Enhanced UV-Reflection Facilitated a Shift in the Pollination System of the Red Poppy, Papaver rhoeas (Papaveraceae)

Evolutionary change is considered a major factor influencing the invasion of new habitats by plants. Yet, evidence on how such modifications promote range expansion remains rather limited. Here we investigated flower color modifications in the red poppy, Papaver rhoeas (Papaveraceae), as a result of its introduction into Central Europe and the impact of those modifications on its interactions with pollinators. We found that while flowers of Eastern Mediterranean poppies reflect exclusively in the red part of the spectrum, those of Central European poppies reflect both red and ultraviolet (UV) light. This change coincides with a shift from pollination by glaphyrid beetles (Glaphyridae) to bees. Glaphyrids have red-sensitive photoreceptors that are absent in bees, which therefore will not be attracted by colors of exclusively red-reflecting flowers. However, UV-reflecting flowers are easily detectable by bees, as revealed by visual modeling. In the North Mediterranean, flowers with low and high UV reflectance occur sympatrically. We hypothesize that Central European populations of P. rhoeas were initially polymorphic with respect to their flower color and that UV reflection drove a shift in the pollination system of P. rhoeas that facilitated its spread across Europe

Natural forests loss and tree plantations: large-scale tree cover loss differentiation in a threatened biodiversity hotspot

Distinguishing between natural forests from exotic tree plantations is essential to get an accurate picture of the world's state of forests. Most exotic tree plantations support lower levels of biodiversity and have less potential for ecosystem services supply than natural forests, and differencing them is still a challenge using standard tools. We use a novel approach in south-central of Chile to differentiate tree cover dynamics among natural forests and exotic tree plantations. Chile has one of the world's most competitive forestry industry and the region is a global biodiversity hotspot. Our collaborative visual interpretation method combined a global database of tree cover change, remote sensing from high-resolution satellite images and expert knowledge. By distinguishing exotic tree plantation and natural forest loss, we fit spatially explicit models to estimate tree-cover loss across 40 millions of ha between 2000 and 2016. We were able to distinguish natural forests from exotic tree plantations with an overall accuracy of 99% and predicted forest loss. Total tree cover loss was continuous over time, and the disaggregation revealed that 1 549 909 ha of tree plantations were lost (mean = 96 869 ha year(-1)), while 206 142 ha corresponded to natural forest loss (mean = 12 884 ha year(-1)). Mostly of tree plantations lost returned to be plantation (51%). Natural forests were converted mainly (75%) to transitional land covers (e.g. shrubland, bare land, grassland), and an important proportion of these may finish as tree plantation. This replacement may undermine objectives of increasedcarbon storage and biodiversity. Tree planting as a solution has gained increased attention in recen years with ambitious commitments to mitigate the effects of climate change. However, negative outcomes for the environment could result if strategies incentivize the replacement of natural forests into other land covers. Initiatives to reduce carbon emissions should encourage differentiating natural forests from exotic tree plantations and pay more attention on protecting and managing sustainably the former

Eigenschaften von Photorezeptoren, Grundlagen des Verhaltens und die Bedeutung für die Evolution der Angiospermen

In the present thesis I studied the spectral properties of photoreceptors as well as the behavioral bases of color vision in representative insect pollinators and evaluated this data in the context of the reproductive ecology and evolutionary biology of representative plant species. In the work presented in the first chapter I examined the visual mechanisms involved in the apparent ecological specialization of glaphyrid beetles to red flowers described for the South-East Mediterranean region. I characterized the photoreceptors spectral sensitivity of Pygopleurus israelitus (Glaphyridae: Scarabaeoidea: Coleoptera). In addition, using chromaticity diagrams to calculate the distribution of beetle-visited flower, I evaluated whether chromatic discrimination differs between P. israelitus and the honeybee. The measurements revealed the presence of three types of photoreceptors, maximally sensitive in the UV, green and red areas of the spectrum. The distribution of flower colors revealed a high level of correspondence between the receptor- based color vision of P. israelitus and the reddish flowers they encounter in nature and suggests differences in the coding of flower colors between P. israelitus and the honeybee. In the work presented in the second chapter I studied flower color evolution in Papaver rhoeas. According to Archeological and Taxonomic evidence this species was introduced into Central Europe from the Levant region about 5 thousand years ago. Intra-specific color differences were evaluated by comparing flower color composition of populations along its distribution range in Central Europe and the Levant region. The data revealed that populations of this species have diverged with respect to their flower color composition. While populations in Central Europe are compose exclusively by individuals having UV-reflecting flowers, populations in the Levant region seem to be composed almost exclusively by individuals having UV-absorbing flowers. In order to evaluate whether P. rhoeas has diverged with respect to its flower color appearance for its main insect pollinator groups, I compared the distribution of flower color loci in the chromaticity diagram of P. israelitus and the honeybee. The results of this evaluation indicates that P. rhoeas has diverged with respect to its flower color appearance for insect pollinators and suggest that the absence of UV-absorbing flowers in Central European populations would be congruent with the historical shift from beetle to bee pollination undergone by this species as it was introduced northwards into Europe. In the last chapter, I evaluated how differential learning affects color generalization in the honeybee. In particular, I evaluated how the position in the color space of a novel color relative to a positively reinforced color (CS+) and an unrewarded color (CS-) affects the occurrence of experience induced behavioral biases. My results revealed that when the novel color varied from CS- in the same way as CS+ but to a lower extent, subjects maintained their stronger response towards the former CS+. In contrast, when a novel color varied from CS- in the same way as CS+ but to a greater extent, subjects shifted their strongest response away from CS- towards the novel stimulus. These results revealed the occurrence of “peak shift” in the honeybee color vision and indicate that honeybees can learn color stimuli in relational terms based on their chromatic properties. The findings presented on this thesis are discussed in the context of the theoretical implications derived from the historical nature of plant pollinator interactions.In der vorliegenden Arbeit analysierte ich sowohl die spektralen Rezeptoreigenschaften wie auch die Verhaltensgrundlagen des Farbensehens repräsentativer Arten von bestäubenden Insekten. Diese Daten werden in den Kontext der Blütenökologie und Evolutionsbiologie repräsentativer Pflanzenarten gestellt. Im ersten Kapitel untersuchte ich die spektralen Rezeptoreigenschaften der Glaphyriden, einer Blumen besuchenden Käfergruppe, in Bezug auf rote Blumen in der südöstlichen Mittelmeerregion, die zu einer ökologischen Spezialisierung geführt haben. Ich verwende die spektrale Empfindlichkeit der Fotorezeptoren von Pygopleurus israelitus (Glaphyridae: Scarabaeoidea: Coleoptera) um mit Hilfe eines Farbesehmodells die Verteilung der Farborte in einem chromatischen Diagramm von Käfer-besuchten Blumen zu berechnen. Die Ergebnisse vergleiche ich mit entsprechenden Analysen an der Honigbiene. Meine Analysen weisen die Existenz von drei Fotorezeptoren mit spektralen Empfindlichkeitsmaxima im Ultraviolett, Grün und Rot nach. Die Verteilung der Blumenfarben im chromatischen Diagramm macht deutlich, dass Farbunterscheidung von P. iraelitus an rote Blumen mit und ohne UV Reflexion optimal angepasst ist und suggeriert außerdem, dass es Unterschiede in der Kodierung von Farben zwischen P. israelitus und der Honigbiene gibt. Im zweiten Kapitel untersuchte ich die Evolution der Blumenfarben von Papaver rhoeas. Laut archäologischer und taxonomischer Beweise kam diese Art vor ungefähr 5000 Jahren aus der levantischen Region nach Mitteleuropa. Ich wertete arttypische Farbunterschiede über den Vergleich von Farborten verschiedener Populationen in Mitteleuropa und in der levantischen Region aus. Meine Daten ergaben, dass sich Populationen dieser Art in ihren Farbmustern unterscheiden. Während die Populationen Mitteleuropas fast ausschließlich UV- reflektierende Blumen enthalten, haben die Populationen der levantischen Region vornehmlich UV-absorbierende Blumen. Um herauszufinden, ob sich das farbliche Erscheinungsbilder von P. rhoeas gegen über seinen Bestäubern verändert hat, verglich ich die Verteilung der Farborte im chromatischen Diagramm für diese Populationen für P. israelitus und die Honigbiene. Meine Ergebnisse stützen die Interprätation, dass sich das farbliche Erscheinungsbild von P. rhoeas verändert hat. Außerdem führen meine Ergebnisse zu der Annahme, dass das Fehlen von UV-absorbierenden Blumen in den Populationen in Mitteleuropa mit dem Wechsel von der Käfer- zur Bienenbestäubung zusammenhängt, die sich durch das Ausbreiten dieser Bestäuberart in den nördlichen Regionen ergab. Im letzten Kapitel untersuchten ich, wie sich das Erlernen von Farbmarken durch die Honigbiene auf die Generalisierung zwischen Farbmarken auswirkt. Dazu wurde auf einer belohnten Farbe (CS+) in Gegenwart einer nicht belohnten Farbe (CS-) dressiert und systematisch überprüft, wie sich dies auf die Unterscheidung von neuen Farbpaaren auswirkt. Meine Ergebnisse wiesen eine neuartige Leistung bei den Bienen nach, den sogenannten „Peak shifts“. Wenn die Testfarbe im chromatischen Diagramm näher am CS- war als der CS+, gaben die Versuchtiere immer der CS+ Farbe den Vorrang. Wenn allerdings die Testfarbe im chromatischen Diagramm weiter entfernt vom CS- war als der CS+, wählten die Bienen die Testfarbe. Diese Ergebnisse weisen nach, dass die Honigbiene aufgrund ihrer chromatischen Wahrnehmung Farbstimuli im direkten Vergleich unterscheiden können. Die Ergebnisse meiner Arbeit werden vor den Hintergrund der coevolutiven Entwicklung von Pflanzen und Bestäubern diskutiert

Mechanisms of flower coloring and eco-evolutionary implications of massive blooming events in the Atacama Desert

The Atacama Desert, one of the driest places on earth, holds a rich biodiversity that becomes most appreciable in years when unusual rainfall accumulation triggers a phenomenon of explosive development of ephemeral herbaceous and woody desert species known as “desierto florido” or “blooming desert.” Despite the scientific importance of this unique phenomenon only few studies have addressed the mechanisms of flower phenotypic divergence under the fluctuating environment provided by this recurrent event. We investigated the mechanisms of floral color diversity in Cistanthe longiscapa (Montiaceae), a dominant species across the ephemeral blooming landscape of Atacama Desert. Our analyses show that the variation in colors of C. longiscapa flowers result from petals containing betalain pigments with different absorption spectra. The different pigment composition of petals causes flower color differences in the visible and ultraviolet (UV) range of the spectrum. Through color vision models we show that C. longiscapa flowers are highly polymorphic in their color appearance for insect pollinators. Our results highlight the variable nature in flower color of C. longiscapa varieties blooming simultaneously in a geographical restricted area. Given the importance of color in attracting floral visitors, the observed color variability could contribute to increased cross pollination in extreme desert conditions, while accounting for complex and fluctuating histories of plant-pollinator interactions

Early Olfactory Environment Influences Social Behaviour in Adult Octodon degus

Artículo de publicación ISIWe evaluated the extent to which manipulation of early olfactory environment can influence social behaviours in the South American Hystricognath rodent Octodon degus. The early olfactory environment of newborn degus was manipulated by scenting all litter members with eucalyptol during the first month of life. The social behaviour of sexually mature animals (5-7 months old) towards conspecifics was then assessed using a y-maze to compare the response of control (naive) and treated animals to two different olfactory configurations (experiment 1): (i) a non-familiarized conspecific impregnated with eucalyptol (eucalyptol arm) presented against (ii) a non-familiarized unscented conspecific (control arm). In addition, in dyadic encounters, we assessed the behaviour of control and eucalyptol treated animals towards a non-familiarized conspecific scented with eucalyptol (experiment 2). We found that control subjects explored and spent significantly less time in the eucalyptol arm, indicating neophobic behaviours towards the artificially scented conspecific. Treated subjects explored and spent similar time in both arms of the maze, showing the same interest for both olfactory stimuli presented. During dyadic encounters in experiment 2, an interaction effect between early experience and sex was observed. Control males escaped and avoided their scented partnermore frequently than eucalyptol treatedmale subjects and than females. Both groups did not differ in the exploration of their scented partners, suggesting that avoidance within agonistic context does not relate to neophobic behaviours. Our results suggest that the exposure to eucalyptol during early ontogeny decreases evasive behaviours within an agonistic context as a result of olfactory learning. Altogether, these results indicate that olfactory cues learned in early ontogeny can influence olfactory-guided behaviours in adult degus.Comision Nacional de Investigacion Cientifica y Tecnologica de Chile CONICYT AT-2405018

Agonistic display during dyadic encounters between animals of the same sex.

<p>(A) Frequency of evasive behaviour (mean ± SE) depended on the sex and previous experience with the artificial odorant. Naïve males performed this kind of behaviours significantly more. (B) Aggressive behaviours (mean ± SE) were more frequent in males than in females. <i>H</i> and <i>p</i>-values from Scheirer-Ray-Hare test are shown in each figure.</p

Exploration time (mean ± SE) during dyadic interactions between individuals of the same sex.

<p>Males (in grey) explored significantly more the anogenital and anterior area of their partners (a non-familiarized conspecific impregnated with <i>eucalyptol</i>) than females (in black). Asterisks represent significant differences between males and females, Scheirer-Ray-Hare test (*<i>P</i> < 0.05 and **<i>P</i> < 0.01).</p

The <i>y-maze</i>.

<p>The system was designed to allow a focal <i>O. degus</i> to explore freely the three arms of the maze. Stimulus subjects were placed in chambers attached to the extremes opposite to the start chamber. A division plate prevented direct contact between focal and stimuli subjects, but allowed the airflow produced by a fan behind each stimulus chamber to circulate through the labyrinth.</p

Effects of early olfactory experience on <i>O. degus’</i> behaviours in the <i>y-maze</i>.

<p>(A) Exploration time (mean ± SE) of the <i>y-maze</i> arms by animals with different olfactory experience during early ontogeny (<i>eucalyptol</i> or naïve). Naïve subjects (controls) showed neophobia towards the artificial olfactory configuration (a conspecific impregnated with <i>eucalyptol</i>), exploring significantly less the <i>eucalyptol</i> arm (in black), subjects reared with <i>eucalyptol</i> (treated) explored similarly both arms. (B) Total time (mean ± SE) spent by both groups in each arm. Control subjects remain significantly more time in the control arm (in grey) and spent significantly less time in the <i>eucalyptol</i> arm than <i>eucalyptol</i> experienced subjects. Different letters represent statistically significant differences between the groups in each arm (<i>p</i> < 0.05, see text for exact statistical and <i>p</i> values).</p

Can red flowers be conspicuous to bees? Bombus dahlbomii and South American temperate forest flowers as a case in point

It has been argued that trichromatic bees with photoreceptor spectral sensitivity peaks in the ultraviolet (UV), blue and green areas of the spectrum are blind to long wavelengths (red to humans South American temperate forests (SATF) contain a large number of human red-looking flowers that are reported to be visited by the bumblebee Bombus dahlbomii.In the present study, B. dahlbomii's spectral sensitivity was measured through electroretinogram (ERG) recordings. No extended sensitivity to long wavelengths was found in B. dahlbomii. The spectral reflectance crves from eight plant species with red flowers were measured. The color loci occupied by these flowers in the bee color space was evaluated using the receptor noise-limited model. Four of the plant species have pure red flowers with low levels of chromatic contrast but high levels of negative L-receptor contrast. Finally, training experiments were performed in order to assess the role of achromatic cues in the detection and discri