Seasonal mortality trends in tree‐feeding insects: a field experiment

Abstract 1. The majority of general life‐history models treat the environment as being invariable through time, even though temporal variation in selective agents could dramatically change the outcomes, e.g. in terms of optimal size and time at maturity. For herbivorous insects, seasonal differences in food quality are reasonably well described, but seasonal dynamics of top‐down selective forces are poorly documented. 2. The present study attempted to quantify seasonal changes in predation risk of folivorous insect larvae in temperate forest habitats. In a series of field experiments, artificial larvae were exposed to predators, and the resulting bird‐inflicted damage was recorded. The trials were repeated regularly throughout the course of two summers. 3. A distinct peak of larval mortality was recorded in mid‐June (the nestling period for most insectivorous passerine birds), after which predation risk declined to a plateau of 20–30% below the peak value. 4. The recorded pattern is interpreted as a consequence of seasonal changes in the number and behaviour of insectivorous birds, and the abundance of alternative food resources for these predators. 5. A quantitative analysis based on field data indicated that considering temporal variation in mortality in life‐history models is crucial for obtaining realistic predictions concerning central life‐history traits, such as final body size in different generations.     

A molecular analysis of the Gelechiidae (Lepidoptera,Gelechioidea) with an interpretative grouping of its taxa

We re‐examine the higher level phylogeny and evolutionary affinities of the family Gelechiidae (Lepidoptera: Gelechioidea) based on DNA sequence data for one mitochondrial gene (cytochrome c oxidase subunit I) and seven nuclear genes (Elongation Factor‐1α, wingless, Ribosomal protein S5, Isocitrate dehydrogenase, Cytosolic malate dehydrogenase, Glyceraldehyde‐3‐phosphate dehydrogenase and Carbamoylphosphate synthase domain protein). Fifty‐two taxa representing nearly all established subfamilies and tribes of Gelechiidae, and about 10% of described gelechiid genera, in addition to five outgroup taxa were sequenced. Data matrices (6157 bp total) were analysed under model‐based evolutionary methods (Maximum Likelihood and Bayesian Inference), resulting in novel high‐level phylogenetic interrelationships. The best supported cladogram divided the Gelechiidae into six distinct clades corresponding to the subfamilies Anacampsinae, Dichomeridinae, Apatetrinae, Thiotrichinae, Anomologinae and Gelechiinae (+ Physoptilinae, which were not available for study). The results suggest the following adjustments in gelechiid interrelationships: Brachmini is nested within Dichomeridinae; Anarsiini is the sister group of Chelariini; Pexicopiinae is the sister group of Apatetrinae, here suggested to be treated as a tribe Pexicopiini of Apatetrinae. A new subfamily Thiotrichinae ( subfam.n. ) is proposed on the basis of the resurrected genus Thiotricha Meyrick ( gen.rev. ), which includes Macrenches Meyrick, Palumbina Rondani and Polyhymno Chambers. Gelechiidae display a wide array of life‐history strategies, but the diversity in patterns of larval mode of life has direct phylogenetic correlation only below subfamily level, suggesting multiple origins and/or frequent reversals for traits such as external or internal feeding and leaf mining within the family.     

Cyclic AMP Phosphodiesterase and its Inhibitor in Slime Mould Development

CYCLIC adenosine-3′,5′-monophosphate (cyclic AMP) acts as a chemotactic factor causing cell aggregation in the slime mould, Dtctyosteltum discoideum^1,2. Aggregation in this organism is the link between the growth phase and the second phase of development, in which cells cooperate and differentiate to form a multicellular fruiting body. The finding that cyclic AMP also mediates developmental functions other than chemotaxis³ suggests that regulation of cyclic AMP synthesis and destruction is important in the control of morphogenesis in D. discoideum.     

Phylogeographic analyses reveal distinct lineages of the liverworts Metzgeria furcata (L.) Dumort. and Metzgeria conjugata Lindb. (Metzgeriaceae) in Europe and North America

Seed plant genera often exhibit intercontinental disjunctions where different species are found on different continents. Many morphologically circumscribed bryophyte species exhibit similar disjunctions. We used nucleotide sequences from the plastid and nuclear genomes to test hypotheses of phylogeography within representatives of the genus Metzgeria: Metzgeria furcata, Metzgeria conjugata, and Metzgeria myriopoda. The first two species have sexual and asexual populations, exhibit disjunctions between North America and Europe, and have been split into separate species, numerous subspecies or varieties. The third species occurs in eastern North America but is not reported from Europe. Phylogenetic analyses resolved three distinct lineages within the morphologically defined species, M. furcata: one in North America, and two in Europe. Similarly, three morphologically cryptic clades of M. conjugata were resolved by the molecular data: northern North America, Europe, and south‐eastern North America. For both species, molecular divergence among taxa occurred in the absence of morphological change. In the case of M. myriopoda, all plants from eastern North America were both morphologically uniform and genetically homogeneous (although not identical). The present study provides significant insight into a plant group with complex taxonomy, and indicates that these liverwort taxa with wide distributions, extreme sex ratios, and continental disjunctions harbor cryptic lineages. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 745–756.     

The ‘Expansion–Contraction’ model of Pleistocene biogeography: rocky shores suffer a sea change?

Approximately 20 000 years ago the last glacial maximum (LGM) radically altered the distributions of many Northern Hemisphere terrestrial organisms. Fewer studies describing the biogeographic responses of marine species to the LGM have been conducted, but existing genetic data from coastal marine species indicate that fewer taxa show clear signatures of post-LGM recolonization. We have assembled a mitochondrial DNA (mtDNA) data set for 14 co-distributed northeastern Pacific rocky-shore species from four phyla by combining new sequences from ten species with previously published sequences from eight species. Nuclear sequences from four species were retrieved from GenBank, plus we gathered new elongation factor 1-α sequences from the barnacle Balanus glandula . Results from demographic analyses of mtDNA for five (36%) species ( Evasterias troschelii, Pisaster ochraceus, Littorina sitkana, L. scutulata, Xiphister mucosus ) were consistent with large population expansions occurring near the LGM, a pattern expected if these species recently recolonized the region. However, seven (50%) species ( Mytilus trossulus, M. californianus, B. glandula, S. cariosus, Patiria miniata, Katharina tunicata , X. atropurpureus ) exhibited histories consistent with long-term stability in effective population size, a pattern indicative of regional persistence during the LGM. Two species of Nucella with significant mtDNA genetic structure showed spatially variable demographic histories. Multilocus analyses for five species were largely consistent with mtDNA: the majority of multilocus interpopulation divergence times significantly exceeded the LGM. Our results indicate that the LGM did not extirpate the majority of species in the northeastern Pacific; instead, regional persistence during the LGM appears a common biogeographic history for rocky-shore organisms in this region.