Three Variable Arenopontia Species (Crustacea, Copepoda) from Panamá

Three species of the genus Arenopontia (Cylindropsyllidae) from the Pacific and Atlantic coast of Panamá are presented. Two of them are A. trisetosa Mielke and A. peteruxi Mielke, both of which were described for the first time from the Galápagos Islands. The third species is tentatively identified as A. gussoae Cottarelli previously reported from an interstitial habitat in Cuba.     

Hybridization between the Galápagos land and marine iguana (Canolophus subcristatus and Amblyrhynchus cristatus) on Plaza Sur

Hybridization plays an important role in the evolution of some of the vertebrate taxa on the Galápagos Islands, such as the Darwin finches. Conversely, only a single possible hybrid between the Galápagos marine iguana ( Amblyrhynchus ) and the land iguana ( Conolophus ) has been reported from the island Plaza Sur. In this paper, the hybrid status of a morphologically unusual iguana from this island is confirmed, using restriction fragment length polymorphism (RFLP) analyses of the nuclear ribosomal DNA (rDNA). Sequencing of the hybrid's mitochondrial cytochrome b gene revealed that it was the offspring of a female land iguana and a male marine iguana. Preliminary molecular analyses of morphologically typical marine and land iguanas from Plaza Sur did not detect introgression of nuclear or mitochondrial markers between species. The potential significance of hybridization for the evolution of the Plaza Sur iguana populations is discussed.     

Chromosome number of Macraea Iaricifolia Hooker fil. (Compositae) and its bearhg on the taxonomic affinity of the genus

ELIASSON, U. H., 1984. Chromosome number of Macraea lariciflia Hooker fil. (Compositae) and its bearing on the taxonomic affinity of the genus. The chromosome number of Macraea laricifolia , a composite endemic to the Galápagos Islands, is reported to be 2 n = 28. Macraea was once regarded as congeneric with Lipochacta , a genus restricted to Hawaii. The chromosome number supports morphological evidence that the two genera arose independently from wedelioid ancestors within the Heliantheae.     

A new look at evolution in the Galápagos: evidence from the late Cenozoic marine molluscan fauna

Endemism is not as common in the marine invertebrate fauna of the Galápagos Islands region as in the adjacent terrestrial biota. Marine invertebrates in the Galápagos are largely cosmopolitan species from the Panamic, Indo-Pacific, Californian, or Peruvian faunal provinces. However, an endemic component is also present in the fauna. The observed pattern among marine invertebrate organisms can be accounted for by at least two processes: (1) genetic continuity between mainland and island populations mediated through planktonic larvae; and (2) lower rates of intrinsic evolutionary change. The evolutionary scenario standardly applied to terrestrial organisms in the Galápagos, namely, adaptive radiation and speciation in reproductive isolation from mainland source populations, does not apply to all marine invertebrates. Evidence in support of the alternative scenario for marine invertebrates comes from both published records of species occurring in the islands and recent studies of fossil-bearing deposits on several islands in the archipelago. Two misconceptions–considering the islands and sedimentary deposits to be older than now thought, and equating the rate of evolution of the terrestrial biota with the marine biota–can lead to an incorrect interpretation of evolution in the Galápagos Contrasts between marine invertebrate and terrestrial organisms serve to illustrate some fundamental differences which have important evolutionary implications. Some of these are: endemism; dispersal; taxonomic relationships; island definitions; rates of evolutionary change; and age of fossils. In terms of Darwin's evolutionary scenario, terrestrial organisms represent the paradigm and marine organisms represent the paradox.     

Darwin and the Galápagos

Charles Darwin's historic visit to the Galápagos Islands in 1835 represents a landmark in the annals of science. But contrary to the legend long surrounding Darwin's famous Galápagos visit, he continued to believe that species were immutable for nearly a year and a half after leaving these islands. This delay in Darwin's evolutionary appreciation of the Galápagos evidence is largely owing to numerous misconceptions that he entertained about the islands, and their unique organic inhabitants, during the Beagle voyage. For example, Darwin mistakenly thought that the Galápagos tortoise–adult specimens of which he did not collect for scientific purposes–was not native to these islands. Hence he apparently interpreted reports of island-to-island differences among the tortoises as analogous to changes that are commonly undergone by species removed from their natural habitats. As for Darwin's finches, Darwin initially failed to recognize the closely related nature of the group, mistaking certain species for the forms that they appear, through adaptive radiation, to mimic. Moreover, what locality information he later published for his Galápagos finch specimens was derived almost entirely from the collections of three other Beagle shipmates, following his return to England. Even after he became an evolutionist, in March of 1837 (when he discussed his Galápagos birds with the eminent ornithologist John Gould), Darwin's theoretical understanding of evolution in the Galápagos continued to undergo significant developments for almost as many years as it took him to publish the Origin of Species (1859). The Darwin-Galápagos legend, with its romantic portrait of Darwin's 'eureka-like' insight into the Galápagos as a microcosmic 'laboratory of evolution', masks the complex nature of scientific discovery, and, thereby, the real nature of Darwin's genius.     

Reproductive ecology of the endemic Lecocarpus pinnatifidus (Asteraceae) in an isolated population in the Galápagos Islands

Lecocarpus pinnatifidus is an endemic member of the Asteraceae occurring on only one island in the Galápagos archipelago. The capitula are large with female ray florets and male disc florets. They are self-compatible but this study suggests fruit set is pollen limited. Visits from Xylocopa darwini and other larger insect pollinators are rare, and small insects seem to be the main pollinators. Small insects carry few pollen grains and most likely mediate self-pollinations. Self-compatibility and seed set after selfing are the most common reproductive strategy in the Galápagos Islands and L. pinnatifidus seemingly fits well into this group.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 171–180.     

The bark and ambrosia beetles (Curculionidae, Scolytinae) of Cocos Island, Costa Rica and the role of mating systems in island zoogeography

Cocos Island is a small oceanic island midway between Costa Rica and the Galápagos Archipelago; about 2 Myr in age, it is the only tropical oceanic island in the eastern Pacific with tropical wet forest. We identified several hundred bark beetle specimens collected during recent expeditions by INBio, the National Biodiversity Institute of Costa Rica, and re-examined all specimens from earlier collections. We report 19 species in ten genera, seven or eight of which are endemic, making scolytines the largest group of beetles known from the island. We describe as new Pycnarthrum pseudoinsulare , Xyleborinus cocoensis , and Xyleborus sparsegranulosus , resurrect Xyleborus bispinatus as separate from X. ferrugineus , and report six other species as new to Cocos Island. Three-quarters of the scolytines reproduce by brother–sister mating, and we argue that inbreeders are superior island colonists because they are less affected than are outbreeders by problems of mate location and inbreeding depression. The fauna and flora of Cocos Island arrived by dispersal and human transport. We examine natural colonization patterns for the fauna, using the distributions of the relatives of island endemics: most colonization came from the Americas, but the closest relatives to some endemics are found on Caribbean or Galápagos islands. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 729–743.     

A summary of geographical characteristics of the Galapagos Islands

Republished here, with permission, in a slightly modified form, from Noticias de Galapagos 55, July 1995, 18–24. Copyright remains, by agreement, with Noticias de Galápagos , which is published by The Charles Darwin Foundation for the Galápagos Islands.     

The vascular plants of Joseph Dalton Hooker's An enumeration of the plants of the Galapagos Archipelago; with descriptions of those which are new

The first floristic work on the Galápagos Islands was published by J. D. Hooker in 1847. It was based mainly on the Beagle collections of Charles Darwin, but those of James McRae, John Scouler. Hugh Cuming, David Douglas, Thomas Edmonston, Abel Du Petit-Thouars and John Goodridge were also used, though those of Archibald Menzies, the first botanist to visit the archipelago, were not. The visits of these naturalists and their collections are discussed. Darwin's field notes on Galápagos plants, hitherto unpublished, are given, and most of the species identified. In the taxonomic portion of the paper, each taxon included by Hooker is discussed, the nomenclaturally or-taxonomically correct name is indicated, specimens examined by Hooker are enumerated, and additional specimens presumably seen but not cited by him are given. Hooker wrote before our present type concept had evolved, and consequently 51 of his 114 new names needed to be typified, as did four others based on Darwin Galápagos collections. In addition, examination of these specimens revealed one species not yet reported from the archipelago ( Galium canescens ), one new island record ( Chamaesyce hirta on James Island), and one deletion from the flora ( Malachra capitala )     

The microevolution of the Galápagos marine iguana Amblyrhynchus cristatus assessed by nuclear and mitochondrial genetic analyses

Marine iguanas may have inhabited the Galápagos archipelago and its former, now sunken islands for more than 10 million years (Myr). It is therefore surprising that morphological and immunological data indicate little evolutionary divergence within the genus. We utilized mitochondrial DNA (mtDNA) sequence analyses and nuclear DNA fingerprinting to re-evaluate the level and pattern of genetic differentiation among 22 marine iguana populations from throughout the archipelago. Both genetic marker systems detect a low level of within-genus divergence, but they show contrasting levels of geographical subdivision among the populations. The mitochondrial gene pools of populations from different regions of the archipelago are isolated, and the mtDNA pattern appears to follow the sequence in which the islands were colonized by marine iguanas. Conversely, the nuclear DNA study indicates substantial interpopulational gene exchange, and the geographical distribution of the nuclear markers seems to be determined by isolation by distance among the populations. The natural history of marine iguanas suggests that the contrasting nuclear and mitochondrial DNA patterns result from an asymmetric migration behaviour of the two sexes, with higher (active and passive) interisland dispersal for males than females. Separate genetic analyses for the sexes appear to support this hypophesis. Based on these findings, a scenario is proposed that explains the marine iguanas' low genetic divergence, notwithstanding their long evolutionary history in the Galápagos archipelago.     

Number of endemic and native plant species in the Galápagos Archipelago in relation to geographical parameters

By simple and multiple regression analyses we investigate updated species numbers of endemic and native vascular plants and seed plants in the Galápagos Archipelago in relation to geographical parameters. We find that the best models to describe species numbers are regression models with log-transformed species numbers as dependent and log-transformed modified area (i.e. area not covered with barren lava) as an independent variable. This holds both for total species number, for native species number, for endemic species number and for total number of seed plants as well as number of endemic seed plants. For the ratio between endemic and native species, modified area is also the major significant variable, but with a negative regression slope.
Multiple regression models show that some isolation measures are significant contributors and may explain some of the residual variation, but their contribution to total explained variation is in general small.
The results show that the species area relationships are different for native and endemic species. This is discussed in relation to classical island biogeographical models, and the concepts of radiative speciation.     

Dynamics of a stand of Scalesia pedunculata Hooker fil., Santa Cruz Island, Galapagos

A seven-year study of a stand of the endemic Scalesia pedunculata (Asteraceae), which is the dominant tier ill the humid forest on the island oS Santa Cruz, Galápagos, reveals a characteristic pattern of growth and survival. The Scalesia trees initially show a rapid increase in both height and girth. After approximately 34–56 years the trees may reach 7–8 m in height and start producing flowers; the relative increase in girth then becomes more pronounced. The mortality rate is very high during the first 4–5 years, decreasing thereafter as the individuals age. It is suggested that the growth and survival pattern of S. pedunculata is an expression of an adaptive strategy fitted for a pioneer or early-successional tree. This tree is simultaneously able to persist in the community by the means of a large reproductive effort and a rapid population turnover. The method of seed-dispersal in the genus discussed in relation to the growth pattern.     

Phylogeny of Nolana (Solanaceae) of the Atacama and Peruvian deserts inferred from sequences of four plastid markers and the nuclear LEAFY second intron

The phylogeny of Nolana (Solanaceae), a genus primarily distributed in the coastal Atacama and Peruvian deserts with a few species in the Andes and one species endemic to the Galápagos Islands, was reconstructed using sequences of four plastid regions (ndhF, psbA-trnH, rps16-trnK and trnC-psbM) and the nuclear LEAFY second intron. The monophyly of Nolana was strongly supported by all molecular data. The LEAFY data suggested that the Chilean species, including Nolana sessiliflora, the N. acuminata group and at least some members of the Alona group, are basally diverged, supporting the Chilean origin of the genus. Three well-supported clades in the LEAFY tree were corroborated by the SINE (short interspersed elements) or SINE-like insertions. Taxa from Peru are grouped roughly into two clades. Nolana galapagensis from the Galápagos Island is most likely to have derived from a Peruvian ancestor. The monophyly of the morphologically well-diagnosed Nolana acuminata group (N. acuminata, N. baccata, N. paradoxa, N. parviflora, N. pterocarpa, N. rupicola and N. elegans) was supported by both plastid and LEAFY data. Incongruence between the plastid and the LEAFY data was detected concerning primarily the positions of N. sessiliflora, N. galapagensis, taxa of the Alona group and the two Peruvian clades. Such incongruence may be due to reticulate evolution or in some cases lineage sorting of plastid DNA. Incongruence between our previous GBSSI trees and the plastid-LEAFY trees was also detected concerning two well-supported major clades in the GBSSI tree. Duplication of the GBSSI gene may have contributed to this incongruence.     

Geology of Galápagos

This paper reviews the origins and geological history of the Galápagos Islands. The islands arose from a 'hot-spot'. The oceanic crust on which the islands are built can be no more than 10 million years old, and the islands themselves have been in existence at least 3.3 million years.
The Galápagos are among the most active volcanic groups in the world, and the physical nature of the islands is dominated by lava structures of various ages, including lava tubes or tunnels, which have been of particular interest to biologists. Weathering of the rock to produce soil has generally been slow, particularly in the drier parts.     

The neglected side of speciation in ancient lakes: phylogeography of an inconspicuous mollusc taxon in lakes Ohrid and Prespa

The morphologically remarkable endemic fauna within ancient lakes has received much attention in the literature. More inconspicuous taxa, however, often lack detailed molecular and morphometrical examination, although their proportion of the endemic fauna of an ancient lake must not be underestimated. Consequently, a better understanding of evolutionary patterns and processes within these lakes requires more knowledge about the often-neglected inconspicuous taxa. In the present study, we focus on the notoriously cryptic pea clam genus Pisidium (Bivalvia: Sphaeriidae). Though the genus is widely distributed, most endemic species are reported only from ancient lakes, including the European ancient sister lake system of Ohrid and Prespa on the Balkan Peninsula. Here we test for the first time hypotheses on the evolution of the endemic pea clams in this European biodiversity hotspot by molecular means. Combining a broad 16S phylogeny (comprising most European pea clam species), network analyses and morphometrical analyses, we found interesting biogeographical patterns and provide evidence for cryptic species in both lakes. Furthermore, we confirmed the proposed sister-species relationship of the endemics P. edlaueri in Lake Ohrid and P. maasseni in Lake Prespa, and we suggest scenarios of the endemic pea clam evolution within both lakes. The patterns of speciation found in the genus Pisidium are compared to patterns in morphologically distinct molluscan groups in lakes Ohrid und Prespa.     

PORPHYRA SUBORBICULATA, PORPHYRA CAROLINENSIS AND PORPHYRA LILLIPUTIANA - THREE NAMES FOR ONE SMALL PORPHYRA

The genus Porphyra is ancient, successful, and morphologically simple. Its members provide a particular challenge to systematists who must decide whether shared features are a result of homoplasy, or reflect recent common ancestry. Three species of diminutive Porphyra with widespread geographic origins share many common morphological features: P suborbiculata Kjellm. has been reported from the west Pacific and Indian Oceans, P. carolinensis Coll et J. Cox from the west Atlantic, and P lilliputiana W. A. Nelson, G. A.Knight et M. W. Hawkes from New Zealand. Comparison of 18S rDNA sequence data from small Porphyra thalli from Mexico, Japan, New Zealand, Australia and Connecticut indicate that these three taxa in fact belong to one cosmopolitan species, which is distributed over three oceans and two hemispheres. Analysis of sequence data from introns present in the 18S rDNA and from the ITS region suggest that this distribution may be linked to human activity, and raises the question of to which geographic locality this entity is truly endemic?     

Darwin was astonished

Darwin did not approach the Galápagos with the same enthusiasm and energy as he showed at earlier places visited by the Beagle. Notwithstanding, he looked back on the five weeks the Beagle spent in the Galápagos as a time when he made observations important for the development of his evolutionary ideas. In retrospect, he was astonished at what he saw there.     

Phylogenetics of Darwiniothamnus (Asteraceae: Astereae) – molecular evidence for multiple origins in the endemic flora of the Galápagos Islands

Aim The aims of this study were (1) to investigate whether the two growth forms of Darwiniothamnus Harling (Asteraceae) originated from the colonization of a single ancestor, (2) to identify the closest relative(s) of Darwiniothamnus, and (3) to review molecular phylogenies from other plant groups to infer the origin of Galápagos endemics. Location Darwiniothamnus is endemic to the Galápagos Islands. Methods All putative relatives of Darwiniothamnus plus 38 additional species were included. Nucleotide sequences of the internal transcribed spacers of the nuclear ribosomal DNA were used for Bayesian and parsimony analyses. Results Darwiniothamnus is polyphyletic. Two species (D. lancifolius (Hook. f.) Harling and D. tenuifolius (Hook. f.) Harling) are woody shrubs that usually grow to 1–2 m in height; they belong to a clade composed of species otherwise restricted to the Caribbean. These two species are sister to Erigeron bellidiastroides Griseb., a herbaceous species endemic to Cuba. The third species (D. alternifolius Lawesson & Adsersen) is a perennial herbaceous plant, woody at the base and reaching only up to 50 cm in height. It is sister to two Chilean (Coquimbo–Valparaiso region) species that also have a perennial herbaceous habit: E. fasciculatus Colla and E. luxurians (Skottsb.) Solbrig. They are placed in an assemblage restricted to South America. The review of previous molecular phylogenetic studies revealed that two of the endemic genera and endemic species of three non‐endemic genera have their closest relatives in South America. Endemic species belonging to three non‐endemic genera have sister species in North America or the West Indies. One endemic genus and endemic species in three non‐endemic genera have sister taxa with a widespread continental distribution, or their molecular phylogenies yielded equivocal results. Main conclusions The flora of Galápagos has affinities with both North America (including the Antilles) and South America. Darwiniothamnus exhibits both patterns: two species of this genus are sister to a taxon endemic to Cuba, supporting a connection between the Cocos plate and the West Indies; the third species, D. alternifolius, provides a link with the Coquimbo–Valparaiso region, suggesting a biogeographical connection between the Nazca plate and southern South America.