Contrasting home-range size and spatial partitioning in cryptic and sympatric pipistrelle bats

The extent of spatial partitioning in insectivorous bats, whose prey is patchily distributed and transient in nature, remains a contentious issue. The recent separation of a common Palaearctic bat, the pipistrelle, into Pipistrellus pipistrellus and Pipistrellus pygmaeus, which are morphologically similar and sympatric, provides an opportunity to examine this question. The present study used radio telemetry to address the spatial distribution and foraging characteristics of P. pipistrellus and P. pygmaeus in northeast Scotland, to test the hypothesis that coexistence between these species is facilitated through spatial segregation. We reveal large and significant differences in the spatial distribution and foraging characteristics of these two cryptic species. Individual P. pipistrellus home ranges were on average three times as large as that of P. pygmaeus, and they foraged for approximately an hour longer each night. Inter-specific spatial overlap was minimal (<5%) and core foraging areas of either species were essentially mutually exclusive despite the proximity of the two roosts. Inter-specific differences in range size were associated with the spatial dispersion of productive foraging sites within individual foraging ranges. P. pipistrellus foraging sites were highly dispersed, necessitating larger ranges. It is predicted that the spatial segregation revealed by the present study is a result of selection favouring the avoidance of competition in these species through differential habitat use.     

Contrasting structure and composition of the understory in species-rich tropical rain forests

In large samples of trees > or = 1 cm dbh (more than 1 million trees and 3000 species), in six lowland tropical forests on three continents, we assigned species with >30 individuals to one of six classes of stature at maturity (SAM). We then compared the proportional representation of understory trees (1-2 cm dbh) among these classes. The understory of the three Asian sites was predominantly composed of the saplings of large-canopy trees whereas the African and American sites were more richly stocked with trees of the smaller SAM classes. Differences in class representation were related to taxonomic families that were present exclusively in one continent or another. Families found in the Asian plots but not in the American plot (e.g., Dipterocarpaceae, Fagaceae) were predominantly species of the largest SAM classes, whereas families exclusive to the American plots (e.g., Melastomataceae sensu stricto, Piperaceae, and Malvaceae [Bombacacoidea]) were predominantly species of small classes. The African plot was similar to Asia in the absence of those American families rich in understory species, while similar to America in lacking the Asian families rich in canopy species. The numerous understory species of Africa were chiefly derived from families shared with Asia and/or America. The ratio of saplings (1-2 cm dbh) to conspecific canopy trees (>40 cm dbh) was lower in American plots than in the Asian plots. Possible explanations for these differences include phenology, moisture and soil fertility regimes, phyletic constraints, and the role of early successional plants in forest development. These results demonstrate that tropical forests that appear similar in tree number, basal area, and the family taxonomy of canopy trees nonetheless differ in ecological structure in ways that may impact the ecology of pollinators, dispersers, and herbivores and might reflect fundamental differences in canopy tree regeneration.     

Riparian shading and groundwater enhance growth potential for smallmouth bass in Ozark streams.

Moderation of stream temperatures by riparian shading and groundwater are known to promote growth and survival of salmonid fishes, but effects of riparian shade and groundwater on to be growth of warmwater stream fishes are poorly understood or assumed to be negligible. We used stream temperature models to relate shading from riparian vegetation and groundwater inflow to summer water temperatures in Missouri Ozark streams and evaluated effects of summer water temperatures on smallmouth bass, Micropterus dolomieu, growth using a bioenergetics model. Bioenergetics model simulations revealed that adult smallmouth bass in non-spring-fed streams have lower growth potential during summer than fish in spring-fed streams, are subject to mass loss when stream temperatures exceed 27 degrees C, and will likely exhibit greater interannual variation in growth during summer if all growth-influencing factors, other than temperature, are identical between the two stream types. Temperature models indicated that increased riparian shading will expand the longitudinal extent of thermal habitat capable of supporting adult smallmouth bass growth in spring-fed stream reaches when mean daily air temperatures exceed 27 degrees C. Optimum growth temperature (22 degrees C) will be present only in spring-fed streams under these conditions. Potential for increasing shade through riparian restoration is greatest for streams <5 m wide and along north-south reaches of larger streams. However, temperature models also indicated that restoring riparian shading to maximum levels throughout a watershed would increase the total stream mileage capable of supporting positive growth of adult smallmouth bass by only 1-6% when air temperatures are at or near average summer maxima; increases in suitable thermal habitat would be greatest in watersheds with higher spring densities. Riparian management for maintenance or restoration of the thermal habitat of adult smallmouth bass during summer should be focused in areas strongly influenced by groundwater. Restoring riparian shading along spring-fed warmwater streams will likely benefit adult smallmouth bass growth and may ultimately influence population sizes.     

Human impacts, plant invasion, and imperiled plant species in California.

Invasive species are one of the fastest growing conservation problems. These species homogenize the world's flora and fauna, threaten rare and endemic species, and impose large economic costs. Here, we examine the distribution of 834 of the more than 1000 exotic plant taxa that have become established in California, USA. Total species richness increases with net primary productivity; however, the exotic flora is richest in low-lying coastal sites that harbor large numbers of imperiled species, while native diversity is highest in areas with high mean elevation. Weedy and invasive exotics are more tightly linked to the distribution of imperiled species than the overall pool of exotic species. Structural equation modeling suggests that while human activities, such as urbanization and agriculture, facilitate the initial invasion by exotic plants, exotics spread ahead of the front of human development into areas with high numbers of threatened native plants. The range sizes of exotic taxa are an order of magnitude smaller than for comparable native taxa. The current small range size of exotic species implies that California has a significant "invasion debt" that will be paid as exotic plants expand their range and spread throughout the state.     

Simulation of germination of pioneer species along an experimental drought gradient

The germination of ten plant species from the Iberian Peninsula was assessed along a water deficit gradient between -0. 1652 (moist) and -0.4988 MPa (dry) of osmotic potential, created by addition of increasing concentrations of polyethylene glycol (PEG 6000) to distilled water in which plants were grown hydroponically. The level and rate of germination of Daucus carota and Thapsia villosa significantly decreased with decreasing psi. Seeds of Dactylis glomerata and Dittrichia viscosa had positive germination responses to low osmotic potentials; germination of Epilobium hirsutum was not affected by osmotic potential. Germination of Medicago arabica, Cynosurus cristatus, Cistus ladanifer and Cistus albidus, was no favored by the addition of polyethylene glycol (PEG). Germination of Foeniculum vulgare and Thapsia villosa was inhibited by PEG.     

Inhibition of Amazon Deforestation and Fire by Parks and Indigenous Lands

Abstract:  Conservation scientists generally agree that many types of protected areas will be needed to protect tropical forests. But little is known of the comparative performance of inhabited and uninhabited reserves in slowing the most extreme form of forest disturbance: conversion to agriculture. We used satellite-based maps of land cover and fire occurrence in the Brazilian Amazon to compare the performance of large (>10,000 ha) uninhabited (parks) and inhabited (indigenous lands, extractive reserves, and national forests) reserves. Reserves significantly reduced both deforestation and fire. Deforestation was 1.7 (extractive reserves) to 20 (parks) times higher along the outside versus the inside of the reserve perimeters and fire occurrence was 4 (indigenous lands) to 9 (national forests) times higher. No strong difference in the inhibition of deforestation ( p = 0.11) or fire ( p = 0.34) was found between parks and indigenous lands. However, uninhabited reserves tended to be located away from areas of high deforestation and burning rates. In contrast, indigenous lands were often created in response to frontier expansion, and many prevented deforestation completely despite high rates of deforestation along their boundaries. The inhibitory effect of indigenous lands on deforestation was strong after centuries of contact with the national society and was not correlated with indigenous population density. Indigenous lands occupy one-fifth of the Brazilian Amazon—five times the area under protection in parks—and are currently the most important barrier to Amazon deforestation. As the protected-area network expands from 36% to 41% of the Brazilian Amazon over the coming years, the greatest challenge will be successful reserve implementation in high-risk areas of frontier expansion as indigenous lands are strengthened. This success will depend on a broad base of political support.     

Ecological-Economic Modeling for Biodiversity Management: Potential, Pitfalls, and Prospects

Abstract:  Ecologists and economists both use models to help develop strategies for biodiversity management. The practical use of disciplinary models, however, can be limited because ecological models tend not to address the socioeconomic dimension of biodiversity management, whereas economic models tend to neglect the ecological dimension. Given these shortcomings of disciplinary models, there is a necessity to combine ecological and economic knowledge into ecological-economic models. It is insufficient if scientists work separately in their own disciplines and combine their knowledge only when it comes to formulating management recommendations. Such an approach does not capture feedback loops between the ecological and the socioeconomic systems. Furthermore, each discipline poses the management problem in its own way and comes up with its own most appropriate solution. These disciplinary solutions, however, are likely to be so different that a combined solution considering aspects of both disciplines cannot be found. Preconditions for a successful model-based integration of ecology and economics include (1) an in-depth knowledge of the two disciplines, (2) the adequate identification and framing of the problem to be investigated, and (3) a common understanding between economists and ecologists of modeling and scale. To further advance ecological-economic modeling the development of common benchmarks, quality controls, and refereeing standards for ecological-economic models is desirable.     

In situ experiment of ontogenetic variability in the otolith chemistry of Stegastes partitus

Otolith chemistry can be used to assess pelagic larval fish connectivity by comparing spatially variable otolith edge chemistry (corresponding to the site of collection) to otolith core chemistry (corresponding to the site of hatching). However, because the otolith’s edge and core represent different life stages, the deposition of elements may differ, thus complicating direct comparisons of edge and core chemistry to investigate connectivity. Here we present data from a field experiment in which otoliths from embryos (3 days post-fertilization) and juveniles of Stegastes partitus were collected at the same site and time, and chemically analyzed to assess whether elemental concentrations of otoliths vary ontogenetically. Separate multivariate analyses, each investigating the spatial/temporal variability in the chemistry of either embryo otoliths or the edges of juvenile otoliths, revealed significant differences, suggesting an environmental influence to the chemical signals of otoliths. A nested multivariate analysis assessing whether otolith chemistry varied with life history stage (i.e., ontogenetic variability) indicated that elemental concentrations of embryo otoliths were significantly greater than that of juvenile otolith edges. Specifically, embryo elemental concentrations of Mn, Zn, Sn, Ba, Ce, and Pb were between 2 and 163 times greater than those of the corresponding juvenile otoliths, and thus the environment was not the primary determinant of embryo otolith chemistry. Consequently, caution is warranted when interpreting environmental patterns of otolith cores, particularly when using them as a proxy for natal signatures.