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Historical geological events and Pleistocene climatic fluctuations have played important roles in shaping distribution and population differentiation across taxa. The buff-bellied hummingbird (Amazilia yucatanensis) is widely distributed along the Gulf of Mexico slope and the Yucatan Peninsula. Here, we obtained measurements and sequenced two mitochondrial DNA fragments from currently recognized subspecies: Amazilia yucatanensis yucatanensis (YUC), Amazilia yucatanensis cerviniventris (CER) and Amazilia yucatanensis chalconota (CHA). Additionally, we tested for their genetic and morphological differentiation, demographic expansion, palaeoclimatic distribution and niche overlap. Our results reveal genetic differentiation between two groups of populations: (1) from the Yucatan Peninsula to Veracruz (YUC+CER); and (2) from Veracruz to Tamaulipas (CHA). Neutrality tests and Bayesian skyline plots suggest past demographic expansion without changes in the effective population size over time. The potential distribution was fragmented at the Trans-Mexican Volcanic Belt and expanded northwards during the Last Glacial Maximum and Mid-Holocene to current conditions. Niche overlap was higher between YUC and CER. The environmental space occupied by subspecies was more similar to each other than expected by chance but significantly non-equivalent. Our results provide new insight on the distribution of this widespread hummingbird species and suggest that fragmentation during glaciations and differences in habitat have played a role in the recent diversification.

Antecedentes y Objetivos: La mayoría de los frutos de los muérdagos de Psittacanthus (Loranthaceae) para la dispersión de sus semillas dependen de las aves frugívoras, y el comportamiento de estos dispersores influye en sus patrones de distribución espacial dentro y entre hospederos. A pesar de la importancia de las aves en su dispersión y distribución, los efectos de la especie de hospedero en la variación del tamaño de los frutos no han sido investigados de manera extensa. El objetivo de este estudio fue caracterizar la variación del tamaño de los frutos maduros de Psittacanthus schiedeanus que crecen en diferentes especies de hospedero. Esperamos que los rasgos del tamaño de los frutos varíen de acuerdo con la calidad de la especie del hospedero, y que esta variación se corresponda con la del éxito reproductivo del muérdago. Métodos: Frutos maduros de plantas de muérdagos Psittacanthus schiedeanus creciendo en especies diferentes de árboles hospederos fueron colectados en dos sitios (Tlalnelhuayocan y Coapexpan) de bosque mesófilo de montaña en el centro de Veracruz, México, medidos (largo y ancho y largo de los pedicelos cupulares) y pesados para describir las diferencias en su tamaño. Resultados clave: La longitud del pedicelo cupular y el tamaño del fruto se vieron significativamente afectados por la especie de hospedero. En promedio, pedicelos cupulares más largos y frutos más grandes se encontraron en plantas que crecen en Acacia pennatula, Quercus germana, Ostrya virginiana y Liquidambar styraciflua, mientras que los más pequeños se encontraron generalmente en plantas sobre árboles hospederos cultivados. Conclusiones: Los resultados nos brindan información valiosa para futuras comparaciones entre especies en relación con los efectos de la especie de hospedero en la variación del tamaño de los frutos. Aunque los efectos de la especie de hospedero en la variación del tamaño de los frutos pueden variar en el espacio, las diferencias en el tamaño de los frutos pueden ser el resultado de diferencias en el recurso del hospedero. Se necesitan más estudios sobre la selección y el manejo de los frutos por parte de los dispersores de semillas, para discutir si la variación observada en el tamaño de los frutos se correlaciona con la selección y el manejo de los frutos por parte de los principales consumidores, y con la unión y el establecimiento exitosos en la rama del hospedero después del paso por el tracto intestinal.

The Dusky Hummingbird Phaeoptila sordida (= Cynanthus sordidus), occurs in the Balsas Basin, a region with a complex biogeographical history, and in the Tehuacán-Cuicatlán Valley and Valles Centrales in Puebla and Oaxaca, Mexico. However, the biogeographical and evolutionary history of these two regions of Mexico is poorly understood. We aimed to understand the genetic structure and phylogeographic history of P. sordida, a range-restricted hummingbird to these two regions, as a proxy to study the evolutionary history of the Balsas Basin, by using mitochondrial DNA (mtDNA) sequences and nuclear microsatellites. Geographic structure was evident for both markers; however, some discordance was observed between the mitochondrial and nuclear markers. Based on mtDNA, samples from the Balsas Basin form one haplogroup, well separated from the Tehuacán-Cuicatlán Valley and Valles Centrales samples. In contrast to this, nuclear microsatellites uncovered two slightly different genetic clusters restricted to different habitats: samples from the Western Balsas restricted to the seasonally deciduous tropical dry forest, and samples from the Eastern Balsas-Tehuacán/Cuicatlán-Tehuantepec area in shrub and dry forested habitats. As expected by the interglacial refugia hypothesis, ENM predicted that the distribution of P. sordida was more contracted and fragmented during the Last Inter Glacial and more expanded at the Last Glacial Maximum. Consistent with that observed for other range-restricted hummingbird species, ENM predictions and a strong signal of population expansion indicate that the geographical range and population size are unstable over time, as compared to widespread hummingbird species, and that ecological and climatic factors possibly impacted its diversification. This study contributes to the debate that disputes the integrity of the Balsas Basin as a biogeographical unit and urges for the conservation of endemic species in the Balsas region and interior Oaxaca.

Functional traits can determine pairwise species interactions, such as those between plants and pollinators. However, the effects of biogeography and evolutionary history on trait-matching and trait-mediated resource specialization remain poorly understood.We compiled a database of 93 mutualistic hummingbird-plant networks (including 181 hummingbird and 1,256 plant species), complemented by morphological measures of hummingbird bill and floral corolla length. We divided the hummingbirds into their principal clades and used knowledge on hummingbird biogeography to divide the networks into four biogeographical regions: Lowland South America, Andes, North & Central America, and the Caribbean islands. We then tested: (a) whether hummingbird clades and biogeographical regions differ in hummingbird bill length, corolla length of visited flowers and resource specialization, and (b) whether hummingbirds' bill length correlates with the corolla length of their food plants and with their level of resource specialization.Hummingbird clades dominated by long-billed species generally visited longer flowers and were the most exclusive in their resource use. Bill and corolla length and the degree of resource specialization were similar across mainland regions, but the Caribbean islands had shorter flowers and hummingbirds with more generalized interaction niches. Bill and corolla length correlated in all regions and most clades, that is, trait-matching was a recurrent phenomenon in hummingbird-plant associations. In contrast, bill length did not generally mediate resource specialization, as bill length was only weakly correlated with resource specialization within one hummingbird clade (Brilliants) and in the regions of Lowland South America and the Andes in which plants and hummingbirds have a long co-evolutionary history. Supplementary analyses including bill curvature confirmed that bill morphology (length and curvature) does not in general predict resource specialization.These results demonstrate how biogeographical and evolutionary histories can modulate the effects of functional traits on species interactions, and that traits better predict functional groups of interaction partners (i.e. trait-matching) than resource specialization. These findings reveal that functional traits have great potential, but also key limitations, as a tool for developing more mechanistic approaches in community ecology.A free Plain Language Summary can be found within the Supporting Information of this article.

The Pleistocene climate cycles and mountain uplift both affected the diversification of taxa in Mesoamerica. Yet, phylogeographic breaks and demographic responses of co-distributed taxa are not congruent. Investigation of more species with widespread distributions across Mexico and Central America will help shed light on how Earth historical events shaped biodiversity in this region. The Azure-crowned Hummingbird (Amazilia cyanocephala) is widely distributed from eastern Mexico into Central America and has been divided into three subspecies by morphology and geographic isolation. To investigate the evolutionary history of the species, we sequenced a non-coding mtDNA fragment along with a nuclear marker across its distribution, and analysed morphological and ecological variation and distributional projections derived from ecological niche modelling. Overall, mtDNA supported genetic differentiation among A. cyanocephala populations, which generally supports the existence of four lineages: two A. c. cyanocephala lineages separated by the Isthmus of Tehuantepec (east and west), A. c. guatemalensis populations separated by the Motagua-Polochic-Jocotan fault system, and the isolated A. c. chlorostephana in Honduras and Nicaragua. However, morphological data were not consistent with this phylogeographic result. The potential distribution of suitable habitat for A. cyanocephala was expanded during the Last Glacial Maximum and more contracted and fragmented during the Last Inter-Glacial and the Present. These models are consistent with a preglacial demographic expansion in A. c. cyanocephala. Mitochondrial genetic diversity and current precipitation seasonality were negatively correlated when analysing all populations. We suggest that isolation and habitat differences have both played a role in the recent diversification of A. cyanocephala. Inferences about the demographic consequences of isolation and subspecies recognition await further study.

Species with genetically differentiated allopatric populations commonly differ in phenotypic traits due to drift and/or selection, which can be important drivers of reproductive isolation. Wedge-tailed sabrewing (Campylopterus curvipennis) is a species complex composed of three genetically and acoustically differentiated allopatric lineages that correspond to currently recognized subspecies in Mexico: C. c. curvipennis (Sierra Madre Oriental), C. c. pampa (Yucatán Peninsula), and C. c. excellens (Los Tuxtlas). Although excellens is taxonomically recognized as a distinct species, there is genetic evidence that lineages excellens and curvipennis have diverged from each other later than pampa. In this study, we experimentally tested C. c. curvipennis song recognition as a major factor in premating reproductive isolation for lineage recognition. To this end, we conducted a song playback experiment to test whether territorial males of one C. c. curvipennis lek discriminate among potential competitors based on male songs from the three lineages. Males of curvipennis responded more aggressively to songs of their own lineage and excellens, than to songs of the most divergent lineage pampa, as evidenced by significant differences in a variety of intensity and latency response variables. This indicate that the pampa male song does not represent a competitive threat as curvipennis and excellens songs, in which divergence and song recognition represent premating reproductive isolation between these isolated lineages. However, the acoustic limits between curvipennis and excellens might be attenuated by gene flow in case of secondary contact between them, despite the strong and relatively rapid divergence of their sexually selected song traits.

The Pleistocene glacial cycles had a strong influence on the demography and genetic structure of many species, particularly on northern-latitude taxa. Here we studied the phylogeography of the white-eared hummingbird (Hylocharis leucotis), a widely distributed species of the highlands of Mexico and Central America. Analysis of mitochondrial DNA (mtDNA) sequences was combined with ecological niche modelling (ENM) to infer the demographic and population differentiation scenarios under present and past conditions. Analyses of 108 samples from 11 geographic locations revealed population structure and genetic differentiation among populations separated by the Isthmus of Tehuantepec (IT) and the Motagua-Polochic-Jocotán (MPJ) fault barriers. ENM predicted a widespread distribution of suitable habitat for H. leucotis since the Last Inter Glacial (LIG), but this habitat noticeably contracted and fragmented at the IT. Models for historical dispersal corridors based on population genetics data and ENM revealed the existence of corridors among populations west of the IT; however, the connectivity of populations across the IT has changed little since the LIG. The shallow geographic structure on either side of the isthmus and a star-like haplotype network, combined with the long-term persistence of populations across time based on genetic data and potential dispersal routes, support a scenario of divergence with migration and subsequent isolation and differentiation in Chiapas and south of the MPJ fault. Our findings corroborate the profound effects of Pleistocene climatic fluctuations on the evolutionary history of montane taxa but challenge the generality of expanded suitable habitat (pine-oak forests) during glacial cycles.

Differential visitation of pollinators due to divergent floral traits can lead to reproductive isolation via assortative pollen flow, which may ultimately be a driving force in plant speciation, particularly in areas of overlap. We evaluate the effects of pollinator behavioral responses to variation of intraspecific floral color and nectar rewards, on reproductive isolation between two hybrid flower color morphs (fuchsia and blue) and their parental species Penstemon roseus and P. gentianoides with a mixed-pollination system. We show that pollinators (bumblebees and hummingbirds) exhibit different behavioral responses to fuchsia and blue morphs, which could result from differential attraction or deterrence. In addition to differences in color (spectral reflectance), we found that plants with fuchsia flowers produced more and larger flowers, produced more nectar and were more visited by pollinators than those with blue flowers. These differences influenced the foraging behavior and effectiveness as pollinators of both bumblebees and hummingbirds, which contributed to reproductive isolation between the two hybrid flower color morphs and parental species. This study demonstrates how differentiation of pollination traits promotes the formation of hybrid zones leading to pollinator shifts and reproductive isolation. While phenotypic traits of fuchsia and red flowers might encourage more efficient hummingbird pollination in a mixed-pollination system, the costs of bumblebee pollination on plant reproduction could be the drivers for the repeated shifts from bumblebee- to hummingbird-mediated pollination.

A major barrier to advancing ornithology is the systemic exclusion of professionals from the Global South. A recent special feature, Advances in Neotropical Ornithology, and a shortfalls analysis therein, unintentionally followed a long-standing pattern of highlighting individuals, knowledge, and views from the Global North, while largely omitting the perspectives of people based within the Neotropics. Here, we review current strengths and opportunities in the practice of Neotropical ornithology. Further, we discuss problems with assessing the state of Neotropical ornithology through a northern lens, including discovery narratives, incomplete (and biased) understanding of history and advances, and the promotion of agendas that, while currently popular in the north, may not fit the needs and realities of Neotropical research. We argue that future advances in Neotropical ornithology will critically depend on identifying and addressing the systemic barriers that hold back ornithologists who live and work in the Neotropics: unreliable and limited funding, exclusion from international research leadership, restricted dissemination of knowledge (e.g., through language hegemony and citation bias), and logistical barriers. Moving forward, we must examine and acknowledge the colonial roots of our discipline, and explicitly promote anti-colonial agendas for research, training, and conservation. We invite our colleagues within and beyond the Neotropics to join us in creating new models of governance that establish research priorities with vigorous participation of ornithologists and communities within the Neotropical region. To include a diversity of perspectives, we must systemically address discrimination and bias rooted in the socioeconomic class system, anti-Blackness, anti-Brownness, anti-Indigeneity, misogyny, homophobia, tokenism, and ableism. Instead of seeking individual excellence and rewarding top-down leadership, institutions in the North and South can promote collective leadership. In adopting these approaches, we, ornithologists, will join a community of researchers across academia building new paradigms that can reconcile our relationships and transform science. Spanish and Portuguese translations are available in the Supplementary Material.

Global climate change and habitat loss are displacing tropical montane forests along mountain slopes1–4. Cloud forests are one of the most diverse and fragile of these montane ecosystems5–8, yet little is known about the historical and ongoing impacts of anthropogenic disturbances on these forests. Here we assess historical (1901–2016) changes in the altitudinal range of vascular plant species in Mesoamerican cloud forests and evaluate the relative impacts of climate change and land-use alterations. By analysing thousands of occurrence records from public biological collections, we uncovered common altitudinal shifts across species and suggest an overall contraction of cloud forests starting in the late 1970s. We infered a pervasive and interrelated impact of rising temperatures, changing precipitation patterns, and deforestation on the distribution of cloud forest species across Mesoamerica. Over the last fifty years, cloud forests have declined due to deforestation and warmer and more (seasonally) arid climates9–11. This is pushing species’ to contract their altitudinal ranges and may lead to an increasing probability of abrupt and devastating declines of population sizes, local adaptation, and migration.

The biogeographical history of Mesoamerican cloud forests is complex, encompassing a diverse and heterogeneous mixture of species with temperate and tropical origins. The dynamic geological landscape and climate change from the Miocene to the Pleistocene affected the distributions and composition of cloud forests in the region, and contributed to divergence events at different time scales. We assessed genetic variation of 29 populations of P. matudae, and closely related P. guatemalensis and P. oleifolius (Podocarpaceae) by sequencing 255 samples of the psbA-trnH and trnL-F intergenic spacer regions across the species ranges. We conducted phylogenetic, population and spatial genetic analyses as well as divergence time estimation and ecological niche modelling (ENM) to test the generality of demographic and genetic scenarios for cloud forest-adapted species. The results revealed genetic differentiation among species, with some individuals of P. oleifolius and P. guatemalensis placed in the P. matudae group and some P. oleifolius in the P. guatemalensis group. Predictions of ENMs under past climatic conditions and a strong signal of spatial expansion suggest that the highland P. matudae and P. oleifolius populations experienced expansions into lower elevation during the Last Glacial Maximum (LGM). Contrary to predictions by the two precipitation models and elevational ups and downs for cloud forest taxa during the LGM, genetic differentiation and predicted distribution of suitable habitat support the hypotheses that P. matudae and P. oleifolius remained in situ during the LGM primarily within the current fragmented distribution of the cloud forest and spread into the lowlands during the LGM, whereas the distribution of suitable habitat for P. guatemalensis had no major changes upwards from the Last Inter Glacial (LIG) to current conditions.

Background Plant-pollinator mutualistic networks show non-random structural properties that promote species coexistence. However, these networks show high variability in the interacting species and their connections. Mismatch between plant and pollinator attributes can prevent interactions, while trait matching can enable exclusive access, promoting pollinators’ niche partitioning and, ultimately, modularity. Thus, plants belonging to specialized modules should integrate their floral traits to optimize the pollination function. Herein, we aimed to analyze the biological processes involved in the structuring of plant-hummingbird networks by linking network morphological constraints, specialization, modularity and phenotypic floral integration. Methods We investigated the understory plant-hummingbird network of two adjacent habitats in the Lacandona rainforest of Mexico, one characterized by lowland rainforest and the other by savanna-like vegetation. We performed monthly censuses to record plant-hummingbird interactions for 2 years (2018–2020). We also took hummingbird bill measurements and floral and nectar measurements. We summarized the interactions in a bipartite matrix and estimated three network descriptors: connectance, complementary specialization (H2’), and nestedness. We also analyzed the modularity and average phenotypic floral integration index of each module. Results Both habitats showed strong differences in the plant assemblage and network dynamics but were interconnected by the same four hummingbird species, two Hermits and two Emeralds, forming a single network of interaction. The whole network showed low levels of connectance (0.35) and high specialization (H2’ = 0.87). Flower morphologies ranged from generalized to specialized, but trait matching was an important network structurer. Modularity was associated with morphological specialization. The Hermits Phaethornis longirostris and P. striigularis each formed a module by themselves, and a third module was formed by the less-specialized Emeralds: Chlorestes candida and Amazilia tzacatl. The floral integration values were higher in specialized modules but not significantly higher than that formed by generalist species. Conclusions Our findings suggest that biological processes derived from both trait matching and “forbidden” links, or nonmatched morphological attributes, might be important network drivers in tropical plant-hummingbird systems while morphological specialization plays a minor role in the phenotypic floral integration. The broad variety of corolla and bill shapes promoted niche partitioning, resulting in the modular organization of the assemblage according to morphological specialization. However, more research adding larger datasets of both the number of modules and pollination networks for a wider region is needed to conclude whether phenotypic floral integration increases with morphological specialization in plant-hummingbird systems.

Host trees are the immediate environments for multi-host mistletoes, so parasitizing different hosts through vector-mediated dispersal of their propagules implies exposure to varying environmental conditions between mistletoe generations. Therefore, to maximize their reproductive fitness on heterogeneous environments (host species) mistletoes should (1) respond by locally adapting to the most suitable host species, if dispersal is not limited or host-directed, (2) plastically change their phenotype on different host species, (3) evolve a very general exploitation strategy extending its host range that would counterbalance host resistance, or (4) perform differently across host species with the emergence of locally adapted or maladapted mistletoe populations. Here, we ask how reproductive traits of Psittacanthus calyculatus mistletoes vary on two host tree species (Crataegus mexicana, Prunus serotina) at three different localities. We followed individual mistletoes on each host species and locality through the flowering season to quantify traits related to reproductive effort and success such as the total numbers of buds, flowers and fruits produced. From buds ready to open, we measured two anthers and quantify the number of pollen grains and its viability. Individual flowers were marked to obtain flower longevity, and were followed until fruit formation. Then, we measured and weighed the fruits and its seeds. Mistletoes from one locality produced more buds, flowers and fruits, and flowers lasted longer, had larger anthers and produced more pollen as compared to the other two localities. However, mistletoes on P. serotina produced fewer floral buds, and their fruits were the heaviest, long and widest and with the fastest ripening across localities. The probability of fruit formation, percentage of fruits formed and pollen viability were similar among mistletoes, regardless host species or locality. We propose that the observed differences in reproductive effort and success associated with host species or locality are plastic or adaptive responses of mistletoes in the face of varying conditions.

Genetic variation and phylogeographic studies have been crucial for understanding mechanisms of speciation. We analyzed genetic variation and phylogeography to reconstruct the demographic history of the Rivoli's Hummingbird (Eugenes fulgens) species complex and also evaluated their morphological differentiation. This widely distributed species inhabits the highlands of Mexico and northern Central America, with 2 subspecies separated by the Isthmus of Tehuantepec (west: E. f. fulgens, east: E. f. viridiceps). We surveyed genetic variation in 2 mitochondrial DNA markers (mtDNA, with 129 individuals) and nuclear DNA (6 microsatellites, with 85 individuals). We also inferred the demographic history, estimated divergence times, and analyzed morphological variation using 470 vouchered specimens. We modeled the current potential distribution of the species using ecological niche modeling and projected it into the past to model the effects of the Pleistocene climatic cycles. Haplotype networks, pairwise FST comparisons, AMOVA, and morphological analysis revealed differences between geographically isolated populations separated by the Isthmus of Tehuantepec (IT; corresponding to the 2 recognized subspecies: fulgens and viridiceps), and by the Motagua-Polochic-Jocotan (MPJ) system fault. Demographic scenarios revealed a contraction in distribution during the last interglacial, and expansion during the Last Glacial Maximum (LGM) with little change since the LGM. Divergence between groups separated by the Isthmus of Tehuantepec ∼59,600 yr ago occurred in the presence of gene flow, suggesting that the Isthmus of Tehuantepec is a semipermeable barrier to gene flow. STRUCTURE analyses of microsatellite data detected 3 genetically differentiated groups. Several results fit a model of recent lineage divergence, including a significant signal of genetic differentiation, demographic expansion, decreased gene flow from past to present, and northward expansion during the LGM and contraction during the interglacial periods. We conclude that the genetic differentiation of E. fulgens in the Madrean Pine-Oak Woodlands resulted from recent geographical isolation of populations separated by natural barriers (IT and MPJ).LAY SUMMARYThe present work allowed us to reconstruct the phylogeographic pattern and evolutionary history of Eugenes fulgens in the highlands of Mesoamerica.It revealed the presence of 3 main lineages: populations west of the Isthmus of Tehuantepec (E. fulgens) and 2 populations east of the isthmus (E. viridiceps), geographically isolated from each other by the Isthmus of Tehuantepec and by the Motagua-Polochic-Jocotan system fault.Our results support the hypothesis that the divergence and demographic expansion within the E. fulgens species complex are associated with the Pleistocene glacial–interglacial cycles.

The host dependence of mistletoes suggests that they track the distributions of their hosts. However, the factors that determine the geographic distribution of mistletoes are not well understood. In this study, the phylogeography of Psittacanthus sonorae was reconstructed by sequencing one nuclear (ITS) and two plastid (trnL-F and atpB-rbcL) regions of 148 plants from populations separated by the Sea of Cortez. Divergence time and gene flow were estimated to gain insight into the historical demography and geographic structuring of genetic variation. We also described and mapped the spatial distribution of suitable habitat occupied by P. sonorae and its most common host Bursera microphylla in the Sonoran Desert, along with their responses to Quaternary climate fluctuations using environmental data and ecological niche modeling (ENM). We detected environmental and genetic differentiation between the peninsular and continental P. sonorae populations. Population divergence occurred during the Pleistocene, around the time of the Last Glacial Maximum. No signals of population growth were detected, with net gene flow moving from the continent to the peninsula. ENM models indicate decoupled responses by the mistletoe and its main host to past climate changes. For the Last Interglacial to the present, most models produce only partial areas of overlap on both the peninsula and the continent. Our results support a scenario of Late-Pleistocene isolation and divergence with asymmetrical gene flow between peninsular and continental P. sonorae populations. Continental populations migrated to the peninsula and the spatial isolation probably produced genetic differentiation under different environmental conditions.

Studies in evolutionary biology have commonly been focused on insular systems because of their natural geographic isolation and relatively simpler biotas. Using mitochondrial DNA sequences of 4 passerine bird species distributed in the Tres Marias Archipelago (TMA) and the nearby mainland of western Mexico—Cardinalis cardinalis, Turdus rufopalliatus, Vireo hypochryseus, and Icterus pustulatus—we determined interspecific and intraspecific phylogenetic relationships between insular and mainland populations, conducted insular age-based time calibration for the estimation of divergence times, and used Bayesian analyses to examine the colonization history of islands. Specifically, we tested whether the study species from the TMA share the same colonization history since the emergence of the islands ∼120 kya, taking advantage of the reduced isolation due to sea-level fluctuations during the Pleistocene, or whether there were independent colonization events. We also looked for evidence in the genetic st...

The predominantly Asian tribe Miliuseae (Annonaceae) includes over 37 Neotropical species that are mainly distributed across Mesoamerica, from southern Mexico to northern Colombia. The tremendous ecological and morphological diversity of this clade, including ramiflory, cauliflory, flagelliflory, and clonality, suggests adaptive radiation. Despite the spectacular phenotypic divergence of this clade, little is known about its phylogenetic and evolutionary history. In this study we used a nuclear DNA marker and seven chloroplast markers, and maximum parsimony, maximum likelihood and Bayesian inference methods to reconstruct a comprehensive time-calibrated phylogeny of tribe Miliuseae, especially focusing on the Desmopsis-Stenanona clade. We also perform ancestral area reconstructions to infer the biogeographic history of this group. Finally, we use ecological niche modeling, lineage distribution models, and niche overlap tests to assess whether geographic isolation and ecological specialization influenced the diversification of lineages within this clade. We reconstructed a monophyletic Miliuseae that is divided into two strongly supported clades: (i) a Sapranthus-Tridimeris clade and (ii) a Desmopsis-Stenanona clade. The colonization of the Neotropics and subsequent diversification of Neotropical Miliuseae seems to have been associated with the expansion of the boreotropical forests during the late Eocene and their subsequent fragmentation and southern displacement. Further speciation within Neotropical Miliuseae out of the Maya block seems to have occurred during the last 15 million years. Lastly, the geographic structuring of major lineages of the Desmopsis-Stenanona clade seems to have followed a climatic gradient, supporting the hypothesis that morphological differentiation between closely related species resulted from both long-term isolation between geographic ranges and adaptation to environmental conditions.

The present day distribution and spatial genetic diversity of Mesoamerican biota reflect a long history of responses to complex topography, geological history and climate changes. The hummingbird Colibri thalassinus thalassinus is distributed in northern Mesoamerica, with geographically disjunct populations mainly separated by the Isthmus of Tehuantepec (IT). Based on sampling across the species range in Mexico, we use mitochondrial DNA (mtDNA) sequences and distributional projections derived from ecological niche modeling (ENM) to test whether (1) populations are genetically differentiated according to the fragmented distribution of C. thalassinus thalassinus in Mexico, and (2) historical demographic patterns of these hummingbird populations correspond to those of expanded populations during the Last Glacial Maximum (LGM). Analysis of genetic variation revealed two main mtDNA lineages: populations west of the IT along the Sierra Madre Oriental, Trans-Mexican Volcanic Belt and Sierra Madre del Sur and populations east of the isthmus in Chiapas and Guatemala. A significant signal of genetic differentiation, demographic expansion near the LGM, and contractions/expansions of suitable environmental conditions during the LGM fit a model of lineage divergence west of the isthmus after the LGM, and that the species’ suitable habitat was continuous connecting populations on either side of the isthmus. We conclude that the genetic differentiation of C. thalassinus thalassinus in Mexico resulted from recent geographical isolation of populations separated by the IT. In addition, this scenario is supported by the modeled paleodistribution that suggests that populations expanded during the LGM, and that the spread of the species into the highlands caused habitat fragmentation and population isolation for C. thalassinus thalassinus during the interglacial periods. The findings corroborate the profound effects of Pleistocene climatic fluctuations on the genetic differentiation of C. thalassinus thalassinus in Mexico but challenge the generality of glacial refugia.

Considering that parasitic plant distributions are constrained by host availability, we measure the effects of adding information of host distributions to predict distributions of mistletoes under ...

While the influence of mistletoe–host interactions on each other’s evolution is well-recognized, the role of interactions between mistletoes and its mutualistic pollinators and seed dispersers mediated by host species is relatively unexplored. Here, we examine the effects of host species (Mexican hawthorn Crataegus mexicana DC, black cherry Prunus serotina Ehrh., leather-leaf Mexican oak Quercus crassipes Bonpl.) on flower morphology, nectar production, pollinator visitation rate and female reproductive fitness in hemiparasitic Mexican mistletoe Psittacanthus calyculatus (DC.) G. Don (Loranthaceae) populations at three different locations. We first measured the lengths of corolla, style, stamen, exerted stamen and anther, the length and width of the ovary and nectar availability for mistletoe flowers in natural populations. Then, we evaluated flower visitation and measured (length and width) and weighed the fruits and its seeds of mistletoes growing on each of the three host species. Finally, we evaluated the effects of host species, location and flower traits on fruit or seed size variation (both as proxies of reproductive fitness). We found mistletoes growing on natural hosts P. serotina and Q. crassipes produced larger flowers, fruits and seeds than mistletoes on cultivated C. mexicana. However, these differences varied across space. The amount of available nectar and hummingbird visitation rates in flowers of mistletoes on C. mexicana was higher at the three sites than in flowers of mistletoes on P. serotina or Q. crassipes. The effects of host species, study site and floral trait covariates affected significantly all fitness measures, indicating that mistletoes’ reproductive fitness is affected differently depending on the host species and their site of occurrence. These host-associated differences in reproduction might have implications for interactions with mutualistic vectors.

Aim The formation of the Trans-Mexican Volcanic Belt (TMVB) played an important role in driving inter- and intraspecific diversification at high elevations. However, Pleistocene climate changes and ecological factors might also contribute to plant genetic structuring along the volcanic belt. Here, we analysed phylogeographical patterns of the parrot-mistletoe Psittacanthus calyculatus to determine the relative contribution of these different factors. Location Trans-Mexican Volcanic Belt. Methods Using nuclear and chloroplast DNA sequence data for 370 individuals, we investigate the genetic differentiation of 35 populations across the species range. We conducted phylogenetic, population and spatial genetic analyses of P. calyculatus sequences along with ecological niche modelling and Bayesian inference methods to gain insight into the structuring of genetic variation of these populations. Results Our analyses revealed population structure with three genetic groups corresponding to individuals from Oaxaca and those from the central-eastern and western TMVB regions. A significant genetic signal of demographic expansion, an east-to-west expansion predicted by species distribution modelling, and approximate Bayesian computation analyses strongly supported a scenario of habitat isolation and invasion of TMVB by P. calyculatus during the late-Pleistocene. Main conclusions The genetic differentiation of P. calyculatus may be explained by the combined effects of (1) geographical isolation linked to the effects of the glacial/interglacial cycles and environmental factors, driving genetic differentiation from congeners into more xeric vegetation and (2) the invasion of TMVB from east to west, suggesting a role for both colonization and glacial/interglacial cycles models.

PREMISE Mistletoes parasitize many hardwood and softwood tree species; however, they play key roles in forest ecosystems. Adult individuals of Psittacanthus schiedeanus take up water and xylem nutrients from both deciduous and evergreen host trees, suggesting the ability to modify its physiology according to the availability of host resources. Yet, there is little information regarding the effects of mistletoes on their host trees from the eophyll stage to reproductive phases of the parasite. METHODS Taking advantage of the fact that P. schiedeanus can reach sexual maturity in 1 year, we investigated its physiological performance during development on deciduous (Liquidambar styraciflua) and evergreen (Quercus germana) host trees in a cloud forest in eastern Mexico. Variables related to chlorophyll fluorescence, carbon assimilation, photosynthetic pigments, and nitrogen, phosphorus, and carbon contents of the parasite and non-infected and infected hosts were analyzed in a nursery experiment. RESULTS Mistletoe had lower water-use efficiency and higher transpiration rates than the host species did. Despite the fact that P. schiedeanus obtained resources from species with differing phenology and resource availability, the parasite steadily improved its CO2 assimilation, electron transport rate, and nutrient content from seedling establishment to adult life stages. Mistletoe decreased the photosynthetic reactions of carbon metabolism in the deciduous host, photosynthetic light reactions in the evergreen host, and nutritional status of both host species, mostly in the evergreen host. CONCLUSIONS The hypothesis that mistletoes adjust their physiology according to the availability of host resources could extend to the early growth of the parasite.

Historical geological events and climatic changes have played important roles in shaping population differentiation and distribution within species. In this study, we analysed the distribution, expansion and colonization patterns, and genetic differentiation among Psittacanthus rhynchanthus populations in Mesoamerica. Specifically, we determine the effects of major historical events and geographic barriers on population divergence using nuclear and chloroplast DNA sequence data and the impact of Pleistocene glacial cycles on the distribution dynamics of P. rhynchanthus using ecological niche modelling (ENM). Our results showed that P. rhynchanthus populations split into two lineages, one distributed on the Yucatan Peninsula and the second along the Pacific and Atlantic slopes and Honduras, approximately 1 million years ago. The two lineages were fragmented at the last interglacial according to ENM predictions and experienced postglacial range expansion during the Last Glacial Maximum. Analysis of climate differentiation and niche models showed that both lineages have different climatic preferences, where the climatic characteristics of the Yucatan populations are not fully represented in the rest of the distribution range of P. rhynchanthus. Additionally, our study suggests that Pleistocene expansion of suitable habitat, environmental segregation (ecological barrier between regions) and, perhaps host shifts, have acted as the isolation mechanisms between the two lineages. Our results provide new insight as to understanding the distribution and phylogeographic patterns and the possible mechanisms underlying intraspecific evolutionary relationships of plants in the Mesoamerican tropical lowlands.

Several models have been proposed to explain the evolution of leks, both in terms of direct or indirect fitness benefits, and in survival. According to kin selection theory, male skewed reproductive success leads unsuccessful males to join successful relatives to increase their inclusive fitness, because their genes would be transmitted indirectly to the next generation. Wedge-tailed Sabrewing (Campylopterus curvipennis) is a hummingbird species whose males congregate at leks, in which spatially clustered males sing a particular song with marked differences among neighboring males (song neighborhoods). The maintenance of song neighborhoods presumably depends on juvenile newcomers copying the song type of their neighbors when they establish within a lek, and their acceptance could be more likely if a relative has already settled down in a territory, which in turn could offer fitness benefits explained by kin selection theory. To investigate the potential for kin selection in this species, we genotyped 126 hummingbirds at 10 microsatellite loci and estimated pairwise relatedness among males at 6 leks and in 4 song neighborhoods within 1 focal lek. Within leks, most males were unrelated and only a few were relatives. Moreover, even though relatedness within leks was higher than between leks, it was not higher than 0, which is likely due to isolation by distance. Our results do not support the idea of kin selection as an important force acting on the formation of leks in this species. Additionally, we found no evidence for kin clustering within song neighborhoods, suggesting that juveniles attempting to settle in a lek have to learn the song of the neighborhood (regardless of their kinship) to gain access to territories.

The phylogenetic relationships among members of the Neotropical clade of Miliuseae were inferred using Bayesian inference, maximum likelihood, and parsimony on a dataset of six plastid regions (ndhF, matK, psbA-trnH, rbcL, rps16-trnQ, and trnL-F). The phylogenetic hypothesis obtained indicate that the Neotropical clade of Miliuseae is a monophyletic group, composed of two distinct lineages: the first comprises the genera Sapranthus and Tridimeris, and the second is composed of Desmopsis, Stenanona, and two potentially new taxa, which together form the Desmopsis-Stenanona clade. However, the relationships within the Desmopsis-Stenanona clade are not fully resolved; the phylogenetic results indicate that Desmopsis and Stenanona, as currently circumscribed, are not monophyletic. The morphological characteristics that distinguish each genus and potential synapomorphies are discussed. We conclude that the observed variation in floral and fruit characteristics among the members of the Desmopsis-Stenano...

Mistletoe infection between conspecific and interspecific hosts can be restricted by seed dispersal, host-mistletoe compatibility and abiotic factors, yet no studies have linked mistletoe infection patterns and pollination together for understanding mistletoe distribution at a local scale. Psittacanthus calyculatus (Loranthaceae) is a hemiparasitic plant with a broad host range across its geographic distribution. The potential for local host adaptation has been shown using cross-inoculation experiments, in which plants of mistletoe seeds collected from a given host are more likely to survive when they are inoculated on conspecific host trees compared with those inoculated on other host provenances. Here we evaluate host adaptation by describing the local patterns of infection (prevalence and intensity) of P. calyculatus mistletoes on three native host tree species (Alnus acuminata, Quercus crassipes, Salix bonplandiana) and one introduced species (Populus alba) and carried out cross-pollination experiments to examine how pollination affects infection patterns of different host species. Mistletoe infection prevalence (proportion of infection) and infection intensity (mean number of mistletoes per tree) were in general disproportional with respect to the availability of native host tree species but higher to that of non-native host tree species. Cross-pollination experiments showed higher mating success on the native host tree species, suggesting higher local adaptation to specially Q. crassipes. The observed spatial distribution of host tree species and mistletoe infection along with the non-random mating could contribute to local genetic structuring of mistletoe populations.

Premise of research. Pollination syndromes are suites of correlated characters that reflect selection by most frequent and effective pollinators. However, the floral phenotypes of some angiosperm species combine traits from different pollination syndromes. The aim of this study was to assess the correspondence between floral traits and floral visitors, considering the breeding systems of two co-occurring Drymonia species with mixed floral phenotypes.Methodology. We assessed floral morphology, nectar production patterns, frequency of floral visitation, breeding systems, and natural fruit set in Drymonia strigosa and Drymonia oinochrophylla species at Los Tuxtlas, Veracruz, Mexico, during 2011–2014. We also conducted a field test of reproductive assurance in D. strigosa, the only species with a high potential for autonomous self-pollination.Pivotal results. In D. strigosa, morphology and nectar production patterns correspond to the ornithophilous syndrome; however, anthers have poricidal dehiscence, a trait...

By integrating mitochondrial DNA (mtDNA), microsatellites and ecological niche modelling (ENM), we investigated the phylogeography of Mexican populations of the common bush-tanager Chlorospingus ophthalmicus to examine the relative role of geographical and ecological features, as well as Pleistocene climatic oscillations in driving the diversification. We sequenced mtDNA of individuals collected throughout the species range in Mexico and genotyped them at seven microsatellite loci. Phylogeographic, population genetics and coalescent methods were used to assess patterns of genetic structure, gene flow and demographic history. ENM was used to infer contractions and expansions at different time periods as well as differences in climatic conditions among lineages. The retrieved mitochondrial and microsatellite groups correspond with the fragmented cloud forest distribution in mountain ranges and morphotectonic provinces. Differing climatic conditions between mountain ranges were detected, and palaeodistribution modelling as well as demographic history analyses, indicated recent population expansions throughout the Sierra Madre Oriental (SMO). The marked genetic structure of C. ophthalmicus was promoted by the presence of ecological and geographical barriers that restricted the movement of individuals among mountain ranges. The SMO was mainly affected by Pleistocene climatic oscillations, with the moist forests model best fitting the displayed genetic patterns of populations in this mountain range.