Habitat Tolerance Research Articles

Conservation of biodiversity in Scandinavian boreal forests: large carnivores as flagships, umbrellas, indicators, or keystones?

Large carnivores are often used as focal species (indicators, umbrellas, flagships or keystones) in conservation strategies either aimed at conserving carnivores, the rest of the biodiversity that occupies their habitats, or both. We evaluate their suitability for these roles in the context of boreal forest biodiversity conservation in the muti-use landscapes of Scandinavia. The enormous conflicts, especially with livestock, that carnivores cause in these areas makes them very controversial flagships to the extent that it may affect rural people's attitudes to conservation in general. Because of the broad habitat tolerance of large carnivores and their prey, and the difficulties in surveying carnivore numbers, they are very insensitive and impractical indicators of forest biodiversity. This ability of large carnivores to thrive in industrial forests means that the many species that are sensitive to modern forestry will not fall under the umbrella of areas managed for large carnivores. If large carnivores have a keystone function with respect to affecting the density of their ungulate prey it is likely to lead to even further conflicts with hunters who gain economic benefit from harvesting wild ungulates. In other words, none of the classic `ecological' arguments are likely to help justify large carnivore conservation, and large carnivore conservation is unlikely to help conserve the rest of the boreal forest's biodiversity. Based on these arguments we recommend that (1) justification for large carnivore conservation focus on the real philosophical and value orientated reasons rather than ecological justifications, (2) that this conservation should be brought about in practice by dedicated management programs that specifically address the conflicts caused by large carnivores, and (3) that boreal forest biodiversity is best conserved by specific actions designed to establish reserves or change forestry practices.

Effect of Introduced Mosquitofish on Pacific Treefrogs and the Role of Alternative Prey

Abstract: Mosquitofish (Gambusia affinis) are distributed by many mosquito control programs because of their broad habitat tolerance and because they are considered by some to be effective mosquito predators. As a result, mosquitofish have become established as an exotic species in numerous perennial streams in the Santa Monica Mountains within the last 10–15 years. Previous studies have found that mosquitofish prey heavily on California newt ( Taricha torosa) larvae that inhabit mountain streams. We found Pacific treefrog ( Hyla regilla) tadpoles in the stomachs of 65% of stream‐caught mosquitofish. In both laboratory and field experiments, we found that mosquitofish preyed heavily on treefrog tadpoles, even when high densities of mosquito larvae were presented as alternative prey. Thus, despite apparent high densities of Pacific treefrog populations, our experiments suggest that introduced mosquitofish may negatively affect stream‐breeding H. regilla in the Santa Monica Mountains.

Combining isotopic and ecomorphological data to refine bovid paleodietary reconstruction: a case study from the Makapansgat Limeworks hominin locality

The relationship between environmental change and hominin evolution remains obscure. For the most part, this stems from the difficulty of reconstructing ancient hominin habitats. Bovids are among the most frequently utilized paleoenvironmental indicators, but little is known about the habitat preferences of extinct taxa. It is generally assumed that fossil bovids both ate the same things and occupied the same habitats as their closest extant relatives. We test the first part of this assumption by reconstructing the diets of seven bovids from Makapansgat Limeworks, South Africa. Since diet and habitat are linked, these reconstructions have implications for our understanding of fossil bovid habitat tolerances. Ecomorphological and stable carbon isotope analyses are employed, allowing us to take advantage of the strengths and overcome the weaknesses of both. In most cases, fossil bovids did have similar diets to their extant relatives, and probably occupied similar habitats.Gazella vanhoepeniandAepycerossp., however, were almost exclusive browsers, and not mixed feeders like their living counterparts.

Host-Range and Distribution ofEucerocoris suspectus(Hemiptera: Miridae), a Potential Biological Control Agent for the Paperbark TreeMelaleuca quinquenervia(Myrtaceae)

The Australian paperbark tree, Melaleuca quinquenervia (Cavier) S. T. Blake, is a serious economic and environmental pest in Florida. One of the most damaging insects found attacking M. quinquenervia during surveys for biocontrol agents in its home range (Australia) was the leaf-blotching bug Eucerocoris suspectus Distant (Hemiptera: Miridae). Adults and nymphs of E. suspectus feed on young leaves and shoots. Their feeding kills leaf tissue surrounding the feeding site, leaving a distinctive, brown, blotch scar. Laboratory host-range studies showed 6 nontarget plant species to be at risk from E. suspectus. However, our extensive field survey data indicate that none of these plants are used as field hosts by E. suspectus. We conducted 8 intensive field searches for E. suspectus feeding damage on >60 plant species at 6 sites. Damage was only noted on Melaleuca spp., except on 1 occasion, where minor feeding damage was found on 2 Lumnitzera racemosa trees adjacent to a more heavily damaged M. quinquenervia tree. Thus, although E. suspectus completed its life cycle on several plant species in the laboratory (albeit at a much lower level than on M. quinquenervia ), in the field, feeding damage is restricted to Melaleuca spp. in the M. leucadendra (L.) L. complex, and rarely, Callistemon spp. The narrow host-range, broad habitat tolerances, and extensive damage caused by this insect should make it a valuable biological control agent if released in Florida.

Pectic Zymograms and Water Stress Tolerance of Endophytic Fungi Isolated from Western Australian Heaths (Epacridaceae)

Forty-nine isolates of root-inhabiting fungi were obtained from thirteen species of eleven genera of native Epacridaceae and compared in relation to host taxonomy and habitat of origin. Pectic zymograms of extracts of the cultured endophytes showed a marked degree of homogeneity of banding patterns amongst isolates from a mesic wetland site, whereas those from dryland habitat displayed more heterogenous banding. It is speculated that host species can operate with only a limited number of fungal associates under mesic conditions but require a higher degree of endophyte variation when combating dry and impoverished environments. Considerable distinction between the geographically diverse endophytes isolated from the common host Lysinema ciliatumsuggested that selection of endophytes was not driven primarily by host taxonomy. Ascribing functional significance to the observed differences between endophytes was studied by examining responses of cultured isolates to polyethylene glycol induced-water stress covering a range of potentials from -0.16 to -2.96MPa. Three response types were observed: ( a) the isolate produced minimal radial growth at all water potentials tested, ( b) maximum growth of the isolate occurred under least water stress, with progressive suppression of radial extension with decreasing water potential and ( c) maximum growth of the isolate occurred under a degree of water stress. The broad range of responses to water stress observed was suggested to reflect the diverse habitat tolerance displayed by epacrids and their endophytic partners in south west Australia.

Breeding Biology and Ecology of Different European and Asiatic Populations of the Great Reed Warbler Acrocephalus arundinaceus

A comparison between various populations of the Great Reed Warbler Acrocephalus arundinaceus was made using published and unpublished data. The comparison showed that most differences are consistent with a division into subspecies. The majority of birds from the nominate subspecies go through a complete moult in late autumn in north Africa, and then continue migration to winter quarters south of the equator. The majority of the eastern subspecies moult completely just after the breeding season. In contrast the orientalis birds spent extremely short periods on migration and long periods in the winter quarters. Orientalis also show more habitat tolerance (breeding in bushes, small trees, and no water), higher breeding density, less nestling starvation, and more Cuckoo Cuculus canorus brood-parasitism. However, some of these features may be due to the fact that some of orientalis populations live in extremely changed (man-made) habitats. On the other hand, clutch-size, total nest-losses, eggs hatchability, fledglings production, and nestling diet composition showed interpopulation variation independent of the subspecies division.

Inferring biome associations of recent mammals from samples of temperate and tropical faunas: Paleoecological considerations

Reconstruction of past faunal assemblages is of primary concern to paleontologists because it yields important information concerning patterns of community structure, biogeography, and paleoclimatology. Unfortunately, the process of fossilization is serendipitous at best, resulting in fossil beds that only contain a sample of the extant fauna that existed at the time of fossilization. Herein, we examine the degree to which incomplete sampling of four well‐known small mammal faunas gives rise to uncertainty concerning the biome association of each site using neontological data from two tropical (Brazilian Cerrado and Gallery Forest) and two temperate (Kansas Prairie and Kentucky Mixed Deciduous‐coniferous Forest) areas. Two simulation approaches (variable and fixed sample sizes) were applied to each set of data to ascertain what proportion of the mammal fauna must be sampled before inferring the correct biome to which the fauna pertained. In the variable sample size approach, species were selected at random from the species pool until the sample correctly identified the biome from which the sample was obtained; this was repeated 200 times for each of the 4 sites. In the fixed sample size approach, a series of simulations were conducted in which each simulation had a fixed number of species, beginning at 2 and increasing at regular intervals until the entire fauna was included in the sample. The number of species required to correctly associate a site with the proper biome was highly variable for three of the four sites. As a result, the number of species required in a sample to be 95% certain of the biome association of Mixed Deciduous‐coniferous Forest, Prairie, and Gallery Forest sites represented a large proportion of the fauna in each case (78%, 88%, and 89%, respectively). In contrast, only 23% of the fauna needed to be sampled from the Cerrado site to obtain the same level of confidence. Adjusting the Cerrado analysis for the effect of endemic species only resulted in an inflation of this value to 33%. The effects of endemics in reducing the certainty of biome associations are only pronounced when sample sizes are small compared to the total species pool. The accuracy of estimating the correct biome association of a fauna is predicated upon the proportion of the fauna in the sample as well as the particular distributional patterns of the species that compose the fauna. Caution should be exercised when inferring the biome association of fossil sites because neither of these features of the sample are usually known. Moreover, even when these features are know, as in the neontological analyses, a large proportion of the fauna frequently is required to be confident of the correct biome association of the fauna. Results indicate that the body size of species found in a fossil assemblage or their ordinal taxonomic affinities can affect the probability of accurately deducing paleoenvironments. Smaller species, and members of the orders Rodentia or Insectivora, are more stenotopic than larger species, or members of the orders Artiodactyla and Carnivora. Fossil assemblages containing only members of the latter groups will consist of wide‐ranging species of broad habitat tolerance. Thus the paleoenvironment of such a fossil assemblage will be difficult to discern.

Modeling Habitat Requirements of a Euryhabitat Species

Statistical models were developed to predict occurrence and standing crops of green sunfish (Lepomis cyanellus) in stream habitats. Individual stream parameters were correlated with standing crop and occurrence, but in combination did not totally define preferred habitat. Habitat requirements of species such as green sunfish, which have wide habitat tolerances, do not appear to be either entirely or largely dependent on physical and chemical factors.

The loss of seagrasses in Cockburn Sound, Western Australia. I. The time course and magnitude of seagrass decline in relation to industrial development

The areas of seagrass meadows in Cockburn Sound, a marine embayment in Western Australia, were estimated from historical aerial photographs supplemented by ground surveys, studies on meadows in adjoining areas, and coring for rhizome remains. Ten species of seagrasses with different habitat tolerances are recorded for the area, with Posidonia sinuosa Cambridge et Kuo forming the most extensive meadows. It is estimated that from 1954 to 1978 the meadow area was reduced from some 4200 to 900 ha. Based on measurements of aboveground productivity at several sites, this represents a reduction of leaf detritus production from 23 000 to 4000 t (dry wt.) y −1. The major loss of seagrass occurred during a period of industrial development on the shore, and the discharge of effluents rich in plant nutrients.

Patterns of Coexistence in Synaptomys Cooperi and Microtus Pennsylvanicus

The microtine rodents Synaptomys cooperi and Microtus pennsylvanicus are sympatric, have a similar life styles, and occur in the same general habitats. The object of this study was to determine the importance of competition in a Microtus—Synaptomys system in southwestern Virginia as a test of the general hypothesis that herbivorous rodents compete directly for space and indirectly for food. The following patterns were observed: (1) Undisturbed populations of Microtus and Synaptomys exhibited microhabitat partitioning when coexisting in heterogeneous habitats that were marginal for Microtus. (2) In the presence of Microtus, Synaptomys microhabitats were characterized by significantly higher densities of deciduous trees and shrubs. (3) Disappearance of Microtus from some habitats during a population decline was accompanied by a shift of Synaptomys into areas formerly occupied by Microtus. Recolonization by Microtus resulted in a return to the previous pattern of microhabitat segregation. (4) Removal of Microtus from an experimental grid was followed by immediate colonization by Synaptomys. (5) One year following removal of Synaptomys from an experimental grid, most of the former Synaptomys habitat remained empty even though Microtus numbers were increasing. (6) Fecal analysis indicated that Synaptomys diet consisted largely of vegetation that is low digestible nutrients (Andropogon in summer, moss in winter). Although Microtus ate Andropogon, this species included more dicotyledons and other monocotyledons in its diet. (7) When Synaptomys was living on a grid from which Microtus had been removed, similarity to food habits of Microtus previously living on the removal grid was much greater than on a grid where the two species coexisted in separate microhabitats (72 vs. 37%). These results suggest that in the southern Appalachians, Synaptomys is excluded from preferred habitats by Microtus and, as a result, lives where cover is sparse and food is low in nutritional value. Although these species do compete, this competition is relaxed when Microtus populations decline. When given access to preferred habitats the food habits of Synaptomys change and resemble those of Microtus, suggesting that the ultimate limiting resource is food. The combination of wider habitat tolerances by Synaptomys and temporal variation in intensity of competition allows coexistence of these species on a regional basis.

An Ecological Study of the Bryophytes of a Natural Prairie in Northwestern Iowa

An Ecological Study of the Bryophytes of a Natural Prairie in Northwestern Iowa

Habitat Separation between Phrynosoma douglassi and P. orbiculare (Lacertilia: Iguanidae) in Mexico

The elevational ranges and habitat tolerances of Phrynosoma douglassi and P. orbiculare are similar in allopatry. In the region of geographical overlap in northern Mexico, where the distributions are parapatric and interdigitate in complex fashion, the realized niches of both species are substantially reduced and different. P. orbiculare is largely confined to montane woodland and forest habitats above 1,889 m, and P. douglassi occupies grasslands usually below 2,194 m. P. douglassi shows ecological release immediately outside the range of P. orbiculare. The diets of both species are similar (dietary overlap = 0.91), consisting of a variety of terrestrial insects, especially ants, and other arthropods. Limited data suggest a dietary shift at one locality where the two Phrynosoma coexist. The hypothesis of exploitative competition explains the ecological and distributional relationships, although other factors, alone or in combination, have not been ruled out.

Predictive Models of Benthic Macroinvertebrate Density for Use in Instream Flow Studies and Regulated Flow Management

As an adjunct to the U.S. Fish and Wildlife Service incremental method for determining habitat suitability for sport fish species at various discharge levels, we propose a similar method for determining optimum conditions for stream macroinvertebrates that stresses predictions of density maxima and flow predictions for maintenance of suitable lotic habitat.The curve fitting equations of the computer simulation showed high reliability in predicting physical habitat tolerances of selected aquatic insects. An example using Nectopsyche lahontonensis is presented.The new predictive model, by exponential polynomial analysis, answers criticisms of earlier models which do not include the dependence of velocity and depth in stream channel hydraulics. The added cross-product term in the model altered the predicted peak responses (density) with random changes in depth and velocity. Although the new model improves the predictions, its effectiveness in stream management has yet to be tested.Key words: habitat suitability, macroinvertebrates, exponential polynomial analysis, flow management, Nectopsyche lahontonensis

The Effect of Sigmodon Hispidus on Spatial and Temporal Activity of Microtus Ochrogaster: Evidence for Competition

Spatial and temporal activities of cotton, rats Sigmodan hispidus, and prairie voles, Microtus ochrogaster, in an old—field habitat in northeast Kansas, USA were studied for 39 mo. During a major portion of the S. hispidus reproductive season the species were spatially segregated but co—occurred the rest of the year. Following a local extinction of cotton rats, prairie voles established a resident population in habitats formerly occupied by cotton rats that was greater than or equal to the vole population in areas which had never been occupied by cotton rats. Comparison of vole population size before and after the loss of cotton rats indicated that cotton rats produced a negative effect on vole population size during the period of spatial segregation but not during the period of spatial co—occurrence. Comparison of vole activity patterns indicated that, with the loss of cotton rats, voles shifted their activity during times when the species had co—occurred but not during periods when they were spatially segregated. Studies of behavioral interaction in a large (4 m x 4 m) arena with varying densities of vertical wires indicated that during single species tests voles and cotton rats preferred the densest areas. Their diel activity patterns were broadly overlapping. In the presence of nonreproductive cotton rats, voles continued to use the same areas as during the control tests but shifted their temporal activity reducing overlap with cotton rats. Interspecific encounters resulted in voles avoiding cotton rats even in the absence of overt aggression. In the presence of reproductive cotton rats, voles shifted their arena usage toward areas least used by cotton rats. Total nocturnal activity by voles was the same as during the control tests but was restricted to hours when cotton rats were least active. Reproductive cotton rats showed higher levels of interspecific aggression than did nonreproductive cotton rats. Voles in the presence of reproductive cotton rats showed increased frequency of serious wounds and deaths, and decreased mass when compared to voles in the presence of nonreproductive cotton rats. We conclude that cotton rats produce a negative effect on prairie vole populations but that the interaction is restricted to the cotton rats' reproductive season. Coexistence of the species appears to rely on the seasonality of the interaction, habitat heterogeneity, and the wider habitat tolerance of prairie voles.

The substrate preference and burrowing behaviour of juvenile lobsters (Homarus gammarus(L.))

Summary Information is sparse on the ecology of the larval and juvenile stages of the lobster (Homarus gammarus (L.)). A knowledge of the distribution and particularly the abundance of this species is vital for the development of stock-recruitment theory. Attempts were therefore made to determine the distribution of juvenile lobsters in the field by Scuba diving and the fishing of small mesh traps. As these initial attempts were of very limited success, lobsters were reared in the laboratory to study their substrate preferences and behaviour. Juvenile lobsters (∼8 mm carapace length) selected coarse substrates which offered suitable crevices, or burrowed extensively in fine, cohesive mud. The rock crevice habitat is widely used by adult lobsters, but the construction of complex mud burrows has not previously been described for this genus. The burrowing behaviour of juvenile lobsters and the structure of the burrows are discussed. Juvenile lobsters appear to have wide habitat tolerances enabling them to inhabit a variety of substrate types. The estimation of juvenile lobster abundance is likely to be extremely difficult.

Velamen and exodermis characters of West African epiphytic orchids in relation to taxonomic grouping and habitat tolerance

The velamen and exodermis of roots of 76 species of epiphytic orchids occurring in West Africa were examined and evaluated for the following characters: number of velamen layers; wall striations and hairs of the velamen; wall thickening and lignification of velamen and exodermal cells; size, and uniformity in shape and size, of velamen and exodermal cells. The term epi-velamen is proposed for the distinctive outermost layer of multi-seriate velamen. High correlation is reported between the number of velamen layers and taxonomic as well as habitat-tolerance groupings, together with lower, but still appreciable, correlation between the other characters evaluated and taxonomic and habitat-tolerance groupings.

Climbing Behavior of Peromyscus floridanus and Peromyscus gossypinus

Field observations and a laboratory test indicate that Peromyscus gossypinus is a more active climber than P. floridanus. Subjects conceived and raised in the laboratory tended to perform more poorly on the climbing test than did wild-caught animals. The greater arboreal tendency of gossypinus may contribute to its wider distribution and broader habitat tolerance, as compared to floridanus, by allowing it to exploit more effectively the resources of the environment. Difference in three-dimensional space utilization of the two species also may serve to reduce competition between them in areas of sympatry. The interspecific variation in climbing activity appears to involve both psychological and morphological adaptations, with the former being of relatively greater importance. Tail length is not correlated with climbing ability in these species. The principal morphological adaptation for climbing appears to be relative development of the plantar tubercles. Two isolated populations of floridanus from different habitat types showed greater divergence in climbing activity than gossypinus stocks from the same localities and habitats. The difference in climbing tendency of the two floridanus populations is believed to be related to the accessibility and general abundance of acorns in their respective habitats.

Chilean Bird Distribution

The results of bird censuses from 13 Chilean habitats are presented. Any one habitat supports a slighly higher bird species diversity than structurally similar habitats in North America and Australia. The bird species turnover between habitats in the same locale, in contrast to other temperate areas, is very low–an island characteristic. Turnover between geographically distinct habitats within Chile is comparable to that between adjacent habitats in North America. Chilean birds exhibit wide habitat tolerance in narrow geographic areas, whcih is attributed to a slow development rate of this bird fauna. Character convergence, where similarities in appearance have evolved to faciliate interspecific aggression and aggregation, is a byproduct of this type of distribution.

Birds and Vegetation Between Perth and Adelaide

A general account is given of the country and bird-life between Perth and Adelaide as seen on the Preliminary Survey of the first British Museum Harold Hall Australian Expedition in December, 1962. The country is divided into three broad Ecological Sections while, for ease of comparison, the route is divided into eight arbitrary and smaller sections. A broad account of the vegetation for each section is given revealing some problems of habitat terminology and emphasizing (a) the complex variety of vegetation, (b) its general continuity in various forms suitable to a number of bird species despite the aridity of the central region. The native (112) and introduced (6) bird species recorded are listed with sectional distribution and habitat notes for each, and the lists of three other observation parties are included for information. Analyses in limited form (a) lists of species recorded in each route section and each Ecological Section, and (b) table of species noted in each of nine selected broad habitats] are given. The number and variety of species of the central regions, and the habitat tolerance of many species, are shown as rather greater than might he expected. Despite the shortcomings of the data the semi-continuity of vegetation is seen a, a factor of probable importance in this. The presence of an ecological gap west of Fowlers Bay is discussed and this and other topics are suggested as being of significance for future study.

A comparative study on the habitat preference and home range of four species of the Genus Emberiza on peat grassland

1. During 14-21, June, 1968, the habitat preference, home range and interspecific relations of four species of the genus Emberiza were investigated at Ishikari-Hutomi, Hokkaido.2. The four species studied and their population densities were: E. schoeniclus, 1.6 bds/ha, E. aureola, 0.6 bds/ha, E. fucata, 0.5 bds/ha and E. spodocephala, 0.2 bds/ha.3. The habitat had the following five types of vegetation: Sasa, Miscanthus, Phragmites, Myrica and bush. E. schoeniclus had the widest habitat tolerance except for bush-type vegetation, whereas the habitats of E. aureola, E. fucata and E. spodocephala tended to be confined to the areas of Sasa, mixed Sasa-Miscanthus and bush types respectively.4. E. schoeniclus nested in the mixed Sasa-Miscanthus type and the feeding ground included Phragmites type with a tendency to form an oval-shaped home range extended toward reed bed. The singing area was around the nesting site and the song-post was selected on a stem of tall grass in most cases. Some nests were concentrated to form a loose colony with distances of about 20m. Such a colony was located near a wide reed bed where it used as feeding ground. A pair and also a bird of the same pair tended to have separate, and therefore not common, feeding grounds.5. The home range of H. aureola was very large and less overlapped. It had two singing areas, the one was the central singing area near or around the nesting site and the other was used as the area for song-duels against the neighboring males. This area was 100 to 200m apart from the nesting site. The nest sites were in short grass areas of Sasa type, but the song-posts were at the top of small bushes. Nests tended to be concentrated but not forming a colony as in E. schoeniclus. At home range boundaries, some chases and actual combats were observed frequently.6. The home range of E. fucata was selected in short grass areas of mixed Sasa-Miscanthus types, with song posts on the top of small bushes. The nest sites were dispersed at regular distances and never in the form of a colony. The singing area was around the nesting site. The feeding ground was both the short grass areas of Sasa type and bare grounds with scattered short grasses. Any direct relationships between the singing area and feeding ground or between the feeding grounds of female and male were noticed.7. E. schoeniclus-E. yessoensis type home range related to tall grass area has a possibility to become compressed into a loose colony with wide feeding ground separated from the nesting site.8. E. fucata-E. cioides type home range related to short grass areas with scattered bushes, has not the possibility to form a colony. Such home ranges are dispersed at regular distances within the habitat.9. E. aureola and E. fucata selected similar habitat and competition seemed to exist between them, but not with E. schoeniclus. As a consequence, E. aureola and E. fucata tended to avoid the habitat overlap, but no competition was noticed either between E. aureola and E. schoeniclus or between E. fucata and E. schoeniclus.