Estimating the population size of specialised solitary bees

Abstract.  1. Reliable methods for quantifying population size are crucial for strategies to conserve endangered wild-bee species. Estimates of population size obtained through survey walks were compared with estimates obtained through mark–recapture studies in 10 populations of the red-listed solitary bee Andrena hattorfiana in southern Sweden.
2. The mean number of bees observed during survey walks was strongly correlated with estimates of population size obtained with mark–recapture. It was found that 5.5–23.4% (mean 13.4%) of the total population was observed during an average survey walk.
3. One component in mark–recapture analysis is the measure of survival of individuals. In the largest bee population, females of A. hattorfiana that emerged in early season were found to forage for pollen on average 18.4 days.
4. The findings suggest that during large-scale surveys, for example re-inventories for red-listed species, the population size of solitary bees can be quantified reliably and effectively by performing survey walks in a two-step process. The first step consists of survey walks to establish the relationship between number of bee observations per survey walk and mark–recapture population size for a small set of populations. In the second, simple observation survey walks can be performed for a large set of populations. In each population of A. hattorfiana , it is recommended that at least six survey walks are performed.     

Evidence for ecological speciation in the sister species Candidula unifasciata (Poiret, 1801) and C. rugosiuscula (Michaud, 1831) (Helicellinae, Gastropoda)

This paper studies the speciation of two land snail species in south-east France. By using two mitochondrial and one nuclear gene, the species are shown to be sister species within the larger clade of western European Candidula species. The species never occurred syntopically, but a narrow contact zone population was identified. Recent range expansions inferred from phylogeographical methods indicated that the present day distributions are not limited by the colonization capacity of the species. Analysis of environmental variables suggested distribution along an ecotone. The gastropod community is also correlated to this gradient. Morphometric shell analysis showed that the divergence between the sister species is a result of desiccation-resistant shell characters. We therefore conclude that the cause for the ecological speciation is most probably the establishment of the Mediterranean climate ≈ 3.2 mya. A model of ecological speciation with a moving ecotone is put forward.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79, 611–628.     

Male copulation frequency and female competition for fertilizations in a promiscuous brood parasite, the Pin-tailed Whydah Vidua macroura

Male Pin-tailed Whydahs Vidua macroura copulate infrequently and terminate most courtship displays, even when females are highly receptive. Female sexual interference is aimed at preventing other females from copulating, and is nearly always successful.     

White-Headed Woodpecker Nesting Ecology After Wildfire

ABSTRACT Within forests susceptible to wildfire and insect infestations, land managers need to balance dead tree removal and habitat requirements for wildlife species associated with snags. We used Mahalanobis distance methods to develop predictive models of white-headed woodpecker (Picoides albolarvatus) nesting habitat in postfire ponderosa pine (Pinus ponderosa)-dominated landscapes on the Fremont-Winema National Forests in south central Oregon, USA. The 1-km radius (314 ha) surrounding 45 nest sites was open-canopied before fire and a mosaic of burn severities after wildfire. The 1-ha surrounding nests of white-headed woodpeckers had fewer live trees per hectare and more decayed and larger diameter snags than at non-nest sites. The leading cause of nest failure seemed to be predation. Habitat and abiotic features were not associated with nest survival. High daily survival rates and little variation within habitat features among nest locations suggest white-headed woodpeckers were consistently selecting high suitability habitats. Management activities that open the forest canopy and create conditions conducive to a mosaic burn pattern will probably provide suitable white-headed woodpecker nesting habitat after wildfire. When making postfire salvage logging decisions, we suggest that retention of larger, more decayed snags will provide nesting habitat in recently burned forests.     

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.     

Can higher‐level phylogenies of weevils explain their evolutionary success? A critical review

We review a series of related publications that combine higher‐level phylogenies of weevils (Coleoptera: Curculionoidea) with host plant information to explain the success of this megadiverse lineage in the context of a co‐evolutionary escape‐and‐radiation hypothesis. We argue that the authors' approach is marred by the cumulative effect of: (1) inadequate taxon sampling, particularly within the most diverse family Curculionidae; (2) insufficient reconciliation of systematic evidence, including the reassessment of morphological characters and necessary classificatory emendations; (3) exceedingly wide concepts of ecological similarity, leading to uninformative tests of adaptation; (4) insufficient resolution of the temporal sequence of associated weevil and angiosperm radiations; and (5) inadequate consideration of alternatives to the escape‐and‐radiation hypothesis. As a result, there are very few new and reliable inferences about the evolutionary success of weevils that depend precisely on the phylogenetic data presented in these studies. Improved taxon sampling alone is not the solution, because the existing mid‐level classification of weevils is too deficient to permit inferences about natural lineages and their ancestral traits. We therefore recommend abandoning such an approach in favour of more narrowly focused reconstructions of the evolutionary history of generic and tribal groupings.     

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.