Arboreal substrates influence foraging in tropical ants

1. Physically complex substrates impart significant costs on cursorial central‐place foragers in terms of time spent outside the nest and total distance travelled. Ants foraging in trees navigate varied surfaces to access patchy resources, thus providing an appropriate model system for examining interactions between foraging efficiency and substrates. 2. We expected that the speed of recruitment, body size distribution and species richness of foraging arboreal ants would differ predictably among common substrate types occurring on tropical tree trunks. We measured changes in ant abundance and species composition over time at baits placed on bare tree bark, moss‐covered bark, and vine‐like vegetation appressed to bark. We also measured average body size and body size frequency on the three substrate types. Ants discovered baits sooner and accumulated at baits relatively faster when using vine substrates as the primary foraging trail. Average body size was smaller on vine substrates than on bark. Experimental removal of vine and moss substrates nullified these differences. Contrary to our predictions, species richness and body size distributions did not differ among the three substrate types, due in part to the frequent presence of a few common ground‐nesting species at baits on bare bark. 3. Our results collectively indicate that linear substrates facilitate access of foraging ants to patchy resources. Ant use of vine‐like substrates appears to be opportunistic; vine use is not confined to certain species nor constrained by body size.     

Noncoding mitochondrial loci for corals

We developed five degenerate primer pairs for the amplification and sequencing of two noncoding regions found in the mitochondrial genome of corals. These primers amplify products ranging from 380 to 950 bp, and work in a wide variety of scleractinian taxa from both the Pacific and Caribbean. Based on our initial analysis of ～300 sequences from 13 scleractinian taxa, both these noncoding regions appear to have equivalent levels of variability to the most variable of previously published coral mitochondrial loci, but work in a wider variety of taxa. We believe these primers will be of use to coral biologists studying questions above the level of species; as with other mithochondrial DNA markers in corals, these loci will likely provide little resolution for within‐species studies.     

Seed dynamics of resprouting shrubs in grassy woodlands: Seed rain,predators and seed loss constrain recruitment potential

Abstract Measuring the fate of seeds between seed production and seedling establishment is critical in understanding mechanisms of recruitment limitation of plants. We examined seed fates to better understand the recruitment dynamics of four resprouting shrubs from two families (Fabaceae and Epacridaceae) in temperate grassy woodlands. We tested whether: (i) pre‐dispersal seed predation affected seed rain; (ii) post‐dispersal seed predation limited seed bank accumulation; (iii) the size of the seed bank was related to seed size; and (iv) viable seeds accumulated in the soil after seed rain. There was a distinct difference in seed production per plant between plant families with the legumes producing significantly more seeds per individual than the epacrids. Seed viability ranged from 43% to 81% and all viable had seed or fruit coat dormancy broken by heat or scarification. Pre‐dispersal predation by Lepidopteran larvae removed a large proportion of seed from the legume seed rain but not the epacrids. Four species of ants (Notoncus ectatomoides, Pheidole sp., Rhytidoponera tasmaniensis and Iridomyrmex purpureus) were major post‐dispersal seed removers. Overall, a greater percentage of Hardenbergia (38%) and Pultenaea (59%) seeds were removed than the fleshy fruits of Lissanthe (14%) or Melichrus (0%). Seed bank sizes were small (<15 seeds m^?2) relative to the seed rain and no significant accumulation of seed in the soil was detected. Lack of accumulation was attributed to seed predation as seed decay was considered unlikely and no seed germination was observed in our study sites. Our study suggests that seed predation is a key factor contributing to seed‐limited recruitment in grassy woodland shrubs by reducing the number of seeds stored in the soil.     

Possible Adaptive Value of Endosymbionts to Their Protozoan Hosts1,2

ABSTRACT. It is generally accepted that in symbiotic systems involving algal species as cellular endobionts there is some positive benefit to the host organisms. In this paper special consideration is given to the larger foraminifera, protozoa that serve as very useful model systems for the study of aspects of inter/intracellular integration and adaptation—living, as they do, in nutrient-limited but well illuminated shallow tropical seas and containing endosymbiotic algae in abundance. A considerable amount of information is now available on physiological as well as morphological adaptations of the host species to pigmented protists representing diverse algal divisions (phyla). Brief mention is also made of bacterial endosymbionts of certain ciliates.     

Marine Amoebae from Waters of Northwest Spain, with Comments on a Potentially Pathogenic Euryhaline Species

Of 17 species of free-living amoebae identified in various samples of salt water, only 1. Acanthamoeba polyphaga , is known to be a potential pathogen. While no deaths occurred when laboratory animals were inoculated with A. polyphaga to test for pathogenicity, the protozoa were present in the brain, liver and lungs of some but not all of the animals.     

Planktothrix populations in subalpine lakes: selection for strains with strong gas vesicles as a function of lake depth,morphometry and circulation

1. The genus Planktothrix (Cyanobacteria) usually produces concentrated populations of filaments in the summer metalimnion of thermally stratifying lakes. This has been associated with the action of gas vesicles, cellular structures providing positive buoyancy. At the end of the summer, filaments are carried by convective mixing deeper into the water column where some gas vesicles collapse as a result of high hydrostatic pressure. They then lose their buoyancy, sink and are lost from the euphotic zone. 2. The resistance of gas vesicles to hydrostatic pressures is critical for the survival of Planktothrix in deep lakes. However, comparative observations on populations from lakes of a range of depths and hydrodynamic regimes are still needed to examine the relationships between the adaptive trait (i.e. the ‘critical’ pressure at which each gas vesicle collapses) with the environmental factor (i.e. the maximum hydrostatic pressure). 3. To explore the adaptation of Planktothrix populations to the depth of winter circulation in different systems, we collected 276 strains of P. cf. rubescens from eight lakes (z_max = 24–410 m) in Northern Italy during summer 2009 and we analysed the multicopy gene gvpC coding for a protein that crucially influences the critical pressure. 4. The strains analysed clustered into two main groups having gas vesicles with a mean critical pressure of 1.1 and 0.9 MPa, respectively. The proportion of the stronger strains was generally positively related to lake depth, although the overall pattern was complicated by individual lake morphology and hydrology. The relative frequency of stronger filaments was (i) greatest in deep basins with concave slopes and (ii) least in one deep, but permanently stratified lake. 5. The simultaneous presence of ‘weaker’ and ‘stronger’ filaments could allow for a rapid adaptive response to changes in hydrostatic pressures, related to changes in the amplitude of vertical circulation characterising deep lakes.