Jaime Martínez-Harms

Kin recognition refers to the discrimination and subsequent behavioral bias toward relatives and represents an important modulator of social interactions. Among relatives, reduced exploration, less aggressiveness, and lower inbreeding is typically expected. Two main mechanisms influence kin discrimination: prior association (based on familiarity) and phenotype matching (based on genetic relatedness). Here, we investigated kin discrimination between opposite-sex siblings in degus (Octodon degus), a highly social rodent endemic to central Chile. While in this species discrimination among same-sex siblings has been shown to be mainly influenced by rearing experience, it remains unknown whether degus can discriminate their opposite-sex siblings at all, and if so, what mechanisms are at play. We used a cross-fostering protocol to experimentally separate the effects of familiarity and genetic relatedness, producing four groups that combined siblings and non-siblings reared together or apart. Behavior was assessed in two experimental setups: (i) a y-maze to test olfactory preferences and (ii) a dyadic encounter arena to evaluate social interactions. In the y-maze, each experimental subject was simultaneously exposed to one sibling and one non-sibling (stimuli pair, SP), both of the opposite sex. Exploration increased significantly when the subject had no rearing experience with either SP member. Females explored the y-maze more than males. Dyadic encounter experiments showed that rearing experience influenced exploratory and agonistic interactions but not sexual behaviors. Social contact, on the other hand, was more frequent among siblings. Taken together, our results indicate that rearing experience plays a major role in modulating opposite-sex social behaviors in this species.

Insect pollination is known to increase avocado yields, with wild pollinators likely playing an important role. In central Chile, the rapid expansion of avocado orchards has resulted in highly diverse natural habitats being replaced by plantations, potentially negatively impacting wild pollinators and thus avocado production. This study aimed to understand the role of natural habitats and wild pollinators in avocado production by (1) exploring the relationship between flower visitor abundance and diversity, and proximity to natural habitat, (2) quantifying the pollination effectiveness of different insect taxa, and (3) measuring the contribution to avocado production of insect pollinators and exploring how this varies with proximity to natural habitats. We conducted flower visitor observations and controlled pollination trials at different distances to natural habitat in three orchards in central Chile, across three years. The results showed that flower visitor abundance, visitation, richness, and diversity were significantly higher closer to natural habitats. However, this relationship varied across distances, with wild insect abundance and visitation rates approximately 2.55 times higher, richness around 1.6 times higher, and diversity 1.5 times higher at the natural habitat edge compared to further inside the orchard. Insect pollinators contributed significantly to avocado production, with almost no fruit set when pollinators were excluded. Hoverflies and other flies were identified as potentially important avocado pollinators. This study demonstrates the importance of natural habitats and wild insect pollination services in crop production. We recommend that growers implement land management practices that protect and restore natural areas in and around their orchards to support wild pollinators.

Pollination niches, which encompass the factors influencing pollen exchange among angiosperms, are fundamental to understanding reproductive success and the intricate eco-evolutionary dynamics of plants. In this study, we investigated pollination niche shift among four sympatric Eriosyce cacti with restricted distributions in the South American Mediterranean region. Utilizing a comprehensive approach—including pollination niche analysis, pollinator color perception studies, reproductive output assessments, molecular phylogenetics, gene flow analyses, and species distribution modeling—we revealed a significant pollination niche displacement in E. chilensis and its variety, E. chilensis var. albidiflora. These taxa transitioned from a hummingbird-pollinated system prevalent in the Eriosyce sect. Neoporteria, characteristic of their sister species E. litoralis, to a bee-pollination strategy akin to that of the co-occurring species E. mutabilis. This shift highlights a simultaneous convergence of E. chilensis toward E. mutabilis and divergence from E. litoralis in pollination strategies, providing adaptive advantages by reducing pollen limitation and enhancing seed production. The morphological and flowering phenological similarities between E. chilensis and E. mutabilis suggest the evolution of a shared advertising display, potentially indicative of floral mimicry, wherein both species benefit from attracting shared bee pollinators. Genomic analyses reveal distinct pollinator-driven selection pressures, with E. chilensis/E. albidiflora exhibiting traits that promote reproductive isolation from E. litoralis, supporting a scenario of rapid speciation occurring within the past half of million years in the absence of geographic barriers. These findings underscore the pivotal role of pollinator interactions in shaping angiosperm speciation and biodiversity, highlighting their dynamic influence on ecological and evolutionary processes.

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.

Although birds have traditionally been considered anosmic, increasing evidence indicates that olfaction plays an important role in the foraging behaviours of insectivorous birds. Recent studies have shown that birds can exploit herbivore-induced plant volatiles and sexual pheromones of adult insects to locate their prey. Many insectivorous birds prey on immature insects, providing relevant ecosystem services as pest regulators in natural and agricultural ecosystems. We asked whether birds could rely on chemical cues emitted by the immature stages of insects to prey on them. To address this question, we performed field experiments to evaluate if insectivorous birds can detect the aggregation pheromone produced by the larvae of the carpenter worm, Chilecomadia valdiviana. Groups of five artificial larvae were placed in branches of 72 adult trees in a remnant fragment of a sclerophyllous forest in central Chile. Each grouping of larvae contained a rubber septum loaded with either larval pheromone as treatment or solvent alone as control. We found that the number of larvae damaged by bird pecks was significantly higher in groups with dispensers containing the larval extract than in control groups. Our results show that birds can rely on immature insect-derived chemical cues used for larvae aggregation to prey on them.

Rising temperatures and increasing drought in Mediterranean-type climate areas are expected to affect plant–pollinator interactions, especially in plant species with specialised pollination. Central Chile experienced a mega drought between 2010 and 2020 which reached an extreme in the austral summer of 2019–2020. Based on intensive pollinator sampling and floral studies we show that the subalpine form of Mutisia subulata (Asteraceae) is a specialised hummingbird-pollinated species. In a two-year study which included the severest drought year, we quantified visitation frequency, flower-head density, flower-head visitation rates, two measures of floral longevity, nectar characteristics and seed set and monitored climatic variables to detect direct and indirect climate-related effects on pollinator visitation. Flower-head density, nectar standing crop and seed set were significantly reduced in the severest drought year while nectar concentration increased. The best model to explain visitation frequency included flower-head density, relative humidity, temperature, and nectar standing crop with highly significant effects of the first three variables. Results for flower-head density suggest hummingbirds were able to associate visual signals with reduced resource availability and/or were less abundant. The negative effect of lower relative humidity suggests the birds were able to perceive differences in nectar concentration. Reduced seed set per flower-head together with the availability of far fewer ovules in the 2019–2020 austral summer would have resulted in a major reduction in seed set. Longer and more intense droughts in this century could threaten local population persistence in M. subulata.

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.