Regeneration patterns and persistence of the fog-dependent Fray Jorge forest in semiarid Chile during the past two centuries

The persistence of rainforest patches at Fray Jorge National Park (FJNP) in semiarid Chile (30°40′S), a region receiving approximately 147 mm of annual rainfall, has been a source of concern among forest managers. These forests are likely dependent on water inputs from oceanic fog and their persistence seems uncertain in the face of climate change. Here, we assessed tree radial growth and establishment during the last two centuries and their relation to trends in climate and canopy disturbance. Such evaluation is critical to understanding the dynamics of these semiarid ecosystems in response to climate change. We analyzed forest structure of six forest patches (0.2–22 ha) in FJNP based on sampling within 0.1 ha permanent plots. For the main canopy species, the endemic Aextoxicon punctatum (Aextoxicaceae), we used tree‐ring analysis to assess establishment periods, tree ages, growing trends and their relation to El Niño Southern Oscillation (ENSO), rainfall, and disturbance. The population dynamics of A. punctatum can be described by a continuous regeneration mode. Regeneration of A. punctatum was sensitive to different canopy structures. Growth release patterns suggest the absence of large scale human impact. Radial growth and establishment of A. punctatum were weakly correlated with rainfall and ENSO. If water limits forests patch persistence, patches are likely dependent on the combination of fog and rain water inputs. Forest patches have regenerated continuously for at least 250 years, despite large fluctuations in rainfall driven by ENSO and a regional decline in rainfall during the last century. Because of the positive influence on fog interception, forest structure should be preserved under any future climate scenario. Future research in FJNP should prioritize quantifying the long‐term trends of fog water deposition on forests patches. Fog modeling is crucial for understanding the interplay among physical drivers of water inputs under climate change.     

Effects of aphids on foliar foraging by Argentine ants and the resulting effects on other arthropods

Abstract.  1. Although interactions between ants and honeydew-producing insects have received considerable study, relatively little is known about how these interactions alter the behaviour of ants in ways that affect other arthropods. In this study, field and greenhouse experiments were performed that examined how the presence of aphids ( Aphis fabae solanella ) on Solanum nigrum influenced the foraging behaviour of Argentine ants ( Linepithema humile ) and, in turn, modified the extent to which ants deter larval lacewings ( Chrysoperla rufilabris ), which are known aphid predators.
2. A field experiment demonstrated that the level of foliar foraging by ants increased linearly with aphid abundance, whereas no relationship existed between the level of ground foraging by ants and aphid abundance.
3. In the greenhouse, as in the field, foliar foraging by ants greatly increased when aphids were present. Higher levels of foliar foraging led to a twofold increase in the likelihood that ants contacted aphid predators. As a result of these increased encounters with ants, lacewing larvae were twice as likely to be removed from plants with aphids compared with plants without aphids. Once contact was made, however, the behaviour of ants towards lacewing larvae appeared similar between the two experimental groups.
4. Argentine ants drive away or prey upon a diversity of arthropod predators and parasitoids, but they also exhibit aggression towards certain herbivores. Future work should attempt to quantify how the ecological effects that result from interactions between honeydew-producing insects and invasive ants, such as L. humile , differ from those that result from interactions between honeydew-producing insects and native ants.     

Fourteen polymorphic microsatellite loci characterized in the house sparrow Passer domesticus (Passeridae,Aves)

We characterized 14 polymorphic microsatellite loci in the house sparrow Passer domesticus. Four loci were isolated from house sparrow genomic libraries and 10 loci were identified by testing 100 loci that had been originally isolated in other passerine species. Loci were characterized in 37–54 unrelated sparrows from British and Norwegian populations. Each locus displayed between two and 31 alleles, with the observed heterozygosity ranging between 0.30 and 0.91.     

Mitochondrial DNA and two perspectives on evolutionary genetics

This essay reviews comparative studies of animal mitochondrial DNA (mtDNA), with emphasis on findings made and ideas developed at Berkeley. It argues that such studies are bringing together two previous paths of progress in evolutionary biology. One path is that of those who worked far above the species level and were concerned with genealogical trees, time scales and the accumulation of new mutations on surviving molecular lineages. The other path is that of those who worked at and below the species level and were concerned mainly with population structure, migration and the frequencies of alleles that existed in an ancestral population. This fusion of paths is made possible by the high rate at which mutations accumulate on mtDNA lineages and by this molecule's uniparental and apparently haploid mode of inheritance. These properties make mtDNA a superb tool for building trees and time scales relating molecular lineages at and below the species level. In addition, owing to its mode of inheritance, mtDNA is more sensitive to bottlenecks in population size and to population subdivision than are nuclear genes. Joint comparative studies of both mtDNA and nuclear DNA variability give us valuable insights into how effective population size has varied through time. Such studies also give insight into the conditions under which mtDNA from one species can colonize another species.     

Molecular evidence for the phylogeny of Australian gekkonoid lizards

Partial sequences of the mitochondrial 12S rRNA and nuclear c-mos genes were determined for 12 species of gekkonoid lizards representing the four major taxa of the Australian region, the Diplodactyhni and Carphodactylini (forming the subfamily Diplodactylinae), the Pygopodidae and the Gekkoninae. One further species represented a non-Australian gekkonoid lineage, the Eublepharinae. The combined sequence data were used to reconstruct the underlying molecular phylogeny. We used the molecular phylogeny to test the monophyly of the diplodactyline tribes and conflicting hypotheses of relationships of die pygopods and of the genus Oedura. Monophyly of the Diplodactylinae is supported, while pygopods form a monophyletic sister lineage to all Diplodactylinae. The molecular data support the monophyly of the Diplodactyhni, with Oedura firmly placed as a diplodactylin. Monophyly of the Carphodactylini is not supported. The four carphodactylin genera form a paraphyletic cluster at the base of the Diplodactyhni. Pygopods are nested within the traditional Gekkonidae and pygopods plus diplodactylines form a well-supported monophyletic group with respect to the remaining gekkonoids, the gekkonines and eublepharines.     

TRACING INEFFICIENT PASTEURIZATION IN HOLDER PLANTS

Examination of a holder pasteurizing plant giving occasional apparently inexplicable phosphatase test failures proved that excessive froth on the surface of the milk during holding, resulting from an unsuitable type of pre-heater, was causing the trouble. Uninsulated lids allowed considerable loss of heat from the froth. Other plants of the same make were examined and the same inherent faults found.
Two other makes of holder plant with well insulated lids were also tested. There was a large air space under the lid in one plant in which phosphatase test failures occurred in the froth and surface milk, whereas the other plant, with no air space, gave no failures.
One hundred bacterial cultures from two bulked froth samples from two plants were tested for heat resistance. A number of these, including a streptococcus, a sarcina, a micrococcus, and several Gram-negative rods, were found to have heat resistance similar to that of tubercle bacilli.     

THE INFLUENCE OF DISSOLVED-OXYGEN CONCENTRATION ON THE TOXICITY OF UN-IONIZED AMMONIA TO RAINBOW TROUT (SALMO GAIRDNERII RICHARDSON)

Periods of survival of rainbow trout in concentrations of un-ionized ammonia in the range 0.86-1.96 parts per million of nitrogen increased as the concentration of dissolved oxygen was raised from 1–5 to 8-5 p.p.m.
At each concentration of dissolved oxygen the period of survival decreased as the concentration of un-ionized ammonia increased from 0.86 to 1.96 p.p.m.
The effect of oxygen in increasing survival time was greater in the lower concentrations of un-ionized ammonia.     

Studies in the Bangioideae III. The Life-history of Porphyra umbilicalis (L.) Kutz. var. lociniata (Lightf.) J. Ag.: A. The Conchocelis-Phase in culture

As the first step in an investigation of the life-history ofPorphyra umbilicalis (L.) Kütz. var. laciniata (Lightf.)J. Ag., spores which have originated as a result of the repeateddivision of the mother-cells have been germinated. When grownon glass their method of germination and growth agrees withthat described by previous investigators, but when germinatedon sterile shell the germ-tubes penetrate the shell and developinto growths identical with Conchocelis rosea Batters. This‘species’, therefore, is a phase in the life-historyof P. umbilicalis var. laciniata and not an autonomous species.The development of the ‘Conchocelis’-phase in cultureis described and also the formation of fertile cell-rows and‘plantlets’. Until the significance of these structuresis understood and a cytological investigation completed, therelationship of the intertidal leafy Porphyra-thallua to thefilamentous, shell-inhabiting, deep-water Conchocelis cannotbe expressed in the terms usually employed to denote the variousphases of the life-histories of algae.