Fernanda Pérez

Ancestral reconstruction of flower morphology and pollination systems in Schizanthus (Solanaceae)

Concerted changes in flower morphology and pollinators provide strong evidence on adaptive evolution. Schizanthus (Solanaceae) has zygomorphic flowers and consists of 12 species of annual or biennial herbs that are distributed mainly in Chile and characterized by bee-, hummingbird-, and moth-pollination syndromes. To infer whether flowers diversified in relation to pollinator shifts, we traced the evolutionary trajectory of flower traits and visitors onto a phylogeny based on sequence data from ITS, waxy, and trnF/ndhJ DNA. Maximum-likelihood ancestral reconstruction of floral traits suggests that ancestral Schizanthus had a bee-pollination syndrome. The hummingbird syndrome evolved in S. grahamii, a high elevation species in the Andes. The moth syndrome evolved in the ancestor of three species that inhabit the Atacama Desert. Results of mapping flower visitors onto the phylogeny show that the shift from bee to hummingbird pollination concurred with a shift in pollinators as predicted by the syndromes. However, the same pattern was not found for the moth syndrome. Visits by moths were observed only in one of the three moth-syndrome species, and at a very low rate. This mismatch suggests either anachronic floral characters or maintenance of rare, imperceptible moth pollination backed up by capacity for autonomous selfing. Overall, results suggest that diversification of flower traits in Schizanthus has occurred in relation to pollinator shifts.

Phylogenetic analysis of floral integration in Schizanthus (Solanaceae): does pollination truly integrate corolla traits?

To assess whether floral integration patterns result from the action of pollinator selection on functionally related traits, we compared corolla integration patterns in eight Schizanthus species differing in pollination systems and in their degree of pollinator dependence across a molecular phylogeny. Integration patterns differed among species and these differences were not related to their phylogenetic relatedness. When the putative original function of some corolla traits was lost in pollinator‐dependent species, the integration among nonfunctional characters and the rest of the corolla traits was disrupted. This pattern was not presented in species adapted for late autonomous selfing, which exhibited higher corolla integration than their pollinator‐dependent relatives. These results suggest that corolla integration in pollinator‐dependent species was shaped by pollinator‐mediated selection. Decoupling of nonfunctional traits in these species may result from a relaxation of correlational selection or from selection acting against a default covariation provided by genetic and developmental connections.

Evolution of autonomous selfing accompanies increased specialization in the pollination system of Schizanthus (Solanaceae)

The co-occurrence of elaborate flowers visited by specific groups of pollinators and capacity for autonomous selfing in the same plant species has puzzled evolutionary biologists since the time of Charles Darwin. To examine whether autonomous selfing and floral specialization evolved in association, we quantified the autofertility level (AFI) in nine Schizanthus species characterized by a wide range of pollination specialization, revealing AFI values of 0.02 to complete selfing. An independent contrasts analysis conducted on AFIs and number of functional pollinator groups showed that autonomous selfing evolved from an ancestral outcrossing system as plants became increasingly specialized (r = -0.82). To assess whether autonomous selfing together with specialization acts as a reproductive assurance mechanism, we estimated spatial and interannual variation in fruit set due to pollinator failure in two closely related high Andean Schizanthus species differing in their specialization levels. Variation in pollinator failure rate was more pronounced and autonomous selfing increased fruit production over biotically assisted pollination in the more specialized species. Our study suggests that specialized pollination deems species more vulnerable to pollinator fluctuation thus promoting the evolution of delayed autonomous selfing.

STRONG PHENOTYPIC VARIATION IN FLORAL DESIGN AND DISPLAY TRAITS OF AN ANNUAL TARWEED IN RELATION TO SMALL-SCALE TOPOGRAPHIC HETEROGENEITY IN SEMIARID CHILE

Floral trait expression in wild populations varies in relation to environmental gradients. Variation can be observed among and within plant populations. We investigated the changes in floral phenotype within populations and the probability of plant pollinator visits in relation to small-scale variation in soil moisture and plant cover in a semiarid ecosystem. We measured the variability of floral phenotypes of three wild populations of Madia chilensis along a gradient constituted by three topographic positions (south-facing slope, north-facing slope, and ravine). Changes in soil moisture, plant density, leaf water content, and internode elongation were measured for one population over two study years. Pollinator visit probabilities were also estimated. Floral phenotypes were strongly segregated among topographic positions but less segregated among populations. Plants with the lowest water contents and the smallest or least-conspicuous flower heads grew in the drier north-facing slope, while plants with the highest water contents and showier flower design and display grew in the wetter ravine. Probabilities of pollinator visits were higher on the north-facing slope. Differences in floral phenotypes and probabilities of pollinator visits of M. chilensis were strongly connected to topographic variations at small spatial scale. Topographic heterogeneity at small spatial scale could thus have important consequences for floral trait evolution and pollination ecology.

Microsatellite markers for the high Andean species Schizanthus hookeri and S. grahamii (Solanaceae)

PREMISE OF THE STUDY Seven microsatellite loci were developed for the two closely related high Andean species Schizanthus hookeri and S. grahamii. These species are annual to biannual herbs with zygomorphic and showy flowers that differ in floral morphology, autonomous selfing capacity, and in the identities of major flower visitors. METHODS AND RESULTS Polymorphisms were evaluated in a total of 45 plants, including individuals from two populations of S. grahamii and one population of S. hookeri. The number of alleles per locus ranged from two to nine in each population. We also tested these loci for cross-amplification in another seven species of the genus. Four primer pairs amplified in these seven species. CONCLUSIONS Characterized microsatellites are conserved in the closely related species S. hookeri and S. grahamii, and they have enough polymorphism to be used in future studies of their mating systems and genetic structure.

A metabolic view of amphibian local community structure: the role of activation energy

In the context of the metabolic theory of ecology (MTE), the activation energy (E) reflects the temperature dependence of metabolism and organism performance in different activities, such as calling behavior. In this contribution we test the role of temperature in affecting local amphibian community structure, particularly the number of species engaged in calling behavior across a temperature gradient. Toward this aim, we compiled phenological calling activity for 52 Neotropical anuran communities. For each community we estimated the activation energy of calling behavior (E), finding values significantly higher than previous reports. A wide range of methodological issues with the potential to produce overestimated E-values were shown to have no significant effect on reported E-values, supporting a biological interpretation of their high values and of geographic trends. Further, a path analysis related variation in E among communities with communities’ phylogenetic structure, local environmental conditions, richness, and seasonality. The decrease of activation energy at higher latitudes and less productive environments suggests that amphibians’ activity could become more dependent of internal individuals’ resources once external sources are reduced. The increase in phylogenetic attraction with latitude points to a rise in the role of niche conservatism and community filtering operating over conserved traits. Finally, flexibility in activation energy related to amphibians’ calling could be an important and poorly recognized determinant of their thermal dependence. The temporal structuring of amphians’ communities was related here with the interplay between ecological and evolutionary processes operating at different scales. Our results support the view of activation energy as an important parameter of biodiversity organization, which unravels the effects of ecological and evolutionary processes on biodiversity structure and function.

Assessing the influence of life form and life cycle on the response of desert plants to past climate change: Genetic diversity patterns of an herbaceous lineage ofNolanaalong western South America

PREMISE OF THE STUDY Plant responses to past climate change could have been shaped by life-history traits. Here we explore the influence of life form on the response of xerophytic plants to Quaternary climate fluctuations, through a comparison of genetic patterns of codistributed herbaceous and shrubby lineages of the genus Nolana. METHODS We reconstructed the phylogeographic history of a herbaceous lineage of three species of Nolana distributed from a northern arid zone (30°S) to a southern wet-temperate (42°S) zone, by sequencing two cpDNA regions. Results were compared with similar data published earlier for a congeneric, codistributed shrubby lineage. KEY RESULTS We detected significant genetic differentiation among populations. Divergence of all haplotypes occurred during the Pleistocene, between 245 and 62 kyr ago. For both the shrubby and herbaceous lineages, the greatest haplotype diversity was found in their northern range. However, herbs also retained some diversity at higher latitude. Herbaceous populations were less genetically structured and less differentiated than shrubby ones. CONCLUSION Genetic evidence revealed that both lineages of Nolana survived climate change through the Quaternary, experiencing population collapses and recoveries. Phylogeographic histories present similarities between the two lineages, but also marked differences that can be explained by their differences in life form and life cycle. While the shrubby lineage followed the classical pattern of postglacial expansion toward higher latitudes, species in the herbaceous lineage showed evidence of long-lasting persistence at the southern edge of their current range, suggesting for the first time multiple glacial refugia for a xerophytic plant in southern South America.