Plant-Pollinator Specialization: Origin and Measurement of Curvature.

AbstractA feature of biodiversity is the abundance of curves displayed by organs and organisms. Curvature is a widespread, convergent trait that has important ecological and evolutionary implications. In pollination ecology, the curvature of flowers and pollinator mouthparts (e.g., hummingbird bills) along the dorsiventral plane has been associated with specialization, competition, and species coexistence. Six differing methods have historically been used to measure curvature in pollination systems; we provide a solution to this inconsistency by defining curvature using well-established concepts from differential geometry. Intuitively, curvature is the degree to which a line is not straight, but more formally it is the rate at which the tangent of a curve changes direction with respect to arc length. Here, we establish a protocol wherein a line is fitted against landmarks placed on an image of a curved organ or organism, then curvature is computed at many points along the fitted line and the sum taken. The protocol is demonstrated by studying the development of nectar spur curvature in the flowering plant genus Epimedium (Berberidaceae). By clarifying the definition of curvature, our aim is to make the language of comparative morphology more precise and broadly applicable to capture other curved structures in nature.

Dark extinction: the problem of unknown historical extinctions.

The extinction of species before they are discovered and named (dark extinction, DE) is widely inferred as a significant part of species loss in the 'pre-taxonomic' period (approx. 1500-1800 CE) and, to some extent, in the 'taxonomic period' (approx. 1800-present) as well. The discovery of oceanic islands and other pristine habitats by European navigators and the consequent introduction of destructive mammals, such as rats and goats, started a process of anthropogenic extinction. Much ecosystem change happened before systematic scientific recording, so has led to DE. Statistical methods are available to robustly estimate DE in the 'taxonomic period'. For the 'pre-taxonomic period', simple extrapolation can be used. The application of these techniques to world birds, for example, suggests that approximately 56 DEs occurred in the 'taxonomic period' (1800-present) and approximately 180 in the 'pre-taxonomic period' (1500-1800). Targeting collection activities in extinction hotspots, to make sure organisms are represented in collections before their extinction, is one way of reducing the number of extinct species without a physical record (providing that collection efforts do not themselves contribute to species extinction).

Adaptation and Latitudinal Gradients in Species Interactions: Nest Predation in Birds.

AbstractAre biotic interactions stronger in the tropics? Here, we investigate nest predation in birds, a canonical example of a strong tropical biotic interaction. Counter to expectations, daily rates of nest predation vary minimally with latitude. However, life-history traits that influence nest predation have diverged between latitudes. For example, tropical species have evolved a longer average nesting period, which is associated with reduced rates of nest attendance by parents. Daily nest mortality declines with nesting period length within regions, but tropical species have a higher intercept. Consequently, for the same nesting period length, tropical species experience higher daily nest predation rates than temperate species. The implication of this analysis is that the evolved difference in nesting period length between latitudes produces a flatter latitudinal gradient in daily nest predation than would otherwise be predicted. We propose that adaptation may frequently dampen geographic patterns in interaction rates.

Dissecting the 'bacon and eggs' phenotype: transcriptomics of post-anthesis colour change in Lotus.

Background and Aims: Post-anthesis colour change (PACC) is widely thought to be an adaptation to signal floral suitability to pollinators. Lotus filicaulis and Lotus sessilifolius are insect-pollinated herbaceous legumes with flowers that open yellow, shift to orange and finally red. This study examines the molecular basis for floral colour change in these Lotus species. Methods: Lotus filicaulis was cultivated in a glasshouse from which pollinating insects (bees) were excluded, and the rate of colour change was recorded in both unpollinated and manually pollinated flowers. Unpollinated flowers from both the yellow stage and the red stage were sampled for sequencing. The transcriptomes of L. filicaulis and L. sessilifolius of both colour stages were analysed for differentially expressed genes and enriched ontologies. Key Results: The rate of progression through PACC doubled when L. filicaulis was hand-pollinated. De novo assembly of RNA-Seq reads from non-model Lotus species outperformed heterologous alignment of reads to the L. japonicus genome. Differential expression analysis suggested that the carotenoid biosynthetic pathway is upregulated at anthesis while the flavonoid biosynthetic pathway is upregulated with the onset of PACC in L. filicaulis and L. sessilifolius . Conclusion: Pollination significantly accelerates PACC in L. filicaulis , consistent with the hypothesis that PACC increases pollination efficiency by directing pollinators to unpollinated flowers. RNA-Seq results show the synchronized upregulation of the entire cyanidin biosynthesis pathway in the red stage of PACC in L. filicaulis and L. sessilifolius . The genes implicated offer the basis for further investigations into how gene families, transcription factors and related pathways are likely to be involved in PACC.

Macroevolution of the plant-hummingbird pollination system.

Plant-hummingbird interactions are considered a classic example of coevolution, a process in which mutually dependent species influence each other's evolution. Plants depend on hummingbirds for pollination, whereas hummingbirds rely on nectar for food. As a step towards understanding coevolution, this review focuses on the macroevolutionary consequences of plant-hummingbird interactions, a relatively underexplored area in the current literature. We synthesize prior studies, illustrating the origins and dynamics of hummingbird pollination across different angiosperm clades previously pollinated by insects (mostly bees), bats, and passerine birds. In some cases, the crown age of hummingbirds pre-dates the plants they pollinate. In other cases, plant groups transitioned to hummingbird pollination early in the establishment of this bird group in the Americas, with the build-up of both diversities coinciding temporally, and hence suggesting co-diversification. Determining what triggers shifts to and away from hummingbird pollination remains a major open challenge. The impact of hummingbirds on plant diversification is complex, with many tropical plant lineages experiencing increased diversification after acquiring flowers that attract hummingbirds, and others experiencing no change or even a decrease in diversification rates. This mixed evidence suggests that other extrinsic or intrinsic factors, such as local climate and isolation, are important covariables driving the diversification of plants adapted to hummingbird pollination. To guide future studies, we discuss the mechanisms and contexts under which hummingbirds, as a clade and as individual species (e.g. traits, foraging behaviour, degree of specialization), could influence plant evolution. We conclude by commenting on how macroevolutionary signals of the mutualism could relate to coevolution, highlighting the unbalanced focus on the plant side of the interaction, and advocating for the use of species-level interaction data in macroevolutionary studies.

Floral phenology of an Andean bellflower and pollination by buff-tailed sicklebill hummingbird.

The Andean bellflowers comprise an explosive radiation correlated with shifts to specialized pollination. One diverse clade has evolved with extremely curved floral tubes and is predicted to be pollinated exclusively by one of two parapatric species of sicklebill hummingbirds (Eutoxeres). In this study, we focused on the floral biology of Centropogon granulosus, a bellflower thought to be specialized for pollination by Eutoxeres condamini, in a montane cloud forest site in southeastern Peru. Using camera traps and a pollination exclusion experiment, we documented E. condamini as the sole pollinator of C. granulosus. Visitation by E. condamini was necessary for fruit development. Flowering rates were unequivocally linear and conformed to the "steady-state" phenological type. Over the course of >1800 h of monitoring, we recorded 12 E. condamini visits totaling 42 s, indicating traplining behavior. As predicted by its curved flowers, C. granulosus is exclusively pollinated by buff-tailed sicklebill within our study area. We present evidence for the congruence of phenology and visitation as a driver of specialization in this highly diverse clade of Andean bellflowers.

Global urban environmental change drives adaptation in white clover.

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale.

Anti-Inflammatory Activity of Haskap Cultivars is Polyphenols-Dependent.

Haskap (Lonicera caerulea L.) berries have long been used for their health promoting properties against chronic conditions. The current study investigated the effect of Canadian haskap berry extracts on pro-inflammatory cytokines using a human monocytic cell line THP-1 derived macrophages stimulated by lipopolysaccharide. Methanol extracts of haskap from different growing locations in Canada were prepared and characterized for their total phenolic profile using colorimetric assays and liquid chromatography-Mass spectrometry (UPLC-MS/MS). Human THP-1 monocytes were seeded in 24-well plates (5 × 105/well) and treated with phorbol 12-myristate 13-acetate (PMA, 0.1 µg/mL) for 48 h to induce macrophage differentiation. After 48 h, the differentiated macrophages were washed with Hank's buffer and treated with various concentrations of test compounds for 4 h, followed by the lipopolysaccharide (LPS)-stimulation (18 h). Borealis cultivar showed the highest phenolic content, flavonoid content and anthocyanin content (p < 0.05). A negative correlation existed between the polyphenol concentration of the extracts and pro-inflammatory cytokines: Interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-α), prostaglandin (PGE2), and cyclooxygenase-2 (COX-2) enzyme. Borealis exhibited comparable anti-inflammatory effects to COX inhibitory drug, diclofenac. The results showed that haskap berry polyphenols has the potential to act as an effective inflammation inhibitor.

Biting the hand that feeds you: wedge-billed hummingbird is a nectar robber of a sicklebill-adapted Andean bellflower / Muerde la mano que le da de comer: Colibrí pico cuña el ladrón de néctar de Centropogon granulosus (Campanulaceae)

Informo sobre el comportamiento de robo de néctar del colibrí pico cuña, Schistes geoffroyi (Trochilidae) en la flor campanulada neotropical, Centropogon granulosus (Campanulaceae). Muchas especies de Centropogon se caracterizan por tener una flor tubular curvada de distintas formas y probablemente especializadas para ser polinizadas por los colibríes de pico curvo (Eutoxeres), como es evidente a partir de la curvatura tanto de la flor como del pico. Debido a la exclusividad de este mutualismo, el robo de néctar ha sido ocasionalmente documentado en Centropogon. Aquí amplío el estudio de robo de néctar de Centropogon incluyendo a Schistes geoffroyi. Esta expansión puede ser un indicador de la alta especialización entre el mutualismo de Centropogon y el colibrí de pico curvo, siendo esta más susceptible al robo de néctar de lo que pensaba previamente. Esto genera preguntas acerca de la evolución de la especialización y parasitismo en este grupo tropical, tanto de las campanuladas como de los colibríes.

I report on nectar robbing behavior of the wedge-billed hummingbird, Schistes geoffroyi (Trochilidae) on the Andean bellflower, Centropogon granulosus (Campanulaceae). Many species of Centropogon are characterized by an abruptly curved corolla tube which is likely specialized for pollination by sicklebill hummingbirds (Eutoxeres), as evident from the matching curvature of flower and bill. Nectar robbing has been documented for some Centropogon spp., but not for sicklebill pollinated C. granulosus. Given recent developments and interest in the Centropogon-sicklebill mutualism, it is pertinent to document any natural history observations that may underlie the ecology and evolution of this pollination system. The establishment of wedge-billed hummingbird as a nectar robber of C. granulosus calls for a new assessment of the ecology and evolution of the highly specialized Centropogon-sicklebill mutualism.