Hypomethylation of the aquatic invasive plant,Ludwigia grandiflora subsp. hexapetala mimics the adaptive transition into the terrestrial morphotype

Ongoing global changes affect ecosystems and open up new opportunities for biological invasion. The ability of invasive species to rapidly adapt to new environments represents a relevant model for studying short-term adaptation mechanisms. The aquatic invasive plant, Ludwigia grandiflora subsp. hexapetala, is classified as harmful in European rivers. In French wet meadows, this species has shown a rapid transition from aquatic to terrestrial environments with emergence of two distinct morphotypes in 5 years. To understand the heritable mechanisms involved in adjustment to such a new environment, we investigate both genetic and epigenetic as possible sources of flexibility involved in this fast terrestrial transition. We found a low overall genetic differentiation between the two morphotypes arguing against the possibility that terrestrial morphotype emerged from a new adaptive genetic capacity. Artificial hypomethylation was induced on both morphotypes to assess the epigenetic hypothesis. We analyzed global DNA methylation, morphological changes, phytohormones and metabolite profiles of both morphotype responses in both aquatic and terrestrial conditions in shoot and root tissues. Hypomethylation significantly affected morphological variables, phytohormone levels and the amount of some metabolites. The effects of hypomethylation depended on morphotypes, conditions and plant tissues, which highlighted differences among the morphotypes and their plasticity. Using a correlative integrative approach, we showed that hypomethylation of the aquatic morphotype mimicked the characteristics of the terrestrial morphotype. Our data suggest that DNA methylation rather than a new adaptive genetic capacity is playing a key role in L. grandiflora subsp. hexapetala plasticity during its rapid aquatic to terrestrial transition.     

Taxonomy, diversity and origins of symbiotic endophytes of Achnatherum sibiricum in the Inner Mongolia Steppe of China

We sampled five Achnatherum sibiricum populations and documented the distribution and abundance of endophytes. In total, 438 fungal isolates were obtained. They were classified into 11 morphotypes based on growth rate and morphological characters including colonial morphology, the production of conidiogenous cells, conidial size and dimension on potato dextrose agar medium. Both tub2 and actG sequences identified only a single product in all representative isolates from three dominant morphotypes. All sequences fell in the same main clade, including Neotyphodium gansuense and Neotyphodium gansuense var. inebrians from another Achnatherum species in North China, Achnatherum inebrians , and Neotyphodium guerinii from European grasses Melica ciliate and Melica transsilvanica . Based on both morphological and phylogenetic analyses, isolates in morphotype I were described as representing a novel Neotyphodium species, Neotyphodium sibiricum sp. nov. Isolates in both morphotype II and III were identified as representing N. gansuense . Both tub2 and actG sequences suggested that N. sibiricum and N. guerinii were probably derived from a common Epichloë ancestor.     

Difference in antifungal activity of morphotypes of clavicipitaceous endophytes within and between species

In a previous study, a total of 484 endophytic fungi were isolated and purified from seven populations of Achnatherum sibiricum (L.) Keng collected at six geographical locations in Inner Mongolia, China. Based on growth rates as well as morphological characteristics, the isolates were classified into five morphotypes. Among them, morphotypes A, B and C were ascribed to the same species, Neotyphodium chisosum, based on ITS sequences. Morphotype E was identified as Epichloë amarillans. In the present study, four morphotypes, A, B, C and E, belonging to two species, were chosen for an in vitro pathogen trial. The results showed that both endophyte colonies and endophyte filtrate of all morphotypes could inhibit the mycelia growth and spore germination of the pathogen fungi tested. The magnitude of inhibition varied not only between species, but also among morphotypes of the same species. Overall, the antifungal ability of E. amarillans (morphotype E) was higher than that of N. chisosum. Within N. chisosum, the antifungal ability was highest in morphotype C, followed by morphotype A, and lowest in morphotype B. This variability suggests that different morphotypes might represent different genotypes of endophyte. The effect of endophyte infection on the host grass should be examined not only on the species level but also on the morphotype level to determine the possible interactions.     

Come with me if you want to live: sympatric parasites follow different transmission routes through aquatic host communities

Community composition, including the relative density of each host species, plays a vital role in the transmission of parasites or disease in freshwater ecosystems. Whereas some host species can effectively transmit parasites, others can act as dead ends (non-viable transmission routes), accumulating large numbers of parasites throughout their life, thus becoming important sinks for parasite populations. Although population sinks have been identified in certain host-parasite systems, robust field estimates of the proportions of parasites that are lost to these hosts are lacking. Here, we quantified the distribution of encysted larval hairworms (phylum Nematomorpha), common parasites in lotic ecosystems, in two subalpine stream communities of New Zealand. With parasite and host population densities calculated per m², we identified which host species most likely contributed to the transmission of three sympatric hairworm morphotypes identified in both streams, and which species acted as population sinks. We also tested for seasonal patterns and peaks in the abundance of each morphotype in the two communities over the sampling season. Finally, we tested whether hosts emerging from the streams had comparable abundances of hairworm morphotypes throughout the sampling period. For each morphotype, different key sets of host species harboured more hairworms on average (abundance) than others, depending on the stream. For one morphotype in particular, two species of hosts were found to be important population sinks that inhibited over a third of these parasites from completing their life cycle. We also observed a clear peak in abundance for another hairworm morphotype during summer. Our data suggest that hosts emerging from the streams matched their aquatic counterparts with respect to hairworm abundance, indicating no infection-dependent reduction in emergence success. Our findings suggest that, depending on relative community composition, sympatric parasites follow different host transmission pathways, some of which lead to dead ends that potentially impact overall infection dynamics. In turn, this information can help us understand the spread or emergence of disease in both freshwater and terrestrial environments, since hairworms infect terrestrial arthropods to complete their life cycle.     

Isolation and characterization of eight microsatellite loci in two morphotypes of the Southeast Asian army ant,Aenictus laeviceps

Eight polymorphic microsatellite markers were developed from morphotype L1 of the Southeast Asian army ant, Aenictus laeviceps in Borneo, and characterized for morphotypes L1 and L2. The number of alleles per locus ranged from nine to 24 (average 15) in morphotype L1 and two to 16 (average 9.8) in L2. Observed heterozygosity ranged from 0.75 to 0.96 in morphotype L1 and from 0.08 to 0.96 in L2. All loci were in Hardy–Weinberg equilibrium. One pair of loci showed linkage disequilibrium in morphotype L1. All markers successfully amplified in morphotype S, and some markers amplified in other Aenictus species.     

Difference in antifungal activity of morphotypes of clavicipitaceous endophytes within and between species

In a previous study, a total of 484 endophytic fungi were isolated and purified from seven populations of Achnatherum sibiricum (L.) Keng collected at six geographical locations in Inner Mongolia, China. Based on growth rates as well as morphological characteristics, the isolates were classified into five morphotypes. Among them, morphotypes A, B and C were ascribed to the same species, Neotyphodium chisosum, based on ITS sequences. Morphotype E was identified as Epichlo? amarillans. In the present study, four morphotypes, A, B, C and E, belonging to two species, were chosen for an in vitro pathogen trial. The results showed that both endophyte colonies and endophyte filtrate of all morphotypes could inhibit the mycelia growth and spore germination of the pathogen fungi tested. The magnitude of inhibition varied not only between species, but also among morphotypes of the same species. Overall, the antifungal ability of E. amarillans (morphotype E) was higher than that of N. chisosum. Within N. chisosum, the antifungal ability was highest in morphotype C, followed by morphotype A, and lowest in morphotype B. This variability suggests that different morphotypes might represent different genotypes of endophyte. The effect of endophyte infection on the host grass should be examined not only on the species level but also on the morphotype level to determine the possible interactions.     

Congruence between morphological and molecular markers inferred from the analysis of the intra-morphotype genetic diversity and the spatial structure of Oxalis tuberosa Mol.

Oxalis tuberosa is an important crop cultivated in the highest Andean zones. A germplasm collection is maintained ex situ by CIP, which has developed a morphological markers system to classify the accessions into morphotypes, i.e. groups of morphologically identical accessions. However, their genetic uniformity is currently unknown. The ISSR technique was used in two experiments to determine the relationships between both morphological and molecular markers systems. The intra-morphotype genetic diversity, the spatial structures of the diversity and the congruence between both markers systems were determined. In the first experience, 44 accessions representing five morphotypes, clearly distinct from each other, were analyzed. At the molecular level, the accessions exactly clustered according to their morphotypes. However, a genetic variability was observed inside each morphotype. In the second experiment, 34 accessions gradually differing from each other on morphological base were analyzed. The morphological clustering showed no geographical structure. On the opposite, the molecular analysis showed that the genetic structure was slightly related to the collection site. The correlation between both markers systems was weak but significant. The lack of perfect congruence between morphological and molecular data suggests that the morphological system may be useful for the morphotypes management but is not appropriate to study the genetic structure of the oca. The spatial structure of the genetic diversity can be related to the evolution of the species and the discordance between the morphological and molecular structures may result from similar selection pressures at different places leading to similar forms with a different genetic background.     

Effects of ecotypes and morphotypes in feedstock composition of switchgrass (Panicum virgatum L.)

Switchgrass (Panicum virgatum L.) is a C4 grass with high biomass yield potential and is now a model species for the Bioenergy Feedstock Development Program. Two distinct ecotypes (e.g., upland and lowland) and a range of plant morphotypes (e.g., leafy and stemmy) have been observed in switchgrass. The objective of this study was to determine the influence of ecotype and morphotype on biomass feedstock quality. Leaf and stem tissues of leafy and stemmy morphotypes from both lowland and upland ecotypes were analyzed for key feedstock traits. The leaf : stem ratio of leafy morphotype was more than 40% higher than the stemmy morphotype in both upland and lowland ecotypes. Therefore, the stemmy morphotype has significant advantages over leafy morphotype during harvesting, storage, transportation and finally the feedstock quality. Remarkable differences in feedstock quality and mineral composition were observed in switchgrass genotypes with distinct ecotypic origins and variable plant morphotypes. Lignin, hemicelluloses and cellulose concentrations were higher in stems than in the leaves, while ash content was notably high in leaves. A higher concentration of potassium was found in the stems compared to the leaves. In contrast, calcium was higher and magnesium was generally higher in the leaves compared to stems. The upland genotypes demonstrated considerably higher lignin (14.4%) compared with lowland genotypes (12.4%), while hemicellulose was higher in lowland compared with upland. The stemmy type demonstrated slightly higher lignin compared with leafy types (P < 0.1). Differences between the ecotypes and morphotypes for key quality traits demonstrated the potential for improving feedstock composition of switchgrass through selection in breeding programs.     

Genetic and anatomic relationships among three morphotypes of the echinoid Echinocrepis rostrata

Abstract. Three morphotypes—purple, tan, and white—of an irregular echinoid of the genus Echinocrepis are commonly observed in the deep North Pacific Ocean. Mitochondrial (mt) 16S DNA and cytochrome c oxidase subunit I (COI) DNA sequences were amplified from gonadal tissue samples from specimens of each morphotype. These portions of the mitochondrial genome are commonly used in species barcoding, and their similarities were compared and placed in 95% connection limit parsimony networks. All three morphotypes have similar 16S mtDNA and COI mtDNA sequences, and are thus likely representatives of the same species, Echinocrepis rostrata. Specimens of the white morphotype were smaller than the specimens of the other two morphotypes, had less gonad tissue, and had a different body shape, suggesting that it represents the juvenile form of E. rostrata. Resolving the three morphotypes into one species simplifies the identification of E. rostrata from photographs and leads to a greater understanding of the life history and reproductive cycle of a species vital to deep-sea bioturbation and carbon sequestration.     

Genetic divergence between and within two color morphotypes of <Emphasis Type="Italic">Parapercis sexfasciata</Emphasis> (Perciformes: Pinguipedidae) from Tosa Bay,southern Japan

The anterior half of the mitochondrial DNA control region (mtCR) sequence (ca. 400 base pairs) was compared between two color morphotypes (A, B) of Parapercis sexfasciata from Tosa Bay, southern Japan, using 16 and 21 specimens, respectively. Intramorphotypic mtCR divergences were only 0.0–0.5% and 1.0–2.5% for morphotypes A and B, respectively. In contrast, intermorphotypic mtCR divergence was much greater, 12.7–14.0%. Furthermore, phylogenetic analysis using a neighbor-joining algorithm, with P. multifasciata as an outgroup, showed that each morphotype was reciprocally monophyletic. These results and the distinct coloration and overlapping distribution indicate that the two color morphotypes of P. sexfasciata represent two distinct species. Mismatch distribution analysis suggested that both morphotypes had undergone population expansion; however, estimates of initial population sizes and mutational timescales suggested that morphotype B comprises historically larger and older populations than morphotype A.     

Chromosome study of hybrid and gynogenetic offspring of artificial crosses between members of the catfish families Clariidae and Pangasiidae

Synopsis Artificial hybridization between species of the catfish families Clariidae (Clarias macrocephalus) and Pangasiidae (Pangasius sutchi) resulted in first generation offspring comprising two intermediate morphotypes and one morphotype indistinguishable from its clariid parent. The two intermediate morphotypes apparently correspond to hybrid morphotypes 2 and 4 resulting from earlier hybridization experiments between the same parent species (Tarnchalanukit 1986). We did not obtain morphotypes 1 and 3. Chromosome spreads of the relatively pangasiid-like morphotype 2 reveal a diploid number of 57, presumably comprising one set of Clarias (n=27) and one of Pangasius (n=30) chromosomes. The relatively clariid-like morphotype 4 is a triploid with 84 chromosomes, presumably comprising two sets from Clarias (2n=54) and one from Pangasius (n=30). Finally, the morphotype indistinguishable from Clarias, is a diploid with 54 chromosomes, apparently arising from gynogenesis.     

Leaf morphological responses to variation in water availability for plants in the <Emphasis Type="Italic">Piriqueta caroliniana</Emphasis> complex

Distribution of plants and the expression of traits associated with environmental variation can be affected by both average conditions and the variance in conditions including extreme climatic events. We expect that these same factors should affect the distribution of plants in hybrid zones between ecologically distinct species where the hybrids should occupy ecotones or intermediate habitats. We evaluated water availability and leaf morphological differences among parental and hybrid populations of herbaceous perennial plants in the Piriqueta caroliniana complex along environmental gradients in Southeastern North America. We focus on two taxa in this group; the viridis morphotype, which occurs in southern Florida, and the caroliniana morphotype, which is distributed from northern Florida to southern Georgia. Advanced-generation hybrid derivatives of these morphotypes occupy a broad geographic region that extends across much of central Florida. Overall, we found that hybrid populations occurred in significantly drier locations, indicating that their habitat requirements are transgressive (i.e., exceeding parental values) rather than intermediate to the parental morphotypes. Water availability differed between the two sampling years, and plants displayed morphological changes in response to these changes in moisture. During the drier year, leaves were narrower and more hirsute, corroborating experimental results that these leaf traits are plastic, and confirming that plasticity occurs in natural habitats. Hybrids exhibited intermediate leaf traits (shape and size) across both years, and displayed transgressive (hair density) leaf traits during the drier year. The apparent canalization of the hybrids’ leaf morphological traits may contribute to their tolerance of variable environmental conditions and may partially explain why they have displaced the caroliniana morphotype in central Florida.     

Evolution of pre‐zygotic and post‐zygotic barriers to gene flow among three cryptic species within the Anastrepha fraterculus complex

Tropical tephritids are ideally suited for studies on population divergence and speciation because they include species groups undergoing rapid radiation, in which morphologically cryptic species and sister species are abundant. The fraterculus species group in the Neotropical genus Anastrepha is a case in point, as it is composed of a complex of up to seven A. fraterculus morphotypes proposed to be cryptic species. Here, we document pre‐ and post‐zygotic barriers to gene flow among adults of the Mexican A. fraterculus morphotype and three populations (Argentina, Brazil, and Peru) belonging to two separate morphotypes (Brazilian 1 and Peruvian). We unveiled three forms of pre‐zygotic reproductive isolation resulting in strong assortative mating. In field cages, free‐ranging male and female A. fraterculus displayed a strong tendency to form couples with members of the opposite sex belonging to their own morphotype, suggesting that male pheromone emission, courtship displays, or both intervene in shaping female choice before actual contact and coupling. In addition, males and females of the Peruvian morphotype became receptive and mated significantly later than adults of the Mexican and Brazilian 1 morphotypes. After contact, Mexican females exhibited greater mating discrimination than males when facing adults of the opposite sex belonging to either the Peruvian or the Brazilian 1 morphotype as evidenced by vigorous resistance to penetration once they had been forcefully mounted by heterotypic males. Forced copulations resulted in production of F1 hybrids that were either less viable (and partially fertile) than parental crosses or even sterile. Our results suggest that the Mexican morphotype is a distinct biological entity and that pre‐zygotic reproductive isolation through divergence in courtship or male‐produced pheromone and other mechanisms appear to evolve faster than post‐zygotic isolation in the fraterculus species group.     

The morphological variation of the eggs and genital plates of two morphotypes of Triatoma protracta Uhler, 1894

The control of triatomine insects is necessary because these insects are the principal vectors of Trypanosoma cruzi, the agent of Chagas disease. Nevertheless, some of these vectors, such as Triatoma protracta, have not been studied adequately and their importance and taxonomic status has not yet been defined in detail and must be reevaluated in view of the continuing taxonomic uncertainties associated with the species. To help clarify the taxonomic status of T. protracta, the eggs and genital plates of two morphotypes were analyzed. Qualitative and quantitative morphological differences were observed in two morphotypes, designated T. p. protracta and T. p. nahuatlae according to Ryckman (1962). The morphotype T. p. protracta exhibited large and wide eggs with pores forming large padded polygonal structures, whereas the eggs of the morphotype T. p. nahuatlae were small and smooth. The size of the 9(th) genital urosternite was longer and wider in females in contrast to males in both morphotypes. However, these size differences were relatively greater in T. p. protracta. The high morphological variation found between the morphotypes of T. protracta suggests that they should be separated. Accordingly, it is probable that this group should be re-classified.     

A biometrical analysis of morphological variation within a section of genusEuplotes (ciliata,hypotrichida), with special reference to theE. vannus complex of sibling species

Some 50 clones belonging to a rather homogeneous, presumably monophyletic, section of genusEuplotes proved to be distributed between two clear-cut subgroups on the basis of cell size and relative peristome length. These subgroups are referred to asvannus andminuta morphotypes.Withinvannus morphotype, theE. vannus complex of 5 sibling species was previously defined on the basis of interfertility criterion. Electrophoretical studies revealed clear-cut biochemical differences between theE. vannus complex and theminuta morphotype.A multivariate analysis concerning 6 characters shows that the 5 species in the complex are closely similar. Nevertheless, the results of discriminant analysis suggest that a morphological discrimination could be possible.The status of one peculiar clone remains somewhat obscure. It belongs undoubtedly to thevannus morphotype, but shows no mating reaction with any of the 5 species ofE. vannus complex and is electrophoretically related tominuta morphotype.The following interpretation is suggested. In this section of genusEuplotes, two stable adaptive zones are available, corresponding to the two morphotypes. Speciation and change of adaptive zone are more or less independent evolutionary events. For example, the 5 species of thevannus complex have been generated by speciation without change of adaptive zone. Conversely, the exceptional clone may be phyletically related to theminuta morphotype through a rather recent jump from one adaptive zone to the other.     

Phylogenomic and morphological data reveal hidden patterns of diversity in the national tree of Brazil,Paubrasilia echinata

Premise

Paubrasilia echinata (common names, pau brasil, brazilwood) is the national tree of Brazil and an endangered species endemic to the Brazilian Atlantic Forest. Over its wide distribution of 2000 km, its leaflets morphology exhibits extensive plasticity. Three morphotypes are commonly identified based on leaf size, but it is unclear if they represent distinct taxa or a single polymorphic species. This study aims to clarify the taxonomic position of the three morphotypes to inform conservation decisions.

Methods

A morphometric study of leaf characters of herbarium specimens was coupled with genetic analyses using genotype-by-sequencing data. We used maximum-likelihood and coalescent methods to evaluate the phylogenetic and population structure of the species. We compared these with a morphological dendrogram built from hierarchical clustering.

Results

Two of the three morphotypes formed separately evolving lineages, the third morphotype formed two geographically separate lineages, and northern trees with intermediate leaf morphology formed a separate fifth lineage. Leaflet size varied by over 35-fold, and although morphological clustering generally matched the genetic patterns, there were some overlaps, highlighting the cryptic diversity within this group.

Conclusions

Our genetic and morphological results provide some evidence that cultivated trees from different states in Brazil seem to have a limited genetic origin and do not reflect the broader genetic and geographical diversity of the species. As a result, more care is likely needed to preserve the overall genomic diversity of this endangered and iconic species.     

Intraspecific taxonomic differentiation in ticks (Acari: Ixodidae) in the view of the morphological conception of species

The criterions for two most used intraspecific taxonomic ranks of ticks--subspecies and morphotype, have been formulated on the basis of the study of morphological variation in the distribution range of all active ontogenetic stages of 11 polymorphic species. All these species are vectors of transmissible diseases. They have vast distribution ranges and different types of host-parasite relationships. Subspecies have the complexes of visual morphological differences expressed in one or both sexes of mature ticks more limited, than those of related species. At immature stages differences of subspecies consist more often in morphometric characters and can be established by the methods of mathematical statistics only. Morphotypes, as a rule, differ at each corresponding stage by "their own" complexes of morphometric characters. All differential parameters of studied morphotypes are overlapped, but have statistically significant differences (by the Student's test). The concrete variations of differentiation by subspecies and morphotypes have been considered. The historical factors of intraspecific differentiation have been reconstructed for each species.     

Molecular,morphological, and ecological differences between the terrestrial and aquatic forms of Oxyrrhynchium speciosum (Brid.) Warnst. (Brachytheciaceae)

Oxyrrhynchium speciosum (Brid.) Warnst. is a relatively uncommon moss that can be found in wetland habitats across Europe and New Zealand. In this paper, we address the morphological, molecular and ecological relationships between the aquatic form of O. speciosum discovered in a deep, Chara-dominated lake (Budzis?awskie, NW Poland) and its terrestrial relatives. Morphological assessments revealed a considerable difference between terretrial and deep-water samples of O.speciosum. The aquatic form of O. speciosum was, on average, 12 times larger, with more branched stems (4–30 times) and longer leaves (1–2 times).

Investigation of ITS1-5·8S-ITS2-26S region sequences, however, revealed no distinction between the terrestrial and aquatic forms. An analysis of the ecological data suggests that the presence of O. speciosum in deep lake habitats is not incidental (as with many land species developing in aquatic environments). On the contrary, aquatic forms have a distinct ecological niche. Our results confirm that both forms of O. speciosum are closely related to O. hians (Hedw.) Loeske (a terrestrial species). The data indicate that O. speciosum is nested within a well-supported O. hians clade and separation of these species may be connected with polyploidization that occurred during their evolution.     

Morphological and physiological differences between two morphotypes of Zostera noltii Hornem. from the south-western Iberian Peninsula

The morphological and physiological differences between two morphotypes of Z. noltii Hornem. were studied in the intertidal meadows on the south-western Iberian Peninsula (Palmones river estuary and Ria Formosa). A small-leaved morphotype (SM) grows mainly at high intertidal sites, meadow edges or in recently deposited sandbanks, whereas a large-leaved morphotype (LM) generally thrives in well-structured beds or in deeper places. This study deals with the morphological, biochemical and physiological differences between these morphotypes as well as the ecological implications of the occurrence of different morphotypes in the same meadow. Shoot length, leaf width, rhizome internode length, roots per node, root length, leaf nutrient and pigment contents, and photosynthetic rates of both morphotypes were compared. The below-ground architecture (root and rhizome complex) of both morphotypes was more developed in sites characterized by higher hydrodynamics and/or a lower nitrogen content in sediments. Both morphotypes showed similar values for photosynthetic efficiency, dark respiration rate and compensation irradiance. On the other hand, the net photosynthetic capacity was much greater (5-fold) for the SM. This difference could explain the greater growth rate and faster leaf turnover rate of the SM compared with the LM. The occurrence of the SM in newly settled areas (and in the meadow edges) could be explained on the basis of its higher growth rate, which would allow a faster spreading of the meadow and/or better recovery after burial resulting from stormy weathers. Received: 20 December 1998 / Received in revised form: 21 April 1999 / Accepted: 23 April 1999