Outcome Of Competitive Interactions Research Articles

Competitive interactions affect larval survival of two root-boring weed biological control candidates of Rumex spp

In weed biocontrol, the release of multiple candidates has been proposed as a way to increase herbivore load and thus impact on the target weed. However, the use of multiple herbivorous species may reduce overall herbivore load due to interspecific interactions. We assessed whether a combined application of two Pyropteron spp. (Lepidoptera: Sesiidae) with root-boring larvae can increase larval infestation rate and impact on two Rumex weeds (Caryophyllales: Polygonaceae). In a laboratory assay (‘behavioural experiment’), interference competition was assessed by comparing the survival of a single larva (no competition), of four conspecific larvae (intraspecific competition) and of two larvae of each species (interspecific competition). In a common garden study (‘infestation and impact experiment’), the outcomes of competitive interactions were assessed on potted plants with single and mixed species applications of the two Pyropteron species using a replacement design. In the behavioural experiment, larval survival was similarly reduced under intra- and interspecific competition compared to no competition, suggesting strong interference competition among larvae independent of the Pyropteron species. In the infestation and impact experiment, mixed application did only scarcely increase herbivore load. Increased herbivore load was found to increase root decay when applied in an inundative approach by placing eggs directly on Rumex plants. However, a joint application of two Pyropteron species did not increase the impact. We propose that detailed behavioural and impact studies be conducted to assess the likely outcome of using multiple candidates in biocontrol programs to minimize associated risks with multiple species introductions.

Cell size as driver and sentinel of phytoplankton community structure and functioning

AbstractBody size is a decisive functional trait in many organisms, especially for phytoplankton, which span several orders of magnitude in cell volume. Therefore, the analysis of size as a functional trait driving species’ performance has received wide attention in aquatic ecology, amended in recent decades by studies documenting changes in phytoplankton size in response to abiotic or biotic factors in the environment.We performed a systematic literature review to provide an overarching, partially quantitative synthesis of cell size as a driver and sentinel of phytoplankton ecology. We found consistent and significant allometric relationships between cell sizes and the functional performance of phytoplankton species (cellular rates of carbon fixation, respiration and exudation as well as resource affinities, uptake and content). Size scaling became weaker, absent or even negative when addressing C‐ or volume‐specific rates or growth. C‐specific photosynthesis and population growth rate peaked at intermediate cell sizes around 100 µm3.Additionally, we found a rich literature on sizes changing in response to warming, nutrients and pollutants. Whereas small cells tended to dominate under oligotrophic and warm conditions, there are a few notable exceptions, which indicates that other environmental or biotic constraints alter this general trend. Grazing seems a likely explanation, which we reviewed to understand both how size affects edibility and how size structure changes in response to grazing. Cell size also predisposes the strength and outcome of competitive interactions between algal species. Finally, we address size in a community context, where size‐abundance scaling describes community composition and thereby the biodiversity in phytoplankton assemblages.We conclude that (a) size is a highly predictive trait for phytoplankton metabolism at the cellular scale, with less strong and nonlinear implications for growth and specific metabolism and (b) size structure is a highly suitable sentinel of phytoplankton responses to changing environments.A freePlain Language Summarycan be found within the Supporting Information of this article.

Metabolic phenotype mediates the outcome of competitive interactions in a response-surface field experiment.

Competition and metabolism should be linked. Intraspecific variation in metabolic rates and, hence, resource demands covary with competitive ability. The effects of metabolism on conspecific interactions, however, have mostly been studied under laboratory conditions. We used a trait‐specific response‐surface design to test for the effects of metabolism on pairwise interactions of the marine colonial invertebrate, Bugula neritina in the field. Specifically, we compared the performance (survival, growth, and reproduction) of focal individuals, both in the presence and absence of a neighbor colony, both of which had their metabolic phenotype characterized. Survival of focal colonies depended on the metabolic phenotype of the neighboring individual, and on the combination of both the focal and neighbor colony metabolic phenotypes that were present. Surprisingly, we found pervasive effects of neighbor metabolic phenotypes on focal colony growth and reproduction, although the sign and strength of these effects showed strong microenvironmental variability. Overall, we find that the metabolic phenotype changes the strength of competitive interactions, but these effects are highly contingent on local conditions. We suggest future studies explore how variation in metabolic rate affects organisms beyond the focal organism alone, particularly under field conditions.

Reconstructing lost ecosystems: A risk analysis framework for planning multispecies reintroductions under severe uncertainty

Abstract Reintroduction projects, which are an important tool in threatened species conservation, are becoming more complex, often involving the translocation of multiple species. Ecological theory predicts that the sequence and timing of reintroductions will play an important role in their success or failure. Following the removal of sheep, goats and feral cats, the Western Australian government is sequentially reintroducing 13 native fauna species to restore the globally important natural and cultural values of Dirk Hartog Island (DHI). We use ensembles of ecosystem models to compare 23 alternative reintroduction strategies on DHI, in Western Australia. The reintroduction strategies differ in the order, timing and location of releases on the island. Expert elicitation informed the model structure, allowing for use of different presumed species interaction networks which explicitly incorporated uncertainty in ecosystem dynamics. Our model ensembles predict that almost all of the species (~12.5 of 13, on average) will successfully establish in the ecosystem studied, regardless of which reintroduction strategy is undertaken. The project can therefore proceed with greater confidence and flexibility regarding the reintroduction strategy. However, the identity of the at‐risk species varies between strategies, and depends on the structure of the species interaction network, which is quite uncertain. The model ensembles also offer insights into why some species fail to establish on DHI, predicting that most unsuccessful reintroductions will be the result of competitive interactions with extant species. Synthesis and applications. Our model ensembles allow for the comparison of outcomes between reintroduction strategies and between different species interaction networks. This framework allows for inclusion of high uncertainty in dynamics. Finally, an ensemble modelling approach also creates a foundation for formal adaptive management as reintroduction projects proceed.

The Significance of Genotypic Diversity in Coral Competitive Interaction: A Transcriptomic Perspective

Competitive interactions shape coral assemblages and govern the dynamics of coral ecosystems. Although competition is an ecological concept, the outcomes of competitive interactions are ultimately determined by patterns of gene expression. These patterns are subject to genotypic variation on both sides of any interaction. Such variation is typically treated as “noise”, but it is sometimes possible to identify patterns within it that reveal important hidden factors in an experiment. To incorporate genotypic variation into the investigation of coral competitive interactions, we used RNA-sequencing to study changes in gene expression in a hard coral (Porites cylindrica) resulting from non-contact competition experiment with a soft coral (Lobophytum pauciflorum). Hard coral genotype explained the largest proportion of variation between samples; however, it was also possible to detect gene expression changes in 76 transcripts resulting from interaction with the soft coral. In addition, we found a group of 20 short secreted proteins that were expressed as a coordinated unit in three interacting Porites-Lobophytum pairs. The presence of this secretion response was idiosyncratic in that it could not be predicted based on polyp behaviour, or the genotype of hard or soft coral alone. This study illustrates the significance of individual variation as a determinant of competitive behaviour, and also provides some intriguing glimpses into the molecular mechanisms employed by hard corals competing at a distance.

Early scrub development in De Westhoek coastal dunes (Belgium)

Coastal dunes in Northwestern Europe were subject to substantial scrub expansion during the past decades, a process often considered as a major problem for conservation management. This paper explores this process in De Westhoek nature reserve (Belgium), focussing on the three major constituents of the early scrub: Salix repens, Hippophae rhamnoides and Ligustrum vulgare. We study changes in dominance pattern between 1953 and 2010 based on vegetation maps and the demography of these species based on growth ring counting. We relate this data to the edaphic factors soil moisture and soil age. Early scrub development occurred in three phases: (1) rapid, mainly secondary scrub expansion after release of grazing pressure, (2) a main shift in relative abundance of the three main species, and (3) further succession into tall scrub and woodland along with local scrub decay. Edaphic factors play a major role in vegetation dynamics, but their relative importance diminishes along with landscape ageing. Simultaneously, the outcome of competitive interaction between scrub species, in which population demography plays a key role, gains importance. Primary and secondary scrub development seem to converge in terms of dominance patterns of S. repens, H. rhamnoides and L. vulgare. Spontaneous decay of mainly L. vulgare offers an opportunity for dune managers for the restoration of herbaceous dune vegetation with high conservation value.

Winners have higher pre-copulatory mating success but losers have better post-copulatory outcomes.

In many animals, the outcomes of competitive interactions can have lasting effects that influence an individual's reproductive success and have important consequences for the strength and direction of evolution via sexual selection. In the fruit fly, Drosophila melanogaster, males that have won previous contests are more likely to win in subsequent conflicts and losers are more likely to lose (winner-loser effects), but the direct fitness consequences and genetic underpinnings of this plasticity are poorly understood. Here, we tested how male genotype and the outcomes of previous male-male conflicts influence male pre- and post-copulatory success. We quantified pre-copulatory success in a choice and no-choice context, and post-copulatory success by quantifying ejaculate offensive and defensive ability. We found that winners have higher reproductive success compared to losers in both pre-copulatory scenarios. However, losers consistently mated for a longer duration, boosted female fecundity and had an increased paternity share when they were the first males to mate, suggesting increased investment into post-copulatory mechanisms. Finally, by using clonal hybrids from the Drosophila Genetic Reference Panel, we documented that genetic variation explained a sizeable proportion of the observed differences between lines, and of the interaction between line and winner and loser effects. Our results place the behavioural data on winner-loser effects in an evolutionary context by documenting the potential fitness gain to males from altering their reproductive strategy based on fighting experience. Our data may also explain the presence and maintenance of trade-offs between different male reproductive strategies.

Imperfect monitoring, cyclical, and learning model perspectives: Price war in the Indonesian lighting industry

In marketing terms, the phenomenon of price war is regarded as the result of over-competition and retaliatory reaction in order to win market share. Based on the available literature, three refined models of price war antecedents has been identified: the imperfect monitoring model, the cyclical model, and the learning model. This article was written as part of a recent empirical observation of four Indonesian lighting companies who consider themselves to be currently engaged in price war. Based on the proposition made earlier by Heil and Helsen (2001), this study was prepared as a qualitative survey using an open-ended questionnaire method. The study found that price war is a result of competitive interaction in periods where demands are declining and induced by intra-brand competition. In conclusion, propositions to manage activities in conditions of price war are presented.

Functional traits and environmental characteristics drive the degree of competitive intransitivity in European saltmarsh plant communities

Abstract Competitive intransitivity, the existence of loops in competitive hierarchies, is one mechanism that can promote the local coexistence of competitors and maintain high local species diversity, although its prevalence and importance remain largely unknown. A full understanding of local community assembly needs knowledge of how transitive and intransitive competitive interactions are linked to species functional traits and the strength of biotic and abiotic filters. We apply a recently developed statistical tool to quantitative data on central European inland saltmarsh plant communities to infer causal relationships between soil characteristics, species occurrences and functional traits, and we estimated coefficients of competition. We found a predominance of intransitive competitive hierarchies. The proportion of such hierarchies was positively correlated with local species richness and compositional variability. Average soil characteristics were not correlated with competitive intransitivity, whereas high soil pH and the high variability in local pH and soil salinity decreased the overall impact of competition on community composition. In pairwise comparisons of species, dissimilarity in morphology, resource demand and reproductive phenology was significantly negatively correlated with differences in competitive performance, while higher environmental dissimilarity was particularly linked to intermediate degrees of competitive superiority. Our results suggest that habitat filtering for similar traits might intensify competitive interactions, but might also give rise to intransitive competitive loops that subsequently promote species coexistence and permit species’ functional equivalence. Intransitive competition appears to increase local diversity and small scale‐species turnover. The observed local differences in competitive structures suggest frequent competitive plasticity and context‐dependent competitive interactions. Finally, our results support the view that local abundance distributions can be used to infer the strength and outcome of competitive interactions. Synthesis. Our results confirm that intransitive competitive interactions might be a strong force structuring local plant communities. Intransitivity needs to be considered when studying plant community assembly and species co‐existence.

Harvesting changes mating behaviour in European lobster.

Removing individuals from a wild population can affect the availability of prospective mates and the outcome of competitive interactions, with subsequent effects on mating patterns and sexual selection. Consequently, the rate of harvest‐induced evolution is predicted to be strongly dependent on the strength and dynamics of sexual selection, yet there is limited empirical knowledge on the interplay between selective harvesting and the mating systems of exploited species. In this study, we used genetic parentage assignment to compare mating patterns of the highly valued and overexploited European lobster (Homarus gammarus) in a designated lobster reserve and nearby fished area in southern Norway. In the area open to fishing, the fishery is regulated by a closed season, a minimum legal size and a ban on the harvest of egg‐bearing females. Due to the differences in size and sex‐specific fishing mortality between the two areas, males and females are of approximately equal average size in the fished area, whereas males tend to be larger in the reserve. Our results show that females would mate with males larger than their own body size, but the relative size difference was significantly larger in the reserve. Sexual selection acted positively on both body size and claw size in males in the reserve, while it was nonsignificant in fished areas. This strongly suggests that size truncation of males by fishing reduces the variability of traits that sexual selection acts upon. If fisheries continue to target large individuals (particularly males) with higher relative reproductive success, the weakening of sexual selection will likely accelerate fisheries‐induced evolution towards smaller body size.

Relatedness and body size influence territorial behaviour in Salmo salar juveniles in the wild

AbstractWild Atlantic salmon, Salmo salar L., juveniles defend territories to enable exclusive access to food resources, and kin selection benefits may be accrued where territorial boundaries of relatives overlap. This study explored space sharing events between pairs of sibling and non‐sibling fish as a measure of territoriality and resource competition in a small chalk stream using passive integrated transponder (PIT) technology. The time period between fish detections in a shared space was closer between pairs of siblings (sibling pairs mean = 60.48 ± 51.84 min; non‐sibling pairs mean = 348.8 ±65.94 min). These results suggest that the territorial boundaries of related fish often overlap, thus increasing the likelihood of siblings accruing kin selection benefits. The findings from this study also suggest that outcomes of competitive interactions among dominant and subordinate fish are less pronounced when fish are related.

Triclosan exposure results in alterations of thyroid hormone status and retarded early development and metamorphosis in Cyprinodon variegatus

Thyroid hormones are critically involved in somatic growth, development and metamorphosis of vertebrates. The structural similarity between thyroid hormones and triclosan, an antimicrobial compound widely employed in consumer personal care products, suggests triclosan can have adverse effects on the thyroid system. The sheepshead minnow, Cyprinodon variegatus, is now used in ecotoxicological studies that have recently begun to focus on potential disruption of the thyroid axis by endocrine disrupting compounds. Here, we investigate the in vivo effects of exposure to triclosan (20, 50, and 100μgL−1) on the thyroid system and the embryonic and larval development of C. variegatus. Triclosan exposure did not affect hatching success, but delayed hatching time by 6–13h compared to control embryos. Triclosan exposure affected the ontogenetic variations of whole body thyroid hormone concentrations during the larval phase. The T3 peak around 12–15 dph, described to be indicative for the metamorphosis climax in C. variegatus, was absent in triclosan-exposed larvae. Triclosan exposure did not produce any deformity or allometric repatterning, but a delayed development of 18–32h was observed. We conclude that the triclosan-induced disruption of the thyroid system delays in vivo the start of metamorphosis in our experimental model. We observed a global developmental delay of 24–45h, equivalent to 4–7% prolongation of the developmental time in C. variegatus. The costs of delayed metamorphosis can lead to reduction of juvenile fitness and could be a determining factor in the outcome of competitive interactions.

Trait values and not invasive status determine competitive outcomes between native and invasive species under varying soil nutrient availability

AbstractInvasion by exotic plants is often associated with nutrient enrichment of soils, particularly on soils of naturally low fertility. As a consequence, it is likely that the outcome of competitive interactions between native and invasive plants may be mediated by soil nutrient availability. We independently investigated competitive effect and response as well as the occurrence of asymmetric competition among native and invasive plants on soils of varying nutrient availability, using a glasshouse experiment. Seedlings of eight co‐occurring pairs of invasive and native species from low fertility Hawkesbury Sandstone‐derived soil were grown under low and high nutrient availability. We tested the hypotheses that native species would be competitively superior at low nutrient availability and have trait values associated with a resource conservation strategy while invasive species would be competitively superior at high nutrient availability and have trait values associated with a resource acquisition strategy. We found that nutrient availability did not mediate competitive interactions between invasive and native species. Instead, two invasive and one native species were always competitively superior irrespective of nutrient availability. Competitively superior species displayed a mixture of both resource conservation and acquisition strategies at low and high nutrient availability. In support of previous studies, we found that the a priori classification of invasive and native species does not predict competitive superiority at varying nutrient levels. Rather, species specific differences in trait values provide a competitive advantage in response to nutrient availability.

Influence of species, size and relative abundance on the outcomes of competitive interactions between brook trout and juvenile coho salmon

Resource competition between animals is influenced by a number of factors including the species, size and relative abundance of competing individuals. Stream-dwelling animals often experience variably available food resources, and some employ territorial behaviors to increase their access to food. We investigated the factors that affect dominance between resident, non-native brook trout and recolonizing juvenile coho salmon in the Elwha River, WA, USA, to see if brook trout are likely to disrupt coho salmon recolonization via interference competition. During dyadic laboratory feeding trials, we hypothesized that fish size, not species, would determine which individuals consumed the most food items, and that species would have no effect. We found that species, not size, played a significant role in dominance; coho salmon won 95% of trials, even when only 52% the length of their brook trout competitors. As the pairs of competing fish spent more time together during a trial sequence, coho salmon began to consume more food, and brook trout began to lose more, suggesting that the results of early trials influenced fish performance later. In group trials, we hypothesized that group composition and species would not influence fish foraging success. In single species groups, coho salmon consumed more than brook trout, but the ranges overlapped. Brook trout consumption remained constant through all treatments, but coho salmon consumed more food in treatments with fewer coho salmon, suggesting that coho salmon experienced more intra- than inter-specific competition and that brook trout do not pose a substantial challenge. Based on our results, we think it is unlikely that competition from brook trout will disrupt Elwha River recolonization by coho salmon.

Presence of competitors influences photosynthesis, but not growth, of the hard coral Porites cylindrica at elevated seawater CO2

Abstract Changes in environmental conditions, such as those caused by elevated carbon dioxide (CO2), potentially alter the outcome of competitive interactions between species. This study aimed to understand how elevated CO2 could influence competitive interactions between hard and soft corals, by investigating growth and photosynthetic activity of Porites cylindrica (a hard coral) under elevated CO2 and in the presence of another hard coral and two soft coral competitors. Corals were collected from reefs around Orpheus and Pelorus Islands on the Great Barrier Reef, Australia. They were then exposed to elevated pCO2 for 4 weeks with two CO2 treatments: intermediate (pCO2 648) and high (pCO2 1003) compared with a control (unmanipulated seawater) treatment (pCO2 358). Porites cylindrica growth did not vary among pCO2 treatments, regardless of the presence and type of competitors, nor was the growth of another hard coral species, Acropora cerealis, affected by pCO2 treatment. Photosynthetic rates of P. cylindrica were sensitive to variations in pCO2, and varied between the side of the fragment facing the competitors vs. the side facing away from the competitor. However, variation in photosynthetic rates depended on pCO2 treatment, competitor identity, and whether the photosynthetic yields were measured as maximum or effective photosynthetic yield. This study suggests that elevated CO2 may impair photosynthetic activity, but not growth, of a hard coral under competition and confirms the hypothesis that soft corals are generally resistant to elevated CO2. Overall, our results indicate that shifts in the species composition in coral communities as a result of elevated CO2 could be more strongly related to the individual tolerance of different species rather than a result of competitive interactions between species.

542 Multi Layered Columnar Epithelium (MLCE) Induced by Bile At the Squamo-Columnar Junction in Mice Originates From Squamous and Columnar Cells

Barrett's esophagus (BE), a premalignant condition of esophageal adenocarcinoma (EAC) is defined as the replacement of normal stratified squamous epithelium of the lower esophagus by metaplastic columnar epithelium (Spechler 2014). The observation of multi-layered columnar epithelium regularly observed at the squamo-columnar junction (SCJ) in BE patients suggests a transitional stage between these two types of epithelia. Studies, in both human and rats, have shown that especially the combination of acid and biles can induce multilayered columnar epithelium (MLCE) and metaplasia at the SCJ (Vaezi 1995, Chen 2008, Glickman 2009). In this study we investigated if the diverse layers as observed in MLCE is a transitional stage between epithelia originating from one progenitor cell, or is a mix of different types of epithelia with diverse progenitors. 0.5% deoxycholic acid (DCA) was given to mice in drinking water for a maximum of 30 weeks. Animals were sacrificed and studied by histology and immunohistochemistry (IHC) at different time points. The combination of bile and acid induced gland formation at the SCJ starting from week 10. The MLCE glands were positive in the outer layer for squamous markers K14, p63 and K5 and in the inner layer for columnar markers K19, TFF2 and Alcian Blue. In one of our previous studies we also observed Lgr5 positive cells (RNA in situ) in these multi-layered glands (Mari et al. 2014). To investigate if the multi-layered epithelium originates from a squamous or columnar stem cell, we performed lineage tracing experiments. A Cytokeratin 5 (K5)-cre (n=20) mouse specific for tracing squamous progenitor lineages, and a LeucineG-coupled receptor (Lgr5)-cre mouse (n=20) were crossed with Rosa-lacZ mice. Lineage tracing was induced by tamoxifen injection prior to bile treatment at the age of 8 weeks. Mice were sacrificed 15 weeks after induction. K5-lacZ positive cells were present in the outer layer of the gland demonstrating that the origin of these cells is from squamous progenitors, which is in concordance with the IHC results. Surprisingly, the columnar inner layer of the gland was devoid of K5and Lgr5-lacZ positive cells, suggesting that the origin cell for this layer is neither K5 or Lgr5. Negative K5 lineage tracing in columnar cells within the MLCE in mice excludes the transdifferentiation hypothesis in which squamous cells change into columnar cells, which has been a prevailing theory for many years. The negative lineage experiments for LGR5 suggests a columnar cell of origin, other than Lgr5 for the inner layer. Continuous acid and bile reflux changes the environment at the SCJ in mice and disrupts the natural homeostatic environment of squamous and columnar cells. It appears that MLCE is the result of competitive interactions between cell lineages driven by environmental changes.

Outcomes of competitive interactions after a natural increment of resources: the assemblage of aphid-tending ants in northern Patagonia

Fil: Lescano, Maria Natalia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Patagonia Norte. Instituto de Investigacion En Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; Argentina

Rapid parallel attentional target selection in single-color and multiple-color visual search.

Previous work has demonstrated that when targets are defined by a constant feature, attention can be directed rapidly and in parallel to sequentially presented target objects at different locations. We assessed how fast attention is allocated to multiple objects when this process cannot be controlled by a unique color-specific attentional template. N2pc components were measured as temporal markers of the attentional selection of 2 color-defined targets that were presented in rapid succession. Both targets either had the same color (one color task) or differed in color (two color task). Although there were small but systematic delays of target selection in the two color task relative to the one color task, attention was allocated extremely rapidly to both target objects in the two color task, which is inconsistent with the hypothesis that their selection was based on a slow switch between different color templates. Two follow-up experiments demonstrated that these delays did not reflect template switch costs, but were the result of competitive interactions between simultaneously active attentional templates. These results show that the control of focal attention during multiple-feature search operates much faster and more flexibly than is usually assumed.

Factors driving the biogeographic distribution of two temperate Australian damselfishes and ramifications for range shifts

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 484:189-202 (2013) - DOI: https://doi.org/10.3354/meps10300 Factors driving the biogeographic distribution of two temperate Australian damselfishes and ramifications for range shifts Ronen Galaiduk1,*, Will F. Figueira1,2, Michael J. Kingsford3, Belinda G. Curley2 1School of Biological Sciences, Marine Ecology Laboratories, A11, University of Sydney, New South Wales 2006, Australia 2Sydney Institute of Marine Science, Building 22, Chowder Bay Road, Mosman, New South Wales 2088, Australia 3School of Marine and Tropical Biology and ARC Centre of Excellence for Coral Reef Studies, James Cook University, Queensland 4811, Australia *Email: rgal2782@uni.sydney.edu.au ABSTRACT: The distribution and abundance of marine organisms is determined by interactions among numerous abiotic and biotic factors that operate across multiple spatial scales. This study focused on 2 endemic temperate damselfishes Parma microlepis and P. unifasciata, which have a similar ecology but only partially overlapping (~3° of latitude) biogeographical and depth ranges. The synergistic effects of temperature, competition and habitat use on patterns of abundance, distribution and growth were investigated using a combination of mensurative and manipulative field and laboratory experiments. Evidence suggests that the current ranges of both species are driven largely by latitudinal and depth variations in habitat types and not by thermal regimes. P. microlepis was shown to be a slower-growing, long-lived species (to 37 yr) that appears to be specialised in using urchin-grazed barrens. In contrast, P. unifasciata is a shorter-lived species (to 12 yr) and more of a habitat generalist. Where the ranges of these 2 species overlap, competitive interactions appear to drive patterns of habitat use, with P. microlepis potentially excluding P. unifasciata from urchin-grazed barrens habitat. Mesocosm laboratory experiments indicated that the outcome of competitive interactions between these 2 species is temperature-dependent, with P. microlepis dominance increasing at higher temperatures. This study clarifies the important role of habitat in determining latitudinal ranges of these 2 species. It also highlights the need to consider temperature-dependent behavioural interactions to properly understand future potential shifts in species ranges that may result from global climate change. KEY WORDS: Damselfishes · Parma microlepis · Parma unifasciata · Biological distribution · Range expansion · Global warming Full text in pdf format PreviousNextCite this article as: Galaiduk R, Figueira WF, Kingsford MJ, Curley BG (2013) Factors driving the biogeographic distribution of two temperate Australian damselfishes and ramifications for range shifts. Mar Ecol Prog Ser 484:189-202. https://doi.org/10.3354/meps10300 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 484. Online publication date: June 12, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

A functional comparative approach to facilitation and its context dependence

Summary Our ability to generalize about broad patterns and outcomes of competitive interactions among plants has improved from a better understanding of functional traits. Facilitative interactions among plants also exhibit strong trait‐based patterns; however, very little empirical research has addressed the trait basis of different facilitative mechanisms or the applicability of traditionally defined functional strategies to facilitation. We present a series of predictions regarding the trait basis of a variety of facilitative mechanisms based on empirical patterns of trait responses to environmental filters and knowledge of plant–environment feedbacks. Using a leaf‐height‐seed framework to predict plant responses to facilitative effects of neighbours, we identify two categories of facilitative mechanisms based on similar predicted responses of specific leaf area (SLA), height and seed size: (i) facilitation of low‐SLA, large‐seeded and tall plants in environments typified by periodically unfavourable conditions; and (ii) facilitation of high‐SLA, small‐seeded and tall plants in persistently severe environments. We suggest that facilitation related to herbivory will be idiosyncratic with respect to these functional traits. Competition for limiting resources is predicted to reinforce trait‐based responses to facilitation in periodically severe environments, particularly under light competition, but to offset facilitative effects to some degree in persistently severe environments. Thus, biotic interactions may have stronger consequences for shifts in trait distributions in environments typified by disturbance, pulsed soil moisture and short growing seasons limited by low temperatures. Facilitative effects, in addition to facilitative responses, may also be regulated by functional traits, but there is much less empirical evidence for links between functional traits and ameliorative effects on the environment. However, we predict that leaf area index or other integrative traits related to canopy density are likely to be important effect traits for most facilitative mechanisms and should be integrated into more trait‐screening programs. Based on the exceptional contribution that trait‐based approaches have made for understanding other interactions, we suggest that taking a functional comparative approach to facilitation is an opportunity to improve our ability to identify general patterns and consequences of positive interactions.