Molecular Phylogenetics and Evolution 54 (2010) 344–356
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Molecular Phylogenetics and Evolution 54 (2010) 344–356 Contents lists available at ScienceDirect Molecular Phylogenetics and Evolution journal homepage: www.elsevier.com/locate/ympev Delimiting species boundaries within the Neotropical bamboo Otatea (Poaceae: Bambusoideae) using molecular, morphological and ecological data Eduardo Ruiz-Sanchez *, Victoria Sosa Departamento de Biologia Evolutiva, Instituto de Ecologia, A. C., Apartado Postal 63, 91000 Xalapa, Veracruz, Mexico article info abstract Article history: Species delimitation is a task that has engaged taxonomists for more than two centuries. Recently, it has Received 2 April 2009 been demonstrated that molecular data and ecological niche modeling are useful in species delimitation. Revised 28 October 2009 In this paper multiple data sets (molecular, morphological, ecological) were utilized to set limits for the Accepted 30 October 2009 species belonging to the Neotropical bamboo Otatea, because there is disagreement about species circum- Available online 6 November 2009 scriptions and also because the genus has an interesting distribution, with most of its populations in Mexico and a single disjunct population in Colombia. Molecular and morphological phylogenetic analyses Keywords: recovered trees with conflicting topologies. Tree-based morphological and character-based analyses rec- Diagnostic characters ognized the same entities. Ecological niche models and PCA/MANOVAS agreed with the recognition of the Ecological niche modeling Molecular parsimony same entities that resulted from the morphological analyses. Morphological analyses retrieved clades Morphology tree-based analysis supported by diagnostic characters and coherent geographical distributions. Based on these results seven Niche divergence entities should be recognized in Otatea, instead of the three previously described species. Statistical parsimony network Ó 2009 Elsevier Inc. All rights reserved. 1. Introduction Current research considers niche modeling to be useful for identi- fying and diagnosing species (Raxworthy et al., 2007; Rissler and Traditionally, species delimitation in the plant kingdom has Apodaca, 2007; Stockman and Bond, 2007; Bond and Stockman, been based on morphological differences. However, the inclusion 2008) and for finding potential new species (Raxworthy et al., of molecular and ecological data in recent years has provided more 2003). Niche modeling is able to provide evidence for geographic evidence for delimiting species. Sites and Marshall (2003, 2004),in isolation among populations (based on either conserved or diver- their synopsis of operational criteria for delimiting species bound- gent ecological niches) and takes populations to be separately aries, designated two broad categories: tree-based and non-tree- evolving lineages when gene flow is considered unlikely for the based methods. Among procedures for establishing species intervening geographic regions (Wiens and Graham, 2005). boundaries is the novel method proposed by Wiens and Penkrot A number of animal species were defined with the WP method (2002), which uses morphological and molecular data and tree- (e.g., Hendrixson and Bond, 2005; Leavitt et al., 2007; Mulcahy, based and character-based analyses simultaneously. The WP 2008) yet it has never been utilized with plants. It has been argued method utilizes DNA haplotypes in parsimony analysis assuming that polyploidy, asexual reproduction or hybridization are factors a phylogeny of non-recombining haplotypes which may show that solely affect evolutionary processes in plants (Rieseberg, the focal species to be either exclusive or not exclusive. The tree- 1997; Mable, 2004; Rieseberg and Willis, 2007; Silvertwon, 2008; based morphological analysis uses populations as terminals rather Soltis et al., 2007). However, Rieseberg et al. (2006) have suggested than individuals to avoid a biased treatment of the polymorphisms that a lack of congruence between correspondence of plant and shared between populations as homoplasies rather than synapo- animal species could be in relation to these same factors but not morphies. Furthermore, the character-based analysis in the WP by contemporary hybridization. Moreover, Rieseberg et al. (2006) method involves finding diagnostic character states that represent generalized that plant species are more likely than animal species differences among the putative species. The WP method considers to represent reproductively independent lineages. strongly supported set of exclusive and geographically coherent We selected the Neotropical bamboo Otatea (McClure and E.W. populations to be potentially distinct species. In this paper this Sm) C. Calderón and Soderstr. as a test of the WP for delimiting concept was expanded by performing niche modeling analyses. plant species for a number of reasons. The first reason is that there is controversy on the recognition of two groups within O. acumi- nata, a variable species with the widest distribution in the genus. * Corresponding author. Fax: +52 228 818 7809. E-mail addresses: [email protected], eduardo.ruiz@posgrado. Initially Otatea was described with Otatea acuminata (Munro) C. inecol.edu.mx (E. Ruiz-Sanchez), [email protected] (V. Sosa). Calderón and Soderstr. Later Otatea aztecorum was described but 1055-7903/$ - see front matter Ó 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.ympev.2009.10.035 E. Ruiz-Sanchez, V. Sosa / Molecular Phylogenetics and Evolution 54 (2010) 344–356 345 it is now considered to be a subspecies of O. acuminata (subsp. logical, and ecological). Four questions emerge from this objective: aztecorum). Therefore O. acuminata is the focal species in our anal- Do subspecies in O. acuminata merit species status? Could the dis- yses. Two additional species were later described, O. fimbriata Sod- junct population of O. fimbriata from Colombia be recognized as erstr. and O. glauca L.G. Clark and G. Cortés, and a new, still different? Can recently collected populations be assigned to previ- undescribed species from Chiapas is also known (Guzmán et al., ously described species or do they need to de described as new 1984; Judziewicz et al., 1999; Clark and Cortés, 2004; Ruiz-Sanchez taxa? Does ecological niche modeling give new insights to identify et al., 2008). What is more, our intensive fieldwork has discovered and diagnose taxa? How many species should be recognized in the an elevated morphological variation in populations from previ- Neotropical bamboo genus Otatea? ously unexplored areas, which have not yet been characterized. The second reason to select this taxon, is that species in Otatea have allopatric distribution patterns and occupy different habitats, 2. Materials and methods so that niche modeling could give new insights to identify and diagnose taxa. Otatea acuminata is endemic to Mexico, from Sonora 2.1. Taxon sampling along of the Pacific slopes to Chiapas and in central Mexico along the Transvolcanic Belt in tropical dry forest and xerophytic Individuals of Otatea were collected during 2005–2007 scrubs. Otatea fimbriata has a disjunct distribution, collected from throughout the entire range of distribution of the genus (Fig. 1). three areas in Mexico and Central America, and one record from Olmeca recta Soderstr., a taxon closely related to Otatea, was used Colombia (Londoño and Clark, 1998) in dry pine–oak–juniper or as the outgroup (Ruiz-Sanchez et al., 2008). A total of 109 individ- even in dry tropical forests. O. glauca is endemic to Chiapas and uals from 28 populations were sampled with 3–12 individuals per only recollected from a single population, on slopes in the ecotone population (Fig. 1, Table 1). Fresh leaves were collected from each of tropical dry forests and oak forests. The undescribed species individual and dried in silica (Chase and Hills, 1991) and the from Chiapas is currently only known from a single population in vouchers were deposited at XAL. tropical dry forest. The third reason for selecting Otatea is because its plants are 2.2. Morphological data set monocarpic with a mass flowering. Populations usually flower for 2 or 3 years, and then the plants die. Herbarium records indicate The morphological matrix included 54 characters (40 vegeta- that the cycles of mass flowering last 17–30 years. Thus it is diffi- tive, six from synflorescences and flowers and eight leaf micromor- cult to find flowering plants to analyze floral characters. Molecular phological characters (Appendix 1; data matrix in Appendix 2). evidence for specimens lacking inflorescences might increase the Character selection was based on the list and illustrations by L. number of informative characters used in defining species bound- Clark in ‘‘Bamboo Biodiversity” (http://www.eeob.iastate.edu/re- aries, together with vegetative morphological characters. search/bamboo) and on Londoño and Clark (2002). Characters were The main objective of this study is to set limits for the species scored by examining live material and herbarium specimens. belonging to Otatea using multiple data sets (molecular, morpho- Vouchers and examined specimens are also listed in Appendix 3. Fig. 1. Distribution and sampling localities of the previously recognized species of Otatea. Numbers correspond to localities in Table 1. (A and B) Details of localities in central Mexico and Chiapas, respectively. 346 E. Ruiz-Sanchez, V. Sosa / Molecular Phylogenetics and Evolution 54 (2010) 344–356 Table 1 Study populations and their haplotypes. n = number of individuals sampled for cpDNA markers,