Biomechanics and functional anatomy of hollow-stemmed sphenopsids. I. Equisetum giganteum (Equisetaceae)

The hollow stem of Equisetum giganteum owes its mechanical stability to an outer ring of strengthening tissue, which provides stiffness and strength in the longitudinal direction, but also to an inner lining of turgid parenchyma, which lends resistance to local buckling. With a height >2.5 m isolated stems are mechanically unstable. However, in dense stands individual stems support each other by interlacing with their side branches, the typical growth habit of semi-self-supporters.     

Triploidy in Equisetum subgenus Hippochaete (Equisetaceae, Pteridophyta)

BACKGROUND AND AIMS: The genus Equisetum is cytologically uniform, having a base chromosome number of x = 108. All previously known species and hybrids that have been counted represent diploids with a sporophytic chromosome number of 2n = 216. Biosystematic studies on Equisetum subgenus Hippochaete revealed evidence that triploids occur in nature. The objective of this study was to confirm that triploid plants exist in the natural environment. METHODS: Flow cytometry was used to establish nuclear DNA values and cytological investigations of meiosis were carried out to obtain information on chromosome number and pairing behaviour. KEY RESULTS: Triploidy exists in three morphologically different hybrid taxa. Two of these are morphologically intermediate between a primary diploid hybrid and a parent, while the third apparently combines genomes from all three Central European Hippochaete species. Nuclear 1C DNA values for the four European Hippochaete species range from 21.4-31.6 pg. For the hybrids, the 1C DNA values not only occupy the same range as the species, but their total DNA amounts agree closely with values predicted by adding the 1C DNA values of each parental genome. Chromosome counts confirm diploidy in the species E. hyemale and E. variegatum and in the hybrid E. xtrachyodon (= E. hyemale x E. variegatum). For the triploids (2n approximately 324), cytological information is presented for the first time. CONCLUSIONS: Triploid taxa may have originated by backcrossing or by crossing of a diploid hybrid with an unrelated diploid species. As tetraploid plants are unknown, these crossings probably involve diploid gametophytes that developed from unreduced diplospores. By repeated crossing events or backcrossing, reticulate evolution patterns arise that are similar to those known for a number of ferns and fern allies.     

草问荆（木贼科）的地理分布

通过整合全球植物志文献资料,结合调查中国科学院植物研究所植物标本馆（PE）、北京林业大学森林植物标本馆（BJFC）和中国科学院沈阳应用生态研究所植物标本馆（IFP）馆藏腊叶标本,以及进行野外观测,获取了草问荆的地理分布数据。采用地理绘图软件MapInfo Professional 8．0,绘制草问荆在中国及世界的资源分布图,首次提供了其在中国的详细分布资料,为深入理解和开发草问荆资源提供了必要的生物学基本数据。     

草问荆(木贼科)的地理分布

通过整合全球植物志文献资料, 结合调查中国科学院植物研究所植物标本馆(PE)、北京林业大学森林植物标本馆(BJFC)和中国科学院沈阳应用生态研究所植物标本馆(IFP)馆藏腊叶标本, 以及进行野外观测, 获取了草问荆的地理分布数据。采用地理绘图软件MapInfo Profes sional 8.0, 绘制草问荆在中国及世界的资源分布图, 首次提供了其在中国的详细分布资料, 为深入理解和开发草问荆资源提供了必要的生物学基本数据。     

Desiccation-time limits of photosynthetic recovery in Equisetum hyemale (Equisetaceae) spores

The chlorophyllous spores of Equisetum survive desiccation, yet cannot tolerate this quiescent state for more than ~2 wk. The hypothesis that spore viability of Equisetum hyemale L. is limited by inhibition of photosynthetic recovery was tested using chlorophyll a fluorescence and oxygen-exchange analyses. Experimental spores were desiccated at 2% relative humidity and 25C for time periods of 24 h, 1 wk, and 2 wk, and then rehydrated at 200 mmol photons/m2s (PAR) and 25C for up to 24 h. Spores desiccated for 24 h recovered photosynthetic competence very rapidly during rehydration, reaching the O2 compensation point in 6.3 ~ 0.3 (mean +/- SE) min. Recovery of photosynthetic performance of spores desiccated for 1 wk was slower, as judged by significantly slower increases of (1) photochemical efficiency of photosystem (PS) II, (2) PS II quinoneB-reducing center concentration, (3) quinoneB concentration, (4) water-oxidation activity, (5) rate of light-induced O2 evolution, and (6) apparent quantum yield of net O2 exchange. Photosystem-II and whole-spore photosynthetic competence of 2-wk desiccated spores was increasingly impaired, and did not recover during rehydration. Origin fluorescence yield and dark respiration were not affected by desiccation time following rehydration. The results suggest that the extremely short viability of disseminated spores of Equisetum hyemale is due to the inability to recover losses of water oxidation and photosystem II-core function following 2 wk of desiccation.     

Arrangement of microtubules during spore formation in Equisetum arvense (Equisetaceae)

The arrangement of cortical microtubules (MTs) during spore formation in Equisetum arvense was examined by immunofluorescence microscopy. The arrangement of MTs was observed to change during sporoderm formation. During exospore formation, the cortical MTs of the tapetum appeared along the tapetal plasma membrane that enclosed each developing spore cell. After exospore formation, the arrangement of the cortical MTs changed into one of separate bands of MTs arranged spirally (spiral bands of MTs). The spiral bands of MTs were superimposed on the developing elaters. This new pattern corresponded to the pattern of cellulose microfibrils deposited in the inner layer of the elater, suggesting that these spiral bands are involved in the deposition of the cellulose microfibrils in the elater. We conclude that the spiral bands of MTs are functionally equivalent to cortical MTs in secondary wall formation.     

Biogeography and genome size evolution of the oldest extant vascular plant genus,Equisetum (Equisetaceae)

Background and AimsExtant plant groups with a long fossil history are key elements in understanding vascular plant evolution. Horsetails (Equisetum, Equisetaceae) have a nearly continuous fossil record dating back to the Carboniferous, but their phylogenetic and biogeographic patterns are still poorly understood. We use here the most extensive phylogenetic analysis to date as a framework to evaluate their age, biogeography and genome size evolution.MethodsDNA sequences of four plastid loci were used to estimate divergence times and investigate the biogeographic history of all extant species of Equisetum. Flow cytometry was used to study genome size evolution against the framework of phylogenetic relationships in Equisetum.Key ResultsOn a well-supported phylogenetic tree including all extant Equisetum species, a molecular clock calibrated with multiple fossils places the node at which the outgroup and Equisetum diverged at 343 Mya (Early Carboniferous), with the first major split among extant species occurring 170 Mya (Middle Jurassic). These dates are older than those reported in some other recent molecular clock studies but are largely in agreement with a timeline established by fossil appearance in the geological record. Representatives of evergreen subgenus Hippochaete have much larger genome sizes than those of deciduous subgenus Equisetum, despite their shared conserved chromosome number. Subgenus Paramochaete has an intermediate genome size and maintains the same number of chromosomes.ConclusionsThe first divergences among extant members of the genus coincided with the break-up of Pangaea and the resulting more humid, warmer climate. Subsequent tectonic activity most likely involved vicariance events that led to species divergences combined with some more recent, long-distance dispersal events. We hypothesize that differences in genome size between subgenera may be related to the number of sperm flagellae.     

Genetic diversity and population structure in the outcrossing populations of Equisetum arvense and E. hyemale (Equisetaceae)

An allozyme examination was conducted to study the mating systems and genetic differentiation of populations of Equisetum arvense and E. hyemale. The study revealed that the rate of intragametophytic selfing in these homosporous pteridophytes is very low, i.e., on average 0.020 and 0.019, respectively, despite the potential hermaproditism and selfing of the gametophytes. Most populations consisted of numerous genotypes, and the average heterozygosities of E. arvense and E. hyemale equalled 0.092 and 0.134, respectively. The commonly observed excess of the heterozygote genotypes indicates that there are interclonal differences in the frequency of vegetative reproduction. The level of genetic divergence among populations was considerable even within a limited geographic area. It is suggested that the life history of Equisetum, characterized by the inefficiency of spore germination and gametophyte reproduction in noncolonizing situations, limits the level of gene flow and leads to a great genetic divergence between populations.     

The calanoid fauna (Crustacea,Copepoda) of the Cordillera Oriental of the Colombian Andes

Calanoid copepods belonging to four species and one subspecies from lakes and ponds mainly from the Cordillera Oriental (22) and Cordillera Central (1) of the Colombian Andes are recorded. Most of the water bodies studied are located in the páramo region, between 2996 and 4085 m altitude. The family Boeckellidae is recorded for the first time from Colombia. Taxonomic characteristics of Boeckella occidentalis Marsh, 1906, Boeckella gracilis (Daday,1902) and the diaptomid Prionodiaptomus colombiensis (Thiébaud, 1914) are discussed. A new diaptomid genus, Colombodiaptomus, with one species and one subspecies are established.     

Chloroplast Genome Differences between Asian and American Equisetum arvense (Equisetaceae) and the Origin of the Hypervariable trnY-trnE Intergenic Spacer

Comparative analyses of complete chloroplast (cp) DNA sequences within a species may provide clues to understand the population dynamics and colonization histories of plant species. Equisetum arvense (Equisetaceae) is a widely distributed fern species in northeastern Asia, Europe, and North America. The complete cp DNA sequences from Asian and American E. arvense individuals were compared in this study. The Asian E. arvense cp genome was 583 bp shorter than that of the American E. arvense. In total, 159 indels were observed between two individuals, most of which were concentrated on the hypervariable trnY-trnE intergenic spacer (IGS) in the large single-copy (LSC) region of the cp genome. This IGS region held a series of 19 bp repeating units. The numbers of the 19 bp repeat unit were responsible for 78% of the total length difference between the two cp genomes. Furthermore, only other closely related species of Equisetum also show the hypervariable nature of the trnY-trnE IGS. By contrast, only a single indel was observed in the gene coding regions: the ycf1 gene showed 24 bp differences between the two continental individuals due to a single tandem-repeat indel. A total of 165 single-nucleotide polymorphisms (SNPs) were recorded between the two cp genomes. Of these, 52 SNPs (31.5%) were distributed in coding regions, 13 SNPs (7.9%) were in introns, and 100 SNPs (60.6%) were in intergenic spacers (IGS). The overall difference between the Asian and American E. arvense cp genomes was 0.12%. Despite the relatively high genetic diversity between Asian and American E. arvense, the two populations are recognized as a single species based on their high morphological similarity. This indicated that the two regional populations have been in morphological stasis.     

Altitudinal variation of dung beetle (Scarabaeidae: Scarabaeinae) assemblages in the Colombian Andes

Aim We describe the changes in species richness, rarity and composition with altitude, and explore whether the differences in Scarabaeinae dung beetle composition along five altitudinal transects of the same mountain range are related to altitude or if there are interregional differences in these altitudinal gradients. Location Field work was carried out on the eastern slope of the eastern Cordillera, Colombian Andes, between Tamá Peak to the north, in the Tamá National Park (07°23′ N, 72°23′ W) and the San Miguel River (00°28′ N, 77°17′ W) to the south. Methods Sampling was carried out between February 1997 and November 1999 in five regions spanning elevation gradients. In each gradient, six sites were chosen at 250 m intervals between 1000 and 2250 m a.s.l. Results We found a curvilinear relationship between altitude and mean species richness, with a peak in richness at middle elevations. However, the diversity of dung beetle assemblages does not seem to be related to the interregional differences in environmental conditions. The number of geographically restricted species is negatively and significantly related to altitude, with geographically restricted species more frequent at low altitude sites. Ordination delimited the two main groups according to altitude: one with all the highest sites (1750–2250 m a.s.l.) and a second group with the remaining sites (< 1750 m a.s.l.). Analysis of species co‐occurrence shows that these dung beetle assemblages seem to be spatially structured when all sites have the same probability of being chosen. In contrast, the spatial structure of species assemblages seems to be random when the probability of choosing any site is proportional to its altitude. Main conclusions The altitude of sites is the main factor that influences the diversity of these dung beetle assemblages. The peak in species richness at middle elevations, the higher number of geographically restricted species at lower altitudinal levels, and the compositional differences along these mountain gradients seem to result from the mixing at these altitudes of dung beetle assemblages that have different environmental adaptations and, probably, different origins. The relevance of altitude in these assemblages is related to the limited role of these Neotropical high altitude environments as centres of refuge and vicariance for a monophyletic group of warm‐adapted species, for which the vertical colonization of these high mountain environments by lineages distributed at lower altitudes would have been very difficult.     

Description of Pintomyia limafalcaoae and Pintomyia antioquiensis,two new species of phlebotomine sand fly (Diptera,Psychodidae) from the Colombian Andes

Two new species of phlebotomine sand fly from Colombian Andes are described, belonging to the subgenus Pifanomyia of the genus Pintomyia. P. (P.) limafalcaoae sp. nov. for which both sexes are described, is assigned to the series pia while P. (P.) antioquiensis sp. nov., known only from the male, is included in the series verrucarum. The subgenus Pifanomyia is characterized and identification keys presented for the two new species.     

Taxonomy of Mechanitis (F.) (Lepidoptera: Nymphalidae) from the West Colombian Andes: an Integrative Approach

Species identification in the butterfly genus Mechanitis (F.) (Lepidoptera: Nymphalidae) becomes difficult when it is based only on wing color patterns, a common practice in butterfly taxonomy. Difficulties in Mechanitis taxonomy are related to the widespread mimicry and polymorphism among species belonging to this genus. Species recognition and inventories of Mechanitis genus in geographic areas as the Andean region of Colombia are of particular interest and the use of more than one character for taxonomic identification is desirable. In this study, we included morphological, ecological, and mitochondrial DNA data to identify the occurring species in this region. Species of Mechanitis were studied from ecological, morphological, and molecular perspectives considering host plant identification, oviposition behavior, and life cycles under laboratory conditions. Immature morphology, patterns of wing color, and genital structures of adults were also studied. The genetic barcoding region of the cytochrome oxidase I mitochondrial gene was sequenced and used to verify the limits between species previously defined by the other characters and to validate its usefulness for species delimitation in this particular genus. The integrative approach combining independent datasets successfully allowed species identification as compared to the approach based on a single dataset. Three well-differentiated species were found in the studied region, Mechanitis menapis (Hewitson), Mechanitis polymnia (Linnaeus), and Mechanitis lysimnia (Fabricius). New valuable characters that could improve taxonomic identification in this genus are considered.     

Sieve-Element Ontogeny in the Aerial Shoot of Equisetum hyemale L.

The aerial shoots of Equisetum hyemale L. var. affine (Engelm.)A. A. Eat. were examined with the electron microscope as partof a continuing study of sieveelement development in the lowervascular plants. Young E. hyemale sieve elements are distinguishablefrom all other cell types within the vascular system by thepresence of refractive spherules, proteinaceous bodies whichdevelop within dilated portions of the endoplasmic reticulum(ER). Details of cell wall thickening differ between protophloemand metaphloem sieve elements. Following cell wall thickeningthe ER increases in quantity and aggregates into stacks. Shortlythereafter, nuclear degeneration is initiated. During the periodof nuclear degeneration some cytoplasmic components-dictyosomes,microtubules and ribosomes-degenerate and disappear, while organellessuch as mitochondria and plastids persist. The latter undergostructural modifications and become parietal in distribution.Eventually the massive quantities of ER are reduced, leavingthe lumen of the cell clear in appearance. At maturity the plasmalemma-linedsieve element contains a parietal network of tubular ER, aswell as mitochondria, plastids, and refractive sphemh At thistime many of the spherules are discharged into the region ofthe wall. Sieveelement pores occur in both lateral and end walls.At maturity many pores are traversed by large numbers of ERmembranes. The metaphloem sieve elements of the mid-internodalregions apparently are sieve-tube members. The connections betweenmature protophloem sieve elements and pericycle cells are associatedwith massive wall thickenings on the pericyclecell side.     

A new case of an Holarctic element in the Colombian Andes: first record of Cordyla Meigen (Diptera,Mycetophilidae) from the Neotropical region

Three new species of Mycetophilidae – Cordyla monticola sp. n., Cordyla pseudopusilla sp. n. and Cordyla reducta sp. n. – are described from the Colombian Andes, representing the first described species of Cordyla Meigen from the Neotropical region. Colour photos of their habitus, wing and terminalia are provided. The morphological affinities of male terminalia are discussed in a worldwide context. The distributional pattern of the genus clearly indicates a case of northern elements reaching the north-western region of the Neotropics that corresponds to a secondary extension of a Holarctic clade to the south.     

Botanical origin and geographic differentiation of bee-pollen produced in high mountains from the Colombian eastern Andes

In the high mountains of the Colombian Eastern Cordillera (~2000–3000 m above sea level), at the Altiplano Cundiboyacense region and surroundings, beekeepers have specialised in pollen production with substantial harvests all year round. Despite this productive advantage, the knowledge about plants used by honeybees as pollen resources is still limited. Hence, the aim of this work was to identify the botanical origin of bee pollen from this region and to examine differences between five distinguished sub-regions: Sabana de Bogotá, Fúquene, Márquez, Tundama and Norte-Gutiérrez. By means of palynological analyses of 86 pollen samples produced between 2008 and 2010, we found a total amount of 126 pollen types, most of them belonging to the families Asteraceae and Fabaceae. Major pollen types correspond to the exotic taxa Hypochaeris radicata, Brassicaceae, Eucalyptus globulus, Trifolium repens, Trifolium pratense and the native taxa Quercus humboldtii and Weinmannia sp. Differences between sample groups from the five sub-regions were mainly associated to variations in pollen abundance and frequency of native plant species. This result highlights the potential for commercialising bee-pollen from the Colombian Eastern Cordillera with geographical origin differentiation, as well as the importance for beekeeping in promoting the conservation of the natural ecosystems from the region.     

Ultrastructural analysis of flagellar development in plurilocular sporangia of Ectocarpus siliculosus (Phaeophyceae)

Flagellar development in the plurilocular zoidangia of sporophytes of the brown alga Ectocarpus siliculosus was analyzed in detail using transmission electron microscopy and electron tomography. A series of cell divisions in the plurilocular zoidangia produced the spore-mother cells. In these cells, the centrioles differentiated into flagellar basal bodies with basal plates at their distal ends and attached to the plasma membrane. The plasma membrane formed a depression (flagellar pocket) into where the flagella elongated and in which variously sized vesicles and cytoplasmic fragments accumulated. The anterior and posterior flagella started elongating simultaneously, and the vesicles and cytoplasmic fragments in the flagellar pocket fused to the flagellar membranes. The two flagella (anterior and posterior) could be clearly distinguished from each other at the initial stage of their development by differences in length, diameter and the appendage flagellar rootlets. Flagella continued to elongate in the flagellar pocket and maintained their mutually parallel arrangement as the flagellar pocket gradually changed position. In mature zoids, the basal part of the posterior flagellum (paraflagellar body) characteristically became swollen and faced the eyespot region. Electron dense materials accumulated between the axoneme and the flagellar membrane, and crystallized materials could also be observed in the swollen region. Before liberation of the zoospores from the plurilocular zoidangia, mastigoneme attachment was restricted to the distal region of the anterior flagellum. Structures just below the flagellar membrane that connected to the mastigonemes were clearly visible by electron tomography.     

New species in Adiantum and Pteris (Pteridaceae) from the Andes

We describe, discuss, and illustrate four new species, one inAdiantum (A. capillatum A. R. Sm. &; Prado, from Ecuador) and three species inPteris (P. lellingeri A. R. Sm. &; Prado, from Bolivia;P. venezuelensis A. R. Sm. &; Prado, from Venezuela; andP. websteri A. R. Sm. &; Prado, from Ecuador, Colombia, and Bolivia).