Flora and lepidoptera fauna adversely affected by invasive Lupinus polyphyllus along road verges

An increasing number of invasive species are changing ecosystems around the world. Road verges have commonly become the first footholds of non-native species in the new environments. Regularly mown road verges also offer habitats for meadow flora and fauna, which in Europe have suffered from the radical decline of semi-natural biotopes due to the agricultural modernization. We studied impacts of an invasive plant Lupinus polyphyllus on the plant and Lepidoptera species composition along road verges. The plant species composition was studied on 15 sites (with 1 m² quadrats) and butterflies and diurnal moths along 15 transects (with weekly censuses) in SE Finland, each site and transect representing equally lupine invaded verge and an adjacent non-lupine verge. The species richness and diversity of flora and the cover and species richness of low growing (<20 cm) species, in particular, was lower in lupine verges compared to non-lupine verges. Also, the abundance of butterflies was lower in lupine verges. As the lupine cover approached 100%, fewer butterflies were observed in lupine transects compared to the adjacent non-lupine transects and a higher proportion of individuals were flying. Our results suggest that the changes in plant species assemblages and lower plant species richness in lupine invaded areas had “bottom-up” effects on higher trophic levels. Further studies on the control of lupine are urgently needed, but meanwhile we suggest regular mowing before the lupines have shed their seeds, together with the removal of the cuttings, to be the best management option.     

Butterflies and diurnal moths along road verges: Does road type affect diversity and abundance?

Roadsides form potential habitats for several grassland species adapted to regular mowing management. We studied the communities of butterflies and day-active moths in 51 sites along the verges of the three road types, i.e., highways, urban roads and rural roads. Despite different traffic densities and widths of the road and verge, the groups were rather similar with regard to soil properties, vegetation structure and mowing intensity. The species richness and total abundance of butterflies (53 species, 5964 individuals) and diurnal moths (46 species, 4626 individuals) were also rather similar in each road type, although a preference for wider verges was observed. Butterfly diversity increased (but not significantly) from the verges of narrow rural roads to wider highways. The highest numbers of meadow species were recorded along highways and the total abundance, especially of diurnal moths, decreased in accordance with the road size. High nectar abundance was the most important factor increasing the numbers of meadow butterflies along road verges, while meadow moths were mostly favoured by shelter provided by tall vegetation. Verges surrounded by cultivated fields were generally related to low numbers of both Lepidoptera groups, whereas adjacent forests increased the total number of all species and favoured several butterflies inhabiting forest edges. The adjacent environment inflicted compositional differences on the Lepidoptera fauna of the three road types. The results indicate that road verges should be considered an important reserve for species dependent on semi-natural grasslands in Finland. A growing interest in accommodating current roadside management for conserving biodiversity is likely to benefit Lepidoptera communities in the verge habitats.     

Butterfly distribution and abundance is affected by variation in the Swedish forest-farmland landscape

Remaining patches of semi-natural grasslands are hot spots for biodiversity in modern agricultural landscapes. In Sweden semi-natural pastures cover approximately 500,000 ha. However, power-line corridors, road verges and clear-cuts cover larger areas (in total about 2,000,000 ha), and these open, less intensively managed habitats are potentially important for species associated with taller vegetation and flower resources (e.g. pollinating insects). The aim of the present study was to evaluate the relative importance of semi-natural pastures and the other three open habitats for butterflies in 12 forest-farmland mosaic landscapes in south central Sweden. Species composition differed significantly between habitats in multivariate analyses. Power-line corridors and semi-natural pastures harbored several species that were disproportionally abundant in these habitats (13 and 8 species, respectively), and power-line corridors also harbored several species that were classified as typical in indicator species analyses. There were more butterfly species, higher abundances and a tendency for more individuals of red-listed species in power-line corridors than in the other three habitats. Effects of the surrounding landscape composition seemed to be weaker than that of the local habitat. However, species composition was significantly associated with landscape composition and species with intermediate and low mobility were more abundant in forested landscapes than in landscapes dominated by arable fields. Analyses of flying time and host plants for larvae suggest that early flying species and species associated with dwarf shrubs were more common in power-line corridors than in the other habitats. A landscape perspective, which takes several habitats into account, is needed for conservation of butterfly communities in forest-farmland landscapes. Power-line corridors and road verges offer possibilities for creating habitats that are suitable for pollinating insects through conservation-oriented management.     

Plant species richness in midfield islets and road verges - The effect of landscape fragmentation

Small marginal habitats in the rural landscape may play an important role for plant species richness as refugias. Little is known how the surrounding landscape and landscape history influence these patterns. I analysed how plant species richness was affected by isolation, habitat area, past and present land use, and if landscape context matters. Plant species occurrence in two different types of small marginal habitats were analysed, road verges and midfield islets. The study was conducted in two different agricultural landscapes in Sweden; one open modern agricultural landscape and one traditional rural landscape, and the results compared. Present and past land use, and landscape change was analysed using aerial photographs and old maps. There was a large grassland reduction more than 50 years ago in the modern landscape, when there still were quite a lot of grasslands left in the traditional landscape. Area and connectivity were more important for plant incidence in small remnant habitats in the modern landscape, compared to the less fragmented, traditional rural landscape. On the other hand there were more grassland specialists, 23% in the traditional landscape compared to 16%. Species richness became higher on midfield islet if grazing was re-introduced. The legacy of surrounding landscape remains in the species pool for a long time, atleast 50 years, even in small grassland fragments. Although small grassland remnants are more sensitive to fragmentation effects compared to larger grasslands, they still encompass a substantial part of the grassland species pool and may be valuable for reconstructing grassland management at a landscape scale.     

Post-fledging dispersal, habitat use, and survival of Sprague’s pipits: Are planted grasslands a good substitute for native?

Loss and degradation of native grasslands on the North American landscape are some of the key factors influencing population declines of grassland songbirds. It is unclear what role anthropogenic grasslands play in the conservation of grassland specialists and whether demographic parameters of grassland songbirds differ between anthropogenic and native grasslands. Furthermore, there has been little research examining the overlap (or lack thereof) between nesting and post-fledging habitat. We initiated a radio-telemetry study from 2004 to 2008 on dispersal, microhabitat use, and survival of juvenile Sprague’s pipits (Anthus spragueii), a threatened grassland-obligate songbird, in native pastures and fields planted with exotic species (planted grasslands). Dispersal distance was greater in planted compared to native grasslands, but appeared to be constrained to natal fields up to 26-d post-fledging. Pipits used microhabitats in planted grasslands with vegetation that was on average 11 cm taller than used locations in native pastures, possibly due to the rapid growth of planted vegetation by the time individuals fledged. Individuals that were reared in planted grasslands had consistently lower daily survival rates compared to those in native pastures. Our observation that young birds rarely left their natal field suggests that conserving nesting habitat in native pastures would be an effective management strategy for this species. However, our results suggest that planted grasslands may act as population sinks given the lower survival of juvenile pipits reared in planted fields in our region. Demographic studies during the post-fledging period are essential to determine the conservation value of anthropogenic grasslands for North American songbirds.     

Modelling the influence of seasonal inter-habitat movements by an ecotone rodent

I assessed the long-term effects of seasonal inter-habitat movements for a common rodent, Microtus californicus, using matrix models tailored to demographic data obtained on populations living at the marsh-grassland ecotone. Three stochastic models were used to simulate the seasonal and spatial dynamics of this system, with the purpose of determining: (1) the growth rates of populations living in single versus a two-habitat landscape; and (2) if the amount, direction, and seasonality of rodent movements between the two habitats may impact these growth rates. The results indicated that grassland populations could be self-sustaining, but that isolated marsh populations would rapidly decline. Importantly, 98% of the two-habitat simulations yielded growth rates greater than those seen in the grassland model, with populations benefiting the most by movements from marsh into grassland at the end of the dry season. This study demonstrated that movements between marsh ‘sink’ and grassland ‘source’ habitats can potentially increase long-term population growth due to seasonal, inter-habitat differences in resource availability.     

Avian community response to vegetation and structural features in grasslands managed with fire and grazing

This study examined the importance of natural and manmade structural features on the avian community relative to management-induced vegetation dynamics. The study was conducted within the context of two alternative vegetation management treatments applied to pastures on a tallgrass prairie site in northcentral Oklahoma from 2001 to 2003. The brown-headed cowbird, a brood parasite, and the grasshopper sparrow, a common grassland obligate species, were most abundant in areas managed under a traditional treatment in which entire pastures were annually burned. Conversely, Henslow’s sparrow, a grassland obligate of conservation concern, was completely absent from traditional treatment pastures. Total bird species diversity and grassland obligate richness was highest in the patch-burn treatment, in which only discrete portions of each pasture were burned each year to create a mosaic of vegetation ‘patches’ in various stages of recovery from disturbance. Models of bird abundance reflected not only species-specific vegetation preferences, but also the often negative influence of structural features such as woody edges, roads, and ponds on breeding bird use of grasslands. Our study demonstrated that both disturbance-derived vegetation attributes and structural features contribute to heterogeneity and influence subsequent use by and composition of grassland bird communities.     

Plant and spider communities benefit differently from the presence of planted hedgerows in highway verges

Road verges should play a crucial role as a refuge for native flora and fauna in human dominated landscapes. However, the influence of construction choices, such as plantation of woody species, on the biodiversity supported by roadsides has received little attention, although the presence of hedgerows in roadsides is likely to enhance their role as a refuge, notably for woodland species. Using standardised methods, we assessed the impact of planted hedgerows on two taxonomic groups (plants and spiders) inhabiting highway verges within an intensive agricultural landscape. We examined community richness, taxonomic and functional composition in sites with and without planted hedgerows. At the site level, the response of plant and spider communities to the presence of planted hedgerows differed markedly: hedgerows were associated with significantly higher plant richness (higher α-diversity), but similar spider richness. Plant communities in sites without hedgerows appeared as a subset of communities in sites with hedgerows, whereas spider communities in non-planted sites were complementary to that of planted sites (increased β-diversity). The presence of planted hedgerows was also associated with increased taxonomic and functional trait diversity at the landscape level (γ-diversity), through an increased β-diversity in both plants and spiders. Our results thus suggest that a mosaic of planted hedgerows and grassland habitats is crucial for the maintenance of biodiversity at a landscape scale. By providing information for road practitioners and policy makers regarding their potential impact on biodiversity, these results have important direct implications for the management of road networks.     

Changes in agricultural management drive the diversity of Burkholderia species isolated from soil on PCAT medium

In order to assess the diversity of culturable Burkholderia populations in rhizosphere and bulk soil and to evaluate how different agricultural management regimes and land use history affect this diversity, four treatments were evaluated: permanent grassland; grassland converted into maize monoculture; arable land and arable land converted into grassland. Burkholderia isolates obtained on PCAT medium were grouped in 47 clusters using 16S ribosomal RNA gene based PCR-DGGE combined with BOX genomic fingerprinting (DGGE-BOX). The distribution of the isolates in the DGGE-BOX clusters was used to calculate the Shannon diversity index per treatment. Interestingly, we observed that the Burkholderia diversity was affected by changes in the agricultural management, since the highest diversity was observed in permanent grassland and in continuous arable land. In addition, the diversity tended to be higher in the rhizosphere than in the corresponding bulk soil. The use of species abundance models indicated that rhizosphere communities had more even distributions than communities collected from the bulk soil. Identification of isolates revealed that only 2% of these belonged to the B. cepacia complex and that the majority was assigned to either (1) new Burkholderia species or (2) Burkholderia species that had originally been isolated from soil. Isolates classified as B. hospita, B. caledonica and Burkholderia sp. ‘LMG 22934’ and ‘LMG 22936’ were found mainly in the arable land, while isolates belonging to Burkholderia sp. ‘LMG 22929’ and B. phytofirmans were associated with the grassland area. Another potentially new Burkholderia species, ‘LMG 22932’, was found in both areas, in close association with the maize rhizosphere.     

Regional population viability of grassland songbirds: Effects of agricultural management

Although population declines of grassland songbirds in North America and Europe are well-documented, the effect of local processes on regional population persistence is unclear. To assess population viability of grassland songbirds at a regional scale (∼150,000 ha), we quantified Savannah Sparrow Passerculus sandwichensis and Bobolink Dolichonyx oryzivorus annual productivity, adult apparent survival, habitat selection, and density in the four most (regionally) common grassland treatments. We applied these data to a female-based, stochastic, pre-breeding population model to examine whether current grassland management practices can sustain viable populations of breeding songbirds. Additionally, we evaluated six conservation strategies to determine which would most effectively increase population trends. Given baseline conditions, over 10 years, simulations showed a slightly declining or stable Savannah Sparrow population (mean bootstrap λ = 0.99; 95% CI = 1.00-0.989) and severely declining Bobolink population (mean bootstrap λ = 0.75; 95% CI = 0.753-0.747). Savannah Sparrow populations were sensitive to increases in all demographic parameters, particularly adult survival. However for Bobolinks, increasing adult apparent survival, juvenile apparent survival, or preference by changing habitat selection cues for late-hayed fields (highest quality) only slightly decreased the rate of decline. For both species, increasing the amount of high-quality habitat (late- and middle-hayed) marginally slowed population declines; increasing the amount of low-quality habitat (early-hayed and grazed) marginally increased population declines. Both species were most sensitive to low productivity and survival on early-hayed fields, despite the fact that this habitat comprised only 18% of the landscape. Management plans for all agricultural regions should increase quality on both low- and high-quality fields by balancing habitat needs, nesting phenology, and species’ response to management.     

Assessing limitations on population growth in two critically endangered Acacia taxa

Flowering phenology, soil seedbank and the impact of fire, weeds and grazing were investigated in two rare Acacia taxa restricted to the agricultural district north of Perth Western Australia. Acacia aprica is known from six extant populations and one extinct population. Five of the extant populations are restricted to linear road reserves with the sixth population located in a small native vegetation remnant. Acacia cochlocarpa ssp. cochlocarpa is known from a single population also situated on a road verge. Size class structure, levels of canopy death and an absence of juveniles indicated that all populations are in decline. Flowering intensity and success varied between populations and years in A. aprica and between years in A. cochlocarpa ssp. cochlocarpa. Seed bank analysis indicated that seeds were patchily distributed while experimental fires demonstrated that such events could break seed dormancy and promote germination. Both taxa have similar germination physiologies and showed increased germination after seeds were exposed to heat. Following emergence, however, competition with annual weeds had a negative impact on seedling growth and survival in both taxa. While vertebrate grazing had some influence, weeds were the major inhibitory influence on recruitment. Reduced fire frequencies since fragmentation may be responsible for population decline in both taxa but other site specific factors such as weeds and grazing may affect the establishment of seedlings following fire.     

Temporal changes (1986-1999) in populations of primrose (Primula vulgaris Huds.) in an agricultural landscape and implications for conservation

In Belgium, Primula vulgaris is a rare and declining species. Its fate is bound up with the ever-changing agricultural landscape in northwestern Belgium and analysis of historical data showed a shrinking distribution area during the last decades. Contrary to the situation in England and France, most of the populations are situated in small landscape elements in the agricultural landscape and not in woodland. The population size distribution is skewed to very small populations (<10 individuals) with few younger life stages in small populations, higher proportions of older adults and unequal flower morph numbers. The changes in several population traits during a 13-year interval are correlated with initial population status, indicating that small populations tend to be more prone to extinction than larger ones. Small remnant woodland patches may be seen as ‘safe sites’: in this environment population sizes were more or less stable during the 13-year period whereas populations in ditches around arable fields were particularly susceptible to decline. Under current conditions, the long term survival of the species in small landscape elements is highly critical unless land use practices change drastically in the near future. The minimum viable populations concept and management of small landscape elements are discussed.     

Birds on roadside verges and the effect of mowing on frequency and distribution

The study, which was carried out both in the eastern and western parts of Denmark, describes the use made of roadside verges by birds, and makes a quantitative assessment of their importance. In addition, the influence of summer mowing on the birds was studied. The results show that different parts of the road verges are used for foraging and that the skylark Alauda arvensis more often forages on road sides than on the adjacent fields. The verges are also important as a nesting site for some species, for example the skylark, which prefers to nest in this habitat rather than in adjacent fields. Mowing in summer has no decisive effect on the number of birds or their distribution on road verges.     

The effects of fire and predators on the long-term persistence of an endangered shrub, Grevillea caleyi

Grevillea caleyi is an endangered plant species with a restricted range lying partly within Ku-ring-gai Chase and Garigal National Parks in NSW, Australia. The principle threatening processes affecting G. caleyi are habitat destruction and adverse fire regimes combined with high levels of seed predation. A stochastic, spatially explicit, individual-based model was constructed to investigate the population dynamics of small populations of the species and to determine the impact of a variety of management strategies. Results of model simulations indicate there is a high risk of population decline and local extinction in remnant sites with small populations under current management regimes. The most effective fire management strategy is to schedule fires that burn 20-100% of sub-populations every 5-15 years, in combination with reduced predation rates. When predation management strategies are employed in conjunction with a structured fire regime, then a 20-30% reduction in predation rates can improve the chance of long-term persistence substantially.     

Where can tigers persist in the future? A landscape-scale, density-based population model for the Indian subcontinent

Despite being targeted as a conservation flagship species for several decades, the tiger (Panthera tigris) grows ever more imperiled. Debate exists as to where tiger conservation should focus: on protected nature reserves or larger landscapes. We developed a landscape scale, density-based model to assess whether reasonably effective management of current reserves is adequate to ensure the survival of tiger populations. We focused on the Indian subcontinent, the region likely to harbor most tigers. Using tiger density estimates and vegetation data, we set tiger population targets that could be attained through reasonable management of the subcontinent’s nature reserves. Depending on the quality of the surrounding landscape matrix, our model indicated that the subcontinent could potentially hold ∼3500-6500 tigers, in up to 150 reserves. Strikingly, just 21 reserves can hold most (58-95%) of this tiger capacity. These high-population target reserves were relatively insensitive to the hostility of the surrounding matrix to tigers, as their aggregate capacity varied by <10% across a wide range of matrix conditions. In contrast, the remaining 129 reserves were highly sensitive to matrix quality, as they were unable to sustain populations with a tiger-hostile matrix, even with reasonable management. Our results suggest that reasonably improved management of the subcontinent’s reserves can sustain multiple tiger populations based on two differing conservation strategies. Conservation within the 21 reserves with the largest population targets should focus primarily on the reserves themselves. In contrast, tiger conservation in the remaining reserves can succeed only with additional management of the unprotected landscapes that surround them.     

Habitat associations of bats in Northern Ireland: implications for conservation

Agricultural intensification in Northern Ireland has brought about large-scale changes to the landscape with a detrimental effect on biodiversity. Between 1996 and 1998, we surveyed a stratified random sample of 1 km squares for bats using a spot-sample technique and time expansion bat detector to establish linear and area habitat associations. Bats strongly selected water bodies with bankside vegetation, treelines, and deciduous and mixed woodland edge, avoiding open areas such as upland/unimproved grassland and improved grassland. Of three sympatric pipistrelle species (Pipistrellus pipistrellus, P. pygmaeus and P. nathusii), two were shown to forage in different habitats; P. pipistrellus being more of a ‘generalist’, foraging in a wider variety of habitats than P. pygmaeus, a ‘specialist’ which foraged in a smaller range of habitats. Nyctalus leisleri selected parkland/amenity grassland, deciduous woodland edge and rivers/canals and avoided improved grassland, hedgerows, whilst Myotis spp. selected deciduous woodland centre, lake/reservoir margins and rivers/canals. Reduction in area and quality of inland water, deciduous woodlands and field boundaries in Northern Ireland may impact on bat populations. Habitat management should focus on improving those habitats which are selected by bats, including the maintenance and enhancement of connecting linear habitats.     

Thresholds in the long-term responses of breeding birds to forest cover and fragmentation

Mitigating the effects of habitat loss requires estimating the minimum amount of habitat necessary for the persistence of wildlife populations in a changing landscape. Assessing minimum habitat amounts, however, relies on identifying ecological thresholds in species’ responses to landscape change. Using two repeated state-wide atlases, our objective was to investigate the responses of 25 forest birds to a range of forest cover and fragmentation. Repeat atlases allow for the analysis of four population dynamics including: (1) colonization, (2) persistence, (3) extinction, and (4) absence. Our objective was to test the hypothesis that forest birds demonstrated thresholds in these four basic dynamics to varying amounts of forest cover and fragmentation.We found thresholds to be a common, though not pervasive, characteristic of how forest birds respond to forest cover and pattern. We found that the probability of persistence was positively correlated with forest cover and 22 species demonstrated threshold responses. In addition, 15 of 25 birds demonstrated discrete thresholds in extinction dynamics. The existence of a colonization threshold has received significantly less attention in ecology. We also found that 17 out of 25 species demonstrated thresholds in their colonization response to a greater amount of forest cover. The effects of forest fragmentation, independent of forest amount, were less clear. We found support for incorporating the effects of fragmentation, but this fragmentation effect was found both below and above threshold points. We conclude that incorporating ecological thresholds in environmental planning should be species-specific and focus on populations on the verge of rapid ecological change.     

The relative importance of patch habitat quality and landscape attributes on a declining steppe-bird metapopulation

Metapopulation theory is one of the most popular approaches to identify the factors affecting the spatial and temporal dynamics of populations in fragmented habitat networks. Habitat quality, patch area and isolation are mainly focused on when analyzing distribution patterns in fragmented landscapes. The effects of landscape heterogeneity in the non-occupied matrix, however, have been largely neglected. Here, we determined the relative importance of patch quality and landscape attributes on the occurrence, density and extinction of the Dupont’s lark (Chersophilus duponti), an endangered steppe passerine whose habitat has been extremely reduced to highly isolated and fragmented patches embedded in a mainly unsuitable landscape matrix. Habitat patch quality, measured in terms of vegetation structure, grazing pressure, arthropod availability, predator abundance, and inter-specific competition, did not affect occurrence, density or extinction. At the landscape scale, however, the species’ occurrence was principally determined by the interactions among patch size, geographic isolation and landscape matrix. Isolation had the main independent contribution to explaining the probability of occurrence, followed by landscape matrix composition and patch size. The species’ density was negatively correlated to patch size, suggesting crowding effects in small fragments, while extinction events were exclusively related to isolation. Our findings suggest that landscape rather than local population characteristics are crucial in determining the patterns of distribution and abundance of non-equilibrium populations in highly fragmented habitat networks. Consequently, conservation measures for these species should simultaneously involve patch size, isolation and landscape matrix and apply to the entire metapopulation rather than to particular patches.     

Insular pest control within a metapopulation context

Introduced pests threaten many species and their control is generally beneficial for conservation, particularly on islands where complete eradication is possible. Unfortunately on ‘nearshore’ islands neighbouring source populations exist and unaided reinvasion is likely. Pest control programmes at these sites thus require a metapopulation context to adequately manage movements between source and sink populations. We investigated the ecology of introduced ship rats (Rattus rattus) on a nearshore island, and gene flow with adjacent mainland populations, in order to understand the metapopulation dynamics and relative levels of pest control required within the landscape. We sampled the entire population by trapping (n = 30), achieving eradication, and found a low rat density (3.2 ha⁻¹) indicative of a sink population. Seed and other plant material constituted the major dietary component of rats. Despite its proximity to mainland source populations, the island population was genetically distinct with reduced allelic diversity caused by a recent reinvasion founder effect. Genetic analyses also detected recent migrants between the populations. In contrast, two mainland populations separated by a similar distance displayed complete genetic mixing. The small water gap therefore provides a sufficient barrier to lower the migration rate to the island and delay reinvasion, which nonetheless eventually happens. In order to maintain nearshore islands pest-free, conservation management will require a metapopulation approach simultaneously focusing on both island and source population pest control.