A new family and a new genus for two taxa previously assigned to Apodachlyella completa (J. E. Humphrey) H. Indoh (Peronosporomycetidae: Leptomitales)

DICK, M. VV., 1986. A new family and a new genus for two taxa previously assigned to Apodachlyella completa (J. E. Humphrey) H. Indoh (Peronosporomycetidae: Leptomitales) . At present two distinct taxa are referrable to Apodachlyella completa. New genus and species names (I'lerogone helodes M. W. Dick genus & sp. nov.) are necessary for the taxon reported from the British Isles. Confirmation of the unique wall membranes in the antheridia and oogonia is used to justify the placement of A. completa in a new, monotypic family of the Leptomitales (Apodachlyellaceae M. W. Dick fam. nova). Plerogone is placed provisionally in the Leptomitaceae.     

Shape analysis of two sympatric coral species: Implications for taxonomy and evolution

Fourier shape analysis of Pleurodictyum americanum and P. dividua , favositid tabulate corals, from the Middle Devonian Hamilton Group of New York State, indicates that colony growth form is variable within species between environments, but that the range of variability in growth form is static through time. Pleurpdictyum dividua displays a columnar morphotype; however, P. dividua and P. americanum cannot be discriminated from one another based on colony shape alone. A major prediction of the punctuated equilibrium model of evolution is morphological stasis throughout the duration of a species. Harmonic means of assemblages of P. americanum show no persistent temporal trends. The range of harmonic means present among the oldest assemblages (Centerfield Limestone) are comparable to those among the youngest assemblages (Windom Shale) and to those in the intervening intervals. Character stasis in colony growth form lasted throughout a 2.5-3.5 my interval. In tabulate corals, where reproductive modes such as fragmentation have not been demonstrated, growth form may be useful in interpreting ancient environments. In addition, the tempo of evolution of growth form can be analyzed when sufficient morphological data are available from a wide distribution of environments. Thus, Fourier shape analysis of growth form provides a powerful tool for paleontologists to interpret the ecology and evolution of colonial marine animals.     

Adverse effects of agricultural intensification and climate change on breeding habitat quality of Black‐tailed Godwits Limosa l. limosa in the Netherlands

Agricultural intensification is one of the main drivers of farmland bird declines, but effects on birds may be confounded with those of climate change. Here we examine the effects of intensification and climate change on a grassland breeding wader, the Black‐tailed Godwit Limosa l. limosa, in the Netherlands. Population decline has been linked to poor chick survival which, in turn, has been linked to available foraging habitat. Foraging habitat of the nidifugous chicks consists of uncut grasslands that provide cover and arthropod prey. Conservation measures such as agri‐environment schemes aim to increase the availability of chick foraging habitat but have not yet been successful in halting the decline. Field observations show that since the early 1980s, farmers advanced their first seasonal mowing or grazing date by 15 days, whereas Godwits did not advance their hatching date. Ringing data indicate that between 1945 and 1975 hatching dates advanced by about 2 weeks in parallel with the advancement of median mowing dates. Surprisingly, temperature sums at median mowing and hatching dates suggest that while the agricultural advancement before 1980 was largely due to agricultural intensification, after 1980 it was largely due to climate change. Examining arthropod abundance in a range of differently managed grasslands revealed that chick food abundance was little affected but that food accessibility in intensively used tall swards may be problematic for chicks. Our results suggest that, compared with 25 years ago, nowadays (1) a much higher proportion of clutches and chicks are exposed to agricultural activities, (2) there is little foraging habitat left when chicks hatch and (3) because of climate change, the vegetation in the remaining foraging habitat is taller and denser and therefore of lower quality. This indicates that for agri‐environment schemes to make a difference, they should not only be implemented in a larger percentage of the breeding area than the current maxima of 20–30% but they should also include measures that create more open, accessible swards.     

A Mechanistic Model of Carbohydrate Dynamics During Adventitious Root Development in Leafy Cuttings

The rooting of vegetatively propagated leafy cuttings involvesthe complex interaction of many processes. For this reason,the influence of carbohydrate status, nutrition, water and hormonalfactors on root formation is poorly understood at a mechanisticlevel. We present a mechanistic model of the growth of pre-formedroot initials on a cutting consisting of leaf, internode androots. The processes represented are leaf photosynthesis, starchmobilization, sugar transport, and sugar utilization for rootgrowth. The model provides a quantitative scheme for understandinghow root development depends on properties of cuttings suchas leaf area, internode length and initial carbohydrate content.The potential of the model to interpret rooting experimentson a whole-cutting basis is illustrated using published datafor cuttings of Triplochiton scleroxylon (a West African hardwood)with different leaf areas. Observed rooting times are reproducedin the model by varying the leaf photosynthetic rate per unitarea. The simulated starch and sugar dynamics during root growthare in qualitative agreement with observations. A sensitivityanalysis is performed to examine the effect of key parameterson the timing or success of rooting. The model provides a frameworkfor examining the role of other factors known to affect rooting,such as nutrient and water status, but requires further parameterisationbefore it can be used as a predictive tool in vegetative propagation. Model, carbohydrates, rooting, vegetative propagation