Effects Of Habitat Disturbance Research Articles

Dung Beetle Communities and Seed Dispersal in Primary Forest and Disturbed Land in Amazonia1

Seeds from tropical fruiting trees ingested and defecated on the soil surface by primary dispersers (such as primates) are vulnerable to destruction from rodents, insects, and fungi. Burial by dung beetles as an incidental result of their feeding and nesting activities often provides these seeds with refugia from attack. To examine the effect of habitat disturbance on the dung beetle communities involved in this process, I surveyed dung beetles at three sites in the Amazon basin, in the states of Para, Amazonas, and Rondonia, Brazil. Through principal component analysis on measurements of size and behavioral characters of beetles, I determined the relative quality of beetle species as seed dispersers (dispersal defined as horizontal or vertical movement of seeds) and ranked them into seed dispersal guilds. I used correspondence analysis to examine in what habitats (primary forest or varying degrees of disturbed habitat) these guilds were abundant. Most guilds decreased with increasing habitat disturbance, but one guild made up of large nocturnal burrowers (primarily Dichotomius) became more abundant with increasing disturbance (up to the level of highest disturbance surveyed), at which point all dung beetle species became scarce. Clear-cuts had lower species richness, lower abundance, and lower biomass than forested areas. These results imply that clear-cutting is detrimental to all seed dispersal dynamics in tropical rain forests, but that some levels of disturbance allow enough disperser activity to preserve this ecosystem function.

Effects of Habitat Disturbance and Protected Areas on Mammals of Peninsular Malaysia

Effects of Habitat Disturbance and Protected Areas on Mammals of Peninsular Malaysia

Using species abundance models as indicators of habitat disturbance in tropical forests

1. In temperate communities, species abundance distributions have been used to detect ecosystem disturbance: in undisturbed habitats, distributions are claimed to generally fit log‐normal models, whereas in disturbed habitats, distributions fit log‐series models. 2. There is a growing literature on the effects of habitat disturbance in tropical ecosystems and several studies suggest that species abundance models may be useful in detecting disturbance, although data are lacking. 3. Nummelin (1998) claims that these models are not universal indicators of forest disturbance, but we highlight a number of problems with the data presented in Nummelin's study and conclude that it is too soon to dismiss these models. We discuss several important points arising from Nummelin's study which need to be considered if species abundance models are to be used appropriately.

Disturbance, habitat structure and the ecology of fishes on coral reefs

Abstract This paper reviews empirical studies relating communities of coral‐reef fishes to the characteristics of the underlying habitat, and the effects of habitat disturbance. Many contrasting patterns in the relationships between fish communities and coral cover, habitat heterogeneity or topographic complexity have been described, including strong effects of particular habitat characteristics (both positive and negative), as well as those finding weak or no relationships. In addition, a whole range of potential responses to different kinds of disturbance, including hurricane damage, crown‐of‐thorns (Acanthaster planci) outbreaks, and El Niño‐associated coral and sea urchin die‐offs, have been described. Few workers have attempted to test among alternative models about the importance of resource limitation or responses to disturbance, so critical hypotheses have not been tested. Potential generalizations may be obscured due to a number of problems faced when making comparisons among existing studies. These include the enormous variation in the magnitude of changes to habitats observed, restrictive assumptions about the form of relationships between fish and habitat variables, inadequate descriptions of habitat and fish community structure, a heavy reliance on ‘natural’, pseudoreplicated experiments and a plethora of different numerical and analytical techniques. We conclude that the search for generalizations would be facilitated by a greater attention to theory and clearer statements of the hypotheses being tested. Evaluation of the general importance of fish‐habitat interactions must await the application of common observational and experimental methodologies to a wider range of fish taxa and locations.

Population densities of Sulawesi crested black macaques (Macaca nigra) on Bacan and Sulawesi, Indonesia: effects of habitat disturbance and hunting.

Population surveys of Sulawesi crested black macaques (Macaca nigra) were conducted on the Indonesian islands of Sulawesi and Bacan in 1992-1994 to assess the status of natural populations and determine habitat and anthropogenic factors affecting their population densities. We surveyed five sites for primates, including undisturbed and disturbed habitats. Data were collected on habitat structure and composition at two undisturbed and one disturbed forest site in which the primates were surveyed. The highest density of macaques was found in primary forest at Gunung Sibela Nature Reserve on Bacan (170.3 individuals/km2). Population density in logged forest on Bacan was high but significantly less than primary forest (133.4 individuals/km2). The high density of crested black macaques in primary forest on Bacan is best explained by the high carrying capacity found in primary forest. The lower food quantity and quality of food resources found in logged forest correlated with lower primate densities compared to primary forest. However, the large population of macaques in logged forest demonstrates the conservation value of such forest. Densities on Sulawesi at Tangkoko-Batuangas-DuaSudara Nature Reserve (TBDS) showed a continuing decline since earlier surveys. Primate densities were highest near the protected center of Tangkoko Reserve (66.7 individuals/km2). The peripheral areas of Batuangas and DuaSudara, even though adjacent and continuous, showed lower population densities of 46.4 and 23.5 individuals/km2, respectively. The best explanation for the continued decline of Macaca nigra populations at TBDS is hunting. Unless conservation measures are implemented immediately, M. nigra on Sulawesi risks extinction in the near future.

Population densities of Sulawesi crested black macaques (Macaca nigra) on Bacan and Sulawesi, Indonesia: Effects of habitat disturbance and hunting

Population surveys of Sulawesi crested black macaques (Macaca nigra) were conducted on the Indonesian islands of Sulawesi and Bacan in 1992–1994 to assess the status of natural populations and determine habitat and anthropogenic factors affecting their population densities. We surveyed five sites for primates, including undisturbed and disturbed habitats. Data were collected on habitat structure and composition at two undisturbed and one disturbed forest site in which the primates were surveyed. The highest density of macaques was found in primary forest at Gunung Sibela Nature Reserve on Bacan (170.3 individuals/km2). Population density in logged forest on Bacan was high but significantly less than primary forest (133.4 individuals/km2). The high density of crested black macaques in primary forest on Bacan is best explained by the high carrying capacity found in primary forest. The lower food quantity and quality of food resources found in logged forest correlated with lower primate densities compared to primary forest. However, the large population of macaques in logged forest demonstrates the conservation value of such forest. Densities on Sulawesi at Tangkoko-Batuangas-DuaSudara Nature Reserve (TBDS) showed a continuing decline since earlier surveys. Primate densities were highest near the protected center of Tangkoko Reserve (66.7 individuals/km2). The peripheral areas of Batuangas and DuaSudara, even though adjacent and continuous, showed lower population densities of 46.4 and 23.5 individuals/km2, respectively. The best explanation for the continued decline of Macaca nigra populations at TBDS is hunting. Unless conservation measures are implemented immediately, M. nigra on Sulawesi risks extinction in the near future. Am. J. Primatol. 44:89–106, 1998. © 1998 Wiley-Liss, Inc.

Effect of habitat disturbance on inoculum potential of ericoid endophytes of Western Australian heaths (Epacridaceae)

SUMMARYThe presence of host plants was found to be a key determinant of soil infectivity for endophytes of epacrids growing in south–west Australian jarrah forest carrying a sparse epacrid understorey. A comparable Banksia woodland with higher density of epacrids showed more uniform levels of infective endophytes, presumably because of closer overlap of host–supported patches of endophyte. Disturbed sites in jarrah forest, in which topsoil had been recently returned following bauxite mining, initially showed extremely low endophyte infectivity, probably due to disruption of the hyphal network, absence of host plants and/or increased competition from soil micro–organisms antagonistic to the endophytes. As the system stabilized and epacrids recruited and grew, inoculum potential of the soil re–established and by 12 yr it equalled that of adjacent undisturbed native forest. At disturbed sites with sparsely distributed adult members of the Epacridaceae, endophyte inoculum proved to be adequate only directly adjacent to the epacrids and declined steeply to negligible levels at only 40 cm radially distant from a host plant. The significance of live epacrid root systems on survival of endophyte inoculum in Banksia woodland was examined following removal of shoots of adult plants of the endemic epacrid, Leucopogon conostephioides DC, Coincident with demise of roots of the detopped plants, endophyte inoculum potential of closely adjacent soil declined by 50% during the growing season. However, the effect was short lived and infectivity rose the following year to equal that of undisturbed adjacent woodland as mycelial matrices supported by neighbouring epacrids invaded the depleted study areas.

Effects of habitat disturbance on the behavioral ecology and demographics of the Tana river red colobus (Colobus badius rufomitratus)

Annual surveys in 1985–1987 revealed that, since 1975, the total population of the Tana River red colobus (Colobus badius rufomitratus)declined by approximately 80%. An intensive study in 1986–1988 of two groups of colobus in the Tana River Primate National Reserve indicated that habitat disturbance from the changing river course and shifting agricultural practices were primarily responsible for the decline. Clearcutting around Mchelelo forest in the late 1960s compressed colobus populations to levels probably above the carrying capacity. Between 1975 and 1986 primate population density declined dramatically, the number of red colobus groups in Mchelelo forest decreased by half, and the size of the remaining group was greatly reduced. In 1986, there were fewer solitary colobus and small parties in the forest, harem male takeovers did not occur, infant survivorship increased, and demographic parameters generally had improved. The colobus groups in Mchelelo in 1973–1975, living at higher densities, showed different feeding and ranging behaviors than 1986–1988 groups. Range size was smaller in 1975, range overlap occurred, and a greater portion of the forest was used per day and per month. Mature leaves accounted for a much higher proportion of the diet. Time spent feeding and resting was the same in both studies. Social organization in predominantly one- male groups was maintained and adult and subadult females transferred between groups.

Activity pattern of the brown howler monkeyAlouatta fusca, Geoffroy 1812, in a forest fragment of southeastern Brazil

A group of six brown howlers was studied during a year in the Santa Genebra Reserve, a 250ha-forest fragment near the city of Campinas, State of Sao Paulo, southeastern Brasil. On average, the group rested for 64% of the daylight hours and feeding and moving occupied 18% and 13% of this period, respectively. A greater proportion of time was spent feeding during dry season (24%) than the wet season (15%), and the reverse observed for time spent resting (59% and 69% of the group's daylight hours during dry and wet seasons, respectively). The increase of resting and decrease of feeding during wet season were related to the percentage of leaves in the group's diet, high even during the fruiting season (wet season). However, additional data of other groups are necessary to draw conclusions about the effects of habitat disturbance on this population.

The butterflies (Lepidoptera) of the Tuxtlas Mts., Veracruz, Mexico, revisited: species-richness and habitat disturbance

Checklists of the butterflies (Lepidoptera) collected in two rainforest study sites in the Mts., Veracruz, Mexico are presented. A total of 182 species of butterflies were recorded at Laguna Encantada, near San Andres Tuxtla, and 212 species were recorded from the nearby Estacion de Biologia Tropical Los Tuxtlas (EBITROLOTU). We collected 33 species not included in G. Ross' (1975-77) faunistic treatment of the region, 12 of which are new species records for the Tuxtlas. We present a list of the skipper butterflies (Hesperioidea) of the Tuxtlas, including a state record for the giant skipper, Agathymus rethon. At both study sites, we observed seasonal patterns in species abundance during periods of reduced precipitation. Our data indicate an apparent increase in butterfly species-richness in the over the last 25 years. This increase reflects more efficient sampling due to advances in lepidopteran ecology and improved collecting methods, as well as the effects of habitat disturbance. A comparison between the butterfly faunas of the two rainforest sites revealed that a higher percentage of weedy, cosmopolitan species were present at Laguna Encantada, the smaller, more disturbed site. We anticipate further changes in butterfly species-richness and faunal composition as the mosaic of habitats in the continue to be modified.

Spiders associated with selected European hay meadows, and the effects of habitat disturbance, with the predation ecology of the crab spiders, Xysticus spp. (Araneae, Thomisidae)

AbstractIn hay meadows near Zurich, central Europe, the faunistic composition of the foliage‐dwelling spiders was evaluated using sweep‐net technique. Eleven families were represented from the 1502 spider individuals captured, the majority of which (> 85%) belonged to the families Theridüdae, Linyphiidae, Araneidae, Tetragnathidae, Lycosidae, Thomisidae and Salticidae. Of the adults collected (39 species, N = 203) 38% were orb‐weavers, 33% were irregular or sheet‐web weavers, and 29% were cursorial hunters. The crab spiders (Thomisidae), Xysticus cristatus (Clerck) and X. kochi Thorell, were the species most frequently collected.A low feeding frequency was observed in the field for the Xysticus spp. (<10% with prey, N = 395), and a wide variety of arthropod taxa was consumed by the crab spiders including eight orders of insects, other spider species and a representative from a family of earthworms. Although crab spiders have been noted as voracious predators of large social bees, this category made up only 3% (by number) of the prey. Previous reports found in the literature suggest that crab spiders that hunt on the flower inflorescence feed almost exclusively within a narrow range of pollinating insects, however, no supporting evidence for this contention was found, instead Xysticus spp. in European hay meadows are exceedingly polyphagous.The impact of mowing on meadow spider populations was evaluated using three methods, all yielding evidence that mowing had a negative effect on spider densities. Depending on the circumstances, the impact of mowing on spider densities in a diverse variety of meadows may range from mild to massive, however, emigration by spiders after their habitat has been disturbed, may serve as a beneficial arthropod generator, providing for the colonization of surrounding field crops.ZusammenfassungSpinnen in europäischen Mähwiesen: Artenspektrum, Einfluß der Mahd und Prädatorenökologie der Krabbenspinnen, Xysticus spp. (Araneae, Thomisidae)Die Spinnenfauna von Mähwiesen wurde bei Zürich, Mitteleuropa, studiert. Insgesamt 1502 Spinnen aus 11 Familien (inkl. 203 Adulttiere aus 39 Arten) wurden mit dem Streifnetz gesammelt, wovon >85% den Familien Theridiidae, Linyphiidae, Araneidae, Tetragnathidae, Lycosidae, Thomisidae und Salticidae angehörten. Die netzlosjagenden Thomisidae [= Krabbenspinnen], Xysticus cristatus (Clerck) und X. kochi Thorell, waren die am häufigsten gesammelten Spinnen. Freilandbeobachtungen ergaben, daß die Xysticus spp. sich von einem breiten Spektrum von Beutetieren aus den Taxa Diptera, Hymenoptera, Homoptera, Heteroptera, Thysanoptera, Coleoptera, Lepidoptera, Collembola, Araneae und Oligochaeta ernährten (ausgesprochene Polyphagie), wobei <10% (N = 395) der im Feld angetroffenen Krabbenspinnen freßaktiv waren. Mit 3 verschiedenen Methoden wurde gezeigt, daß die Mahd einen negativen Einfluß auf die Populationsdichten von Wiesenspinnen ausübte. Wir vermuten, daß die ausgedehnten Wiesenflächen innerhalb der mitteleuropäischen Agrarlandschaft eine wichtige Funktion als Prädatorenreservoir für die Besiedlung von angrenzenden Ackerkulturen erfüllen.