Effect of habitat fragmentation on levels and patterns of genetic diversity in natural populations of the peat moss Polytrichum commune

Peat bogs represent unique ecosystems that are under particular threat from fragmentation due to peat harvesting, with only 38% of the original peatland in Europe remaining intact and unaffected by peat cutting, drainage and silviculture. In this study, we have used microsatellite markers to determine levels and patterns of genetic diversity in both cut and uncut natural populations of the peat moss Polytrichum commune. Overall diversity levels suggest that there is more genetic variation present than had previously been assumed for bryophytes. Despite this, diversity values from completely cut bogs were found to be lower than those from uncut peatlands (average 0.729 versus 0.880). In addition, the genetic diversity was more highly structured in the cut populations, further suggesting that genetic drift is already affecting genetic diversity in peat bogs subjected to fragmentation.

A species invasion mediated through habitat structure, intraguild predation and parasitism.

With field, laboratory, and modeling approaches, we examined the interplay among habitat structure, intraguild predation (IGP), and parasitism in an ongoing species invasion. Native Gammarus duebeni celticus (Crustacea: Amphipoda) are often, but not always, replaced by the invader Gammarus pulex through differential IGP. The muscle-wasting microsporidian parasite Pleistophora mulleri infects the native but not the invader. We found a highly variable prevalence of P. mulleri in uninvaded rivers, with 0–91% of hosts parasitized per sample. In addition, unparasitized natives dominated fast-flowing riffle patches of river, whereas parasitized individuals dominated slower- flowing, pooled patches. We examined the survivorship of invader and native in single and mixed-species microcosms with high, intermediate, and zero parasite prevalence. G. pulex survivorship was high in all treatments, whereas G. duebeni subsp. celticus survivorship was significantly lower in the presence of the invader. Further, parasitized G. duebeni subsp. celticus experienced near-total elimination. Models of the species replacement process implied that parasite-enhanced IGP would make invasion by G. pulex more likely, regardless of habitat and parasite spatial structure. However, where heterogeneity in parasite prevalence creates a landscape of patches with different susceptibilities to invasion, G. pulex may succeed in cases where invasion would not be possible if patches were equivalent. The different responses of parasitized and unparasitized G. duebeni subsp. celticus to environmental heterogeneity potentially link landscape patterns to the success or failure of the invasion process.

The area-independent effects of habitat complexity on biodiversity vary between regions.

Potential explanatory variables often co-vary in studies of species richness. Where topography varies within a survey it is difficult to separate area and habitat-diversity effects. Topographically complex surfaces may contain more species due to increased habitat diversity or as a result of increased area per se. Fractal geometry can be used to adjust species richness estimates to control for increases in area on complex surfaces. Application of fractal techniques to a survey of rocky shores demonstrated an unambiguous area-independent effect of topography on species richness in the Isle of Man. In contrast, variation in species richness in south-west England reflected surface availability alone. Multivariate tests and variation in limpet abundances also demonstrated regional variation in the area-independent effects of topography. Community composition did not vary with increasing surface complexity in south-west England. These results suggest large-scale gradients in the effects of heterogeneity on community processes or demography.

Challenging assumptions of future coastal habitat development around the UK

One habitat management requirement forced by 21st century relative sea-level rise (RSLR), will be the need to re-comprehend the dimensions of long-term transgressive behaviour of coastal systems being forced by such RSLR. Fresh approaches to the conceptual modelling and subsequent implementation of new coastal and peri-marine habitats will be required. There is concern that existing approaches to forecasting coastal systems development (and by implication their associated scarce coastal habitats) over the next century depend on a certain premise of orderly spatial succession of habitats. This assumption is shown to be questionable given the possible future rates of RSLR, magnitude of shoreline retreat and the lack of coastal sediment to maintain the protective morphologies to low-energy coastal habitats. Of these issues, sediment deficiency is regarded as one of the major problem for future habitat development. Examples of contemporary behaviour of UK coasts show evidence of coastal sediment starvation resulting from relatively stable RSLR, anthropogenic sealing of coastal sources, and intercepted coastal sediment pathways, which together force segmentation of coastal systems. From these examples key principles are deduced which may prejudice the existence of future habitats: accelerated future sediment demand due to RSLR may not be met by supply and, if short- to medium-term hold-the-line policies predominate, long-term strategies for managed realignment and habitat enhancement may prove impossible goals. Methods of contemporary sediment husbandry may help sustain some habitats in place but otherwise, instead of integrated coastal organization, managers may need to consider coastal breakdown, segmentation and habitat reduction as the basis of 21st century coastal evolution and planning.

Habitat-specific adaptation of immune responses of stickleback (Gasterosteus aculeatus) lake and river ecotypes

Freshwater populations of three-spined sticklebacks (Gasterosteus aculeatus) in northern Germany are found as distinct lake and river ecotypes. Adaptation to habitat-specific parasites might influence immune capabilities of stickleback ecotypes. Here, naive laboratory-bred sticklebacks from lake and river populations were exposed reciprocally to parasite environments in a lake and a river habitat. Sticklebacks exposed to lake conditions were infected with higher numbers of parasite species when compared with the river. River sticklebacks in the lake had higher parasite loads than lake sticklebacks in the same habitat. Respiratory burst, granulocyte counts and lymphocyte proliferation of head kidney leucocytes were increased in river sticklebacks exposed to lake when compared with river conditions. Although river sticklebacks exposed to lake conditions showed elevated activation of their immune system, parasites could not be diminished as effectively as by lake sticklebacks in their native habitat. River sticklebacks seem to have reduced their immune-competence potential due to lower parasite diversity in rivers

Pollinators of an endemic and endangered species, Mammillaria gaumeri (Cactaceae), in its natural habitat (coastal dune) and in a botanical garden.

Mammillaria gaumeri (Britton & Ross) Orcutt (Cactaceae), an endemic plant of the Yucatan Peninsula, is included by the Mexican government in the list of species that require special protection. Its natural habitat is now restricted to fragmented areas and protection programs involve botanical gardens in growing individuals rescued from disturbed areas. Little information is available on the reproductive characteristics of this species and nothing is known of its pollinators. We investigated the visitors of M. gaumeri flowers, collecting and observing bee species in its natural habitat (i.e., coastal dune) and in a botanical garden, where coastal dune vegetation had been created. Observations were made on plants whose density was artificially increased by grouping flowering individuals. At each site, we: 1) collected insects visiting the flowers; 2) recorded number of visits; and 3) video-recorded bee movements on the flowers. As expected, the number of bee species and visitation frequency were higher at the botanical garden than at the coastal dune. After landing on a flower, bees either inspected the anthers or dived among them. These behaviors, carried out by all observed species, seemed related to the state of the anthers (full or empty of pollen) and stigma lobes (opened or closed). Specifically, visits lasted longer when anthers were full of pollen and stigma lobes were opened. The same bee species recorded on the dune were also recorded at the botanical garden, suggesting that the artificial dune at the botanical garden offered suitable conditions for the natural pollinators of this endangered cactus.

Coexistence among native and introduced freshwater amphipods (Crustacea); habitat utilization patterns in littoral habitats

Studies of biological invasions predominantly stress threats to biodiversity through the elimination and replacement of native species. However, we must realise that resident communities may often be capable of integrating invaders, leading to patterns of coexistence. Within the past ninety years, three freshwater amphipod species have invaded Northern Ireland the North American Gammarus tigrinus and Crangonyx pseudogracilis, plus the European G. pulex. These species have come into contact with the ubiquitous native species, G. duebeni celticus. This study examined spatiotemporal patterns of stability of single and mixed species assemblages in an invaded lake. Lough Beg and its associated rivers were surveyed in summer 1994 and winter 1995, and a selection of stations re-sampled in summer one and five years later. All possible combinations of the four amphipod species were found. Although species presence/absence was stable between seasons at the scale of the whole lough, it was extremely fluid at the scale of individual sites, 82% of which changed in species composition between seasons. Overall mean amphipod abundance was similar across 5 distinguishable habitat types, but there were differences in species compositions among these habitats. In addition, although co-occurrences of Gammarus species did not differ from random, there was a strong negative association between Gammarus spp. and C. pseudogracilis. This latter pattern was at least in part generated by the better tolerance of C. pseudogracilis to lower water quality. A review of previous studies indicates that the exclusion of C. pseudogracilis by Gammarus species from high water quality areas is likely to involve biotic interaction. Thus, overall, co-existence of the four species, which is clearly dynamic and scale-dependent, appears promoted by spatial and temporal habitat heterogeneity. However, biotic interactions may also play a role in local exclusions. Since the three introduced species have not eliminated the native species, and each successive invasion has not replaced the previous invader, this study demonstrates that freshwater invaders may integrate with native communities leading to coexistence and increased species diversity.

Seasonal patterns in activity and habitat use by bats (Pipistrellus spp. and Nyctalus leisleri) in Northern Ireland, determined using a driven transect

The seasonal activity of Leisler's bat Nyctalus leisleri and pipistrelle bats Pipistrellus spp. with respect to minimum bat numbers and habitat use were investigated in County Down, Northern Ireland using a driven transect from April 1998 to October 1998. Data were collected in lowland farmland near Belfast, Northern Ireland using two BatBox III bat detectors tuned to detect both species and species groups simultaneously. The number of bats/km increased during April, May and June, peaking in July and tailed off after this period. The main peak in July is assumed to reflect the occurrence of newly volant young. An increase in the number of pipistrelle social calls during August and September probably represented mating activity. Bat activity correlated with temperature in both N. leisleri and Pipistrellus spp., although bat numbers were independent of temperature after the middle of June. There was significant variation in habitat use by pipistrelle bats along roads over the study period. Pipistrelle bats were observed in greater numbers in areas of tree-line, cut hedge (

Habitat for Humanity: Calibrating Best Practice Against the MDGs

Poverty alleviation lies at the heart of contemporary international initiatives on development. The key to development is the creation of an environment in which people can develop their potential, leading productive, creative lives in accordance with their needs, interests and faith. This entails, on the one hand, protecting the vulnerable from things that threaten their survival, such as inadequate nutrition, disease, conflict, natural disasters and the impact of climate change, thereby enhancing the poor’s capabilities to develop resilience in difficult conditions. On the other hand, it also requires a means of empowering the poor to act on their own behalf, as individuals and communities, to secure access to resources and the basic necessities of life such as water, food, shelter, sanitation, health and education. ‘Development’, from this perspective, seeks to address the sources of human insecurity, working towards ‘freedom from want, freedom from fear’ in ways that empower the vulnerable as agents of development (not passive recipients of benefaction).

Recognition of the magnitude of the problems confronted by the poor and failure of past interventions to tackle basic issues of human security led the United Nations (UN) in September 2000 to set out a range of ambitious, but clearly defined, development goals to be achieved by 2015. These are known as the Millennium Development Goals (MDGs). The intention of the UN was to mobilise multilateral international organisations, non-governmental organisations and the wider international community to focus attention on fulfilling earlier promises to combat global poverty. This international framework for development prioritises: the eradication of extreme poverty and hunger; achieving universal primary education; promoting gender equality and empowering women; reducing child mortality; improving maternal health; combating HIV/AIDS, malaria and other diseases; ensuring environmental sustainability; and developing a global partnership for development. These goals have been mapped onto specific targets (18 in total) against which outcomes of associated development initiatives can be measured and the international community held to account. If the world achieves the MDGs, more than 500 million people will be lifted out of poverty. However, the challenges the goals represent are formidable. Interim reports on the initiative indicate a need to scale-up efforts and accelerate progress.
Only MDG 7, Target 11 explicitly identifies shelter as a priority, identifying the need to secure ‘by 2020 a significant improvement in the lives of at least 100 million slum dwellers’. This raises a question over how Habitat for Humanity’s commitment to tackling poverty housing fits within this broader international framework designed to allievate global poverty. From an analysis of HFH case studies, this report argues that the processes by which Habitat for Humanity tackles poverty housing directly engages with the agenda set by the MDGs. This should not be regarded as a beneficial by-product of the delivery of decent, affordable shelter, but rather understood in terms of the ways in which Habitat for Humanity has translated its mission and values into a participatory model that empowers individuals and communities to address the interdependencies between inadequate shelter and other sources of human insecurity. What housing can deliver is as important as what housing itself is.

Examples of the ways in which Habitat for Humanity projects engage with the MDG framework include the incorporation of sustainable livelihoods strategies, up-grading of basic infrastructure and promotion of models of good governance. This includes housing projects that have also offered training to young people in skills used in the construction industry, microfinanced loans for women to start up their own home-based businesses, and the provision of food gardens. These play an important role in lifting families out of poverty and ensuring the sustainability of HFH projects. Studies of the impact of improved shelter and security of livelihood upon family life and the welfare of children evidence higher rates of participation in education, more time dedicated to study and greater individual achievement. Habitat for Humanity projects also typically incorporate measures to up-grade the provision of basic sanitation facilities and supplies of safe, potable drinking water. These measures not only directly help reduce mortality rates (e.g. diarrheal diseases account for around 2 million deaths annually in children under 5), but also, when delivered through HFH project-related ‘community funds’, empower the poor to mobilise community resources, develop local leadership capacities and even secure de facto security of tenure from government authorities.

In the process of translating its mission and values into practical measures, HFH has developed a range of innovative practices that deliver much more than housing alone. The organisation’s participatory model enables both direct beneficiaries and the wider community to tackle the insecurities they face, unlocking latent skills and enterprise, building sustainable livelihood capabilities. HFH plays an important role as a catalyst for change, delivering through the vehicle of housing the means to address the primary causes of poverty itself. Its contribution to wider development priorities deserves better recognition. In calibrating the success of HFH projects in terms of units completed or renovated alone, the significance of the process by which HFH realises these outcomes is often not sufficiently acknowledged, both within the organisation and externally. As the case studies developed in the report illustrate, the methodologies Habitat for Humanity employs to address the issue of poverty housing within the developing world, place the organisation at the centre of a global strategic agenda to address the root causes of poverty through community empowerment and the transformation of structures of governance.

Given this, the global network of HFH affiliates constitutes a unique organisational framework to faciliate sharing resources, ideas and practical experience across a diverse range of cultural, political and institutional environments. This said, it is apparent that work needs to be done to better to faciliate the pooling of experience and lessons learnt from across its affiliates. Much is to be gained from learning from less successful projects, sharing innovative practices, identifying strategic partnerships with donors, other NGOs and CBOs, and engaging with the international development community on how housing fits within a broader agenda to alleviate poverty and promote good governance.

Lamprey (Lampetra fluviatilis and Lampetra planeri) ammocoete habitat associations at regional, catchment and microhabitat scales in Northern Ireland

Habitat characteristics associated with lamprey ammocoetes (Lampetra spp.) were investigated at three different spatial scales: regional (Northern Ireland), catchment (Ballinderry River) and microhabitat. At the regional scale, ammocoetes were more abundant in rivers with a pH >= 8.2, while within a catchment, abundance was negatively related to the number of potential lamprey barriers and distance upstream. At the microhabitat scale, at sites where ammocoetes were present, ammocoetes were more abundant where median phi >= 1.94 (very coarse sand), where sediment depth >= 11.5 cm, and where kurtosis was >1.71. This study provides information on habitat associations of lamprey in the UK which may be of use in their conservation, in particular it highlights the negative association of migration barriers with lamprey abundance.