region. The African/Mascarene Island families, most closely related to Myrtaceae, differentiated during the late Eocene, with subsequent but recent longdistance dispersal from Africa to the Mascarenes. Myrtaceae show a rapid differentiation of a basal, paraphyletic subf. Leptospermoideae in Australasia. Fleshy-fruited taxa (subf. Myrtoideae) are not monophyletic. Vicariance of a widespread warm temperate Southern Hemisphere distribution is likely in explaining the South American-Australasian disjunction, with subsequent dispersal events between the two and to Africa and the Mediterranean basin.

Senna (Leguminosae) is a large, widespread genus that includes species with enantiostylous, asymmetric flowers and species with extrafloral nectaries. Clarification of phylogenetic relationships within Senna based on parsimony analyses of three chloroplast regions (rpS16, rpL16, and matK) provides new insights on the evolution of floral symmetry and extrafloral nectaries. Our results support the monophyly of only one (Psilorhegma) of the six currently recognized sections, while Chamaefistula, Peiranisia, and Senna are paraphyletic, and monotypic Astroites and Paradictyon are nested within two of the seven major clades identified by our molecular phylogeny. Two clades (I, VII) include only species with monosymmetric flowers, while the remaining clades (II-VI) contain species with asymmetric, enantiostylous flowers, in which either the gynoecium alone or, in addition, corolla and androecium variously contribute to the asymmetry. Our results further suggest that flowers were ancestrally monosymmetric with seven fertile stamens and three adaxial staminodes, switched to asymmetry later, and reverted to monosymmetry in clade VII. Fertility of all 10 stamens is a derived state, characterizing the Psilorhegma subclade. Extrafloral nectaries evolved once and constitute a synapomorphy for clades IV-VII (''EFN clade''). These nectaries may represent a key innovation in plant defense strategies that enabled Senna to undergo large-scale diversification.

Despite the remarkable species richness of the Mediterranean flora and its well-known geological history, few studies have investigated its temporal and spatial origins. Most importantly, the relative contribution of geological processes and long-distance dispersal to the composition of contemporary Mediterranean biotas remains largely unknown. We used phylogenetic analyses of sequences from six chloroplast DNA markers, Bayesian dating methods, and ancestral area reconstructions, in combination with paleogeographic, paleoclimatic, and ecological evidence, to elucidate the time frame and biogeographic events associated with the diversification of Araceae in the Mediterranean Basin. We focused on the origin of four species, Ambrosina bassii, Biarum dispar, Helicodiceros muscivorus, Arum pictum, subendemic or endemic to Corsica, Sardinia, and the Balearic Archipelago. The results support two main invasions of the Mediterranean Basin by the Araceae, one from an area connecting North America and Eurasia in the Late Cretaceous and one from the Anatolian microplate in western Asia during the Late Eocene, thus confirming the proposed heterogeneous origins of the Mediterranean flora. The subendemic Ambrosina bassii and Biarum dispar likely diverged sympatrically from their widespread Mediterranean sister clades in the Early-Middle Eocene and Early-Middle Miocene, respectively. Combined evidence corroborates a relictual origin for the endemic Helicodiceros muscivorus and Arum pictum, the former apparently representing the first documented case of vicariance driven by the initial splitting of the Hercynian belt in the Early Oligocene. A recurrent theme emerging from our analyses is that land connections and interruptions, caused by repeated cycles of marine transgressions-regressions between the Tethys and Paratethys, favored geodispersalist expansion of biotic ranges from western Asia into the western Mediterranean Basin and subsequent allopatric speciation at different points in time from the Late Eocene to the Late Oligocene.

We sequenced the trnL and rpl16 introns of the chloroplast DNA from 95 of the ca. 425 species (30 of 37 sections, seven of eight subgenera) of Primula L. in order to reconstruct the phylogenetic history of the group. Among the 24 additional taxa sampled are representatives of all genera that are likely to be embedded in Primula, as well as outgroups from the Maesaceae, Theophrastaceae, and Myrsinaceae. In the strict consensus of the most parsimonious trees, Primula and the genera embedded in it (Dionysia Fenzl., Sredinskya [Stein] Fedorov, Dodecatheon L., and Cortusa L.) are sister to a clade of several genera previously suspected to be embedded in Primula (Hottonia L., Omphalogramma [Franchet] Franch., and Soldanella L.). In recognition of this, two new rankless names are defined for these clades (/Primula and /Soldanella). Close relationships are inferred between Dionysia and Primula subgenus Sphondylia (Duby) Rupr., Sredinskya and Primula subgenus Primula, Dodecatheon and Primula subgenus Auriculastrum Schott, and Cortusa and Primula subgenus Auganthus (Link) Wendelbo. The largest subgenus, Aleuritia (Duby) Wendelbo, is dispersed among three clades that are not each other's closest relatives. Primula sections Muscarioides Balf. f., Soldanelloides Pax, Denticulata Watt, Armerina Lindley, and Aleuritia Duby are resolved as para-or polyphyletic with moderate to strong support. Throughout, we consider the striking morphological and cytological variation seen in Primula within a phylogenetic context, particularly as it relates to the close relationship implied here between Dionysia and Primula subgenus Sphondylia. The homology of involute leaf vernation in Primula is reconsidered in light of its two independent origins, and we come to the conclusion that vernation in subgenus Sphondylia is better characterized as conduplicate.