Pollination and herbivory are both key drivers of plant diversity but are traditionally studied in isolation from each other. We investigated real-time evolutionary changes in plant traits over six generations by using fast-cycling Brassica rapa plants and manipulating the presence and absence of bumble bee pollinators and leaf herbivores. We found that plants under selection by bee pollinators evolved increased floral attractiveness, but this process was compromised by the presence of herbivores. Plants under selection from both bee pollinators and herbivores evolved higher degrees of self-compatibility and autonomous selfing, as well as reduced spatial separation of sexual organs (herkogamy). Overall, the evolution of most traits was affected by the interaction of bee pollination and herbivory, emphasizing the importance of the cross-talk between both types of interactions for plant evolution.

The evolution of monomorphisms from heterostylous ancestors has been related to the presence of homostyly and the loss of self-incompatibility, allowing the occurrence of selfing, which could be advantageous under pollinator limitation. However, flowers of some monomorphic species show herkogamy, attraction and rewarding traits that presumably favour cross-pollination and/or a mixed mating system. This study evaluated the contributions of pollinators, breeding system and floral traits to the reproduction of Turnera velutina, a herkogamous monomorphic species. Floral visitors and frequency of visits were recorded, controlled hand cross-pollinations were conducted under greenhouse and natural conditions, and individual variation in floral traits was characterised to determine their contribution to seed production. Apis mellifera was the most frequent floral visitor. Flowers presented approach herkogamy, high variation in nectar features, and a positive correlation of floral length with nectar volume and sugar concentration. Seed production did not differ between manual self- and cross-pollinations, controls or open cross-pollinations, but autonomous self-pollination produced, on average, 82.74% fewer seeds than the other forms, irrespective of the level of herkogamy. Differences in seed production among autonomous self-pollination and other treatments showed that T. velutina flowers depend on insect pollination for reproduction, and that approach herkogamy drastically reduced seed production in the absence of pollen vectors. The lack of differences in seed production from manual cross- and self-pollinations suggests the possible presence of a mixed mating system in the studied population. Overall, this species was possibly derived from a distylous ancestor but appears fully capable of outcrossing despite being monomorphic.

A biometric study of the flower, floral rewards (nectar and pollen) and pollen-ovule ratios in 14 taxa of Vicia (Fabaceae) from Extremadura (Spain) has been evaluated. Almost all floral characteristics are directly correlated and it has been found that flower size is a good indicator of the reward production, and the pollen-ovule ratios are positively correlated to seed size. A direct correlation between pollen size (volume) and style length has likewise been observed. This may show the importance of the pollen food reserves in sustaining the growth of its pollen tube along the style.

Theory predicts that herbivory should primarily determine the evolution of herbivore-induced plasticity in plant defenses, but little is known about the influence of other interactions such as pollination. Pollinators may exert negative selection on the herbivoreinduced plasticity of chemical defenses when floral signals and rewards are indirectly affected, provoking deterrent effects on these mutualists. We investigated the influence of constant herbivory and pollination on the evolved patterns and degree of herbivoreinduced plasticity in chemical plant defenses and floral morphometry and volatiles in fast-cycling Brassica rapa plants. To do this, we used plants from an evolution experiment that had evolved under bee/hand pollination and herbivory manipulated in a 2 × 2 factorial design during six generations, producing four selection treatments. We grew sibling plant pairs from each of the four selection treatments of the last generation and infested one group with herbivores and left the other uninfested. Herbivore-induced plasticity was analyzed within-and between-selection treatments. We found support for the hypothesis that constant herbivory favors the evolution of higher constitutive yet lower herbivore-induced plasticity in defenses. However, this only occurred in plants that evolved under hand pollination and constant herbivory. Bee pollination had a strong influence on the evolution of herbivoreinduced plasticity of all traits studied. Plants that evolved under bee pollination, with and without constant herbivory, showed remarkably similar patterns of herbivore-induced plasticity in their defense-and floral traits and had a higher number of plastic responses compared to plants with hand pollination. Such patterns support the hypothesis that bee pollination influenced the evolution of herbivore-induced plasticity, most likely via indirect effects, such as links between defense-and floral traits. We conclude that interactions other than herbivory, such as pollination, may impact herbivore-induced plasticity, through indirect effects and metabolic trade-offs, when it contributes to trait evolution in plants.

Despite the paramount role of floral fragrance in pollinator attraction and reproduction in flowering plants, we know little about its evolution under natural conditions. Here we show that by reducing herbivore load with pesticide application, plants showed evolutionary changes in their floral fragrance within 4 generations when compared to plants with natural levels of herbivory. We interpret this finding in the context of relaxed physiological and ecological trade-offs with fewer herbivores, potentially facilitating selection by bees on specific aromatic volatiles. Our study confirms earlier findings of experimental evolution under highly controlled and simplified conditions in the greenhouse.

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Background Stelis (Orchidaceae) encompasses approximately 1100 species of epiphytic orchids distributed throughout the Neotropics, with the highest diversity in Andean South America. Sixty-two species were recorded previously in Mexico.MethodsWe formally describe here Stelis zootrophionoides as a new species from Chiapas, Mexico. To determine its systematic position, we conducted a morphological comparison with other members of Pleurothallidinae and a phylogenetic analysis of nucleotide sequences from the plastid matK/trnK and trnL/trnF regions, as well as the nuclear ribosomal ITS region for 52 species of Pleurothallidinae. Sequences of 49 species were downloaded from GenBank and those of three species, including the new taxon, were newly generated for this work. The new species is described and illustrated; notes on its ecological preferences and a comparison with closely related species are presented.ConclusionsThe new species, known only from one location and apparently restricted to the cloud forest in the central highlands of Chiapas, Mexico, is considered a rare species. This small epiphyte is unique among the Mexican species of Stelis by the combination of dark purple flowers with the distal third of the dorsal sepal adhered to the apices of the lateral sepals, which are partially united into a bifid synsepal, leaving two lateral window-like openings, and sagittate labellum. Stelis jalapensis, known from southern Mexico and Guatemala, also has the apices of the sepals adhered to each other, but it is distinguished by its larger flowers with lanceolate, acute dorsal sepal, completely fused lateral sepals (i.e. the synsepal is not bifid), and oblong-elliptic labellum. The phylogenetic analysis shows that S. zootrophionoides is closely related to other Mexican Stelis and corroborates previous suggestions that fused sepal apices have arisen independently in different lineages of Pleurothallidinae.

Ecological interactions between plants and insects are of paramount importance for the maintenance of biodiversity and ecosystem functioning. Herbicides have long been considered a threat to plant and insect populations, but global increases in intensive agriculture and availability of herbicide-resistant crops have intensified concerns about their full impact on biodiversity. Here, we argue that exposure to sublethal herbicide doses has the potential to alter plant-insect interactions as a result of disruptions in their chemical communication. This is because herbicides interfere with biosynthetic pathways and phytohormones involved in the production of several classes of plant volatiles that mediate plant-insect chemical communication. Sublethal herbicide doses can modify the morphological and life-history plant traits and affect interactions with insects. However, the potential changes in plant volatiles and their consequences for plant-insect chemical communication have not yet received as much attention. We discuss how target-site (disruptors of primary metabolism) and non-target-site (synthetic auxins) herbicides could alter the production of plant volatiles and disrupt plant-insect chemical communication. We suggest research avenues to fill in the current gap in our knowledge that might derive recommendations and applied solutions to minimize herbicides' impacts on plant-insect interactions and biodiversity.