Competitive reversals inside ecological reserves: the role of external habitat degradation

1998 ◽  
Vol 37 (6) ◽  
pp. 491-533 ◽  
Author(s):  
Robert Stephen Cantrell ◽  
Chris Cosner ◽  
William F. Fagan
Keyword(s):  
Habitat Degradation

scholarly journals Defining the niche for niche construction: evolutionary and ecological niches

2021 ◽  
Vol 36 (3) ◽  
Author(s):  
Rose Trappes
Keyword(s):  
Evolutionary Biology ◽  
Ecological Niche ◽  
Niche Construction ◽  
Habitat Degradation ◽  
Ecological Niches ◽  
Niche Concept ◽  
Definition Of ◽  
Compare And Contrast ◽  
Extreme Habitat

AbstractNiche construction theory (NCT) aims to transform and unite evolutionary biology and ecology. Much of the debate about NCT has focused on construction. Less attention has been accorded to the niche: what is it, exactly, that organisms are constructing? In this paper I compare and contrast the definition of the niche used in NCT with ecological niche definitions. NCT’s concept of the evolutionary niche is defined as the sum of selection pressures affecting a population. So defined, the evolutionary niche is narrower than the ecological niche. Moreover, when contrasted with a more restricted ecological niche concept, it has a slightly different extension. I point out three kinds of cases in which the evolutionary niche does not coincide with realized ecological niches: extreme habitat degradation, commensalism, and non-limiting or super-abundant resources. These conceptual differences affect the role of NCT in unifying ecology and evolutionary biology.

Effects of riparian woody vegetation on EPT functional connectivity in Western Germany

2021 ◽  
Author(s):  
Andrés Peredo Arce ◽  
Martin Palt ◽  
Martin Schletterer ◽  
Jochem Kail
Keyword(s):  
Water Pollution ◽  
Functional Connectivity ◽  
Riparian Vegetation ◽  
Habitat Degradation ◽  
Riparian Forest ◽  
Landscape Connectivity ◽  
Riparian Forests ◽  
Coniferous Forests ◽  
Western Germany

<p>In the degraded European landscapes riparian corridors had have become key features to maintain connectivity between habitat patches for multitude of organisms. This role of riparian forests has been assessed from the purely structural point of view, to complex models specific for particular species or groups of species, from mammals to plants, from endangered to invasive species.</p><p>Dispersion is a key part of the lifecycle of EPTs (Ephemeroptera, Plecoptera and Trichoptera) as they live most of their lives as aquatic juveniles, being drifted downstream, and disperse back upstream when they become short-lived winged adults. These three families of aquatic macroinvertebrates are widely used as bioindicators because of their sensitivity to water pollution and habitat degradation, but little is known about how the riparian vegetation impacts their ability to disperse and recolonize. For example, riparian vegetation could help EPTs dispersion by protecting them from harsh weather conditions, or by helping them to orientate themselves by changing how the reflexion of the light on the water polarises.</p><p>Nevertheless, connectivity is not the only driver of the EPT community as other parameters can have a direct effect on the community composition. For example, water pollution is an important driver of the freshwater macroinvertebrate community and in locations where pollution is high is not expected to find almost any EPTs individual regardless of the landscape connectivity. Furthermore, other landscape features can hinder the role of riparian forests as corridors for being a barrier to EPT dispersion, like dams or coniferous forests.</p><p>In this study we compare the EPT communities on 120 pairs of sites, each pair located in the same river at 1 to 5 km distance, with different riparian vegetation conditions in Western Germany. The communities are characterised by their overall dispersion capacity using the Species Flying Propensity index (Sarremejane et al. 2017). The riparian vegetation is identified using areal images in the 10 meters and 30 meters buffer from the river.</p><p>We expect that riparian forest fragmentation will directly impact functional connectivity, and therefore, in locations with less fragmented riparian forests the EPT community will be mainly composed by weak dispersers (and <em>vice versa</em>). Nevertheless, covariates that can impact or mask this effect were taken into account: catchment land use, saprobic pollution, naturalness, hidromorphological hydromorphological degradation and also other features as coniferous forests or dams.</p>

scholarly journals Acacia invasion is facilitated by landscape permeability: The role of habitat degradation and road networks

2020 ◽  
Vol 23 (4) ◽  
pp. 598-609
Author(s):  
Gustavo Heringer ◽  
Jan Thiele ◽  
Cibele Hummel Amaral ◽  
João Augusto Alves Meira‐Neto ◽  
Fabio Antonio Ribeiro Matos ◽  
...  
Keyword(s):  
Habitat Degradation ◽  
Road Networks ◽  
Landscape Permeability

Evaluating the role of invasive aquatic species as drivers of fine sediment-related river management problems: The case of the signal crayfish (Pacifastacus leniusculus)

2011 ◽  
Vol 35 (4) ◽  
pp. 517-533 ◽  
Author(s):  
Gemma L. Harvey ◽  
Tom P. Moorhouse ◽  
Nicholas J. Clifford ◽  
Alexander J. Henshaw ◽  
Matthew F. Johnson ◽  
...  
Keyword(s):  
Invasive Species ◽  
Habitat Degradation ◽  
River Sediments ◽  
Large Body ◽  
Aquatic Organisms ◽  
Mitigation Strategies ◽  
Catchment Scale ◽  
Signal Crayfish ◽  
River Bed

Sediment quantity and quality are key considerations in the sustainable management of fluvial systems. Increasing attention is being paid to the role of aquatic biota as geomorphic agents, capable of altering the composition, mobilization and transport of fluvial sediments at various spatiotemporal scales. In this paper invasive species are presented as a special case since: (1) populations may not be constrained by factors characteristic of their native habitats; and (2) they represent a disturbance to which the system may not be resilient. Discussion is centred on the signal crayfish which has rapidly colonized catchments in Europe and Japan, but the hypotheses and models presented provide a framework applicable to other invasive species. This paper explores the mechanisms by which signal crayfish may influence sediment dynamics from the patch scale to the catchment scale. There is potential for signal crayfish to impact significantly on river sediments and morphology as a function of their interactions with river bed and bank material, and with other aquatic organisms, combined with their large body size and aggressive nature, their presence in very high densities, and the lack of effective mitigation strategies. Potential catchment-scale management issues arising from these factors include habitat degradation, mobilization of sediment-associated nutrients and contaminants, and sediment-related flood risks. Further interdisciplinary research is required at the interface between freshwater ecology, fluvial geomorphology and hydraulics, in order to quantify the significance and extent of these impacts. The paper points to the key research agendas that may now emerge.

scholarly journals Biodiversity Patterns of Macroinvertebrate Assemblages in Natural and Artificial Lentic Waters on an Oceanic Island

2021 ◽  
Vol 8 ◽  
Author(s):  
Lucas Lamelas-López ◽  
Paulo A. V. Borges ◽  
Laura Serrano ◽  
Vitor Gonçalves ◽  
Margarita Florencio
Keyword(s):  
Habitat Degradation ◽  
Temporary Ponds ◽  
Macroinvertebrate Assemblages ◽  
Β Diversity ◽  
Spatial Influence ◽  
Physico Chemical ◽  
Monthly Pattern ◽  
High Concentrations ◽  
Lentic Waters

The Azorean islands have been historically affected by human activities, mainly due to the combined effects of habitat degradation and fragmentation, and the introduction of exotic species. We here aim to analyze the role of environmental characteristics and spatial descriptors in supporting regional biodiversity of macroinvertebrates by considering natural ponds and artificial tanks. After the monthly variation of macroinvertebrate assemblages was assessed in three temporary and two permanent ponds in the Azorean island of Terceira during a complete inundation-desiccation annual cycle, the assemblage differences of 12 ponds (three temporary and nine permanent ponds) and 8 closely-located artificial tanks were analyzed across a range of landscape disturbances. Macroinvertebrate assemblages were found to differ according to hydroperiod and sampled months. Although the former explained the highest variance, macroinvertebrate differentiation by hydroperiod was also dependent on the study month. Our results also revealed a consistent monthly pattern of species replacement. However, the contribution of nestedness to the macroinvertebrate β-diversity was notable when temporary ponds were close to desiccation, probably indicating a deterministic loss of species due to the impoverished water conditions of the ponds facing desiccation. When the macroinvertebrate assemblages were analyzed in relation to physico-chemical variations and spatial descriptors, the artificial tanks were not clearly segregated from the natural ponds, and only differentiated by pH differences. In contrast, those natural ponds exhibiting high concentrations of total phosphorous (likely signs of anthropization) also discriminated the ordination of ponds in a distance-based redundancy analysis, and showed impoverished assemblages in comparison with well-preserved ponds. The macroinvertebrate assemblages of the natural ponds showed a significant spatial pattern, but this spatial influence was not significant when tanks and ponds were considered together. Our results suggest that tanks may act as possible reservoirs of biodiversity during the desiccation period of temporary ponds, but are unable to establish successful populations. These fishless permanent tanks can complement the conservation of a biodiversity that is largely maintained by the pristine high-altitude natural ponds. The establishment of a guideline for conservation management that also considers the artificial tanks is necessary to benefit the local and regional Azorean macroinvertebrate diversity.

scholarly journals Arbuscular Mycorrhizal and Root Colonizing Dark Septate Endophyic Fungal Associations in Urginea indica and Urginea wightii Accessions

2020 ◽  
pp. 11-16
Author(s):  
B. Mohana ◽  
Shiva Kameshwari ◽  
Hanumanth Rao
Keyword(s):  
Habitat Degradation ◽  
Arbuscular Mycorrhizal ◽  
Dark Septate Endophyte ◽  
Terrestrial Habitats ◽  
Fungal Symbiosis ◽  
Fungal Association ◽  
Fungal Associations ◽  
Urginea Indica ◽  
Over Exploitation

Urginea indica belongs to Hyacinthaceae family. It is also known as Indian squill, commonly called as wild Onions. The over exploitation and habitat degradation has resulted in the loss of habitat and it has caused genetic depletion and loss of genetic diversity. Immediate Measures have to be undertaken for conservation, to save this economically important medicinal plant. The present investigation is an attempt to highlight the occurance of arbuscular mycorrhizal (AM) and Dark Septate Endophyte (DSE) fungal association found in the root bulbs of Urginea indica. 8 Accessions of Urginea was examined in Urginea indica kunth and Urginea wightii accessions, collected from various regions of Karnataka and South India. Fungal Symbiosis was present in all the accessions, with 100% root infection. Urginea has DSE fungal association and AM Association. This is the first report on the DSE fungal association in Urginea indica kunth. In addition to the prevalance of AM fungal symbiosis. The role of DSE is still in infancy. Though noclear relationship between AM and DSE fungal colonizations was recognized. Our studies suggests the coexistence of AM and DSE fungal colonizations are common terrestrial habitats especially the xerophytic environment. DSE-plant symbiosis should not be limited to nutritional uptake but mediates other parameters such as drought resistance, stress tolerance and herbivore resistance. Our results show 100% infection by AM and DSE fungal colonies. Infection levels were high throughout the year, the highest levels occurring in the most nutrient-stressed situations. Their occurrence and variaton in different accessions is discussed below.

scholarly journals Molecular characterisation of haemoparasites in forest birds from Robinson Crusoe Island: Is the Austral Thrush a potential threat to endemic birds?

2014 ◽  
Vol 25 (2) ◽  
pp. 139-152 ◽  
Author(s):  
JAVIER MARTÍNEZ ◽  
RODRIGO A. VÁSQUEZ ◽  
CRISTOBAL VENEGAS ◽  
SANTIAGO MERINO
Keyword(s):  
Habitat Degradation ◽  
Bird Species ◽  
Forest Birds ◽  
Blood Parasites ◽  
Robinson Crusoe ◽  
Potential Threat ◽  
Endemic Birds ◽  
Sephanoides Fernandensis ◽  
Sephanoides Sephaniodes

SummaryThe Juan Fernández Firecrown Sephanoides fernandensis and Juan Fernández Tit-Tyrant Anairetes fernandezianus are two endemic forest birds inhabiting Robinson Crusoe Island and are classified as ‘Critically Endangered’ and ‘Near Threatened’ respectively by IUCN. Previous research concluded that the two main factors involved in the decline of these birds were habitat degradation and the introduction of predator / competitor species. However, the potential role of parasitic diseases has not yet been explored. In order to explore hypothetical host-switching phenomena, we genetically identified the haemoparasites present in four bird species, the two endemic species mentioned above and two recent colonisers, Green-Backed Firecrown Sephanoides sephaniodes and Austral Thrush Turdus falcklandii. We failed to find infections by different blood parasites (Plasmodium, Haemoproteus, Leucocytozoon, Trypanosoma, Babesia and Isospora) in the endangered Juan Fernández Firecrown. However, the Juan Fernández Tit-Tyrant was infected with some parasites shared with the Austral Thrush. The latter species may function as a key-host species on the island as it showed both the higher hemoparaasitic diversity and prevalence. The role of Green-Backed Firecrowns is apparently of lower importance because only one individual was found parasitized. The Austral Thrush could be responsible of the introduction of some parasites also isolated from the Juan Fernández Tit-Tyrant and represent a potential threat to the endemic firecrown due to its role as a reservoir. The spread of Austral Thrushes could increase the contact between species, increasing the probability of a switching event.

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