Chad Husby

Can a Botanic Garden Cycad Collection Capture the Genetic Diversity in a Wild Population

Premise of research. Conservation of plant species often requires ex situ (off-site) cultivation of living collections. Cycads constitute the most imperiled major group of plants, and ex situ collections are an important part of conservation planning for this group, given seed recalcitrance, difficulties with tissue culture, and ongoing in situ threats. Very little is known about the genetics of ex situ conservation collections of cycads. Thus, this study seeks to illuminate how well an ex situ collection of a cycad can capture the diversity in a wild population. Methodology. A model species, Zamia decumbens, was chosen on the basis of geographic isolation and detailed census knowledge, which allowed near-total sampling of in situ plants. Overall, 375 in situ plants were compared to 205 ex situ plants via 10 microsatellite markers. Pivotal results. Genetic-distance analysis shows high fidelity of the ex situ collections to their in situ source populations as well as clustering of ex situ progeny by accession and strong identity with their respective mother plants. Structured resampling of allele capture from the in situ populations by the ex situ collections shows that allele capture increases as number of ex situ plants maintained increases, but with a diminishing rate of increase. Conclusions. These data demonstrate that botanic garden collections can better conserve the genetic diversity of in situ cycad populations if four recommendations are followed: (1) use the species biology to inform the collecting strategy; (2) manage each population separately; (3) collect and maintain multiple accessions; and (4) collect over multiple years.

Biology and Functional Ecology of Equisetum with Emphasis on the Giant Horsetails

Horsetails are unique survivors of a very ancient group of vascular plants, the Sphenophyta, which has a history reaching back to the Upper Devonian. Despite the striking conservatism of Equisetum architecture and anatomy and the small number of species (15) in the modern flora, their ability to thrive under a wide range of conditions is remarkable. This is due to a diverse suite of adaptations that allow tolerance of disturbance, soil anoxia, high metals, and salinity, along with efficient nutrient uptake and nitrogen fixation. The giant horsetails represent the largest living Sphenophyta and provide insights into how their larger ancestors lived and how this ancient lineage has managed to survive in tropical regions.

Cyclone tolerance in new world arecaceae: biogeographic variation and abiotic natural selection.

BACKGROUND AND AIMS Consistent abiotic factors can affect directional selection; cyclones are abiotic phenomena with near-discrete geographic limits. The current study investigates selective pressure of cyclones on plants at the species level, testing for possible natural selection. METHODS New World Arecaceae (palms) are used as a model system, as plants with monopodial, unbranched arborescent form are most directly affected by the selective pressure of wind load. Living specimens of known provenance grown at a common site were affected by the same cyclone. Data on percentage mortality were compiled and analysed in biogeographic and phylogenetic contexts. KEY RESULTS Palms of cyclone-prone provenance exhibited a much lower (one order of magnitude) range in cyclone tolerance, and significantly lower (P < 0.001) mean percentage mortality than collections from cyclone-free areas. Palms of cyclone-free provenance had much greater variation in tolerance, and significantly greater mean percentage mortality. A test for serial independence recovered no significant phylogenetic autocorrelation of percentage mortality. CONCLUSIONS Variation in cyclone tolerance in New World Arecaceae correlates with biogeography, and is not confounded with phylogeny. These results suggest natural selection of cyclone tolerance in cyclone-prone areas.

Is Managed Relocation of Rare Plants Another Pathway for Biological Invasions

Numerous studies have suggested that Earth’s climate has changed and will continue to change in response to human activities. It is expected that average temperatures will increase, in some places as much as 4 °C, between 1990 and 2040 (IPCC 2007). In addition, precipitation will probably change, becoming drier in some areas and wetter in others. The intensity of storms, such as hurricanes, may also increase in some areas (IPCC 2007). Biological organisms have physiological tolerances to climate extremes, which may decrease their ability to survive or be sufficiently competitive in the new climates, with different ranges. Although most animals and some plants may be able to migrate to more appropriate locations, many plants have limited seed dispersal capabilities and may be unable to reach suitable habitat without assistance.

Salinity tolerance ecophysiology of Equisetum giganteum in South America: a study of 11 sites providing a natural gradient of salinity stress

In river valleys of the worlds driest desert (The Atacama of South America) large stands of giant horsetail (Equisetum giganteum) are found to tolerate soil water salinity up to at least half that of seawater. The roots selectively exclude Na and take-up K in response to salinity while stomatal conductances and photochemical efficiency of Photosystem II remain unaffected.

Further Nomenclatural Action for the Cypresses (Cupressaceae)

Abstract.  The relationships among cypress species of the closely related genera Cupressus L., Callitropsis Oerst., and the recently described Hesperocyparis Bartel & R. A. Price were examined using morphological characters. Previous studies did not fully resolve New World and Old World cypresses, the status of Cupressus duclouxiana B. Hickel, Cupressus benthamii Endl., and Cupressus funebris Endl. being in question. Cupressus duclouxiana is sister to Hesperocyparis and Cupressus benthamii is sister to Callitropsis, while Cupressus funebris is considered a basal taxon to all other Cupressus investigated. The intrusion of Hesperocyparis lusitanica (Mill.) Bartel characters into the standard descriptions of Cupressus torulosa D. Don ex Lamb. is examined in order to clarify the differentiation of the respective genera. An emended description of Callitropsis constituting a grade of three species is provided. The new combination, Callitropsis funebris (Endl.) de Laub. & Husby, is provided for Cupressus funebris. Five names at new varietal rank are transferred to Hesperocyparis, as H. arizonica (Greene) Bartel var. nevadensis (Abrams) de Laub. [≡ Cupressus nevadensis Abrams], H. arizonica var. montana (Wiggins) de Laub. [≡ Cupressus montana Wiggins], H. goveniana (Gordon) Bartel var. abramsiana (C. B. Wolf) de Laub. [≡ Cupressus abramsiana C. B. Wolf], H. goveniana var. pygmaea (Lemmon) de Laub. [≡ Cupressus goveniana Gordon var. pygmaea Lemmon], and H. lusitanica var. lindleyi (Klotzsch ex Endl.) de Laub. [≡ Cupressus lindleyi Klotzch ex Endl.].

Morphometric Analysis of Aiphanes Minima (Arecaceae) Across the Antilles

Abstract. Morphometric analyses are used to test two competing hypotheses of classification for Aiphanes (Arecaceae: Cocoseae) in the Antilles. Three vegetative characters and three characters of the inflorescence were analyzed via one-way analyses of variance followed by a test of pairwise comparisons for the least-squares means. We found a complex pattern of morphological variation that supports the recognition of a single, variable species, Aiphanes minima. Resumen. Se usaron análisis morfométricos para evaluar dos hipótesis opuestas referentes a la clasificación de Aiphanes (Arecaceae: Cocoseae) en las Antillas. Se sometieron tres caracteres vegetativos y tres de las inflorescencias a análisis de varianza de una via, seguidos por una prueba de comparaciones en pares para las medias de mínimos cuadrados. Se encontró un patrón complejo de variación morfológica que apoya la existencia de una sola especie variable, Aiphanes minima.