Developmental expression of the murine Prl-1 protein tyrosine phosphatase gene

The expression of the murine Prl-1 protein tyrosine phosphatase gene was examined in normal embryos from E10.5 through E18.5. Prl-1 mRNA was detected in the brain, neural tube, and dorsal root ganglia, and in several non-neuronal tissues, including the skeletal system. Heart and skeletal muscle were consistently negative. At E13.5, Prl-1 was expressed in the condensing prechondrogenic cells of the vertebrae, whereas at E18.5, Prl-1 mRNA was localized to the hypertrophic chondrocytes. The dynamic expression of Prl-1 during cartilage differentiation may suggest a functional role in skeletal development.     

Divergent environments and population bottlenecks fail to generate premating isolation in Drosophila pseudoobscura

While the feasibility of bottleneck-induced speciation is in doubt, population bottlenecks may still affect the speciation process by interacting with divergent selection. To explore this possibility, I conducted a laboratory speciation experiment using Drosophila pseudoobscura involving 78 replicate populations assigned in a two-way factorial design to both bottleneck (present vs. absent) and environment (ancestral vs. novel) treatments. Populations independently evolved under these treatments and were then tested for assortative mating and male mating success against their common ancestor. Bottlenecks alone did not generate any premating isolation, despite an experimental design that was conducive to bottleneck-induced speciation. Premating isolation also did not evolve in the novel environment treatment, neither in the presence nor absence of bottlenecks. However, male mating success was significantly reduced in the novel environment treatment, both as a plastic response to this environment and as a result of environment-dependent inbreeding effects in the bottlenecked populations. Reduced mating success of derived males will hamper speciation by enhancing the mating success of immigrant, ancestral males. Novel environments are generally thought to promote ecological speciation by generating divergent natural selection. In the current experiment, however, the novel environment did not cause the evolution of any premating isolation and it reduced the likelihood of speciation through its effects on male mating success.     

Industrial microbiology of solar salt production

Solar salterns can be modeled as giant outdoor chemostats, much like a series of dams on a slow-moving river. Microorganisms and their products play an essential, but sometimes uncharacterized, role in salt production in these ponds, from seawater salinity up through NaCl saturation. They may physically affect the evaporation process and their by-products may chemically modify or bind with dissolved ions. Many solar salt facilities engage microbiologists to establish monitoring programs for analyses of nutrients, standing crop and associated biological variables in the ponds. Other solar salt companies engage microbiologists only when there are “crises” in the ponds that interfere with salt production. Journal of Industrial Microbiology & Biotechnology (2002) 28, 42–47 DOI: 10.1038/sj/jim/7000173 Received 20 May 2001/ Accepted in revised form 13 June 2001     

Global and regional patterns in lotic meiofauna

• 1 Parsimony analysis of endemicity (PAE) was used to assess patterns in the distribution of harpacticoid copepods (all freshwater species and stream species only) at global and regional scales. These analyses provided a focus for reviewing large scale patterns and processes in freshwater meiofauna.
• 2 On a global scale, PAE suggested that large‐scale biogeographical events have been most important in shaping present‐day distributions in the Canthocamptidae. A small proportion (4%) of canthocamptid species were widespread (i.e. occurred in more than one biogegraphical region), suggesting that dispersal may also play a role in determining distribution at the species level. Global distribution patterns for other meiofauna suggest varying roles for dispersal and vicariant events. No consistent latitudinal trends in species diversity were evident, although a lack of distributional data for many regions, and uncertainty over the status of many cosmopolitan species, precludes more robust analyses. Molecular techniques should prove useful in identifying truly cosmopolitan taxa.
• 3 On a regional scale, a PAE within Western Europe demonstrated a clear link between the distribution of canthocamptid species and the extent of the Last (Wiechselian) glaciation. Northern and southern areas of Europe contain distinctive harpacticoid faunas and the recolonisation of northern Europe appears to have been from the Balkans rather than other Mediterranean peninsulae. The high harpacticoid diversity in southern Europe, may reflect a lack of glacial disruption of groundwater habitats.
• 4 A PAE of lotic data for harpacticoid copepods within the Holarctic reflected the global PAE for freshwater harpacticoids as a whole, but not the regional PAE. A high proportion of stream‐dwelling harpacticoids are widespread species, but only one (Bryocamptus zschokkei) was found in streams across the Holarctic. Other cosmopolites were restricted to streams in Europe or North America, suggesting that species‘ niche requirements might differ among regions. There appeared to be some convergence in the composition of lotic copepod communities in terms of the number of species within genera.
• 5 We conclude that large‐scale processes inevitably have a major influence on the local composition of lotic meiofaunal communities, but that the relative importance of small scale vs. large scale processes is unclear at present, largely due to a paucity of suitable data.

     

REPRODUCTIVE CHARACTER DISPLACEMENT OF EPICUTICULAR COMPOUNDS AND THEIR CONTRIBUTION TO MATE CHOICE IN DROSOPHILA SUBQUINARIA AND DROSOPHILA RECENS

Interactions between species can alter selection on sexual displays used in mate choice within species. Here we study the epicuticular pheromones of two Drosophila species that overlap partially in geographic range and are incompletely reproductively isolated. Drosophila subquinaria shows a pattern of reproductive character displacement against Drosophila recens, and partial behavioral isolation between conspecific sympatric versus allopatric populations, whereas D. recens shows no such variation in mate choice. First, using manipulative perfuming experiments, we show that females use pheromones as signals for mate discrimination both between species and among populations of D. subquinaria. Second, we show that patterns of variation in epicuticular compounds, both across populations and between species, are consistent with those previously shown for mating probabilities: pheromone compositions differ between populations of D. subquinaria that are allopatric versus sympatric with D. recens, but are similar across populations of D. recens regardless of overlap with D. subquinaria. We also identify differences in pheromone composition among allopatric regions of D. subquinaria. In sum, our results suggest that epicuticular compounds are key signals used by females during mate recognition, and that these traits have diverged among D. subquinaria populations in response to reinforcing selection generated by the presence of D. recens.     

Rapid and unexpected effects of piscivore introduction on trophic position and diet of perch (Perca flavescens) in lakes recovering from acidification and metal contamination

1. Yellow perch (Perca flavescens) are often the only surviving fish species in acidified lakes. We studied four lakes along a gradient of recovery from acidification and that had different food web complexities. All had abundant yellow perch, two had low piscivore abundance, one had a well‐established piscivore population and one was manipulated by introducing piscivorous smallmouth bass (Micropterus dolomieu). We hypothesised that there would be strong effects on perch abundance, behaviour and diet induced by the presence of piscivores. 2. In the manipulated lake, the bass reduced yellow perch abundance by 75% over a 2‐year period. Concomitantly, perch use of the pelagic habitat fell from 48 to 40%. 3. In contrast to findings from less disturbed systems, yellow perch in the littoral zone of the manipulated lake did not strongly shift from zooplankton to benthic food sources after the arrival of piscivores. Diet analysis using stable carbon isotopes revealed a strong continued reliance on zooplankton in all lakes, independent of the degree of piscivory. The failure to switch to benthos in the refuge area of the littoral zone is most likely related to the depauperate benthos communities in these formerly acidified lakes. 4. Yellow perch in lakes recovering from acidification face a considerable ecological challenge as the necessary switch to benthic diet is hindered by a low abundance of benthos. The arrival of piscivores in these recovering lakes imposes further restrictions on perch access to food items. We infer that future recovery of perch populations (and higher trophic levels) will have to be preceded by the re‐establishment of diverse benthic macroinvertebrate communities in these lakes.     

Alarm substance from adult zebrafish alters early embryonic development in offspring

Alarm substances elicit behavioural responses in a wide range of animals but effects on early embryonic development are virtually unknown. Here we investigated whether skin injury-induced alarm substances caused physiological responses in embryos produced by two Danio species (Danio rerio and Danio albolineatus). Both species showed more rapid physiological development in the presence of alarm substance, although there were subtle differences between them: D. rerio had advanced muscle contraction and heart function, whereas D. albolineatus had advanced heart function only. Hence, alarm cues from injured or dying fish may be of benefit to their offspring, inducing physiological responses and potentially increasing their inclusive fitness.     

Predation on Moose Calves by European Brown Bears

Abstract: In North America, brown bears (Ursus arctos) can be a significant predator on moose (Alces alces) calves. Our study in Sweden is the first in which brown bears are the only predator on moose calves. Bears and moose occurred at densities of about 30/1,000 km² and 920/1,000 km², respectively, and bears killed about 26% of the calves. Ninety-two percent of the predation took place when calves were <1 month old. Bear predation was probably additive to other natural mortality, which was about 10% in areas both with and without bears. Females that lost their calves in spring produced more calves the following year (1.54 calves/F) than females that kept their calves (1.11 calves/F), which reduced the net loss of calves due to predation to about 22%.     

Do developmental mode and dispersal shape abundance-occupancy relationships in marine macroinvertebrates?

1. Dispersal is a crucial process in maintaining population structures in many organisms, and is hypothesized as a process underlying the interspecific relationship between abundance and distribution. Here we examined whether there was a link between the dispersal and developmental modes of marine macroinvertebrates and the slopes and elevations of interspecific abundance-occupancy relationships. We predicted that if within-site retention of larvae ranks in the order brooders > lecithotrophs > planktotrophs, for any given level of mean abundance, occupancy should increase in the order brooders < lecithotrophs < planktotrophs. We also predicted that propensity to form metapopulations should be greater for planktonic dispersers (i.e. lecithotrophs and planktotrophs combined) than for non-planktonic (i.e. brooders), resulting in steeper abundance-occupancy relationships for the former. 2. Predictions were tested using a data set for 362 subtidal marine macroinvertebrates occurring across 446 1-km(2) grid squares around the British Isles; analyses were performed on the data set as a whole and for separate phyla. 3. The total data set had a Z-transformed effect size of 0.79, within the confidence intervals described by Blackburn et al. (2006; Journal of Animal Ecology, 75, 1426-1439), and was consistently present with relatively homogeneous effect size in separate analyses of polychaetes, crustaceans, molluscs and echinoderms. 4. In all cases, planktonic dispersing organisms showed an abundance-occupancy relationship with greater elevation than that for non-planktonic organisms; in polychaetes the elevation of slopes was in the rank order planktotrophs > lecithotrophs > brooders. No differences between the slopes of the abundance-occupancy relationship were apparent for different dispersal modes either within, or across phyla. 5. We conclude that dispersal capacity may play an important part in determining the elevation of the abundance-occupancy relationship, the corollary of low dispersal in the marine realm being greater local retention of larvae and greater local population abundance at low extents of geographical distribution.