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Species limits, geographical distribution and genetic diversity in Johannesteijsmannia (Arecaceae)
Abstract
Four species are recognized in the understorey palm genus Johannesteijsmannia (Arecaceae), all of which occur in close geographical proximity in the Malay Peninsula. We hypothesize that overlapping distributions are maintained by a lack of gene flow among species and that segregation along morphological trait or environmental axes confers ecological divergence and, hence, defines species limits. Although some species have sympatric distributions, differentiation was detected among species in morphological and genetic data, corroborating current species delimitation. Differences in niche breadth were not found to explain the overlapping distribution and co-existence of Johannesteijsmannia spp. Four species formed over the last 3 Mya, showing that diversity accumulated within a short time frame and wide range expansion has not occurred, potentially due to a lack of time for dispersal or the evolution of traits to facilitate movement. An assessment of genetic diversity is presented and, as expected, the widest distribution in the genus harbours the highest genetic diversity.
... As suggested by Bacon et al. (2016), when two or more taxonomic related groups are widely separated geographically, they present a high degree of climate divergence. Thus, the climate differences may have played a fundamental role in the potential distribution of C. alba and C. prunifera. ...
Climate changes are one of the main factors that affect palm trees distribution in the tropics. Among the palm trees with social, economic, and ecological relevance, we highlight the native species, Copernicia alba Morong ex Morong and Britton and Copernicia prunifera (Miller) H. E Moore. An important strategy for protecting biodiversity is to identity the climate areas that will be suitable for future habitats of the species. In this sense, we used the ecological niche models (ENMs) to predict the suitable climate areas for the potential occurrence of C. alba and C. prunifera palm trees in current and future scenarios, RCP 4.5 (optimistic) and 8.5 (pessimistic), besides to evaluate these species vulnerability facing the climate changes. Our results predicted the C. prunifera habitat would continue to increase over the past years. In the RCP 8.5 scenario, the climate model projected an increase of 23.88% for the C. prunifera population between 2050 and 2070. Also, our results can be used for the application and the establishment of commercial C. prunifera plantations. By contrast, the predicted habitat of C. alba will decrease 22.2% between 2050 and 2070, according to the RCP 8.5 scenario. For both C. prunifera and C. alba species, we observed a low percentage of the potential distribution in protected areas for future scenarios. Therefore, we suggest the creation and maintenance of extensive forestry Protected Areas (PAs) with ecological corridors and the construction of germplasm banks to manage and conserve these two important palm tree species.
... The palm family was recently advocated as a model group to understand the evolution of tropical rain forests (Baker and Couvreur, 2013) and numerous studies have investigated their phylogenetic relationships and systematics (Uhl and Dransfield, 1987;Baker et al., 1999;Dransfield et al., 2008;Baker and Dransfield, 2016). However, given the remarkably low rate of molecular evolution observed in palms (Wilson et al., 1990), phylogenetic studies at different taxonomic levels within the Arecaceae based on a few plastid or nuclear genes generally result in poorly resolved phylogenetic trees, especially at the species level (Roncal et al., 2005(Roncal et al., , 2008Cuenca et al., 2008;Baker et al., 2011;Bacon et al., 2012aBacon et al., , 2016aBacon et al., ,b, 2017Meerow et al., 2015;Sanín et al., 2016). ...
The tribe Geonomateae is a widely distributed group of 103 species of Neotropical palms which contains six ecologically important understory or subcanopy genera. Although it has been the focus of many studies, our understanding of the evolutionary history of this group, and in particular of the taxonomically complex genus Geonoma, is far from complete due to a lack of molecular data. Specifically, the previous Sanger sequencing-based studies used a few informative characters and partial sampling. To overcome these limitations, we used a recently developed Arecaceae-specific target capture bait set to undertake a phylogenomic analysis of the tribe Geonomateae. We sequenced 3,988 genomic regions for 85% of the species of the tribe, including 84% of the species of the largest genus, Geonoma. Phylogenetic relationships were inferred using both concatenation and coalescent methods. Overall, our phylogenetic tree is highly supported and congruent with taxonomic delimitations although several morphological taxa were revealed to be non-monophyletic. It is the first time that such a large genomic dataset is provided for an entire tribe within the Arecaceae. Our study lays the groundwork not only for detailed macro- and micro-evolutionary studies within the group, but also sets a workflow for understanding other species complexes across the tree of life.
In plant communities, genetic diversity among dominant species can not only affect the fitness of the population, but also interactions with concomitant species. Soil salinity is a common factor that influences plant growth in estuarine wetlands. However, few studies have tested whether their high genetic diversity will be beneficial for the resistance of plant populations to salinity and the presence of concomitant plants. Four different genotypes of Phragmites australis, a dominant species of the Yellow River Delta in China, were selected to construct populations with three different genotypic levels. These populations were planted either with or without concomitant species and were subjected to control or salinity treatments. At the end of treatments, growth variables of P. australis populations were measured. In response to soil salinity, the total biomass of 1-, 2-, and 4-genotype populations decreased by 35%, 24%, and 13%, respectively, indicating higher resistance of P. australis populations with high genetic diversity. Correspondingly, 2-, and 4-genotype populations showed higher biomass allocation to roots, which can maintain adequate water uptake for plants. The biomass accumulation of 1-genotype populations with concomitant plants was significantly lower compared with populations without concomitant plants; however, no significant difference was found for 4-genotype populations between both control and salinity treatments, suggesting their higher capacities when coexisting with concomitant species. However, the genotypic level of populations did not significantly affect their biomass accumulation. High genetic diversity is greatly beneficial for the resistance of P. australis populations to salinity and coexistence with other plants. This information should be considered in the construction or restoration of this species in estuarine wetlands.
Comparative studies can provide powerful insights into processes that affect population divergence and thereby help to elucidate the mechanisms by which contemporary populations may respond to environmental change. Furthermore, approaches such as genotyping by sequencing (GBS) provide unprecedented power for resolving genetic differences among species and populations. We therefore used GBS to provide a genomewide perspective on the comparative population structure of two palm genera, Washingtonia and Brahea, on the Baja California peninsula, a region of high landscape and ecological complexity. First, we used phylogenetic analysis to address taxonomic uncertainties among five currently recognized species. We resolved three main clades, the first corresponding to W. robusta and W. filifera, the second to B. brandegeei and B. armata, and the third to B. edulis from Guadalupe Island. Focusing on the first two clades, we then delved deeper by investigating the underlying population structure. Striking differences were found, with GBS uncovering four distinct Washingtonia populations and identifying a suite of loci associated with temperature, consistent with ecologically mediated divergence. By contrast, individual mountain ranges could be resolved in Brahea and few loci were associated with environmental variables, implying a more prominent role of neutral divergence. Finally, evidence was found for long‐distance dispersal events in Washingtonia but not Brahea, in line with knowledge of the dispersal mechanisms of these palms including the possibility of human‐mediated dispersal. Overall, our study demonstrates the power of GBS together with a comparative approach to elucidate markedly different patterns of genomewide divergence mediated by multiple effectors.
Summary' I. 'Introduction' II. 'A brief history of hypotheses' III. 'Age of TRF biome and lineages' IV. 'Frequency of immigration from other biomes' V. 'Speciation and extinction' VI. 'Ecological limits' VII. 'Key methodological challenges' VIII. 'Perspectives' IX. 'Conclusions' 'Acknowledgements' References Tropical rainforest (TRF) is the most species-rich terrestrial biome on Earth, harbouring just under half of the world's plant species in c. 7% of the land surface. Phylogenetic trees provide important insights into mechanisms underpinning TRF hyperdiversity that are complementary to those obtained from the fossil record. Phylogenetic studies of TRF plant diversity have mainly focused on whether this biome is an evolutionary ‘cradle’ or ‘museum’, emphasizing speciation and extinction rates. However, other explanations, such as biome age, immigration and ecological limits, must also be considered. We present a conceptual framework for addressing the drivers of TRF diversity, and review plant studies that have tested them with phylogenetic data. Although surprisingly few in number, these studies point to old age of TRF, low extinction and high speciation rates as credible drivers of TRF hyperdiversity. There is less evidence for immigration and ecological limits, but these cannot be dismissed owing to the limited number of studies. Rapid methodological developments in DNA sequencing, macroevolutionary analysis and the integration of phylogenetics with other disciplines may improve our grasp of TRF hyperdiversity in the future. However, such advances are critically dependent on fundamental systematic research, yielding numerous, additional, well-sampled phylogenies of TRF lineages.
The floral biology and flower visitors of the tropical palms Johannesteijsmannia altifrons, J. magnifica and J. perakensis were investigated. We combined the data from this study with published data of J. lanceolata to give an overview of the reproductive biology and pollination system of the genus. Anthesis peaks from 0500–1100 hrs when the inflorescences are visited mainly by flies, beetles and stingless bees (Trigona), the last are potential pollinators. The breeding system is facultative selfing, indicating the ability of the species to reproduce in the absence of pollinators or in isolation.
To understand the driving factors behind the specificity amongst plant visitors and potential pollinators, we identified Mystrops spp. from eight palm species representative of each of the major clades of Wettinia (Arecaceae). We collected 31 palm inflorescences of at least three individuals per species from three different regions of across the distribution of the palms (Colombian Andes, Amazon and Choco). Sixty thousand visiting insect individuals were collected, 53% of which correspond to 17 different Mystrops morphospecies. The average number of pollinator species was highest in W. fascicularis (five species) and lowest in W. drudei (one species). We found high specificity between the Mystrops assemblages and Wettinia spp. and, in general terms, one primary visitor per Wettinia sp. These results confirm previous reports of a strong mutualistic relationship between Arecaceae and Mystrops. Using inference of environmental niches, we found Wettinia spp. to be segregated along their distribution on climatic gradients. Finally, we found that climate has an important role in shaping pollinator species turnover, even after controlling for spatial distance, and that phylogenetic relatedness also has a positive effect on turnover of Mystrops spp.
The evolution of a mechanism for attaining reproductive isolation between two diverging populations is a key step in the speciation process. We studied phenotypic variation, genetic differentiation, spatial distribution and reproductive ecology in two sympatric forms of the understorey palm Geonoma macrostachys in lowland tropical rainforest in Amazonian Ecuador. The two forms were morphologically and genetically distinct and differed in habitat preference, with one form being confined to moist flood plain habitats and the other occurring in terra firme and flood plain. Pollen transfer between the two forms was limited, but not totally prevented, by differences in flowering time, with flowers of the small form opening 2-3 h earlier than those of the large form. Differences in floral scent probably reduce the number of shared pollinators. A crossing experiment showed that pistillate flowers of either form produced fruit with pollen from the other form. We conclude that flowering biology may be a key factor in causing reproductive isolation between these closely related sympatric taxa.
It is now recognized that speciation can proceed even when divergent natural selection is opposed by gene flow. Understanding the extent to which environmental gradients and geographical distance can limit gene flow within species can shed light on the relative roles of selection and dispersal limitation during the early stages of population divergence and speciation. On the remote Lord Howe Island (Australia), ecological speciation with gene flow is thought to have taken place in several plant genera. The aim of this study was to establish the contributions of isolation by environment (IBE) and isolation by community (IBC) to the genetic structure of 19 plant species, from a number of distantly related families, which have been subjected to similar environmental pressures over comparable time scales. We applied an individual-based, multivariate, model averaging approach to quantify IBE and IBC, while controlling for isolation by distance (IBD). Our analyses demonstrated that all species experienced some degree of ecologically driven isolation, whereas only 12 of 19 species were subjected to IBD. The prevalence of IBE within these plant species indicates that divergent selection in plants frequently produces local adaptation and supports hypotheses that ecological divergence can drive speciation in sympatry.
Gene flow within and between species is a fundamental process shaping the evolutionary history of taxa. However, the extent of hybridization and reinforcement is little documented in the tropics. Here we explore the pattern of gene flow between three sister species from the herbaceous genus Marantochloa (Marantaceae), sympatrically distributed in the understorey of the African rainforest, using data from the chloroplast and nuclear genomes (DNA sequences and AFLP). We found highly contrasting patterns: while there was no evidence of gene flow between M. congensis and M. monophylla, species identity between M. monophylla and M. incertifolia was maintained despite considerable gene flow. We hypothesize that M. incertifolia originated from an ancient hybridization event between M. congensis and M. monophylla, considering the current absence of hybridization between the two assumed parent species, the rare presence of shared haplotypes between all three species and the high percentage of haplotypes shared by M. incertifolia with each of the two parent species. This example is contrasted with two parapatrically distributed species from the same family in the genus Haumania forming a hybrid zone restricted to the area of overlap. This work illustrates the diversity of speciation/introgression patterns that can potentially occur in the flora of tropical Africa.
Background
The hypothesis that pollinators have been important drivers of angiosperm diversity dates back to Darwin, and remains an important research topic today. Mounting evidence indicates that pollinators have the potential to drive diversification at several different stages of the evolutionary process. Microevolutionary studies have provided evidence for pollinator-mediated floral adaptation, while macroevolutionary evidence supports a general pattern of pollinator-driven diversification of angiosperms. However, the overarching issue of whether, and how, shifts in pollination system drive plant speciation represents a critical gap in knowledge. Bridging this gap is crucial to fully understand whether pollinator-driven microevolution accounts for the observed macroevolutionary patterns. Testable predictions about pollinator-driven speciation can be derived from the theory of ecological speciation, according to which adaptation (microevolution) and speciation (macroevolution) are directly linked. This theory is a particularly suitable framework for evaluating evidence for the processes underlying shifts in pollination systems and their potential consequences for the evolution of reproductive isolation and speciation.
Scope
This Viewpoint paper focuses on evidence for the four components of ecological speciation in the context of plant-pollinator interactions, namely (1) the role of pollinators as selective agents, (2) floral trait divergence, including the evolution of ‘pollination ecotypes‘, (3) the geographical context of selection on floral traits, and (4) the role of pollinators in the evolution of reproductive isolation. This Viewpoint also serves as the introduction to a Special Issue on Pollinator-Driven Speciation in Plants. The 13 papers in this Special Issue range from microevolutionary studies of ecotypes to macroevolutionary studies of historical ecological shifts, and span a wide range of geographical areas and plant families. These studies further illustrate innovative experimental approaches, and they employ modern tools in genetics and floral trait quantification. Future advances to the field require better quantification of selection through male fitness and pollinator isolation, for instance by exploiting next-generation sequencing technologies. By combining these new tools with strategically chosen study systems, and smart experimental design, we predict that examples of pollinator-driven speciation will be among the most widespread and compelling of all cases of ecological speciation.
Background and AimsAdaptation to different pollinators has been hypothesized as one of the main factors promoting the formation of new species in the Cape region of South Africa. Other researchers favour alternative causes such as shifts in edaphic preferences. Using a phylogenetic framework and taking into consideration the biogeographical scenario explaining the distribution of the group as well as the distribution of pollinators, this study compares pollination strategies with substrate adaptations to develop hypotheses of the primary factors leading to speciation in Lapeirousia (Iridaceae), a genus of corm-bearing geophytes well represented in the Cape and presenting an important diversity of pollination syndromes and edaphic preferences.Methods
Phylogenetic relationships are reconstructed within Lapeirousia using nuclear and plastid DNA sequence data. State-of-the-art methods in biogeography, divergence time estimation, character optimization and diversification rate assessments are used to examine the evolution of pollination syndromes and substrate shifts in the history of the group. Based on the phylogenetic results, ecological factors are compared for nine sister species pairs in Lapeirousia.Key ResultsSeventeen pollinator shifts and ten changes in substrate types were inferred during the evolution of the genus Lapeirousia. Of the nine species pairs examined, all show divergence in pollination syndromes, while only four pairs present different substrate types.Conclusions
The available evidence points to a predominant influence of pollinator shifts over substrate types on the speciation process within Lapeirousia, contrary to previous studies that favoured a more important role for edaphic factors in these processes. This work also highlights the importance of biogeographical patterns in the study of pollination syndromes.
http://www.biomedcentral.com/1741-7007/11/48
The reproductive biology of the rare and endangered palm, J h n esteijsmannia lanceolata, was studied to provide basic but essential information that contributes to the conservation of the species. Floral phenology and visiting insects were observed in cultivated and w l populations. Pollen viability and stigma receptivitiy were tested for flowers of different ages. Thirty inflorescences were subjected to pollination experiments. Flowers of J. lanceolata were homogamous, with a thesis peaked from 0730 to 1100 hours. Pollen viability and stigma receptivity lasted one day. Small flies (Phoridae and Cecidomyiidae) and stingless bees (Trigona spp.) were the potential pollinators of the inflorescences. Flower abortion was high (> 90%) and seed set was very low (< 0.05%). The breeding system may be autogamy, geitonogamy or xenogamy. The species is self-compatible, indicating its ability to survive and persist in fragmented or isolated environment.
A total of 20 new localities were recorded for the genus Johannesteijsmannia since 1972, demonstrating that the genus is less restricted in its distribution in Malaysia than previously thought. Nevertheless, Johannesteijsmannia is regarded as threatened with J. lanceolata, J. magnifica and J. perakensis assessed as endangered and J. altifrons as vulnerable. Endangered status was given to endemic species with restricted occurrence and small population size found in less than five localities. Recommended conservation measures include the need to expand in situ protection for populations in vulnerable habitats, inclusion of the species into forest management plans, and establishment of a sustainable seed harvesting regime. We also suggest regular monitoring of populations situated along forest boundaries and initiation of long-term conservation biology research. Habitats at risk in Jerantut-Benta (for J. lanceolata), Serendah and Bukit Kinta Forest Reserves (for J. magnifica), and Perak, i.e.,
Bintang Hijau, Kledang-Saiong and Bubu Forest Reserves (for J. perakensis) should be given protected status and ex situ conservation should be implemented.
Phylogenetic analyses were performed on six genera and 46 species of the Neotropical palm tribe Geonomeae (subfamily Arecoideae) and outgroups composed of 14 species from the Arecoideae, two from the Ceroxyloideae, and one from the Phytelephantoideae. The analyses were based on two low copy nuclear DNA sequences from the genes encoding phosphoribulokinase and RNA polymerase II. The two data sets did not appear to conflict and were analyzed separately and in combination. Our results added support to the previously reported monophyly of the tribe. The basal node of the tribe was polytomous containing the genera Welfia and Pholidostachys and a clade consisting of the rest of the Geonomeae. Pholidostachys formed a monophyletic group. The currently accepted genera Calyptronoma and Calyptrogyne formed a well-supported clade with Calyptronoma resolved as paraphyletic to Calyptrogyne. Geonoma formed a strongly supported monophyletic group consisting of two main clades. Geonoma section Taenianthera was not monophyletic but a group of three high-elevation Geonoma species was resolved.
Among the hypotheses invoked to explain high species richness in tropical forests, the niche differentiation hypothesis has received observational and experimental support (Ashton 1969, Chesson 2000, Clark et al . 1999, Souza & Martins 2004, Svenning 2001, Terborgh & Mathews 1999). Habitat specialization with regard to edaphic factors and topography has been observed in several plant groups including trees, lianas, shrubs, ferns and palms (Clark et al . 1999, Ibarra-Manriquez & Martinez-Ramos 2002, Svenning 1999, Tuomisto & Ruokolainen 1993). Treefall gaps and light gradients have also been found to be important ecological factors affecting plant distribution and niche differentiation in the understory (Chazdon 1986, Poorter & Arets 2003, Terborgh & Mathews 1999). It is suggested that such habitat heterogeneity may not only maintain biodiversity but also may lead to the origin of new species through the process of parapatric speciation (Gentry 1989, Haffer 1997, Patton & Smith 1992).
Aim Concerns over how global change will influence species distributions, in conjunction with increased emphasis on understanding niche dynamics in evolutionary and community contexts, highlight the growing need for robust methods to quantify niche differences between or within taxa. We propose a statistical framework to describe and compare environmental niches from occurrence and spatial environmental data.
Location Europe, North America and South America.
Methods The framework applies kernel smoothers to densities of species occurrence in gridded environmental space to calculate metrics of niche overlap and test hypotheses regarding niche conservatism. We use this framework and simulated species with pre-defined distributions and amounts of niche overlap to evaluate several ordination and species distribution modelling techniques for quantifying niche overlap. We illustrate the approach with data on two well-studied invasive species.
Results We show that niche overlap can be accurately detected with the framework when variables driving the distributions are known. The method is robust to known and previously undocumented biases related to the dependence of species occurrences on the frequency of environmental conditions that occur across geographical space. The use of a kernel smoother makes the process of moving from geographical space to multivariate environmental space independent of both sampling effort and arbitrary choice of resolution in environmental space. However, the use of ordination and species distribution model techniques for selecting, combining and weighting variables on which niche overlap is calculated provide contrasting results.
Main conclusions The framework meets the increasing need for robust methods to quantify niche differences. It is appropriate for studying niche differences between species, subspecies or intra-specific lineages that differ in their geographical distributions. Alternatively, it can be used to measure the degree to which the environmental niche of a species or intra-specific lineage has changed over time.
We describe a model-based clustering method for using multilocus genotype data to infer population structure and assign individuals to populations. We assume a model in which there are K populations (where K may be unknown), each of which is characterized by a set of allele frequencies at each locus. Individuals in the sample are assigned (probabilistically) to populations, or jointly to two or more populations if their genotypes indicate that they are admixed. Our model does not assume a particular mutation process, and it can be applied to most of the commonly used genetic markers, provided that they are not closely linked. Applications of our method include demonstrating the presence of population structure, assigning individuals to populations, studying hybrid zones, and identifying migrants and admixed individuals. We show that the method can produce highly accurate assignments using modest numbers of loci—e.g., seven microsatellite loci in an example using genotype data from an endangered bird species. The software used for this article is available from http://www.stats.ox.ac.uk/~pritch/home.html.
Synechanthus, a genus of two species, is widely distributed from southern Mexico through Central America to the Pacific coast of Colombia and Ecuador Univariate, bivariate, and multivariate statistical methods, based on data taken from herbarium specimens, were used to examine morphological variation between and within species. The species are clearly distinguished based on qualitative variables, and means of most quantitative variables are significantly different between the two. Synechanthus warscewiczianus is distributed more or less continuously from Nicaragua to Ecuador. No variables are correlated with latitude, but three are correlated with elevation. In central Panama, small-sized plants occur on three isolated peaks. These can be separated from larger-sized plants with discriminant analysis, and two of the three small-sized populations can be separated from each other. The distribution of S. fibrosus, from Mexico to Costa Rica, encompasses three separate populations that can be distinguished from one another by discriminant analysis. No variables are correlated with elevation or latitude.
A method is presented for the rapid isolation of high molecular weight plant DNA (50,000 base pairs or more in length) which is free of contaminants which interfere with complete digestion by restriction endonucleases. The procedure yields total cellular DNA (i.e. nuclear, chloroplast, and mitochondrial DNA). The technique is ideal for the rapid isolation of small amounts of DNA from many different species and is also useful for large scale isolations.
The suitability of two easily available alternative diets, the house dust mite, Dermatophagoides farinae and Quercus spp. pollen, was evaluated for mass-rearing of Amblyseius californicus in order to improve the use of this predator in biological control programs. At 25°C and RH >80%, an intrinsic rate of increase (rm) of 0.143 day−1 was obtained on D. farinae, whereas the rm on pollen was 0.158 day−1. However, when the two food sources were used to feed colonies over a long period of time, better results were obtained with the house dust mite: after 20 days an initial population of 3 young pairs of A. californicus increased to 205 motile stages on D. farinae and to 49.5 on Quercus spp. pollen. Advantages of the use of D. farinae for mass-rearing of A. californicus are discussed.
A model is developed to predict evolution in a population which contains a variety of ecologically specialized phenotypes. Individuals of each phenotype are assumed to specialize on a specific region of a resource axis present in the environment. The model, incorporating density-dependent effects on the fitness of the various phenotypes, predicts the number of individuals of each phenotype through time for both asexually and sexually reproducing populations. The lizard species, Anolis roquet, illustrates the kind of population treated by the model. The resource axis is prey size; small lizards preferentially utilize small prey, while large lizards exploit large prey. Field data on this species are used to estimate some of the parameters of the model. The model shows that there is an optimum number of individuals of each phenotype for a given set of resources and a given regime of interphenotypic competition. If the population has this optimum distribution of individuals, then the fitnesses of all phenotyp...
The recovery of demographic history through phylogeographical analysis is critical for understanding microevolutionary processes and the spatial/temporal context of lineage divergence. Palaeodistribution modelling and the fossil record might provide the spatial context for statistical phylogeographical analyses, allowing the generation of independent palaeoscenarios of demographic history that can be tested using coalescent models. In this study we generated independent demographic scenarios to examine geographical barriers to gene flow in a Neotropical swamp palm, Mauritia flexuosa, and assessed how climatic changes during the Pleistocene influenced its geographical distribution and genetic diversity.
Palms (Arecaceae/Palmae) are a model group for evolutionary studies in the tropics. Family-wide data on taxonomy, phylogenetics and distribution are now available, but a general framework of palm evolution is still lacking. The overall aim of this study, published in two companion papers, is to seek evolutionary explanations for the geographical distribution of palm lineages and species diversity patterns at global and regional levels. In this first paper we undertake a detailed analysis of palm biogeography for all major lineages in a global context, comparing our results to the fossil record, molecular dating studies and previously established biogeographical hypotheses for the family.
Two semiarboreal skinks (Mabuya) are narrowly sympatric in the Kalahari desert, whereas two terrestrial species are broadly sympatric both with one another and with the semiarboreal species. We attempt to discern reasons for these differing distributional patterns. The narrow zone of sympatry of the semiarboreal species is partially congruent with zones of habitat change (rainfall and vegetation), suggesting that the narrow zone probably reflects adaptations of these species of geographic discontinuities of the physical environment. However, the near identity of niches (position on sandridges, microhabitats, body temperatures, times of activity, as well as types and sizes of prey) of the semiarboreal species relative to other species pairs also suggest that intense competition could restrict the zone of sympatry.
We studied vegetative and reproductive characters of 74 herbarium specimens of Licuala glabra Griff. (Palmae) collected from 22 localities throughout Peninsular Malaysia. To test the null hypothesis that there are no distinct groups within the species, cluster analysis (nearest neighbour), principal coordinates and principal components analyses were performed on the set of 43 qualitative and quantitative characters. The results obtained suggested that: (1) there are three infraspecific groups within the species, vizthe two published varieties glabra and selangorensis as well as a possible third novel taxon; (2) there is clustering of individuals corresponding to their geographic localities; (3) clusters generated using only reproductive characters indicate a biogeographic distribution of populations correlated with the mountain ranges in the peninsula.
Undisturbed ant faunas of islands in the Moluccas-Melanesian arc are for the most part "saturated," that is, approach a size that is correlated closely with the landmass of the island but only weakly with its geographic location (figure 1). In the Ponerinae and Cerapachyinae combined the saturation level can be expressed approximately as F=3A0.6, where F is the number of species in the fauna and A the area of the island in square miles. Interspecific competition, involving some degree of colonial warfare, plays a major role in the determination of the saturation curve. It deploys the distribution of some ant species into mosaic patterns and increases the diversification of local faunas. Perhaps because of the complex nature of the Melanesian fauna, differences between local faunas appear that give the subjective impression of randomness. Despite the action of species exclusion, the size of local faunas occurring within a set sample area increases with the total size of the island (figure 2). Water gaps br...
The area under the receiver operating characteristic (ROC) curve, known as the AUC, is currently considered to be the standard method to assess the accuracy of predictive distribution models. It avoids the supposed subjectivity in the threshold selection process, when continuous probability derived scores are converted to a binary presence-absence variable, by summarizing overall model performance over all possible thresholds. In this manuscript we review some of the features of this measure and bring into question its reliability as a comparative measure of accuracy between model results. We do not recommend using AUC for five reasons: (1) it ignores the predicted probability values and the goodness-of-fit of the model; (2) it summarises the test performance over regions of the ROC space in which one would rarely operate; (3) it weights omission and commission errors equally; (4) it does not give information about the spatial distribution of model errors; and, most importantly, (5) the total extent to which models are carried out highly influences the rate of well-predicted absences and the AUC scores.
The palm has a juvenile stage with entire leaves followed by a stage in which an aerial stem develops, up to a height of 13 m, and pinnate leaves are produced, which leave distinct scars on the stem. In the juveniles, successive leaf lengths increase by c1-4 cm and about 28 juvenile leaves are produced. Annual leaf production increased from c1.2 yr-1 in juveniles to c2.2 yr-1 in tall palms. Duration of the juvenile phase was 15-25 yr, while the oldest palm observed was c85 yr. Flowering began at 5 m stem height, after 40-60 yr, with one inflorescence in each leaf axil and 183±92 (s.d.) fruits on each infructescence. Mortality was estimated as 99.8-99.9% from the seed to juvenile stage, and 1.4-4% yr-1 in later stages. A mean generation time of 68 yr was calculated. About 23% of net production was used in reproduction during the reproductive period, or c13% of total net production of an old palm. -from Author
Broad-scale patterns of species diversity have received much attention in the literature, yet the mechanisms behind their formation may not explain species richness disparities across small spatial scales. Few taxa display high species diversity on either side of Wallace's Line and our understanding of the processes causing this biogeographical pattern remains limited, particularly in plant lineages. To understand the evolution of this biogeographical pattern, a time-calibrated molecular phylogeny of Livistoninae palms (Arecaceae) was used to infer the colonization history of the Sahul tectonic plate region and to test for disparities in diversification rates across taxa and across each side of Wallace's Line. Our analyses allowed us to examine how timing, migration history, and shifts in diversification rates have contributed to shape the biogeographical pattern observed in Livistoninae. We inferred that each of the three genera found in Sahul crossed Wallace's Line only once and relatively recently. In addition, at least two of the three dispersing genera underwent an elevation in their diversification rate leading to high species richness on each side of Wallacea. The correspondence of our results with Southeast Asian geologic and climatic history show how palms emerge as excellent models for understanding the historical formation of fine-scale biogeographic patterns in a phylogenetic framework.
The general conclusion of part I is that the theoretical correlation between representatives of a locus in gametes, uniting or otherwise, relative to one or another array of such representatives (F-statistics), gives a broader basis for comparison of population structures, including progress in fixation, than does the alternative concept: the probability of identity of such representatives by origin. One reason is that correlations vary from -1 to +1 while probabilities vary only from 0 to +1. The probability concept gives, however, a very useful supplementary interpretation where applicable. The relation of the basic set of F-statistics, FIT, FIS, FST, to variances within populations is discussed in part II and applications to diverse patterns of population structure are reviewed (the island model with or without selective differences, isolation by distance in continuous populations under balancing of local inbreeding and dispersion, uniformly distributed clusters under a similar balance, selective clines, breeds of livestock). In part III, these F-statistics are applied to systems of mating in populations of given small size, in which consanguine mating is either avoided as much as possible, or pursued as much as is possible without any disruption of the group. The apparently paradoxical result obtained by Kimura and Crow that heterozygosis declines more rapidly under the former than under the latter is discussed from the standpoint of these statistics. These systems have been found to agree in one respect, the ultimate proportion of recombinant lines in the race between fixation and recombination among lines starting from double heterozygotes.
Geology provides the basis for understanding distributions of faunas and floras in Southeast Asia but only via a complex interplay of plate movements, palaeogeography, ocean circulation and climate. Southeast Asia grew incrementally by the addition of continental fragments, mainly rifted from Australia, and added to the margins of Sundaland as a result of subduction. Sundaland was an almost permanent land area from the beginning of the Mesozoic. The addition of the continental fragments of Southwest Borneo and later East Java-West Sulawesi formed a much larger emergent land area by the Late Cretaceous that extended from Indochina to West Sulawesi. Subduction resumed at the Sundaland margin in the Eocene and this led to widespread rifting within Sundaland, and formed one of the most important barriers at its edge, the Makassar Straits. Australia began to collide with Southeast Asia about 25 million years ago, effectively closing the former deep ocean separating the two continents, and forming the region now known as Wallacea. Collision, volcanism, and subduction-related processes have led to rise of mountains but also formed new oceans within this complex region. Plate tectonic movements and collisions were intimately linked to changing topography, bathymetry and land/sea distributions which have in turn influenced oceanic circulation and climate. As the deep-water barrier between Australia and Southeast Asia was eliminated and mountains rose, deep marine basins also formed. Eustatic changes in sea level further contributed to a complex palaeogeography. The present gateway between the Pacific and Indian Oceans is the only low latitude oceanic passage between the world's oceans, and is an important influence on local and probably global climate. The gateway is likely to have been just as significant in the past. Understanding the geology, then palaeogeography, and then their oceanic and climatic consequences are vital steps on the way to interpreting present distributions of plants and animals.
Synechanthus, a genus of two species, is widely distributed from southern Mexico through Central America to the Pacific coast of Colombia and Ecuador. Univariate, bivariate, and multivariate statistical methods, based on data taken from herbarium specimens, were used to examine morphological variation between and within species. The species are clearly distinguished based on qualitative variables, and means of most quantitative variables are significantly different between the two. Synechanthus warscewiczianus is distributed more or less continuously from Nicaragua to Ecuador. No variables are correlated with latitude, but three are correlated with elevation. In central Panama, small-sized plants occur on three isolated peaks. These can be separated from larger-sized plants with discriminant analysis, and two of the three small-sized populations can be separated from each other. The distribution of S. fibrosus, from Mexico to Costa Rica, encompasses three separate populations that can be distinguished from one another by discriminant analysis. No variables are correlated with elevation or latitude. Communicating Editor: Fred R. Barrie
A general coefficient measuring the similarity between two sampling units is defined. The matrix of similarities between all pairs of sample units is shown to be positive semidefinite (except possibly when there are missing values). This is important for the multidimensional Euclidean representation of the sample and also establishes some inequalities amongst the similarities relating three individuals. The definition is extended to cope with a hierarchy of characters.
Phenology, flowering biology, and pollination were studied for one year in four sympatric varieties of the polymorphic palm Geonoma cuneata in Ecuador. Flowering seasons of the three most common varieties were significantly staggered resulting in minimal temporal overlap. No marked differences were found with respect to flowering biology or pollination. The implication of these findings for explaining the complicated morphological variation pattern found in G. cuneata and similar species complexes is discussed.
This paper presents an investigation of the chemical composition of the floral scent of eight coflowering, sympatric taxa of Geonoma, a neotropical genus of understory palms with little or no variation in floral characteristics. The objective was to evaluate if floral scent might function as a reproductive isolation mechanism. Floral scent was collected with headspace techniques and the chemical composition analyzed and determined by gas chromatography–mass spectrometry. The eight studied taxa each had a characteristic, distinct floral scent composition, as revealed by grouping of individuals of each taxon together in a principal component analysis. As flower morphology and colors, as well as the diurnal flowering phenology, often vary little between sympatric, coflowering plants, other mechanisms to keep the species reproductively isolated are needed. It was concluded that variation in floral scent composition potentially is of importance to keep taxa of Geonoma reproductively isolated.
We studied vegetative and reproductive characters of 74 herbarium specimens of Licuala glabra Griff. (Palmae) collected from 22 localities throughout Peninsular Malaysia. To test the null hypothesis that there are no distinct groups within the species, cluster analysis (nearest neighbour), principal coordinates and principal components analyses were performed on the set of 43 qualitative and quantitative characters. The results obtained suggested that: (1) there are three infraspeciflc groups within the species, viz., the two published varieties glabra and selangorensis as well as a possible third novel taxon; (2) there is clustering of individuals corresponding to their geographic localities; (3) clusters generated using only reproductive characters indicate a biogeographic distribution of populations correlated with the mountain ranges in the peninsula.
Carpentaria acuminata occurs in monsoon rainforest and is endemic to the Northern Territory, Australia. The genetic diversity of C. acuminata populations was surveyed across the geographical range of the species using isozyme analysis. Genetic diversity within C. acuminata populations (HE = 0.143) was typical of rainforest species and woody angiosperms generally. Genetic diversity was not correlated with rainforest patch size. However, there was significant heterogeneity among populations (FST = 0.379), with infrequent effective gene flow among populations (Nm = 0.39). Genetic diversity was negatively correlated with increasing distance between neighbouring C. acuminata populations, but geographical distance was not a good predictor of genetic similarity. C. acuminata is a favoured food of mobile frugivores such as Torres Strait pigeons and flying foxes. The decreased diversity with decreasing density of populations indicated that seed dispersal by frugivores has been important for the maintenance of diversity in this species. Populations known to have originated on relatively young, Holocene landforms were not necessarily genetically depauperate. Gene flow by pollen is apparently limited because C. acuminata populations are significantly inbred regardless of genetic diversity (F = 0.641). The distribution and diversity of rare alleles, i.e. those occurring in few populations, is consistent with the theory of rainforest contraction during the Pleistocene.
A review is given of the role of traditional morphometrics in plant systematics. The three most commonly used tech-niques of data analysis – Cluster Analysis, Principal Component Analysis and Discriminant Analysis – are dis-cussed. The kinds of data that can be taken from palm specimens and the problems of using specimens as data sources are outlined. Published systematic studies of palms using traditional morphometrics are reviewed. More recent studies indicate that: hybrid zones between species may be common; infraspecific diversity is greater than previously suspected; there may be more than double the currently accepted number of species; and our current knowledge of morphological variation in palms is superficial. A procedure for scientific systematics is given, which incorporates traditional morphometric methods.