CURRENT PROJECT: HOLOCHROMEVOL.
My research interest is mainly focused in the evolution and diversification of flowering plants with special emphasis in genus Carex (Cyperaceae). Interestingly, with approximately 2,000 species worldwide, Carex is one of the largest angiosperm genus in the world. Our research aims to disentangle the causes behind this remarkable species richness. In order to unravel the evolutionary and diversification patterns of this genus, my colleagues and I perform studies of molecular phylogenetics and biogeographics, phylogeographics, cytogenetics, herbarium study, phylogenetic comparative analyses... to study geographic (high long-distance dispersal ability), ecological (high habitat disparity) and chromosomal (rapid evolution of its holocentric chromosomes; 2n = 12 - 124) speciation in Carex.
* JULY- 3-2014
NEW ACCEPTED PUBLICATION ABOUT PATTERNS OF CHROMOSOME EVOLUTION IN ANGIOSPERMS.
Determining phylogenetic relationships among very closely related species has remained a challenge for evolutionary biologists due to interlocus phylogenetic discordance and the difficulty of obtaining variable markers. Here, we used a Genotyping-by-Sequencing (GBS) approach to sample a reduced representation genomic data set and infer the phylogeny of seven closely related species in the genus Carex (Cyperaceae). Past attempts to reconstruct phylogenetic relationships among these species produced conflicting and poorly-supported results. We inferred a robust phylogeny based on >3,000 GBS loci and >1,300 SNPs (with a minimum sequence depth within individuals of 10) using maximum likelihood and Bayesian inference. We also tested for historical introgression using the D-statistic test. We compared these analyses with partitioned RAD analysis, which is designed to identify suboptimal trees reflecting secondary phylogenetic signal that may be obscured by the dominant signal in the data. Phylogenetic analyses yielded fully resolved trees with high support. We found two main clades, one grouping Carex scoparia populations and C. waponahkikensis, and a second clade grouping C. longii, C. vexans, C. suberecta and C. albolutescens. We detected marginal significant signals of introgression between C. scoparia and C. suberecta or C. albolutescens, and we rejected a hybrid origin hypothesis for C. waponahkikensis. Our results demonstrate the power of NGS data sets for resolving some of the most difficult phylogenetic challenges where traditional phylogenetic markers have failed.
MARCIAL ESCUDERO, DEREN A.R. EATON, MARLENE HAHN & ANDREW HIPP. IN PRESS. GENOTYPING-BY-SEQUENCING AS A TOOL TO INFER PHYLOGENY AND ANCESTRAL HYBRIDIZATION: A CASE STUDY IN CAREX (CYPERACEAE). MOLECULAR PHYLOGENETICS AND EVOLUTION, 000, 000-000.
NEW ACCEPTED PUBLICATION ABOUT PATTERNS OF CHROMOSOME EVOLUTION IN ANGIOSPERMS.
Chromosome evolution has been demonstrated to have profound effects on diversification rates and speciation in angiosperms. While polyploidy has predated some major radiations in plants, it has also been related to decreased diversification rates. There has been comparatively little attention to the evolutionary role of gains and losses of single chromosomes, which may or not entail changes in the DNA content (then called aneuploidy or dysploidy, respectively). In this study we investigate the role of chromosome number transitions and of possible associated genome size changes in angiosperm evolution. We model the tempo and mode of chromosome number evolution and its possible correlation with patterns of cladogenesis in 15 angiosperm clades. Inferred polyploid transitions are distributed more frequently towards recent times than single chromosome gains and losses. This is likely because the latter events do not entail changes in DNA content and are probably due to fission or fusion events (dysploidy), as revealed by an analysis of the relationship between genome size and chromosome number. Our results support the general pattern that recently originated polyploids fail to persist, and suggest that dysploidy may have comparatively longer-term persistence than polyploidy. Changes in chromosome number associated with dysploidy were typically observed across the phylogenies based on a chi-square analysis, consistent with these changes being neutral with respect to diversification.
MARCIAL ESCUDERO, SANTIAGO MARTIN-BRAVO, ITAY MAYROSE, MARIO FERNANDEZ-MAZUECOS, OMAR FIZ-PALACIOS, ANDREW HIPP, MANUEL PIMENTEL, PEDRO JIMENEZ-MEJIAS, VIRGINIA VALCARCEL, PABLO VARGAS & MODESTO LUCEÑO. IN PRESS. KARYOTYPIC CHANGES THROUGH DYSPLOIDY PERSIST LONGER OVER EVOLUTIONARY TIME THAN POLYPLOID CHANGES. PLOS ONE, 9, e58266. LINK. PDF.
* SEPTEMBER- 23-2013
NEW ACCEPTED PUBLICATION ABOUT PATTERNS OF SPECIES RICHNESS IN FAMILY CYPERACEAE.
Premise of the study. Understanding heterogeneity in species richness across the tree of life is a challenge in evolutionary biology. The sedge family Cyperaceae is classified into tribes that exhibit a roughly 200-fold range in species richness. The Cyperaceae present an excellent case study in the determinants of species richness within higher-level taxa. Methods. We used secondary calibration based on prior studies and fossils from a rush (Juncaceae) and five sedges to calibrate two previously published Cyperaceae phylogenies, then compared our results to previous molecular clock analyses. We used an information theoretic approach to identify shifts in lineage diversification rates and phylogenetic generalized least squares to fit alternative models of clade species richness. Key results. Our results suggest a late Cretaceous origin for Cyperaceae (76–89 My ago). The inferred 0.06 speciation events per My is comparable to overall diversification rates in the order Poales but faster than angiosperm background rates. A threefold increase in diversification rate at the base of the species-rich SDC+FAEC clade correlates with climatic changes during the Paleocene-Eocene boundary (ca. 55 Mya ago). The greater driver of among-clade variance in species richness, however, is clade age (simple R2 = 0.334, P = 0.0006). Conclusions. While shifts in diversification rates play a role in the generation of heterogeneous patterns of species richness, our study demonstrates that variance in clade age alone explains ca. 33% of among-clade variation in species diversity, which stands in contrast to the general pattern for angiosperms.
Background and Aims. The sedge genus Carex, the most diversified angiosperm genus of the northern temperate zone, is renowned for its holocentric chromosomes and karyotype variability. The genus exhibits high variation in chromosome numbers both among and within species. Despite the possibility that this chromosome evolution may play a role in the high species diversity of Carex, population-level patterns of molecular and cytogenetic differentiation in the genus have not been extensively studied.
* APRIL- 17-2013
NEW ACCEPTED PUBLICATION ABOUT HOLOCENTRIC CHROMOSOME EVOLUTION AT POPULATION LEVEL.
Methods. We investigated microsatellite variation (11 loci, 461 individuals) and chromosomal diversity (82 individuals) in 22 Midwestern populations of the North American sedge Carex scoparia and two Northeastern populations.
Key Results. Among Midwestern populations, geographic distance is the most important predictor of genetic differentiation. Within populations, inbreeding is high and chromosome variation explains a significant component of genetic differentiation. Infrequent dispersal among populations separated by more than 100 km explains an important component of molecular genetic and cytogenetic diversity within populations. However, karyotype variation and correlation between genetic and chromosomal variation persist within populations even when putative migrants based on genetic data are excluded.
Conclusions. These findings demonstrate dispersal and genetic connectivity among widespread populations that differ in chromosome numbers, explaining the phenomenon of genetic coherence in this karyotypically diverse sedge species. More generally, our study suggests that traditional sedge taxonomic boundaries demarcate good species even when those species encompass a high range of chromosomal diversity. This finding is important evidence as we work to document the limits and drivers of biodiversity in one of the world’s largest angiosperm genera.
* MARCH- 25-2013
NEW ACCEPTED PUBLICATION DESCRIBING A NEW CAREX SPECIES FROM SOUTH AFRICA.
"This new taxon is named after the Rainbow gorge, the place in the Drakensberg Mountains (KwaZulu-Natal, South Africa) where the species was found (there are numerous waterfalls in this gorge producing rainbows). In addition, the species is endemic to South Africa, which is popularly known as the Rainbow Nation. Following the International Code of Botanical Nomenclature (ICBN, Rec. 60D; McNeill et al. 2006) for geographical names, the specific epithet should be “rainbowensis”, but we have used “rainbowii”, since the rainbow symbolizes the peace and the freedom. To both qualities this species is also dedicated".
SANTIAGO MARTIN-BRAVO, MARCIAL ESCUDERO, MONICA MIGUEZ, PEDRO JIMENEZ-MEJIAS & MODESTO LUCEÑO. 2013. MOLECULAR AND MOPHOLOGICAL EVIDENCE FOR A NEW SPECIES FROM SOUTH AFRICA: CAREX RAINBOWII (CYPERACEAE). SOUTH AFRICAN JOURNAL OF BOTANY, 87, 85-91. LINK. PDF.
NEW PUBLICATION ABOUT SELECTION OF HOLOCENTRIC CHROMOSOME NUMBERS AT LOW EVOLUTIONARY SCALE IN THE JOURNAL PERSPECTIVES IN PLANT ECOLOGY, EVOLUTION AND SYSTEMATICS.
MARCIAL ESCUDERO, ENRIQUE MAGUILLA & MODESTO LUCEÑO. IN PRESS. SELECTION BY CLIMATIC REGIME AND NEUTRAL EVOLUTIONARY PROCESSES IN -HOLOCENTRIC CHROMOSOMES (CAREX GR. LAEVIGATA: CYPERACEAE): A MICROEVOLUTIONARY APPROACH. PPEES, 15, 118-129. LINK. PDF.
1. MARCIAL ESCUDERO, ENRIQUE MAGUILLA & MODESTO LUCEÑO. 2013. SELECTION BY CLIMATIC REGIME AND NEUTRAL EVOLUTIONARY PROCESSES IN HOLOCENTRIC CHROMOSOMES (CAREX GR. LAEVIGATA: CYPERACEAE): A MICROEVOLUTIONARY APPROACH. PERSPECTIVES IN PLANT ECOLOGY, EVOLUTION AND SYSTEMATICS, 15, 118-129. LINK. PDF.
2. MARCIAL ESCUDERO, ANDREW HIPP, THOMAS HANSEN, KJETIL VOJE & MODESTO LUCEÑO. 2012. SELECTION AND INERTIA IN THE EVOLUTION OF HOLOCENTRIC CHROMOSOMES IN SEDGES (CAREX, CYPERACEAE). NEW PHYTOLOGIST, 195, 237-247. LINK. PDF.
3. MARCIAL ESCUDERO, ANDREW HIPP, MARCIA WATERWAY & LUIS VALENTE. 2012. DIVERSIFICATION RATES AND CHROMOSOME EVOLUTION IN THE MOST DIVERSE ANGIOSPERM GENUS OF THE TEMPERATE ZONE (CAREX, CYPERACEAE). MOLECULAR PHYLOGENETICS AND EVOLUTION, 63, 650-655. LINK. PDF.
4. MARCIAL ESCUDERO, PABLO VARGAS, PAUL ARENS, JOOP OUBORG & MODESTO LUCEÑO. 2010. THE EAST-WEST-NORTH COLONIZATION HISTORY OF THE MEDITERRANEAN AND EUROPE BY THE COASTAL PLANT CAREX EXTENSA (CYPERACEAE). MOLECULAR ECOLOGY, 19, 352-370. LINK. PDF.