• Information on the genetic architecture of phenotypic traits is helpful for constructing and testing models of the ecoevolutionary dynamics of natural populations. For plant groups with long life ...cycles there is a lack of line cross experiments that can unravel the genetic architecture of loci underlying quantitative traits.
• To fill this gap, we propose the use of variation for phenotypic traits expressed in natural hybrid zones as an alternative approach. We used data from orchid hybrid zones and compared expected and observed patterns of phenotypic trait expression in different early-generation hybrid classes identified by molecular genetic markers.
• We found evidence of additivity, dominance, and epistatic interactions for different phenotypic traits.
• We discuss the potential of this approach along with its limitations and suggest that it may represent a realistic way to gain an initial insight into the heritability and genomic architecture of traits in organismal groups with complex life history, such as orchids and many others.
Molecular ecologists increasingly require ‘universal’ genetic markers that can easily be transferred between species. The distribution of cross‐species transferability of nuclear microsatellite loci ...is highly uneven across taxa, being greater in animals and highly variable in flowering plants. The potential for successful cross‐species transfer appears highest in species with long generation times, mixed or outcrossing breeding systems, and where genome size in the target species is small compared to the source. We discuss the implications of these findings and close with an outlook on potential alternative sources of cross‐species transferable markers.
Generally, species with broad niches also show large range sizes. We investigated the relationship between hydrological niche breadth and geographic range size for Amazonian tree species seeking to ...understand the role of habitat specialization to Amazonian wetlands and upland forests on the current distribution of tree species. We obtained 571,092 valid occurrence points from GBIF and SpeciesLink to estimate the range size and the niche breadth of 76% of all known Amazonian tree species (5150 tree species). Hydrological niche breadth was measured on different unidimensional axes defined by (1) total annual precipitation; (2) precipitation seasonality; (3) actual evapotranspiration; and (4) water table depth. Geographic range sizes were estimated using alpha‐hull adjustments. General linear models were used to relate niche breadth to range size while contrasting tree species occurring and not occurring in wetlands. The hydrological niche breadth of Amazonian tree species varied mostly along the water table depth axis. The average range size for an Amazonian tree species was 751,000 km2 (median of 154,000 km2 and standard deviation of 1,550,000 km2). Niche breadth–range size relationships for Amazonian tree species were positive for all models, and the explanatory power of the models improved when including whether a species occurred in wetlands or in terrestrial uplands. Wetland species had steeper positive slopes for the niche breadth–range size relationship, and consistently larger range sizes for a given niche breadth. Amazonian tree species varied strongly in hydrological niche breadth and range size, but most species had narrow niche breadths and range sizes. Our results suggest that the South American riverscape may have been acting as a corridor for species dispersal in the Neotropical lowlands.
The general ecological pattern for a positive range size‐niche breadth association holds for Amazonian tree species. Furthermore, those wetland‐adapted tree species have broader niche breadth and large range sizes compared with tree species only occurring in upland forests.
The South American Dry Diagonal, also called the Diagonal of Open Formations, is a large region of seasonally dry vegetation extending from northeastern Brazil to northern Argentina, comprising the ...Caatinga, Cerrado, and Chaco subregions. A growing body of phylogeography literature has determined that a complex history of climatic changes coupled with more ancient geological events has produced a diverse and endemic‐rich Dry Diagonal biota. However, the exact drivers are still under investigation, and their relative strengths and effects are controversial. Pleistocene climatic fluctuations structured lineages via vegetation shifts, refugium formation, and corridors between the Amazon and Atlantic forests. In some taxa, older geological events, such as the reconfiguration of the São Francisco River, uplift of the Central Brazilian Plateau, or the Miocene inundation of the Chaco by marine incursions, were more important. Here, we review the Dry Diagonal phylogeography literature, discussing each hypothesized driver of diversification and assessing degree of support. Few studies statistically test these hypotheses, with most support drawn from associating encountered phylogeographic patterns such as population structure with the timing of ancient geoclimatic events. Across statistical studies, most hypotheses are well supported, with the exception of the Pleistocene Arc Hypothesis. However, taxonomic and regional biases persist, such as a proportional overabundance of herpetofauna studies, and the under‐representation of Chaco studies. Overall, both Pleistocene climate change and Neogene geological events shaped the evolution of the Dry Diagonal biota, though the precise effects are regionally and taxonomically varied. We encourage further use of model‐based analyses to test evolutionary scenarios, as well as interdisciplinary collaborations to progress the field beyond its current focus on the traditional set of geoclimatic hypotheses.
Resumo
A Diagonal de Formações Abertas da América do Sul, também chamada de Diagonal Seca é uma grande região de vegetação sazonalmente seca que se estende do Nordeste do Brasil até o Norte da Argentina, composta pelas subregiões Caatinga, Cerrado e Chaco. Uma crescente literatura em filogeografia tem demonstrado que a diversa e endêmica biota Diagonal de Formações Abertas é produto de uma história complexa de mudanças climáticas, em conjunto com eventos geológicos mais antigos. Entretanto, os fatores específicos que geram essa diversidade e endemismo continuam sendo investigados, e há controvérsias em relação à importância relativa de cada um deles. Flutuações climáticas durante o Pleistoceno estruturaram linhagens através de mudanças na vegetação, formação de refúgios, e corredores entre a Floresta Amazônica e Mata Atlântica. Para alguns grupos taxonômicos, eventos geológicos durante o Neogeno, tal como a mudança no curso do São Francisco, o soerguimento do Planalto Central no Brasil, ou eventos durante o Mioceneo como a inundação do Chaco devido a incursões marinhas, foram mais importantes. No presente trabalho, nós revisamos a literatura sobre filogeografia na Diagonal de Formações Abertas, levantamos as hipóteses de diversificação sugeridas, e avaliamos seu grau de suporte. Poucos estudos testaram hipóteses estatisticamente, com maior parte do suporte atribuído aos padrões filogeográficos encontrados. Dentre os estudos que usaram uma abordagem estatística, a maioria das hipóteses são bem suportadas, exceto a hipótese dos arcos Pleistocênicos. Entretanto, vieses taxonômicos e regionais persistem, tal como a relativa prevalência de estudos herpetológicos e a falta de estudos sobre o Chaco. De forma geral, tanto as mudanças climáticas no Pleistoceno, quanto mudanças geológicas no Neogeno moldaram a evolução da Diagonal de Formações Abertas, apesar do efeito exato de cada um desses fatores variar dependendo da região e grupo taxonômico. Nós recomendamos o uso de análises baseadas em teste de modelos para testar cenários evolutivos, assim como colaborações interdisciplinares incluindo biólogos, geólogos e climatólogos para expandir o campo de estudo para além do seu atual foco atrelado às tradicionais hipóteses geoclimáticas mencionadas acima.
Mountains are renowned for their bountiful biodiversity. Explanations on the origin of such abundant life are usually regarded to their orogenic history. However, ancient mountain systems with ...geological stability also exhibit astounding levels of number of species and endemism, as illustrated by the Brazilian Quartzitic Mountains (BQM) in Eastern South America. Thus, cycles of climatic changes over the last couple million years are usually assumed to play an important role in the origin of mountainous biota. These climatic oscillations potentially isolated and reconnected adjacent populations, a phenomenon known as flickering connectivity, accelerating speciation events due to range fragmentation, dispersion, secondary contact, and hybridization. To evaluate the role of the climatic fluctuations on the diversification of the BQM biota, we estimated the ancient demography of distinct endemic species of animals and plants using hierarchical approximate Bayesian computation analysis and Ecological Niche Modelling. Additionally, we evaluated if climatic oscillations have driven a genetic spatial congruence in the genetic structure of codistributed species from the Espinhaço Range, one of the main BQM areas. Our results show that the majority of plant lineages underwent a synchronous expansion over the Last Glacial Maximum (LGM, c. 21 thousand years ago), although we could not obtain a clear demographic pattern for the animal lineages. We also obtained a signal of a congruent phylogeographic break between lineages endemic to the Espinhaço Range, suggesting how ancient climatic oscillations might have driven the evolutionary history of the Espinhaço's biota.
Abstract The effect of environmental gradients on the remarkable diversity of mountain‐associated plants and on the species' abilities to cope with climate change transcends species‐specific ...strategies. For instance, our understanding of the impact of thermal gradients on ecological divergences in populations of widely distributed species is limited, although it could provide important insights regarding species' response to climate change. Here, we investigated whether populations of an endemic species broadly distributed across an elevation gradient employ unique or multiple divergent ecological strategies according to specific environmental conditions. We hypothesised that populations employ distinct strategies, producing a tolerance‐avoidance trade‐off related to the thermal conditions they experience across elevations. We conducted our research with 125 individuals of Pitcairnia flammea (Bromeliaceae) sampled from various elevations spanning from sea level to ~2200 m and cultivated under the same conditions. To assess specific ecological strategies of P. flammea populations across elevations, we examined leaf temperature, heat and cold tolerances, as well as other structural/morphological, optical, physiological and biochemical leaf traits. We majorly observed that water‐saving traits diminish as elevation increases while membrane fluidity, majorly associated with unsaturated and very‐long‐chain lipids, enhances. Low‐elevation individuals of P. flammea invest in water storage tissues, which likely prevent excessive water loss through the intense transpiration rates under warming periods. Conversely, high‐elevation plants exhibit increased membrane fluidity, a possible response to the stiffening induced by low temperature. Our results revealed a tolerance‐avoidance trade‐off related to thermal strategies of populations distributed across an elevation gradient. Low‐elevation plants avoid excessive leaf temperature by investing in water‐saving traits to maintain transpiration rates. High‐elevation individuals, in turn, tend to invest in membrane properties to tolerate thermal variations, particularly cold events. Our findings challenge the conventional notion that plants' vulnerability to warming depends on species‐specific thermal tolerance by showing diverse thermal strategies on populations across an elevation gradient. Read the free Plain Language Summary for this article on the Journal blog.
Resumo O efeito dos gradientes ambientais na grande diversidade de plantas associadas a montanhas transcende as estratégias específicas de cada espécie. Nosso entendimento sobre o impacto dos gradientes térmicos nas divergências ecológicas em populações de espécies amplamente distribuídas, por exemplo, é limitado, embora possa fornecer informações importantes sobre a resposta das espécies às mudanças climáticas. Aqui, investigamos se populações de uma espécie endêmica e amplamente distribuída em um gradiente altitudinal, empregam estratégias ecológicas únicas ou múltiplas de acordo com condições ambientais específicas. Nossa hipótese é que as populações empregam estratégias que resultam em um equilíbrio entre tolerância e evitação relacionado às condições térmicas que experimentam em diferentes altitudes. Analisamos 125 indivíduos de Pitcairnia flammea (Bromeliaceae) amostrados em diversas altitudes, desde o nível do mar até cerca de 2.200 metros, e cultivados nas mesmas condições. Para avaliar as estratégias ecológicas específicas das populações de P. flammea , examinamos temperatura foliar, tolerâncias ao calor e ao frio, além de outros traços foliares estruturais/morfológicos, óticos, fisiológicos e bioquímicos. Vimos que características de economia de água diminuem à medida que a altitude aumenta, enquanto a fluidez da membrana, associada principalmente a lipídios insaturados e de cadeia muito longa, aumenta. Indivíduos de baixa altitude investem em tecidos de armazenamento de água, provavelmente prevenindo a perda excessiva de água durante períodos de aquecimento e com taxas intensas de transpiração. Por outro lado, plantas de altas altitudes possuem maior fluidez de membrana, uma possível resposta ao enrijecimento induzido por baixas temperaturas. Nossos resultados revelaram um equilíbrio entre tolerância e evitação relacionado às estratégias térmicas de populações distribuídas ao longo de um gradiente de altitude. Plantas de baixa altitude evitam temperaturas foliares excessivas investindo em características de economia de água para manter as taxas de transpiração. Indivíduos de alta altitude, por sua vez, tendem a investir em membranas que toleram variações térmicas, especialmente eventos frios. Nossas descobertas desafiam a noção convencional de que a vulnerabilidade das plantas ao aquecimento depende da tolerância térmica específica da espécie, mostrando estratégias térmicas diversas em populações ao longo de um gradiente de altitude.
PREMISE OF THE STUDY:
The yellow‐flowered Aechmea subgenus Ortgiesia (yfAsO) (Bromeliaceae) is a group of seven morphologically similar bromeliads found mostly in the southern Brazilian Atlantic ...rainforest. The recent origin of this group probably contributes to its taxonomic complexity. The aims of this study were to investigate the levels of genetic diversity and structure at the population and species levels, to gain insight into the processes behind the diversification of the group, and to contribute to the establishment of species boundaries.
METHODS:
We sequenced two noncoding regions of the chloroplast genome (rpl32‐trnL and rps16‐trnK) and the nuclear phyC gene in 204 and 153 individuals, respectively, representing the seven species of the group. Phylogeographical and population genetics approaches were used.
KEY RESULTS:
Three of the seven yfAsO showed some degree of genetic differentiation among species. Divergence time for the group was dated to around 4 million years ago. Areas of conservation value were identified, and a scenario of multiple refugia in the southern Brazilian Atlantic rainforest during the Pleistocene climatic oscillations is suggested.
CONCLUSIONS:
We hypothesized that incomplete lineage sorting and localized hybridization events are responsible for the low levels of genetic differentiation and the taxonomic complexity observed among and within the seven yfAsO species. Further studies on Aechmea comata and Aechmea kertesziae will be necessary to clarify the boundary between these two species. Most of the populations sampled showed high genetic diversity and/or unique haplotypes; they should be prioritized for conservation purposes.
Aim
Ancient climatic fluctuations are invoked as the main driving force that generates the astonishing biodiversity in ancient mountains. As a result, endemism and spatial turnover are usually high ...and few species are widespread amongst entire mountain ranges, precluding the understanding of origins of macroevolutionary patterns. Here, we used a species endemic to, but widespread in, one of the most species‐rich ancient mountains in the globe to test how environmental changes acted on and how their macroevolutionary patterns were shaped.
Location
Espinhaço Range, Eastern Brazil.
Taxon
Vriesea oligantha species complex (Bromeliaceae).
Methods
We compiled data for plastidial regions and nuclear microsatellites to assess genetic diversity, population structure, migration rates and phylogenetic relationships. Using temperature and precipitation variables, we modelled suitable areas for the present and the past, estimating corridors between isolated populations. We also implemented Bayesian demographic analyses to estimate ancient populations dynamics. Finally, we tested if population structure is driven by isolation by environment or by distance using a Bayesian modelling approach.
Results
Our results showed that the intraspecific divergence events of V. oligantha are older than those associated with the latest Pleistocene climatic oscillations, supporting the view that Quaternary climatic fluctuations are key components for understanding its population differentiation processes. Species distribution modelling estimated corridors between populations in the past, as also shown in the demographic analyses, depicting a major spatial reorganization during colder climates. Besides, the high genetic structure estimated results from both models of isolation by distance and by environment.
Main conclusions
V. oligantha is a remarkable model to test the effects of climatic oscillations over the biological community, since this species originated in the early‐Pleistocene, prevailing over several cycles of climatic fluctuations until today. The estimated demographic dynamics of V. oligantha agrees with the species‐pump mechanism, suggesting it as the main cause of speciation within the Espinhaço Range. Moreover, the phylogeographic patterns of V. oligantha reflect previously recognised spatial and temporal macroevolutionary patterns in the Espinhaço Range, providing insights into how microevolutionary processes may have given rise to this astonishing mountain biodiversity.
Aim
The centre‐periphery hypothesis (CPH) explains the decline of species abundance towards range limits and how this is driven by increasing ecological marginality. So far, most studies testing the ...CPH have focused on abiotic factors contributing to marginality, while the role of biotic interactions in limiting species distribution has been neglected. Here, we investigate both drivers' roles in restricting an orchid's range along a broad environmental gradient.
Location
Atlantic Forest and Pampas grasslands (south and southeastern Brazil).
Taxa
Sand dune orchid Epidendrum fulgens (Orchidaceae).
Methods
We integrated empirical data on geographical distribution, pollinator richness and genetic diversity along the entire range of the species to investigate whether range limits match niche limits and whether habitat suitability declines towards low‐ and high‐latitude species ranges. We performed niche models to predict niche limits and used polynomial and linear regression models to investigate the associations between ecological niche and species range as well as to test the relationship between genetic‐derived metrics and the geographical and ecological distances.
Results
Ecological conditions become more marginal towards the edges of the E. fulgens range, with an abrupt variation in precipitation. While pollinator richness increases habitat suitability of E. fulgens in the low‐latitude edge range, climate has primarily shaped the species' high‐latitude limit. Genetic diversity within populations decreases, while genetic differentiation increases towards both margins, although with a more consistent pattern for the low‐latitudinal component.
Main Conclusions
This study corroborates the predictions of CPH regarding ecological and genetic patterns of variation in space and highlights distinct factors limiting geographical distribution at the opposite margins of a latitudinal and narrowly distributed species. This improves our understanding on how biotic and abiotic variables limit species distribution ranges along latitudinal gradients in an extremely diverse and vulnerable tropical ecosystem, with potential for informing conservation practices.
Phylogeographic studies have merged different disciplines to explain speciation processes at both spatial and time scales. Although the number of phylogeographic extant studies has increased almost ...exponentially, few have been conducted in tropical countries, especially using plants. Plants are interesting models for such studies because their responses to different habitat conditions are reflected directly in the size and distribution of populations, enabling direct tests of alternative demographic scenarios. Here, we review phylogeographic studies using plant species occurring in different vegetation domains within Brazil, which has the greatest number of plant species in the world. Based on a detailed examination of 41 published articles, we synthesized the current knowledge and discussed the main processes driving the high levels of plant diversity within Brazilian domains. General patterns of diversification could be inferred due to the number of species studied, especially in the Cerrado and Atlantic Forest, the most intensively studied domains (34.1% and 17.1% of the studies, respectively). Distinct vegetation types within both biomes were affected differently by the Pleistocene climatic oscillations. Edaphic conditions and geographical barriers (rivers and mountains) have also influenced the phylogeographical patterns of plants species from Amazonia and the Atlantic Forest. Other Brazilian domains, such as the Caatinga, Pantanal, and Pampas, have been studied to a lesser extent and no common phylogeographic pattern across species could be inferred. Issues regarding past connections between distinct domains also remain unclear, including those affecting the two main forest domains in South America. Future research on plant species will fill these information gaps, improving our understanding of the complex diversification processes affecting the South American biota.
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