Rediscovery and Mitochondrial Relationships of the Dendrobatid Frog Colostethus humilis Suggest Parallel Colonization of the Venezuelan Andes by Poison Frogs

Colostethus humilis Rivero, ‘1978’1980 was rediscovered near the type locality. The species is redescribed, and data on its advertisement call are provided for the first time. Its morphology and colour pattern differ from other Andean dendrobatids. It shows morphological and bio-acoustic similarities to species of Colostethus from the Amazonian lowlands. A phylogenetic analysis of sequences of the mitochondrial 16S rRNA gene confirmed that C. humilis is related to Amazonian lowland Colostethus, rather than to other Andean poison frogs of the genera Nephelobates and Mannophryne. This indicates that several groups of basal dendrobatids independently have colonised the Venezuelan Andes.     

Factors affecting the fate of Pacific lamprey carcasses and resource transport to riparian and stream macrohabitats

1. Anadromous fish transport marine-derived nutrients to freshwaters during spawning migrations with potential implications for stream food webs. While many studies have explored the role of marine-derived nutrients instream ecosystems (particularly via Pacific salmonids [Oncorhynchus spp.]), relatively few have examined the spatial distribution and patchiness of non-salmonid fish carcasses or rates of transport to the riparian zone.
2. We radio-tagged and released 144 mature Pacific lamprey (Entosphenus tridentatus) prior to spawning and tracked the fate of post-spawn carcasses in two inland Columbia River basin streams to characterise spatial distribution of carcasses and marine-derived nutrient deposition. We found that 27 and 40% of lamprey that could be assigned a fate were moved into the riparian zone adjacent to stream segments exhibiting higher velocity conditions with larger substrates. Conversely, lamprey with instream fates were associated with depositional microhabitats and woody debris dams. Estimated carcass loading rates varied by more than an order of magnitude among habitats. These patterns probably reflect a combination of processes influencing the likelihood of carcass removal (e.g. by predators or scavengers, or stranding) and factors affecting the distribution of carcasses remaining within the stream.
3. Our results demonstrate substantial transport of lamprey carcasses across the stream-riparian ecotone and a non-random distribution of carcasses within streams, patterns which probably influence how resources enter stream and riparian food webs. More broadly, the results suggest local and landscape-scale hydrogeomorphic factors, along with species-specific traits and phenology, affect the distribution and potential roles of fish carrion in stream food webs.

     

Improving the performance of the EPT Index to accommodate multiple stressors in Afrotropical streams

The EPT index (Ephemeroptera, Plecoptera and Trichoptera) may be skewed by the wide tolerance to multiple stressors of the Baetid, Caenid and Hydropsychid families, which affects the performance of the EPT index as an indicator of multiple stressors in aquatic ecosystems. The effect of the BCH families on the EPT index was evaluated and alternatives were considered to improve its performance. The hypothesis that the removal of the BCH families improves sensitivity of the EPT index to human-induced stressors in streams and rivers was tested. Macroinvertebrates were collected in January–March 2009 at 22 sites in the Nyando and Nzoia Rivers, Lake Victoria basin, Kenya. Nine derivatives and modifications of the EPT index were tested for responses to a disturbance gradient, ranked into three condition categories (reference, intermediate and impaired). The sensitivity of the proportionate abundance derivative of the EPT index improved when the BCH families were removed, whereas that of the richness derivative improved marginally. Other modifications considered performed poorly when compared with the EPT-BCH metrics. Wide distribution of the BCH across all sites, irrespective of the level of disturbance, reduced the sensitivity of the EPT index in the studied streams. The removal of the BCH families enhanced the sensitivity of the index to multiple stressors in Afrotropical streams and rivers.     

DISTRIBUTION AND SYSTEMATICS OF BATRACHOSPERMUM (BATRACHOSPERMALES,RHODOPHYTA) IN NORTH AMERICA. 3. SECTION SETACEA1

Six populations of Batirachospermum section Setacea from North America were compared to eight type specimens using multivariate morphometrics and image analysis. From this analysis, four species in this section were distinguished worldwide: B. atrum (Hudson) Hartley [syn. B. gallaei Sirodot]; B. orrthostichum Skuja, B. sertularina (Bory) Bory]; B. diatyches Entwisle; B. androinvolucrum sp. nov.; and B. puiggarianum Grunow in Wittrock et Nordstedt (syn. B. angolense Welwitsch ex West et West, B. nigrescens Welwitsch ex West et West). Two of these species were found in North America: B. atrum in California and Texas and B. androinvolucrum in British Columbia, Washington State, and Alabama. The new species, B. androinvolucrum, is distinguished by having spermatangia restricted to one-celled involucral bracts of the carpogonial branch.     

Population and microhabitat effects of interspecific interactions on the endangered Andalusian toothcarp (A<Emphasis Type="Italic">phanius baeticus</Emphasis>)

The Andalusian toothcarp, Aphanius baeticus, is a critically endangered cyprinodontid species, with only nine known extant populations. Although not yet studied in the field, the distribution and abundance of Andalusian toothcarp are thought to be strongly influenced by interspecific interactions. We analysed the abundance and microhabitat use of Andalusian toothcarp in two water courses, one in which several other fish species occurred (sympatric site) and one hypersaline stream in which toothcarp was the only species present (allopatric site). Fish were sampled using plastic minnow traps and results were analysed separately for three size categories. Toothcarps were clearly more abundant in the allopatric population than in the sympatric one, though the difference was less apparent in the smallest size category. In coexistence with other species, toothcarp occupied shallower microhabitats, but in both sites in the absence of shelter fish selected deeper positions than in its absence. While in the sympatric site sheltered microhabitats were used predominately by small individuals, in the allopatric ones they were used by larger ones. Observed patterns strongly suggest that predation is the main mechanism involved in the differences in abundance and microhabitat use between sites. Our results confirm that the presence or absence of coexisting species is an important habitat feature for Andalusian toothcarp populations.     

Movement patterns of invertebrates in temporary and permanent streams

Summary Although it has been shown that invertebrates recolonize reflooded temporary streams from permanent refuges, e.g., the hyporheic zone, it has not been shown that they actively move into these refuges as streams dry. Substrate filled cages and drift nets were used to monitor invertebrate movement in two temporary streams and a permanent stream prior to and during drying to determine whether invertebrates leave drying riffles and enter flooded riffles. Invertebrate movement was essentially unidirectional in the permanent stream with downstream drift and with-in-substrate downstream movement dominating. In the temporary stream, movement vertically downward toward the hyporheic zone and upstream movement substantially contributed to a departure from a unidirectional pattern. In addition, prior to stream drying the relative colonization rate was higher and drift rate was lower in the temporary streams than in the permanent stream. During drying of the temporary stream, upstream movement continued to dominate but hyporheic movement was unimportant. Further, the upstream movement did not occur at the end of the riffle where it would lead to migration into non-drying riffles. Thus, even though movement patterns were different in permanent and temporary streams the pattern observed during stream drying would result in the concentration and subsequent death of invertebrates in drying riffles. This observation demonstrates that movement patterns of stream invertebrates do not necessarily result in behavioral avoidance of a dry period of temporary fiffles.     

Seasonal relationships between planktonic microorganisms and dissolved organic material in an alpine stream

The relationships between the abundance and activity of planktonic, heterotrophic microorganisms and the quantity and characteristics of dissolved organic carbon (DOC) in a Rocky Mountain stream were evaluated. Peak values of glucose uptake, 2.1 nmol L⁻¹ hr⁻¹, and glucose concentration, 333 nM, occurred during spring snowmelt when the water temperature was 4.0°C and the DOC concentration was greatest. The turnover time of thein situ glucose pool ranged seasonally from 40–1110 hours, with a mean of 272 hr. Seasonal uptake of³H-glucose, particulate ATP concentrations, and direct counts of microbial biomass were independent of temperature, but were positively correlated with DOC concentrations and negatively correlated with stream discharge. Heterotrophic activity in melted snow was generally low, but patchy. In the summer, planktonic heterotrophic activity and microbial biomass exhibited small-scale diel cycles which did not appear to be related to fluctuations in discharge or DOC, but could be related to the activity of benthic invertebrates. Leaf-packs placed under the snow progressively lost weight and leachable organic material during the winter, indicating that the annual litterfall in the watershed may be one source of the spring flush of DOC. These results indicate that the availability of labile DOC to the stream ecosystem is the primary control on seasonal variation in heterotrophic activity of planktonic microbial populations.     

Responses of a lake outlet community to light and nutrient manipulation: effects on periphyton and invertebrate biomass and composition

1.  Experimental channels were installed at the outlet of a small Canadian Shield lake to study the role of light and nutrients on the regulation of periphyton and invertebrate biomass and taxonomic composition. Light (93% reduction) and nutrients (four-fold increase of ambient total phosphorus (TP) concentration) were manipulated in a factorial design experiment.
2.  Periphyton chlorophyll a (Chl a ), measured four times during the 12-week experiment, increased due to higher irradiance but was unaffected by phosphorus enrichment. Over the experiment, periphyton biomass was, on average, three times higher in open than in shaded channels.
3.  Algal taxonomic and growth form composition were affected by light and phosphorus enrichment. The proportion of cyanophytes was significantly higher in unenriched, shaded channels (45%) compared to the three other treatments. Single cells and colonial forms were dominant in shaded channels, whereas filamentous and chain-forming algae were prevalent in open channels.
4.  Total invertebrate biomass remained unchanged over time and among treatments. At the beginning of the experiment, all the channels were dominated by Chironomidae and filter feeders (Simuliidae and Hydropsychidae). After 55 days, filter feeders became clearly dominant (60%) in all treatments except in the enriched, open channels where there was a significant shift in the functional group composition toward grazers (snails and oligochaetes). Among filter feeders, Simuliidae increased in shaded channels.     

Zoobenthic Communities of Inlets and Outlets of High Altitude Alpine Lakes

Due to their sensitivity, remote mountain lakes and streams are not only vulnerable to environmental change but also excellent sensors of such changes. Notwithstanding their importance as an ultimate resource of unpolluted waters, the alpine biome remains one of the less studied ecosystems in the world. This study involved the analysis of a database of zoobenthic communities collected in 36 inlets and 44 outlets of Swiss (Canton Bern) and Italian (Piedmont, Trentino-Alto Adige) Alpine lakes. All the streams are above the tree line and were sampled qualitatively in September/October (mostly in 2000) by disturbing the substrate and concentrating the dislodged animals with a standard pond net (250 μm mesh size). Generally higher population densities and taxon richness were found in the outlets than in the inlets. Fifty-seven per cent of taxa were common to the two stream types, with 17% found exclusively in the inlets and 26% in the outlets. Piedmont had the highest number of taxa found only in the region, Trentino-Alto Adige the lowest number. Insects represented 89% and 81% of the zoobenthic community of inlets and outlets, respectively. Among the insects, Diptera prevailed, with Chironomidae accounting for 68% of the mean inlet communities and 45% of those found in the outlets. The subfamily of Diamesinae was far more abundant in the inlets (16%) than in the outlets (1%). In contrast, the outlets hosted more Ephemeroptera, Trichoptera, Plecoptera, Oligochaeta and Tricladida. Some significant differences regarding the distribution of some species were found along the West–East and South–North gradients. The lakes appeared to affect the structure of the stream zoobenthic community by ameliorating the harsh physico-chemical conditions of the tributaries but no evidence was found indicating an increase in organic matter. In fact, filter-feeding invertebrates did not show any significant increase in the outlets, though the number of these taxa was higher downstream of the lakes.     

Beta diversity of aquatic macroinvertebrate assemblages associated with leaf patches in neotropical montane streams

Over 70% of the total channel length in all river basins is formed by low order streams, many of which originate on mountaintops. Headwater streams play fundamental roles in processing and transporting terrestrial and aquatic organic matter, often harboring high biodiversity in bottom leaf patches deposited from riparian vegetation. The objective of this study was to assess the variation in taxonomic composition (measured by beta diversity of aquatic macroinvertebrates) among stream sites located in the Espinhaço Meridional Mountain Range, part of a UNESCO Biosphere Reserve in eastern Brazil. We tested two hypotheses. (a) Taxa turnover is the main reason for differences in aquatic insect assemblages within stream sites; we predicted that turnover would be higher than nestedness in all stream sites. (b) Stream site altitude and catchment elevation range are the main explanatory variables for the differences in beta diversity; we predicted that local stream site variables would account for only minor amounts of variation. In both dry and wet seasons, we sampled twice in two habitat types (five leaf patches in pools and five in riffles) in each of nine stream sites distributed in three different river basins. We computed average pairwise beta diversity among sampling stations and seasons in each stream site by using Jaccard and Bray–Curtis indices, and calculated the percentages of diversity resulting from turnover and nestedness. Finally, we tested the degree that local‐ or catchment‐level predictor variables explained beta diversity. We found that turnover was the main component of beta diversity and that both dissolved oxygen and elevation range best explained Bray–Curtis beta diversity. These results reinforce the importance of leaf patches in montane (sky islands) Neotropical savanna streams as biodiversity hotbeds for macroinvertebrates, and that both local and landscape variables explained beta diversity.