Diversity2015, 7(3), 229-241; doi:10.3390/d7030229 - published 26 June 2015 Show/Hide Abstract
Abstract: Community saturation can help to explain why biological invasions fail. However, previous research has documented inconsistent relationships between failed invasions (i.e., an invasive species colonizes but goes extinct) and the number of species present in the invaded community. We use data from bird communities of the Hawaiian island of Oahu, which supports a community of 38 successfully established introduced birds and where 37 species were introduced but went extinct (failed invasions). We develop a modified approach to evaluate the effects of community saturation on invasion failure. Our method accounts (1) for the number of species present (NSP) when the species goes extinct rather than during its introduction; and (2) scaling patterns in bird body mass distributions that accounts for the hierarchical organization of ecosystems and the fact that interaction strength amongst species varies with scale. We found that when using NSP at the time of extinction, NSP was higher for failed introductions as compared to successful introductions, supporting the idea that increasing species richness and putative community saturation mediate invasion resistance. Accounting for scale-specific patterns in body size distributions further improved the relationship between NSP and introduction failure. Results show that a better understanding of invasion outcomes can be obtained when scale-specific community structure is accounted for in the analysis.
Diversity2015, 7(3), 206-228; doi:10.3390/d7030206 - published 26 June 2015 Show/Hide Abstract
Abstract: Marine protected areas are commonly seen as the most effective strategy for protecting mangroves from external human pressures but little is known about the role of public land-tenure contexts (dense settlements, agricultural or range lands and wild anthromes) on clearing rates, patch properties, and ecological condition. We addressed the following questions using a peri-urban to wild gradient along the anthropogenic coastal-scape in Turbo Municipality (Colombia, Southern Caribbean): Do the different deforestation rates observed under peri-urban, rural, military-protected and wild land-use-and-tenure contexts, promote distinctive fragmentation patterns? Do these patterns influence loggers’ access and ultimately ecosystem ecological condition? Loss rate (1938–2009) was the greatest peri-urban mangroves and positively correlated with urban edge and patch density. Pasture edge was highest in rural mangroves while mean patch area was higher in protected and wild mangroves. An Anthropogenic Disturbance Index (ADI) was strongly correlated with reduced mean patch area and increased patch density, due to increased trampling and logging, that ultimately promoted high densities of thin (diameter: <5 cm) Laguncularia racemosa trees but had no significant effect on the presence of a dominant benthic gastropod. In conclusion, both protection and remoteness were effective in reducing anthropogenic edges and fragmentation, and thus contributed to a high ecological condition in mangroves at a major deforestation hotspot.
Diversity2015, 7(2), 195-205; doi:10.3390/d7020195 - published 17 June 2015 Show/Hide Abstract
Abstract: A total of 77 giant Pacific octopus, Enteroctopus dofleini, tissue samples were collected from the Oregon Coast (OR), Neah Bay Washington (NB), Puget Sound Washington (PS) and the southeast coast of Vancouver Island, British Columbia, Canada (BC) for genetic analyses. A suite of eight variable microsatellite markers developed from giant Pacific octopuses were amplified in these samples to determine population diversity, structure, relatedness and paternity. The majority of loci met Hardy-Weinberg equilibrium expectations within each population. We found moderate genetic diversity (average observed heterozygosity = 0.445, range = 0.307–0.515 and average expected heterozygosity = 0.567, range = 0.506–0.696) and moderate population structuring with distinct separation of groups (FST values ranged from 0.101 between BC and PS to 0.237 between BC and NB). Several egg strings from the BC population were collected from three female octopus dens for relatedness and paternity analyses. Results suggest strong support for multiple paternity within one egg clutch with progeny sired by between two to four males.
Diversity2015, 7(2), 170-191; doi:10.3390/d7020170 - published 9 June 2015 Show/Hide Abstract
Abstract: Human pressure on ecosystems is among the major drivers of biodiversity loss. As biodiversity plays a key role in supporting the human enterprise, its decline puts the well-being of human societies at risk. Halting biodiversity loss is therefore a key policy priority, as reflected in the 2020 Aichi Biodiversity Targets under strategic goal A. The Ecological Footprint has become a widely used metric for natural capital and ecosystem accounting, and is frequently cited in the sustainability debate, where it is often used for tracking human-induced pressures on ecosystems and biodiversity. Given its potential role as an indirect metric for biodiversity-related policies, this paper breaks down the Ecological Footprint into its components and analyzes resource and ecosystem service flows at an international level. We discuss its usefulness in tracking the underlying drivers of habitat impacts and biodiversity loss. We find that: China is a major net importer of all biomass biocapacity components; the largest net exporters of forest biocapacity are not low-income countries; a very high proportion of the Ecological Footprint of fishing grounds is traded internationally; Singapore and at least three Middle East countries are almost wholly reliant on net imports for the cropland biocapacity they consume.
Diversity2015, 7(2), 149-169; doi:10.3390/d7020149 - published 22 May 2015 Show/Hide Abstract
Abstract: Covering approximately 10,000 km2 the Sundarbans in the Northern Bay of Bengal is the largest contiguous mangrove forest on earth. Mangroves forests are highly productive and diverse ecosystems, providing a wide range of direct ecosystem services for resident populations. In addition, mangroves function as a buffer against frequently occurring cyclones; helping to protect local settlements including the two most populous cities of the world, Kolkata and Dhaka, against their worst effects. While large tracts of the Indian Sundarbans were cleared, drained and reclaimed for cultivation during the British colonial era, the remaining parts have been under various protection regimes since the 1970s, primarily to protect the remaining population of Bengal tigers (Panthera tigris ssp. tigris). In view of the importance of such forests, now severely threatened worldwide, we trace the areal change that the Indian Sundarbans have undergone over the last two-and-a-half centuries. We apply a multi-temporal and multi-scale approach based on historical maps and remote sensing data to detect changes in mangrove cover. While the mangroves’ areal extent has not changed much in the recent past, forest health and structure have. These changes result from direct human interference, upstream development, extreme weather events and the slow onset of climate change effects. Moreover, we consider the role of different management strategies affecting mangrove conservation and their intersection with local livelihoods.