D. Wilson Freshwater

Bio: D. Wilson Freshwater is an academic researcher from University of North Carolina at Wilmington. The author has contributed to research in topics: Gelidiales & Gelidium. The author has an hindex of 23, co-authored 66 publications receiving 1600 citations. Previous affiliations of D. Wilson Freshwater include Wilmington University.

Reconstructing the lionfish invasion: insights into Greater Caribbean biogeography

Abstract: Aim Lionfish (Pterois volitans and P. miles) are popular ornamental fishes native to the Indo-Pacific that were introduced into Florida waters and are rapidly spreading and establishing throughout the Western Atlantic (WA). Although unfortunate, this invasion provides an excellent system in which to test hypotheses on conservation biology and marine biogeography. The goals of this study are: (1) to document the geographical extent of P. volitans and P. miles; (2) to determine whether the progression of the lionfish invasion is the result of expansion following the initial introduction event or the consequence of multiple introductions at various WA locations; and (3) to analyse the chronology of the invasion in conjunction with the genetic data in order to provide real-time assessments of hypotheses of marine biogeography. Location The Greater Caribbean, including the US east coast, Bermuda, the Bahamas and the Caribbean Sea. Methods Mitochondrial control region sequences were obtained from lionfish individuals collected from Bermuda and three Caribbean locations and analysed in conjunction with previously published data from five native and two non-native locations (US east coast and the Bahamas; a total of six WA locations). Genetic variation within and among groups was quantified, and population structure inferred via spatial analyses of molecular variance, pairwise ΦST, exact tests, Mantel tests and haplotype networks. Results Mitochondrial DNA screening of WA lionfish shows that while P. miles is restricted to the northernmost locations (Bermuda and the US east coast), P. volitans is ubiquitous and much more abundant. Invasive populations of P. miles and P. volitans have significantly lower levels of genetic diversity relative to their native counterparts, confirming that their introduction resulted in a strong founder effect. Despite the relative genetic homogeneity across the six WA locations, population structure analyses of P. volitans indicate significant differentiation between the northern (US east coast, the Bahamas and Bermuda) and the Caribbean populations. Main conclusions Our findings suggest that the ubiquity of WA lionfish is the result of dispersal from a single source of introduction in Florida and not of multiple independent introductions across the range. In addition, the progression of the lionfish invasion (as documented from sightings), integrated with the genetic evidence, provides support for five of six major scenarios of connectivity and phylogeographical breaks previously inferred for Caribbean organisms.

Mitochondrial control region sequence analyses indicate dispersal from the US East Coast as the source of the invasive Indo-Pacific lionfish Pterois volitans in the Bahamas.

Abstract: LionWsh are popular aquarium Wsh from the Indo-PaciWc that have invaded the western Atlantic. Two species, Pterois volitans and P. miles, were well established along the United States east coast before the Wrst lionWsh were reported from the Bahamas in 2004, where they quickly dispersed throughout the archipelago by 2007. The source of the Bahamian lionWsh invasion has been in ques- tion because of the hypothesized low connectivity between Florida and Bahamas reef species as well as the temporal lag in their arrival in the Bahamas. Mitochondrial control region haplotypes (680 bp) were determined and analyzed for lionWsh specimens from the Bahamas, North Carolina, and two sites within their native range (Indonesia and the Philippines). Exact tests, pairwise F st and AMOVA analy- ses all showed no signiWcant diVerentiation between the Bahamas and North Carolina specimens. The similarity between the Bahamas and North Carolina lionWsh was also reXected in a minimum spanning network and neighbor- joining distance tree generated from the data. Sequence analyses also revealed the presence of only Pterois volitans, as no P. miles were detected in the Bahamian sample. These results indicate that the source of the Bahamian lion- Wsh is egg and larval dispersal from the United States east coast population, and support previous models of reef Wsh dispersal that suggest a low level of connectivity between the Bahamas and east coast of Florida.

A MOLECULAR PHYLOGENY OF THE GELIDIALES (RHODOPHYTA) BASED ON ANALYSIS OF PLASTID rbcL NUCLEOTIDE SEQUENCES1

Abstract: Parsimony analyses of rbcL nucleotide. sequences were used to develop hypotheses of relationships among taxa in the taxonomically difficult order Celidiales including species from seven currently recognized genera: Capreolia, Gelidiella, Gelidium, Onikusa, Pterocladia, Ptilophora, and Suhria. Nucleotide. sequences of rbcL from red algae are variable and provide a large number of informative characters for phylogenetic analysis, yet the absence of insertion/deletion mutations allows for the unambiguous alignment of sequences. Species were resolved into 10 well-.supported major clades representing genera and species complexes. The topological positions of these 10 clades within trees are also well supported and indicate that Gelidium and Pterocladia as currently circumscribed are not monophyletic. These results call for a revision of the classification of the Gelidiales.

Distribution and Identification of an Invasive Gracilaria Species that is Hampering Commercial Fishing Operations in Southeastern North Carolina, USA

Abstract: A newly abundant Gracilaria species in the sounds of southeastern North Carolina has become a problem for commercial fishing and industries drawing water from the lower Cape Fear River. DNA sequence analyses have shown that this species is Gracilaria vermiculophylla, a taxon originally described from East Asia. Surveys for G. vermiculophylla have shown that it has a discontinuous distribution in the sounds of southeastern North Carolina, and suggest that it is spreading. Gracilaria vermiculophylla meets 6 of the 10 criteria used to help identify invasive species in that it has only recently appeared in southeastern North Carolina; is associated with human mechanisms of dispersal; has a restricted distribution; has disjunct populations in isolated oceans; no means of active dispersal, and an exotic evolutionary origin. The species may also meet two additional criteria as its local range is believed to be expanding, and it is filling a previously unoccupied seasonal niche. These factors taken together strongly suggest that G. vermiculophylla is an invasive species in southeastern North Carolina.

Effects of life history traits and sampling strategies on genetic diversity estimates obtained with RAPD markers in plants

Abstract: A compilation of studies using RAPD markers for evaluating population differentiation resulted in 78 estimates of AMOVA-derived Φ ST and 31 estimates of Nei's G ST , as well as in 41 estimates of Nei's within-population diversity. In outcrossing taxa, estimates of between-population diversity were closely correlated with maximum geographic distance between sampled populations. A corresponding association was not found in selfing taxa. These results suggest that RAPD can be a sensitive method for detection of genetic structuring according to the isolation-by-distance model. However, it also means that sampling strategies, as applied in individual studies, can seriously influence the resulting estimates of between-population diversity. Other sampling strategies, like number of plants per population and number of scored polymorphic markers, do not seem to impart any serious artefacts. As previously verified with allozyme data, RAPD markers showed that long-lived, outcrossing, late successional taxa retain most of their genetic variability within populations. By contrast, annual, selfing and/or early successional taxa allocate most of the genetic variability among populations. Estimates for between- and within-population diversity, respectively, proved to be negatively correlated, as previously reported for allozyme data. The only major discrepancy between allozymes and RAPD markers concerns geographic range; within-population diversity was strongly affected by distributional range of the investigated species in the allozyme data but not in the RAPD data. Moreover, RAPD-based values for between-population diversity increased with increasing distributional range whereas the opposite has been reported in a large allozyme data compilation. Contrary to allozymes, RAPD marker-derived within-population diversity is probably therefore not a very good predictor of total species genetic diversity.

Sympatric speciation in phytophagous insects: moving beyond controversy?

Abstract: ▪ Abstract Sympatric speciation is the splitting of one evolutionary lineage into two without the occurrence of geographic isolation. The concept has been intimately tied to entomology since the 1860s, when Benjamin Walsh proposed that many host-specific phytophagous insects originate by shifting and adapting to new host plant species. If true, sympatric speciation would have tremendous implications for our understanding of species and their origins, biodiversity (25–40% of all animals are thought to be phytophagous specialists), insect-plant coevolution, community ecology, phylogenetics, and systematics, as well as practical significance for the management of insect pests. During much of the twentieth century sympatric speciation was viewed as much less plausible than geographic (allopatric) speciation. However, empirical field studies, laboratory experiments, developments in population genetics theory, and phylogenetic and biogeographic data have all recently combined to shed a more favorable light on t...

Applying DNA barcoding to red macroalgae: a preliminary appraisal holds promise for future applications

Abstract: Marine macroalgae, especially the Rhodophyta, can be notoriously difficult to identify owing to their relatively simple morphology and anatomy, convergence, rampant phenotypic plasticity, and alternation of heteromorphic generations. It is thus not surprising that algal systematists have come to rely heavily on genetic tools for molecular assisted alpha taxonomy. Unfortunately the number of suitable marker systems in the three available genomes is enormous and, although most workers have settled on one of three or four models, the lack of an accepted standard hinders the comparison of results between laboratories. The advantages of a standard system are obvious for practical purposes of species discovery and identification; as well, compliance with a universal marker, such as cox1 being developed under the label ‘DNA barcode’, would allow algal systematists to benefit from the rapidly emerging technologies. Novel primers were developed for red algae to PCR amplify and sequence the 5′ cox1 ‘barcode’ region and were used to assess three known species-complex questions: (i) Mazzaella species in the Northeast Pacific; (ii) species of the genera Dilsea and Neodilsea in the Northeast Pacific; and (iii) Asteromenia peltata from three oceans. These models were selected because they have all caused confusion with regards to species number, distribution, and identification in the field, and because they have all been studied with molecular tools. In all cases the DNA barcode resolved accurately and unequivocally species identities and, with the enhanced sampling here, turned up a variety of novel observations in need of further taxonomic investigation.

The Cell Wall

Abstract: Secondary thickening in pteridophytes.-The known cases of secondary thickening in recent Pteridophyta have been brought together by HILL23 in a useful resume. After stating the criteria for secondary growth, Botrychium, which has a distinct cambium, and Ophioglossum, which lacks a definite layer, are described, followed by Angiopteris and Marattia, in which a cambium forms a few xylem elements. CORMACK'S observations on the secondary wood in the nodes of Equisetum are cited, though no reference is made to the cambium in the young cone as reported by J]FFREY.24 The other cases of secondary growth include Psilotum, Selaginella spinulosa, and several species of Isoetes, especially I. hystrix, which may show a cambium outside the vascular cylinder.-M. A.