Pollen tube growth and the pollen‐tube pathway of Nymphaea odorata (Nymphaeaceae)

An important aspect of the evolution of carpel closure, or angiospermy, is the relationship between pollen tube growth patterns and internalization of the pollen‐tube pathway. True carpel closure, involving postgenital fusion of inner carpel margins, is inferred to have arisen once within the ancient order Nymphaeales, in the common ancestor of Nymphaeaceae. We studied pollen tube development, from pollination to fertilization, in a natural population of Nymphaea odorata, using hand pollinations and timed flower collections. Pollen germinates in stigmatic secretions within 15 min and pollen tubes enter subdermal transmitting tissue within an hour, following wide intercellular spaces towards the zone of postgenital fusion. At the zone of fusion they turn downwards to grow in narrow spaces between interlocked cells and then wander freely to ovules within ovarian secretions. The pollen‐tube pathway is 2–6 mm long and upper ovules are first penetrated 2.5 h after pollination. Pollen tubes grow at rates of approximately 1 mm/h whether in stigmatic fluid, transmitting tissues or ovarian secretions. Pollen‐tube pathways are structurally diverse across Nymphaeales, yet their pollen tubes have similar morphologies and rapid growth rates. This pattern suggests pollen tube growth innovations preceded and were essential for the evolution of complete carpel closure. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162 , 581–593.     

Two new species of Dunkleosteus Lehman, 1956, from the Ohio Shale Formation (USA,Famennian) and the Kettle Point Formation (Canada,Upper Devonian), and a cladistic analysis of the Eubrachythoraci (Placodermi,Arthrodira)

Two pachyosteomorph arthrodires are described from the Upper Devonian of North America, Dunkleosteus raveri sp. nov. and Dunkleosteus amblyodoratus sp. nov. (from the Appalachian and the Michigan basins, respectively). Dunkleosteus raveri sp. nov. is found stratigraphically below the only other species within the Ohio Shale Formation (Famennian), and is characterized by the retention of a primitive dermal ornamentation, and shares with Dunkleosteus terrelli ( Newberry, 1873 ) the possession of articular facets on the parasphenoid. Dunkleosteus amblyodoratus sp. nov. (Kettle Point Formation, Upper Devonian), known only from incomplete nuchal, paranuchal, and parasphenoid plates, also retains dermal tuberculation, and is characterized by tapering articular facets on the parasphenoid. The current study reviews three North American species of Dunkleosteus (Du. terrelli, Du. raveri sp. nov. , and Du. amblyodoratus sp. nov. ). Formerly, two subgroups were recognized within the Dinichthyidae, the terrelli and herzeri groups, which are shown here to be members of distinct clades. Dinichthys herzeri Newberry, 1868 (the namesake member of the herzeri group) is now the sole member of the family Dinichthyidae comb. nov. , and is assigned to the Aspinothoracidi sensu Miles & Dennis, 1979 . Heintzichthys Whitley, 1933 and Gorgonichthys Claypole, 1892 (additional members of the herzeri group) were previously placed among the aspinothoracid arthrodires. Likewise, Holdenius holdeni Dunkle & Bungart, 1942 (the final member of the herzeri group) and Hadrosteus rapax Gross, 1932 are now placed within the Aspinothoracidi. The remaining taxa, formerly assigned to the Dinichthyidae (i.e. Dunkleosteus Lehman, 1956 ; Eastmanosteus Obruchev, 1964 ; Golshanichthys Lelièvre, Janvier, & Goujet, 1981 ; and Westralichthys Long, 1987 ), are united within the Dunkleosteidae Stensiö, 1963 . © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 159 , 195–222.     

Inter‐regional comparison of land‐use effects on stream metabolism

1. Rates of whole‐system metabolism (production and respiration) are fundamental indicators of ecosystem structure and function. Although first‐order, proximal controls are well understood, assessments of the interactions between proximal controls and distal controls, such as land use and geographic region, are lacking. Thus, the influence of land use on stream metabolism across geographic regions is unknown. Further, there is limited understanding of how land use may alter variability in ecosystem metabolism across regions. 2. Stream metabolism was measured in nine streams in each of eight regions (n = 72) across the United States and Puerto Rico. In each region, three streams were selected from a range of three land uses: agriculturally influenced, urban‐influenced, and reference streams. Stream metabolism was estimated from diel changes in dissolved oxygen concentrations in each stream reach with correction for reaeration and groundwater input. 3. Gross primary production (GPP) was highest in regions with little riparian vegetation (sagebrush steppe in Wyoming, desert shrub in Arizona/New Mexico) and lowest in forested regions (North Carolina, Oregon). In contrast, ecosystem respiration (ER) varied both within and among regions. Reference streams had significantly lower rates of GPP than urban or agriculturally influenced streams. 4. GPP was positively correlated with photosynthetically active radiation and autotrophic biomass. Multiple regression models compared using Akaike’s information criterion (AIC) indicated GPP increased with water column ammonium and the fraction of the catchment in urban and reference land‐use categories. Multiple regression models also identified velocity, temperature, nitrate, ammonium, dissolved organic carbon, GPP, coarse benthic organic matter, fine benthic organic matter and the fraction of all land‐use categories in the catchment as regulators of ER. 5. Structural equation modelling indicated significant distal as well as proximal control pathways including a direct effect of land‐use on GPP as well as SRP, DIN, and PAR effects on GPP; GPP effects on autotrophic biomass, organic matter, and ER; and organic matter effects on ER. 6. Overall, consideration of the data separated by land‐use categories showed reduced inter‐regional variability in rates of metabolism, indicating that the influence of agricultural and urban land use can obscure regional differences in stream metabolism.     

Relationships between Bulb Size, Apex Size and Flowering in Bulbous Iris cv. Ideal

Large, retarded bulbs of the Iris cv. Ideal flower readily after exposure to appropriate preplanting conditions, whereas smaller bulbs flower with decreased frequency. Flower initiation occurs when apices from large, retarded bulbs are cultured on either Murashige-Skoog medium supplemented with gibberellic acid, or on the same medium without gibberellic acid on which scales from large bulbs have been incubated. Since floral initiation seldom occurs in explants from small bulbs, it is likely that reduced flowering of small bulbs relates in part to characteristics of the apical meristem. Apical dome diameter is one characteristic of retarded (and freshly dug) bulbs that is positively correlated with bulb size. However, whereas prolonged storage at retarding temperature increases the frequency of flowering of smaller bulbs, there is not a concomitant increase in apical dome diameter. Moreover, the ratio of apical dome diameter to bulb size in freshly dug bulbs does not increase measurably with later digging date indicating that apical dome size is not correlated with bulb maturity.     

Genetic variation and reproductive mode in populations of Simocephalus vetulus (Branchiopoda: Cladocera) from the East Midlands of England

SUMMARY. 1. Five populations of the cladoceran Simocephalus vetulus (O. F. Muller) examined by enzyme electrophoresis at four to five loci revealed high levels of genetic variation.
2. The one intermittent population had genotype frequencies in Hardy Weinberg equilibrium, the three permanent populations showed deviations from equilibrium of varying magnitude. The fifth population was fixed for a single clone, and was possibly recently derived from a single ephippial hatchling.
3. Laboratory breeding experiments confirmed that this species is a cyclic parthenogen.     

Systematic status of the Black-collared Bulbul Neolestes torquatus

The Afrotropical monotypic genus Neolestes has been treated variously as a bulbul (Pycnonotidae) or a 'shrike' (Malaconotidae, Laniidae or Prionopidae). Recent field observations and fresh laboratory material have enabled a multi-disciplinary review incorporating biology, anatomy and DNA. The DNA analysis suggests that N. torquatus represents a deep branch of the pycnonotid clade. The plumage of Neolestes is unlike that of any bulbul, although the juvenile plumage is more bulbul-like than shrike-like. Evidence from the syrinx, skull, humerus and carpometatarsus eliminates a relationship between Neolestes and the shrikes and mainly points to one with the Pycnonotidae. Neolestes could be the primitive sister-group of the Pycnonotidae, or a member of some larger group of which the bulbuls are but one manifestation. The vocalizations are not shrike-like but are reminiscent of those of the African species of Pycnonotus ; other aspects of its behaviour point in this direction. We believe there is no evidence for considering Neolestes to be a 'shrike', and recommend treating it as a primitive member of the Pycnonotidae, although as incertae sedis.     

Distribution and behaviour of passerines around Peregrine Falco peregrinus eyries in western Greenland

This paper describes the distribution and behaviour of passerine birds within 1 km of Peregrine Falcon Falco peregrinus eyries in western Greenland. Passerine populations were censused in 1983 around six cliffs occupied by nesting Peregrines and at six sites on the open tundra, and in 1984 at two unoccupied sites suitable for Peregrine nesting.
Four passerine species accounted for over 90% of birds seen. Within 400 m of Peregrine occupied cliffs, three species, Lapland Longspur Calcarius lapponicus . Northern Wheatear Oenanthe oenanthe , and Common Redpoll Carduelisflammea , were found in lower than average abundance while the fourth, Snow Bunting Plectrophenax nivalis , was found in increased abundance. Our indirect tests suggest that Peregrine presence, rather than direct predation, was responsible for the distributions of the first three species. The Snow Bunting, however, behaviourally adapts to Peregrine presence in order to exploit nesting habitat available at the cliff base.
These results contrast strongly with those reported by other Arctic workers, where increased abundances of potential prey were observed in close proximity to nesting Peregrines.