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The process of ecological speciation has not been considered in great detail. We can gain a new perspective on this process by viewing new species as successful invaders, and by using invasive species as a model system for understanding the early stages of speciation. I propose that ecological species may be polyphyletic, and undergo genetic differentiation early in their histories. I also note that there are formidable genetic obstacles to ecological speciation. The rate of speciation is dependent on geographical and ecological variables, as are rates of invasions by exotic species. Ecological opportunity is the key for speciation and invasion; and it is most often found on young islands. In general there are no traits that presage which exotic species will be the best invaders of natural areas. Thus it would be difficult to predict which traits foster ecological speciation. Herbaceous plants are more invasive and have higher rates of diversification than woody plants.
Restriction digest patterns from 18S–26S nuclear ribosomal DNA internal transcribed spacers (ITS) were employed to investigate delineation between the morphologically similar moss species Leucobryum glaucum, L. juniperoideum, and L. albidum. Discriminant analysis allowed assignment of specimens to haplotypes based on their morphological features and supported the recognition of L. glaucum and L. albidum. In contrast, L. albidum and L. juniperoideum both corresponded to the same haplotype. Many populations could be readily assigned to either L. glaucum or L. albidum by their morphological features. However, morphological variation between these two species was continuous and one of the ITS haplotypes could not be unambiguously characterized by its morphology. Genetically and morphologically identifiable specimens of L. albidum were sampled in Europe and North America, in contrast to the traditional interpretation of L. albidum as a North American endemic. Although L. albidum seems to have a more southern-Atlantic distribution pattern than L. glaucum, the two species occupy broadly overlapping geographic ranges and were sometimes found intermixed.
We sequenced chloroplast DNA from the matK, rbcL, and rpl16 regions to infer interrelationships within the pinyon pines (Pinus subsections Cembroides and Nelsoniae). Pinyons, together with subsections Balfourianae, Gerardianae, and Krempfianae have been classified in section Parrya, characterized by a dorsal umbo (raised area) on the ovulate cone scale. All three cpDNA regions support the separation of pinyon pines into subsection Cembroides and a monotypic subsection Nelsoniae and indicate that section Parrya is paraphyletic. We propose restricting section Parrya to the North American clade (subsections Cembroides, Nelsoniae, and Balfourianae) and transferring the Asian subsections Gerardianae and Krempfianae to section Quinquefolius (generally known as section Strobus). The data moderately support a sister relationship between subsections Nelsoniae and Balfourianae, rendering the pinyons paraphyletic. Several monophyletic groups can be identified within subsection Cembroides, including a sister relationship between P. maximartinezii and P. pinceana, which is at variance with morphological cladistic analyses. In general, relationships inferred from cpDNA are less consistent with morphological evidence than with internal transcribed spacer region data, despite paralogy in the latter marker.
Morphological and phytogeographical data support the recognition of three distinct species in the genus Brachyelytrum: B. japonicum, B. erectum, and B. aristosum. Brachyelytrum japonicum is confined to eastern Asia and is characterized by narrow leaf blades (0.5–0.8 cm wide), long lower glumes (0.2–2.0 mm long), and long rachillas (6.8–8.8 mm long). Brachyelytrum erectum is distributed throughout much of the eastern United States, from northwestern Minnesota south to central Louisiana, east to northern Florida and north to northeastern New York. Brachyelytrum erectum is characterized by long hispid hairs (0.2–0.9 mm long) on the veins of the lemma, wide lemmas (0.8–1.8 mm wide), and a conspicuous lemma mid-vein. Brachyelytrum aristosum has a more northern distribution, occurring in southern Canada from southern Ontario to Newfoundland, the northern adjacent United States and through the Appalachian mountains to northwestern North Carolina. Brachyelytrum aristosum is characterized by short scaberulous hairs (0.06–0.2 mm long) on the lemma and narrow lemmas (0.7–1.4 mm wide) that are weakly veined. The distinctiveness of B. erectum and B. aristosum is further supported by amplified fragment length polymorphism (AFLP) data. We include a key to the taxa, synonymies, descriptions, and representative specimens. This study represents a recent monographic study of an eastern North American and eastern Asian disjunct genus.
The first extensive cpDNA phylogeny of African Begonia was estimated with chloroplast trnL intron DNA sequences. A total of 81 Begonia species was sampled and analyzed using parsimony and maximum likelihood methods. Analyses showed well-resolved sectional relationships, but little resolution at the base of the phylogeny. Malagasy species of Begonia formed a monophyletic group, as were the mainland African wingless fleshy-fruited species with the exception of section Mezierea. Species in section Mezierea are not as closely related to other wingless fleshy-fruited species as once thought. The section is polyphyletic, with the Malagasy members of the section nested within the Malagasy clade. The phylogenetic position of species in section Mezierea demonstrates that fleshy fruits have evolved at least twice in African Begonia. The terrestrial, 2-tepaled, West and Central African yellow-flowered begonias and their related species are also monophyletic, with the monotypic section Cristasemen and B. iucunda holding a solitary, basal position. The predominantly East and South African species in sections Rostrobegonia, Augustia, Sexalaria, and Peltaugustia show greater affinity with Asian and American, rather than other African begonias, and are interdigitated among them; therefore African Begonia are not monophyletic. The trnL intron is a useful region for identifying monophyletic groups across the whole genus and breaking up the genus into workable units. This demonstrates the value of reconstructing phylogenies of large genera in order to achieve more stable classifications.
The circumscription of Oxylobium and related genera has been problematic for nearly 200 years. Traditional definitions of genera in the group have relied on morphological features of the leaves, flower, and fruit that overlap extensively between genera. Therefore sequences of cpDNA (trnL-F intron and spacer) and nrDNA (ITS) were used to estimate the phylogeny of the group in an attempt to redefine the genera as monophyletic groups. Oxylobium sens. str. was found to be a well supported clade in both data sets, with the inclusion of Mirbelia oxylobioides. No other genus in the group was supported by these data, except Gastrolobium sens. lat. Some species groups within Chorizema, Mirbelia, and Podolobium were supported but relationships among these, Oxylobium and Gastrolobium differed significantly between the chloroplast and nuclear data sets. No group supported by the molecular data had a morphological synapomorphy, not even Oxylobium or Gastrolobium. Therefore it may be necessary to adopt a much broader generic concept in this group than has been done previously. Incongruence between the two molecular data sets, and very short internal basal branches in both, suggest a rapid early radiation in this group, possibly combined with hybridization and lineage sorting.
Four species were discerned in a complex of Galphimia Cav. (Malpighiaceae) from the Pacific slope of Mexico. Three are newly described (G. arenicola, G. mexiae, and G. radialis). One is transferred from Thryallis L. (nom. rejic.) to Galphimia, and the new combination G. langlassei is proposed.
A molecular phylogenetic analysis of the Andean genus Tarasa (Malvaceae) and related genera yielded unexpected results regarding generic boundaries, the origins of polyploidy, and the morphological attributes of the polyploid taxa. The polyploid species of Tarasa are particularly unusual because they have life histories and floral morphologies that contradict two traditional polyploid dogmas: they are annuals and have smaller floral features (including pollen) than the diploid species. Typically, polyploids are perennial and larger than their parents. Nuclear (ITS1, 5.8S, and ITS2) and chloroplast (psbA-trnH and trnT-trnL spacers, matK-3′ trnK intron) sequence data were used to reconstruct independent phylogenies to test the monophyly of the genus, determine its sister group(s), and investigate the origin of the polyploid species. Neither the nuclear nor the chloroplast phylogeny supports monophyly of Tarasa as currently circumscribed. The high Andean genus Nototriche, the North/South American disjunct genus Sphaeralcea, and Malacothamnus chilensis are placed within the Tarasa clade. The polyploid species of Tarasa are not monophyletic and thus have been generated multiple times. These findings suggest that the unusual morphological features of the tetraploids are the result of convergent evolution and not shared ancestry.
Adelobotrys (Merianieae: Melastomataceae) is a neotropical, primarily Amazonian genus of 23 lianas and eight arborescent species. A cladistic analysis was performed to test the monophyly of Adelobotrys, discover its synapomorphies, and clarify its internal relationships. The results also allowed a preliminary appraisal of generic limits within Merianieae. For the analysis, 117 morphological characters were coded for 53 ingroup taxa (52 of Adelobotrys plus Sarmentaria decora) and 12 outgroup species from the genera Meriania, Graffenrieda, Axinaea, Centronia, Phainantha, Behuria, Huberia, Pachyloma, and Pternandra. The analysis resulted in a single most parsimonious tree. The result suggests that Adelobotrys is polyphyletic. However, species that fall within the original circumscription of the genus form a well-supported monophyletic group. This group of lianoid species with narrow hypanthia; 5-locular ovaries; short fruiting pedicels; urceolate to globose fruiting hypanthia; elongated, winged seeds; and a vestiture of malpighian hairs is here termed Adelobotrys sensu stricto. Several well-defined lineages are recognized within Adelobotrys s.s., although most of them have only weak support. Purported problems persist with circumscriptions of merianean genera, in particular Meriania.
Cornus eydeana Q. Y. Xiang & Y. M. Shui, a new species of cornelian cherry, Cornus subg. Cornus, is described from southeastern Yunnan, China. The new species resembles other cornelian cherries in having umbellate inflorescences subtended by two pairs of scale-like bracts and fruit with cavity-filled stones. However, it differs from them by the following combination of characters: evergreen habit, leathery leaves with three or four secondary veins, and densely flowered, long pedunculate inflorescences with perfect flowers. Morphologically, the species appears most similar to the African species C. volkensii Harms, but pollen morphology and geographic distributions suggest a closer affinity with the Eurasian species. The discovery of this species has significant implications for our understanding of the systematics and evolution of the cornelian cherry group.
Nasa Weigend ser. Carunculatae (Urb. & Gilg) Weigend is revised, four species are recognized, and one, Nasa usquiliensis Weigend, T. Henning & C. Schneider described as new to science. The species of this group are restricted to steep scree slopes in Peru and southern Ecuador and have patchy distributions at elevations of 2200–3500 m. All species share shrubby habit with ligneous stems and deciduous foliage. These characters in combination with clawed, spreading petals and bicolored nectar scales are unique in Nasa. Branched root-tubers are reported from N. carunculata, which is the first report of tuberous storage roots in the genus. Species delimitation is primarily based on habit, trichome characters, flower size, petal color and shape, and the morphology of the floral scales.
Two non-coding DNA regions from both the chloroplast genome (trnL intron, trnL–trnF IGS, trnT–trnL IGS) and nuclear ribosomal genomes (ITS1 and ITS2) were sequenced in the genus Keckiella and allied genera (Penstemon, Chelone, and Nothochelone) to determine which, if any, of these sequences contained sufficient variability to resolve the seven species of Keckiella. The trnL intron contained almost no signal. However, the trnT–trnL chloroplast IGS region and the nuclear ribosomal sequences were capable, to some extent, of resolving the phylogeny of Keckiella. The nrDNA ITS sequences contained slightly more variability than the chloroplast noncoding region. When combined, these non-coding sequences generated a relatively robust and resolved cladogram. Keckiella rothrockii is clearly indicated as the most basal species of the genus, and the remaining taxa appear to belong to two well-supported clades. The first contains the sister taxa K. antirrhinoides and K. cordifolia. The second contains K. breviflora, K. ternata, K. corymbosa, and K. lemmonii. The nodes of the latter three species are not as strongly supported.
Because recent molecular studies, based on multiple data sets from all three plant genomes, have indicated mutually congruent, well-resolved, and well-supported relationships within Convolvulaceae (the morning-glory family), a formal reclassification of this family is presented here. Convolvulaceae, a large family of worldwide distribution, exhibiting a rich diversity of morphological characteristics and ecological habitats, are now circumscribed within twelve tribes. A key to these tribes of Convolvulaceae is offered. The group of spiny-pollen bearing Convolvulaceae (forming “Echinoconiae”) and tribe Cuscuteae are retained essentially in their traditional sense, Cresseae are circumscribed with only minor modifications, Convolvuleae and Erycibeae are recognized in a restricted sense, while Dichondreae and Maripeae are expanded. Also, to produce a tribal taxonomy that better reflects phylogenetic relationships, the concept of Poraneae is abandoned as artificial, three new tribes are recognized (Aniseieae, Cardiochlamyeae, and Jacquemontieae), and a new tribal status is proposed for the Malagasy endemic Humbertia (Humbertieae). “Merremieae” are tentatively retained even though the monophyly of this tribe is not certain. In addition to the formal classification, we provide clade name definitions for the family as well as for most of the clades recognized presently as tribes. Also, five well-supported clades that are not assigned formal ranks are recognized and their names defined. The reevaluation of traditional taxonomic characters reveals that many homoplasious characters were emphasized in previous classifications, resulting in formal recognition of non-monophyletic groups. Putative morphological synapomorphies for many clades discovered through molecular cladistic analyses are discussed. However, the morphology of several clades that are well-supported by DNA evidence remains poorly understood, creating further challenges for future studies in Convolvulaceae.