Analysing the history of the derelomine flower weevil–Carludovica association (Coleoptera: Curculionidae; Cyclanthaceae)

The evolutionary history of the interaction among species of derelomine flower weevils (Coleoptera: Curculionidae: Derelomini) and the Panama-hat palm Carludovica (Cyclanthaceae) is analysed with emphasis on the congruence of (1) topologies and (2) character state transformations in each of the Neotropical clades. For this purpose cladistic analyses are complemented with host plant records, natural history information and selected morphological studies of the associated taxa. The interaction is specialized, involving pollination, oviposition into the inflorescences and the predation of seeds (particularly within Systenotelus ). As results from a range of standard coevolutionary methods of analysis indicate, however, events of colonization, extinction and independent (non-reciprocal) speciation have been abundant throughout the history of the association. At the same time it is possible to specify the homology and succession of characters among species of derelomines and Carludovica and interpret them as reciprocal adaptations to attack and protect the seeds, respectively. It is argued that – in light of the limited evolutionary stability of many insect–plant interactions – the question of coevolution is most effectively addressed by combining information from the character- and topology-based approaches.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 483–517.     

Dynamics of the lacustrine fauna from the Early Cretaceous Yixian Formation,China: implications of volcanic and climatic factors

Pan, Y., Sha, J., Fürsich, F.T., Wang, Y., Zhang, X. & Yao, X. 2011: Dynamics of the lacustrine fauna from the Early Cretaceous Yixian Formation, China: implications of volcanic and climatic factors. Lethaia, Vol. 45, pp. 299–314. The taphonomy and palaeoecology of the famous Lower Cretaceous Jehol biota of northeastern China are two of its least resolved aspects. The biota occurs in lacustrine sediments characterized by abundant volcanic ash layers. The general view is that these tuff layers correlate strongly with vertebrate mass mortality events. However, though aquatic invertebrates also suffered mass mortality, in the majority of cases individuals tend to occur on bedding planes of finely laminated sediments, suggesting that each mass mortality event is not related to volcanic activity. Based on data collected in the course of two excavations at Zhangjiagou and Erdaougou, the role of volcanic activity and other factors that could have controlled the dynamics of the fauna were investigated. Cluster analyses of fossil assemblages from both localities show similar results, and eight fossil communities are recognized. In the lacustrine Yixian Formation, frequent and often severe volcanic activity represented by the abundant tuff layers influenced the water quality, causing repeated collapse of the aquatic ecosystem. Bedding planes with remains of the eight different communities were analysed, each recording the community dynamics of a shallow eutrophic lake system that was most probably controlled by fluctuations of oxygen level related to climate. A mortality model, in which oxygen‐level fluctuations play the decisive role, is proposed to explain the existence and distribution of the fossil communities, as well as the unfossiliferous layers. □China, Jehol biota, lacustrine community, mass mortality, palaeoclimate, volcanic activity.     

Newly Isolated Friend Cell Lines are Blocked at the Same Stage of Erythroid Differentiation as Established Clones

Friend erythroleukemia cells, a widely used in vitro model of murine erythropoiesis, express prior to induction, a state of erythroid differentiation similar to that of the early erythroblast in vivo. To investigate whether this uniform and stable epigenetic state was the result of a selection in long-term culture for the corresponding cell type, 29 new cell lines were isolated from the hemopoietic organs of DBA/2 mice infected with Friend virus and were analyzed without delay for the expression of several erythroid traits. All the lines examined displayed levels of expression of the markers indistinguishable from those displayed by established Friend cell clones. Thus, newly isolated Friend cell lines appear to be blocked at essentially the same stage of erythroid differentiation as established clones. This indicates that the expression of several characteristic erythroid markers is remarkably stable in vitro and does not result from long-term selection. In contrast, the capacity of these cells to respond to chemical inducers varies considerably from clone to clone and with, time in culture.