Role Of Species In Ecosystems Research Articles

Trophic ecology of juvenile amphibians: relative level of myrmecophagy in two anuran species

ABSTRACT Research on trophic niche dimensions is essential to understanding the role of species in ecosystems. In the case of amphibian conservation, it is particularly important to study juveniles, given the vulnerability of this life stage. Here, the diets consumed by juvenile Rhinella arenarum and Odontophrynus sp. were evaluated, with special attention paid to the incidence of ants. Diet composition was quantified by analyzing the amphibians’ stomach contents. The representation of different taxonomic prey groups was determined, and the relationships between the amphibians’ morphological traits and the characteristics of their prey were explored. Diet composition and diversity differed between juveniles of the two species. Juvenile R. arenarum occupied an intermediate position along the specialist-generalist spectrum. Their most commonly consumed prey were ants (mainly Solenopsis and Linepithema) followed by mites. Juvenile Odontophrynus sp. had a more generalist diet. Their most commonly consumed prey were Isopoda followed by Coleoptera and miscellaneous larvae. Snout-vent length (SVL) was greater for juvenile Odontophrynus sp. than for juvenile R. arenarum, but the latter consumed more prey. The results suggest that juveniles of R. arenarum tend to specialize more on ants than do juveniles of Odontophrynus sp.

Life History Traits of the Stygophilous Amphipod Synurella ambulans in the Hyporheic Zone of the Lower Reaches of the Upper Sava River (Croatia)

Estimating the growth and population dynamics of crustaceans is important for understanding the role of species in ecosystems and for conservation and monitoring purposes. This study investigated temporal and spatial variation in population dynamics (growth rate, instantaneous mortality rates, and longevity) of the stygophilous freshwater amphipod Synurella ambulans (F. Müller, 1846), and influencing environmental factors. Seasonal sampling was conducted from December 2018 to October 2019 at two sampling sites (Jarun and Medsave) along the Sava River in northwestern Croatia. A Bhattacharya cohort analysis was applied to the length-frequency data using the FISAT software package. At least four cohorts were distinguished during the year. The possible influence of environmental factors on growth parameters was investigated using Canonical Correspondence Analysis (CCA), which revealed that the important environmental factors influencing S. ambulans abundance were water temperature and dissolved oxygen concentration. The average total body length (TBL) of females was 4.25 mm, while the TBL of males was 3.34 mm. The asymptotic length (L∞) and growth coefficient (K) were estimated to be 6.30 mm and 0.92 year−1 for females and 5.40 mm and 0.59 year−1 for males, respectively, at the Jarun site. L∞ and K were estimated to be 7.20 mm and 0.34 year−1, respectively, for females and 4.00 mm and 1.20 year−1, respectively, for males at the Medsave site. Estimated total mortality (Z) for each sex had higher values for males than females at both sampling sites. The lack of ecological knowledge on S. ambulans populations and relationships with invertebrate communities in the hyporheic zone of the large river ecosystems emphasises the importance of a detailed study for protecting this species and its vulnerable ecotonal groundwater-connected environment.

Population dynamics and secondary production of a key benthic tanaidacean, Monokalliapseudes schubarti (Mañé-Garzón, 1949) (Tanaidacea, Kalliapseudidae), from a tropical coastal lagoon in southeastern Brazil

Estimates of population dynamics and secondary production are important to understand the role of species in ecosystems and the mechanisms that drive life-history trade-offs, contributing to system preservation and monitoring. Population dynamics (growth rate, instantaneous mortality rates and longevity) and secondary production (biomass, production and P/B ratio) of the key marine benthic species Monokalliapseudes schubarti (Mañé-Garzón, 1949) were investigated monthly in a tropical coastal lagoon over 18 months and compared with data from other subtropical and temperate populations. A growth curve was estimated by fitting the Von Bertalanffy growth model. M. schubarti showed latitudinal variation in growth parameters. In tropical areas, M. schubarti generated consecutive cohorts and the growth curve parameters were: , , . A smaller asymptotic length was found for tropical and subtropical areas compared with data from temperate areas, and a lower growth rate was found at the tropical site. The annual mortality rate for the finite population was 0.999 year−1. Longevity, estimated at 10 months, was lower at the tropical site. The secondary production rate of M. schubarti at the tropical coastal lagoon was 10.60 g AFDW m−2 year−1, with a P/B ratio = 5.44. Brief longevity, a high P/B ratio, and high mortality may indicate M. schubarti as an opportunistic species in tropical areas.

The ecosystem: research and practice in North America

Abstract. Since the early 1940s, the ecosystem approach has been developed in a variety of forms by North American ecologists. Lindeman established its foundation, with his focus on functional components and energy transfers between trophic levels; this view was developed further by several ecologists, including G. Evelyn Hutchinson, and H. T. and E. P. Odum. Ecosystem ecology eventually became closely associated with powerful American institutions, such as the Atomic Energy Commission, receiving ample support; in association with the International Biological Program it became known as "big ecology''. More recently, ecosystem ecology has exhibited strengthened interest in spatial patterns, the role of species in ecosystems, and global change. This history has encompassed various ontological, methodological, ethical and political claims regarding the place of this approach in the discipline of ecology and in environmental governance.

Collapse of a Marine Mammal Species Driven by Human Impacts

Understanding historical roles of species in ecosystems can be crucial for assessing long term human impacts on environments, providing context for management or restoration objectives, and making conservation evaluations of species status. In most cases limited historical abundance data impedes quantitative investigations, but harvested species may have long-term data accessible from hunting records. Here we make use of annual hunting records for Caspian seals (Pusa caspica) dating back to the mid-19th century, and current census data from aerial surveys, to reconstruct historical abundance using a hind-casting model. We estimate the minimum numbers of seals in 1867 to have been 1–1.6 million, but the population declined by at least 90% to around 100,000 individuals by 2005, primarily due to unsustainable hunting throughout the 20th century. This collapse is part of a broader picture of catastrophic ecological change in the Caspian over the 20th Century. Our results combined with fisheries data show that the current biomass of top predators in the Caspian is much reduced compared to historical conditions. The potential for the Caspian and other similar perturbed ecosystems to sustain natural resources of much greater biological and economic value than at present depends on the extent to which a number of anthropogenic impacts can be harnessed.

The value of nature

According to many accounts we are in the midst of a major extinction crisis, one that is unrivaled in extent and pace in evolutionary history. Despite enormous energy and expenditure devoted to conservation, we will be unable to save all imperiled species and places. How can (or even should) we come up with a prioritization approach that helps us make decisions about what is worth saving? One of the most widely promoted schemes is monetary valuation of species and ecosystems, based on the goods and services that we as humans receive. These ecosystem services can be delivered directly (eg food, fiber, or beauty) or indirectly (eg water filtration, carbon capture). While some have advocated monetary valuation as a democratic process in deciding which species or places to conserve (Nunes and van den Berg 2001; Ecol Econ 39: 203–22), others consider this a “selling out” of nature (McCauley 2006; Nature 447: 27–28). The important question is, can the economic model of anthropocentric valuing of species, ecosystems, and their goods and services deliver conservation benefits as promised? I propose a performance-based assessment using successes and failures over the past several decades, when the economic model has reigned supreme. Although space limitations prevent a detailed accounting here, I choose two crude metrics: protecting species and protecting ecosystems. Evidence suggests that we are doing rather poorly on the first, given accelerating species loss. Conversely, using protected areas, we have done better, by currently placing 12% of the global terrestrial surface area under some level of protection, with a goal of 20% by 2020. However, this growth in protected areas essentially “locks up” these places in conservation and out of the “normal” marketplace, so their applicability to assess performance of monetary evaluation is questionable. Furthermore, setting areas aside for conservation alone may not result in desired conservation benefits – we can't squeeze all of Earth's terrestrial biota into 10% or even 20% of the available area. Moreover, many protected areas are largely rock and ice (that is, not the most productive habitats) and global change will require many species to relocate. While I'm unable to judge whether – in the absence of the economic conservation model – biodiversity would have fared even worse, the status quo can't be one of comfort and promise for the future. I believe that any economic valuation of species or ecosystems will clash with long-term conservation goals. The most formidable obstacle is that managing species and ecosystems based on their utility to humans requires accurate measurements of the services that are provided and a thorough accounting of all costs and benefits. This raises serious questions about the ecological knowledge required to make such decisions. The economic value we assign to species will shift based on available information about the functional roles of species in ecosystems or food webs. For instance, we now recognize the role of top predators as structuring forces in terrestrial and aquatic environments, yet we do not assign them appropriate economic value. Non-lethal diseases and many parasites are now increasingly appreciated for their beneficial effects, for example in priming our immune systems. Any conservation approaches built on market-based evaluations rooted in past or incomplete ecological knowledge could result in extinction of species we undervalued previously. Furthermore, it is unclear how costs and benefits are being apportioned (locally, regionally, nationally, or globally). This raises serious questions about issues of accounting, governance, and enforcement, as well as the length of time economic models need to cover to account for cumulative or long-term effects. Finally, assigning trust and power to unregulated, market-based institutions to manage conservation interests implies that theoretical foundations, institutional structures, and their governance are sound and can be relied upon. The recent global financial crises indicate the opposite, because short-term profit maximizations overrode long-term stewardship responsibilities. While humans will clearly continue to be the beneficiaries of ecosystem services, the only hope for long-term conservation is to increase societal support. This requires a redefinition (in non-market terms) of our relationships with the natural world (including other people). In fact, this may provide the only means to assure the survival of many species and biotic communities for which we (currently) have no use or value. I agree with Aldo Leopold in that I have no hope for recruiting future generations of conservation-minded individuals by appealing to their pocketbooks. Instead, we should strive to reach their hearts. A nation does not buy conservation but learns it.

Ecosystem engineering in space and time

The ecosystem engineering concept focuses on how organisms physically change the abiotic environment and how this feeds back to the biota. While the concept was formally introduced a little more than 10 years ago, the underpinning of the concept can be traced back to more than a century to the early work of Darwin. The formal application of the idea is yielding new insights into the role of species in ecosystems and many other areas of basic and applied ecology. Here we focus on how temporal, spatial and organizational scales usefully inform the roles played by ecosystem engineers and their incorporation into broader ecological contexts. Two particular, distinguishing features of ecosystem engineers are that they affect the physical space in which other species live and their direct effects can last longer than the lifetime of the organism--engineering can in essence outlive the engineer. Together, these factors identify critical considerations that need to be included in models, experimental and observational work. The ecosystem engineering concept holds particular promise in the area of ecological applications, where influence over abiotic variables and their consequent effects on biotic communities may facilitate ecological restoration and counterbalance anthropogenic influences.

RELATIVE EFFECTS OF SPECIES COMPOSITION AND RICHNESS ON ECOSYSTEM PROPERTIES IN PONDS

Biological diversity is complex and can be described and quantified in various ways. Research exploring the consequences of biodiversity for ecosystem functioning has generally focused on the effects of four components of biodiversity: species richness and composition, and functional group richness and composition. Most of the research to date has focused on biodiversity effects within single trophic levels. The aim of this study was to compare the relative effects of these four components of biological diversity across pond food webs using aquatic mesocosm experiments in which all four community properties were manipulated independently. Functional groups were defined in terms of trophic groups, and consisted of aquatic macrophytes, periphyton grazers, and invertebrate predators. Species composition and species richness were manipulated within functional groups. Ecosystem response variables included the final biomass of the manipulated taxa (macrophytes, grazers, and predators), ecosystem rates (productivity and decomposition), and trophic structure (phytoplankton and periphyton biomass). Results reveal strong effects of species composition on a significant proportion of ecosystem response variables. In contrast, species richness, functional group richness, and functional group composition altered the biomass of the manipulated taxa, but had no additional effects on other ecosystem variables. Results suggest that the roles of species in ecosystems, when considered in a food web context, are often the result of both direct and indirect effects that are difficult to predict based on the association of a species to a particular functional group. If a goal of biodiversity research is to predict the response of ecosystems to biodiversity loss, effects of composition and species losses across food webs must be fully integrated into biodiversity–ecosystem functioning research.

Characterizing ecosystem‐level consequences of biological invasions: the role of ecosystem engineers

Invasions by exotic species represent both threats to ecosystems as well as opportunities to learn more about them. Among the invaders that will have the largest impacts are those that directly modify ecosystems and thus have cascading effects for resident biota. Exotics can affect ecosystems by altering system‐level flows, availability, or quality of nutrients, food, and physical resources (e.g. living space, water, heat or light). The invader‐mediated control of physical resources, typically achieved through the modification of habitats, has received limited attention in invasion biology. This reflects a general trend in ecology, and only recently has the concept of ecosystem engineering been developed to account for the role of species that shape habitats. Plants and animals in terrestrial and aquatic systems can both create and destroy structure. When introduced into ecosystems, these exotic engineers cause physical state changes with effects that ramify throughout the system. Although the consequences of these modifications are varied and complex, insight gained from general ecological principles offers an opportunity to predict what invaders will do upon their integration into systems. Examples from the literature suggest that introduced ecosystem engineers that increase habitat complexity or heterogeneity tend to cause abundances and/or species richness to rise, while those that decrease complexity tend to have the reverse effect. In assessing such patterns, however, it is critical to also consider spatial scales and the life habits of resident organisms. In addition to providing predictive power, recognition of engineering as a major means by which invasive species affect ecosystems provides a unifying theme for invasion biology and offers a chance to consider more fully the general role of species in ecosystems.

Ecological sustainability and biodiversity

SUMMARY The immense complexity of ecosystems severely hampers the underpinning of the ecological sustainability paradigm. The few existing definitions of ecological sustainability, such as ecosystem health, are based on the obsolete superorganism paradigm of ecosystems, assuming an equilibrium for every ecosystem. New, anthropocentric approaches, like the ecosystem integrity concept, surmise that ecosystems are dynamic, loosely defined assemblages of species, which necessitates adaptive management. Another complicating factor is our poor understanding of the complex relation between biodiversity and ecosystem functioning. The few hypotheses about the role of species in ecosystems, like the rivet popper and the functional redundancy hypotheses, are not universally applicable. The functional importance of an individual species is unpredictable and context-dependent, even for keystone species. Biodiversity buffers changes in environmental conditions and might be considered as a kind of insurance.

The Role of Species in Ecosystems

The Role of Species in Ecosystems

What Do Species Do in Ecosystems?

Three aspects of the role of species in ecosystems are reviewed. (1) Theoretically, what are the possible relationships between ecosystem processes (Likens' (1992) transformation and flux of energy and matter) and the species richness of communities ? (2) Summaries of two experiments with artificially constructed terrestrial ecosystems in the controlled environment facility known as the Ecotron are described. The first draws attention to the role of earthworms as ecosystem engineers; the second explores changes in ecosystem processes in mesocosms assembled with three different levels of biological diversity