Warren L. Wagner

Fossil evidence for a diverse biota from Kaua`i and its transformation since human arrival

Coring and excavations in a large sinkhole and cave system formed in an eolianite deposit on the south coast of Kaua‘i in the Hawaiian Islands reveal a fossil site with remarkable preservation and diversity of plant and animal remains. Radiocarbon dating and investigations of the sediments and their fossil contents, including diatoms, invertebrate shells, vertebrate bones, pollen, and plant macrofossils, provide a more complete picture of prehuman ecological conditions in the Hawaiian lowlands than has been previously available. The evidence confirms that a highly diverse prehuman landscape has been completely transformed, with the decline or extirpation of most native species and their replacement with introduced species. The stratigraphy documents many late Holocene extinctions, including previously undescribed species, and suggests that the pattern of extirpation for snails occurred in three temporal stages, corresponding to initial settlement, late prehistoric, and historic impacts. The site also records land-use changes of recent centuries, including evidence for deforestation, overgrazing, and soil erosion during the historic period, and biological invasion during both the Polynesian and historic periods. Human artifacts and midden materials demonstrate a high-density human presence near the site for the last four centuries. Earlier evidence for humans includes a bone of the prehistorically introduced Pacific rat (Rattus exulans) dating to 822 yr BP (calendar year [cal yr] AD 1039–1241). Vegetation at the site before human arrival consisted of a herbaceous component with strand plants and graminoids, and a woody component that included trees and shrubs now mostly restricted to a few higher, wetter, and less disturbed parts of the island. Efforts to restore lowland areas in the Hawaiian Islands must take into account the evidence from this study that the prehuman lowlands of dry leeward Kaua‘i included plants and animals previously known only in wetter and cooler habitats. Many species may be restricted to high elevations today primarily because these remote locations have, by virtue of their difficult topography and climate, resisted most human-induced changes more effectively than the coastal lowlands.

Family-level relationships of Onagraceae based on chloroplast rbcL and ndhF data

Despite intensive morphological and molecular studies of Onagraceae, relationships within the family are not fully understood. One drawback of previous analyses is limited sampling within the large tribe Onagreae. In addition, the monophyly of two species-rich genera in Onagreae, Camissonia and Oenothera, has never been adequately tested. To understand relationships within Onagraceae, test the monophyly of these two genera, and ascertain the affinities of the newly discovered genus Megacorax, we conducted parsimony and maximum likelihood analyses with rbcL and ndhF sequence data for 24 taxa representing all 17 Onagraceae genera and two outgroup Lythraceae. Results strongly support a monophyletic Onagraceae, with Ludwigia as the basal lineage and a sister-taxon relationship between Megacorax and Lopezia. Gongylocarpus is supported as sister to Epilobieae plus the rest of Onagreae, although relationships within the latter clade have limited resolution. Thus, we advocate placement of Gongylocarpus in a monogeneric tribe, Gongylocarpeae. Most relationships within Onagreae are weakly resolved, suggesting a rapid diversification of this group in western North America. Neither Camissonia nor Oenothera appears to be monophyletic; however, increased taxon sampling is needed to clarify those relationships. Morphological characters generally agree with the molecular data, providing further support for relationships.

Origins of Dioecy in the Hawaiian Flora

Because of its presumed high levels of dioecy (separate male and female plants), study of the native Hawaiian angiosperm flora has been important in development of many hypotheses about conditions favoring the evolution of dioecy. The importance of ecological correlates with dioecy has proven difficult to assess, however, because of lack of data on the origins of dioecy in the Hawaiian Islands. Clearly, these correlations are of greater interest in taxa where dioecy evolved in the Hawaiian Islands (autochthonous evolution of dioecy) than in taxa that are the result of dioecious colonists with subsequent speciation in the Hawaiian Islands. Because the Hawaiian flora is small and extremely isolated, colonists can be identified and their breeding systems hypothesized, thus allowing inferences on the origins of dioecy. Using current taxonomic information, the incidence of dioecy in native Hawaiian angiosperm species is 14.7%, lower than previous estimates, but still the highest of any known flora worldwide. Ten percent of the colonists were sexually dimorphic (dioecious, gynodioecious, polygamodioecious, and subdioecious), and over half (55.2%) of current dimorphic species are in lineages arising from dimorphic colonists, showing that dimorphism is high in part because colonists were dimorphic. Autochthonous evolution of dimorphism occurred in at least 12 lineages (e.g., hermaphroditic colonists of Bidens (Asteraceae), the Hawaiian Alsinoideae (Caryophyllaceae), and Hedyotis (Rubiaceae) led to species-rich lineages that include many dimorphic species). One-third (31.8%) of current dimorphic species are in lineages arising from monomorphic colonists. Dioecy in the Hawaiian Islands is a result of both dimorphic colonists as well as evolution of dioecy in Hawaiian lineages from hermaphroditic colonists. The high incidence of dimorphism is not because dimorphic colonists evolved more species per colonist than monomorphic colonists. Detailed studies of individual lineages are critical to elucidate causal factors in the evolution of dioecy.

SPECIATION IN HAWAIIAN ANGIOSPERM LINEAGES: CAUSE, CONSEQUENCE, AND MODE

Abstract The biota of Hawaiian Islands is derived entirely from long distance dispersal, often followed by in situ speciation. Species descended from each colonist constitute monophyletic lineages that have diverged to varying degrees under similar spatial and temporal constraints. We partitioned the Hawaiian angiosperm flora into lineages and assessed morphological, ecological, and biogeographic characteristics to examine their relationships to variation in species number (S). Lineages with external bird dispersal (through adhesion) were significantly more species‐rich than those with abiotic dispersal, but only weakly more species‐rich than lineages with internal bird dispersal (involving fleshy fruits). Pollination mode and growth form (woody vs. herbaceous) had no significant effect on S, in contrast to studies of angiosperm families. S relates positively to the geographic and ecological range size of whole lineages, but negatively to local abundance and mean range sizes of constituent species. Species‐rich lineages represent a large proportion of major adaptive shifts, although this appears to be an artifact of having more species. Examination of 52 sister species pairs in numerous lineages provides evidence for allopatric (including peripheral isolates) and parapatric (ecological) modes, with 15 cases of each. Although postspeciational dispersal may obscure these modes in many of the remaining cases, instances of sympatric and hybrid speciation are also discussed. Because speciation is both a consequence and a cause of ecological and biogeographic traits, speciation mode may be integral to relationships between traits. We discuss the role of speciation in shaping the regional species pool.

Biogeographical and Ecological Correlates of Dioecy in the Hawaiian Flora

The angiosperm flora of the Hawaiian Islands, with its high incidence of dioecy, has been central in development of hypotheses about the evolution of dioecy. Based on a recent taxonomic treatment of the Hawaiian angiosperm flora, we analyzed biogeo- graphic patterns of dioecy as well as the association of dioecy with ecological traits po- tentially important in the evolution of dioecy for native current species and genera. We also analyzed patterns for presumed colonists of the flora to control better for phylogenetic patterns in these traits. Dioecy is associated with woodiness, especially trees; however, this pattern does not hold for gynodioecy. Within woody species, dimorphism (dioecy, gyno- dioecy, subdioecy, polygamodioecy) is associated with mesic habitats and occurs more frequently in species with lowland and lowland-montane distributions. In contrast, in the endemic Hawaiian Alsinoideae (Schiedea and Alsinidendron) and in Bidens (two groups with autochthonous evolution of dimorphism), dimorphism is associated with more xeric habitats, and for the former group, with wind pollination. For the entire angiosperm flora, dimorphic species are associated with flowers that are small and green. Woody dioecious species and genera are disproportionately associated with wind pollination; hermaphroditic species are disproportionately bird pollinated primarily because of one species-rich lineage in the Campanulaceae. There was no association of dimorphism and pollinator type for colonists. Because of a few species-rich lineages, dimorphism is associated with dry fruits at the specific level, but at the generic level and for colonists, dimorphism is associated with fleshy fruits. Dioecious and gynodioecious species are found more often on older islands, a result of speciation of dimorphic colonists as well as autochthonous evolution of dimorphism. Single- island endemism is not associated with dioecy in the flora as a whole or with dimorphism within lineages evolving dimorphism autochthonously; thus Bakers law is not supported within the Hawaiian Islands. Because the Hawaiian angiosperm flora originated from a minimum of only 291 colonists, many of the associations of dimorphism with ecological traits occur because of the influence of only a few species-rich lineages. Better knowledge of phylogenetic patterns and further ecological studies, particularly within those groups evolving dioecy autochthonously, are needed to determine causality.

A Comparative Study in Ancestral Range Reconstruction Methods: Retracing the Uncertain Histories of Insular Lineages

Island systems have long been useful models for understanding lineage diversification in a geographic context, especially pertaining to the importance of dispersal in the origin of new clades. Here we use a well-resolved phylogeny of the flowering plant genus Cyrtandra (Gesneriaceae) from the Pacific Islands to compare four methods of inferring ancestral geographic ranges in islands: two developed for character-state reconstruction that allow only single-island ranges and do not explicitly associate speciation with range evolution (Fitch parsimony [FP; parsimony-based] and stochastic mapping [SM; likelihood-based]) and two methods developed specifically for ancestral range reconstruction, in which widespread ranges (spanning islands) are integral to inferences about speciation scenarios (dispersal-vicariance analysis [DIVA; parsimony-based] and dispersal-extinction-cladogenesis [DEC; likelihood-based]). The methods yield conflicting results, which we interpret in light of their respective assumptions. FP exhibits the least power to unequivocally reconstruct ranges, likely due to a combination of having flat (uninformative) transition costs and not using branch length information. SM reconstructions generally agree with a prior hypothesis about dispersal-driven speciation across the Pacific, despite the conceptual mismatch between its character-based model and this mode of range evolution. In contrast with narrow extant ranges for species of Cyrtandra, DIVA reconstructs broad ancestral ranges at many nodes. DIVA results also conflict with geological information on island ages; we attribute these conflicts to the parsimony criterion not considering branch lengths or time, as well as vicariance being the sole means of divergence for widespread ancestors. DEC analyses incorporated geological information on island ages and allowed prior hypotheses about range size and dispersal rates to be evaluated in a likelihood framework and gave more nuanced inferences about range evolution and the geography of speciation than other methods tested. However, ancestral ranges at several nodes could not be conclusively resolved, due possibly to uncertainty in the phylogeny or the relative complexity of the underlying model. Of the methods tested, SM and DEC both converge on plausible hypotheses for area range histories in Cyrtandra, due in part to the consideration of branch lengths and/or timing of events. We suggest that DEC model-based methods for ancestral range inference could be improved by adopting a Bayesian SM approach, in which stochastic sampling of complete geographic histories could be integrated over alternative phylogenetic topologies. Likelihood-based estimates of ancestral ranges for Cyrtandra suggest a major dispersal route into the Pacific through the islands of Fiji and Samoa, motivating future biogeographic investigation of this poorly known region.

Interspecific Hybridization in Natural Populations of Cyrtandra (Gesneriaceae) on the Hawaiian Islands: Evidence from RAPD Markers

Interspecific hybridization among Hawaiian species ofCyrtandra (Gesneriaceae) was investigated using randomly amplified polymorphic DNA (RAPD) markers. Thirty-three different primers were used to investigate interspecific hybridization for 17 different putative hybrids based on morphological intermediacy and sympatry with putative parental species. RAPD data provided evidence for the hybrid origin of all putative hybrid taxa examined in this analysis. However, the patterns in the hybrid taxa were not found to be completely additive of the patterns found in the parental species. Markers missing in the hybrid taxa can be attributed to polymorphism in the populations of the parental species and the dominant nature of inheritance for RAPD markers. Unique markers found within hybrid taxa require further explanation but do not necessarily indicate that the taxa are not of hybrid origin. The implications suggest that these interspecific hybridization events had, and continue to have, an effect on the adaptive radiation and conservation biology ofCyrtandra.

A phylogenetic analysis of Schiedea and Alsinidendron (Caryophyllaceae: Alsinoideae): implications for the evolution of breeding systems

Phylogenetic analysis of Schiedea and Alsinidendron (Caryophyllaceae), a monophyletic lineage endemic to the Hawaiian Islands, produced six equally most parsimonious trees with 132 steps using morphological characters. Four major clades were found in all trees. Breeding system characters were excluded from the analysis because of the likelihood that dimorphism (gynodioecy, subdioecy, dioecy) has evolved in parallel in Schiedea, although subsequent inclusion of these characters had little effect on topology. Dimorphism is found in the two clades occurring primarily in dry habitats. Mapping of breeding systems on the phylogeny suggests that dimorphism has probably evolved on two or more occasions, depending on the number of character states and whether the character is treated as ordered or unordered. One to several reversals from dimorphism to hermaphroditism have also occurred. Dimorphic species occur only in dry habitats, but mapping of habitat on the phylogeny suggests that hermaphroditic species originally may have invaded dry habitats without evolving a dimorphic breeding system. Ecological shifts to very wet habitats appear to have favored the evolution of autogamy, which has occurred independently in the two clades largely restricted to mesic or wet habitats. The striking variation in breeding systems found in Schiedea and Alsinidendron appears to result in large part from the invasion of diverse habitats in the Hawaiian Islands following colonization by the ancestor of this lineage. Dioecy, the presence of separate pistillate (female) and staminate (male) plants in a population, occurs in about 4% of all flowering plants (Yampolsky and Yampolsky 1922). Numerous theoretical and empirical studies have addressed the question of why dioecy should evolve, given that female or male individuals suffer a 50% loss in reproductive potential relative to hermaphrodites. One set of arguments emphasizes the importance of inbreeding depression. In models developed by Lloyd (1975a) and Charlesworth and Charlesworth (1978), females may spread in populations if both inbreeding depression and selfing rates are high. Under these conditions, females spread because the.progeny of females, which are always outcrossed, will have higher fitness than the progeny of hermaphrodites, which self to varying degrees. If females produce more seeds than hermaphrodites, which seems likely on the basis of resource reallocation, they may spread even when inbreeding depression and selfing rates of hermaphrodites are lower. Other models (Charnov 1982) emphasize the importance of shifts in resource allocation. Empirical studies indicate the widespread occurrence of inbreeding depression (Schemske 1983; Schoen 1983; Sakai et al. 1989; Dudash 1990; Johnston 1992), and studies of selfing rates in several species with high inbreeding depression indicate that unisexual individuals should be favored by selection (Kohn 1988; Sakai and Weller, unpubl. data). Overall, little evidence has accumulated suggesting that either

A New Lineage‐Based Tribal Classification of the Family Caryophyllaceae

Understanding the relationships within the Caryophyllaceae has been difficult, in part because of arbitrarily and poorly defined genera and difficulty in determining phylogenetically useful morphological characters. This study represents the most complete phylogenetic analysis of the family to date, with particular focus on the genera and relationships within the large subfamily Alsinoideae, using molecular characters to examine the monophyly of taxa and the validity of the current taxonomy as well as to resolve the obscure origins of divergent taxa such as the endemic Hawaiian Schiedea. Maximum parsimony and maximum likelihood analyses of three chloroplast gene regions (matK, trnL‐F, and rps16) from 81 newly sampled and 65 GenBank specimens reveal that several tribes and genera, especially within the Alsinoideae, are not monophyletic. Large genera such as Arenaria and Minuartia are polyphyletic, as are several smaller genera. The phylogenies reveal that the closest relatives to Schiedea are a pair of widespread, largely Arctic taxa, Honckenya peploides and Wilhelmsia physodes. More importantly, the three traditional subfamilies (Alsinoideae, Caryophylloideae, and Paronychioideae) are not reflective of natural groups; we propose abandoning this classification in favor of a new system that recognizes major lineages of the molecular phylogeny at the tribal level. A new tribe, Eremogoneae Rabeler & W.L. Wagner, is described here.

Outcomes of the 2011 Botanical Nomenclature Section at the XVIII International Botanical Congress

Abstract The Nomenclature Section held just before the 18th International Botanical Congress in Melbourne, Australia in July 2011 saw sweeping changes to the way scientists name new plants, algae, and fungi. The changes begin on the cover: the title was broadened to make explicit that the Code applies not only to plants, but also to algae and fungi. The new title will now be the International Code of Nomenclature of algae, fungi, and plants. For the first time in history the Code will allow for the electronic publication of names of new taxa. In an effort to make the publication of new names more accurate and efficient, the requirement for a Latin validating diagnosis or description was changed to allow either English or Latin for these essential components of the publication of a new name. Both of these latter changes will take effect on 1 January 2012. The nomenclatural rules for fungi will see several important changes, the most important of which is probably the adoption of the principle of “one fungus, one name.” Paleobotanists will also see changes with the elimination of the concept of “morphotaxa” from the Code.