Extension of twoCaulerpa species along the Tunisian coast

Two species of the green alga genusCaulerpa are considered as invasive in Tunisia:Caulerpa racemosa andC. taxifolia. C. racemosa is found in a many new localities at the central and southern Tunisian coast, and even in the North of the country in colder water. These new observations lead to the hypothesis of the multiplicity of the origins of the introduction of the species and suggest possible invasive potentialities. The general thallus, and more particularly the number, the shape as well as the arrangement of ramelli on fronds allowed us to identify four morphologically different groups. These groups could be either different systematic entities or polymorphic variations of the same taxon due to different ecological conditions.Caulerpa taxifolia was observed for the first time in Tunisia at the roadstead of Sousse in the beginning of the year 2000. It is recognized as identical to that found in the other Mediterranean localities (GenBank number AJ228960). Up to the end of March 2000, a submarine prospecting campaign revealed an affected area of about 350 ha in front of 2 km of coast. Colonies ofCaulerpa taxifolia disseminating in this area appear in isolated spots. form, In the growing stage, they form surfaces varying between 0.5 to 6 m² and located 20 to 100 m from each other. The total covered surface was estimated to be between 0.5 and 1 ha.     

Conservation of Vascular Epiphyte Diversity in Mexican Coffee Plantations

Abstract:  Coffee plantations have replaced many lower-montane forests in the Neotropics, and ongoing intensification is converting traditional polycultures with a variety of shade trees to plantations with no or monospecific shade trees. To evaluate the impact of coffee cultivation on epiphyte diversity, I surveyed vascular epiphytes on shade trees in nine different coffee plantations and compared records with those in four natural forests in central Veracruz, Mexico. Eighty-nine species occurred in coffee plantations, and 104 species occurred in natural forests. The number of epiphytic species in traditional polycultures with old shade trees, mostly of the genus Inga , was similar to that in forests, but plantations with small trees and sparse shade hosted fewer epiphytes than those with large trees. Epiphyte communities were, however, more homogeneous in coffee plantations than in forests, possibly because of a drier microclimate and the lack of large and long-lived trees. These results demonstrate the value of traditional polycultures for epiphyte diversity, show the importance of conserving large shade trees, and suggest that these coffee systems may not be suitable for all epiphytes.     

The Value of Biodiversity in Reserve Selection: Representation, Species Weighting, and Benefit Functions

Abstract:  The limited availability of resources for conservation has led to the development of many quantitative methods for selecting reserves that aim to maximize the biodiversity value of reserve networks. In published analyses, species are often considered equal, although some are in much greater need of protection than others. Furthermore, representation is usually treated as a threshold: a species is either represented or not, but varying levels of representation over or under a given target level are not valued differently. We propose that a higher representation level should also have higher value. We introduce a framework for reserve selection that includes species weights and benefit functions for under- and overrepresentation (number of locations for each species). We applied the method to conservation planning for herb-rich forests in southern Finland. Our use of benefit functions and weighting changed the identity of about 50% of the selected sites at different funding levels and improved the representation of rare and threatened species. We also identified a small area of additional land that would substantially enhance the existing reserve network. We suggest that benefit functions and species weighting should be considered as standard options in reserve-selection applications.     

Use of Substitute Species in Conservation Biology

Abstract:  In conservation biology, researchers often want to study the reasons why an endangered population is faring poorly but are unable to study it directly for logistical or political reasons. Instead they study a species that substitutes for the one of concern in the hope that it will cast light on the conservation problem. Here we outline the assumptions underlying this approach. Substitutes can be different populations or species and may be chosen because they are similar biologically to the target or representatives of a constellation of species of which the target is one. They also may be used to develop a predictive model to which the conservation target can be related. For substitutes to be appropriate, they should share the same key ecological or behavioral traits that make the target sensitive to environmental disturbance and the relationship between population vital rates and level of disturbance should match that of the target. These conditions are unlikely to pertain in most circumstances and the use of substitute species to predict endangered populations' responses to disturbance is questionable.     

贺兰山高山草甸生物多样性和地上生物量的关系

在对贺兰山高山草甸进行群落调查的基础上,研究高山草甸生物多样性和地上生物量与环境因子之间的关系,进而分析生物多样性和地上生物量的关系.结果表明:(1)地上生物量主要与土层深度成正相关关系.(2)海拔高度与生物多样性成负相关关系,而其它影响物种丰富度或Shannon指数的环境因子仅在个别群落类型中起作用.(3)生物多样性与地上生物量主要呈单峰曲线关系.     

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.     

Fire and Green-Tree Retention in Conservation of Red-Listed and Rare Deadwood-Dependent Beetles in Finnish Boreal Forests

Abstract:  Habitat loss, fragmentation, and declining habitat quality have created an extinction debt in boreal forests, which could be partly reversed by deliberately improving the habitat quality in managed areas outside reserves. We studied the effects of green-tree retention and controlled burning on red-listed and rare, deadwood-dependent (saproxylic) beetles in a large-scale field experiment in eastern Finland. Our factorial study design included 24 sites dominated by Scots pine ( Pinus sylvestris L.) and with three levels of green-tree retention (0, 10, and 50 m³/ha) and uncut controls. Twelve of the 24 sites were burned in 2001. We sampled beetles with 10 flight-intercept traps on each site during the years 2000–2002 (i.e., 1 pretreatment and 2 post-treatment years). A total sample of 153,449 individuals representing 1,160 beetle species yielded 2,107 specimens of 84 red-listed or rare saproxylic species. The richness of these species was higher on the burned than on the unburned sites, and higher levels of green-tree retention promoted species richness, but there were clear differences between the years. The richness of red-listed and rare saproxylic species increased in the first post-treatment year, evidently due to the treatments, continued to increase on the burned sites in the second post-treatment year, but decreased on the unburned sites. Our results showed that the living conditions of many red-listed and rare saproxylic species could be improved significantly with rather simple alterations to forest management methods. Controlled burning with high levels of green-tree retention creates resources for many saproxylic species, but increasing the levels of green-tree retention in unburned areas can also be beneficial.     

Recovery of Faunal Communities During Tropical Forest Regeneration

Abstract:  As mature tropical forests are cleared, secondary forests may play an important role in the conservation of animal species, depending on how fast animal communities recover during forest regeneration. I reviewed published studies on the recovery of animal species richness and composition during tropical forest regeneration. In 38 of the 39 data sets I examined, conversion of forest to agriculture or pasture substantially reduced species richness. Given suitable conditions for forest recovery, the species richness of the animal taxa considered can be predicted to resemble that of mature forests roughly 20–40 years after land abandonment. At least for ants and birds, however, recovery of species composition appears to take substantially longer than recovery of species richness. Because species richness for many taxa appears to recover relatively rapidly in secondary forests, conservation of secondary forests may be an effective investment in future diversity. The slower recovery of species composition indicates, however, that some species will require stands of mature forest to persist.     

Effect of Invasive Plant Species on Temperate Wetland Plant Diversity

Abstract:  Invasive species are a major threat to global biodiversity and an important cause of biotic homogenization of ecosystems. Exotic plants have been identified as a particular concern because of the widely held belief that they competitively exclude native plant species. We examined the correlation between native and invasive species richness in 58 Ontario inland wetlands. The relationship between exotic and native species richness was positive even when we controlled for important covarying factors. In addition, we examined the relationship between the abundance of four native species (  Typha latifolia, T. angustifolia, Salix petiolaris, Nuphar variegatum ) and four invasive species (  Lythrum salicaria, Hydrocharis morsus-ranae, Phalaris arundinacea, Rhamnus frangula ) that often dominate temperate wetlands and native and rare native species richness. Exotic species were no more likely to dominate a wetland than native species, and the proportion of dominant exotic species that had a significant negative effect on the native plant community was the same as the proportion of native species with a significant negative effect. We conclude that the key to conservation of inland wetland biodiversity is to discourage the spread of community dominants, regardless of geographical origin.