320 research outputs found
Eleocharis yecorensis (Cyperaceae), a new species of spike-sedge from MĆ©xico
Eleocharis (Cyperaceae) includes approximately 200 species and is particularly diverse in the New World. A newly discovered species of subgenus Limnochloa is described from the states of Sonora and Mexico, Mexico. Eleocharis yecorensis is related to E. acutangula, E. mutata. and E. quadrangulata and can be distinguished from these species by its five-angled culms, obdeltoid achenes. and narrow neck between tubercle and achene body. In addition. E. yecorensis possesses root storage structures similar to those found in the Chinese water chestnut, Eleocharis dulcis
C4 Photosynthesis: Convergence upon Convergence uponā¦
C4 photosynthesis has evolved independently numerous times in plants. New work suggests that these multiple origins are the result of recurring selection on a few amino acid positions in the key enzyme phosphoenolpyruvate carboxylase
Glume absence in the Orcuttieae (Gramineae: Chloridoideae) and a hypothisis of intratribal relationships
This study addresses glume absence in tribe Orcuttieae. In Orcuttia califomica, O. inaequalis, and O. viscida, all spikelets possess two glumes except for the terminal spikelet of the inflorescence, which lacks both glumes. In O. pilosa and Tuctoria greenei the terminal spikelet lacks only the first (proximal) glume, whereas in O. tenuis, T. fragilis, and T. mucronata both glumes are developed on all spikelets. This is the first report of glume absence in species of Orcuttieae other than Neostapfia colusana, which has been long reported to lack both glumes on all spikelets. A hypothesis of phylogenetic relationships in the tribe is presented and characters involved are discussed. We hypothesize Neostapfia to be sister to a Tuctoria/Orcuttia clade, and Tuctoria to be a grade leading to a monophyletic Orcuttia
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The unique and moderating effects of religious, family and school connectedness on early adolescent adjustment
textParent-adolescent connection is considered a core parenting component influencing adolescent psychosocial development. When the connection is poor, the adolescent has an increased risk of developing depressive symptoms and behavioral problems. Non-family socialization experiences increase in importance as the quality of family experiences decreases and may protect adolescents with low family connectedness from demonstrating depressive symptoms and behavioral problems. The school is one context that may provide socialization experiences to promote continued development for early adolescents. Stronger levels of connection to the school have been related to decreased prevalence of adolescent problem behaviors such as delinquency. The religious community represents another context in which early adolescents may develop important connections. This context is particularly important to study as over half of all adolescents in the U.S. report attending church services weekly and/or are involved in a church youth group and approximately 60% of adolescents report their faith is important to them. Research examining adolescent feelings of connection to their religious group and how this relates to delinquent behaviors and depressive symptoms, however, is lacking. The present study explored the cross-sectional contribution of adolescent connections to the family, school and religious contexts to the depressive symptoms and delinquent behaviors of a sample of 167 middle school students. Three aspects of religious connectedness (i.e., youth leader, congregation member, and spiritual connectedness) were found to uniquely contribute to the occurrence of early adolescent outcomes. Specifically, youth leader and spiritual connectedness uniquely contributed to early adolescent engagement in more serious delinquent behaviors. Congregation member and spiritual connectedness contributed to the occurrence of early adolescent depressive symptoms. Additionally, all three types of religious connectedness buffered the relationship between family connectedness and more serious delinquent behaviors. That is, high levels of religious connectedness protected early adolescents from engaging in the problem behaviors. Unexpectedly, an exacerbating relationship was demonstrated between school connectedness and youth leader connectedness as well as spiritual connectedness on early adolescent less serious delinquent behaviors. Findings are discussed from the perspectives of Social Control Theory and Attachment Theory.Kinesiology and Health Educatio
A Floristic Study in the Diamond Creek Drainage Area, Gila National Forest, New Mexico
The Diamond Creek drainage is one of the major watershed systems of the Gila National Forest in southwestern New Mexico. The purposes of this study were to catalog the vascular plants of a portion of this drainage area, describe the vegetation zones, locate any threatened, endangered, or sensitive plant species, and assess plant regeneration in areas that have been burned. The study area is located in the eastern portion of the Gila National Forest along the Black Range in the northwest corner of Sierra County. It covers approximately 5600 hectares (14000 acres) and ranges in elevation from 2250 to 3000 m (7400 to 9850 ft). Collected from the upper main Diamond Creek drainage area were 348 species including an additional six infraspecific taxa. The five largest families (by number of species and infraspecific taxa) in the study area were the Asteraceae (58), Poaceae (52), Fabaceae (24), Rosaceae (19), and Cyperaceae (17). The study area can be classified as Montane Coniferous Forest with most of the study area dominated by Pinus ponderosa and Pseudotsuga menziesii var. glauca. This overall vegetation type is fractured by narrow canyons, open meadows, perennial and intermittent streams, and rock outcrops. Three sensitive plant species were located in the study area: Erigeron scopulinus, Senecio sacramentanus, and Draba mogollonica. Two fires have occurred in the study area in recent times. These burned areas are primarily covered by shrubs including Quercus gambelii, Robinia neomexicana var. neomexicana, and Populus tremuloides
Chromosome Evolution in Cyperales
Karyotypic evolution is a prominent feature in the diversiļ¬cation of many plants and animals, yet the role that chromosomal changes play in the process of diversiļ¬cation is still debated. At the diploid level, chromosome ļ¬ssion and/or fusion are necessary components of chromosomal structural change associated with diversiļ¬cation. Yet the genomic features required for these events remain unknown. Here we present an overview of what is known about genomic structure in Cyperales, with particular focus on the current level of understanding of chromosome number and genome size and their impact in a phylogenetic context. We outline ongoing projects exploring genomic structure in the order using modern genomics techniques coupled with traditional data sets. Additionally, we explore the questions to which this approach might be best applied, and in particular, detail a project exploring the nature of genomic structural change at the diploid level in genus Carex, a group in which chromosome ļ¬ssion/fusion events are common and associated with diversiļ¬cation of many of its 2000 species. A hypothesized mechanism for chromosome number change in this genus is agmatoploidy, denoting changes in chromosome number without change in DNA amount through ļ¬ssion/fusion of holocentric chromosomes (chromosomes without localized centromeres). This project includes the creation of bacterial artiļ¬cial chromosome (BAC) and expressed sequence tagged (EST) libraries to be used in physical and genetic linkage mapping studies in order to reveal the patterns of genome structural variation associated with agmatoploidy in Carex, and to explore the sequence and genic characteristics of chromosomal break points in the genome
Megaphylogenetic Specimen-Level Approaches to the Carex (Cyperaceae) Phylogeny Using ITS, ETS, and matK Sequences: Implications for Classification
We present the first large-scale phylogenetic hypothesis for the genus Carex based on 996 of the 1983 accepted species (50.23%).
We used a supermatrix approach using three DNA regions: ETS, ITS and matK. Every concatenated sequence was derived from a single
specimen. The topology of our phylogenetic reconstruction largely agreed with previous studies. We also gained new insights into the early
divergence structure of the two largest clades, core Carex and Vignea clades, challenging some previous evolutionary hypotheses about
inflorescence structure. Most sections were recovered as non-monophyletic. Homoplasy of characters traditionally selected as relevant for
classification, historical misunderstanding of how morphology varies across Carex, and regional rather than global views of Carex diversity
seem to be the main reasons for the high levels of polyphyly and paraphyly in the current infrageneric classification
Phylogeny of Cyperaceae Based on DNA Sequence Dataāa New rbcL Analysis
Since the Monocots II meeting in 1998, signiļ¬cant new data have been published that enhance our systematic knowledge of Cyperaceae. Phylogenetic studies in the family have also progressed steadily. For this study, a parsimony analysis was carried out using all rbcL sequences currently available for Cyperaceae, including data for two new genera. One of the four subfamilies (Caricoideae) and seven of the 14 tribes (Bisboeckelereae, Cariceae, Cryptangieae, Dulichieae, Eleocharideae, Sclerieae, Trilepideae) are monophyletic. Subfamily Mapanioideae and tribe Chrysitricheae are monophyletic if, as the evidence suggests, Hellmuthia is considered a member of Cypereae. Some other features of our analysis include: well-supported Trilepideae and SclerieaeāBisboeckelereae clades; a possible close relationship between Cryptangieae and Schoeneae; polyphyletic tribes Schoeneae and Scirpeae; the occurrence of Cariceae within the DulichieaeāScirpeae clade, and a strongly supported clade, representing Cyperus and allied genera in Cypereae, sister to a poorly supported FiciniaāHellmuthiaā IsolepisāScirpoides clade. Such patterns are consistent with other studies based on DNA sequence data. One outcome may be that only two subfamilies, Mapanioideae and Cyperoideae, are recognized. Much further work is needed, with efforts carefully coordinated among researchers. The work should focus on obtaining morphological and molecular data for all genera in the family
Phylogenetic Relationships of Monocots Based on the Highly Informative Plastid Gene ndhF
We used ndhF sequence variation to reconstruct relationships across 282 taxa representing 78 monocot families and all 12 orders. The resulting tree is highly resolved and places commelinids sister to Asparagales, with both sister to LilialesāPandanales in the strict consensus; Pandanales are sister to Dioscoreales in the bootstrap majority-rule tree, just above Petrosaviales. Acorales are sister to all other monocots, with Alismatales sister to all but Acorales. Relationships among the four major clades of commelinids remain unresolved. Relationships within orders are consistent with those based on rbcL, alone or in combination with atpB and 18S nrDNA, and generally better supported: ndhF contributes more than twice as many informative characters as rbcL, and nearly as many as rbcL, atpB, and 18S nrDNA combined. Based on functional arguments, we hypothesized that net venation and fleshy fruits should both evolveāand thus undergo concerted convergenceāin shaded habitats, and revert to parallel venation and dry, passively dispersed fruits in open, sunny habitats. Our data show that net venation arose at least 26 times and disappeared 9 times, whereas fleshy fruits arose 22 times and disappeared 11 times. Both traits arose together at least 15 times and disappeared together 5 times. They thus show a highly significant pattern of concerted convergence (P \u3c 10-9) and are each even more strongly associated with shaded habitats (P \u3c 10-10 to 10-23); net venation is also associated, as predicted, with broad-leaved aquatic plants. Exceptions to this pattern illustrate the importance of other selective constraints and phylogenetic inertia
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