Species-poor Systems Research Articles

Resource partitioning of a Mexican clam in species-poor Baltic Sea sediments indicates the existence of a vacant trophic niche

Invasive species are often generalists that can take advantage of formerly unexploited resources. The existence of such vacant niches is more likely in species-poor systems like the Baltic Sea. The suspension feeding wedge clam, Rangia cuneata, native to estuarine environments in the Gulf of Mexico, was sighted for the first time in the southeastern Baltic in 2010 and a few years later in the northern Baltic along the Swedish coast. To explore possible competition for food resources between R. cuneata and the three native clams inhabiting Baltic shallow soft bottoms, stable isotope and fatty acid analyses were conducted. There was no overlap between R. cuneata and any of the native species in either stable isotope or fatty acid niches. This suggests efficient partitioning of resources; multivariate analyses indicate that separation was driven mainly by δ13C and by fatty acids reflecting diatoms and cyanobacteria, respectively (e.g. 16:1ω7 and 18:3ω3). R. cuneata reflected seasonal variation in phytoplankton more than other clams reflecting higher trophic plasticity. In conclusion, the addition of R. cuneata to the Baltic shallow soft bottoms suggests the existence of a vacant trophic niche in these sediment habitats, however the long-term effects on other species and nutrient cycling requires further studies focusing on the population dynamics of R. cuneata and its impact on the Baltic Sea ecosystem.

Experimental Effects of a Lightweight Mussel Dredge on Benthic Fauna in a Eutrophic MPA

Dredging for wild mussels Mytilus edulis Linnaeus, 1758 takes place in the marine protected areas (Natura 2000 sites) in Denmark. The fishery is strictly regulated to limit the impact of dredging to the benthic environment, and requires the use of modified lightweight mussel dredges. Nevertheless, the depletion of the benthic macrofauna associated with M. edulis beds after impact from such dredges is yet to be quantified. Here, dredging is shown to result in a significant decline in the density, species richness, and biological traits directly in the dredge track but no significant impact on the community composition. Species richness remained significantly affected 4 mo post dredging, although the positive trend after 4 mo may signal recovery. An effect of dredging was also detected in areas adjacent (approximately 5 m) to the dredge tracks, but needs further investigation to understand this impact. The results provide an estimate of benthic macrofaunal depletion in the dredge track as well as of the short-term recovery, which may be of use in the management of the fishery. Finally, it is suggested that species richness may be a more sensitive indicator than density in a eutrophic and species-poor system.

Restoring tropical forest composition is more difficult, but recovering tree-cover is faster, when neighbouring forests are young

Neighbouring forests constitute biological sources that enable the succession from species-poor systems, such as tree-plantings, to highly diverse forests. However, old forest patches are becoming rare in tropical agricultural landscapes. We were interested in if, and how, spontaneous regeneration under tree-plantings reflects the age and the amount of the neighbouring forest cover. We anticipated that older forests promote a compositionally broader recovery in neighbouring tree-plantings, because older forests likely include disturbance-sensitive species, particularly within least deforested landscapes. We studied twenty-seven restoration sites implemented as tree-plantings in the Brazilian Atlantic Forest. We quantified the effects of age and amount of neighbouring forest cover on structural and compositional characteristics of the regeneration community (dbh < 5 cm). We used two landscape groups (presence, or absence, of forests older than 30 years.) with a similar areal range of forest cover, enabling the disentanglement of forest age from forest amount effects on regeneration community responses. Surprisingly, we found that greater forest cover correlated with denser and more species-rich regeneration communities only when neighbouring forests were young. This pattern was promoted by non-vertebrate dispersed species. Regeneration communities in tree-plantings near to young forests had lower seed-mass and relative abundances of forest-specialists, compared to communities found near old forest patches. Regeneration is likely denser in landscapes of vast young-forest coverage. However, small-seeded and habitat-generalist species, frequently related to disturbance tolerance, tend to be dominant if old-growth forests are far away. This biased seed source appears to preclude the restoration of typical historic tropical forest composition.

Predator-prey body size relationships of cod in a low-diversity marine system

How predators select their prey largely defines ecosystem trophic structure, function and dynamics. In aquatic systems, organism body size is an important trait explaining predator− prey interactions. Here, we used a unique Atlantic cod Gadus morhua stomach content dataset with diet information from over 100 000 individuals collected from the Baltic Sea in 1963−2014, to explore prey size distribution and predator−prey mass ratios in the diet of Eastern Baltic cod. Maximum and average prey sizes increased with predator size, as for cod in other systems. However, the prey size spectra found in Eastern Baltic cod stomachs reflect the low species diversity in the Baltic Sea. In general, Eastern Baltic cod feed on smaller prey in relation to their body size than other cod populations. Due to the truncated prey size distribution in the Baltic Sea, cod cannibalism functions as a compensatory mechanism that allows Baltic cod to reach their prey size potential. On the other hand, small- and intermediate-sized cod prey mainly on a few invertebrate prey species, potentially making them vulnerable to changes in these prey populations. Our results encourage further studies disentangling the relative effects of prey preference and prey availability on cod trophodynamics in species-poor systems such as the Baltic Sea.

Vertical transmission of sponge microbiota is inconsistent and unfaithful.

Co-evolutionary theory predicts that if beneficial microbial symbionts improve host fitness, they should be faithfully transmitted to offspring. More recently, the hologenome theory of evolution predicts resemblance between parent and offspring microbiomes and high partner fidelity between host species and their vertically transmitted microbes. Here, we test these ideas in multiple coexisting host species with highly diverse microbiota, leveraging known parent-offspring pairs sampled from eight species of wild marine sponges (Porifera). We found that the processes governing vertical transmission were both neutral and selective. A neutral model was a better fit to larval (R2 = 0.66) than to the adult microbiota (R2 = 0.27), suggesting that the importance of non-neutral processes increases as the sponge host matures. Microbes that are enriched above neutral expectations in adults were disproportionately transferred to offspring. Patterns of vertical transmission were, however, incomplete: larval sponges shared, on average, 44.8% of microbes with their parents, which was not higher than the fraction they shared with nearby non-parental adults. Vertical transmission was also inconsistent across siblings, as larval sponges from the same parent shared only 17% of microbes. Finally, we found no evidence that vertically transmitted microbes are faithful to a single sponge host species. Surprisingly, larvae were as likely to share vertically transmitted microbes with larvae from other sponge species as they were with their own species. Our study demonstrates that common predictions of vertical transmission that stem from species-poor systems are not necessarily true when scaling up to diverse and complex microbiomes.

Calculating Competitive Intransitivity: Computational Challenges.

Intransitive (or "rock-paper-scissors") competition is compelling because it promotes species coexistence and because recent work suggests that it may be common in natural systems. One class of intransitivity indices works by considering s, the minimum number of competitive reversals to convert a given competitive community (i.e., a "tournament") to a hierarchy. The most straightforward example of such "reversal-based" indices is Petraitis's index, [Formula: see text], where M is the maximum s across all possible n-species tournaments. Using exhaustive searches, we prove that Petraitis's formula for M (and, therefore, t) does not hold for [Formula: see text]. Furthermore, determination of s for even moderate values of n may prove difficult, as the equivalent graph theoretical problem is NP (nondeterministic polynomial time) hard; there is no known computationally feasible way to compute an exact answer for anything but small values of n, let alone a closed-form solution. Petraitis's t is a valuable index of intransitivity; however, at present its use is limited to relatively species-poor systems. More broadly, reversal-based indices, while intuitive, may be problematic because of this computability issue.

Functional diversity measures revealed impacts of non-native species and habitat degradation on species-poor freshwater fish assemblages

Trait-based ecology has been developed for decades to infer ecosystem responses to stressors based on the functional structure of communities, yet its value in species-poor systems is largely unknown. Here, we used an extensive dataset in a Spanish region highly prone to non-native fish invasions (15 catchments, N=389 sites) to assess for the first time how species-poor communities respond to large-scale environmental gradients using a taxonomic and functional trait-based approach in riverine fish. We examined total species richness and three functional trait-based indices available when many sites have ≤3 species (specialization, FSpe; originality, FOri and entropy, FEnt). We assessed the responses of these taxonomic and functional indices along gradients of altitude, water pollution, physical habitat degradation and non-native fish biomass. Whilst species richness was relatively sensitive to spatial effects, functional diversity indices were responsive across natural and anthropogenic gradients. All four diversity measures declined with altitude but this decline was modulated by physical habitat degradation (richness, FSpe and FEnt) and the non-native:total fish biomass ratio (FSpe and FOri) in ways that varied between indices. Furthermore, FSpe and FOri were significantly correlated with Total Nitrogen. Non-native fish were a major component of the taxonomic and functional structure of fish communities, raising concerns about potential misdiagnosis between invaded and environmentally-degraded river reaches. Such misdiagnosis was evident in a regional fish index widely used in official monitoring programs. We recommend the application of FSpe and FOri to extensive datasets from monitoring programs in order to generate valuable cross-system information about the impacts of non-native species and habitat degradation, even in species-poor systems. Scoring non-native species apart from habitat degradation in the indices used to determine ecosystem health is essential to develop better management strategies.

Biotic homogenization: Loss of avian functional richness and habitat specialists in disturbed Andean temperate forests

Habitat loss and degradation have the potential to alter the species richness–functional diversity relationship decreasing both species richness and functional richness, and increasing functional biotic homogenization. These anthropogenic disturbances may have strong impacts on species-poor systems with low functional redundancy. We tested the species richness–functional diversity relationship and the potential effects of deforestation and degradation on functional diversity of avian assemblages in a Biodiversity Hotspot, in southern Chile. For 101 sites established across a disturbance gradient, we conducted 505 point-transect surveys to measure avian community structure, 505 vegetation plots to quantify stand-level structure, and measured deforestation at the landscape-level. We used three functional diversity indices for avian assemblages (functional richness, functional evenness, and community-weighted specialization as a measure of functional biotic homogenization). We found a non-saturating relationship between species richness and both functional richness and community-weighted specialization, suggesting low functional redundancy. We also found a non-significant decline of functional evenness indicating that when adding new species to the initial pool, functional redundancy increases slightly. Deforestation led to a decrease in both functional richness and community-weighted specialization, particularly precluding the persistence of specialized species in disturbed forests. Functional evenness did not vary with deforestation suggesting that the regularity of density distribution in filled niche volume may be relatively resilient to disturbance. However, the fact that community-weighted specialization decreased linearly under deforestation serves as evidence of functional biotic homogenization processes (“loser” specialists being replaced by “winner” generalist species) in a Biodiversity Hotspot.

Do deposit-feeders compete? Isotopic niche analysis of an invasion in a species-poor system.

Successful establishment of invasive species is often related to the existence of vacant niches. Competition occurs when invaders use the same limiting resources as members of the recipient community, which will be reflected in some overlap of their trophic niches. The concept of isotopic niche has been used to study trophic niche partitioning among species. Here, we present a two-year field study comparing isotopic niches of the deposit-feeding community in a naturally species-poor system. The isotopic niche analyses showed no overlap between a recent polychaete invader and any of the native species suggesting that it has occupied a vacant niche. Its narrow isotopic niche suggests specialized feeding, however, the high δ15N values compared to natives are most likely due to isotope fractionation effects related to nitrogen recycling and a mismatch between biological stoichiometry of the polychaete and the sediment nitrogen content. Notably, highly overlapping isotopic niches were inferred for the native species, which is surprising in a food-limited system. Therefore, our results demonstrate that invaders may broaden the community trophic diversity and enhance resource utilization, but also raise questions about the congruence between trophic and isotopic niche concepts and call for careful examination of assumptions underlying isotopic niche interpretation.

Positive Plant Diversity-Soil Stability Relationships are Mediated through Roots in the Songnen Grassland: Chronosequence Evidence

Living plant diversity (excluding the litter issue) may affect below-ground properties and processes, which is critical to obtaining an integrated biodiversity-ecosystem functioning theory. However, related patterns and underlying mechanisms have rarely been examined, especially lacking long-term evidence. We conducted a factorial crossed sample survey to examine the effects of plant diversity on soil stability over succession based on space-for-time substitution in the Songnen Steppes, North-Eastern China. The results indicate that, under natural colonizing conditions, species-poor systems achieved lower soil stability than species-rich systems, regardless of successional stage. However, soil stability was significantly regulated by plant species richness (number), composition (identity), density (abundance), and functional roles. Our results confirm that a long-term positive plant diversity-soil stability relationship exists in steppe succession. In particular, this enhanced effect of biodiversity on soil stability may operate via diversifying plant root traits. Our results may underpin an integrated biodiversity-ecosystem functioning theory, and improve human use and conservation management of natural resources at an integrated ecosystem level.

Specificity and temporal dynamics of complex bacteria–sponge symbiotic interactions

Microbes are known to form intricate and intimate relationships with most animal and plant taxa. Microbe--host symbiotic associations are poorly explored in comparison with other species interaction networks. The current paradigm on symbiosis research stems from species-poor systems where pairwise and reciprocally specialized interactions between a single microbe and a single host that coevolve are the norm. These symbioses involving just a few species are fascinating in their own right, but more diverse and complex host-associated microbial communities are increasingly found, with new emerging questions that require new paradigms and approaches. Here we adopt an intermediate complexity approach to study the specificity, phylogenetic community structure, and temporal variability of the subset of the most abundant bacteria associated with different sponge host species with diverse eco-evolutionary characteristics. We do so by using a monthly resolved annual temporal series of host-associated and free-living bacteria. Bacteria are very abundant and diverse within marine sponges, and these symbiotic interactions are hypothesized to have a very ancient origin. We show that host-bacteria reciprocal specialization depends on the temporal scale and level of taxonomic aggregation considered. Sponge hosts with similar eco-evolutionary characteristics (e.g., volume of tissue corresponding to microbes, water filtering rates, and microbial transmission type) have similar bacterial phylogenetic community structure when looking at interactions aggregated over time. In general, sponge hosts hypothesized to form more intricate relationships with bacteria show a remarkably persistent bacterial community over time. Other hosts, however, show a large turnover similar to that observed for free-living bacterioplankton. Our study highlights the importance of exploring temporal variability in host--microbe interaction networks if we aim to determine how specific and persistent these poorly explored but extremely common interactions are.

Complex wasp-waist regulation of pelagic ecosystems in the Pacific Ocean

‘Wasp-waist’ control of marine ecosystems is driven by a combination of top-down and bottom-up forcing by a few abundant short-lived species occupying intermediate trophic levels that form a narrow ‘waist’ through which energy flow from low to high trophic levels is controlled. It has been assumed that wasp-waist control occurs primarily in highly productive and species-poor systems (e.g. upwelling regions). Two large, species-rich, pelagic ecosystems in the relatively oligotrophic eastern and western Pacific Ocean also show wasp-waist-like structure, in that short-lived and fast-growing cephalopods and fishes at intermediate trophic levels comprise the vast majority of the biomass. Possible forcing dynamics of these systems were examined using ecosystem models by altering the biomass of phytoplankton (bottom-up forcing), large pelagic predators (top-down forcing), and intermediate ‘wasp-waist’ functional groups independently and observing how these changes propagated throughout the ecosystem. The largest effects were seen when altering the biomass of mid trophic-level epipelagic and mesopelagic fishes, where dramatic trophic cascades occurred both upward and downward in the system. We conclude that the high productivity and standing biomass of animals at intermediate trophic levels has a strong top-down influence on the abundance of primary producers. Furthermore, their importance as prey for large predators results in bottom-up controls on populations at higher trophic levels. We show that these tropical pelagic ecosystems possess a complex structure whereby several waist groups and alternate trophic pathways from primary producers to apex predators can cause unpredictable effects when the biomasses of particular functional groups are altered. Such models highlight the possible structuring mechanisms in pelagic systems, which have implications for fisheries that exploit these wasp-waist groups, such as squid fisheries, as well as for fisheries of top predators such as tunas and billfishes that prey upon wasp-waist species.

Forest Biodiversity and the Delivery of Ecosystem Goods and Services: Translating Science into Policy

Biodiversity is integral to almost all ecosystem processes, with some species playing key functional roles that are essential for maintaining the value of ecosystems to humans. However, many ecosystem services remain nonvalued, and decisionmakers rarely consider biodiversity in policy development, in part because the relationships between biodiversity and the provision of ecosystem services are not generally appreciated. To date, the majority of work in which the functional importance of biodiversity has been examined has been conducted in relatively species-poor systems. Focusing on forest and agroforest systems, we synthesize recent research on the role of biodiversity in the provision of ecosystem services and provide examples of biodiversity science that informs ecosystem management and policy. Finally, we highlight barriers to the transfer of knowledge from scientists to decisionmakers and suggest that scientists can be much more effective at informing policy and improving resource management by asking policy-relevant questions and providing timely and consistent information to decisionmakers and the public on the linkages among biodiversity, ecosystem services, and their value to people.

Belowground DNA-based techniques: untangling the network of plant root interactions

Plant roots are a central driver of ecosystem productivity, as plant investments belowground often comprise more than half of total plant biomass (Jackson et al. 1996). Despite this general observation, almost nothing is known about the distribution of roots in ecosystems; generally because roots of different species are morphologically indistinguishable, restricting species identification. This is in strict contrast to plant identification aboveground, which is straightforward after initial taxonomic training. Although in species poor systems containing roots of two species morphological identification has been possible in a few cases (Genney et al. 2002; Janecek et al. 2004; Mommer et al. 2011), disentangling and identifying roots from species-rich systems is impossible. To overcome problems of species identification, pioneering DNA-based techniques have been applied to plant roots (Jackson et al. 1999; Linder et al. 2000) and are now being used in experimental and observational studies of species-rich plant communities (e.g. Mommer et al. 2010; Kesanakurti et al. 2011; Dumbrell et al. 2011). In this paper, we discuss the current state of molecular techniques for plant species identification and quantification from mixed root samples. We focus on crucial aspects in the methodology regarding primer choice, DNA extraction and PCR inhibition, showing the potential caveats and their solutions. Finally we briefly discuss a few questions in the field of root ecology that will be advanced significantly by the appropriate use of these molecular tools.

Habitat loss and possible effects on local species richness in a species-poor system: a case study of southern Baltic Sea macrofauna

The effects of habitat loss on local species richness depend on the characteristics of the endangered system (including its total species pool and the distribution of species among the habitats). The present study focuses on the species-poor southern Baltic marine benthic biota. Macrobenthic samples were collected in three habitats: (1) soft bottom covered with vegetation; (2) stony reefs; (3) unvegetated sands. Fourty one percent of 54 observed macrozoobenthic species were habitat specific, while 30% occurred in all three habitats. There were no significant differences in total species richness among the three habitats. The accumulation curves plotted for subsets of data with selected habitats excluded lay below the curve plotted for the whole dataset, but only in one case the 95% confidence intervals of the subset curve did not overlap with those plotted for the whole dataset. The exclusion of samples from selected habitats produced a species richness drop ranging from 9 to 13%. The present study showed that habitat loss in a species-poor area with a relatively large ratio of generalist species cannot produce local species richness declines similar to those predicted for diverse marine systems. However, it must be emphasized that in species-poor systems, the loss of ecological function accompanying habitat loss could be disproportionally higher than that predicted based on decreases in species richness, as some functions are performed by a single species.

Assessing the ecological status in species-poor systems: A fish-based index for Mediterranean Rivers (Guadiana River, SW Spain)

The assessment of the ecological status of freshwater ecosystems is a key issue for many international laws such as the Water Framework Directive (WFD) in light of the actual impoverished status of these ecosystems. Different multimetric approaches have been successfully developed in different freshwater environments. However, multimetric indices are difficult to apply to Mediterranean rivers basins, characterized by freshwater fish communities very low in species richness and support a high number of endemics with generalist and opportunistic life strategies. Here we follow a site-specific approach to develop an adaptation of the multimetric procedure usually used in Indices of Biotic Integrity (IBI), resulting in the Index of Community Integrity (ICI). We modeled the presence–absence of 10 native freshwater fish species from the Guadiana River basin using the Assessment of Nearest Neighbor Analyses (ANNA) model, to assess the deviation of the observed and expected community composition at reference condition. ANNA, which is a multi-species model, allowed incorporating in the index some rare species, though not all of them present in the basin. Deviations were transformed into probabilities of belonging to a reference site and species by species measures were then integrated in a final score. The use of presence–absence only data reduces potential errors associated with estimations of species’ abundance and its seasonal changes, which is especially important in Mediterranean environments. The ICI was sensitive to both habitat degradation and the degree of dominance of non-native species within the freshwater fish community (or biotic perturbation), which have been traditionally overlooked in IBIs, but was unresponsive to natural sources of variation. Given the site-specific nature and the simplicity of the index that we propose here, we expect it to be applicable to other Mediterranean basins for which predictive models can be produced.

Asymmetries in specialization in ant–plant mutualistic networks

Mutualistic networks involving plants and their pollinators or frugivores have been shown recently to exhibit a particular asymmetrical organization of interactions among species called nestedness: a core of reciprocal generalists accompanied by specialist species that interact almost exclusively with generalists. This structure contrasts with compartmentalized assemblage structures that have been verified in antagonistic food webs. Here we evaluated whether nestedness is a property of another type of mutualism-the interactions between ants and extrafloral nectary-bearing plants--and whether species richness may lead to differences in degree of nestedness among biological communities. We investigated network structure in four communities in Mexico. Nested patterns in ant-plant networks were very similar to those previously reported for pollination and frugivore systems, indicating that this form of asymmetry in specialization is a common feature of mutualisms between free-living species, but not always present in species-poor systems. Other ecological factors also appeared to contribute to the nested asymmetry in specialization, because some assemblages showed more extreme asymmetry than others even when species richness was held constant. Our results support a promising approach for the development of multispecies coevolutionary theory, leading to the idea that specialization may coevolve in different but simple ways in antagonistic and mutualistic assemblages.

Tornado damage of Quercus stellata and Quercus marilandica in the Cross Timbers, Oklahoma, USA

Questions: The Cross Timbers are a mosaic of savannas, grasslands and upland forests, occupying a significant portion of south-central North America. Our questions here were (1) how does a severe tornado affect the two most dominant tree species of the area Quercus marilandica and Q. stellata with respect to damage and mortality; (2) how do such patterns vary as a function of tree size? What are the implications of disturbance for codominance in species-poor systems? Location: The Cross Timbers in Oklahoma, USA. Methods: We established a 14.48-ha permanent plot following a severe tornado in 2003. We identified, numbered and tagged each tree and recorded its diameter at breast height (DBH), spatial coordinates, status (dead or alive), and damage type. We examined (1) relative abundance before and after the tornado; (2) differences in damage and mortality, and (3) the influence of tree diameter on the probability of damage and mortality for each species. Results: Differences in species identity and tree characteristics were significantly related to tree mortality following the tornado, after accounting for spatial locations. The odds of mortality were 12.0 times greater for Q. marilandica than for Q. stellata. Such greater vulnerability of Q. marilandica versus Q. stellata was also reflected in changes in density and basal area. Tree diameter clearly influenced the damage and mortality pattern in Q. stellata; larger trees sustained more damage and mortality. However, Q. marilandica did not exhibit size-dependent mortality. Conclusion: The tornado affected the two dominant species differently. The intra- and inter-specific differences in windstorm susceptibility may allow coexistence of the two species and are potentially important in the dynamics of the Cross Timbers. Species more damaged might finally benefit from the wind disturbance due to their resprouting ability.

Diversity-dependent production can decrease the stability of ecosystem functioning.

There is concern that species loss may adversely affect ecosystem functioning and stability. But although there is evidence that biodiversity loss can lead to reductions in biomass production, there is no direct evidence that biodiversity loss affects ecosystem resistance (ability to withstand perturbation) or resilience (recovery from perturbation). Yet theory, laboratory experiments and indirect experimental evidence strongly suggest that diversity and stability are related. Here we report results from a field experiment with factorially crossed perturbation and diversity manipulations. We simulated drought perturbation on constructed grassland ecosystems containing 1, 2, 4, 8 or 32 plant species. Under unperturbed conditions, the species-poor systems achieved lower biomass production than the species-rich systems. However, the species-poor systems were more resistant to perturbation than the species-rich systems. The species-poor systems also showed a larger initial resilience following perturbation, although the original relationship between diversity and productivity was fully restored after 1year. Our results confirm that biodiversity increases biomass production, but they also point to the fact that such diversity--production associations may lead to an inverse relationship between biodiversity and the stability of ecosystem functioning.

Linking Ecological Sustainability and World Food Needs

Ecological approaches to agriculture can provide useful guidelines for addressing world food needs, while avoiding adverse environmental and social impacts. Experiments in both natural and agricultural ecosystems suggest that systems with high plant diversity may be more productive, more stable and more resilient than species-poor systems. In addition, systems with high plant diversity support higher levels of biodiversity in other functional groups, which may enhance the productivity of the plant component. Given these benefits of diverse systems, various approaches for converting conventional high input agricultural systems to more sustainable systems are addressed. Andow and Hidaka's (1989) concept of production syndromes is considered in the context of conversion to sustainable agriculture.