Geographical variation in male advertisement calls and female preference of the wide‐ranging canyon treefrog,Hyla arenicolor

We surveyed the geographical variation in male advertisement calls of the wide‐ranging canyon treefrog, Hyla arenicolor, and found large call differences among geographically distant lineages that had been characterized by a recent phylogeographical study. To test whether these call differences were biologically relevant and could allow reproductive isolation of different lineages should they come into secondary contact, we assessed female preference in a lineage occurring in southern Utah and north‐western Arizona, USA. These females exhibited a strong preference for their own lineage's call type over the calls of two Mexican lineages, but not over the calls from the geographically nearest lineage. We also identified traits that female frogs probably use to discriminate between lineage‐specific advertisement calls. Our behavioural results, together with recent molecular estimates of phylogenetic relationships among lineages, will guide future work addressing the evolutionary forces that have led to this biologically significant variation in male sexual signals. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ??, ??–??.     

Grazing management influences the subsidy of terrestrial prey to trout in central Rocky Mountain streams (USA)

1. Research in forest and grassland ecosystems indicates that terrestrial invertebrates that fall into streams can be an important prey resource for fish, providing about 50% of their annual energy and having strong effects on growth and abundance. However, the indirect effects of land uses like cattle grazing on this important prey subsidy for stream salmonids are unclear. 2. During summer 2007, we compared the effects of three commonly used grazing systems on terrestrial invertebrate inputs to streams in northern Colorado and their use by trout. Cattle graze individual pastures for about 120 days under traditional season‐long grazing (SLG), about 35–45 days under simple rotational grazing and 10–20 days under intensive rotational grazing in this region. We also compared these effects to a fourth group of sites grazed only by wildlife (i.e. no livestock use). 3. Overall, rotational grazing management (either simple or intensive), resulted in more riparian vegetation, greater inputs of terrestrial invertebrates, greater biomass of terrestrial invertebrate prey in trout diets, a higher input compared to trout metabolic demand and more trout biomass than SLG. However, these differences were frequently not statistically significant owing to high variability, especially for trout diets and biomass. 4. Despite the inherent variability, riparian vegetation and terrestrial invertebrates entering streams and in trout diets at sites managed for rotational grazing were similar to sites managed for wildlife grazing only. 5. These results indicate that rotational grazing systems can be effective for maintaining levels of terrestrial invertebrate subsidies to streams necessary to support robust trout populations. However, factors influencing the effect of riparian grazing on stream subsidies are both spatially variable and complex, owing to differences in microclimate, invertebrate and plant populations and the efforts of ranchers to tailor grazing systems to specific riparian pastures.     

Parasites and Mate Choice in Gray Treefrogs, Hyla versicolor

A fundamental assumption of the Hamilton and Zuk (1982) modelof sexual selection is that parasite-free males should producemate attracting displays that are substantially more vigorousand effective than those of their parasitized counterparts.Further, the model predicts that parasite-free males shouldbe preferred as mating partners by females and, as a consequence,should have higher reproductive success than their parasitizedcompetitors. Gray treefrogs (Hyla versicolor) constitute anideal species for testing both assumptions and predictions ofthe Hamilton-Zuk model in that: (i) mate attraction by malesrequires the production of energetically costly calls and (ii)males of this species have been shown to harbor a wide rangeof helminth parasites. The present paper summarizes resultsof analyses of calling and mating behavior by male gray treefrogsin relation to their parasite infection levels. In general,these analyses revealed no consistent relationship between thenumber and kinds of parasites harbored by males and either theduration or duty-cycle (a direct measure of energetic cost)of their calls. Furthermore, males found in amplexus (i.e.,males actually selected as mating partners by females) showeda slightly higher prevalence of parasite infection (but a slightlylower intensity of infection) than did a comparable sample ofunmated males. In sum, the present study failed to support themajor within-species prediction of the Hamilton-Zuk model ofsexual selection and also calls into question one of the fundamentalassumptions of the model.     

Fish Tumor Pigment Cells: Differentiation and Comparison to Their Normal Counterparts

The objectives of this paper are to describe 1) the developmentof new research systems for biochemical comparison of cellulartraits between normal and tumorous pigment cells of fish origin,2) the similarity and dissimilarity between these two categoriesof pigment cells with regard to growth, differentiation andpigment translocating activities and 3) the potentials of thesetumorous pigment cells to manifest multiple differentiation.The development of research systems has been achieved by theestablishment of 1) methods to obtain homogenous populationsof viable, cultivatable xanthophores (erythrophores) and melanophoresfrom goldfish skins, 2) permanent cell lines from goldfish erythrophoromas(tumors derived from erythrophores) and from Nibe croaker irido-melanophoromas(tumors composed of mixed populations of iridophore- and melanophore-likecells) and 3) procedures to induce differentiation in normaland tumorous stem cells (including the formation of pigmentsand ability to undergo pigment translocation in response tocAMP, to the neurotransmitter epinephrine and to the hormonesACTH and melatonin). Two kinds of tumorous pigment cell linesexamined herein have the ability to form, in addition to variouspigments, structures similar to dermal skeletons and lentoidbodies. These findings strongly suggest the possibility thatthese fish pigment cell tumors are neural crest stem cell tumorsin nature.     

Spring habitat use and feeding behaviour of Steller's Eider Polysticta stelleri in Varangerfjord, northern Norway

The distribution and abundance of Steller's Eider Polysticta stelleri were studied in Varangerfjord, Norway, in May 1995, immediately prior to the birds' departure for the breeding areas. Almost 80% of the variance in Steller's Eider numbers was explained by a regression model based upon low tide beach width, suggesting strong selection for gently shelving coastal profiles. Such habitat is common but restricted in Varangerfjord and is rare along surrounding coastlines where the species is more scarce. The majority of Steller's Eider and the Common Eider Somateria mollissima were recorded within 200 m of the coast, in contrast to the King Eider Somateria spectabilis , which tended to be more than 200 m from the shore. More detailed observations at one study site showed that Common and Steller's Eiders fed in different ways and in separate areas, despite similar proximity to the shore, although the two species did aggregate together to roost at high tide, particularly during the daytime. Steller's Eider showed a strong tidal rhythm in activity by day and night, roosting at high tide, diving offshore on the ebb and flow tides but resorting to algal beds and sandy-mud beaches to feed at low tide.     

Evolutionary Trends in the Subsocial Sawflies Belonging to the Neodiprion abietis Complex (Hymenoptera: Tenthredinoidea)

Populations of the Neodiprion abietis complex occur on firsand spruces in North America. A distinct western populationon white fir differs greatly in appearance from the four easternstrains, of which two feed on balsam fir and one each on blackand white spruce respectively. Differences in developmentalrates, larval survival on the various food plants, and hostselection by the females supply the isolating mechanisms betweenthe strains in the field. All populations cross-mated freelyin the laboratory, and the resulting hybrids indicate the transmissionof Several morphological and physiological characters. It isspeculated that the ancestral line of the complex fed on pinebefore a jump to spruce and then to balsam was made.     

Catchment and reach-scale properties as indicators of macroinvertebrate species traits

1. We used catchment and reach-scale physical properties to predict the occurrence of specific species life history and behaviour traits of aquatic insects across fifty-eight catchments in a mixed land use basin. Catchment-scale attributes were derived using a geographical information system (GIS). Logistic regression techniques were used to model the relationships.
2. The reach-scale properties were highly predictive of species traits. Fourteen of the fifteen traits had significant models with concordance values greater than 68%. Cross-sectional area at bank full discharge, % shallow, slow-water habitats, and % fines were the most important variables.
3. Life history and behavioural attributes were best related to reach-scale physical features. This suggests that species traits exhibit strong relationships to local environmental conditions.
4. Catchment-scale variables had fewer significant models with species traits (four of fifteen), however these variables may have direct or indirect influence on reach-scale properties.
5. Catchment features, in particular surficial geology, influence macroinvertebrate assemblages through their control over channel morphology and hydrologic patterns.
6. The effects of land use were masked by geology (i.e. lacustrine clay geology and rowcrop agriculture were correlated), lack of detail in land use data and the aggregation of the species data.
7. These models reflect the coupling of local environmental conditions and the set of adaptations among the local taxa. These observations underscore the idea that habitat plays a major role in organizing stream assemblages.
8. Using these approaches, predictions can be made about the ability of various taxonomic groupings to track environmental change through time, or for projecting the impact of alternative land management scenarios. Identifying fundamental life history and other traits can improve the selection and evaluation of such indicators.