Biogeography of the grasses (Poaceae): a phylogenetic approach to reveal evolutionary history in geographical space and geological time

The grasses (Poaceae) are the fifth most diverse family of angiosperms, including 800 genera and more than 10 000 species. Few phylogenetic studies have tried to investigate palaeo‐biogeographical and palaeo‐ecological scenarios that may have led to present‐day distribution and diversity of grasses at the family level. We produced a dated phylogenetic tree based on combined plastid DNA sequences and a comprehensive sample of Poaceae. Furthermore, we produced an additional tree using a supermatrix of morphological and molecular data that included all 800 grass genera so that ancestral biogeography and ecological habitats could be inferred. We used a likelihood‐based method, which allows the estimation of ancestral polymorphism in both biogeographical and ecological analyses for large data sets. The origin of Poaceae was retrieved as African and shade adapted. The crown node of the BEP + PACCMAD clade was dated at 57 Mya, in the early Eocene. Grasses dispersed to all continents by approximately 60 million years after their Gondwanan origin in the late Cretaceous. PACCMAD taxa adapted to open habitats as early as the late Eocene, a date consistent with recent phytolith fossil data for North America. C₄ photosynthesis first originated in Africa, at least for Chloridoideae in the Eocene at c. 30 Mya. The BEP clade members adapted to open habitats later than PACCMAD members; this was inferred to occur in Eurasia in the Oligocene. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162 , 543–557.     

The response of Chironomidae to sediment pollution and other environmental characteristics in urban wetlands

1. We investigated the distribution of chironomid taxa in urban wetlands in the greater Melbourne area, Australia, to test if their distribution was influenced by sediment pollution and other environmental variables. 2. For identification of the Chironomidae, DNA markers generated via polymerase chain reaction–restriction fragment length polymorphism of cytochrome c oxidase sub unit I (COI) were validated against morphology and reference specimens for more than 5000 chironomids representing over 80 species. DNA‐based identification generally concurred with morphological separation, but also indicated the existence of cryptic diversity in some genera. 3. Non‐metric multidimensional scaling (NMS) and canonical correspondence analysis (CCA) showed chironomid assemblages were structured among wetlands and could be linked to several habitat characteristics. However, Chironomidae assemblages were only weakly linked to sediment pollution. 4. Logistic regressions identified potential bioindicators of sediment pollution. Riethia stictoptera, Tanytarsus inextentus, Coelopynia and Chironomus ‘februarius’ were negatively associated and Chironomus duplex was positively associated with sediment pollution. Thresholds for the pollution sensitivities of specific species were mostly similar to those established with previous microcosm tests. 5. Several other environmental factors influenced the distribution of specific chironomid taxa. Salinity, substratum type and submerged and riparian vegetation were particularly important. 6. We conclude that specific chironomid taxa rather than assemblages have potential as bioindicators of sediment pollution provided their ecological preferences are considered and their pollution sensitivities are characterized using multiple methods. The integration of DNA‐based techniques should facilitate accurate and rapid identification of bioindicators species.     

Breeding biology of the Red Kite Milvus milvus in Corsica

The breeding biology of the Red Kite Milvus milvus is still little known in the southern part of its range (Mediterranean), despite recent conservation concerns and major declines in most insular populations (Sicily, Sardinia and Balearics). We report here on the breeding biology of the Red Kite in Corsica in 1996–99 and on recent population trends there. In a 42‐km² study area located in the northwest of the island (Balagne region), breeding density was locally high (1.17–1.78 breeding pairs/km²). Breeding dispersion ranged from loosely colonial to dispersed, with average nearest‐neighbour distance of 444 ± 316 m (range 50–2000) (all data as means ± sd). Kites established breeding territories in January–February, and 92.4% of territorial pairs laid a clutch (n = 238). Laying took place between February and May (mean lay date: 27 March ± 16 days, n = 147). Clutch size averaged 2.44 ± 0.71 (1–5 eggs, n = 96), hatching success 66.9% and fledging success 78.6%. Productivity averaged 1.33 ± 0.88 young per breeding attempt (n = 221) and 1.65 ± 0.65 young per successful breeding attempt (n = 173). Overall breeding success was 51.4 ± 38.0% (n = 88). We describe the growth of young (wing, weight, tarsus and bill) and show a marked seasonal decline in clutch size and breeding performance, with pairs laying earlier producing larger clutches and being more successful than later breeding pairs. Unlike most other insular Mediterranean Red Kite populations that have recently declined, the breeding population in the northwest of Corsica, which accounts for c. 25% of the whole island population, increased from 25 to 35 pairs in 1989 to a maximum of 80–90 pairs in 1997. This increase was probably related to the lack of persecution and a local increase in abundance of Rabbits Oryctolagus cuniculus, following their introduction in the late 1970s, which provided an important feeding resource for Kites. Finally, we compare our results with those from other Red Kite populations studied in Europe. We found that there is a latitudinal gradient in laying date and productivity across Western Europe populations, but no evidence of an insular syndrome in the Corsican population.     

Evidence of recent and continuous speciation in a biodiversity hotspot: a population genetic approach in southern African gladioli (Gladiolus; Iridaceae)

There has been much debate over the origin of species diversity in biodiversity hotspots, particularly the rate of speciation over extinction and the geographic mode of speciation. Here, we looked at speciation with varying degrees of sympatry in a biodiversity hotspot, focusing on a distinct morphological clade in the Cape Floristic Region in southern Africa, the Gladiolus carinatus species complex (Iridaceae). We investigate the mechanisms involved in population and species differentiation through a combination of ecological and genomic approaches. We estimated spatial and phenological overlap, differences in floral morphology, genetic isolation and genomic selection. A genetic coalescent analysis estimated that the time of divergence between lineages followed the establishment of available habitat in the Cape littoral plain where these species currently overlap geographically. Marked shifts in flowering time and morphology, which act as barriers to gene flow, have developed to varying degrees over the last 0.3–1.4 million years. An amplified fragment length polymorphism genome scan revealed signatures of divergent and balancing selection, although half of the loci consistently behaved neutrally. Divergent species outliers (1%) and floral morph outliers (3%) represent a small proportion of the genome, but these loci produced clear genetic clusters of species and significant associations with floral traits. These results indicate that the G. carinatus complex represents a continuum of recent speciation. We provide further evidence for ecological adaptation in the face of gene flow.     

A new genus of pliosaur (Reptilia: Sauropterygia) from the Lower Jurassic of Holzmaden,Germany

Abstract: The exquisitely preserved holotype of the pliosaur ‘Rhomaleosaurus’victor (SMNS 12478) is described from the Toarcian Posidonien‐Schiefer (Upper Lias, Lower Jurassic) of Holzmaden (Baden‐Württemberg), Germany. The specimen presents a novel combination of synapomorphies and unique morphometric proportions separating it from Rhomaleosaurus sensu stricto and warranting the erection of a new genus, Meyerasaurus gen. nov. Historically, the name ‘Thaumatosaurus’ has been interchangeable with Rhomaleosaurus and is frequently associated with SMNS 12478 in the literature. However, this is an invalid taxon and cannot be reinstated. The anatomy of Meyerasaurus victor is compared in detail with other pliosaurs, and its taxonomic affinity is reviewed. M. victor belongs to the family Rhomaleosauridae and shares several anatomical characters with Rhomaleosaurus including a short and robust premaxillary rostrum (length‐to‐width ratio c. 1.0), parallel premaxilla–maxilla sutures anterior to the nares, vomers contacting the maxillae posterior to the internal nares, and c. 28 cervical vertebrae minus the atlas–axis. The known geographical distribution of Rhomaleosaurus, which previously extended across the German and English palaeobiogeographical zones, is reduced to the English zone as a consequence of the referral of SMNS 12478 to a new genus. This is significant because it contributes to an ongoing trend of increasing generic separation between the German and English zones, while increasing the generic diversity within the German zone itself.