Habitats and Resources: The Need for a Resource-based Definition to Conserve Butterflies

Current definitions of habitat are closely allied to the concept of patch and matrix. This concept is, for instance, central to the prevailing metapopulation models of population dynamics. But, butterfly population dynamics, mobility and spatial structure can only properly be understood in the context of a resource-based definition of habitats. In criticising current definitions of habitat, we illustrate how habitat is best understood in terms of resource distributions. These transcend vegetation-based definitions of habitat and lie at the root of life history strategies, the vulnerability of butterflies to environmental changes and extinction, and govern conservation status. We emphasise the need for a resource-use database and demonstrate the shortcomings of current data for conserving butterflies; patch based definitions of habitats are inappropriate for some species and for others do not provide a universal panacea, inadequately explaining spatial occurrence when scaled over space and time. A resource-based habitat definition challenges the bipolar, patch vs. matrix view of landscape; the alternative is to view landscape as a continuum of overlapping resource distributions. We urge greater attention to the details of butterfly behaviour and resource use as the keys to understanding how landscape is exploited and therefore to successful conservation at the landscape scale.     

The dimer interface of the membrane type 1 matrix metalloproteinase hemopexin domain: crystal structure and biological functions

Homodimerization is an essential step for membrane type 1 matrix metalloproteinase (MT1-MMP) to activate proMMP-2 and to degrade collagen on the cell surface. To uncover the molecular basis of the hemopexin (Hpx) domain-driven dimerization of MT1-MMP, a crystal structure of the Hpx domain was solved at 1.7 Å resolution. Two interactions were identified as potential biological dimer interfaces in the crystal structure, and mutagenesis studies revealed that the biological dimer possesses a symmetrical interaction where blades II and III of molecule A interact with blades III and II of molecule B. The mutations of amino acids involved in the interaction weakened the dimer interaction of Hpx domains in solution, and incorporation of these mutations into the full-length enzyme significantly inhibited dimer-dependent functions on the cell surface, including proMMP-2 activation, collagen degradation, and invasion into the three-dimensional collagen matrix, whereas dimer-independent functions, including gelatin film degradation and two-dimensional cell migration, were not affected. These results shed light on the structural basis of MT1-MMP dimerization that is crucial to promote cellular invasion.     

Mapping the Habitat Quality of Patch Networks for the Marsh Fritillary Euphydryas aurinia (Rottemburg, 1775) (Lepidoptera, Nymphalidae) in Wales

The marsh fritillary is widely distributed in Wales, with over 200 populations identified in the past 15 years. However, agricultural improvement, habitat fragmentation and changes in agricultural practices continue to impact on status and a decline in range of 23.5% was recorded over a 10-year period. Solutions must be applied at the landscape scale to improve metapopulation viability and, since 2000, surveys of habitat extent and quality have been carried out on 116,373 ha of grassland surrounding 111 populations. Analysis of the results for standard ‘core landscapes’ (based on circles of 1 km radius around known populations) shows that overall cover of suitable breeding habitat is 3.44%. However, only 11.85% of the grassland that was suitable for marsh fritillaries was classified as being in Good Condition. The remainder was regarded as having sub-optimal vegetation structure and/or the foodplant was at low density; 33% of the habitat resource that was not in Good Condition was regarded as inappropriately or excessively managed and 67% was suffering from neglect. An Index of Landscape Quality is used to rank landscapes for evaluation. Thirty-five ‘core landscapes’ (incorporating 98 marsh fritillary populations) were assessed and just four exceeded a threshold value deemed to represent viable landscape configurations. The results have demonstrated that most marsh fritillary populations in Wales exist within depauperate patch networks that lack sufficient breeding habitat of the right quality for long-term persistence. Without targeted conservation action the marsh fritillary will continue to decline in Wales. This paper reports on efforts to collect information on the quality of breeding habitat for marsh fritillaries across Wales in order to identify priorities for conservation action.     

Coexistence and host use by a large community of Pierid butterflies: habitat is the templet

Summary We report studies on the butterfly-hostplant communities in the species-rich area of west central Morocco. Pieridae feeding on Capparales form two distinct ecological guilds: inflorescence feeders and folivores. Several members of each guild may synchronously occur in sympatry. Substantial levels of cannibalism and inter-specific predation occur amongst the inflorescence feeders. No evidence was obtained for segregation of butterfy species on different hosts. Host plants included in the diet of specialists were also used by generalists. Despite substantial differences observed in laboratory trials of larval survivorship on different hostplants, results were congruent for all Pieridae, suggesting that little one-to-one insect-host coevolution has occurred. Host specialization was instead related to the year-to-year stability of host numbers in an area. High levels of pierid infestation occurred on host species with numerically stable populations. Host numerical stability was correlated with habitat type. There is little evidence for segregation of competing inflorescence feeders by hostplant species, but some evidence for segregation by habitat type (particularly by shading levels). We interpret our results as indicating that the hostplant affiliations of Moroccan Capparales-feeding Pieridae are subject to (at best) diffuse coevolutionary effects from hosts and competitors, and are strongly influenced by habitat characteristics.     

The effect of matrix on the occurrence of hazel grouse (Bonasa bonasia) in isolated habitat fragments

The aim of this study was to determine the effect of matrix on the occurrence of hazel grouse (Bonasa bonasia) in habitat fragments. The study was conducted in two kinds of landscape: (1) an agricultural landscape, where the censused forest habitat fragments were surrounded by farmland, and (2) in an intensively managed forested landscape, where the censused habitat fragments were surrounded by nonhabitat coniferous forest. Occupied and unoccupied habitat fragments in the agricultural landscape differed significantly in distance to the nearest suitable continuous habitat, with hazel grouse occurring only in habitat fragments closer than 100 m from continuous forest. In the intensively managed forest landscape, the effect of isolation was less evident, but there might be a threshold around 2 km. Effects of isolation occurred over much shorter distances when the surrounding habitats consisted of farmland than when it was forested habitats. The size of the habitat fragments was important in both landscapes, with larger habitat fragments more often containing hazel grouse.     

Persistence of species in a fragmented urban landscape: the importance of dispersal ability and habitat availability for grassland butterflies

Some species cope with, and survive in, urban areas better than others.From a conservation viewpoint it is important to understand why some species arerare or are excluded in the urban landscape, in order that we might take actionto conserve and restore species. Two ecological factors that might explain thedistribution and abundance of butterfly species in the urban landscape aredispersal ability and the availability of suitable habitat. The influence ofthese factors was assessed by examining the distribution and genetic structureof four grassland butterfly species in the West Midlands conurbation, UK. Thefour species differ in their distribution and abundance, mobility and habitatspecificity. No significant fit to the isolation-by-distance model was found forany of the study species at this spatial scale. MeanF _ST values revealed a non-significant level ofpopulation structuring for two species, Pieris napi (L.)and Maniola jurtina (L.), but moderate and significantpopulation differentiation for Pyronia tithonus (L.) andCoenonympha pamphilus (L.). Results suggest that thesespecies are limited more by the availability of suitable habitat than by theirability to move among habitat patches. Conservation strategies for thesegrassland species should initially focus on the creation and appropriatemanagement of suitable habitat. More sedentary species that have already beenexcluded from the conurbation may require a more complex strategy for theirsuccessful restoration.     

Winter habitat use by Loggerhead Shrikes (Lanius Ludovicianus) in Mexico: separating migrants from residents using stable isotopes

Several species of migrant birds overlap in range on their wintering grounds with non-migrant conspecifics or other species that occupy a similar niche. Very little is known whether such overlap results in competition and subsequent habitat segregation since it is usually impossible to separate resident from migrant individuals. The Loggerhead Shrike (Lanius ludovicianus) is a declining grassland species in North America that winters in the southern United States and Mexico. Using stable-hydrogen isotope (δD) analysis of feathers, we identified resident and migrant shrikes wintering in northeastern Mexico based on a latitudinal gradient in precipitation and feather δD values. Indicator species analyses showed that migrants occupied areas where bare ground was less available than those occupied by residents, a pattern which held when a more restricted set of birds from the extremes of the δD distribution were considered. This provides evidence for conspecific habitat segregation. Habitat differences were also found between sites occupied by shrikes and apparently suitable but unoccupied sites. Shrikes occupied more open sites that contained shorter tall shrubs and huisache (Acacia farneasiana) and fewer tall shrubs, mesquite (Prosopsis glandulosa) and huisache than unoccupied sites. The availability of suitable winter habitat and the potential competition between migrants and residents may be factors that influence the population dynamics of migrant shrikes in North America.     

Dynamic interdomain interactions contribute to the inhibition of matrix metalloproteinases by tissue inhibitors of metalloproteinases

Because of their important function, matrix metalloproteinases (MMPs) are promising drug targets in multiple diseases, including malignancies. The structure of MMPs includes a catalytic domain, a hinge, and a hemopexin domain (PEX), which are followed by a transmembrane and cytoplasmic tail domains or by a glycosylphosphatidylinositol linker in membrane-type MMPs (MT-MMPs). TIMPs-1, -2, -3, and -4 are potent natural regulators of the MMP activity. These are the inhibitory N-terminal and the non-inhibitory C-terminal structural domains in TIMPs. Based on our structural modeling, we hypothesized that steric clashes exist between the non-inhibitory C-terminal domain of TIMPs and the PEX of MMPs. Conversely, a certain mobility of the PEX relative to the catalytic domain is required to avoid these obstacles. Because of its exceedingly poor association constant and, in contrast with TIMP-2, TIMP-1 is inefficient against MT1-MMP. We specifically selected an MT1-MMP·TIMP-1 pair to test our hypothesis, because any improvement of the inhibitory potency would be readily recorded. We characterized the domain-swapped MT1-MMP chimeras in which the PEX of MMP-2 (that forms a complex with TIMP-2) and of MMP-9 (that forms a complex with TIMP-1) replaced the original PEX in the MT1-MMP structure. In contrast with the wild-type MT1-MMP, the diverse proteolytic activities of the swapped-PEX chimeras were then inhibited by both TIMP-1 and TIMP-2. Overall, our studies suggest that the structural parameters of both domains of TIMPs have to be taken into account for their re-engineering to harness the therapeutic in vivo potential of the novel TIMP-based MMP antagonists with constrained selectivity.     

Spatial patterns in at-sea behaviour during spring migration by little gulls ( Larus minutus ) in the southeastern North Sea

At-sea distribution of seabirds has been studied on different scales and with different focus in many parts of the world. However, factors and/or processes causing certain patterns are often not easily explained. This also holds true for fast migrating species of international conservation concern, such as the little gull (Larus minutus) in the German Bight (southeastern North Sea). In this study, we used multiyear distributional data in combination with behavioural observations and food sampling to investigate spatial and temporal patterns and their possible causes during spring migration. The results show a highly focussed migration pattern during the last week of April and the first week of May. The river Eider seemed to play an important role as main migration route. Highest numbers were found either close to the mainland or close to the offshore islands. Little gulls used certain subareas for intense feeding (i.e. the region near Helgoland and the outlet of river Elbe) and others for migration. Hydrographic phenomena such as fronts and foam lines play an important role within the feeding sites and strongly influence behaviour and distribution. Feeding behaviour as well as samples of probable prey revealed different quality of feeding sites according to the energy density of the most abundant probable food items (drowned insects versus zooplankton and fish). In conclusion, the area utilisation of L. minutus during spring migration in the German Bight showed a clear pattern, and sites with main feeding action should be regarded as sensitive for little gulls, at least during spring migration.     

Hyaluronan expressed by the hematopoietic microenvironment is required for bone marrow hematopoiesis

The contribution of hyaluronan (HA) to the regulatory network of the hematopoietic microenvironment was studied using knock-out mice of three hyaluronan synthase genes (Has1, Has2, and Has3). The number of hematopoietic progenitors was decreased in bone marrow and increased in extramedullary sites of Prx1-Cre;Has2(flox/flox);Has1(-/-);Has3(-/-) triple knock-out (tKO) mice as compared with wild type (WT) and Has1(-/-);Has3(-/-) double knock-out (dKO) mice. In line with this observation, decreased hematopoietic activity was observed in long term bone marrow cultures (LTBMC) from tKO mice, whereas the formation of the adherent layer and generation of hematopoietic cells in WT and dKO cultures was not different. 4-Methylumbelliferone (4MU) was used to pharmacologically inhibit the production of HA in LTBMC. Treatment with 4MU inhibited HA synthesis, decreased expression of HAS2 and HAS3, and eliminated hematopoiesis in LTBMC, and this effect was alleviated by the addition of exogenous HA. Exogenous HA also augmented the cell motility in LTBMC, which correlated with the HA-stimulated production of chemokines and growth factors. Conditioned media from HA-induced LTBMC enhanced the chemotaxis of hematopoietic stem/progenitor cells (HSPC) in response to SDF-1. Exposure of endothelial cells to 4MU decreased their ability to support HSPC rolling and adhesion. In addition, migration of transplanted HSPC into the marrow of 4MU-pretreated mice was lower than in untreated mice. Collectively, the results suggest that HA depletion reduces the ability of the microenvironment to support HSPC, and confirm a role for HA as a necessary regulatory element in the structure of the hematopoietic microenvironment.     

Making the matrix matter: challenges in Australian grazing landscapes

Many ecological theories are based on the concept of patches. Patches are a useful starting point for conservation efforts, but a focus on patches alone will not always achieve desired conservation outcomes. Conservation strategies in the grazing landscapes of southeastern Australia suggest that large patches of trees are widely regarded as habitat while other forms of habitat are largely ignored. We provide data on birds and reptiles from the Nanangroe grazing landscape that illustrate the potential habitat value of areas located between large patches of trees – that is, the matrix. Despite evidence on its potential value, present conservation strategies rarely consider the matrix. Possible reasons for this bias relate to the economics of farming and the history of land use, the current environmental law framework, and also the reluctance of ecologists to study the matrix. More scientific evidence on the role of the matrix will be crucial if conservation strategies are to consider not only patches, but entire landscapes. However, for science to be relevant to land management, there is a need for new research approaches. First, an increased consideration of environmental policy and law will increase the likelihood of scientific findings being adopted by policy makers. Second, at an applied level, more practical on-ground research into farming practices and clearer communication are necessary to achieve more sustainable matrix management in Australian grazing landscapes.     

On the significance of structural vegetation elements for caterpillar thermoregulation in two peat bog butterflies: Boloria eunomia and B. aquilonaris

Purpose

Temperature profoundly impacts on distribution and habitat-use of organisms. The development of ectothermous caterpillars does not depend on host plant quality only, but also on the availability of suitable thermal conditions. Selection for thermally favorable microclimates (i.e. behavioral thermoregulation) is a primary mechanism of temperature control, and caterpillars can be either (or alternately) temperature conformers (i.e. passively adopting ambient temperature conditions) or thermoregulators (i.e. able to some extent to elevate or decrease their body temperature relative to ambient temperature). Here, we addressed the functional significance of different structural vegetation elements for the behavioral thermoregulation by caterpillars of two butterfly species.

Results

Weather conditions influenced the caterpillar detection probability within host plant patches, indicating that caterpillars can hide and use suitable microclimates provided by vegetation structures to cope with weather variations. This is why we (1) evaluated the heterogeneity in temperature conditions provided by these structures, (2) quantified the influence of ambient temperature and light intensity on caterpillar body temperature, and (3) tested how position on structure, substrate color and exposition influenced caterpillar body temperature. As expected, vegetation structures provided heterogeneous temperature and sun exposition conditions, while caterpillar body temperature was dependent on ambient temperature and light intensity. But body temperature was additionally influenced by the position on vegetation structures, substrate color and exposition.

Conclusions

These results suggest that there is no unique and fixed structure in the vegetation subsuming the best thermal conditions for caterpillars. We argue that a better understanding of the thermal properties of vegetation structures is essential for correctly understanding caterpillar habitat-use and the behavioral mechanisms driving their body thermoregulation. Conceptually this means that thermal conditions should be included in the definition of a species' functional habitat. Practically this may influence the choice of appropriate habitat management for species of conservation concern.     

Habitat structure and animal movement: the behaviour of bumble bees in uniform and random spatial resource distributions

Foraging organisms (like bumble bees) move between resource points (like flowers) whose natural distributions vary enormously: from hyperdispersed to random to clumped. These differences in habitat structure may significantly influence the fitness of both plant and pollinator. To examine the effect of habitat structure on pollinator movement and fitness, we observed captive worker bumble bees collecting nectar from artificial flowers containing equal volumes of reward and arranged in two spatial configurations: a hexagonal array with constant distances between flowers (“constant”), and an “exploded hexagonal” array, with variable distances between flowers (“variable”). The mean nearest-neighbour distance was the same in both arrays, as was the general hexagonal appearance. The experiment therefore compares how resource dispersion, independent of nearest-neighbour distance, influences bee behaviour. Bees in the variable array showed decreased directionality, higher revisitation frequencies, and greater inter-flower flight distances than shown in the constant array. As a consequence, bees in the variable array had a 19% lower gross rate of nectar collection. Our results suggest that wild-foraging bees should prefer regularly spaced flowers (when all else, including mean nearest-neighbour distance, is equal), and that plants can decrease self-pollination by regular spacing between flowers, inflorescences, or individuals. Received: 16 January 1996 / Accepted: 30 June 1997     

Assessing habitat and resource availability for an endangered desert bird species in eastern Morocco: the Houbara Bustard

In Morocco we tested the consistency between an a priori habitat classification based on topography, hydrology, vegetation structure and composition, and an a posteriori classification based on arthropod assemblages, in a plain supporting wild endangered Houbara Bustards. According to vegetation structure, we defined seven a priori habitats that differed significantly in perennial cover and height. A multivariate multiple regression analysis showed a significant relationship between arthropod assemblages and vegetation structure. Canonical Analyses of Principal Coordinates, conducted simultaneously on direct searches of arthropods and trapping data, showed significant differences between assemblages in both cases, and produced two similar constrained ordinations of six a posteriori habitats: esparto grass (Stipa tenacissima), temporarily flooded areas, fields, “reg” with short perennials, “reg” with tall perennials and wadis. The two sampling methods reflected a dominance of ants and beetles. Arthropod biomasses increased significantly in spring and then decreased significantly in summer for beetles, and in autumn for ants. No strong differences appeared between habitats within seasons, especially in spring, indicating a uniform distribution of food resources during the Houbara breeding season. The “reg” with short perennials had the highest ant biomass in summer. This “reg” and fields also supported the highest arthropod biomass in autumn. Variation in arthropod biomass was a pertinent factor that should be integrated into Houbara habitat selection studies. The definition of habitat availability based on easily identifiable landscape units, combined with empirical tests on arthropod communities provided an accurate classification for habitat selection studies and conservation planning.     

Effect of different matrices on physiological amino acids analysis by liquid chromatography: evaluation and correction of the matrix effect

Free amino acids in plasma, muscle and liver tissues were determined using the Pico-Tag method which involves HPLC and pre-column derivatization. A study of the accuracy in the determination is carried out by means of external calibration, standard-added calibration, Youden calibration and analyte recovery. It is conclusively shown that the method is affected by a proportional systematic error due to matrix effects, but not by a constant one. A new function named matrix-corrected calibration is proposed to correct for proportional bias when free analyte matrices for matrix-matched addition is unavailable.     

Habitat selection and home range in the Blanford's fox,Vulpes cana: compatibility with the resource dispersion hypothesis

Summary This paper presents analyses of habitat-use and home range size in the Blanford's fox. We predicted, from the resource dispersion hypothesis (RDH), that home ranges would encompass similar areas of combined fruitful habitats, but widely different areas of useless habitats, and thus that home ranges would be larger where such fruitful patches are fragmented and widely dispersed. Home range estimates of 0.5–2.0 km² were calculated for 16 adult Blanford's foxes, using three different methods. There were no significant differences in home range size between sexes or study sites. One habitat, dry creekbed, was the most frequently visited in all home ranges. Dry creekbed provided abundant prey for the foxes and only sparse cover for their predators. Both the available area of creekbed in each range, and the area of creekbed patches that was used by the foxes, were independent of home range size. However, the variance in home range size was explained by the mean distance between the main denning area and the most frequently used patches of creekbed. These results are in accord with some predictions of the resource dispersion hypothesis.     

Beyond the patch: Disturbance affects species abundances in the surrounding community

The role of disturbance in community ecology has been studied extensively and is thought to free resources and reset successional sequences at the local scale and create heterogeneity at the regional scale. Most studies have investigated effects on either the disturbed patch or on the entire community, but have generally ignored any effect of or on the community surrounding disturbed patches. We used marine fouling communities to examine the effect of a surrounding community on species abundance within a disturbed patch and the effect of a disturbance on species abundance in the surrounding community. We varied both the magnitude and pattern of disturbance on experimental settlement plates. Settlement plates were dominated by a non-native bryozoan, which may have established because of the large amount of initial space available on plates. Percent covers of species within the patch were affected by the surrounding community, confirming previous studies' predictions about edge effects from the surrounding community on dynamics within a patch. Disturbance resulted in lower percent cover in the surrounding community, but there were no differences between magnitudes or spatial patterns of disturbance. Disturbance lowered population growth rates in the surrounding community, possibly by altering the abiotic environment or species interactions. Following disturbance, the recovery of species within a patch may be affected by species in the surrounding community, but the effects of a disturbance can extend beyond the patch and alter abundances in the surrounding community. The dependence of patch dynamics on the surrounding community and the extended effects of disturbance on the surrounding community, suggest an important feedback of disturbance on patch dynamics indirectly via the surrounding community.     

Osteopontin undergoes polymerization in vivo and gains chemotactic activity for neutrophils mediated by integrin alpha9beta1

Osteopontin (OPN) is an integrin-binding inflammatory cytokine that undergoes polymerization catalyzed by transglutaminase 2. We have previously reported that polymeric OPN (polyOPN), but not unpolymerized OPN (OPN*), attracts neutrophils in vitro by presenting an acquired binding site for integrin α9β1. Among many in vitro substrates for transglutaminase 2, only a few have evidence for in vivo polymerization and concomitant function. Although polyOPN has been identified in bone and aorta, the in vivo functional significance of polyOPN is unknown. To determine whether OPN polymerization contributes to neutrophil recruitment in vivo, we injected OPN* into the peritoneal space of mice. Polymeric OPN was detected by immunoblotting in the peritoneal wash of mice injected with OPN*, and both intraperitoneal and plasma OPN* levels were higher in mice injected with a polymerization-incompetent mutant, confirming that OPN* polymerizes in vivo. OPN* injection induced neutrophil accumulation, which was significantly less following injection of a mutant OPN that was incapable of polymerization. The importance of in vivo polymerization was further confirmed with cystamine, a transglutaminase inhibitor, which blocked the polymerization and attenuated OPN*-mediated neutrophil recruitment. The thrombin-cleaved N-terminal fragment of OPN, another ligand for α9β1, was not responsible for neutrophil accumulation because a thrombin cleavage-incompetent mutant recruited similar numbers of neutrophils as wild type OPN*. Neutrophil accumulation in response to both wild type and thrombin cleavage-incompetent OPN* was reduced in mice lacking the integrin α9 subunit in leukocytes, indicating that α9β1 is required for polymerization-induced recruitment. We have illustrated a physiological role of molecular polymerization by demonstrating acquired chemotactic properties for OPN.