Jennifer L. Trusty

Molecular phylogenetics of the Macaronesian‐endemic genus Bystropogon (Lamiaceae): palaeo‐islands, ecological shifts and interisland colonizations

A molecular phylogenetic study of Bystropogon L’Hèr. (Lamiaceae) is presented. We performed a cladistic analysis of nucleotide sequences of the internal transcribed spacers (ITS), of the nuclear ribosomal DNA, and of the trnL gene and trnL‐trnF intergenic spacer of the chloroplast DNA. Bystropogon odoratissimus is the only species endemic to the Canary Islands that occurs in the three palaeo‐islands of Tenerife. This species is not part of an early diverging lineage of Bystropogon and we suggest that it has a recent origin. This phylogenetic pattern is followed by most of the species endemic to the palaeo‐islands of Tenerife. The two sections currently recognized in Bystropogon form two monophyletic groups. Taxa belonging to the section Bystropogon clade show interisland colonization limited to the Canary Islands with ecological shifts among three ecological zones. Taxa from the section Canariense clade show interisland colonization both within the Canary Islands and between the Canary Islands and Madeira. Speciation events within this clade are mostly limited to the laurel forest. The genus has followed a colonization route from the Canaries towards Madeira. This route has also been followed by at least five other plant genera with species endemic to Macaronesia. Major incongruences were found between the current infrasectional classification and the molecular phylogeny, because the varieties of Bystropogon origanifolius and Bystropogon canariensis do not form two monophyletic groups. The widespread B. origanifolius appears as progenitor of the other species in section Bystropogon with a more restricted distribution.

Using molecular phylogenies to test phytogeographical links between East/South Africa-Southern Arabia and the Macaronesian islands-a review, and the case of Vierea and Pulicaria section Vieraeopsis (Asteraceae)

We undertook a phylogenetic analysis of sequences of the internal transcribed spacers (ITS) of the nuclear ribosomal DNA to test the hypothesis that the Canary Island genus Vierea is closely related to Pulicaria sect. Vieraeopsis, a taxon with four species restricted to Socotra and Southern Arabia. The ITS tree does not support this relationship, although many of the nodes were weakly supported (bootstrap value below 75%). Vierea is sister to the Mediterranean genus Perralderia (bootstrap support 74%). We suggest that morphological similarities between Vierea and Pulicaria sect. Vieraeopsis are due mostly to morphological convergence. It is thus concluded that these two taxa do not share a common history. A review of molecular phylogenetic studies of taxa considered to represent putative biogeographical links between Macaronesia and Southern Arabia and/or distant regions of Africa, is also presented. With a few exceptions most of these putative relationships are not supported by molecular phylogenies. Additional cladistic studies are needed for at least 15 genera or sections with a predominant disjunct phytogeographical distribution between Macaronesia, East/South Africa and Southern Arabia.

Using Molecular Data to Test a Biogeographic Connection of the Macaronesian Genus Bystropogon (Lamiaceae) to the New World: A Case of Conflicting Phylogenies

Abstract Bystropogon (Lamiaceae) is endemic to the Macaronesian Islands and represents the best-known example of a putative phytogeographic connection between these islands and the New World. Previous morphological taxonomic studies suggested that this genus is closely related to the western South American Minthostachys. Phylogenetic analyses of nucleotide sequences of the internal transcribed spacers and 5.8S subunit of nuclear ribosomal DNA and the trnL gene and trnL-trnF spacer of the chloroplast genome for 33 of the 72 genera in the Mentheae tribe were performed. Maximum parsimony analysis of the combined data set resulted in 63 most parsimonious trees. The strict consensus tree of this analysis shows with moderate bootstrap support (74%) that Bystropogon is sister to the Old World taxa Acinos, Ziziphora, and Clinopodium vulgare. When analyzed separately, the ITS and trnL/F data sets do not agree as to the sister group to Bystropogon, although none supports a sister relationship with Minthostachys. The cpDNA phylogeny strongly supports a relationship of Bystropogon with a clade of New World mint taxa (90% bootstrap value). Due to the apparent conflict between the chloroplast and nuclear characters observed in the phylogenies, we are not certain of the true biogeographic relationship of Bystropogon. Finally, in all analyses, all of the Mentheae genera sampled in this study form a monophyletic group (100% bootstrap value) and a derived clade of ten New World genera is found. These results contribute to our understanding of generic relationships within the tribe.

MOLECULAR PHYLOGENETICS OF THE CARIBBEAN GENERA RHODOGERON AND SACHSIA (ASTERACEAE)

Rhodogeron Griseb. and Sachsia Griseb. (Asteraceae) are two Caribbean genera. Rhodogeron is restricted to Cuba, whereas Sachsia is found in Cuba, the Bahamas, south Florida, and Hispaniola. A phylogenetic study of nucleotide sequences of the chloroplast gene ndhF and of the internal transcribed spacers (ITS) of the nuclear ribosomal DNA shows that these two genera form a monophyletic group. The ndhF phylogeny places Rhodogeron and Sachsia within the tribe Plucheeae but with only very weak bootstrap support (59%). The ITS phylogeny indicates the serpentine areas of Cuba are the ancestral habitat for these genera, with a colonization route from Cuba toward the Bahamas and Florida. In addition, this study supports previous taxonomic treatments that considered Sachsia divaricata Griseb. and Sachsia polycephala Griseb. to be conspecific. Finally, Rhodogeron is the sister taxon to Sachsia, and we propose that it should be maintained as a distinct monospecific genus.

Invasive Wisteria in the Southeastern United States: genetic diversity, hybridization and the role of urban centers

The increasing numbers and negative impacts of invasive species have prompted research on the relationship between human activities and the success of invasive horticultural plants. In this study, we use population genetic relationships to model the escape of a common garden vine, exotic Wisteria, into natural habitats. Urban and naturalized Wisteria populations in Charleston, South Carolina and Tallahassee, Florida were investigated using a combination of chloroplast, mitochondrial and nuclear DNA markers. Fifty-nine of 72 (81.9%) Wisteria collections were hybrids of Wisteria sinensis and W. floribunda. Chi-square analysis of the distribution of shared W. floribunda haplotypes among naturalized and urban populations supports the relationship of time with invasion success. Naturalized populations were more similar to those in historic neighborhoods. The most common haplotype, F1, was encountered 22 times but its distribution was not significantly different between urban and naturalized populations. In contrast, a significantly higher proportion of haplotype F2 found in naturalized populations suggests that selection may also be acting within these populations. Finally, due to extensive human dispersal, there is no relationship between genetic distance and geographical distance among the populations sampled. We conclude that Wisteria’s long history of horticulture, rampant hybridization, and human-aided dispersal are all implicated in the successful ability of these plants to invade natural habitats throughout the USA.

Ex Situ Conservation of the Federally Endangered Plant Species Clematis socialis Kral (Ranunculaceae)

ABSTRACT: The Center for Plant Conservation (CPC) has created sampling guidelines for the ex situ conservation of rare plant species. These guidelines estimate the number of individuals needed to maximize the genetic diversity of the collection according to population genetic theory. For many clonal plant species, knowledge of the number of unique individuals is not easily discerned and application of these guidelines must be based on molecular genetic data. In this paper, we discuss the steps taken in order to meet CPC guidelines for the conservation of a rare clonal plant, Clematis socialis. Due to limited seed availability, methods were developed for successful in vitro propagation and cryopreservation of C. socialis shoot tips. Inter-simple sequence repeat (ISSR) analysis identified fifteen unique genotypes in the ex situ in vitro collection. One genotype in this collection has been conserved from a population that is now presumed extinct. Although the initial sampling protocol managed to capture considerable genetic diversity, an additional 97 genotypes are needed to meet CPC guidelines. The information and experience gained through the initial C. socialis ex situ conservation efforts form the basis for a strategy to improve ex situ conservation activities for this endangered species. We recommend that additional in vitro collections be made from each of the five extant populations and placed in cryostorage.

GALAPAGOS AND COCOS ISLANDS: GEOGRAPHICALLY CLOSE, BOTANICALLY DISTANT

We investigated whether the plants of the Galápagos Archipelago and Cocos Island, which are each other’s closest neighboring insular systems, show any such sister relationships. Five genera of vascular plants have endemics in both archipelagos, including plants with different life histories and dispersal mechanisms: tree ferns, epiphytes, trees, herbs, and shrubs, with adaptations for dispersal by wind or birds (two genera each) or with no obvious dispersal adaptation (one genus). We obtained molecular phylogenies for these genera to test the hypothesis of phytogeographical links between the islands. The phylogenies for all five genera were not consistent with this hypothesis, but they supported floristic studies in revealing no direct phytogeographical links between the islands. We attribute this lack of floristic affinity primarily to air and ocean circulation patterns that limit dispersal between Galápagos and Cocos and to a low frequency of interisland bird movements. There are also major ecological differences between them, and Cocos Island is quite small, which limits the chance of random dispersal events and subsequent establishment.

Clonal diversity and structure in the endangered Alabama leather flower Clematis socialis Kral (Ranunculaceae)1

Abstract Effective conservation strategies for rare clonal plant species require knowledge of their population-level genetic diversity. We used data from genetic markers (Inter-Simple Sequence Repeat (ISSR), and Sequence Characterized Amplified Region (SCAR)) to estimate the number of genetically distinct individuals and the spatial extent of such genets within study populations of the federally endangered Alabama leather flower (Clematis socialis). We found high clonal diversity in C. socialis in spite of the limited seed set and seedling recruitment previously reported for this species. ISSR analyses of plants from the six known populations of C. socialis yielded 54 distinct multilocus genotypes from 74 sampled plants. Although the populations are separated by an average of 60 km, related genotypes were relatively evenly distributed among all populations. Within populations, the majority of C. socialis genets extended less than 1 m in diameter, but two large individuals spanning 11 m were identified. Based on observed growth data, the 11 m result suggests that C. socialis genets can live for at least 55 years. The size and relative longevity of C. socialis genets have likely slowed the loss of genetic diversity in this rare, clonal species. Additionally, we estimate that population loss and fragmentation of C. socialis populations have been relatively recent: within two to three generations. Finally, our data indicate that without sexual reproduction, rare genets are likely to go extinct and genetic diversity will decline unless populations are managed to prevent this outcome. In order for conserved populations to persist, research on how management activities simultaneously affect sexual and clonal reproduction in these populations is necessary.