RAPDs and noncoding chloroplast DNA reveal a single origin of the cultivated Allium fistulosum from A. altaicum (Alliaceae)

The origin of the crop species Allium fistulosum (bunching onion) and its relation to its wild relative A. altaicum were surveyed with a restriction fragment length polymorphism (RFLP) analysis of five noncoding cpDNA regions and with a random amplified polymorhic DNA (RAPD) analysis of nuclear DNA. Sixteen accessions of A. altaicum, 14 accessions of A. fistulosum, representing the morphological variability of the species, and five additional outgroup species from Allium section Cepa were included in this study. The RFLP analysis detected 14 phylogenetically informative character transformations, whereas RAPD revealed 126 polymorphic fragments. Generalized parsimony, neighbor-joining analysis of genetic distances, and a principal co-ordinate analysis were able to distinguish the two species, but only RAPD data allowed clarification of the interrelationship of the two taxa. The main results of this investigation were: (1) A. fistulosum is of monophyletic origin, and (2) A. fistulosum originated from an A. altaicum progenitor, making A. altaicum a paraphyletic species. Compared with A. altaicum the cultivated accessions of the bunching onion show less genetic variability, a phenomenon that often occurs in crop species due to the severe genetic bottleneck of domestication. Allium altaicum and A. fistulosum easily hybridize when grown together, and most garden-grown material is of recent hybrid origin.     

On the origin of the invasive olives (Olea europaea L., Oleaceae)

The olive tree (Olea europaea) has successfully invaded several regions in Australia and Pacific islands. Two olive subspecies (subspp. europaea and cuspidata) were first introduced in these areas during the nineteenth century. In the present study, we determine the origin of invasive olives and investigate the importance of historical effects on the genetic diversity of populations. Four invasive populations from Australia and Hawaii were characterized using eight nuclear DNA microsatellites, plastid DNA markers as well as ITS-1 sequences. Based on these data, their genetic similarity with native populations was investigated, and it was determined that East Australian and Hawaiian populations (subsp. cuspidata) have originated from southern Africa while South Australian populations (subsp. europaea) have mostly derived from western or central Mediterranean cultivars. Invasive populations of subsp. cuspidata showed significant loss of genetic diversity in comparison to a putative source population, and a recent bottleneck was evidenced in Hawaii. Conversely, invasive populations of subsp. europaea did not display significant loss of genetic diversity in comparison to a native Mediterranean population. Different histories of invasion were inferred for these two taxa with multiple cultivars introduced restoring gene diversity for europaea and a single successful founder event and sequential introductions to East Australia and then Hawaii for cuspidata. Furthermore, one hybrid (cuspidata x europaea) was identified in East Australia. The importance of hybridizations in the future evolution of the olive invasiveness remains to be investigated.     

Geographic partitioning of chloroplast DNA variation in the genusDatisca (Datiscaceae)

Datisca (Datiscaceae) is a ditypic genus with an intercontinentally disjunct distribution. Chloroplast DNA restriction site data was obtained from 23 populations and four 10–20 year old herbarium specimens ofD. glomerata and three populations ofD. cannabina from throughout their geographic ranges in western North America and southwest-central Asia, respectively. InD. glomerata, plastome diversity is partitioned geographically. All populations from southern California have a common plastome, while most populations north of this region share a relatively divergent plastome (0.49% sequence divergence). Likewise, these plastomes are highly divergent (0.87% mean sequence divergence) from those found inD. cannabina. Biogeographic processes dating to the Pleistocene and Late Miocene may be responsible for these intra- and interspecific patterns of chloroplast DNA divergence.     

The taxonomic status of Polystachya foliosa (orchidaceae) in The Bahama Islands

Polystachya foliosa is lectotypified and a new triandrous variety of it is described from the Bahama Islands and Cuba.     

Development and characterization of 10 microsatellite markers for the semi-evergreen tree species, Ligustrum ovalifolium (Oleaceae)

Ligustrum ovalifolium is a semi-evergreen tree distributed in the western part of Japan and southern Korea. This species contains an insular endemic variety, L. ovalifolium var. pacificum; this variety occurs only on the Izu Islands located south of the Japanese mainland Honshu. We isolated 10 polymorphic microsatellite loci from the species, and characterized them for 21 individuals from a population of L. ovalifolium. The primers developed in this study yielded an average 12.2 alleles per locus and an average expected heterozygosity of 0.78. These markers will be powerful tools for studying the genetic differentiation within the species.     

The taxonomic status ofRhabdolichops troscheli (Kaup, 1856), and speculations on gymnotiform evolution

Synopsis Anatomical and ecological studies of the gymnotiformRhabdolichops troscheli (Kaup 1856), one of the weakly electric fish of South America, indicate it to be unique among gymnotiforms in possessing certain characteristics found in characins. These include post-temporal fossae, well developed gillrakers, a planktivorous feeding mode, and diurnal feeding activity. We use these findings to speculate about the evolution of gymnotiform fishes, by assuming that these character states in this most primitive gymnotiform convey information about the group's evolutionary history. We suggest that the electric organs in this group of ostaryophysans have evolved primarily as a means of locating and capturing prey in river habitats of South America whose turbid waters result in low light penetration, ruling out visual sensing systems as an effective means of receiving information. Other aspects of morphology and behavior such as the absence or reduction of scales, and the nocturnal feeding activities characteristic of other gymnotiform, can be explained as consequences of food resource availability and predation pressures in these riverine environments.     

Origin and diversification of Hibiscus glaber, species endemic to the oceanic Bonin Islands, revealed by chloroplast DNA polymorphism

Abstract Two woody Hibiscus species co-occur in the Bonin Islands of the northwestern Pacific Ocean: Hibiscus glaber Matsum. is endemic to the islands, and its putative ancestral species, Hibiscus tiliaceus L., is widely distributed in coastal areas of the tropics and subtropics. To infer isolating mechanisms that led to speciation of H. glaber and the processes that resulted in co-occurrence of the two closely related species on the Bonin Islands, we conducted molecular phylogenetic analyses on chloroplast DNA (cpDNA) sequences. Materials collected from a wide area of the Pacific and Indian Oceans were used, and two closely related species, Hibiscus hamabo Siebold Zucc. and Hibiscus macrophyllus Roxb., were also included in the analyses. The constructed tree suggested that H. glaber has been derived from H. tiliaceus, and that most of the modern Bonin populations of H. tiliaceus did not share most recent ancestry with H. glaber. Geographic isolation appears to be the most important mechanism in the speciation of H. glaber. The co-occurrence of the two species can be attributed to multiple migrations of different lineages into the islands. While a wide and overlapping geographical distribution of haplotypes was found in H. tiliaceus, localized geographical distribution of haplotypes was detected in H. glaber. It is hypothesized that a shift to inland habitats may have affected the mode of seed dispersal from ocean currents to gravity and hence resulted in geographical structuring of H. glaber haplotypes.     

A chloroplast DNA phylogeny of lilacs (Syringa, Oleaceae): plastome groups show a strong correlation with crossing groups

Phylogenetic relationships and genomic compatibility were compared for 60 accessions of Syringa using chloroplast DNA (cpDNA) and nuclear ribosomal DNA (rDNA) markers. A total of 669 cpDNA variants, 653 of which were potentially phylogenetically informative, was detected using 22 restriction enzymes. Phylogenetic analyses reveal four strongly supported plastome groups that correspond to four genetically incompatible crossing groups. Relationships of the four plastome groups (I(II(III,IV))) correlate well with the infrageneric classification except for ser. Syringa and Pinnatifoliae. Group I, which includes subg. Ligustrina, forms a basal lineage within Syringa. Group II includes ser. Syringa and Pinnatifoliae and the two series have high compatibility and low sequence divergence. Group III consists of three well-defined species groups of ser. Pubescentes. Group IV comprises all members of ser. Villosae and has the lowest interspecific cpDNA sequence divergences. Comparison of cpDNA sequence divergence with crossability data indicates that hybrids have not been successfully generated between species with divergence greater than 0.7%. Hybrid barriers are strong among the four major plastome groups, which have sequence divergence estimates ranging from 1.096 to 1.962%. In contrast, fully fertile hybrids occur between species pairs with sequence divergence below 0.4%. Three regions of the plastome have length variants of greater than 100 bp, and these indels identify 12 different plastome types that correlate with phylogenetic trees produced from cpDNA restriction site data. Biparentally inherited nuclear rDNA and maternally inherited cpDNA length variants enable the identification of the specific parentage of several lilac hybrids.     

A new species ofFontanesia (Oleaceae) from China and taxonomic revision of the genus

Fontanesia longicarpa K.-J. Kim is newly described from China. This distinctive species is known only from the Zhejiang province and differs from other species in the genus by the size and shape of its fruit. As currently circumscribed, the genus now consists of three taxa;F. longicarpa, F. philliraeoides Labill. var.philliraeoides andF. philliraeoides var.fortunei (Carr.) Koehne. A revisionary study of the genus is provided, including a key and pertinent synonymy.     

Assessing the taxonomic status of Osmoderma cristinae (Coleoptera: Scarabaeidae), endemic to Sicily,by genetic,morphological and pheromonal analyses

Resolving complexes of closely related and cryptic insect species can be challenging, especially when dealing with rare and protected taxa that are difficult to collect for genetic and morphological analyses. Until recently, populations of the genus Osmoderma (Scarabaeidae), widespread in Europe, were treated as a single species O. eremita (Scopoli, 1763) in spite of observed geographic variation in morphology. A previous survey using sequence data from the mtDNA cytochrome C oxidase I gene (COI) revealed the occurrence of at least two distinct lineages within this species complex: O. eremita in the west and O. barnabita Motschulsky, 1845, in the east. Interestingly, beetles confined to Sicily have been described as a distinct species, O. cristinae Sparacio, 1994, based on morphological traits. Only few Sicilian specimens were included in the former genetic analysis, and the results led to a still questionable taxonomic rank for these populations. To explore the robustness of the previous taxonomic arrangement for O. cristinae, a combination of genetic, morphological and pheromonal analyses was used. A 617‐bp fragment of the COI gene, aligned with O. cristinae and O. eremita sequences already available in GenBank, showed a clear genetic divergence between the two species (interspecific mean distance = 6.6%). Moreover, results from AFLP markers sustained the distinction of the two species. In addition, geometric morphometric analyses of the shape of male genitalia revealed a clear differentiation between the two species. Via scent analysis and field trapping, we demonstrated the production of the sex pheromone (R)‐(+)‐γ‐decalactone by males of O. cristinae, the attraction by conspecific individuals (mostly females) to this compound, and a lack of antagonistic effect of (S)‐(–)‐γ‐decalactone. The fact that O. eremita and O. eremita use the same compound for mate finding suggests that this sex pheromone has not undergone a differentiation and probably the allopatry of these two species compensates for the absence of a mechanism to avoid cross‐attraction. Our genetic and morphological data support the divergence of the two species and confirm the species status for O. cristinae, while sex pheromones are confirmed to be invariant among different species of the genus Osmoderma.     

Bidirectional history of hybridization in California wild radish, Raphanus sativus (Brassicaceae), as revealed by chloroplast DNA

The evolutionary processes that take place in invasive plant populations are not well documented or understood. Interspecific hybridization between cultivated radish (Raphanus sativus) and R. raphanistrum is known to be responsible for the origin of the invasive California wild radish, but little is known about the nature of the hybridization events that produced the hybrid-derived lineage. We analyzed the trnL-rpl32 intergenic region of chloroplast DNA (cpDNA) obtained from 37 cultivated radish individuals from four different cultivars, 53 R. raphanistrum individuals from six European populations and 104 California wild radish individuals from 11 populations covering its entire range throughout the state. We found that cultivated radish and R. raphanistrum shared no cpDNA haplotypes but that they both shared haplotypes with California wild radish, evidence for bidirectional hybridization between the progenitor species in the creation of the California lineage. We also found evidence that multiple cultivars and multiple European source populations contributed to the diversity of cpDNA haplotypes within California. Studies like this will continue to be important for our understanding of the origin of invasive populations and the mechanisms by which they succeed.     

Fight club: a unique weapon in the wing of the solitaire,Pezophaps solitaria (Aves: Columbidae), an extinct flightless bird from Rodrigues,Mascarene Islands

The solitaire (Columbidae; Pezophaps solitaria) of Rodrigues was an extinct giant flightless pigeon and the sister taxon to the dodo (Columbidae; Raphus cucullatus) from neighbouring Mauritius. The appearance and behaviour of the solitaire was recorded in detail by two observers before it became extinct in the mid 1700s. They described a prominent wing structure termed the ‘musket ball’ (carpal knob), which was used as a weapon and to produce an audible signal by either sex in territorial combat. Our study of subfossil solitaire bones from cave localities shows that the carpal knob formed after skeletal maturity, and reached its greatest size in adult males. We describe the morphology of the carpal knob, including its histology in thin section. It is an outgrowth of the processus extensorius of the carpometacarpus, but differs morphologically from homologous structures in other bird taxa, and thus is unique in Aves. We also compare the pectoral and wing osteology of the solitaire with that of the dodo, which had a similar morphology, but lacked any bony outgrowths on the wing. Furthermore, we suggest some biological and environmental factors leading to the evolution of this remarkable and unique carpal weapon. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 32–44.     

Patterns of Privet: Urbanizing Watersheds,Invasive Ligustrum sinense,and Performance of Native Plant Species in Piedmont Floodplain Forests

Floodplain forests in rapidly changing landscapes with increased urbanization may reshape habitat conditions to the detriment of native biota and favor invasive species. We assessed whether introduced Ligustrum sinense distribution and abundance are causally linked to urbanization and whether mechanisms that promote L. sinense cause the demise of native plant species. We surveyed vegetation in 12 independent floodplain forests along an urban to rural gradient in South Carolina, USA. We then used a seedling transplant experiment in nine watersheds to assess how increased urban development affects survival and growth of L. sinense and three native species over two growing seasons. Urban development ranged from 1 to 45% and L. sinense cover was positively associated with development. However, in our transplant experiment, growth and survival of L. sinense did not differ significantly among watersheds. Native species were able to survive at all sites, but performance varied greatly among sites and species but not as a function of urban development. Our results suggest that although L. sinense invasion and urbanization are related (likely due to proximity of propagules from urban sources), the demise of native species cannot be explained by increased urbanization or changes in edaphic conditions and points to L. sinense as an agent of change in our floodplain forests. These results indicate that all floodplain forests are at risk of invasion if propagules arrive and that land managers need to be vigilant against new species introductions regardless of the proximity to urban areas.     

Multiple colonizations from Madagascar and converged acquisition of dioecy in the Mascarene Dombeyoideae (Malvaceae) as inferred from chloroplast and nuclear DNA sequence analyses

Background and Aims

In the Mascarenes, a young oceanic archipelago composed of three main islands, the Dombeyoideae (Malvaceae) have diversified extensively with a high endemism rate. With the exception of the genus Trochetia, Mascarene Dombeyoideae are described as dioecious whereas Malagasy and African species are considered to be monocline, species with individuals bearing hermaphrodite/perfect flowers. In this study, the phylogenetic relationships were reconstructed to clarify the taxonomy, understand the phylogeographic pattern of relationships and infer the evolution of the breeding systems for the Mascarenes Dombeyoideae.

Methods

Parsimony and Bayesian analysis of four DNA markers (ITS, rpl16 intron and two intergenic spacers trnQ-rsp16 and psbM-trnD) was used. The molecular matrix comprised 2985 characters and 48 taxa. The Bayesian phylogeny was used to infer phylogeographical hypotheses and the evolution of breeding systems.

Key Results

Parsimony and Bayesian trees produced similar results. The Dombeyoideae from the Mascarenes are polyphyletic and distributed among four clades. Species of Dombeya, Trochetia and Ruizia are nested in the same clade, which implies the paraphyly of Dombeya. Additionally, it is shown that each of the four clades has an independent Malagasy origin. Two adaptive radiation events have occurred within two endemic lineages of the Mascarenes. The polyphyly of the Mascarene Dombeyoideae suggests at least three independent acquisitions of dioecy.

Conclusions

This molecular phylogeny highlights the taxonomic issues within the Dombeyoideae. Indeed, the limits and distinctions of the genera Dombeya, Trochetia and Ruizia should be reconsidered. The close phylogeographic relationships between the flora of the Mascarenes and Madagascar are confirmed. Despite their independent origins and a distinct evolutionary history, each endemic clade has developed a different breeding systems (dioecy) compared with the Malagasy Dombeyoideae. Sex separation appears as an evolutionary convergence and may be the consequence of selective pressures particular to insular environments.     

Chromosome numbers, nuclear DNA content, and polyploidy in Consolea (Cactaceae), an endemic cactus of the Caribbean Islands

Polyploidy, an important mechanism of plant evolution, was investigated in Consolea, an endemic Caribbean opuntioid genus represented by nine subdioecious species with very narrow distributions, including species classified as rare or threatened. Standard chromosome counting and flow cytometric analyses were used to determine chromosome numbers and ploidy of each taxon. Compared to the base number (x = 11), the mitotic and meiotic counts indicated that there are seven hexaploid (2n = 66) and two octoploid species (2n = 88); no diploids were found. Histograms of intact nuclei confirmed that all species are polyploid, with C-DNA values ranging from 4.88-9.50 pg. The variation of DNA content was significantly higher for the octoploids than for the hexaploids. Male and female sexual morphs had similar DNA content, suggesting that there are no sex chromosomes. Cytomixis between cells and microsporocytes with no chromatin were observed. This provides a mechanism whereby gametes with variable chromosome numbers are produced, influencing reproduction and promoting speciation. In conclusion, C-DNA content and chromosome number separated Consolea species into two groups, which may correspond to two phylogenetic lineages or indicate that polyploidization occurred independently, with comparable effects on C-DNA content.