Do wooded streets provide connectivity for bats in an urban landscape?

The effects of urbanization on bats are poorly understood, but published data suggests it might be detrimental to them. Even though urban parks provide refuge to native biota, the nature of the urban landscape exacerbates the insularization process. In order to evaluate if wooded streets in an urban landscape provide connectivity for bats, we compared bat community structure in three different types of habitats: urban parks, wooded streets and non-wooded streets. Sampling occurred monthly from August 2006 to July 2007 in the city of Vitória, southeastern Brazil. Richness, relative abundance and diversity were higher in urban parks and lower in non-wooded streets. Jaccard’s similarity index showed that the wooded streets are more similar to non-wooded streets than to urban parks. Urbanization may benefit generalist species by providing new resources, but for specialist species critical resources may be lost and persistence endangered. There is evidence that wooded streets may provide some degree of connectivity for birds in urban landscapes, but our results suggest that this is not the case, with wooded streets being used by few individuals of a few species. Vegetation cover is important to maintain bat diversity in urban centers. Activities like landscape planning and gardening should include biodiversity data in their outputs in order to better design a landscape that improves the likelihood of persistence of bats.     

Do plant populations on distinct inselbergs talk to each other? A case study of genetic connectivity of a bromeliad species in an Ocbil landscape

Here, we explore the historical and contemporaneous patterns of connectivity among Encholirium horridum populations located on granitic inselbergs in an Ocbil landscape within the Brazilian Atlantic Forest, using both nuclear and chloroplast microsatellite markers. Beyond to assess the E. horridum population genetic structure, we built species distribution models across four periods (current conditions, mid‐Holocene, Last Glacial Maximum [LGM], and Last Interglacial) and inferred putative dispersal corridors using a least‐cost path analysis to elucidate biogeographic patterns. Overall, high and significant genetic divergence was estimated among populations for both nuclear and plastid DNA (Φ_ST(n) = 0.463 and Φ_ST(plastid) = 0.961, respectively, p < .001). For nuclear genome, almost total absence of genetic admixture among populations and very low migration rates were evident, corroborating with the very low estimates of immigration and emigration rates observed among E. horridum populations. Based on the cpDNA results, putative dispersal routes in Sugar Loaf Land across cycles of climatic fluctuations in the Quaternary period revealed that the populations’ connectivity changed little during those events. Genetic analyses highlighted the low genetic connectivity and long‐term persistence of populations, and the founder effect and genetic drift seemed to have been very important processes that shaped the current diversity and genetic structure observed in both genomes. The genetic singularity of each population clearly shows the need for in situ conservation of all of them.     

Do litter manipulations affect leaf functional traits of savanna woody plants?

Plant litter is the layer composed of dead plant material that covers soil surfaces in terrestrial ecosystems. It is an important pool of essential nutrients for soil and plants, serving also as a protective layer on the soil surface. In this study, we investigated the effects of litter addition and removal on leaf functional traits of woody Neotropical savanna trees. We measured maximum photosynthesis (A _max), stomatal conductance (g _s), leaf transpiration (E), intrinsic water use efficiency (IWUE), specific leaf area (SLA), and chlorophyll content (CCI) in 15 species belonging to three different phenological groups (evergreen, briefly deciduous, and deciduous species) that were subjected to three distinct litter availability treatments (addition, removal, and control plots) in a Neotropical Savanna site in Brazil. Although SLA and CCI differed among phenology groups, they were not affected by the litter treatments. In contrast, when considered at the community level, we found that the availability of litter affected the leaf traits linked with the water status of the plants (E, g _s and IWUE). Plants in the litter removal plots exhibited lower g _s and E (25 % of reduction in comparison with control group) but higher IWUE, while plants in the litter addition plots had a 10 % decrease in IWUE but a 12 % increase in g _s and E compared with plants in control plots. Savanna woody plants responded promptly to litter manipulation by adjusting leaf water loss, which suggests that in the short term, changes in the amount of litter in Cerrado ecosystems can affect the soil water availability to the plant community.     

Is realised connectivity among populations of aquatic fauna predictable from potential connectivity?

1. Effective management of aquatic fauna requires knowledge of the ways in which populations in different catchments and sub‐catchments are connected. A powerful way to estimate this is using genetic markers, which provide information on the average amount of genetic connectivity among populations over generations. Although many studies of genetic connectivity have appeared in the literature, there are innumerable species that have not been studied. 2. This study explores whether it is possible to make broad generalisations about population connectivity, based on readily available information in the form of species life history and architecture of the aquatic habitat. 3. A number of models have been proposed to explain the pattern of connectivity shown by aquatic species with different life‐history characteristics, for example, the stream hierarchy model, Isolation by Distance, the Death Valley Model, the headwater model and panmixia. 4. In this study, we propose a dichotomous key to assign species to different models of potential connectivity. The key is based on a few very simple questions about the life history of the species and the geographical arrangement of study sites. We then assessed the performance of the key with 109 data sets of Australian fish and macroinvertebrates, using genetic data to provide an estimate of realised connectivity. 5. The realised connectivity fitted the proposed potential connectivity model in over 70% of cases, and we suggest this might be a useful initial approach for managers where empirical data are lacking.     

Distance,dams and drift: what structures populations of an endangered,benthic stream fish?

相似文献   

Do annual and perennial populations of an insect-pollinated plant species differ in mating system?

Background and AimsTheory predicts that outcrossing should be more prevalent among perennials than annuals, a pattern confirmed by comparative evidence from diverse angiosperm families. However, intraspecific comparisons between annual and perennial populations are few because such variation is uncommon among flowering plants. Here, we test the hypothesis that perennial populations outcross more than annual populations by investigating Incarvillea sinensis, a wide-ranging insect-pollinated herb native to China. The occurrence of both allopatric and sympatric populations allows us to examine the stability of mating system differences between life histories under varying ecological conditions.MethodsWe estimated outcrossing rates and biparental inbreeding in 16 allopatric and five sympatric populations in which both life histories coexisted using 20 microsatellite loci. In each population we measured height, branch number, corolla size, tube length and herkogamy for ~30 individuals. In a sympatric population, we recorded daily flower number, pollinator visitation and the fruit and seed set of annual and perennial plants.Key ResultsAs predicted, outcrossing rates (t) were considerably higher in perennial (mean = 0.76) than annual (mean = 0.09) populations. This difference in mating system was also maintained at sympatric sites where plants grew intermixed. In both allopatric and sympatric populations the degree of herkogamy was consistently larger in outcrossing than selfing plants. Perennials were more branched, with more and larger flowers than in annuals. In a sympatric population, annuals had a significantly higher fruit and seed set than perennials.ConclusionsGenetically based differences in herkogamy between annuals and perennials appear to play a key role in governing outcrossing rates in populations, regardless of variation in local ecological conditions. The maintenance of mating system and life history trait differentiation between perennial and annual populations of I. sinensis probably results from correlated evolution in response to local environmental conditions.     

Do damselfly larvae recognize and differentially respond to distinct categories of macroinvertebrates?

Zygopteran larvae normally encounter other aquatic macroinvertebrates that are predators, competitors, and prey and should therefore demonstrate varied responses when faced with different categories of opponent. In a laboratory experiment individual final-instarIschnura posita (Hagen) larvae were observed in interactions with six categories of invertebrate opponents. The opponent categories were a nonconspecific damselfly and a small crayfish, which represented threatening opponents because they were larger than theI. posita subject larva, and a mayfly and a stonefly, which constituted nonthreatening opponents because they were smaller than the subject larva. The levels of threat posed by conspecific larvae of final and penultimate instar were inferred by comparison to the other opponent categories. Multivariate analysis showedI. posita's response differed between the two larger opponents, but responses were statistically indistinguishable between the two smaller opponents. Larvae retreated, moved around the stalk, and struck their opponents with their lamellae more often in the presence of a crayfish than the nonconspecific zygopteran. In contrast, they assumed an S-bend posture frequently with the zygopteran. Responses toward final-instar conspecifics differed from responses toward the larger opponents. Effectively, larvae wagged their abdomens only in the presence of final-instar conspecifics and retreated and moved around the stalk less frequently in these trials. Responses toward the smaller conspecifics differed from the responses to the small opponents. Larvae struck penultimate-instar conspecifics with their lamellae more frequently than the other small opponents. Our results suggest that larval zygopteran behaviors (such as S-bend and SCS) that have previously been described as intraspecific displays are of a more general nature and used toward a variety of opponents, whereas wag is unique to intraspecific interactions inI. posita.     

Do mountain hare populations cycle?

We investigated the occurrence and distribution of multi-annual cycles in abundance of mountain hare populations across a wide area of their range in northern Europe. We analysed 125 time-series of mountain hare abundance indexed from hunting bag records and questionnaire responses from Scotland, Sweden, Finland and Switzerland. We also reanalysed 17 previously published time-series based on hunting bag records and snow track indices from mountain hare populations in Scotland, Norway, Sweden, Finland, Russia and Italy. Autocorrelation analysis showed that 45% of mountain hare populations showed evidence of cycles, characterised by significant negative autocorrelations at half or the whole cycle period. The amplitude and periodicity of cycles varied between and within countries. Time-series in Scotland were characterised by high-amplitude weak cycles with a mean periodicity of nine years but with a range of 4–15 years. Norwegian and Swedish time-series revealed low amplitude weak cycles with a 3–7 year period. Finnish time-series showed low amplitude cycles with a 4–11 year period. Alpine time-series were predominantly non-cyclic, while the limited number of series from Russia showed high amplitude weak cycles with an 8–11 year period. The results reveal that mountain hare populations show a wide range of population dynamics with distinct regional differences in periodicity, amplitude and density dependent structure of cycles. These findings suggest that different factors may limit or regulate mountain hare populations in different regions of Europe thus supporting the results of recent field studies.     

Do earthworms affect dynamics of functional response and genetic structure of microbial community in a lab-scale composting system?

Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicomposting (with earthworms) and were monitored for 60 days after pre-composting. The physico-chemical parameters (pH, C/N, organic matter, NH(4)(+)-N and ash content) showed similar evolution in both systems except a higher NH(4)(+)-N in the initial vermicomposts. However, principle component analysis (PCA) of enzymatic activities and community level physiological profiles revealed differences in the functional response of microbial communities in compost and vermicompost during maturation. Dehydrogenase activity and bacterial counts indicated a steady decrease in biological activity and population during composting, whereas vermicomposting exhibited higher activity on day 30 and a reduction in bacterial counts on day 10. PCA of denatured gradient gel electrophoresis (DGGE) profiles showed divergent dynamics of bacterial communities in two processes. These results indicated differences in the functional response and genetic structure of microbial community in composts and vermicomposts despite similar changes in their physico-chemical parameters.     

What causes male‐biased sex ratios in mature damselfly populations?

1. Several hypotheses to account for biased sex ratios in mature insect populations were tested by monitoring two field populations of the damselfly Lestes sponsa and by performing experiments in field cages. The population sex ratios are heavily male biased in this species. 2. The observed sex ratio at emergence was even and both sexes emerged synchronously. Females had longer maturation times but these were insufficient to explain the observed sex ratio shift. 3. Mass increases during maturation were consistently larger in females. In agreement with this, immature females made more flights per unit of time, which should make them more vulnerable to predation, however maturation probabilities were lower in females only in one field cage experiment. This inconsistency may be due to long bad weather conditions. Interestingly, predators reduced mass increase and this reduction was larger in females than in males. 4. Calculations based on the sex specific maturation times show that only slightly lower daily survival probabilities during maturation in females are enough to generate the observed sex ratio shift. 5. Mature survival was higher in males than in females in one field population but not in another, indicating that this cannot be a general mechanism causing the sex ratio. A higher maturation probability in males is therefore the most plausible mechanism causing the sex ratio shift in damselfly populations.     

Do leaf-litter attributes affect the richness of leaf-litter ants?

The search for factors shaping leaf-litter ant communities has received particular attention due to the essential role of these insects in many ecological processes. Here, we aimed to investigate how the number of leaves and leaf morphotypes affect the litter-ant species density at forest edge and interior in an Atlantic Forest remnant in the state of Alagoas, Brazil. This study was developed based on 28 litter plots (1m2 each), 14 in the forest interior and 14 in the forest edge. As we early expected, ant species density increased with increasing both the number of leaves and the number of leaf morphotypes, but this result was clearly influenced by plot location. Contrasting with the forest interior, ant species density did not increase as the number of leaves increased in the forest edge. Possibly, factors such as plant species richness, vegetation structure and environmental conditions affect ant species density as well as promote a patchy distribution of species in ant communities along the edge-to-interior gradient. Our findings suggest that edge-affected forests present more simplified ant communities, with different factors shaping its structure. We encourage future studies to include leaf litter heterogeneity as one of the explanatory variables investigated.     

Do local communities support the conservation of endangered Przewalski’s gazelle?

Understanding local attitudes and opinion is vital to the success of conservation programs, especially in areas of expanding human populations such as China. Przewalski’s gazelle (Procapra przewalskii) is an endangered ungulate found only in the eastern part of the Qinghai-Tibet Plateau. The gazelle is a conservation focus; however, little is known regarding how this animal is perceived by local people. To understand the relationship between demography, levels of conservation knowledge, and attitudes, we conducted 174 interviewer-led surveys in villages located inside, near, and away from the gazelle’s home ranges around Qinghai Lake, China. About half of the interviewees were aware of gazelle conservation. No more than half of the interviewees were aware that grassland fence, livestock, roads, and wolves negatively impact upon gazelle. On the whole, the majority of interviewees supported the conservation of gazelle. There were high levels of support for both establishing a special protected area and investing more funds in conservation but very few interviewees reported personal benefits from gazelle conservation. Overall attitude of interviewees toward the gazelle differed significantly among regions and people living near the range of gazelle were the most positive. Interviewees with conservation information were more positive than interviewees lacking such information. People who had more education or possessed more grassland had more positive attitudes toward the gazelle. This study suggests that greater communication is needed with local people. Programs that promote public engagement and participation are required for the conservation of Przewalski’s gazelle and other larger herbivores on the Qinghai-Tibet Plateau.     

Does microclimate affect grasshopper populations after cutting of hay in improved grassland?

The microclimate of an improved hay meadow was studied using Tinytag dataloggers to record sward temperature after cutting. Temperatures in the sward were then compared to grasshopper abundances to see if mowing created an excessively hot microclimate unfavourable for sustained grasshopper activity in mid summer. The abundance of Chorthippus albomarginatus and Chorthippus parallelus was significantly reduced on the hay plots compared to the unmanaged control swards, which may have been due to high sward temperatures created by the absence of tall, shady vegetation in which grasshoppers may take refuge to avoid overheating. This study suggests that a combination of mortality caused by the physical process of mowing, and high sward temperatures created by removal of the standing crop by cutting may cause the low abundance of grasshoppers in improved grassland in eastern England. This research is particularly important when considering the orthopteran assemblages of Environmental Stewardship Scheme field margins where mowing for hay in July and August may seriously reduce grasshopper populations. If mowing of grassland has to occur during the grasshopper season, we suggest a later cut in September or a system of rotational mowing, leaving areas of uncut grassland as shelter.     

Do competitive intraguild interactions affect space and habitat use by small carnivores in a forested landscape?

Complex interactions such as interference competition and predation, including intraguild predation, are now recognized as important components in animal community structure. At the lower end of a guild, weasels may be highly affected by other guild members due to small body size in relation to other predators. In 2000 and 2001, we radio-collared 24 ermines Mustela erminea and 25 long-tailed weasels M. frenata in 2 areas that differed in abundance of guild members. We tested the hypothesis that when faced with an increased density of other guild members, weasels would modify space and habitat use to reduce the risk of predation associated with encounters involving guild members. We predicted that weasels would increase use of specific habitats (such as refuges) to reduce encounter rates in the presence of a greater number of guild members. Because M. erminea is smaller than M. frenata and thus better able to take advantage of small rodent burrows as refuges from predators and as feeding grounds, we also predicted that M. frenata would show a stronger response to a higher abundance of guild members than M. erminea . Results were consistent with our predictions. Faced with an increased abundance of guild members, M. frenata showed increased habitat selectivity and reduced activity levels, which resulted in increased daily travel distances and increased home ranges. Mustela erminea responded to an increased abundance of guild members through reduced use of preferred habitat which M. frenata already occupied. The contrasting pattern of habitat selection observed between the 2 mustelid species suggested cascading effects, whereby large-predator pressure on M. frenata relaxed pressure of M. frenata on M. erminea . Our results draw attention to the likelihood that competitive intraguild interactions play a facilitating role in M. erminea – M. frenata coexistence.     

Distribution of recreational boating across lakes: do landscape variables affect recreational use?

1. Because people impact lake ecosystems, it is important to consider factors influencing the human use of freshwater resources. We investigated the influence of the landscape position, as well as lake area, recreational facilities, and distance to highways and urban centres, on lake use by boaters in the Northern Highland Lake District of Wisconsin, U.S.A.
2. In aerial surveys of ninety-nine randomly selected lakes, we did not see boats on over half of the lakes. Of the lakes with boats, we found a strong correlation between the number of boats and lake area. Recreational boats tended to be found on large, accessible lakes with good boating facilities. Boats were not seen on small, stained lakes with few recreational facilities.
3. Regression models showed that lake size and landscape position explained 63% of the variability in the average number of boats per lake and landscape position explained 24% of the variability in boat density on all ninety-nine lakes. Social variables representing the quality of boating facilities and the perception of good fishing explained 70% of the variability in number of boats per lake and 54% of the variation in boat density on all lakes. A combined model using both physical and social variables increased the explanatory power for both number and density. Lake use by boaters was correlated with landscape position, the quality of fishing and the availability of recreational facilities. When the analysis was restricted to the forty-six lakes where boats were found, only the availability of recreational facilities proved a significant predictor of boat density.
4. Our results suggest that lake choice by recreational boaters may be best predicted by a combination of the location of a lake in a regional hydrologic landscape, and considerations of available facilities and perceptions regarding fishing.