Host specificity and reproductive success of yucca moths (Tegeticula spp. Lepidoptera: Prodoxidae) mirror patterns of gene flow between host plant varieties of the Joshua tree (Yucca brevifolia: Agavaceae)

Coevolution between flowering plants and their pollinators is thought to have generated much of the diversity of life on Earth, but the population processes that may have produced these macroevolutionary patterns remain unclear. Mathematical models of coevolution in obligate pollination mutualisms suggest that phenotype matching between plants and their pollinators can generate reproductive isolation. Here, we test this hypothesis using a natural experiment that examines the role of natural selection on phenotype matching between yuccas and yucca moths (Tegeticula spp.) in mediating reproductive isolation between two varieties of Joshua tree (Yucca brevifolia var. brevifolia and Y. brevifolia var. jaegeriana). Using passive monitoring techniques, DNA barcoding, microsatellite DNA genotyping, and sibship reconstruction, we track host specificity and the fitness consequences of host choice in a zone of sympatry. We show that the two moth species differ in their degree of host specificity and that oviposition on a foreign host plant results in the production of fewer offspring. This difference in host specificity between the two moth species mirrors patterns of chloroplast introgression from west to east between host varieties, suggesting that natural selection acting on pollinator phenotypes mediates gene flow and reproductive isolation between Joshua‐tree varieties.     

Chemistry and geographic variation of floral scent in Yucca filamentosa (Agavaceae)

We identified volatiles from the floral headspace of Yucca filamentosa using gas chromatography and mass spectrometry and analyzed floral scent composition and variation among populations pollinated by different yucca moth species. Twenty-one scent compounds were repeatedly identified and most could be categorized into two major classes: (1) homoterpenes derived from the sesquiterpene alcohol nerolidol and (2) long chain aliphatic hydrocarbons. Two biosynthetic pathways are thus responsible for the majority of floral volatiles in Y. filamentosa. The homoterpene E-4,8-dimethylnona-1,3,7-triene, which is released systemically by higher plants upon herbivory, was the most abundant compound. Two di-oxygenated compounds not previously reported as floral compounds also were detected. No differentiation in floral scent was observed between populations pollinated by different yucca moths, nor was there any correlation between chemical distance and geographic distance among populations. The total release rate of volatiles differed significantly among populations, but not between populations with different pollinators. The combination of unique compounds and low variation in the fragrance blend may reflect highly selective attraction of obligate pollinators to flowers. The observed lack of differentiation in floral scent can putatively explain high moth-mediated gene flow among sites, but it does not explain conservation of odor composition across populations with different pollinators.     

Yucca linearifolia (Agavaceae): A new,indehiscent, fleshy-fruited,linear-leaved species endemic to the Chihuahuan Desert,Mexico

Yucca linearifolia is described, illustrated, and distinguished from other yucca species. Its distinctive combination of fleshy fruit and narrow, linear, denticulate leaves sets it apart from all other yuccas. Se describe e ilustraYucca linearifolia y se discute su separación de otras especies del géneroYucca. La combinación de caracteres tales como el fruto, carnoso y la hoja linear y denticulada la distingue del resto de las especies del género.     

Reproductive consequences of interactions between Yucca glauca (Agavaceae) and Tegeticula yuccasella (Lepidoptera) in Colorado

For over 100 years the association between Yucca (Agavaceae) and Tegeticula (Lepidoptera: Incurvariidae) has been accepted as a quintessential example of an obligate mutualism. The yucca moth is purported to be the sole pollinator of Yucca, while Yucca flowers provide courtship and mating arenas, and Yucca seeds provide food for developing Tegeticula larvae. We studied Yucca glauca in northern Colorado, comparing the reproductive ecology and breeding systems of Yucca in plains populations, the “preferred” habitat of Yucca, with “marginal” sites at the edge of the local elevational distribution. Tegeticula are abundant at plains sites, and fruit set is significantly higher than in the foothills, where fruit set is limited by the paucity of moths. The low frequency of moths at high elevation, coupled with behaviors of adult female Tegeticula which lead to self-pollination, failure to pollinate, and periodic overloading of fruits with eggs, may help explain why Yucca glauca appears to maintain alternative pollinators. Some fruits lack evidence of Tegeticula infestation, suggesting that larvae die before completing development, or that fertilization of Yucca sometimes occurs without the intervention of Tegeticula. Biochemical analyses of nectar and observations of floral visitors revealed that it is highly likely that the fly Pseudocalliope sp. nov. (Lauxaniidae), which congregates and mates on Yucca glauca blossoms, acts as a secondary pollinator. Autogamy appears to occur infrequently in natural populations. We therefore propose that the yucca-yucca moth symbiosis be viewed as a facultative mutualism.     

Pattern and timing of diversification in Yucca (Agavaceae): specialized pollination does not escalate rates of diversification

The yucca-yucca moth interaction is one of the most well-known and remarkable obligate pollination mutualisms, and is an important study system for understanding coevolution. Previous research suggests that specialist pollinators can promote rapid diversification in plants, and theoretical work has predicted that obligate pollination mutualism promotes cospeciation between plants and their pollinators, resulting in contemporaneous, parallel diversification. However, a lack of information about the age of Yucca has impeded efforts to test these hypotheses. We used analyses of 4322 AFLP markers and cpDNA sequence data representing six non-protein-coding regions (trnT-trnL, trnL, trnL intron, trnL-trnF, rps16 and clpP intron 2) from all 34 species to recover a consensus organismal phylogeny, and used penalized likelihood to estimate divergence times and speciation rates in Yucca. The results indicate that the pollination mutualism did not accelerate diversification, as Yucca diversity (34 species) is not significantly greater than that of its non-moth-pollinated sister group, Agave sensu latissimus (240 species). The new phylogenetic estimates also corroborate the suggestion that the plant-moth pollination mutualism has at least two origins within the Agavaceae. Finally, age estimates show significant discord between the age of Yucca (ca 6-10Myr) and the current best estimates for the age of their pollinators (32-40Myr).     

Oviposition and pollination behavior of the yucca moth,Tegeticula maculata (Lepidoptera: Prodoxidae), and its relation to the reproductive biology of Yucca whipplei (Agavaceae)

Summary The adult behavior of the yucca moth, Tegeticula maculata Riley, is finely tuned to the reproductive biology of its specific host plant, Yucca whipplei Torr. The female moths oviposit in the ovaries of the yucca flowers and actively pollinate the same flowers with pollen which they have collected previously. The selective pressures imposed on the moths by 1) the plant's need for pollen transfer via an insect pollinating agent, 2) its partial self-incompatibility, and 3) its ability to regulate seed set by aborting excess fruits, have molded the pollinator's behavior in such a way that its offspring have the greatest possible chance of surviving through the early larval stages. The evolutionary responses of the pollinator include the following: 1) the female moths consistently fly to a different plant after collecting pollen, thus insuring cross-fertilization of the flowers, 2) they always pollinate after depositing the first egg in a flower, but not necessarily after subsequent ovipositions, and 3) females emerging near the end of the flowering season frequently oviposit in developing seed pods, as opposed to open flowers which are more likely to be aborted by the plants.     

Long-term growth patterns of Welwitschia mirabilis,a long-lived plant of the Namib Desert (including a bibliography)

Plant Ecology - Over the past 14 years, long-term ecological research (LTER) was conducted on the desert perennial, Welwitschia mirabilis (Gnetales: Welwitschiaceae), located in the Welwitschia...     

Genetic differentiation in the Agave deserti (Agavaceae) complex of the Sonoran desert

The Agave deserti complex, comprising A. deserti, A. cerulata and A. subsimplex, represents a group of species and subspecies with a near allopatric distribution and clear differences in morphology. Genetic differentiation and taxonomic status with respect to spatial distribution of 14 populations of the complex were analyzed in an effort to understand the evolution and speciation process within the genus. Allelic frequencies, levels of genetic variation, expected heterozygosity (H(S)), proportion of polymorphic loci (P), and genetic differentiation (theta and Nei's genetic distance) were estimated using 41 putative RAPD loci. All three species show high levels of genetic variation (H(S)=0.12-0.29, P=63.4-95.1), and low genetic differentiation between populations and species (theta populations=0.14+/-0.02 (SE); G(st)=0.11+/-0.02). Accordingly, gene flow among populations was estimated as high by three different methods (N(m)=2.91-6.14). Nei's genetic distances between the three species were low compared to the values obtained from other Agavaceae, and there was no clear correlation with taxonomic divisions. In a UPGMA analysis, A. subsimplex and A. cerulata formed exclusive monospecific clusters, whereas the A. deserti populations appear in more than one cluster together with other species. The results were consistent with a pattern of genetic isolation by distance.     

The establishment patterns of tree seedlings are determined immediately after wildfire in a black spruce (Picea mariana) forest

Fire severity is predicted to increase in boreal regions due to global warming. We hypothesized that these extreme events will alter regeneration patterns of black spruce (Picea mariana). To test this hypothesis, we monitored seed dispersal and seedling emergence, survival and growth for 6 years from 2005 to 2010 after the 2004 wildfire on Poker Flat, interior Alaska, using 96 1 × 1 m plots. A total of 1,300 seedlings of black spruce and three broad-leaved deciduous trees (Populus tremuloides, Betula papyrifera, and Salix spp.) were recorded. Black spruce seedlings colonized burned and unburned ground surfaces for the first 2 years after the wildfire and established on any topographical surface, while the broad-leaved trees emerged less in areas of lower elevation, slope gradient and canopy openness and only on burned surfaces. Vascular plant cover on the ground floor increased the seedling establishment of black spruce and broad-leaved trees, most likely because of seed-trap effects. Black spruce grew faster on burned surface than on unburned surfaces. However, broad-leaved trees grew faster than black spruce on burned surfaces. Black spruce regenerates even after severe wildfire when the microtopography restricts the colonization of broad-leaved trees. The regeneration trajectories are determined soon after wildfire by a combination of seed limitation for black spruce and habitat preference for broad-leaved trees.     

Differential leaf gas exchange responses to salinity and drought in the mangrove tree Avicecennia germinans (Avicenniaceae)

Leaf gas exchange was assessed in Avicennia germinans L. grown under different NaCl concentrations (0-40 per thousand), after salt-relief, and then during drought. Stomatal conductance (gs) and net photosynthetic rate (Pn) decreased with increasing NaCl concentration, and intrinsic water use efficiency (Pn / gs) increased. Under desalinization Pn / gs declined. Thus, gs did not change in plants grown at low NaCl concentration (10 per thousand), but increased up to 30-32% at higher NaCl concentration (20-40 per thousand). However, Pn was only slightly enhanced (10-15%). Under drought, Pn decreased by as much as 46% in plants grown at low NaCl concentration (10 per thousand) and by 22% at high NaCl concentration (40 per thousand). Thus, Pn / gs decreased and water use efficiency was lower during drought compared to estimates prior to salt-relief.     

The colonization history of Juniperus brevifolia (Cupressaceae) in the Azores Islands

Background

A central aim of island biogeography is to understand the colonization history of insular species using current distributions, fossil records and genetic diversity. Here, we analyze five plastid DNA regions of the endangered Juniperus brevifolia, which is endemic to the Azores archipelago.

Methodology/Principal Findings

The phylogeny of the section Juniperus and the phylogeographic analyses of J. brevifolia based on the coalescence theory of allele (plastid) diversity suggest that: (1) a single introduction event likely occurred from Europe; (2) genetic diversification and inter-island dispersal postdated the emergence of the oldest island (Santa Maria, 8.12 Ma); (3) the genetic differentiation found in populations on the islands with higher age and smaller distance to the continent is significantly higher than that on the younger, more remote ones; (4) the high number of haplotypes observed (16), and the widespread distribution of the most frequent and ancestral ones across the archipelago, are indicating early diversification, demographic expansion, and recurrent dispersal. In contrast, restriction of six of the seven derived haplotypes to single islands is construed as reflecting significant isolation time prior to colonization.

Conclusions/Significance

Our phylogeographic reconstruction points to the sequence of island emergence as the key factor to explain the distribution of plastid DNA variation. The reproductive traits of this juniper species (anemophily, ornithochory, multi-seeded cones), together with its broad ecological range, appear to be largely responsible for recurrent inter-island colonization of ancestral haplotypes. In contrast, certain delay in colonization of new haplotypes may reflect intraspecific habitat competition on islands where this juniper was already present.     

Initiation and growth of cell lines of Taxus brevifolia (Pacific yew)

Summary Conditions have been established for the induction and maintenance of callus cultures of Taxus brevifolia (Pacific yew) from bark, stem, and needle tissues. Cultures were established on a modified Gamborg's B5 medium, 1% sucrose, 0.2% casamino acids and 1 mg/L 2,4-D. There was no apparent inhibition of callus induction as a result of taxol concentration in the explant material. Cell lines derived from explants of individual trees were used to investigate growth characteristics. Although none of the cell lines contained taxol, some contained low levels of related taxanes. Variability was observed with each cell line in response to light, and auxin type and concentration. Growth index was most affected by cell line, followed by auxin type and concentration. These culturing methods may be useful for the goal of developing a highproducing cell line applicable for large-scale taxol production.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - NAA naphthaleneacetic acid - IAA indoleacetic acid - CA casamino acids - B5CA B5 with 0.2% casamino acids - IBA indolebutryric acid; Picloram (4-amino-3,5,6-tricnloro-2-pyridinecarboxylic acid) - 2,4,5-T 2,4,5-trichlorophenoxyacetic acid - BA 6-benzylaminopurine     

Dependence of the dwarf sundew (Drosera brevifolia) on burrowing crayfish disturbance

Plant Ecology - Disturbance is necessary for the survival of most species of carnivorous plants to reduce competition and expose bare soil for germination. Historically, fire was the most...     

Natural genetic differentiation and human-mediated gene flow: the spatiotemporal tendency observed in a long-lived <Emphasis Type="Italic">Cinnamomum camphora</Emphasis> (Lauraceae) tree

The camphor tree (Cinnamomum camphora) is an important natural resource in East Asia. From the early eighteenth to mid-twentieth century, C. camphora was widely cultivated to obtain camphor, a white crystalline substance used as a repellent, a component of medicine, and an ingredient in the production of smokeless gunpowder and celluloid. The vast utilization and cultivation of C. camphora have obscured its natural distribution, and the genetic structure of this species was likely affected by both natural factors and human activities in different areas and at different times. To estimate this process, we collected 817 samples from Japan, China, and Taiwan, including samples from trees estimated to be hundreds to thousands of years old. Population genetic analyses using 11 microsatellite markers detected the footprints of ancient genetic differentiation and recent human-mediated gene flow. The strong genetic differentiation between areas (Japan vs. China and Taiwan) and the decreased genetic diversity in Japan can be ascribed to the long-term geographical isolation during and after the glacial period. Within each area, the genetic composition of the cultivated or planted populations was often inconsistent with the surrounding natural and/or older specimens. This finding may be due to the regional transfer of plant materials with no regard to their genetic origin. We also detected rare but evident immigration from different areas; furthermore, these non-native genets seemed to locally hybridize with the native genets. We suggest that the intentional transfer and/or artificial hybridization between areas should be prohibited in order to preserve the genetic composition of C. camphora.     

Carbohydrate Analysis of Floral and Extra-floral Nectars in Selected Taxa of Sansevieria (Agavaceae)

A comparative analysis of the simple carbohydrates (fructose,glucose, sucrose) between floral and extra-floral nectars wasperformed among 17 taxa and two established cultivars of Sansevieria.Floral nectars (FNs) were found to be universally sucrose dominant,while extra-floral nectars (EFNs) were extremely sucrose poor(hexose dominant). Monosaccharide: saccharide ratios for FNsvaried from 1: 1.1 to 1: 4.4. By contrast, monosaccharide: disaccharideratios of EFNs varied from 6.0: 1 to 17.1: 1. Floral and inflorescencemorphology in addition to chemical factors strongly suggesta hawkmoth pollinated syndrome. Extra-floral nectaries may provideprotection of the inflorescence against herbivores by ants orother aggressive insects. Sansevieria, Agavaceae, floral nectars, extra-floral nectars, pollination     

A new leaf-tying Episimus Walsingham (Lepidoptera: Tortricidae) feeding on the vulnerable tree Haplorhus peruviana (Anacardiaceae) in the Atacama Desert of northern Chile

Episimus Walsingham, 1892 (Lepidoptera: Tortricidae: Olethreutinae: Olethreutini) is reported for the first time from Chile. Male and female adults of Episimus buarquei Brito & Vargas sp. n. are described and illustrated based on specimens reared from larvae collected on the vulnerable native tree Haplorhus peruviana Engler (Anacardiaceae) in the Chaca Valley, Atacama Desert of northern Chile. DNA barcode sequences of the cytochrome c oxidase subunit I mitochondrial gene are provided and used to preliminarily assess the relationships of E. buarquei with congeneric species.

http://zoobank.org/urn:lsid:zoobank.org:pub:CDD4BF83-F8AB-4644-8047-77793AB43CA6