A revised evolutionary history of Poales: origins and diversification

Poales represents more than one‐third of all monocotyledons (c. 20 000 species in 16 families) and constitutes a microcosm of the angiosperms. The extreme variation in species richness among the families of Poales is still not understood: Poaceae includes ～10 000 species, whereas six families have fewer than ten species. Here, using the largest phylogenetic analysis of Poales to date, molecular dating, ancestral reconstructions and diversification analyses, we develop a macro‐evolutionary and macro‐ecological approach to seek correlates for changing diversification patterns. We show that the poalean families diverged in the Late Cretaceous, a time of high levels of CO₂ and high rainfall. Our habitat reconstructions indicate that Poales inhabited open and dry habitats in this environment. We also demonstrate that lineages with CO₂‐concentrating mechanisms inhabiting dry and open environments exhibited higher diversification rates than C₃, shade and wet lineages. CO₂‐concentrating mechanisms counteract the effects of low atmospheric CO₂ and reduce phototranspiration. It is believed that the parallel evolution of C₄ and CAM (Crassulacean acid metabolism) photosynthesis in Poaceae, Cyperaceae and Bromeliaceae is an adaptation to changes in atmospheric CO₂ concentrations. Combinations of extrinsic and intrinsic factors might have played a role in shifts in diversification rates and may explain the variation in species richness in Poales. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 4–16.     

The occurrence of Fosliella limitata (Foslie) Ganesan (a new British record) and F. lejolisii (Rosanoff) Howe (Rhodophyta,Corallinaceae) on the Isle of Wight

The occurrence of Fosliella limitata and F. lejolisii at Bembridge, Isle of Wight is reported. F. limitata is newly recorded for Britain whilst F. lejolisii has been found only rarely since disease struck Zostera in the early 1930s. The two epiphytes both grow on Zostera; F. limitata also grows on large brown and red algae. Their vegetative and reproductive structures are described and illustrated and information given regarding their seasonal occurrence from May 1975 to April 1976. Previous records of both species are discussed and a table is given summarizing the differences between the species.     

Chronology of the Neolithic Necropolis at Camí de Can Grau (NE-Iberian Peninsula). Funerary pattern changes and long-distance raw material exchanges

Camí de Can Grau is one of the most important Neolithic necropolises of the “Pit Burials” horizon (North-East of the Iberian Peninsula. Late fifth–early fourth millennia cal BC), because of its large number of graves. However, the number of buried individuals and the type of grave goods of the site have some peculiarities suggesting that could be one of the last manifestations of this horizon. For proving that, a radiocarbon dating programme and some statistical analysis were carried out so as to determine its chronology. The results are discussed regarding the duration of the necropolis, the degree of contemporaneity between graves and grave goods and the number of buried individuals. Moreover, chronological relationships with other similar contexts of the same horizon and located in other regions are presented. This study goes beyond a purely local research, as it proposes a method for addressing the chronology of funerary contexts.     

Pattern and timing of evolutionary divergences among hominoids based on analyses of complete mtDNAs

We have examined and dated primate divergences by applying a newly established molecular/paleontological reference, the evolutionary separation between artiodactyls and cetaceans anchored at 60 million years before present (MYBP). Owing to the morphological transformations coinciding with the transition from terrestrial to aquatic (marine) life and the large body size of the animals (which makes their fossils easier to find), this reference can be defined, paleontologically, within much narrower time limits compared to any local primate calibration marker hitherto applied for dating hominoid divergences. Application of the artiodactyl/cetacean reference (A/C-60) suggests that hominoid divergences took place much earlier than has been concluded previously. According to a homogenous-rate model of sequence evolution, the primary hominoid divergence, i.e., that between the families Hylobatidae (gibbons) and Hominidae, was dated at 36 MYBP. The corresponding dating for the divergence betweenPongo (orangutan) andGorilla-Pan (chimpanzee)-Homo is 24.5 MYBP, that forGorilla vsHomo-Pan is 18 MYBP, and that forHomo vsPan 13.5 MYBP. The split between Sumatran and Bornean orangutans was dated at 10.5 MYBP and that between the common and pygmy chimpanzees at 7 MYBP. Analyses of a single gene (cytochromeb) suggest that the divergence within the Catarrhini, i.e., between Hominoidea and Old World monkeys (Cercopithecoidea), took place >40 MYBP; that within the Anthropoidea, i.e., between Catarrhini and Platyrrhini (New World monkeys), >60 MYBP; and that between Anthropoidea and Prosimii (lemur), 80 MYBP. These separation times are about two times more ancient than those applied previously as references for the dating of hominoid divergences. The present findings automatically imply a much slower evolution in hominoid DNA (both mitochondrial and nuclear) than commonly recognized.     

The “Phoca standard”: An external molecular reference for calibrating recent evolutionary divergences

Comparison of the complete mitochondrial DNA (mtDNA) of the high-Arctic ringed seal (Phoca hispida) and the sub-Arctic harbour (P. vitulina) and grey (Halichoerus grypus) seals shows that they are genetically equidistant from one another. We relate the evolutionary divergence of the three species to expanding glaciation in the Arctic Basin and establish, in conjunction with mtDNA data, a standard reference for calibration of recent divergence events among mammalian taxa. In the present study, we apply the “Phoca standard” to the dating of divergences within the hominid phylogenetic tree. After determining the relative rates of substitution over all mitochondrial protein-coding genes in the different evolutionary lineages, we estimate that humans and chimpanzees diverged from each other 6.1 Mya (95% confidence limits: 5.2–6.9 Mya). The corresponding lower-limit divergence between common chimpanzee,Pan troglodytes, and pygmy chimpanzee,P. paniscus, occurred 3 (2.4–3.6) Mya, and the primary split within theP. troglodytes complex 1.6 (1.3–2.0) Mya. The analyses suggest that the split betweenGorilla andPan/Homo occurred 8.4 (7.3–9.4) Mya. They also suggest thatPongo (orangutan) and the lineage leading to gorillas, chimpanzees, and humans diverged 18.1 (16.5–19.6) Mya. The present analysis is independent of the hominid paleontological record and inferential morphological interpretations and thus is a novel approach to the lower-limit dating of recent divergences. Correspondence to: U. Arnason