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The Evolution of Parasites from Their Hosts: A Case Study in the Parasitic Red Algae
Abstract
Morphological similarities of many parasites and their hosts have led to speculation that some groups of plant, animal, fungal, and algal parasites may have evolved directly from their hosts. These parasites, which have been termed adelphoparasites in the botanical literature, and more recently, agastoparasites in the insect literature, may evolve monophyletically from one host and radiate secondarily to other hosts or, these parasites may arise polyphyletically, each arising from its own host. In this study we compare the internal transcribed spacer regions of the nuclear ribosomal repeats of species and formae specialis (host races) included in the red algal parasite genus Asterocolax with its hosts, which all belong to the Phycodrys group of the Delesseriaceae and with closely related nonhost taxa of the Delesseriaceae. These analyses reveal that species of Asterocolax have evolved polyphyletically. Asterocolax erythroglossi from the North Atlantic host Erythroglossum laciniatum appears to have evolved from its host, whereas taxa included in the north Pacific species Asterocolax gardneri have had two independent origins. Asterocolax gardneri from the host Polyneura latissima probably arose directly from this host. In contrast, all other A. gardneri formae specialis appear to have originated from either Phycodrys setchellii or P. isabelliae and radiated secondarily onto other closely related taxa of the Phycodrys group, including Nienburgia andersoniana and Anisocladella pacifica. Gamete crossing experiments confirm that A. gardneri from each host is genetically isolated from both its host, and from other A. gardneri and their hosts. Cross-infection experiments reveal that A. gardneri develops normally only on its natural host, although some abberrant growth may occur on alternate hosts. The ability of red algal parasites to radiate secondarily to other red algal taxa, where they may become isolated genetically and speciate, suggests that this process of speciation is not a 'genetic dead end' but one that may give rise to related clusters of parasite species.
... However, determination of taxonomic positions of red algal parasites based solely on morphological inference was hindered by the complicated evolutionary history of the parasites, which may result in the morphological dissimilarity between the parasites and their hosts, a broad host range, and possible hostswitching events. Molecular phylogenetic techniques have been successfully used to resolve the evolutionary relationships between red algal parasites and their host species [7][8][9][10][11]. Molecular analyses revealed that most of the red algal parasites are sister species to their hosts derived from a recent common ancestor [7,11]; and some radiated to exploit more distantly related hosts [8][9][10]. ...
... Molecular phylogenetic techniques have been successfully used to resolve the evolutionary relationships between red algal parasites and their host species [7][8][9][10][11]. Molecular analyses revealed that most of the red algal parasites are sister species to their hosts derived from a recent common ancestor [7,11]; and some radiated to exploit more distantly related hosts [8][9][10]. ...
... C. babae corresponded to the concept of promiscuous alloparasites [3] which describes red algal parasites that grow on several hosts in nature, with at least one of the hosts not closely related to the parasites. The present study also concurred with previous molecular studies [7][8][9][10], in which red algal parasites infect only hosts within the same family, even in cases of parasite species that have radiated or switched to a secondary host species. ...
[This corrects the article DOI: 10.1371/journal.pone.0097450.].
... Therefore, understanding the evolutionary trajectory between photosynthesis and abandoning autotrophy for a parasitic strategy, is of particular importance. Red algal parasites are uniquely valuable to study this path because they have independently evolved many times, providing literally dozens of discrete events to compare [4][5][6][7]. This system may provide novel insights into the evolution of parasitism, especially with regard to the early stages of transitioning from a photosynthetic past. ...
... Red algal parasites exclusively infect other red algae, typically ones with which they share a recent common ancestor [5][6][7][8]. The relationship between host and parasite was first recognized using morphological similarities in the life-cycles of parasites and their hosts [9]. ...
... The relationship between host and parasite was first recognized using morphological similarities in the life-cycles of parasites and their hosts [9]. More recently, molecular data have confirmed this hypothesis [4][5][6]10]. Traditionally red algal parasites have been placed into two different groups, based on their phylogenetic relationships with their hosts [6]. Adelphoparasites (adelpho is Greek for "kin") are closely related to their host and often infect only one host, whereas alloparasites are more divergent from their host(s) [4,6]. ...
Parasitism is a common life strategy throughout the eukaryotic tree of life. Many devastating human pathogens, including the causative agents of malaria and toxoplasmosis, have evolved from a photosynthetic ancestor. However, how an organism transitions from a photosynthetic to a parasitic life history strategy remains mostly unknown. This is largely because few systems present the opportunity to make meaningful comparisons between a parasite and a close free-living relative. Parasites have independently evolved dozens of times throughout the Florideophyceae (Rhodophyta), and often infect close relatives. The accepted evolutionary paradigm proposes that red algal parasites arise by first infecting a close relative and over time diversify and infect more distantly related species. This provides a natural evolutionary gradient of relationships between hosts and parasites that share a photosynthetic common ancestor. Elegant microscopic work in the late 20th century provided detailed insight into the infection cycle of red algal parasites and the cellular interactions between parasites and their hosts. Those studies led to the use of molecular work to further investigate the origins of the parasite organelles and reveal the evolutionary relationships between hosts and their parasites. Here we synthesize the research detailing the infection methods and cellular interactions between red algal parasites and their hosts. We offer an alternative hypothesis to the current dogma of red algal parasite evolution and propose that red algae can adopt a parasitic life strategy through multiple evolutionary pathways, including direct infection of distant relatives. Furthermore, we highlight potential directions for future research to further evaluate parasite evolution in red algae.
... However, determination of taxonomic positions of red algal parasites based solely on morphological inference was hindered by the complicated evolutionary history of the parasites, which may result in the morphological dissimilarity between the parasites and their hosts, a broad host range, and possible hostswitching events. Molecular phylogenetic techniques have been successfully used to resolve the evolutionary relationships between red algal parasites and their host species [7][8][9][10][11]. Molecular analyses revealed that most of the red algal parasites are sister species to their hosts derived from a recent common ancestor [7,11]; and some radiated to exploit more distantly related hosts [8][9][10]. ...
... Molecular phylogenetic techniques have been successfully used to resolve the evolutionary relationships between red algal parasites and their host species [7][8][9][10][11]. Molecular analyses revealed that most of the red algal parasites are sister species to their hosts derived from a recent common ancestor [7,11]; and some radiated to exploit more distantly related hosts [8][9][10]. ...
... C. babae corresponded to the concept of promiscuous alloparasites [3] which describes red algal parasites that grow on several hosts in nature, with at least one of the hosts not closely related to the parasites. The present study also concurred with previous molecular studies [7][8][9][10], in which red algal parasites infect only hosts within the same family, even in cases of parasite species that have radiated or switched to a secondary host species. ...
Congracilaria babae was first reported as a red alga parasitic on the thallus of Gracilaria salicornia based on Japanese materials. It was circumscribed to have deep spermatangial cavities, coloration similar to its host and the absence of rhizoids. We observed a parasitic red alga with morphological and anatomical features suggestive of C. babae on a Hydropuntia species collected from Sabah, East Malaysia. We addressed the taxonomic affinities of the parasite growing on Hydropuntia sp. based on the DNA sequence of molecular markers from the nuclear, mitochondrial and plastid genomes (nuclear ITS region, mitochondrial cox1 gene and plastid rbcL gene). Phylogenetic analyses based on all genetic markers also implied the monophyly of the parasite from Hydropuntia sp. and C. babae, suggesting their conspecificity. The parasite from Hydropuntia sp. has a DNA signature characteristic to C. babae in having plastid rbcL gene sequence identical to G. salicornia. C. babae is likely to have evolved directly from G. salicornia and subsequently radiated onto a secondary host Hydropuntia sp. We also recommend the transfer of C. babae to the genus Gracilaria and propose a new combination, G. babae, based on the anatomical observations and molecular data. Citation: Ng P-K, Lim P-E, Phang S-M (2014) Radiation of the Red Algal Parasite Congracilaria babae onto a Secondary Host Species, Hydropuntia sp. (Gracilariaceae, Rhodophyta). PLoS ONE 9(5): e97450. doi:10.1371/journal.pone.0097450 Copyright: ß 2014 Ng et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This project is funded by the Postgraduate Research Fund from University of Malaya (PV082/2011B), the Fundamental Research Grant Scheme (FP033-2012A) and MoHE-HIR grant (H-50001-00-A000025) from the Ministry of Higher Education (MOHE), Malaysia. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist.
... However, determination of taxonomic positions of red algal parasites based solely on morphological inference was hindered by the complicated evolutionary history of the parasites, which may result in the morphological dissimilarity between the parasites and their hosts, a broad host range, and possible hostswitching events. Molecular phylogenetic techniques have been successfully used to resolve the evolutionary relationships between red algal parasites and their host species [7][8][9][10][11]. Molecular analyses revealed that most of the red algal parasites are sister species to their hosts derived from a recent common ancestor [7,11]; and some radiated to exploit more distantly related hosts [8][9][10]. ...
... Molecular phylogenetic techniques have been successfully used to resolve the evolutionary relationships between red algal parasites and their host species [7][8][9][10][11]. Molecular analyses revealed that most of the red algal parasites are sister species to their hosts derived from a recent common ancestor [7,11]; and some radiated to exploit more distantly related hosts [8][9][10]. ...
... C. babae corresponded to the concept of promiscuous alloparasites [3] which describes red algal parasites that grow on several hosts in nature, with at least one of the hosts not closely related to the parasites. The present study also concurred with previous molecular studies [7][8][9][10], in which red algal parasites infect only hosts within the same family, even in cases of parasite species that have radiated or switched to a secondary host species. ...
Congracilaria babae was first reported as a red alga parasitic on the thallus of Gracilaria salicornia based on Japanese materials. It was circumscribed to have deep spermatangial cavities, coloration similar to its host and the absence of rhizoids. We observed a parasitic red alga with morphological and anatomical features suggestive of C. babae on a Hydropuntia species collected from Sabah, East Malaysia. We addressed the taxonomic affinities of the parasite growing on Hydropuntia sp. based on the DNA sequence of molecular markers from the nuclear, mitochondrial and plastid genomes (nuclear ITS region, mitochondrial cox1 gene and plastid rbcL gene). Phylogenetic analyses based on all genetic markers also implied the monophyly of the parasite from Hydropuntia sp. and C. babae, suggesting their conspecificity. The parasite from Hydropuntia sp. has a DNA signature characteristic to C. babae in having plastid rbcL gene sequence identical to G. salicornia. C. babae is likely to have evolved directly from G. salicornia and subsequently radiated onto a secondary host Hydropuntia sp. We also recommend the transfer of C. babae to the genus Gracilaria and propose a new combination, G. babae, based on the anatomical observations and molecular data.
... We believe that it is unlikely that the Pterocladiophilaceae constitutes a natural allparasitic family. Our data presented here and elsewhere (Goff et al. 1996Goff et al. , 1997) indicate that parasites rarely infect hosts outside their family and never FIG 1. ML reconstruction of Gracilariales samples based on SSU DNA sequences (hLRT-derived parameters, ML 5 – 5671.56). Underlines indicate parasite and host samples (seeTable 1). ...
... An exception is the parasite Harveyella mirabilis, which parasitizes a member of the Delesseriaceae, Gonimophyllum skottsbergii; this host is also an adelphoparasite that parasitizes Cryptopleura crispa, a case of hyperparasitism. Like other studies of adelphoparasites (Goff et al. 1996Goff et al. , 1997), we found that the parasite Gonimophyllum skottsbergii is more closely related to its host than the host (Cryptopleura crispa) is to other species in the genus (C. ramosa). ...
... Though both parasites are closely related to Bostrychia radicans, only additional sampling, and more variable genes, will reveal if the parasites have a common origin. The observation that these two parasite genera are geographically distant and have very different early development (Zuccarello and West 1994a) would indicate that they have independent origins, as has been found in other parasites (Goff et al. 1996Goff et al. , 1997). The fact that the Bostrychia parasites are closely related to their hosts raises the question of why their ability to transform their host is so different from that of other adelphoparasites (Goff and Zuccarello 1994). ...
Red algal parasites are common and have a unique type of development in which parasite nuclei are transferred to host cells and “control” host cell development. Previous phylogenetic studies have concentrated on parasites closely related to their hosts, termed adelphoparasites. A second set of parasites, usually classified in a different family or tribe from their host, termed alloparasites, have not been studied phylogenetically. This study concentrates on the wholly parasitic family, the Choreocolacaceae (Gigartinales). Using small subunit rDNA sequence data, we found that all the parasites studied are within the same family as their host. Our data support the placement of Holmsella, species of which parasitize Gracilaria and Gracilariopsis, in the order Gracilariales and suggest that Holmsella is an old parasitic genus. Most other species of the Choreocolacaceae parasitize species of the Rhodomelaceae. The one exception is the hyperparasitism between Harveyella mirabilis (Reinsch) F. Schmitz et Reinke (Rhodomelaceae) and the parasite Gonimophyllum skottsbergii Setchell (Delesseriaceae). The parasites Bostrychiocolax australis Zuccarello et West and Dawsoniocolax bostrychiae (Joly et Yamaguishi-Tomita) Joly et Yamaguishi-Tomita are placed within the tribe Bostrychiae as are their hosts. Harveyella mirabilis has a single origin and has switched hosts several times during its passage between the Atlantic and Pacific Oceans. Evidence does not support the continued recognition of the family Choreocolacaceae. Our results also indicate that the distinction between adelphoparasites and alloparasites is unwarranted, with a continuum between newly evolved parasites closely related to their hosts and parasites less closely related to their hosts.
... Both must be considered alloparasites in contrast to most (90%) other red algal parasites, which are adelphoparasites. The latter occurs on hosts to which they are closely related, whereas the former occurs on unrelated hosts (Goff et al. 1997). Adelphoparasites have been shown to have evolved either directly from their hosts or from a very closely related host (Goff et al. 1997). ...
... The latter occurs on hosts to which they are closely related, whereas the former occurs on unrelated hosts (Goff et al. 1997). Adelphoparasites have been shown to have evolved either directly from their hosts or from a very closely related host (Goff et al. 1997). Although alloparasites are found on unrelated hosts, they are thought to have arisen first as an adelphoparasite that secondarily moved to another less directly related host. ...
... Although alloparasites are found on unrelated hosts, they are thought to have arisen first as an adelphoparasite that secondarily moved to another less directly related host. This conclusion is supported by cross-hybridization and infection studies as well as molecular sequence data (Goff et al. 1997). ...
The major diagnostic features for erecting the red algal subfamily Choreonematoideae (Corallinales) were a combination of 1) absence of both cell fusions and secondary pit connections, 2) conceptacle roof and wall comprised of a single cell layer, and 3) presence of tetrasporangial pore plugs within a uniporate conceptacle in the monotypic taxon Choreonema thuretii (Bornet) Schmitz. Because this alga is a parasite, the absence of secondary cell connections is most likely an adaptation to a reduced thallus. This study shows that all conceptacles are not composed of a file of cells but rather a single layer of epithallial cells that are underlain by a thick layer of calcified acellular material; both epithallial cells and the calcified layer are produced by peripheral sterile cells. Although the outermost tetrasporangial pore canal is uniporate, there is a calcified acellular multiporate plate recessed just below the rim. The plate is produced by interspersed sterile cells and is continuous with the calcified layer supporting the conceptacle. These unique structures are likely due to parasitism rather than to the ancestral state. Based on these results and a reexamination of published micrographs depicting lenticular cells in Austrolithon intumescens Harvey et Woelkerling, we propose that both subfamily Choreonematoideae and Austrolithoideae are closely allied with subfamily Melobesioideae. This distant relationship to its host (Corallinoideae) plus a combination of unique conceptacle and unusual type of parasitism indicates that C. thuretii is an alloparasite and that it is likely the most ancient red algal parasite studied to date.
... The majority of red algal parasites exist in the continuum between these poles of single host adelphoparasites and promiscuous alloparasites (see above image). This brings into question whether or not the designation of particular taxa as adelpho-or alloparasites is still useful in the context of molecular investigations, with several authors calling for the terms to be avoided altogether [26, 31, 42, 47]. N. A. Blouin and C. E. Lane Prospects & Overviews ...
... Parasites within the florideophyte red algae were initially classified based on morphological characteristics in the early 20th century [23]. Consistent with an idea popular at the time for parasitism in animals, they were assumed to have evolved from their hosts242526. Starting in the mid 20th century, many parasites were re-classified based on reproductive development . ...
... This, however, remains to be tested formally. Currently, adelphoparasites are believed to be more recently diverged than alloparasites, and there is some molecular data to support this idea [26, 31,45464748. In this context, red algal parasite lineages must initially evolve as an adelphoparasite with a single host. ...
Many of the most virulent and problematic eukaryotic pathogens have evolved from photosynthetic ancestors, such as apicomplexans, which are responsible for a wide range of diseases including malaria and toxoplasmosis. The primary barrier to understanding the early stages of evolution of these parasites has been the difficulty in finding parasites with closely related free-living lineages with which to make comparisons. Parasites found throughout the florideophyte red algal lineage, however, provide a unique and powerful model to investigate the genetic origins of a parasitic lifestyle. This is because they share a recent common ancestor with an extant free-living red algal species and parasitism has independently arisen over 100 times within this group. Here, we synthesize the relevant hypotheses with respect to how these parasites have proliferated. We also place red algal research in the context of recent developments in understanding the genome evolution of other eukaryotic photosynthesizers turned parasites.
... Previous studies of marine symbioses between marine red algae and their parasites have demonstrated the utility of molecular methods for assessing coevolutionary relationships (Goff et al. 1996(Goff et al. , 1997. Similarly, host specificity and coevolution of marine algae with gall-inducing Proteobacteria have been shown using internal transcribed spacer (ITS) and 16S ribosomal DNA (rDNA) sequence data from the red alga Prionitis and its bacterial symbionts respectively (Ashen & Goff 2000). ...
... Furthermore, mitochondrial haplotype and nuclear gene phylogenies have been compared among organisms and with shifting phenotypic traits across wide geographic distributions to characterize dynamic interactions in coevolving plant-insect associations (Althoff & Thompson 1999;Thompson 1999). Additionally, genetic evidence can be a welcome addition to morphological assessment given the potential for phenotypic convergence among symbionts due to evolutionary pressures common to their shared habitat (Dowton & Austin 1994;Goff et al. 1997;Ronquist 1994). ...
... Instances of congruence between fungal endophyte and host phylogenies exist for H. irritans group 1 and group 4 sequences and their associated algal hosts. Such topological similarity in phylogenies has been used to indicate cospeciation in algal relationships with other algae, fungi and bacteria thought to have coevolved (Ashen & Goff 2000;Goff et al. 1996Goff et al. , 1997Kroken & Taylor 2000). With respect to H. irritans sequences from La Jolla Cove, endophyte and host phylogenies appear incongruent because comparatively divergent fungal sequences from groups 2 and 4 occur on C. osmundacea hosts that are highly similar genetically. ...
The fungal endophyte Haloguignardia irritans induces gall formation on the brown algal genera Cystoseira and Halidrys occurring from Oregon to Baja California, Mexico. Here we examine genetic covariation and compare rDNA phylogenies to investigate the coevolutionary histories of H. irritans and its algal hosts. Despite recognition of H. irritans as a single morphological species, internal transcribed spacer rDNA sequences representative of its geographic range are characterized by sequence variation at the intraspecific to intrageneric levels. An assessment of parallel cladogenesis between endophyte and host phylogenies provides evidence for a combination of independent fungal divergence and host jumping, similar to that observed in terrestrial lichens. Our results suggest that reduced gene flow due to geographic isolation is a major contributing factor to more concerted covariation observed at one island site, rather than to differences among algal host species alone. Because geography and its effects on gene flow can create heterogeneous mosaics of coevolution for symbioses in terrestrial environments, our results support the notion that conservation efforts toward the maintenance of genetic diversity in marine environments should likewise consider geographic complexity and its effects on coevolving marine species.
... As presented in the next section, using the fusion model for the origin viruses as a working hypothesis, I identified several bacterial, archaeal, and eukaryal species that might be evolving into molecular organisms. Surprisingly though, for more than a century, researchers have been studying parasitic algae (71) and fungi (72) that do develop a molecular structure within their host cells (73)(74)(75)(76)(77)(78)(79)(80)(81). Remarkably, these parasites fuse with their host cells and develop as molecular organisms. ...
... Similar to archaeal and bacterial parasitic species, there are also numerous eukaryal parasitic species, such as the algae and fungi, which might be evolving into molecular organisms. Remarkably, it appears that some of these parasitic species are already true parasitic molecular organisms, although currently they are not recognized as such (73)(74)(75)(76)(77)(78)(79)(80)(81). As predicted by the fusion model for the origin of AVs, these fungal and algal parasites: (a) fuse with their host cells, (b) develop a molecular structure, (c) replicate their genome and synthesize their other specific molecules using the host cell resources, and (d) generate cell-like reproductive forms that differentiate into spores, which start a new life cycle by fusing with other host cells [reviewed in (73)(74)(75)(76)(77)(78)(79)(80)(81)]. ...
... Remarkably, it appears that some of these parasitic species are already true parasitic molecular organisms, although currently they are not recognized as such (73)(74)(75)(76)(77)(78)(79)(80)(81). As predicted by the fusion model for the origin of AVs, these fungal and algal parasites: (a) fuse with their host cells, (b) develop a molecular structure, (c) replicate their genome and synthesize their other specific molecules using the host cell resources, and (d) generate cell-like reproductive forms that differentiate into spores, which start a new life cycle by fusing with other host cells [reviewed in (73)(74)(75)(76)(77)(78)(79)(80)(81)]. ...
Viruses are the most abundant life forms and the repertoire of viral genes is greater than that of cellular genes. It is also evident that viruses have played a major role in driving cellular evolution, and yet, viruses are not part of mainstream biology, nor are they included in the Tree of Life. A reason for this major paradox in biology is the misleading dogma of viruses as viral particles and their enigmatic evolutionary origin. This article presents an alternative view about the nature of viruses based on their properties during the intracellular stage of their life cycle, when viruses express features comparable to those of many parasitic cellular species. Supporting this view about the nature of viruses is a novel hypothetical evolutionary model for their origin from parasitic cellular species that fused with their host cells. By losing their membrane and cellular structure within the host cell, these new types of parasitic species gained full access to precursors for the synthesis of their specific molecules and to the host’s information processing machineries, such as translation, which created unique parasitic and evolutionary opportunities. To identify viruses during their intracellular stage of their life cycle, in which their specific molecules are free or dispersed within the host cell, this paper introduces the concept of “molecular structure” and labels viruses as “molecular organisms.” Among the extant viruses, the life cycle of poxviruses and other complex viruses that fuse with their host cells provides compelling evidence for the fusion model. One of the most remarkable implications of fusion model is that new viral lineages originated from parasitic cellular species throughout the history of life, and that this process might still be active. Surprisingly, it appears that several parasitic cellular species are currently evolving into molecular organisms. More remarkably though, according to this model, several parasites that are currently classified as cellular organisms are in fact genuine molecular organisms. The current evidence for the fusion hypothesis is strong and it is fully testable using both experimental and phylogenetic approaches. The academic and research implications of this model, which supports the inclusion of viruses in the Tree of Life, are highly significant. Some of these implications are discussed in more detail in two other articles of this series, which presents a unifying model for the origin and evolution of cellular and viral domains, including the origin of life.
... 85 Red algal parasites mostly infect members of the same family (Goff et al. 1996, Preuss and 86 Zuccarello 2014 or occasionally different families within the same order (Zuccarello et al. 87 2004). The close relationships between many red algal parasites and their hosts led to the 88 proposition that red algal parasites evolved from their host (Setchell 1918, Goff et al. 1997. 89 Phylogenetic analyses demonstrated that some parasites and their host are more closely related to 90 each other than to other species in the same host genus (Goff et al. 1997, Zuccarello et al. 2004 Preuss and Zuccarello 2017), whereas other parasites are more distantly related to their host 92 species, possibly due to host switching (Kurihara et al. 2010, Preuss and Zuccarello 2014. ...
... The close relationships between many red algal parasites and their hosts led to the 88 proposition that red algal parasites evolved from their host (Setchell 1918, Goff et al. 1997. 89 Phylogenetic analyses demonstrated that some parasites and their host are more closely related to 90 each other than to other species in the same host genus (Goff et al. 1997, Zuccarello et al. 2004 Preuss and Zuccarello 2017), whereas other parasites are more distantly related to their host 92 species, possibly due to host switching (Kurihara et al. 2010, Preuss and Zuccarello 2014. 93 In addition, red algal parasites exhibit a unique organelle transfer mechanism of infection 94 by forming a connection between a parasite and a host cell, called a secondary pit connection Accepted Article Coleman 1984, 1985), leading to cells containing cellular components of both species 96 ("heterokaryons") within the host and parasite thallus. ...
Comparative organelle genome studies of parasites can highlight genetic changes that occur during the transition from a free‐living to a parasitic state. Our study focuses on a poorly studied group of red algal parasites, which are often closely related to their red algal hosts and from which they presumably evolved. Most of these parasites are pigmented and some show photosynthetic capacity. Here, we assembled and annotate the complete organelle genomes of the photosynthetic red algal parasite, Pterocladiophila hemisphaerica. The plastid genome is the smallest known red algal plastid genome at 68,701 bp. The plastid genome has many genes missing, including all photosynthesis‐related genes. In contrast, the mitochondrial genome is similar in architecture to that of other free‐living red algae. Both organelle genomes show elevated mutation rates and significant changes in patterns of selection, measured as dN/dS ratios. This caused phylogenetic analyses, even of multiple aligned proteins, to be unresolved or give contradictory relationships. Full plastid datasets
interfered by selected best gene evolution models showed the supported relationship of P. hemisphaerica within the Ceramiales, but the parasite was grouped with support as sister to the Gracilariales when interfered under the GHOST model. Nuclear rDNA showed a supported grouping of the parasite within a clade containing several red algal orders including the Gelidiales. This photosynthetic parasite which is unable to photosynthesize with its own plastid, due to the total loss of all photosynthesis genes, raises intriguing questions on parasite‐host organelle genome capabilities and interactions.
... taxonomy) of parasites is complicated by their reduced thalli and consequent lack of diagnostic morphological characters, leading to diversity being underreported (Zuccarello and West 1994a). The ability of many parasites to switch hosts and infect multiple hosts, and the propensity of phycologists to name parasites based on hosts, further complicate the interpretation of their (Goff et al. 1996(Goff et al. , 1997, and have led to multiple names for some taxa that are found on multiple hosts (Zuccarello and West 1994a). An example is Asterocolax gardneri (Setchell) Feldmann et Feldmann, where phylogenetic results indicate that the species has three independent origins from Phycodrys setchellii, Phycodrys isabelliae and Polyneura latissima (i.e. a polyphyletic A. gardneri; Goff et al. 1997). ...
... The ability of many parasites to switch hosts and infect multiple hosts, and the propensity of phycologists to name parasites based on hosts, further complicate the interpretation of their (Goff et al. 1996(Goff et al. , 1997, and have led to multiple names for some taxa that are found on multiple hosts (Zuccarello and West 1994a). An example is Asterocolax gardneri (Setchell) Feldmann et Feldmann, where phylogenetic results indicate that the species has three independent origins from Phycodrys setchellii, Phycodrys isabelliae and Polyneura latissima (i.e. a polyphyletic A. gardneri; Goff et al. 1997). Without further information on their phylogeny or more detailed morphological investigations, the origins of parasites and their true diversity remain to be uncovered. ...
Red algal parasites are diverse organisms that are unusual due to the fact that many are closely related to their hosts. Parasitism has developed many times within different red algal groups, but the full extent of parasite biodiversity is unknown, as parasites are easily overlooked due to their small size and often low abundance. Additionally, the literature on red algal parasites is dispersed and has not been compiled in over 30 years. Although criteria have been proposed to define what constitutes a red algal parasite, many parasites are poorly described, and the cellular interactions with their host are poorly known. A few studies have demonstrated that parasites transfer organelles to host cells, which can alter the physiology of the host to the benefit of the parasite. Here, we apply a set of defining criteria for parasites to a compiled list of all described red algal parasites. Our results highlight the lack of knowledge of many key parasitic processes including early parasite development, host cell “control”, and parasite origin. Until the biology of more parasites is studied, generalisations on the processes of parasitism in red algae may be premature. We hope this synopsis will stimulate research into this fascinating group.
... Red algal parasites are common on other red algae and have been described from several orders within the Florideophyceae (Goff 1982), a few molecular-based phylogenetic studies have focused on a handful of species (Goff et al. 1997, Zuccarello et al. 2004, Ng et al. 2013, with new species still being described (Kim and Cho 2010). ...
... Due to the morphological and genetic similarity of red algal parasite and host, it has been suggested that the parasite evolved from its host (Goff et al. 1997, Blouin and Lane 2012, Ng et al. 2013. For example, the parasite Congracilaria babae Yamamoto is more closely related to its host Gracilaria salicornia (C. ...
Red algal parasites are common within red algae and are mostly closely related to their hosts, but have a reduced habit. In the past, red algal parasites, due to their reduced morphology, have been given distinct generic names, even though they are often phylogenetically nested in their host’s genus. This is a problem nomenclaturally for maintenance of a taxonomy based on monophyly. This study investigates the morphology, genetic variation and distribution of an undescribed red algal parasite growing on its host Rhodophyllis membranacea, widely distributed throughout New Zealand. Microscopy, molecular markers (plastid, mitochondrial, nuclear), and herbarium investigation were used to investigate this species. The parasite is widely distributed throughout New Zealand. All molecular markers clearly show that the parasite is almost identical to the host, even though morphologically quite distinct from members of the host genus. We believe that to maintain monophyly of Rhodophyllis the parasite should be described as a new species of Rhodophyllis, Rhodophyllis parasitica sp. nov. We also recommend that in order to maintain generic monophyly most red algal parasite genera should also be transferred to their host genus.
... DNA sequences from Malaysian parasites and from C. babae collected in Japan were compared to ascertain whether the two are conspecific despite some anatomical variations. Previous studies of the evolutionary relationships between red algal parasites and their hosts that have utilized molecular approaches have used genetic markers of nuclear origin, including the small subunit (SSU) rRNA gene, the internal transcribed spacer (ITS) region, and the large subunit (LSU) rRNA gene (Goff et al. 1996(Goff et al. , 1997Zuccarello et al. 2004;Kurihara et al. 2010). Kurihara et al. (2010) showed that the shorter LSU rRNA gene fragment (~620-650 bp) provided more sequence variations compared to the longer portion of the SSU rRNA gene (~1,100 bp). ...
... As such, the LSU rRNA gene was used in addition to the ITS region of the nuclear ribosomal repeat to determine the evolutionary relationships of the red algal parasites and their hosts. The ITS region is not subject to horizontal gene transfer between species and has been demonstrated to include sufficient informative characters for such analyses (Goff et al. 1996(Goff et al. , 1997. DNA analyses of the plastid rbcL gene and the mitochondrial cox1 gene were also conducted in this study, as sequences of rbcL have commonly been used to infer the phylogenetic position of Gracilariaceae up to the species level (Gurgel and Fredericq 2004), whereas the cox1 gene has been established as the universal DNA barcode for species identification in red algae (Saunders 2005;Robba et al. 2006). ...
The present study compares genetic structure from the plastid rbcL, mitochondrial cox1, and nuclear internal transcribed spacer (ITS) sequences among 13 populations of Gracilaria salicornia and its red algal parasite, G. babae, in Malaysia. Owing to the unique biology of the red algal parasite, identical phylogeographies were inferred from the rbcL and cox1 sequences in both G. babae and its host, G. salicornia. Despite the low genetic variation, rbcL and cox1 showed a concordant phylogeographic split that largely corresponds to Peninsular Malaysia and East Malaysia, except for a sample from East Malaysia that was consistently grouped with samples from the peninsula. On the other hand, G. salicornia was separated from G. babae in the midpoint-rooted phylogeny inferred from ITS data despite the failure to retrieve the two taxa in reciprocal monophyly. Gracilaria salicornia was less diverse and lacked apparent geographic structure. In contrast, the ITS data revealed considerable genetic diversity and fine-scale genetic structuring in G. babae within Malaysian waters, probably as a result of adaptation to the local host population.
... Red algal parasites are common on other red algae and have been described from several orders within the Florideophyceae (Goff 1982), a few molecular-based phylogenetic studies have focused on a handful of species (Goff et al. 1997, Zuccarello et al. 2004, Ng et al. 2013, with new species still being described (Kim and Cho 2010). ...
... Due to the morphological and genetic similarity of red algal parasite and host, it has been suggested that the parasite evolved from its host (Goff et al. 1997, Blouin and Lane 2012, Ng et al. 2013. For example, the parasite Congracilaria babae Yamamoto is more closely related to its host Gracilaria salicornia (C. ...
What's in a name? Monophyly of genera in the red algae: Rhodophyllis parasitica sp. nov. (Gigartinales, Rhodophyta); a new red algal parasite Red algal parasites are common within red algae and are mostly closely related to their hosts, but have a reduced habit. In the past, red algal parasites, due to their reduced morphology, have been given distinct generic names, even though they are often phylogenetically nested in their host's genus. This is a problem nomenclaturally for maintenance of a taxonomy based on monophyly. This study investigates the morphology, genetic variation and distribution of an unde-scribed red algal parasite growing on its host Rhodophyllis membranacea, widely distributed throughout New Zealand. Microscopy, molecular markers (plastid, mitochondrial, nuclear), and herbarium investigation were used to investigate this species. The parasite is widely distributed throughout New Zealand. All molecular markers clearly show that the parasite is almost identical to the host, even though morphologically quite distinct from members of the host genus. We believe that to maintain monophyly of Rhodophyllis the parasite should be described as a new species of Rhodophyllis, Rhodophyllis parasitica sp. nov. We also recommend that in order to maintain generic monophyly most red algal parasite genera should also be transferred to their host genus.
... DNA sequences from Malaysian parasites and from C. babae collected in Japan were compared to ascertain whether the two are conspecific despite some anatomical variations. Previous studies of the evolutionary relationships between red algal parasites and their hosts that have utilized molecular approaches have used genetic markers of nuclear origin, including the small subunit (SSU) rRNA gene, the internal transcribed spacer (ITS) region, and the large subunit (LSU) rRNA gene (Goff et al. 1996(Goff et al. , 1997Zuccarello et al. 2004;Kurihara et al. 2010). Kurihara et al. (2010) showed that the shorter LSU rRNA gene fragment (~620-650 bp) provided more sequence variations compared to the longer portion of the SSU rRNA gene (~1,100 bp). ...
... As such, the LSU rRNA gene was used in addition to the ITS region of the nuclear ribosomal repeat to determine the evolutionary relationships of the red algal parasites and their hosts. The ITS region is not subject to horizontal gene transfer between species and has been demonstrated to include sufficient informative characters for such analyses (Goff et al. 1996(Goff et al. , 1997. DNA analyses of the plastid rbcL gene and the mitochondrial cox1 gene were also conducted in this study, as sequences of rbcL have commonly been used to infer the phylogenetic position of Gracilariaceae up to the species level (Gurgel and Fredericq 2004), whereas the cox1 gene has been established as the universal DNA barcode for species identification in red algae (Saunders 2005;Robba et al. 2006). ...
A phylogenetic study of two parasites found on the common host species Gracilaria salicornia from Japan and Malaysia based on nuclear, plastid, and mitochondrial molecular markers was conducted. The Japanese and Malaysian parasites were placed in the same cluster in the nuclear phylogenies inferred from the LSU rRNA gene and ITS region, supporting the monophyly of these parasites despite the slight anatomical variations observed. In addition to the molecular analyses, shared morphological and reproductive features including the lack of rhizoids, similar coloration to hosts, and the presence of deep spermatangial conceptacles supported the inclusion of both the Japanese and Malaysian parasites in Congracilaria babae. Phylogenetic analyses based on ITS sequences indicated that C. babae most likely evolved directly from its current host species, G. salicornia. C. babae was shown to be a member of Gracilaria sensu stricto along with its host. C. babae growing on G. salicornia is characterized by having plastid rbcL and mitochondrial cox1 gene sequences identical to those of its host, whereas the nuclear LSU rRNA gene and ITS region sequences are different from those of its host.
... Where the parasite is the host's closest phylogenetic relative (Emery's rule in the strict sense), it is likely to have originated through sympatric speciation. However, the reproductive isolation mechanisms required for sympatric speciation are complex (Bourke & Franks, 1991) and this type of speciation is rarely supported by phylogenetic studies (for exceptions, see Goff et al., 1997;Sumner et al., 2004). In contrast, when parasites and hosts are close relatives, but not sibling species (loose version of Emery's rule), they are likely to originate from allopatric speciation, following straightforward evolutionary scenarios. ...
... In contrast, when parasites and hosts are close relatives, but not sibling species (loose version of Emery's rule), they are likely to originate from allopatric speciation, following straightforward evolutionary scenarios. Evidence for such speciation events are numerous (Carpenter et al., 1993;Ward, 1996;Goff et al., 1997;Lowe & Crozier, 1997;Sanetra & Buschinger, 2000;Lowe et al., 2002;Parker & Rissing, 2002;Janda et al., 2004;Sumner et al., 2004;Pitts et al., 2005). However, to determine the actual evolutionary scenario that produced extant host-parasite systems can only be speculative because of the lack of historical information on the origins of and interactions between the species (Via, 2001). ...
The recent invasion by self-replicating socially parasitic Cape honeybee workers, Apis mellifera capensis, of colonies of the neighbouring African subspecies Apis mellifera scutellata represents an opportunity to study evolution of intraspecific parasitism in real time. As honeybee workers compete pheromonally for reproductive dominance, and as A. m. capensis workers readily produce queen-like pheromones, we hypothesized that these semiochemicals promoted the evolution of intraspecific social parasitism. Remarkably, the offspring of a single worker became established as a parasite in A. m. scutellata's range. This could have resulted from extreme selection among different clonal parasitic worker lineages. Using pheromonal contest experiments, we show that the selected parasitic lineage dominates in the production of mandibular gland pheromones over all other competitors to which it is exposed. Our results suggest that mandibular gland pheromones played a key role in the evolution of intraspecific social parasitism in the honeybee and in the selection of a single genotype of parasitic workers.
... Molecular phylogenetics show different evolutionary relationships of these parasites to their hosts (e.g., Goff et al., 1996;Kurihara et al., 2010;Preuss & Zuccarello, 2018). Most parasites are closely related to their hosts, often grouping with the host as its closest relative, indicating that the parasite evolved recently (Goff et al., 1997;Ng et al., 2014). In other cases, the parasites are phylogenetically distant from their hosts, and their closest relative is a non-host species (Goff et al., 1996;Kurihara et al., 2010;Preuss & Zuccarello, 2018;Zuccarello et al., 2004). ...
Parasitic red algae are an interesting system for investigating the genetic changes that occur in parasites. These parasites have evolved independently multiple times within the red algae. The functional loss of plastid genomes can be investigated in these multiple independent examples, and fine-scale patterns may be discerned. The only plastid genomes from red algal parasites known so far are highly reduced and missing almost all photosynthetic genes. Our study assembled and annotated plastid genomes from the parasites Janczewskia tasmanica and its two Laurencia host species (Laurencia elata and one unidentified Laurencia sp. A25) from Australia and Janczewskia verruciformis, its host species (Laurencia catarinensis), and the closest known free-living relative (Laurencia obtusa) from the Canary Islands (Spain). For the first time we show parasitic red algal plastid genomes that are similar in size and gene content to free-living host species without any gene loss or genome reduction. The only exception was two pseudogenes (moeB and ycf46) found in the plastid genome of both isolates of J. tasmanica, indicating potential for future loss of these genes. Further comparative analyses with the three highly reduced plastid genomes showed possible gene loss patterns, in which photosynthetic gene categories were lost followed by other gene categories. Phylogenetic analyses did not confirm monophyly of Janczewskia, and the genus was subsumed into Laurencia. Further investigations will determine if any convergent small-scale patterns of gene loss exist in parasitic red algae and how these are applicable to other parasitic systems.
... Traditionally, the relationships between parasites and their hosts have been studied in terms of morphological and reproductive features (Guimarães 1993, Apt and Schlech 1998, Fujii and Guimarães 1999, Kraft and Abbott 2002, Vergés et al. 2005, Kim and Cho 2010. In recent years, the molecular diversity of red algal parasites has been uncovered, with descriptions of new species, new taxonomic proposals, and a better understanding of evolutionary origin and phylogenetic relationships (Goff et al. 1997, Zuccarello et al. 2004, Kurihara et al. 2010, Ng et al. 2014a,b, Preuss and Zuccarello 2018 (Joly 1966, Joly and Oliveira Filho 1966, Joly and Yamaguishi-Tomita 1967, Oliveira Filho and Ugadim 1973, Yoneshigue and Oliveira Filho 1984, Yoneshigue 1985, Fujii and Guimarães 1999. Except for G. africanum and J. moriformis, all the other representatives were described from Brazil. ...
The monotypic red algal parasite genus Spyridiocolax was proposed from material from the coast of Espírito Santo to accommodate Spyridiocolax capixabus , endemic from Brazil. The species is rare, and we performed a morphological reappraisal and the first molecular characterization of S. capixabus . Parasite specimens growing on Spyridia clavata were collected in the type locality, Itaoca Beach, Espírito Santo. Spyridiocolax capixabus forms colorless warts on the branches of S. clavata , and the secondary pit connections were described for the first time. Male, female and tetrasporophytic structures were observed growing in the same host plant. The plastid rbc L sequences of parasite and host were identical. A divergence of one nucleotide was found to the nuclear SSU rRNA gene, suggesting that the parasite retains the chloroplast of its host. Both plastidial and nuclear phylogenies supported the close relationship of S. capixabus and S. clavata . The data obtained corroborate other studies with rhodophycean parasites, which show morphological and molecular similarities between parasites and hosts. To maintain the monophyly of the host genus, the transfer of S. capixabus to Spyridia is proposed here on the basis of morphological and molecular evidence. Our study constitutes a starting point for reinvestigating the red algal parasites in Brazil.
... Mitochondrial marker (cox1) shows that the parasite Vertebrata aterrimophila is genetically similar to, and shares a common origin with, its host Vertebrata aterrima. Many red algal parasites in the Ceramiales show a close host-parasite relationship (Goff et al., 1997;Zuccarello et al., 2004;Kurihara et al., 2010;Preuss & Zuccarello, 2018). Previous morphological descriptions placed many parasites in independent parasitic genera (Kraft & Abbott, 2002;Kim & Cho, 2010), due to their obvious morphological differences from their hosts (e.g. ...
Parasitic red algae grow only on other red algae and have over 120 described species. Developmental studies in red algal parasites are few, although they have shown that secondary pit connections formed between parasite and host and proposed that this was an important process in successful parasitism. Furthermore, it was recorded that the transfer of parasite nuclei by these secondary pit connections led to different host cell effects. We used developmental studies to reconstruct early stages and any host cell effects of a parasite on Vertebrata aterrima. A mitochondrial marker (cox1) and morphological observations (light and fluorescence microscopy) were used to describe this new red algal parasite as Vertebrata aterrimophila sp. nov. Early developmental stages show that a parasite spore connects via secondary pit connections with a pericentral host cell after cuticle penetration. Developmental observations revealed a unique connection cell that grows into a ‘trunk-like’ structure. Host cell transformation after infection by the parasite included apparent increases in both carbohydrate concentrations and nuclear size, as well as structural changes. Analyses of molecular phylogenies and reproductive structures indicated that the closest relative of V. aterrimophila is its host, V. aterrima. Our study shows a novel developmental parasite stage (‘trunk-like’ cell) and highlights the need for further developmental studies to investigate the range of developmental patterns and host effects in parasitic red algae.
... Some parasitic rhodophytes obtain nourishment from other, closely related rhodophytes, and are believed to represent evolutionary derivatives of their hosts (rhodophyte adelphoparasitism, cf. Goff and Zuccarello, 1994;Goff et al., 1996Goff et al., , 1997. Endophytic phaeophytes may be pathogens in other phaeophytes, causing tumors and deformations such as twisted stripes and blades (Apt, 1988;Heesch and Peters, 1999). ...
Sublagenicula nuda lycophyte megaspores from the upper Visean of central France frequently host a colonial green alga as an endophyte. This association was first recorded more than 100 years ago by the French paleobotanist B. Renault, who introduced the name Lageniastrum macrosporae for the alga. However, the biological significance of the discovery was not fully assessed until recently. The L. macrosporae-S. nuda association represents the oldest compelling fossil evidence for algal endophytes in land plants, and the only example to date of an alga residing in the interior of spores of vascular cryptogams. Here we present a detailed re-evaluation and photographic documentation of the surviving original specimens from the Visean of Combres/Lay and Esnost. Moreover, a newly discovered specimen from the Stephanian of central France represents the first record of this association from the Upper Carboniferous. An emended diagnosis for L. macrosporae Renault, 1896 is provided, and a lectotype and paralectotype are designated. Although L. macrosporae displays a striking suite of morphological characters found in members of the extant chlorophyte family Volvocaceae (especially the genus Volvox), the peculiar biology of the fossil necessitates establishment of a new family, for which the name Lageniastraceae is proposed. Considerations of the adaptive advantages for the alga of occupying the interior of megaspores are offered. These include the possible effectiveness of the spores in protection during periods of desiccation and against plankton-feeding animals, and use of the spores as potential vectors for dispersal from one isolated body of water to another by spore-feeding animals. (c) 2005 Elsevier SAS. All rights reserved.
... Its persistence and its reactivation would imply that: (a) the process of cell division (nuclear envelope dispersion and reformation), (b) mitotic duplication (doubling of the chromosomes and allocating them to the progeny cells) and (c) the viral DNA correspond to the sexual reproductive cycle of the host organism. Such an infectious origin for the nucleus would also be compatible for the prevalence of infectious nuclei, seen in many species of parasitic red algae that represent a basal eukaryote (Goff et al., 1997). Read algae are clearly the oldest eukaryote that can be found in the fossil record. ...
... Some parasitic rhodophytes obtain nourishment from other, closely related rhodophytes, and are believed to represent evolutionary derivatives of their hosts (rhodophyte adelphoparasitism, cf. Goff and Zuccarello, 1994;Goff et al., 1996Goff et al., , 1997. Endophytic phaeophytes may be pathogens in other phaeophytes, causing tumors and deformations such as twisted stripes and blades (Apt, 1988;Heesch and Peters, 1999). ...
... Some plastids have completely lost photosynthetic capacity, a prominent example being the apicoplast of apicomplexans. Multiple instances of conversion into nonphotosynthetic plastids have also occurred within cryptophytes, dinoflagellates, euglenids, stramenopiles, red algae and Viridiplantae (Goff et al. 1997 ; HoefEmden and Melkonian 2003 ; Nudelman et al. 2003 ; Bungard 2004 ; De Koning and Keeling 2006) . Retention of nonphotosynthetic plastids and their genomes is due to the fact that these organelles carry out a variety of important metabolic processes in addition to photosynthesis, including amino acid and fatty acid biosynthesis (Mazumdar et al. 2006) . ...
Plastids, the light-harvesting organelles of plants and algae, are the descendants of cyanobacterial endosymbionts that became
permanent fixtures inside nonphotosynthetic eukaryotic host cells. This chapter provides an overview of the structural, functional
and molecular diversity of plastids in the context of current views on the evolutionary relationships among the eukaryotic
hosts in which they reside. Green algae, land plants, red algae and glaucophyte algae harbor double-membrane-bound plastids
whose ancestry is generally believed to trace directly to the original cyanobacterial endosymbiont. In contrast, the plastids
of many other algae, such as dinoflagellates, diatoms and euglenids, are usually bound by more than two membranes, suggesting
that these were acquired indirectly via endosymbiotic mergers between nonphotosynthetic eukaryotic hosts and eukaryotic algal
endosymbionts. An increasing amount of genomic data from diverse photosynthetic taxa has made it possible to test specific
hypotheses about the evolution of photosynthesis in eukaryotes and, consequently, improve our understanding of the genomic
and biochemical diversity of modern-day eukaryotic phototrophs.
... The phenomenon of parasites being closely related to their hosts is seen across the tree of life. In attacking closely related species, T. fratricida also functions as an adelphoparasite , similar to species of parasitic red algae or mistletoe ( Goff et al., 1997 ). ...
Premise of study:
This research seeks to advance understanding of conditions allowing movement of fungal pathogens among hosts. The family Clavicipitaceae contains fungal pathogens exploiting hosts across three kingdoms of life in a pattern that features multiple interkingdom host shifts among plants, animals, and fungi. The tribe Ustilaginoideae potentially represents a third origin of plant pathogenesis, although these species remain understudied. Fungal pathogens that cause ergot are linked morphologically with Clavicipitaceae, but are not yet included in phylogenetic studies. The placement of Ustilaginoideae and ergot pathogens will allow differentiation between the host habitat and host relatedness hypotheses as mechanisms of phylogenetic diversification of Clavicipitaceae.
Methods:
A multigene data set was assembled for Clavicipitaceae to test phylogenetic placement and ancestral character-state reconstructions for Ustilaginoidea virens and U. dichromonae as well as the ergot mycoparasite Cordyceps fratricida. Microscopic morphological observations of sexual and asexual states were also performed.
Key results:
Phylogenetic placement of U. virens and U. dichromonae represents a third acquisition of the plant pathogenic lifestyle in Clavicipitaceae. Cordyceps fratricida was also placed in Clavicipitaceae and recognized as a new genus Tyrannicordyceps. Ancestral character state reconstructions indicate initially infecting hemipteran insect hosts facilitates subsequent changes to a plant pathogenic lifestyle. The ancestor of T. fratricida is inferred to have jumped from grasses to pathogens of grasses.
Conclusions:
The host habitat hypothesis best explains the dynamic evolution of host affiliations seen in Clavicipitaceae and throughout Hypocreales. Co-occurrence in the same habitat has allowed for host shifts from animals to plants, and from plants to fungi.
... Morphologically reduced to a miniature, often colorless pustule, adelphoparasites are highly host dependent and occur exclusively on their sister-taxon (Goff 1982). The remaining 20% of red algal parasites are known as alloparasites (''allo'' meaning other) because whereas they also diverged from free-living species, they have since radiated to exploit more distantly related red algal hosts (Goff et al. 1997). Although this terminology has somewhat fallen out of favor because a full spectrum of host/parasite relationships occur in nature (Zuccarello et al. 2004), the terms remain useful to designate differences in the biology of the organisms. ...
Red algal parasites are unusual because the vast majority of them parasitize species with which they share a recent common ancestor. This strategy has earned them the name "adelphoparasites," from the Greek, adelpho, meaning "kin." Intracellular adelphoparasites are very rare in nature, yet have independently evolved hundreds of times among the floridiophyte red algae. Much is known about the life history and infection cycle of these parasites but nearly nothing in known about their genomes. We sequenced the mitochondrial genomes of the free-living Gracilariopsis andersonii and its closely related parasite Gracilariophila oryzoides to determine what effect a parasitic lifestyle has on the genomes of red algal parasites. Whereas the parasite genome is similar to the host in many ways, the genes encoding essential proteins ATP8 and SDHC are pseudogenes in the parasite. The mitochondrial genome of parasite from a different class of red algae, Plocamiocolax puvinata, has lost the atp8 gene entirely, indicating that this gene is no longer critical in red algal parasite mitochondria.
... These de scriptions were essentially morphological (e.g. Goff 1982; Goff & Zuccarello 1994; Zuccarello & West 1994; Broad water & Lapointe 1997; Chamberlain 1999) and it was not until the latter years of the century that the evolutionary re lationships between parasite and host and between parasites were examined using molecular tools (Goff et al. 1996Goff et al. , 1997). Apparently, autotrophic endophytes are also commonly ob served within the thalli of coralline red algae. ...
Epulo multipedes gen. et sp. nov. is described for a coralline red alga growing parasitically on Jania collected from eastern Australia. Epulo is a monospecific genus with vegetative filaments that invade host cells and totally disrupt them, a phenomenon not seen before in the Corallinaceae. The new genus comprises two phases: an unconsolidated vegetative portion that is endophytic within the host tissue, and reproductive conceptacles formed at the surface of the host. Vegetative cells are uninucleate and form haustoria within host cells. Reproductive conceptacles are formed when outgrowths of the parasite consolidate at the surface. Tetrasporangial conceptacles are multiporate, with zonate tetrasporangia. Sexual conceptacles are uniporate. Epulo is included in the tribe Austrolithoideae and has affinities with Austrolithon, but differs in being parasitic, having uninucleate rather than multinucleate cells, and having conceptacles formed externally on the host.
... Its persistence and its reactivation would imply that: (a) the process of cell division (nuclear envelope dispersion and reformation), (b) mitotic duplication (doubling of the chromosomes and allocating them to the progeny cells) and (c) the viral DNA correspond to the sexual reproductive cycle of the host organism. Such an infectious origin for the nucleus would also be compatible for the prevalence of infectious nuclei, seen in many species of parasitic red algae that represent a basal eukaryote (Goff et al., 1997). Read algae are clearly the oldest eukaryote that can be found in the fossil record. ...
In contrast with former definitions of life limited to membrane-bound cellular life forms which feed, grow, metabolise and replicate (i) a role of viruses as genetic symbionts, (ii) along with peripheral phenomena such as cryptobiosis and (iii) the horizontal nature of genetic information acquisition and processing broaden our view of the tree of life. Some researchers insist on the traditional textbook conviction of what is part of the community of life. In a recent review [Moreira, D., Lopez-Garcia, P., 2009. Ten reasons to exclude viruses from the tree of life. Nat. Rev. Microbiol. 7, 306-311.] they assemble four main arguments which should exclude viruses from the tree of life because of their inability to self-sustain and self-replicate, their polyphyly, the cellular origin of their cell-like genes and the volatility of their genomes. In this article we will show that these features are not coherent with current knowledge about viruses but that viral agents play key roles within the roots and stem of the tree of life.
... Ronquist 1994; Ward 1996; Lowe & Crozier 1997) ). These phenomena are not conned to hymenopterans: Emery's rule also applies to groups of fungi, red algae and perhaps mistletoe (Goff et al. (1997) and references therein). Three sequences of events have been suggested to lead to either strict or loose conformity with Emery's rule. ...
In some taxa of Hymenoptera, fungi, red algae and mistletoe, parasites and their hosts are either sibling species or at least closely related (Emery's rule). Three evolutionary mechanisms have been proposed for this phenomenon: (i) intraspecific parasitism is followed by sympatric speciation; (ii) allopatric speciation is followed by secondary sympatry and the subsequent parasitism of one sibling species by the other; and (iii) allopatric speciation of a species with intraspecific parasitism is followed by secondary sympatry, in which one species becomes an obligate parasite of the other. Mechanisms (i) and (ii) are problematic, while mechanism (iii) has not, to our knowledge, been analysed quantitatively. In this paper, we develop a model for single- and two-species evolutionary stable strategies (ESSs) to examine the basis for Emery's rule and to determine whether mechanism (iii) is consistent with ESS reasoning. In secondary sympatry after allopatric speciation, the system's evolution depends on the relative abundances of the two sibling species and on the proportional damage wrought by parasites of each species on non-parasitic members of the other. Depending on these interspecific effects, either the rarer or the commoner species may become the parasite and the levels of within-species parasitism need not determine which evolves to obligate parasitism.
... other Myrmica species (40), may be a result of host shifts of ''karavajevi'' ancestor, resulting in host expansion and later host specialization and speciation. This mode of radiation has been documented in various parasitic taxa, such as mistletoes (64), red algae (65), and gall wasps (66), and seems plausible also in bumblebee (35) and paper wasp inquilines (37). Alternatively, ''karavajevi'' may have increased its host array concurrently with speciation events in its original host lineage. ...
Sympatric speciation through intraspecific social parasitism has been proposed for the evolution of Hymenopteran workerless parasites. Such inquilines exploit related host taxa to produce their own sexual offspring. The relatedness of inquilines to their hosts has been generalized in Emery's rule, suggesting that social parasites are close or the closest relatives to their host species. If the closest relative of each parasite is its host, then multiple independent origins of the parasite species are implied even within a single genus, probably through sympatric speciation. To test the plausibility of sympatric speciation in inquilines, we conducted a mitochondrial DNA phylogenetic analysis in three inquiline-host pairs of Myrmica ant species. We show that congeneric inquilines have originated independently several times. We also show that two of the inqulines are more closely related to their hosts than to any other species. Our results suggest sympatric speciation of Myrmica inquilines. Sympatric speciation is probably facilitated by the social biology and ecology of Myrmica, with polygyny as a prerequisite for the evolution of intraspecific parasitism.
... Polyphyletic origins of parasitism and sister relationships between hosts and parasites as predicted by a strict interpretation of Emery's hypothesis were found in red algae (Goff et al., 1997), whereas a monophyletic origin of parasitism and subsequent colonization of closely related hosts is a more common result (Choudhary et al., 1994; Ronquist, 1994; Pedersen, 1996; Parker and Rissing, 2002). In all of the above examples, however, parasitic taxa fall within the host clade, suggesting their derivation from one of the current host lineages. ...
The African brood parasitic finches (Vidua spp.) are host specialists that mimic the songs and nestling mouth markings of their finch hosts (family Estrildidae). Although recent molecular analyses suggest rapid speciation associated with host switches in some members of this group, the association of different Vidua lineages with particular host genera suggests the possibility of cospeciation at higher levels in the host and parasite phylogenies. We compared a phylogeny of all Vidua species with a phylogeny of their estrildid finch hosts and compared divergence time estimates for the two groups. Basal divergences among extant members of the Vidulidae and among Vidua species are more recent than those among host genera and species, respectively, allowing a model of cospeciation to be rejected at most or all levels of the Vidua phylogeny. Nonetheless, some tests for cospeciation indicated significant congruence between host and parasite tree topologies. This result may be an artifact of clade-limited colonization. Host switches in parasitic finches have most often involved new hosts in the same or a closely related genus, an effect that increases the apparent congruence of host and parasites trees.
... To our knowledge, no formal theory has been developed to address this relationship directly, but one idea in the literature suggests that it may be worth testing. Emery's rule (Emery 1909;Wilson 1971) is the observation that species often effectively parasitize other closely related species, especially among social insects, although the rule has also been suggested to extend to diverse groups of organisms such as fungi, red algae, and mistletoe (e.g., Goff et al. 1997). One suggested mechanism for Emery's rule is that parasites can pass more easily through the defenses of a sibling species than through those of less closely related species (Lowe et al. 2002). ...
Adaptive divergence among populations can result in local adaptation, whereby genotypes in native environments exhibit greater fitness than genotypes in novel environments. A body of theory has developed that predicts how different species traits, such as rates of gene flow and generation times, influence local adaptation in coevolutionary species interactions. We used a meta-analysis of local-adaptation studies across a broad range of host-parasite interactions to evaluate predictions about the effect of species traits on local adaptation. We also evaluated how experimental design influences the outcome of local adaptation experiments. In reciprocally designed experiments, the relative gene flow rate of hosts versus parasites was the strongest predictor of local adaptation, with significant parasite local adaptation only in the studies in which parasites had greater gene flow rates than their hosts. When nonreciprocal studies were included in analyses, species traits did not explain significant variation in local adaptation, although the overall level of local adaptation observed was lower in the nonreciprocal than in the reciprocal studies. This formal meta-analysis across a diversity of host-parasite systems lends insight into the role of both biology (species traits) and biologists (experimental design) in detecting local adaptation in coevolving species interactions.
The dominant social-evolutionary paradigm implicitly equates social actions and behaviors causing associations by extrapolating from models of social actions to explain behaviors affecting association. This extrapolation occurs when models of helping behavior are applied to explain aggregation or fusion, and when models of discriminatory helping behavior are applied to explain discriminatory segregation or discriminatory rejection. Here, I outline an alternative theoretical approach that explicitly distinguishes a social action as a helping or harming behavior, and an association as the context for a social action. Based on this distinction, I define a list of terms that allows a classification of association phenomena and the conceptual framework necessary to explain their evolution. I apply the resulting theory, which I call “association theory,” to identify a series of steps common to major and minor transitions in social evolution. These steps include the evolution of association, the evolution of differential treatment, the evolution of association preference, and the evolution of genetic kin recognition. I explain how to measure the parameters of association theory and I apply the theory to test Hamilton’s rule. I evaluate the evidence for association theory, including how it resolves anomalies of a former paradigm. Finally, I discuss association theory’s assumptions, and I explain why it may become the dominant framework for analyzing social evolution.
The dominant social-evolutionary paradigm implicitly equates social actions and behaviors causing associations by extrapolating from models of social actions to explain behaviors affecting association. This extrapolation occurs when models of helping behavior are applied to explain aggregation or fusion, and when models of discriminatory helping behavior are applied to explain discriminatory segregation or discriminatory rejection. Here, I outline an alternative theoretical approach that explicitly distinguishes a social action as a helping or harming behavior, and an association as the context for a social action. Based on this distinction, I define a list of terms that allows a classification of association phenomena and the conceptual framework necessary to explain their evolution. I apply the resulting theory, which I call “association theory,” to identify a series of steps common to major and minor transitions in social evolution. These steps include the evolution of association, the evolution of differential treatment, the evolution of association preference, and the evolution of genetic kin recognition. I explain how to measure the parameters of association theory and I apply the theory to test Hamilton’s rule. I evaluate the evidence for association theory, including how it resolves anomalies of a former paradigm. Finally, I discuss association theory’s assumptions, and I explain why it may become the dominant framework for analyzing social evolution.
By impacting the structure of the seaweed host population, epiphytes, endophytes, and parasites may affect the species community with which the host interacts. These intimate associations have been hardly studied beyond a descriptive stage. The scarcity of epidemiological studies in natural populations of seaweeds is a major gap for the understanding of naturally occurring mechanisms impacting ecosystem functioning. However, major progresses have been done in recent years in characterizing some mechanisms of cross-talk involved in host specificity, the role of bacterial biofilms in mediating some interactions, as well as host defenses that impact the diversity of these associations through allelopathic interactions. Close associations are also providing both an economic burden and new opportunities in human affairs, as seaweed aquaculture develops worldwide and in the context of environment-friendly strategies to cope with fouling organisms, respectively.
The subfamily Bostrychioideae (Rhodomelaceae, Ceramiales) presently consists of two genera and about 17 species. Generic distinction within the subfamily is based on the number of tier cells (the results of transversely dividing pericentral cells) per axial cell, with two tier cells designating the genus Bostrychia and more than two characterising Stictosiphonia. Phylogenetic analysis of all but two species of this subfamily based on DNA sequences from the nuclear-encoded 26S ribosomal RNA gene and plastid-encoded rbcL gene shows that this generic split is not supported. Our data suggest that the subfamily may be split into two sections based on one or another type of attachment structure, as first proposed by Erika Post, but we propose that all species be returned to the genus Bostrychia due to as yet not fully resolved or supported phylogeny. We also recommend that Bostrychia tenella ssp. flagellifera be returned to B. flagellifera because it does not group with B. tenella samples and shows a diagnostic synapomorphy (branching interval). Our data additionally show that many currently circumscribed species are not monophyletic. Even when B. tenuissima is regarded as synonymous with B. simpliciuscula, due to sequence identity, the resulting amalgamated species is still polyphyletic when populations from broad geographic regions are analysed. Another possible polyphyletic species is B. calliptera. The clade containing cladohaptera (specialized attachment organs) is taxonomically unresolved but contains a heavily corticated species (B. pilulifera), a parasite (Bostrychiocolax australis), plus several lineages in the Bostrychia radicans/B. moritziana species complex that are morphologically very similar.
The morphology of the parasitic red alga Janczewskia moriformis Setchell is described based on material from Espirito Santo, southeastern Brazil. The parasite was growing on two species of Laurencia, L. flagellifera J. Agardh and L. translucida M.T Fujii et Cordeiro-Marino. Janczewskia moriformis has a wart-like thallus made up of coalescent branches that form a solid tissue from which branches develop and project beyond the surface of the wart. Lenticular thickenings are absent from the medullary cell walls, and secondary pit connections are not present between adjacent cortical cells. Spermatangial conceptacles are narrow mouthed and the spermatangial branches lie on the base and side of the conceptacles. In all these features, the Brazilian plants are similar to J. moriformis of the Pacific coast of North America, except for the different hosts and the presence of projecting cortical cells in our plants. Although the parasite has the ability to grow on both Laurencia hosts, it is found more frequently on L. flagellifera and is morphologically more similar to it.
Coralline-coralline and coralline-other plant (including higher plants, algae, fungi and prokaryotes) interactions are reviewed in terms of competition, parasitism, commensalism, amensalism, neutralism, protocooperation and mutualism. Two of the seven interactions appear unreported (neutralism and protocooperation), four (commensalism, competition, parasitism and amensalism) are recorded to varying degrees, and one is uncertain (mutualism). Within competition and parasitism, most known interactions are coralline-coralline, whereas amensal and commensal interactions were dominated by coralline-other plant interactions. Examining coralline-coralline and coralline-other plant interactions shows that we know very little, particularly about coralline interactions involving algal hosts.
A molecular phylogenetic study of red algal parasites commonly found in the Northwestern Pacific and the Hawaiian Islands was undertaken. Four species, Benzaitenia yenoshimensis Yendo, Janczewskia hawaiiana Apt, J. morimotoi Tokida, and Ululania stellata Apt et Schlech (Ceramiales), are parasitic on rhodomelacean species belonging to the tribes Chondrieae and Laurencieae. Although Janczewskia and Ululania are classified in the same tribes as their host species, the taxonomic placement of Benzaitenia has been controversial. To infer the phylogenetic positions of these parasites and to clarify the relationships between the parasites and their hosts, phylogenetic analyses of partial nuclear SSU and LSU rRNA genes and the cox1 gene were performed. The SSU rRNA gene analyses clearly show that both Janczewskia species are positioned within the Laurencia s. str. clade with their host species, while Benzaitenia and Ululania are placed in the Chondrieae clade. According to these analyses, J. hawaiiana and U. stellata are not sister to their current hosts; in contrast, B. yenoshimensis and J. morimotoi are closely related to their current hosts. These data suggest that J. hawaiiana and U. stellata have likely evolved from species other than their current hosts and have switched hosts at some point in their evolutionary history. Likelihood ratio tests do not support the monophyly of J. hawaiiana and J. morimotoi, suggesting multiple origins of parasitism within Laurencia s. str.
Pelagophycus porra (Leman) Setchell has a narrow distribution confined to deep water from the Channel Islands off the southern California coast to central Baja California, Mexico. Distinct morphotypes are consistently correlated with distinctive habitats, that is, windward exposures characterized by strong water motion and rocky substrates, and sheltered areas with soft substrates found on the lee sides of the islands. We tested the hypothesis that morphologically and ecologically distinct forms reflect genetically distinct stands. Individuals representing populations from three islands and the mainland were compared using RFLP analyses of the nuclear rDNA internal transcribed spacers (ITS1 and ITS2), chloroplast trnL (UAA) intron sequences, and random amplified polymorphic DNA (RAPDs). No variation was found in a survey of 20 restriction sites of ITS1 (ca. 320 base pair [bp]) and ITS2 (ca. 360 bp) among individuals from six populations. Likewise, comparisons of trnL intron (241 bp) sequences among nine individuals from seven populations were identical with the exception of a CATAGT insert in two adjacent stands. A RAPD analysis of 24 individuals from nine populations (4 windward and 5 leeward) using 16 primers generated 166 bands. Thirty-eight percent of the bands did not vary, 16% were unique to a given individual, and 46% were variable. Neighbor joining analysis produced a well-resolved tree with moderately high bootstrap support in which windward and leeward populations were easily distinguished. The lack of divergence in both the fast evolving nuclear rDNA-ITS and the chloroplast trnL intron does not support the morphotypes as different species. However, the compartmentalized differentiation shown in the RAPD data clearly points to isolation. This, and previous ecological studies that demonstrate habitat specificity suggest that leeward stands probably comprise a species in statu nascendi.
DNA sequences, powerful for phylogeny, have not yet proven as rewarding for taxonomic categorization purposes. However, further analyses of one locus, the second Internal Transcribed Spacer of the nuclear ribosomal gene cistron, has suggested a high degree of predictability across eukaryotes. Comparison of the secondary structure of ITS2 transcripts reveals its most conserved region, on the 5′-side of helix III. Comparison of this 5′ 30 bp highly conserved region with the extent of sexual compatibility in a clade of organisms produces two useful predictions: identity of this region predicts meaningful intercrossing ability, and, difference of even one CBC pairing in this region predicts total failure of crossing. Previous to the appearance of the first CBC in the highly conserved portion, all gametic compatibility has been lost, thanks to the parallel evolutionary changes in genes controlling mating. These two landmark events help to delimit the level of interbreeding taxa.
proportion of the biodiversity of life. Not only do they impact humans and other animals in fundamental ways, but in recent years they have become a powerful model system for the study of ecology and evolution, with practical applications in disease prevention. Here, in a thoroughly revised and updated edition of his influential earlier work, Robert Poulin provides an evolutionary ecologist's view of the biology of parasites. He sets forth a comprehensive synthesis of parasite evolutionary ecology, integrating information across scales from the features of individual parasites to the dynamics of parasite populations and the structuring of parasite communities.Evolutionary Ecology of Parasitespresents an evolutionary framework for the study of parasite biology, combining theory with empirical examples for a broader understanding of why parasites are as they are and do what they do. An up-to-date synthesis of the field, the book is an ideal teaching tool for advanced courses on the subject. Pointing toward promising directions and setting a research agenda, it will also be an invaluable reference for researchers who seek to extend our knowledge of parasite ecology and evolution.
A maximum likelihood method for inferring evolutionary trees from DNA sequence data was developed by Felsenstein (1981). In evaluating the extent to which the maximum likelihood tree is a significantly better representation of the true tree, it is important to estimate the variance of the difference between log likelihood of different tree topologies. Bootstrap resampling can be used for this purpose (Hasegawa et al. 1988; Hasegawa and Kishino 1989), but it imposes a great computation burden. To overcome this difficulty, we developed a new method for estimating the variance by expressing it explicitly.The method was applied to DNA sequence data from primates in order to evaluate the maximum likelihood branching order among Hominoidea. It was shown that, although the orangutan is convincingly placed as an outgroup of a human and African apes clade, the branching order among human, chimpanzee, and gorilla cannot be determined confidently from the DNA sequence data presently available when the evolutionary rate constancy is not assumed.
A mat-forming, stoloniferous, marine red alga previously included within the Gelidium pusillum is common in the lower and mid eulittoral zones on the coasts of South Australia, Victoria, S New South Wales, and the North, South and Chatham Islands of New Zealand. This species has diphasic life history in which there is an alternation of gametangial and tetrasporangial phases. -from Authors
In the initial stages of cell–cell interactions (spore germination and host penetration), the adelphoparasites Gardneriella tuberifera Kyl. and Gracilariophila oryzoides Setch. & Wilson form infection rhizoids that fuse directly with underlying host epidermal or cortical cells. In so doing, parasite nuclei and other organelles enter the cytoplasm of the host. The resulting heterokaryon may fuse with adjacent host cells either directly, via secondary pit connections, or by the dissolution or dislodgment of pit plugs from existing pit connections. The cell fusion events result in a heterokaryotic syncytium in which parasite nuclei replicate. In Gardneriella, formation of the syncytium induces surrounding host tissues to divide to form a photosynthetic callus. The internalized syncytium forms conjunctor and rhizoidal cells that fuse with host callus, eventually transforming the host callus into cells containing parasite nuclei. Gracilariophila does not induce surrounding host tissue to divide. Rather, division of the initial heterokaryotic tissue gives rise to the colorless mantle that protrudes from the host and forms reproductive structures. The heterokaryotic tissue also fuses with underlying host cells, thereby spreading parasite nuclei throughout adjacent host cells. In both these adelphoparasites, transformation of host cells by parasite nuclear invasion results in plastid dedifferentiation, an increase in mitochondria, autolysis of organelles, and accumulation of large amounts of floridean starch. The development and physiology of these parasites is similar to normal post-fertilization processes in the hosts that give rise to carposporophytes and suggests that these adelphoparasites may have originated from perturbations of developmental pathways involved in their host's post-fertilization development.
In several groups of parasites including insect, flowering plant, fungal, and red algal parasites, morphological similarities of the parasites and their specific hosts have led to hypotheses that these parasites evolved from their hosts. But these conclusions have been criticized because the morphological features shared by parasite and host may be the result of convergent evolution. In this study, we examine the hypothesis, originally put forth by Setchell, that adelphoparasitic red algae, that is, parasitic red algae that are morphologically very similar to their hosts, evolved from their specific red algal hosts. Rather than comparing morphological features of parasites and hosts, small-subunit 18S nuclear ribosomal DNA and the internal transcribed spacer regions (ITSs) of the nuclear ribosomal repeat are compared for five parasites, their hosts, and related nonhosts from four red algal orders. These comparisons reveal that each of these adelphoparasites has evolved either directly from the host on which it is currently found, or it evolved from some other taxon that is closely related to the modern host. The parasites Gardneriella tuberifera, Rhodymeniocolax botryoides, and probably Gracilariophila oryzoides evolved from their respective hosts Sarcodiotheca gaudichaudii, Rhodymenia pacifica, and Gracilariopsis lemaneiformis, respectively. The parasite Faucheocolax attenuata evolved from either Fauchea laciniata or Fauchea fryeana and subsequently radiated onto the other host species. Presently this parasite is found on both hosts. Lastly, some parasitic genera such as Plocamiocolax are polyphyletic in their origins. A species of Plocamiocolax from an Antarctic Plocamium cartilagineum appears to have evolved from its host whereas the common Plocamiocolax pulvinata that occurs along the west coast of North America likely evolved from Plocamium violaceum and radiated secondarily onto its present day host, Plocamium cartilagineum.
Delineation of species in the economically important agarophyte genera Gracilaria and Gracilariopsis has proven extremely difficult using available morphological characteristics. In this study, we examine the usefulness of two transcribed spacers for molecular systematic studies of these genera. The polymerase chain reaction was used to amplify the internal transcribed spacers (ITSs) and the intervening 5.8S ribosomal DNA of the nuclear ribosomal repeat region. In addition, a plastid spacer region and flanking regions of coding genes were amplified from the RUBISCO operon. Both regions were sequenced for individuals and populations of Gracilariopsis lemaneiformis (Bory) Dawson, Acleto, et Foldvik to determine the usefulness of these spacers in delimiting populations. These studies reveal that there is as much variation among individuals of a population as there is between individuals of geographically separate populations. In addition, the ITS spacer regions were compared between different species of Gracilariopsis and Gracilaria. The nuclear ITS spacer region is conserved at a species level in both genera and provides phylogenetically informative characters that can be used to examine species interrelationships among relatively closely related taxa. However, because of the difficulties of aligning this entire region among species from the two genera, the ITS region is not useful for examining intergenera relationships. ITS interspecies sequence comparisons indicate that Gracilariopsis lemaneiformis from California is significantly different from G. lemaneiformis from China and that a species of Gracilariopsis from Peru is more closely related to G. lemaneiformis from North Carolina than it is to the other Gracilariopsis species examined. In addition, these studies indicate that Gracilaria chilensis Bird, McLachlan, et Oliveira from New Zealand and Gracilaria tenuistipitata Chang et Xia from southeast Asia are as closely related as are Gracilaria verrucosa (Hudson) Papenfuss, G. pacifica Abbott, and Gracilaria robusta Kylin. Phylogenetic analysis of aligned plastid spacer sequences from Gracilaria and Gracilariopsis taxa provide similar conclusions about species relationships.
Pleuroblepharis stichidophora gen. et sp. nov., from Amchitka Island in the Aleutian Island s, is described as new to science. This taxon is the only representative of the Bonnemaisoniaceae (Nemaliales, Rhodophyta) collected at Amchitka. It is distinguished from other members of the family by the presence of macroscopic tetrasporophytes with compound tetrasporangial stichidia arising along the margins of laminate axes. These tetrasporic branchlets are homologous to indeterminate branches. Gland cells with brownish contents are present over the surface of the laminate axes and also on the stichidia . Although numerous specimens have been collected, tetrasporic plants are the only fertile stages observed so far.
The CLUSTAL package of multiple sequence alignment programs has been completely rewritten and many new features added. The new software is a single program called CLUSTAL V, which is written in C and can be used on any machine with a standard C compiler. The main new features are the ability to store and reuse old alignments and the ability to calculate phylogenetic trees after alignment. The program is simple to use, completely menu driven and on-line help is provided.
The phylogenetic diversity of the eukaryotic kingdom was assessed by comparing the structural and evolutionary diversity of 18-20S ribosomal RNA genes. The coding regions for cytoplasmic small subunit ribosomal RNA genes vary in length from 1753 to 2305 nucleotides, and they appear to be evolutionary mosaics in which highly and partially conserved sequences are interspersed among regions that display very high rates of genetic drift. Structural similarities between these gene sequences were used to establish a phylogenetic framework for the eukaryotes. The extent of sequence variation within the eukaryotes exceeds that displayed within the eubacterial or archaebacterial lines of descent. The kinetoplastids and euglenoids represent the earliest branchings among the eukaryotes. These branchings preceded the divergence of lineages leading to the slime molds and apicomplexans and far antedate a radiative period that gave rise to the plants, animals, fungi, and other protists.
Phylogenetic relationships among the major groups of hymenopteran insects were investigated by using comparative sequence information from the mitochondrial 16S rRNA gene. The placement of the ectoparasitic Stephanidae as the sister group to the remaining Apocrita confirmed ectoparasitism as the ground plan biology for the Apocrita. Endoparasitism evolved at least eight times within the Apocrita, and the consequent association with polydnaviruses and virus-like particles evolved at least three times. The Evaniomorpha were consistently placed as basal to the remaining Apocrita but were not resolved as monophyletic. The Gasteruptiidae were resolved as the sister group to the Evaniidae, but the relationship between the Trigonalyoidea and the Evanioidea was unclear. The Proctotrupomorpha (sensu Rasnitsyn) was resolved by topology-dependent permutation tail probability (T-PTP) testing as monophyletic, with strong evidence for a sister group relationship between the Platygastroidea and the Chalcidoidea. Strong evidence was found for the monophyly of the Ichneumonomorpha (Ichneumonidae + Braconidae) and the sister-group relationship between the Aculeata (Vespomorpha) and the Ichneumonomorpha.
A phylogeny for the Rhodophyta has been inferred by parsimony analysis of plastid rbcL sequences representing 81 species, 68 genera, 38 families, and 17 orders of red algae; rbcL encodes the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. Levels of sequence divergence among species, genera, and families are high in red algae, typically much greater than those reported for flowering plants. The Rhodophyta traditionally consists of one class, Rhodophyceae, and two subclasses, Bangiophycidae and Florideophycidae. The Bangiophycidae with three orders (Porphyridiales, Compsopogonales, and Bangiales) appears to be polyphyletic, and the Florideophycidae with 17 orders is monophyletic in this study. The current classification of the Florideophycidae based on ultrastructure of pit connections is supported. With the exception of the Rhodogorgonales, which appears to be misplaced, orders with one or two pit-plug cap layers (Hildenbrandiales, Corallinales, Acrochaetiales, Palmanales, Batrachospermales, and Nemaliales) terminate long branches of basal position within Florideophycidae in the most parsimonious rbcL tree. Orders that lack typical cap layers but possess a cap membrane are resolved as a monophyletic clade sister to the Ahnfeltiales. The large order Gigartinales, which is distributed among five rbcL clades, is polyphyletic. Families that possess typical carrageenan in their cell walls are resolved as a terminal clade containing two family complexes centered around the Solieriaceae and Gigartinaceae.
During the normal course of infection, nuclei are transferred via secondary pit connections from the parasitic marine red alga Choreocolax to its red algal host Polysiphonia. These "planetic" nuclei are transmitted by being cut off into specialized cells (conjunctor cells) that fuse with an adjacent host cell, thereby delivering parasite nuclei and other cytoplasmic organelles into host cell cytoplasm. Within the foreign cytoplasm, planetic nuclei survive for several weeks and may be active in directing the host cellular responses to infection, since these responses are seen only in host cells containing planetic nuclei. The transfer and long-term survival of a nucleus from one genus into the cytoplasm of another through mechanisms that have evolved in nature challenge our understanding of nuclear-cytoplasmic interactions and our concept of "individual."
Some new and unreported sublittoral algae from Cerros Island
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Intorno all'origine delle formiche dulotiche, par-assitiche e mirmecofile
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Parasitic red algae: an appraisal. Pp. 87-109 in Modern approaches to the taxonomy of red and brown algae
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Un nouveau genre de Rhodophycee parasite d'une Delesseriacee
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Recherches sur les formes parasites. Comptes Rendus Hebdomadaires des Sceances de l'Academie des Sci-ences
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Parasitism among the red algae
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Choreocolax polysiphoniae Reinsch
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Phylogenetic analysis using parsimony (PAUP). Vers. 3.01. Illinois Natural History Survey
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The parasitic Aculeata, a study in evolution
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Epiparasitism in mistletoes
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