Ana M. Anton

On the names of the Andean species of Poa L. (Poaceae) described by Pilger

Abstract Anton, A. M. & Negritto, M. A.: On the names of the Andean species of Poa L. (Poaceae) described by Pilger. — Willdenowia 27: 235–247. 1997. — ISSN 0511-9618. Lectotypes are designated for the names of nine Andean Poa species described by Pilger. No holotype was indicated by the author for both Poa gymnantha and P. humillima, and the holotypes of P. candamoana, P. carazensis, P. chamaeclinos, P. fibrifera, P. gilgiana, P. horridula, and P. pardoana at B were destroyed in 1943. Analytical drawings based on the lectotypes are presented for all nine species.

Some evolution trends in the inflorescence of Poaceae

Summary It is postulated that the wide diversity shown by the inflorescence of grasses can be explained by means of a fairly restricted number of processes which have mainly reductive characteristics. Depending on the mode of action of these processes, a means is proposed by which the origin of different types of inflorescences can be recognized. In all cases, the starting point is a panicle with primary and secondary branches, from which, following four major evolutionary trends, the origins of other structures can be determined.

The grass flower; suggestions on its origin and evolution

Summary Analysing a large number of different grass flowers, a hypothesis is proposed to explain the floral variation found in the family. It is postulated that the interaction of the palea with the floral apex generates an area of inhibition wich substantially affects the floral apex. Depending on the mode of action in the reduction process, together with an independent phenomenon which affects the gynoecial organization, four major evolutionary patterns are recognized. The form of grass flower which has been most successful appears to be the bi-lodiculate, tri-staminate and bi-stigmatic, with the stamens belonging to two different cycles – the frontal from the outer whorl and the two lateral from the inner whorl.

The grass megagametophyte and its possible phylogenetic implications

The structure of the grasses megagametophyte is considered to be characteristic enough as to deserve a particular place in the megagametophyte typology. Furthermore, it is compared with those of other Monocotyledonous families to point out embryological affinities.

Pollen-pistil size correlation and pollen size-number trade-off in species of Argentinian Nyctaginaceae with different pollen reserves

Data on pollen and pistil traits from 14 Argentinean Nyctaginaceae species with starch or lipids as pollen reserves are presented. We expect differences in the traits between these two groups of species, but the same pattern within each group for (a) the relationship between pollen size and pistil length assuming that pollen tube length is predetermined by provisions in the pollen independently of the pollen reserve type, and for (b) a trade-off between size and number because available resources for male function are not unlimited. In particular we expect that (a) species with longer pistils will have larger pollen grains, (b) pollen grain size and the number of pollen grains per flower will be negatively correlated. Significant differences in the mean pollen number per flower and mean pollen size were observed between species with different pollen reserve type but not for pistil length. Then, correlation analyses were performed for species with starchy pollen or with pollen with lipids separately. Pollen size - pistil length correlation was positive and significant for species with starchy pollen but not for species with pollen with lipids. On the other hand, pollen size - number correlation was not significant for both starchy and oil-rich species. Results suggest that pollen reserve type would be a relevant factor that constraint pollen size in species of Nyctaginaceae, and that this pollen trait should be considered when studying pollen-pistil relationships, mainly between species of those families with mixed pollen reserves.

Munroa argentina, a Grass of the South American Transition Zone, Survived the Andean Uplift, Aridification and Glaciations of the Quaternary

The South American Transition Zone (SATZ) is a biogeographic area in which not only orogeny (Andes uplift) and climate events (aridification) since the mid-Miocene, but also Quaternary glaciation cycles had an important impact on the evolutionary history of the local flora. To study this effect, we selected Munroa argentina, an annual grass distributed in the biogeographic provinces of Puna, Prepuna and Monte. We collected 152 individuals from 20 localities throughout the species’ range, ran genetic and demographic analyses, and applied ecological niche modeling. Phylogenetic and population genetic analyses based on cpDNA and AFLP data identified three phylogroups that correspond to the previously identified subregions within the SATZ. Molecular dating suggests that M. argentina has inhabited the SATZ since approximately 3.4 (4.2–1.2) Ma and paleomodels predict suitable climate in these areas during the Interglacial period and the Last Glacial Maximum. We conclude that the current distribution of M. argentina resulted from the fragmentation of its once continuous range and that climate oscillations promoted ecological differences that favored isolation by creating habitat discontinuity.

Contrasting models of the female reproductive tract in four o’clocks (Nyctaginaceae)

UNLABELLED • PREMISE OF THE STUDY In angiosperms, several carpel tissues are specialized to facilitate pollen-tube elongation to achieve fertilization. We evaluated the possible evolutionary pathways of the diverse female reproductive tracts in Nyctaginaceae.• METHODS We studied the anatomy of a range of species representing different tribes, using light, fluorescence, scanning electron, and transmission electron microscopy.• KEY RESULTS Stigmas have multicellular, multiseriate papillae, except for Boerhavia diffusa with unicellular papillae. The styles are solid, with a strand of transmitting tissue linking the stigma with the ventral ovary wall. In Allionia, Boerhavia, and Mirabilis, the transmitting tissue branches into two independent tracts at the base of the ovary and continues across the lateral margins of the funicle to the micropyle; it is composed of cells with thick walls surrounded by abundant extracellular matrix. Bougainvillea, Pisonia, and Pisoniella have a diffuse transmitting tissue and an obturator, a proliferation of cells covered by a layer of secretory papillae that encloses the funicle, placenta, and ventral wall of the gynoecium and contacts with the micropyle.• CONCLUSIONS We propose two models of female reproductive tract, (A) one in which an obturator is absent and the transmitting tissue is compact and branched and (B) one in which an obturator is present and the transmitting tissue is diffuse. On the basis of character optimization, we hypothesize that model B represents the ancestral (plesiomorphic) condition in the family and model A originated once during evolution, within the tribe Nyctagineae.

Colonization in North American Arid Lands: The Journey of Agarito (Berberis trifoliolata) Revealed by Multilocus Molecular Data and Packrat Midden Fossil Remains.

Here we conduct research to understand the evolutionary history of a shrubby species known as Agarito (Berberis trifoliolata), an endemic species to the Chihuahuan Desert. We identify genetic signatures based on plastid DNA and AFLP markers and perform niche modelling and spatial connectivity analyses as well as niche modelling based on records in packrats to elucidate whether orogenic events such as mountain range uplift in the Miocene or the contraction/expansion dynamics of vegetation in response to climate oscillations in the Pliocene/Pleistocene had an effect on evolutionary processes in Agarito. Our results of current niche modelling and palaeomodelling showed that the area currently occupied by Berberis trifoliolata is substantially larger than it was during the Last Interglacial period and the Last Glacial Maximum. Agarito was probably confined to small areas in the Northeastern and gradually expanded its distribution just after the Last Glacial Maximum when the weather in the Chihuahuan Desert and adjacent regions became progressively warmer and drier. The most contracted range was predicted for the Interglacial period. Populations remained in stable areas during the Last Glacial Maximum and expanded at the beginning of the Holocene. Most genetic variation occured in populations from the Sierra Madre Oriental. Two groups of haplotypes were identified: the Mexican Plateau populations and certain Northeastern populations. Haplogroups were spatially connected during the Last Glacial Maximum and separated during interglacial periods. The most important prediction of packrat middens palaeomodelling lies in the Mexican Plateau, a finding congruent with current and past niche modelling predictions for agarito and genetic results. Our results corroborate that these climate changes in the Pliocene/Pleistocene affected the evolutionary history of agarito. The journey of agarito in the Chihuahuan Desert has been dynamic, expanding and contracting its distribution range and currently occupying the largest area in its history.

Three New Species of Poa from the Andes of Colombia and Peru

Abstract During a revision of Andean Poa, three new species, one from Colombia and two from Peru, were recognised as new and are described here. Poa soderstromii from the Páramo of Chisacá, Colombia, is similar to the Peruvian Poa brevis from which it differs by having the glumes nearly as long as the spikelet and the lemmas conspicuously 5-nerved and scabrous on the keel. Poa oscariana, from Cusco, is similar to P. gilgiana and P. huancavelicae; from both it can be separated by the spikelets broadly elliptic in outline, 4.5–5.5 mm long and dull pale green, and glumes and lemmas asperulous, without hyaline margins. Poa pilgeri from Junín, Huancayo, resembles P. candamoana, but differs by its filiform and convolute leaves and small spikelets. The species are described, illustrated and compared with similar species. A key as well as commentaries on the subgeneric affinities of the new species are included.

A New Synonym in Senna, Series Aphyllae (Leguminosae, Caesalpinioideae)

Abstract Multivariate and univariate analyses based on morphological characters were carried out in order to understand the taxonomic status of Senna spiniflora and S. chacoënsis. Fifteen morphological characters from herbarium specimens were recorded and analyzed by the Kruskal-Wallis test and principal components analysis. The type specimens and all available herbarium material were examined for the taxonomic study. The results showed that the taxa differed only by the character of stem pubescence and this feature displayed high variability. In parallel, the principal components analysis demonstrated that no clearly separated groups were recognized. Based upon these results, the synonymy of S. chacoënsis to S. spiniflora is proposed.