Direct and indirect consequences of dominant plants in arid environments

This Figure belongs to the Synthesis chapter of Diego Sotomayor's PhD dissertation: "Direct and indirect consequences of dominant plants in arid environments". This dissertation was presented at the Department of Geography at York University.<br><br>The numbers in the Figure correspond to the dissertation chapters were each concept was covered:<br><br>1) Indirect interactions in terrestrial plant communities<br>2) Dominant plant effects across large spatial and temporal gradients<br>3) Dominant plant effects at micro-scales and within seasons<br>4) Plant-plant direct and indirect interactions by dominant plant canopies<br>5) Dominant plant effects on ecotypic differentiation<br><br>This is the abstract of the dissertation:<br> In arid environments, dominant woody plants such as shrubs or trees, usually facilitate a high density of species in their understories. This phenomemon is composed by a series of direct and indirect effects from the dominant plant to the understory species, and among understory species. The aim of this project was to determine these direct and indirect consequences of dominant plant-plant facilitation in a collection of field sites along the coastal Atacama Desert. The following objectives and hypotheses were examined in this project: (1) to summarize and contextualize the breadth of research on indirect interactions in terrestrial plant communities; (2) that the positive effects of dominant plants on understory communities are spatiotemporally scale dependent, from micro- to broad-scale spatial effects, and from within-seasonal to among-year temporal effects; (3) that dominant plants via their different traits determine the outcome of plant-plant interactions; (4) that dominant plants determine the outcome of interactions amongst understory species and that their responses are species-specific; and (5) that facilitation by dominant plants generates sufficiently different micro-environmental conditions that lead to consistent differences in seeds traits of understory plants. Overall, we found that multiple factors determine the outcome of plant-plant interactions along the field sites studied in this project. These factors impact both the direct and indirect effects of dominant woody plants on their understory communities and include species-specific traits of both the dominant and understory species, and the spatial and temporal environmental gradients that manifest their effects at different scales. Dominant plants usually facilitate increased species richness and density of plants in their understory, that in turn mediates effects amongst these species. However, these direct effects seem to have a limit given that at extremely stressful environmental conditions they tend to change to neutral and even competitive effects of canopies on their understories. This provides evidence that positive effects of dominant plants collapse under extreme spatiotemporal stress. Although we did not find evidence of evolutionary effects of top-down facilitation, the methodology proposed here represents a contribution to test the conditions under which these results hold. Overall, this project illustrates the importance of understanding the multiple drivers that determine the outcome of biotic interactions.  <br> <br

Indirect interactions in terrestrial plant communities: emerging patterns and research gaps Dataset

<p>This is the dataset from: Sotomayor DA and Lortie CJ. 2015. Indirect interactions in terrestrial plant communities: emerging patterns and research gaps. Ecosphere 6(6): art103. http://dx.doi.org/10.1890/ES14-00117.1<br>Methods<br>This dataset corresponds to a systematic review on inidirect interactions in terrestrial plant communities which captured the literature published between 1990 and July 2014 using the ISI Web of Science (WoS), Scopus, and Google Scholar. The following keywords were used: "indirect", "plant", "interaction", "competition", "facilitation". The first three words were used together in combination with the last two words in separate queries (i.e. indirect* plant* interaction* competition OR indirect* plant* interaction* facilitation).<br>The initial serach yielded 490 research articles obtained from the WoS, which were screened in order to assess their relevance. Searches in both Scopus and Google Scholar were conducted to complement the WoS search. The following inclusion criteria were used: (1) studies explicitly dealing with indirect interactions in terrestrial ecosystems (i.e. 3 or more species reported in the interaction); (2) studies describing the results of experiments specifically designed to test effects of indirect interactions versus proposals of indirect interactions in discussion; and (3) primary empirical research reported (i.e., not reviews). Papers complying with these criteria were processed to extract data on (1) type of interaction tested; (2) number of species tested as targets, where target is defined as the species on which measurements of performance were taken; (3) role of the species involved in the interaction considering not only target species, but also species that were removed or mentioned by the authors as members of the interaction; (4) type of experiment and number of field sites; (5) type of ecosystem and geographical location of the study; and (6) type of measurements and statistical analysis performed.</p> <p> </p

Evidence map of Indirect interactions in terrestrial plant communities: emerging patterns and research gaps

This is Figure 2 of Sotomayor and Lortie 2015 and can also be found here: http://www.esajournals.org/doi/abs/10.1890/ES14-00117.1<br><br>This Figure represents the geographical distribution of studies on indirect interactions involving terrestrial plants. <br><div><div><br></div></div> <br>ABSTRACT<br><div><div>Indirect interactions occur when the effect of one species on another is mediated by a third species. These interactions occur in most multi-species assemblages and are diverse in their mechanistic pathways. The interest in indirect interactions has increased exponentially over the past three decades, in recognition of their importance in determining plant community dynamics and promoting species coexistence. Here, we review the literature on indirect interactions among plants published since 1990, using a novel synthetic framework that accounts for and classifies intervening species and mechanisms within trophic networks. The objectives of this review are: (1) to identify the geographical regions and ecosystem types where indirect interactions have been examined; (2) to summarize the information on the number of trophic levels examined in studies of indirect interactions; (3) to test whether the frequency of indirect interactions varies across environmental gradients; and (4) to identify the experimental approaches most commonly used in studies of indirect interactions. Studies examining indirect interactions in plants have been conducted primarily in the Northern Hemisphere, with a focus on grasslands and forests. The majority of studies (67%) examined two trophic levels. Indirect facilitation and apparent competition are the interactions that have been most frequently examined, with the latter being reported more frequently in relatively productive environments. Other indirect interactions reported include associational resistance, exploitative competition or facilitation, shared defenses, and trophic cascades. Generally, field experiments tested indirect interactions based on single target species. While the majority of studies on indirect interactions dealt with basic ecology issues, several studies have dealt with such interactions in the context of biological invasions (18%) and rangeland management (12%). This review allowed us identifying a number of research needs, including the study of non-feeding interactions and that for more realistic complex designs, explicitly testing indirect interactions across different trophic levels, in geographical regions that have been under-examined to date, and in stressful ecosystems.<br></div></div><br

Dataset for the functional assessment of animals with plant facilitation complexes

<p>Review</p> <p>A set of systematic literature searches were done in October 2014 using Web of Science with the following search terms: “plant AND facilitat* AND shrub AND insect”, “plant AND facilitat* AND shrub AND animal”, “plant AND facilitat* AND shrub AND bird” and “plant AND facilitat* AND shrub AND mammal”. Search results were refined by the “ecology” category, and there were no biases associated with publication year, journal, or article type (cursory inspection of distribution across journals and time indicated even representation). The remaining articles were compiled into a single list, and duplicates were removed providing a total of 77 primary-research publications. We then processed each individual paper in full and excluded articles that were reviews, that did not include plant-plant facilitation estimates in some form, or that did not include quantitative documentation of an interacting animal.</p> <p>Findings</p> <p>Facilitation studies focus primarily on plants often neglecting the extended effects that spread through ecological networks. Plants interact with other organisms through consumptive effects and a myriad of non-trophic effects such as habitat amelioration or pollination. Shrubs are a dominant benefactor species in plant facilitation studies but can also have direct and indirect effects/interactions with animals. Herein, we use a systematic review to address the following two objectives: (1) to propose a conceptual framework that explores these effects taking into consideration the functional roles of the interacting species, and (2) to formally review the current state of this field examining effects beyond the widely explored plant-plant interactions. This synthesis was explicitly structured to ensure that basal shrub-plant facilitation was included in some form with an animal species, and consequently a relatively limited number of studies have to date examined the importance of these two sets of coupled interactions (77 studies in total). From this set of studies, 34 studies documented positive plant interactions generating a total of 47 independent instances of shrub-plant-animal or shrub-animal-plant interactions. These sets of interaction pathways were relatively evenly split between direct (54%) and indirect (46%) shrub interactions with animals. Hypotheses frequently tested included seed trapping, herbivore protection, magnet pollination effects, and facilitation-mediated secondary seed dispersal. The most common functional role of shrubs was herbivore protection, and the most common animal role associated with plant-facilitation complexes was that of a consumer. However, animals also frequently provided direct positive effects including secondary seed dispersal and pollination. The implications of nested complexes of shrub-plant facilitations are thus largely unexplored particularly in their capacity to scale to other taxa or trophic levels even from the relatively simple sets of interactions summarized in this review. None of these studies explored bidirectional plant-animal interactions, used a network approach to the study facilitation, nor contrasted interaction strengths. Nested and multi-trophically integrated sets of experiments incorporating plant facilitation into community dynamics are thus critical in advancing management of high-stress ecosystems.</p

A systematic review dataset describing the studies of positive interactions and the niche in deserts.

To synthesize the breadth of concepts and approaches used to concurrently study niche and positive plant interactions in deserts, we conducted a formalized systematic review. in early 2018, we conducted a search of the peer-reviewed literature using the Web of Science with the following terms: “niche“ AND (“plant facilitat*” OR “nurse plant” OR “positive interact*) AND (“arid” OR “desert”). After removing duplicates, the following data were extracted to categorize the studies. The code and full list of studies are provided on GitHub: https://cjlortie.github.io/desert.niche.facilitation

Species occurrence list for SDM of positive plant-interactions

Species distribution models we developed examining shrub-annual associations in the Mojave desert. Species within this study were separated into three classes. 1) facilitated - previously reported to be a beneficiary species, 2) unreported - unknown to have been a beneficiary species, 3) shrub - a previously reported benefactor species. These details were obtained from the scientific literature. The dataset contains the list of occurrences for the facilitated species, unreported species and  shrub-benefactor species. The occurrences were downloaded using GBIF

Dataset examining functional assessment of animals with plant facilitation complexes

<p>A systematic review examing plant facilitation by shrubs with other plant species and at least one animal species reported was done in 2014. A conceptual framework, review, and this dataset examined the capacity for positive plant interactions to scale to other taxa.</p

Conservación in situ en el Instituto Nacional de Innovación Agraria del Perú: avances y perspectivas (In situ conservation at the National Institute of Agricultural Innovation: progress and perspectives)

This poster was presented at the XI International Symposium of Genetic Resources for the Americas and the Caribbean, held at Guadalajara - Mexico, on October 15-18, 2017. This poster was presented in Spanish, but here you can find an Abstract in English. <br><br>In situ conservation takes place in the natural environment of the agrobiodiversity species and their wild relatives. This work synthesizes the in situ conservation efforts of the Subdirectorate of Genetic Resources (SDRG) of the National Institute of Agrarian Innovation in Peru. The SDRG has the legal mandate to lead in situ conservation actions at the national level, and develops related projects since the 1990s. Its activities have focused on: (1) conserving agrobiodiversity in farmer / breeder farms, with several projects implemented, highlighting the GEF Project "In situ conservation of native crops and their wild relatives", and the FAO Project "Reassessment and safeguarding of the ancestral knowledge for the management of Agroecosystems and Agrobiodiversity to generate the SIPAM site Andean Agriculture"; and (2) preparation of synthesis reports, policies and articulation with other sectors, highlighting the National Reports of the State of Genetic Resources, and the promulgation of the Supreme Decree on the Recognition of Agrobiodiversity Zones. These advances reinforce in situ conservation in Peru, but show the need to: (1) develop the National Agrobiodiversity Inventory to identify priority areas; (2) strengthen conservation in farmers / breeders' farms in partnership with regional and local governments; (3) implement the national system of Agrobiodiversity Zones; and (4) design studies on ecosystem services of agrobiodiversity and the processes and factors that influence its conservation in situ. The strengthening of these capacities will allow to support in the improvement of the quality of life of the conservationist farmers.<br

Germination of desert annuals to shrub facilitation is species specific but not ecotypic

<p>Aims Positive plant-interactions can promote higher species density of beneficiary species in deserts. However, there is limited evidence examining the trait sets of seeds from beneficiary species. In this study, we examined the hypothesis that shrubs (benefactors) influence the germination of desert annuals (beneficiaries) and promote ecotypic differentiation by generating distinct microsites through abiotic stress amelioration. The following predictions were tested using growth chamber and field-collected seeds: i) seed mass and viability will be greater and less variable for seeds collected from within shrub understory relative to seeds from open microsites, ii) germination of seeds from shrub and open microsites will be greatest under home (source) conditions, iii) seeds from the shrub will adaptively accelerate their germination rate when germinated in simulated home (source) microsites relative to their simulated away (reciprocal) microsite.</p> <p>Methods Seeds and their associated maternal plants were collected from four annual species found within a shrub understory (Larrea tridentata) and open microsites in the Mojave Desert of California (35.30ᵒ N, 117.26ᵒ W, 793 m.a.s.l.), and then reciprocally germinated in growth chambers simulating both microclimatic conditions. Cumulative germination and germination rate was measured every 4-5 days for 42 days.</p> <p>Important findings There was no significant difference in the mean or coefficient of variation for seed mass and viability between the shrub and open microsites. The source of the seeds did not significantly impact the cumulative germination and there was no accelerated rate of germination within species which suggests that ecotypic differentiation is not occurring. Cumulative germination was significantly higher within the shrub-simulated microhabitat for three out of the four species examined. Cumulative germination and germination rate was significantly different between species. These results support that shrubs influence the germination of desert annuals, and the outcome of this interaction is species specific, but shrub microsites do not alter the more conserved seed biology traits. Lack of gene flow, short dispersal distances, or source-sink dynamics can reduce trait differentiation and should be tested in future studies.</p