Bruce G. Baldwin

Long-distance dispersal: a framework for hypothesis testing

Tests of hypotheses about the biogeographical consequences of long-distance dispersal have long eluded biologists, largely because of the rarity and presumed unpredictability of such events. Here, we examine data for terrestrial (including littoral) organisms in the Pacific to show that knowledge of dispersal by wind, birds and oceanic drift or rafting, coupled with information about the natural environment and biology of the organisms, can be used to generate broad biogeographic predictions. We then examine the predictions in the context of the origin, frequency of arrival and location of establishment of dispersed organisms, as well as subsequent patterns of endemism and diversification on remote islands. The predicted patterns are being increasingly supported by phylogenetic data for both terrestrial and littoral organisms.

Switch from specialized to generalized pollination

The once prevalent view that the evolution of extreme ecological specialization is accompanied by a loss of potential for adapting to new conditions, and thus is irreversible, has been challenged by several recent examples,,. However, we know of no modern phylogenetic studies showing reversal in pollination relationships from extreme specialization to generalization, although such reversals are theoretically expected,. Here we present molecular phylogenetic evidence for an evolutionary shift in Dalechampia (Euphorbiaceae) vines from a highly specialized relationship (pollination by one or a few animal species,) with resin-collecting bees to generalized pollination by a variety of pollen-feeding insects. This shift was associated with dispersal from Africa to Madagascar, where the specific resin-collecting pollinators are absent. These results show that plants dispersing beyond the range of their specific pollinators may succeed by evolving more generalized pollination systems.

Phylogeny of the Coneflowers and Relatives (Heliantheae: Asteraceae) Based on Nuclear rDNA Internal Transcribed Spacer (ITS) Sequences and Chlorplast DNA Restriction Site Data

Abstract The internal transcribed spacer (ITS) region of 18S–26S nuclear ribosomal DNA (rDNA) was sequenced in 65 taxa representing most coneflowers (i.e., species in Dracopis, Echinacea, Ratibida, and Rudbeckia) and other taxa representing 21 outgroup genera of tribe Heliantheae. Results of parsimony analysis of the rDNA dataset by itself and in combination with the cpDNA dataset uphold the hypothesis from an earlier cpDNA restriction site study that Echinacea is not closely related to the other three genera of coneflowers. The data support placement of Echinacea in subtribe Zinniinae. The remaining three coneflower genera represent a monophyletic lineage corresponding to subtribe Rudbeckiinae sensu H. Robinson. The rDNA data support two sublineages in Rudbeckia congruent with the two traditionally recognized subgenera, subg. Macrocline and subg. Rudbeckia. In subg. Macrocline, two geographic areas of diversification are indicated: southeastern and western United States. The widespread species R. laciniata is placed strongly with the western lineage of subg. Macrocline. The rDNA data support transfer of Dracopis to Rudbeckia subg. Macrocline, a relationship also supported by multiple morphological characters. The rDNA data do not confidently resolve the sister group of Rudbeckiinae from among the members of Heliantheae investigated. Multiple hypotheses are suggested for the outgroup taxa, such as expanding subtribe Zinniinae to include Echinacea and Trichocoryne, a genus previously regarded as belonging to subtribe Hymenopappinae (Heleneae or Heliantheae sensu lat.). Our findings further support expansion of subtribe Engelmanniinae to include Balsamorhiza, Borrichia, and Wyethia even though these taxa lack ray floret complexes and have fertile disc ovaries. We suggest that bioprospectors might usefully search among taxa of Zinniinae for bioactive substances similar to the immune stimulants of Echinacea. Communicating Editor: Alan Whittemore

Higher-Level Relationships and Major Lineages of Lessingia (Compositae, Astereae) Based on Nuclear rDNA Internal and External Transcribed Spacer (ITS and ETS) Sequences

Abstract The apparent recency of diversification of Californian Lessingia (Compositae, Astereae) makes the genus a particularly interesting group for evolutionary investigation. Here we focus on the major evolutionary lineages within Lessingia (sensu Lane 1992) and the higher-level relationships of the genus and presumed close relatives using sequence data from the 18S–26S nuclear ribosomal DNA (nrDNA) internal transcribed spacer (ITS) region and the 3’ end (561–563 bp) of the external transcribed spacer (ETS). We present new 3‘ETS primers that are useful across Astereae and examine the phylogenetic utility of the 3‘ETS in Lessingia and close relatives. In Lessingia, the 3‘ETS region appears to have evolved up to 1.4 times more rapidly by nucleotide substitution than has the ITS region. Our results show that data from the ETS greatly augments data from the ITS region; the combined data set yields the best resolved and best supported molecular trees for Lessingia. These topologies lead us to five conclusions regarding the phylogenetic relationships of Lessingia (sensu Lane 1992) and closely related genera: (1) Lessingia may not be monophyletic when Benitoa is included within the genus, (2) among the taxa sampled, Benitoa and Hazardia appear to be the closest living relatives of Lessingia s. s. and L. filaginifolia (= Corethrogyne), (3) a sister group relationship exists between the radiate, perennial L. filaginifolia (= Corethrogyne) and the discoid, annual members of the genus (Lessingia s. s.), (4) different corolla coloration (pink/white vs. yellow) diagnoses the two major clades of Lessingia s. s., and (5) the “yellow group” of lessingias comprises three distinct, morphologically diagnosable, lineages which span the currently accepted circumscriptions of two taxa (L. lemmonii and L. glandulifera). Communicating Editor: Kathleen A. Kron

Nuclear rDNA Evidence for Major Lineages of Helenioid Heliantheae (Compositae)

Abstract Results of phylogenetic analyses of nuclear 18S–26S rDNA internal transcribed spacer (ITS) region sequences for representatives of most genera of helenioid Heliantheae and various members of Heliantheae s.s. (sensu stricto) and Eupatorieae help to clarify major lineages and relationships in the clade corresponding to Heliantheae s.l. (sensu lato) and Eupatorieae. Most subtribes of helenioid Heliantheae as circumscribed by Robinson (1981) correspond closely with ITS clades. Polygeneric subtribes of helenioid Heliantheae that appear to be monophyletic based on ITS data include Flaveriinae sensu Turner and Powell (1977), Madiinae sensu Carlquist (1959), and Peritylinae sensu Robinson (1981). Chaenactidinae sensu Robinson (1981) is polyphyletic, but most members of the group are encompassed within only four ITS clades. Based on the ITS data and results of combined analyses of ITS variation plus previously published morphological and chloroplast DNA data, we conclude that Heliantheae s.s. and Eupatorieae represent nested clades within helenioid Heliantheae, as previously suggested. Loss of paleae appears to have been a rare occurrence during radiation of Heliantheae s.s.; only one epaleate taxon that we sampled (Trichocoryne) was placed within an ITS clade of otherwise paleate taxa, referable to Heliantheae s.s. We conclude that expression of paleae in Heliantheae s.s., Madiinae, and Marshallia is homoplasious. We also conclude that pappi of bristles or bristle-like subulate scales have arisen in various lineages of Heliantheae s.l. and in general have received too much weight in previous circumscriptions of suprageneric taxa. Multiple examples of extreme dysploidy from high (putatively polyploid) ancestral chromosome numbers in helenioid Heliantheae are evident from the phylogenetic data. Bidirectional ecological shifts between annual and perennial habits and repeated origins of woodiness from herbaceous ancestors also can be concluded for helenioid Heliantheae. Based on modern distributions of taxa and evident phylogenetic patterns, Baeriinae, Madiinae, and the x = 19 “arnicoid” taxa probably share a common Californian ancestry. To produce a tribal taxonomy for Heliantheae s.l. that better reflects phylogenetic relationships, Eupatorieae and (provisionally) Heliantheae s.s. are retained in essentially the traditional senses, Helenieae is recognized in a restricted sense, Madieae and Tageteae are expanded, and three new tribes (Bahieae, Chaenactideae, and Perityleae) are erected. In Madieae, three new subtribes (Arnicinae, Hulseinae, and Venegasiinae) are recognized, in addition to Baeriinae and Madiinae. In Peritylinae, a new combination, Perityle montana, is proposed for Correllia montana. Communicating Editor: Richard Jensen

Phylogenetic utility of the nuclear rDNA ITS region in subfamily Ixoroideae (Rubiaceae): comparisons with cpDNA rbcL sequence data

ITS of the nrDNA were sequenced for 21 taxa inIxoroideae and outgroups (Rubiaceae) and compared with sequences of the cp-generbcL. Separate and combined analyses were performed. ITS-variation was extensive and, because of alignment ambiguities, some sites were excluded from the analyses. Several topologies from therbcL analysis that conflicted with earlier classifications are corroborated by the ITS data: 1)Posoqueria should be excluded fromGardenieae. 2) The disputed genusBertiera, previously inGardenieae, is basal in an extendedCoffeeae, includingTricalysia. 3)Ixora should be excluded fromPavetteae. 4)Vangueria, (Antirheoideae), belongs toIxoroideae. This affiliation ofAntirheoideae tribes withIxoroideae is also shown by new ITS andrbcL data forAlberta. Incongruities found between the two data sets may be caused by density of taxon sampling, different evolutionary rates, phylogenetic sorting, homoplasy caused by functional constraints, or sampling of non-orthologous ITS types.

Macroevolutionary patterns of defense and pollination in Dalechampia vines: adaptation, exaptation, and evolutionary novelty.

We conducted phylogenetically informed comparative analyses of 81 taxa of Dalechampia (Euphorbiaceae) vines and shrubs to assess the roles of historical contingency and trait interaction in the evolution of plant-defense and pollinator-attraction systems. We asked whether defenses can originate by exaptation from preexisting pollinator attractants, or vice versa, whether plant defenses show escalation, and if so, whether by enhancing one line of defense or by adding new lines of defense. Two major patterns emerged: (i) correlated evolution of several complementary lines of defense of flowers, seeds, and leaves, and (ii) 5 to 6 losses of the resin reward, followed by redeployment of resin for defense of male flowers in 3 to 4 lineages, apparently in response to herbivore-mediated selection for defense of staminate flowers upon relaxation of pollinator-mediated selection on resin. In all cases, redeployment of resin involved reversion to the inferred ancestral arrangement of flowers and resiniferous bractlets. Triterpene resin has also been deployed for defense of leaves and developing seeds. Other unique defenses against florivores include nocturnal closure of large involucral bracts around receptive flowers and permanent closure around developing fruits (until opening again upon dehiscence). Escalation in one major clade occurred through an early dramatic increase in the number of lines of defense and in the other major clade by more limited increases throughout the groups evolution. We conclude that preaptations played important roles in the evolution of unique defense and attraction systems, and that the evolution of interactions with herbivores can be influenced by adaptations for pollination, and vice versa.

Phylogeny and ecological radiation of New World thistles (Cirsium, Cardueae – Compositae) based on ITS and ETS rDNA sequence data

Sequence data from a portion of the external transcribed spacer (ETS) and internal transcribed spacers (ITS‐1 and ITS‐2) of 18S‐26S nuclear ribosomal DNA were used to resolve historical biogeography and ecology of true thistles (Cirsium, Cardueae, Compositae) in the New World. The 650 base‐pair, 3′ portion of the ETS examined here showed a level of variation across taxa similar to that of the ITS sequences included. A maximum‐likelihood tree based on combined ETS and ITS sequences leads us to suggest that the New World species of true thistles constitute a major lineage, which in turn comprises several smaller lineages. A western North American lineage shows weak quartet‐puzzling support, but includes a well‐supported lineage of species endemic to the California Floristic Province. Comparisons of this Californian lineage with other neoendemic angiosperm groups of the region show that the Californian Cirsium lineage exhibits unusually high ecological diversity for a group displaying such low levels of rDNA sequence divergence across taxa. Similarly low levels of sequence divergence were found throughout the New World Cirsium lineage. These results indicate either that Cirsium underwent a rapid ecological radiation in North America, or that rDNA evolution in North American Cirsium has been highly conservative.

Edaphic races and phylogenetic taxa in the Lasthenia californica complex (Asteraceae: Heliantheae): an hypothesis of parallel evolution

Lasthenia californica sensu Ornduff consists of two races that differ in their flavonoid pigments and edaphic tolerances. Recent phylogenetic studies of Lasthenia have revealed that members of L. californica sensu Ornduff belong to two phylogenetic species. The relationship of the edaphic races to these new species and to each other is the focus of this study. Characterization of flavonoid profiles and phylogenetic placement of 33 populations demonstrates that races and phylogenetic taxa are not concordant, suggesting that one or both edaphic races evolved in parallel in the two clades. We hypothesize an edaphically linked ecological role for flavonoid differences that first revealed the existence of two races.

ORIGIN OF THE SERPENTINE-ENDEMIC HERB LAYIA DISCOIDEA FROM THE WIDESPREAD L. GLANDULOSA (COMPOSITAE)

Abstract Phylogenetic analyses of nuclear rDNA sequences uphold Gottlieb et al.s hypothesis that Layia discoidea, a morphologically unusual, serpentine‐endemic herb of narrow distribution in central California, “budded off” recently (less than one million years ago) from a nearby lineage of the widespread L. glandulosa, which occurs on sandy soils across much of far western North America. Although L. discoidea and L. glandulosa retain complete interfertility, nuclear rDNA data for the two species are almost free of evolutionary noise, without evidence of gene flow between them; allopatric divergence of L. discoidea cannot be ruled out. Molecular data are consistent with a hypothesis of accelerated morphological evolution of L. discoidea and Gottlieb et al.s suggestion that the closest relatives of L. discoidea are populations of L. glandulosa with yellow, rather than white, ray corollas, in accord with Clausen, Keck, and Hieseys evidence of a gene for yellow ray coloration in the rayless L. discoidea.