Contrasting Ecosystem-Effects of Morphologically Similar Copepods

Organisms alter the biotic and abiotic conditions of ecosystems. They can modulate the availability of resources to other species (ecosystem engineering) and shape selection pressures on other organisms (niche construction). Very little is known about how the engineering effects of organisms vary among and within species, and, as a result, the ecosystem consequences of species diversification and phenotypic evolution are poorly understood. Here, using a common gardening experiment, we test whether morphologically similar species and populations of Diaptomidae copepods (Leptodiaptomus ashlandi, Hesperodiaptomus franciscanus, Skistodiaptomus oregonensis) have similar or different effects on the structure and function of freshwater ecosystems. We found that copepod species had contrasting effects on algal biomass, ammonium concentrations, and sedimentation rates, and that copepod populations had contrasting effects on prokaryote abundance, sedimentation rates, and gross primary productivity. The average size of ecosystem-effect contrasts between species was similar to those between populations, and was comparable to those between fish species and populations measured in previous common gardening experiments. Our results suggest that subtle morphological variation among and within species can cause multifarious and divergent ecosystem-effects. We conclude that using morphological trait variation to assess the functional similarity of organisms may underestimate the importance of species and population diversity for ecosystem functioning

Successful Removal of a Penile Constriction Ring in a 14-Year-Old Male

Penile strangulation is a rarely described medical emergency, especially in the adolescent population. This case demonstrates the successful removal of a constricting metal ring from the penis of a 14-year-old male with a diamond blade equipped orthopedic oscillating saw while under ketamine anesthesia in the emergency department

Biodiversity and resilience of ecosystem functions

Accelerating rates of environmental change and the continued loss of global biodiversity threaten functions and services delivered by ecosystems. Much ecosystem monitoring and management is focused on the provision of ecosystem functions and services under current environmental conditions, yet this could lead to inappropriate management guidance and undervaluation of the importance of biodiversity. The maintenance of ecosystem functions and services under substantial predicted future environmental change (i.e., their ‘resilience’) is crucial. Here we identify a range of mechanisms underpinning the resilience of ecosystem functions across three ecological scales. Although potentially less important in the short term, biodiversity, encompassing variation from within species to across landscapes, may be crucial for the longer-term resilience of ecosystem functions and the services that they underpin

Ecological distribution and population physiology defined by proteomics in a natural microbial community

Community proteomics applied to natural microbial biofilms resolves how the physiology of different populations from a model ecosystem change with measured environmental factors in situ.The initial colonists, Leptospirillum Group II bacteria, persist throughout ecological succession and dominate all communities, a pattern that resembles community assembly patterns in some macroecological systems.Interspecies interactions, and not abiotic environmental factors, demonstrate the strongest correlation to physiological changes of Leptospirillum Group II.Environmental niches of subdominant populations seem to be determined by combinations of specific sets of abiotic environmental factors

A synthesis is emerging between biodiversity–ecosystem function and ecological resilience research: reply to Mori

Letter

Global change effects on plant communities are magnified by time and the number of global change factors imposed

Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity–ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously

BURROW USE IN A NORTHERN CALIFORNIA POPULATION OF THE WOLF SPIDER SCHIZOCOSA MCCOOKI (ARANEAE, LYCOSIDAE)

Volume: 31Start Page: 433End Page: 43

CLIMATE CHANGE AND GRASSLAND RESTORATION IN CALIFORNIA: LESSONS FROM SIX YEARS OF RAINFALL MANIPULATION IN A NORTH COAST GRASSLAND

Volume: 54Start Page: 225End Page: 23

Recovery dynamics of the Caribbean long-spined sea urchin, Diadema antillarum

The sea urchin Diadema antillarum is a keystone herbivore in the Caribbean and its functional extinction due to an epidemic in 1983 had a marked effect on coral reef health. Recovery of D. antillarum has been associated with improvements in reef health but has been unexpectedly slow and patchy with many populations persisting at low abundance on the reefs. This thesis investigates possible reasons for low and variable recovery of D. antillarum on the reef using combined techniques of population dynamic modelling, meta-analysis and field experimentation. Population dynamic modelling was used to explore the implications of alternative process hypotheses for recovery dynamics. Depensatory density dependence (Allee effects) or cultivation effects are predicted to lead to complex dynamics characterized by switching between alternative, high and low abundance states. Density independent variation in vital rates, e.g. due to environmental change, are predicted to affect recovery abundance and rates without leading to complex dynamics. Time series data explored through meta-analysis, and local recovery patterns examined in Curacao, exhibit recovery dynamics and spatial distributions which indicate that variation in density independent factors, rather than depensatory density dependent processes are the key drivers of population dynamics. Recovering populations and patches of high D. antillarum abundance are both associated with locations which exhibit high resource availability, high macroalgal abundance, few herbivorous fish competitors, reduced predation risk and local larval retention. Specifically, I find evidence to suggest that rates of recovery are determined by resource availability and population sizes are controlled by predation pressure and larval retention. Interestingly, the environmental characteristics which appear favourable to D. antillarum are also characteristics which tend to result from high levels of human threat. My results demonstrate that D. antillarum populations favour specific habitat characteristics which occur in a variety of habitat types and indicate that coral reefs, upon which most attention has been focused, actually represent relatively poor habitat for the species. In light of this, I predict that the widespread reappearance of D. antillarum on coral reefs will only occur once population densities in preferred, sheltered, shallow, nutrient enriched, often humanimpacted habitats become high enough to depress habitat quality in these locations, such that forereefs become suitable as alternative habitats.EThOS - Electronic Theses Online ServiceGBUnited Kingdo