The importance of color : floral morphs, visit rates and fitness in the shrub Sarothamnus scoparius

El estudio de la variación intraespecífica del color de las flores nos permite comprender mejor el papel de los polinizadores como agentes de selección, y su efecto sobre la abundancia de las variantes florales. Estudiamos la influencia de la variación en los colores florales sobre la tasa de visita a las flores y la reproducción de Sarothamnus scoparius (retama), un arbusto exótico común en el NO de la Patagonia. En particular, determinamos si la mayor abundancia de arbustos con flores amarillas en relación a los arbustos con flores rojas o naranjas se debía a una tasa de visita diferencial por parte de sus potenciales polinizadores. Para eso, 1) medimos la tasa de visita a flores amarillas, rojas y naranjas en situaciones naturales y en plantas cuyo color de las flores fue manipulado; 2) determinamos si la tasa de visita a las flores rojas y naranjas dependía de su distancia al morfo floral más abundante (amarillo), y 3) estimamos la producción de frutos/flor y semillas/fruto en arbustos con flores amarillas y rojas. Encontramos que: 1) tanto en situaciones naturales como en flores cuyo color fue manipulado, las flores amarillas recibieron entre 1 y 4 veces más visitas que las otras variantes; 2) la tasa de visita a las flores rojas y naranjas decrecieron de manera abrupta a medida que aumentaba su distancia a las flores amarillas (7 veces en solo 100 cm), y 3) tanto la producción de frutos/flor como la de semillas/fruto fue ~40% mayor en los arbustos con flores amarillas comparado con aquellos de flores rojas. Estos resultados sugieren que la mayor abundancia de arbustos con flores amarillas se debe a que sus potenciales polinizadores prefieren este color, lo que se traduce en una reproducción mayor de esta variante floral. Este trabajo ilustra la importancia de los polinizadores como eventuales agentes selectivos de las características florales, así como la influencia del vecindario floral en dicho proceso.The study of the intraspecific variability in the flower color may help us to better understand the role of pollinators as selective agents end their effect on the local abundance of floral morphs. We studied the influence of intraspecific variation of flower color on the floral visitation rate and the fitness of Sarothamnus scoparius, a common exotic shrub in Northern Patagonia. Particularly, we determined whether the higher abundance of shrubs with yellow-flowers compared with those with red or orange flowers was consequence of a differential visitation rate of potential pollinators. We 1) measured the visitation rate to yellow flowers and their variants red and orange in natural conditions and in flowers where their color was manipulated; 2) determined whether the visitation rate to red and orange flowers depended on their distance to yellow flowers, and 3) estimated the production of fruit set and seed set in yellow and red flower morphs. We found that: 1) in both, nutural and color-modified conditions, yellow flowers received 1-4 times more visits than red or orange flowers; 2)the visitation rate to red and orange flowers decreased abruptly as the distance to yellow flowers increases (7 times in only 100 cm), and 3) both fruit and seed set were ~40% higher in shrubs with yellow flowers compared with those with red flowers. These results suggest that the higher abundance of shrubs with yellow flowers is consequence of a higher visitation rate of potential pollinators, which in turn produce a higher fitness in this floral morph. This work illustrates the importance of pollinators modeling flower characteristics and the influence of floral neighborhood in such process

Predation risk and floral rewards: How pollinators balance these conflicts and the consequences on plant fitness

Foraging behavior of pollinators is shaped by, among other factors, the conflict between maximizing resource intake and minimizing predation risk; yet, empirical studies quantifying variation in both forces are rare, compared to those investigating each separately. Here, we discuss the importance of simultaneously assessing bottom-up and top-down forces in the study of plant-pollinator interactions, and propose a conceptual and testable graphical hypothesis for pollinator foraging behavior and plant fitness outcomes as a function of varying floral rewards and predation risk. In low predation risk scenarios, no noticeable changes in pollinator foraging behavior are expected, with reward levels affecting only the activity threshold. However, as predation risk increases we propose that there is a decrease in foraging behavior, with a steeper decline as plants are more rewarding and profitable. Lastly, in high predation risk scenarios, we expect foraging to approach zero, regardless of floral rewards. Thus, we propose that pollinator foraging behavior follows an inverse S-shape curve, with more pronounced changes in foraging activity at intermediate levels of predation risk, especially in high reward systems. We present empirical evidence that is consistent with this hypothesis. In terms of the consequences for plant fitness, we propose that specialized plant-pollinator systems should be more vulnerable to increased predation risk, with a steeper and faster decline in plant fitness, compared with generalist systems, in which pollinator redundancy can delay or buffer the effect of predators. Moreover, whereas we expect that specialist systems follows a similar inverse S-shape curve, in generalist systems we propose three different scenarios as a function not only of reward level but also compatibility, mating-system, and the interplay between growth form and floral display. The incorporation of trade-offs in pollinator behavior balancing the conflicting demands between feeding and predation risk has a promising future as a key feature enabling the development of more complex foraging models

Patch-level facilitation fosters high-Andean plant diversity at regional scales

Aim: Local effects of ecosystem engineers on biodiversity can scale up to the landscape level, stressing the importance of ecological processes as determinants of species richness at larger spatial scales. In harsh environments, cushion plants often act as ecosystem engineers given their ability to buffer extreme abiotic conditions, thus providing unique and more favorable niches for the establishment of less stress-tolerant plant species. We assessed if facilitation by cushion plants influences patterns of plant diversity at increasing spatial scales. Location: Northern Patagonian Andes, Argentina. Methods: Based on plant species records within and outside cushions, we compared plant diversity in the presence and absence of cushions at the community, mountain and regional scale. Specifically, observed and estimated numbers of species occurring in either cushion plants or in the surrounding open areas were compared with the species numbers of the open areas. Results: The presence of cushion plants significantly increased species richness at all spatial levels analyzed. At the patch level, a higher number of species was recorded growing within cushion plants than in open area plots of similar size. Consistently, hypothetical communities lacking cushion plants showed significantly lower species richness than observed communities with cushion plants. These differences in species richness at patch and community scales increased with altitude, hence facilitation by cushion plants became more important at higher elevations. Moreover, according to asymptotic non-parametric estimators, cushion plants could increase overall regional species richness up to 40%. Conclusions: Our findings suggest that about one third of the high-Andean flora of the region owes its presence to the existence of nursing plants, defying the view that abiotic factors alone are enough to fully determine species occurrences at large spatial scales. This study provides evidence that local-scale ecological processes can be crucial in promoting and maintaining biodiversity at any spatial scale.Fil: Gavini, Sabrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Ezcurra, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Aizen, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentin

RecruitNet: A global database of plant recruitment networks

Plant recruitment interactions (i.e., what recruits under what) shape the composition, diversity, and structure of plant communities. Despite the huge body of knowledge on the mechanisms underlying recruitment interactions among species, we still know little about the structure of the recruitment networks emerging in ecological communities. Modeling and analyzing the community-level structure of plant recruitment interactions as a complex network can provide relevant information on ecological and evolutionary processes acting both at the species and ecosystem levels. We report a data set containing 143 plant recruitment networks in 23 countries across five continents, including temperate and tropical ecosystems. Each network identifies the species under which another species recruits. All networks report the number of recruits (i.e., individuals) per species. The data set includes >850,000 recruiting individuals involved in 118,411 paired interactions among 3318 vascular plant species across the globe. The cover of canopy species and open ground is also provided. Three sampling protocols were used: (1) The Recruitment Network (RN) protocol (106 networks) focuses on interactions among established plants ("canopy species") and plants in their early stages of recruitment ("recruit species"). A series of plots was delimited within a locality, and all the individuals recruiting and their canopy species were identified; (2) The paired Canopy-Open (pCO) protocol (26 networks) consists in locating a potential canopy plant and identifying recruiting individuals under the canopy and in a nearby open space of the same area; (3) The Georeferenced plot (GP) protocol (11 networks) consists in using information from georeferenced individual plants in large plots to infer canopy-recruit interactions. Some networks incorporate data for both herbs and woody species, whereas others focus exclusively on woody species. The location of each study site, geographical coordinates, country, locality, responsible author, sampling dates, sampling method, and life habits of both canopy and recruit species are provided. This database will allow researchers to test ecological, biogeographical, and evolutionary hypotheses related to plant recruitment interactions. There are no copyright restrictions on the data set; please cite this data paper when using these data in publications

RecruitNet: A global database of plant recruitment networks

Plant recruitment interactions (i.e., what recruits under what) shape the composition, diversity, and structure of plant communities. Despite the huge body of knowledge on the mechanisms underlying recruitment interactions among species, we still know little about the structure of the recruitment networks emerging in ecological communities. Modeling and analyzing the community-level structure of plant recruitment interactions as a complex network can provide relevant information on ecological and evolutionary processes acting both at the species and ecosystem levels. We report a data set containing 143 plant recruitment networks in 23 countries across five continents, including temperate and tropical ecosystems. Each network identifies the species under which another species recruits. All networks report the number of recruits (i.e., individuals) per species. The data set includes >850,000 recruiting individuals involved in 118,411 paired interactions among 3318 vascular plant species across the globe. The cover of canopy species and open ground is also provided. Three sampling protocols were used: (1) The Recruitment Network (RN) protocol (106 networks) focuses on interactions among established plants (“canopy species”) and plants in their early stages of recruitment (“recruit species”). A series of plots was delimited within a locality, and all the individuals recruiting and their canopy species were identified; (2) The paired Canopy-Open (pCO) protocol (26 networks) consists in locating a potential canopy plant and identifying recruiting individuals under the canopy and in a nearby open space of the same area; (3) The Georeferenced plot (GP) protocol (11 networks) consists in using information from georeferenced individual plants in large plots to infer canopy-recruit interactions. Some networks incorporate data for both herbs and woody species, whereas others focus exclusively on woody species. The location of each study site, geographical coordinates, country, locality, responsible author, sampling dates, sampling method, and life habits of both canopy and recruit species are provided. This database will allow researchers to test ecological, biogeographical, and evolutionary hypotheses related to plant recruitment interactions. There are no copyright restrictions on the data set; please cite this data paper when using these data in publications